@article{jiang_araia_balyan_robinson_brown_caiola_hu_dou_neal_li_2024, title={Kinetic study of Ni-M/CNT catalyst in methane decomposition under microwave irradiation}, volume={340}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2023.123255}, abstractNote={Methane catalytic decomposition has been studied with catalysts that can attenuate the energy of electromagnetic waves to heat and drive the reaction. Herein, we report, for the first time, a comprehensive kinetic study of Ni-M (M=Pd, Cu, or Fe)-CNT catalysts under microwave irradiation. These binary metal alloy nanoparticles have been synthesized on multiwalled carbon nanotube support with solvothermal process. These catalysts showed incredible performance for both absorbing microwave energy and catalyzing the reaction to form carbon nanotubes and hydrogen. Ni-M-CNT has a reaction order of 0.74. 10Ni-1 Pd-CNT, 10Ni-1Cu-CNT, and 10Ni-1Fe-CNT have activation energies at 87, 75, and 69 kJ/mol. The investigation was carried out in a differential reactor. The results indicated that 10Ni-1Fe-CNT had the lowest activation energy due to the increase in microwave susceptibility. This work pioneered the microwave catalytic methane decomposition field as well as paving the way for future electrification of COx-free hydrogen production.}, journal={APPLIED CATALYSIS B-ENVIRONMENT AND ENERGY}, author={Jiang, Changle and Araia, Alazar and Balyan, Sonit and Robinson, Brandon and Brown, Siobhan and Caiola, Ashley and Hu, Jianli and Dou, Jian and Neal, Luke M. and Li, Fanxing}, year={2024}, month={Jan} }
 @article{cai_krzystowczyk_braunberger_li_neal_2024, title={Techno-economic analysis of chemical looping air separation using a perovskite oxide sorbent}, volume={132}, ISSN={["1878-0148"]}, DOI={10.1016/j.ijggc.2024.104070}, abstractNote={Air separation is a costly process that is difficult to operate efficiently at small scales. Chemical looping air separation (CLAS) is a promising process for small-footprint oxygen production with low energy consumption. CLAS has potential applications in a promising carbon capture technology, oxyfuel combustion (oxy-combustion). In oxy-combustion, high-concentration oxygen from an air separation unit is used to combust a carbonaceous fuel into an easily-separated, nitrogen-free exhaust stream. In this paper, a techno-economic analysis was conducted in conjunction with reactor modeling to determine the cost of oxygen from a CLAS plant as a modular air separation unit for a 5 MW thermal coal-based oxy-combustion plant. The effects of different length-to-diameter ratios were investigated. The cost of oxygen from CLAS was projected to be as low as $65/ton O2 under baseline assumptions, which was much lower than typical current delivered oxygen at similar scales. Although higher in capital cost, CLAS also compares favorably to pressure swing adsorption, which has much larger parasitic energy losses. Further analysis indicates that air and steam demand and the sorbent reactor L/D ratio are key to optimizing the costs.}, journal={INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL}, author={Cai, Runxia and Krzystowczyk, Emily and Braunberger, Beau and Li, Fanxing and Neal, Luke}, year={2024}, month={Feb} }
 @article{haribal_iftikhar_tong_rayer_sanderson_li_neal_2024, title={Technoeconomic and Emissions Analysis of the Hybrid Redox Process for the Production of Acetic Acid with CO<sub>2</sub> Utilization}, volume={3}, ISSN={["2366-7486"]}, DOI={10.1002/adsu.202300453}, abstractNote={Abstract The production of oxygenated hydrocarbons, such as acetic acid, using captured CO 2 is a promising pathway to reduce greenhouse gas emissions in the chemical industry. The use of a chemical looping‐based hybrid redox process (HRP) is proposed to convert CO 2 and natural gas into separate CO and syngas streams that can be used to produce various commodity oxygenates, while allowing the beneficial utilization of captured CO 2 . Here, a detailed technoeconomic analysis of HRP applied to the production of acetic acid is presented. Emissions and energy analyses show the ability of HRP to lower the CO 2 emissions for acetic acid synthesis by 74% compared to a conventional steam and autothermal reforming route. HRP also offers a potential 34% reduction in capital costs. Compared to a dry reforming based acetic acid production route, HRP has the potential for significantly lower costs. If integrated with a low carbon energy source, HRP has the potential to achieve a negative emission of greenhouse gas (‐0.50 kg CO 2 per kg acetic acid).}, journal={ADVANCED SUSTAINABLE SYSTEMS}, author={Haribal, Vasudev and Iftikhar, Sherafghan and Tong, Andrew and Rayer, Aravind and Sanderson, Corry and Li, Fanxing and Neal, Luke}, year={2024}, month={Mar} }
 @article{cai_brody_tian_neal_bose_li_2023, title={Numerical modeling of chemical looping oxidative dehydrogenation of ethane in parallel packed beds}, volume={469}, ISSN={["1873-3212"]}, url={https://doi.org/10.1016/j.cej.2023.143930}, DOI={10.1016/j.cej.2023.143930}, abstractNote={Chemical looping oxidative dehydrogenation (CL-ODH) of ethane has the potential to be a highly efficient alternative to steam cracking for ethylene production. Accurate reactor modeling is of critical importance to efficiently scale up and optimize this new technology. This study reports a one-dimensional, heterogeneous packed bed model to simulate the CL-ODH of ethane to ethylene with a Na2MoO4-promoted CaTi0.1Mn0.9O3 redox catalyst. The overall reaction kinetics was well-described by coupling the gas-phase steam cracking of ethane with the reduction kinetics of the redox catalyst by H2 and C2H4. The impact of H2 on the formation rate of CO2 byproduct from C2H4 conversion was also thoroughly investigated to validate the applicability of the kinetic model under operational environments. The temperature variation within the different CL-ODH steps and the temperature distribution along the bed were also carefully considered. The accuracy of the model was validated by experiments conducted in a large lab-scale packed bed reactor (200 g catalyst loading), with an average deviation of 2.8% in terms of ethane conversion and ethylene yield. The model was subsequently used to optimize the operating parameters of the CL-ODH reactor, indicating that up to 63.7% single-pass C2 + olefin yield can be achieved with the current redox catalyst bed whereas further optimization of the redox catalyst to inhibit C2H4 activation can result in 69.4% single-pass C2 + yield while maintaining low CO2 selectivity.}, journal={CHEMICAL ENGINEERING JOURNAL}, author={Cai, Runxia and Brody, Leo and Tian, Yuan and Neal, Luke and Bose, Arnab and Li, Fanxing}, year={2023}, month={Aug} }
 @article{brody_neal_liu_li_2022, title={Autothermal Chemical Looping Oxidative Dehydrogenation of Ethane: Redox Catalyst Performance, Longevity, and Process Analysis}, volume={7}, ISSN={["1520-5029"]}, DOI={10.1021/acs.energyfuels.2c01293}, abstractNote={Energy-efficient upgrading of stranded ethane from shale gas to olefins holds the promise of increasing the supply of useful chemical feedstocks while reducing flaring-based CO2 emissions. Previously, we reported a modular ethane-to-liquids (M-ETL) system based on a chemical looping oxidative dehydrogenation (CL-ODH) scheme. In this article, we present long-term (>1200 h) results of Li2CO3-promoted La0.8Sr0.2FeO3 corresponding to ∼4125 CL-ODH cycles in a large laboratory-scale packed bed reactor. Temperature monitoring along the bed length confirmed the exothermicity of both the oxidative dehydrogenation and regeneration steps, enabling an autothermal operation. Product gas analysis indicated that the redox catalyst maintains a high C2+ selectivity (∼90%) and ethane conversion (∼67%) at 735 °C after continuous cycling of >1000 h. Product distributions and heats of reactions were used to update our M-ETL process model for revised techno-economic analysis, demonstrating that the current system is economically viable with relatively low required selling prices across a wide range of operating scenarios.}, journal={ENERGY & FUELS}, author={Brody, Leo and Neal, Luke and Liu, Junchen and Li, Fanxing}, year={2022}, month={Jul} }
 @article{jiang_wang_bai_balyan_robinson_hu_li_deibel_liu_li_et al._2022, title={Methane Catalytic Pyrolysis by Microwave and Thermal Heatingover Carbon Nanotube-Supported Catalysts: Productivity, Kinetics,and Energy Efficiency br}, volume={61}, ISSN={["0888-5885"]}, DOI={10.1021/acs.iecr.1c05082}, abstractNote={Methane catalytic pyrolysis, which is the reaction to produce hydrogen and carbon without emitting CO2, represents an approach for decarbonization using natural gas as an energy resource. The endothermic pyrolysis reaction was carried out under two heating scenarios: convective thermal heating and microwave-driven irradiative heating. The pyrolysis reaction was conducted at 550–600 °C over carbon nanotube (CNT)-supported Ni–Pd and Ni–Cu catalysts. On both catalysts, an enhanced methane conversion rate was observed under microwave irradiation. The enhanced catalytic activity was hypothetically caused by the presence of free electrons in the carbon atoms within the CNT that enabled the CNT support to absorb microwave energy effectively and to be heated efficiently by microwave. The microwave catalytic pyrolysis has shown improvement in kinetics, where the apparent activation energy dropped from 45.5 kJ/mol under conventional convective heating to 24.8 kJ/mol under microwave irradiation. When the methane conversion rate is increased by 37%, the microwave power consumption only changed by 10.8%. The research demonstrated the potential of transforming natural gas into clean hydrogen and value-added carbon in a more energy-efficient way. Process simulation and techno-economic analysis showed that potentially hydrogen minimum selling price of about $1/kg H2 could be achieved.}, number={15}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Jiang, Changle and Wang, I-Wen and Bai, Xinwei and Balyan, Sonit and Robinson, Brandon and Hu, Jianli and Li, Wenyuan and Deibel, Angela and Liu, Xingbo and Li, Fanxing and et al.}, year={2022}, month={Apr}, pages={5080–5092} }
 @article{liu_yusuf_jackson_martin_chacko_vogt-lowell_neal_li_2022, title={Redox oxide@molten salt as a generalized catalyst design strategy for oxidative dehydrogenation of ethane via selective hydrogen combustion}, volume={646}, ISSN={["1873-3875"]}, DOI={10.1016/j.apcata.2022.118869}, abstractNote={The current study demonstrates a redox oxide @ molten salt core-shell architecture as a generalized redox catalyst design strategy for chemical looping – oxidative dehydrogenation of ethane. 17 combinations of redox active oxides and molten salts were prepared, evaluated, and characterized. X-ray diffraction indicates that the redox oxides and molten salts are fully compatible, forming separate and stable phases. X-ray photoelectron spectroscopy demonstrates that the molten salts aggregate at the redox oxide surface, forming a core-shell structure to block the non-selective sites responsible for COx formation. Up to ∼74 % single-pass olefin yields were achieved using the proposed redox catalyst design strategy. Statistical analyses of the performance data indicate the potential to achieve up to 86.7 % single-pass yield by simply optimizing the operating conditions using the redox catalysts reported in this study. Meanwhile, the generalizability of the catalyst design strategy offers exciting opportunities to further optimize the composition and performance of the redox catalysts for ethane ODH under a chemical looping scheme with significantly reduced energy consumption and CO2 emissions.}, journal={APPLIED CATALYSIS A-GENERAL}, author={Liu, Junchen and Yusuf, Seif and Jackson, Daniel and Martin, William and Chacko, Dennis and Vogt-Lowell, Kyle and Neal, Luke and Li, Fanxing}, year={2022}, month={Sep} }
 @article{zhu_gao_wang_haribal_liu_neal_bao_wu_wang_li_2021, title={A tailored multi-functional catalyst for ultra-efficient styrene production under a cyclic redox scheme}, volume={12}, ISSN={["2041-1723"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85101732148&partnerID=MN8TOARS}, DOI={10.1038/s41467-021-21374-2}, abstractNote={Styrene is an important commodity chemical that is highly energy and CO2 intensive to produce. We report a redox oxidative dehydrogenation (redox-ODH) strategy to efficiently produce styrene. Facilitated by a multifunctional (Ca/Mn)1-xO@KFeO2 core-shell redox catalyst which acts as (i) a heterogeneous catalyst, (ii) an oxygen separation agent, and (iii) a selective hydrogen combustion material, redox-ODH auto-thermally converts ethylbenzene to styrene with up to 97% single-pass conversion and >94% selectivity. This represents a 72% yield increase compared to commercial dehydrogenation on a relative basis, leading to 82% energy savings and 79% CO2 emission reduction. The redox catalyst is composed of a catalytically active KFeO2 shell and a (Ca/Mn)1-xO core for reversible lattice oxygen storage and donation. The lattice oxygen donation from (Ca/Mn)1-xO sacrificially stabilizes Fe3+ in the shell to maintain high catalytic activity and coke resistance. From a practical standpoint, the redox catalyst exhibits excellent long-term performance under industrially compatible conditions.}, number={1}, journal={NATURE COMMUNICATIONS}, publisher={Springer Science and Business Media LLC}, author={Zhu, Xing and Gao, Yunfei and Wang, Xijun and Haribal, Vasudev and Liu, Junchen and Neal, Luke M. and Bao, Zhenghong and Wu, Zili and Wang, Hua and Li, Fanxing}, year={2021}, month={Feb} }
 @article{brody_neal_haribal_li_2021, title={Ethane to liquids via a chemical looping approach - Redox catalyst demonstration and process analysis}, volume={417}, ISSN={["1873-3212"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85102136078&partnerID=MN8TOARS}, DOI={10.1016/j.cej.2021.128886}, abstractNote={The inability to economically transport ethane from distributed shale gas production sites results in the “rejection”, i.e. flaring or reinjection, of this important petrochemical feedstock. Therefore, a technology capable of efficiently converting geographically isolated ethane into transportable liquid fuels would effectively exploit this abundant yet wasted resource. We proposed a modular ethane-to-liquids (M−ETL) system that employs a chemical looping-oxidative dehydrogenation (CL-ODH) scheme to convert ethane into olefins via cyclic redox reactions. The olefins would subsequently undergo oligomerization to form mid-distillate liquid fuels. In this study, a sodium molybdate promoted CaTi0.1Mn0.9O3 core-shell redox catalyst (CaTi0.1Mn0.9O3@Na2MoO4) is presented as a potentially viable, redox-active catalyst for the CL-ODH of ethane to ethylene. Performance data were collected from 1,600 + hours (>4,000CL-ODH cycles) of packed bed operations at varying temperatures and space velocities. 52 – 58% single-pass olefin yields at 725 and 730 °C were obtained with relatively low (2.5 – 8%) COx selectivity. The experimental data were used as inputs to an ASPEN Plus® based M−ETL system model to evaluate its performance. Sensitivity analyses were performed on the CL-ODH and oligomerization sections of the M−ETL system, and the results were used to inform economic analysis of the process. The techno-economic analysis (TEA) indicates that the introduction of recycle to the system provides flexibility for profit generation for both high (Xethane = 0.75) and low (Xethane = 0.58) conversion cases. Additionally, TEA results demonstrate that electrical cogeneration can be economically attractive under certain scenarios.}, journal={CHEMICAL ENGINEERING JOURNAL}, author={Brody, Leo and Neal, Luke and Haribal, Vasudev and Li, Fanxing}, year={2021}, month={Aug} }
 @article{iftikhar_jiang_gao_liu_gu_neal_li_2021, title={LaNixFe1-xO3-delta as a Robust Redox Catalyst for CO2 Splitting and Methane Partial Oxidation}, volume={35}, ISSN={["1520-5029"]}, DOI={10.1021/acs.energyfuels.1c02258}, abstractNote={The current study reports LaNi0.5Fe0.5O3−δ as a robust redox catalyst for CO2 splitting and methane partial oxidation at relatively low temperatures (∼700 °C) in the context of a hybrid redox process. Specifically, perovskite-structured LaNixFe1–xO3−δ (LNFs) with nine different compositions (x = 0.05–0.5) were prepared and investigated. Among the samples evaluated, LaNi0.4Fe0.6O3−δ and LaNi0.5Fe0.5O3−δ showed superior redox performance, with ∼90% CO2 and methane conversions and >90% syngas selectivity. The standalone LNFs also demonstrated performance comparable to that of LNF promoted by mixed conductive Ce0.85Gd0.1Cu0.05O2−δ (CGCO). Long-term testing of LaNi0.5Fe0.5O3−δ indicated that the redox catalyst gradually loses its activity over repeated redox cycles, amounting to approximately 0.02% activity loss each cycle, averaged over 500 cycles. This gradual deactivation was found to be reversible by deep oxidation with air. Further characterizations indicated that the loss of activity resulted from a slow accumulation of iron carbide (Fe3C and Fe5C2) phases, which cannot be effectively removed during the CO2 splitting step. Reoxidation with air removed the carbide phases, increased the availability of Fe for the redox reactions via solid-state reactions with La2O3, and decreased the average crystallite size of La2O3. Reactivating the redox catalyst periodically, e.g., once every 40 cycles, was shown to be highly effective, as confirmed by operating the redox catalyst over 900 cumulative cycles while maintaining satisfactory redox performance.}, number={17}, journal={ENERGY & FUELS}, author={Iftikhar, Sherafghan and Jiang, Qiongqiong and Gao, Yunfei and Liu, Junchen and Gu, Haiming and Neal, Luke and Li, Fanxing}, year={2021}, month={Sep}, pages={13921–13929} }
 @article{hao_gao_liu_dudek_neal_wang_liu_li_2021, title={Zeolite-assisted core-shell redox catalysts for efficient light olefin production via cyclohexane redox oxidative cracking}, volume={409}, ISSN={["1873-3212"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85098692807&partnerID=MN8TOARS}, DOI={10.1016/j.cej.2020.128192}, abstractNote={This study reports a highly effective redox catalyst platform, i.e. composites of metal-exchanged ZSM5 and CaMn0.75Fe0.25O3@Na2WO4, for “low temperature” (<650 °C) redox oxidative cracking (ROC) of naphtha using a cyclohexane model compound. TEM-EDX showed that Na2WO4 shell covers the CaMn0.75Fe0.25O3 bulk and the zeolite + CaMn0.75Fe0.25O3@Na2WO4 composite can achieve autothermal conversion of cyclohexane under a cyclic redox scheme by selective oxidation of by-product H2 to H2O. Meanwhile, NH3-TPD and pyridine FTIR experiments confirmed that the Brönsted acidity of ZSM5 was primarily responsible for cyclohexane activation. Compared to each catalyst component alone, the synergistic effect of the composite redox catalysts resulted in substantially higher olefin yield (up to 75%), lower alkane yield (~5%), lower aromatic yield (~10%), and higher lattice oxygen utilization (up to 4 wt.cat%). Based on TGA-DSC experiments and ASPEN Plus analysis, the multi-functional redox catalysts facilitate autothermal conversion of cyclohexane with high lattice oxygen utilization from the redox catalysts. Due to the highly effective redox catalysts performance and the ease for heat integration, the novel ROC process has the potential for more energy-efficient light olefins production with significantly reduced CO2 emissions when compared to naphtha steam cracking.}, journal={CHEMICAL ENGINEERING JOURNAL}, author={Hao, Fang and Gao, Yunfei and Liu, Junchen and Dudek, Ryan and Neal, Luke and Wang, Shuang and Liu, Pingle and Li, Fanxing}, year={2021}, month={Apr} }
 @article{hao_gao_neal_dudek_li_chung_guan_liu_liu_li_2020, title={Sodium tungstate-promoted CaMnO3 as an effective, phase-transition redox catalyst for redox oxidative cracking of cyclohexane}, volume={385}, ISSN={["1090-2694"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85082646635&partnerID=MN8TOARS}, DOI={10.1016/j.jcat.2020.03.022}, abstractNote={Oxidative cracking, which combines catalytic oxidation and cracking reactions, represents a promising approach to reduce the energy and carbon intensities for light olefin production from naphtha. The need to co-feed gaseous oxygen with hydrocarbons, however, leads to significant COx formation and safety concerns. The cost and energy consumption associated with air separation also affects its economic attractiveness. In this study, we investigated a redox oxidative cracking (ROC) scheme and evaluated perovskites (La0.8Sr0.2FeO3 and CaMnO3) and Na2WO4-promoted perovskite (La0.8Sr0.2FeO3@Na2WO4 and CaMnO3@Na2WO4) as the redox catalysts for ROC. CaMnO3@Na2WO4 redox catalyst shows high activity, selectivity, and stability for light olefin production from cyclohexane. Operated under a redox oxidative cracking (ROC) scheme, CaMnO3@Na2WO4 enhances the catalytic cracking of cyclohexane, while showing high selectivity towards hydrogen combustion with its built-in, active lattice oxygen. Over three-fold increase in olefin yield compared to thermal cracking and 35% yield increase compared to conventional O2-cofeed oxidative cracking were achieved. Low energy ion scattering (LEIS), X-ray photoelectric spectroscopy (XPS), and differential scanning calorimetry (DSC) indicated a core-shell structure, where a molten Na2WO4 layer covers the CaMnO3 core. Na2WO4 modifies the oxygen donation behavior of CaMnO3 and provides a catalytically active surface for cyclohexane activation. In-situ XRD revealed that CaMnO3@Na2WO4 exhibited excellent structural stability and regenerability. The transformation of Mn4+ ↔ Mn3+ ↔ Mn2+ in CaMnO3, facilitated by reversible phase transition to (Ca/Mn)O solid solution, is responsible for the lattice oxygen donation and uptake during redox cycles. Electrochemical impedance spectroscopy (EIS) measurements further confirmed that the oxygen species were transported through the molten Na2WO4 layer to participate in ROC. These findings offer mechanistic insights to design effective redox catalysts for hydrocarbon valorization using the chemical looping strategy.}, journal={JOURNAL OF CATALYSIS}, author={Hao, Fang and Gao, Yunfei and Neal, Luke and Dudek, Ryan B. and Li, Wenyuan and Chung, Chingchang and Guan, Bo and Liu, Pingle and Liu, Xingbo and Li, Fanxing}, year={2020}, month={May}, pages={213–223} }
 @article{yusuf_neal_bao_wu_li_2019, title={Effects of Sodium and Tungsten Promoters on Mg6MnO8-Based Core-Shell Redox Catalysts for Chemical Looping-Oxidative Dehydrogenation of Ethane}, volume={9}, ISSN={["2155-5435"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85064004480&partnerID=MN8TOARS}, DOI={10.1021/acscatal.9b00164}, abstractNote={The present study investigates the effect of sodium and tungsten promoters on Mg6MnO8-based redox catalysts in a chemical looping oxidative dehydrogenation (CL-ODH) scheme. CL-ODH has the potential...}, number={4}, journal={ACS CATALYSIS}, author={Yusuf, Seif and Neal, Luke and Bao, Zhenghong and Wu, Zili and Li, Fanxing}, year={2019}, month={Apr}, pages={3174–3186} }
 @article{neal_haribal_li_2019, title={Intensified Ethylene Production via Chemical Looping through an Exergetically Efficient Redox Scheme}, volume={19}, ISSN={["2589-0042"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85071973963&partnerID=MN8TOARS}, DOI={10.1016/j.isci.2019.08.039}, abstractNote={Ethylene production via steam cracking of ethane and naphtha is one of the most energy and emission-intensive processes in the chemical industry. High operating temperatures, significant reaction endothermicity, and complex separations create hefty energy demands and result in substantial CO2 and NOx emissions. Meanwhile, decades of optimization have led to a thermally efficient, near-"perfect" process with ∼95% first law energy efficiency, leaving little room for further reduction in energy consumption and CO2 emissions. In this study, we demonstrate a transformational chemical looping-oxidative dehydrogenation (CL-ODH) process that offers 60%-87% emission reduction through exergy optimization. Through detailed exergy analyses, we show that CL-ODH leads to exergy savings of up to 58% in the upstream reactors and 26% in downstream separations. The feasibility of CL-ODH is supported by a robust redox catalyst that demonstrates stable activity and selectivity for over 1,400 redox cycles in a laboratory-scale fluidized bed reactor.}, journal={ISCIENCE}, publisher={Elsevier BV}, author={Neal, Luke M. and Haribal, Vasudev Pralhad and Li, Fanxing}, year={2019}, month={Sep}, pages={894-+} }
 @article{yusuf_haribal_jackson_neal_li_2019, title={Mixed iron-manganese oxides as redox catalysts for chemical looping-oxidative dehydrogenation of ethane with tailorable heat of reactions}, volume={257}, ISSN={["1873-3883"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85067840834&partnerID=MN8TOARS}, DOI={10.1016/j.apcatb.2019.117885}, abstractNote={The chemical looping-oxidative dehydrogenation (CL-ODH) of ethane is investigated in this study. In CL-ODH, a redox catalyst donates its lattice oxygen to combust hydrogen formed from ethane dehydrogenation (ODH reactor). The reduced redox catalyst is then transferred to a separate reactor (regenerator), where it is re-oxidized with air. Typically, the ODH step is endothermic, due to the high endothermicity to reduce the redox catalyst. This energy demand is met through sensible heat carried by the redox catalyst from the regenerator, which operates at a higher temperature. This temperature difference between the two reactors leads to exergy losses. We report an Fe-Mn redox catalyst showing tunable exothermic heat of reduction. Promotion with Na2WO4 resulted in high ethylene yields due to the suppression of surface Fe/Mn. ASPEN Plus® simulations indicated that Fe-Mn redox catalysts can lower the temperature difference between the two reactors. This can lead to efficiency improvements for CL-ODH.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, publisher={Elsevier BV}, author={Yusuf, Seif and Haribal, Vasudev and Jackson, Daniel and Neal, Luke and Li, Fanxing}, year={2019}, month={Nov} }
 @article{neal_haribal_mccaig_lamb_li_2019, title={Modular‐scale ethane to liquids via chemical looping oxidative dehydrogenation: Redox catalyst performance and process analysis}, volume={1}, ISSN={2637-403X 2637-403X}, url={http://dx.doi.org/10.1002/AMP2.10015}, DOI={10.1002/AMP2.10015}, abstractNote={Abstract The difficulties in the liquefaction and transportation of ethane in shale gas has led to significant rejection, via reinjection or flaring, of this valuable hydrocarbon resource. Upgrading this low‐value, isolated ethane into easily transportable liquid fuels is a promising solution to this supply glut. In this study, we present a modular system that can potentially be operated economically at geographically isolated gas‐processing facilities. The modular ethane‐to‐liquids (M‐ETL) system uses a chemical looping‐oxidative dehydrogenation (CL‐ODH) technology to efficiently convert ethane and natural gas liquids into olefins (primarily ethylene) via cyclic redox reactions of highly effective redox catalyst particles. The resulting olefins are then converted to gasoline and mid‐distillate products via oligomerization. CL‐ODH eliminates air separation and equilibrium limitations for olefin generation. It also simplifies the process scheme and reduces energy consumption. Here, we present experimental proof‐of‐concept data on CL‐ODH conversion of ethane to ethylene. Using the CL‐ODH performance data at 750°C, we show that a simple, single‐pass configuration can be economically viable at distributed sites. We identify that economic factors such as the capital cost, price of ethane feed, and value of electricity byproduct have strong effects on the required selling price of the liquids. It is also noted that the economic viability of the M‐ETL system is relatively insensitive to the liquid yield under a low ethane price scenario. The demand and value of electricity at distributed locations, on the other hand, can play an important role in the optimal process configuration and economics.}, number={1-2}, journal={Journal of Advanced Manufacturing and Processing}, publisher={Wiley}, author={Neal, Luke and Haribal, Vasudev and McCaig, Joseph and Lamb, H. Henry and Li, Fanxing}, year={2019}, month={Apr}, pages={e10015} }
 @article{dudek_tian_blivin_neal_zhao_li_2019, title={Perovskite oxides for redox oxidative cracking of n-hexane under a cyclic redox scheme}, volume={246}, ISSN={["1873-3883"]}, url={https://doi.org/10.1016/j.apcatb.2019.01.048}, DOI={10.1016/j.apcatb.2019.01.048}, abstractNote={Steam cracking of naphtha is a commercially proven technology for light olefin production and the primary source of ethylene in the Europe and Asia-Pacific markets. However, its significant energy consumption and high CO2 intensity (up to 2 tons CO2/ton C2H4), stemming from endothermic cracking reactions and complex product separations, make this state-of-the-art process increasingly undesirable from an environmental standpoint. We propose a redox oxidative cracking (ROC) approach as an alternative pathway for naphtha conversion. Enabled by perovskite oxide-based redox catalysts, the ROC process converts naphtha (represented by n-hexane) in an auto-thermal, cyclic redox mode. The addition of 20 wt.% Na2WO4 to SrMnO3 and CaMnO3 created highly selective redox catalysts capable of achieving enhanced olefin yields from n-hexane oxy-cracking. This was largely attributed to the redox catalysts’ high activity, selectivity, and stability towards selective hydrogen combustion (SHC) under a redox mode. Na2WO4/CaMnO3 demonstrated significantly higher olefin yield (55–58%) when compared to that from thermal cracking (34%) at 725 °C and 4500 h−1. COx yield as low as 1.7% was achieved along with complete combustion of H2 over 25 cycles. Similarly, Na2WO4/SrMnO3 achieved 41% olefin yield, 0.4% COx yield, and 73% H2 combustion at this condition. Oxygen-temperature-programmed desorption (O2-TPD) indicated that Na2WO4 hindered gaseous oxygen release from CaMnO3. Low-energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) revealed an outermost perovskite surface layer covered by Na2WO4, which suppressed near-surface Mn and alkaline earth metal cations. The formation of non-selective surface oxygen species was also inhibited. XPS analysis further confirmed that promotion of SrMnO3 with Na2WO4 suppressed surface Sr species by 90%, with a similar effect also observed on CaMnO3. These findings point to the promoting effect of Na2WO4 and the potential of promoted SrMnO3 and CaMnO3 as selective redox catalysts for efficient production of light olefins from naphtha via the ROC process.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, publisher={Elsevier BV}, author={Dudek, Ryan B. and Tian, Xin and Blivin, Millicent and Neal, Luke M. and Zhao, Haibo and Li, Fanxing}, year={2019}, month={Jun}, pages={30–40} }
 @misc{gao_neal_ding_wu_baroi_gaffney_li_2019, title={Recent Advances in Intensified Ethylene Production-A Review}, volume={9}, ISSN={["2155-5435"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85071911366&partnerID=MN8TOARS}, DOI={10.1021/acscatal.9b02922}, abstractNote={Steam cracking is a well-established commercial technology for ethylene production. Despite decades of optimization efforts, the process is, nevertheless, highly energy and carbon intensive. This r...}, number={9}, journal={ACS CATALYSIS}, author={Gao, Yunfei and Neal, Luke and Ding, Dong and Wu, Wei and Baroi, Chinmoy and Gaffney, Anne M. and Li, Fanxing}, year={2019}, month={Sep}, pages={8592–8621} }
 @article{haribal_chen_neal_li_2018, title={Intensification of Ethylene Production from Naphtha via a Redox Oxy-Cracking Scheme: Process Simulations and Analysis}, volume={4}, ISSN={["2096-0026"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85053184335&partnerID=MN8TOARS}, DOI={10.1016/j.eng.2018.08.001}, abstractNote={Ethylene production by the thermal cracking of naphtha is an energy-intensive process (up to 40 GJ heat per tonne ethylene), leading to significant formation of coke and nitrogen oxide (NOx), along with 1.8–2 kg of carbon dioxide (CO2) emission per kilogram of ethylene produced. We propose an alternative process for the redox oxy-cracking (ROC) of naphtha. In this two-step process, hydrogen (H2) from naphtha cracking is selectively combusted by a redox catalyst with its lattice oxygen first. The redox catalyst is subsequently re-oxidized by air and releases heat, which is used to satisfy the heat requirement for the cracking reactions. This intensified process reduces parasitic energy consumption and CO2 and NOx emissions. Moreover, the formation of ethylene and propylene can be enhanced due to the selective combustion of H2. In this study, the ROC process is simulated with ASPEN Plus® based on experimental data from recently developed redox catalysts. Compared with traditional naphtha cracking, the ROC process can provide up to 52% reduction in energy consumption and CO2 emissions. The upstream section of the process consumes approximately 67% less energy while producing 28% more ethylene and propylene for every kilogram of naphtha feedstock.}, number={5}, journal={ENGINEERING}, author={Haribal, Vasudev Pralhad and Chen, Yun and Neal, Luke and Li, Fanxing}, year={2018}, month={Oct}, pages={714–721} }
 @article{yusuf_neal_haribal_baldwin_lamb_li_2018, title={Manganese silicate based redox catalysts for greener ethylene production via chemical looping - oxidative dehydrogenation of ethane}, volume={232}, ISSN={["1873-3883"]}, url={http://dx.doi.org/10.1016/j.apcatb.2018.03.037}, DOI={10.1016/j.apcatb.2018.03.037}, abstractNote={The current study investigates manganese silicate based redox catalysts for ethane to ethylene conversion in a chemical looping oxidative dehydrogenation (CL-ODH) process. Facilitated by a two-step cyclic redox scheme, CL-ODH has the potential to overcome the drawbacks of traditional steam cracking including high energy consumption, coke formation, and significant CO2 and NOx emissions. In CL-ODH, lattice oxygen in manganese silicate based redox catalysts is used to combust the hydrogen formed from ethane dehydrogenation, enhancing ethylene formation and suppressing coke formation. The oxygen-deprived redox catalyst is subsequently regenerated with air, releasing heat to balance the overall heat requirement. The key to this process is an efficient redox catalyst with high selectivity and facile oxygen transport. In this study, redox catalysts with combined manganese and silica phases were tested. We report that redox catalysts with high manganese content are more effective for CL-ODH due to their higher oxygen capacity at reaction temperatures. Sodium tungstate was used as a promoter due to its effectiveness to suppress COx formation. Among the redox catalysts investigated, sodium tungstate promoted (1.7 wt.% Na) manganese silicate (Mn:Si molar ratio = 70:30) was the most effective, showing an ethylene selectivity of 82.6% and yield of 63.3%. Temperature programmed reaction (TPR) experiments indicate that the sodium tungstate promoter inhibits ethane activation on the surface of the redox catalyst and is selective towards hydrogen combustion. XPS analysis indicates that the manganese silicate redox catalysts have a smaller amount of near surface Mn4+ than previously studied manganese containing redox catalysts, leading to higher ethylene selectivity on the un-promoted redox catalysts. XPS also indicates that the reduction of the un-promoted redox catalysts leads to the consumption of silica and formation of inosilicate species. ASPEN Plus® simulations of the CL-ODH scheme using manganese silicate based redox catalysts indicate significant energy and emissions savings compared to traditional steam cracking: the overall energy consumption for ethylene production can potentially be reduced by 89% using the manganese silicate based redox catalyst in the CL-ODH process. Resulting from the significant energy savings, CO2/NOx emissions can be reduced by nearly one order of magnitude when compared to traditional steam cracking.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Yusuf, Seif and Neal, Luke and Haribal, Vasudev and Baldwin, Madison and Lamb, H. Henry and Li, Fanxing}, year={2018}, month={Sep}, pages={77–85} }
 @article{zhu_li_neal_li_2018, title={Perovskites as Geo-inspired Oxygen Storage Materials for Chemical Looping and Three-Way Catalysis: A Perspective}, volume={8}, ISSN={["2155-5435"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85050819577&partnerID=MN8TOARS}, DOI={10.1021/acscatal.8b01973}, abstractNote={With highly tunable composition, structure, and chemical-physical properties, perovskite oxides represent a large family of mixed-oxide materials that finds many energy- and environment-related applications. This perspective discusses the fundamentals and applications of perovskite oxides in the context of chemical looping and three-way catalysis (TWC). Both applications make use of perovskite oxides’ oxygen storage and donation properties (>400 μmol O/g) under macroscopic reduction–oxidation (redox) cycles and at elevated temperatures. While perovskite oxides have been investigated as oxygen storage materials (OSMs) and three-way catalysts for more than five decades, use of these oxides in chemical looping, as oxygen carriers or redox catalysts, is a relatively new topic. This article provides an account of the effects of compositional, structural, and surface properties of perovskites on their oxygen storage and donation properties as well as their interactions with various gaseous reactants. Design and...}, number={9}, journal={ACS CATALYSIS}, author={Zhu, Xing and Li, Kongzhai and Neal, Luke and Li, Fanxing}, year={2018}, month={Sep}, pages={8213–8236} }
 @article{yusuf_neal_li_2017, title={Effect of Promoters on Manganese-Containing Mixed Metal Oxides for Oxidative Dehydrogenation of Ethane via a Cyclic Redox Scheme}, volume={7}, ISSN={["2155-5435"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85027258022&partnerID=MN8TOARS}, DOI={10.1021/acscatal.7b02004}, abstractNote={Ethylene is an important building block in the chemical industry; state of the art ethylene production (steam cracking) has multiple drawbacks, including high energy consumption, coke formation, and significant CO2 and NOx emissions. We propose a chemical looping oxidative dehydrogenation (CL-ODH) process to convert ethane into ethylene in a two-step, cyclic redox scheme. In this process, lattice oxygen in a metal oxide based redox catalyst is used to combust the hydrogen formed in ethane dehydrogenation, thereby enhancing ethylene formation while retarding coke formation. The oxygen-deprived redox catalyst is subsequently regenerated with air, releasing heat to balance the overall heat requirement. CL-ODH can realize a reduction of over 80% in primary energy consumption and pollutant emissions. The key to this process is an efficient redox catalyst with high selectivity and facile oxygen transport. Previously we determined that oxides with an Mg6MnO8 structure allow high lattice oxygen mobility and satis...}, number={8}, journal={ACS CATALYSIS}, author={Yusuf, Seif and Neal, Luke M. and Li, Fanxing}, year={2017}, month={Aug}, pages={5163–5173} }
 @article{haribal_neal_li_2017, title={Oxidative dehydrogenation of ethane under a cyclic redox scheme - Process simulations and analysis}, volume={119}, ISSN={["1873-6785"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85007442920&partnerID=MN8TOARS}, DOI={10.1016/j.energy.2016.11.039}, abstractNote={Steam cracking of ethane is an energy intensive process (15–25 GJth/tonne ethylene) involving significant coke formation and CO2/NOx emissions. We propose an alternative two-step redox (or chemical looping) oxidative dehydrogenation (CL-ODH) scheme where hydrogen, produced from ethane cracking, is selectively oxidized by lattice oxygen from a redox catalyst, in the first step. Regeneration of the lattice oxygen in a subsequent step heats the redox catalyst, with the sensible heat providing the thermal energy needed for the cracking reaction. The overall process provides minimal parasitic energy loss and significantly reduced CO2/NOx formation, while favoring ethylene formation through the removal of hydrogen. In the current study, the CL-ODH process is simulated with ASPEN Plus® using experimental data on a Mn-based redox catalyst. The CL-ODH is compared with steam cracking for an ethylene production capacity of 1 million tonne/year. Results indicate that the CL-ODH process, with 85% single-pass ethane conversion, provides 82% reduction in overall energy demand and 82% reduction in CO2 emissions. The overall downstream section consumes approximately 23.5% less energy, with 32.1% less compression work. Increase in the ethane conversion further reduces the energy demand downstream. For every tonne of ethylene, the process has 7.35 GJth excess fuel energy whereas cracking requires an external fuel input of 1.42 GJth.}, journal={ENERGY}, author={Haribal, Vasudev Pralhad and Neal, Luke M. and Li, Fanxing}, year={2017}, month={Jan}, pages={1024–1035} }
 @article{shafiefarhood_zhang_neal_li_2017, title={Rh-promoted mixed oxides for "low-temperature" methane partial oxidation in the absence of gaseous oxidants}, volume={5}, ISSN={["2050-7496"]}, url={https://doi.org/10.1039/C7TA01398A}, DOI={10.1039/c7ta01398a}, abstractNote={Rh promoted mixed-oxides show a syngas productivity of 7.9 mmol g−1 at 600 °C in the absence of gaseous oxidants.}, number={23}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Shafiefarhood, Arya and Zhang, Junshe and Neal, Luke Michael and Li, Fanxing}, year={2017}, month={Jun}, pages={11930–11939} }
 @article{neal_yusuf_sofranko_li_2016, title={Inside Cover: Oxidative Dehydrogenation of Ethane: A Chemical Looping Approach (Energy Technol. 10/2016)}, volume={4}, ISSN={2194-4288}, url={http://dx.doi.org/10.1002/ENTE.201600464}, DOI={10.1002/ENTE.201600464}, abstractNote={Throwing ethane for a chemical loop: The cover art illustration presents a chemical looping (CL)–oxidative dehydrogenation (ODH) scheme for ethylene production from ethane. CL–ODH uses promoted Mg6MnO8 as the oxygen carrier (i.e., redox catalyst). In the ODH reactor, the promoted Mg6MnO8 is reduced while converting ethane to ethylene and water. The reduced redox catalyst is then transferred to the regenerator where it is re-oxidized with air before circulating back to the ODH reactor to complete the chemical loop. Heat from the regenerator is also transferred to the ODH reactor along with the redox catalyst particles. The CL–ODH scheme is shown to be able to achieve significantly higher ethane conversion and ethylene yield than thermal cracking while reducing the energy consumption and CO2/NOx emissions. You can read more in the Full Paper by Luke Neal, Seif Yusuf, John Sofranko, and Fanxing Li from North Carolina State University on page 1200 in Issue 10, 2016 (DOI: 10.1002/ente.201600074).}, number={10}, journal={Energy Technology}, publisher={Wiley}, author={Neal, Luke M. and Yusuf, Seif and Sofranko, John A. and Li, Fanxing}, year={2016}, month={Aug}, pages={1126–1126} }
 @article{gao_neal_li_2016, title={Li-Promoted LaxSr2-xFeO4-delta Core-Shell Redox Catalysts for Oxidative Dehydrogenation of Ethane under a Cyclic Redox Scheme}, volume={6}, ISSN={["2155-5435"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84994627994&partnerID=MN8TOARS}, DOI={10.1021/acscatal.6b01399}, abstractNote={Chemical looping oxidative dehydrogenation (CL-ODH) of ethane utilizes a transition metal oxide based oxygen carrier, also known as a redox catalyst, to convert ethane into ethylene under an autothermal cyclic redox scheme. The current study investigates a Li-promoted LaxSr2–xFeO4−δ (LaSrFe) redox catalyst for CL-ODH reactions. While LaSrFe without Li promoter exhibits low ethylene selectivity, addition of Li leads to high selectivity/yield and good regenerability. Up to 61% ethane conversion and 90% ethylene selectivity are achieved with Li-promoted LaSrFe. Further characterization indicates that the Li-promoted LaSrFe redox catalyst consists of LiFeO2 (disordered rock salt) and LaSrFe (Ruddlesden–Popper) phases. Moreover, the surface of the redox catalysts is enriched with Li cations. It is also determined the LaSrFe phase contributes to oxygen storage and donation, whereas the activity and selectivity of the redox catalysts are modified by the Li promoter: while oxygen for the CL-ODH reaction is suppli...}, number={11}, journal={ACS CATALYSIS}, author={Gao, Yunfei and Neal, Luke M. and Li, Fanxing}, year={2016}, month={Nov}, pages={7293–7302} }
 @article{neal_yusuf_sofranko_li_2016, title={Oxidative Dehydrogenation of Ethane: A Chemical Looping Approach}, volume={4}, ISSN={2194-4288}, url={http://dx.doi.org/10.1002/ENTE.201600074}, DOI={10.1002/ENTE.201600074}, abstractNote={The current study investigates a chemical-looping-based oxidative dehydrogenation (CL-ODH) concept for ethane-to-ethylene conversion. In this cyclic redox scheme, an oxide-based redox catalyst is used to selectively combust hydrogen from ethane dehydrogenation. As the hydrogen product limits ethane conversion, in situ oxidation of hydrogen enhances the ethane conversion and ethylene yield. Moreover, heat required in ODH is compensated by re-oxidation of the oxygen-deprived redox catalyst, enabling auto-thermal operation for the overall process. Compared to steam cracking, CL-ODH can potentially achieve higher efficiency with lower CO2 and NOx emissions. Silica and magnesia-supported manganese oxides are investigated. It is determined that unpromoted Mn/SiO2 and Mn/MgO redox catalysts exhibit low selectivity towards ethylene. The addition of promoters such as sodium and tungsten renders effective redox catalysts with satisfactory activity, selectivity, oxygen carrying capacity, and redox stability.}, number={10}, journal={Energy Technology}, publisher={Wiley}, author={Neal, Luke M. and Yusuf, Seif and Sofranko, John A. and Li, Fanxing}, year={2016}, month={Jun}, pages={1200–1208} }
 @article{neal_shafiefarhood_li_2015, title={Effect of core and shell compositions on MeOx@LaySr1-yFeO3 core-shell redox catalysts for chemical looping reforming of methane}, volume={157}, ISSN={["1872-9118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84945124544&partnerID=MN8TOARS}, DOI={10.1016/j.apenergy.2015.06.028}, abstractNote={The chemical looping reforming (CLR) process converts methane into syngas through cyclic redox reactions of an active lattice oxygen (O2−) containing redox catalyst. In CLR, methane is partially oxidized to CO and H2 using the active lattice oxygen of a redox catalyst. In a subsequent step, the oxygen-deprived redox catalyst is regenerated by air. Such a process can eliminate the need for steam and/or oxygen in reforming, thereby improving methane conversion efficiency. A number of perovskite-structured mixed metal oxides are known to be active for CLR. However, the oxygen storage capacity of perovskites tends to be low, limiting their practical application in chemical looping. In contrast reducible metal oxides such as cobalt and iron oxides can store up to 30 wt.% lattice oxygen but are less selective for syngas generation. We explore oxygen carriers that utilize the advantages of both perovskites and first-row transition metal oxides by integrating a transition metal oxide core with a mixed ionic–electronic conductive (MIEC) perovskite support/shell. MIEC perovskites facilitate countercurrent conduction of O2− and electrons, allowing facile O2− transport though the solid. It is proposed that this conduction allows rapid oxygen transport to and from the transition metal oxide cores irrespective of the porosity of the redox catalyst. In this work, we show that MeOx@LaySr1−yFeO3 can be an excellent model catalyst system for CLR. The activity, selectivity, and coke resistance of the core–shell system can be tuned by changing the ratio of La to Sr in the perovskite shell and the type of transition metal oxide in the core. Our studies indicate that lower Sr loadings can improve activity and selectivity of the catalyst for methane partial oxidation, but make the LSF shell less resistant to decomposition during the reduction step.}, journal={APPLIED ENERGY}, author={Neal, Luke and Shafiefarhood, Arya and Li, Fanxing}, year={2015}, month={Nov}, pages={391–398} }
 @article{galinsky_shafiefarhood_chen_neal_li_2015, title={Effect of support on redox stability of iron oxide for chemical looping conversion of methane}, volume={164}, ISSN={["1873-3883"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84908004028&partnerID=MN8TOARS}, DOI={10.1016/j.apcatb.2014.09.023}, abstractNote={The chemical looping processes utilize lattice oxygen in oxygen carriers to convert carbonaceous fuels in a cyclic redox mode while capturing CO2. Typical oxygen carriers are composed of a primary oxide for active lattice oxygen storage and a ceramic support for enhanced redox stability and activity. Among the various primary oxides reported to date, iron oxide represents a promising option due to its low cost and natural abundance. The current work investigates the effect of support on the cyclic redox performance of iron oxides as well as the underlying mechanisms. Three ceramic supports with varying physical and chemical properties, i.e. perovskite-structured Ca0.8Sr0.2Ti0.8Ni0.2O3, fluorite-structured CeO2, and spinel-structured MgAl2O4, are investigated. The results indicate that the redox properties of the oxygen carrier, e.g. activity and long-term stability, are significantly affected by support and iron oxide interactions. The perovskite supported oxygen carrier exhibits high activity and stability compared to oxygen carriers with ceria support, which deactivate by as much as 75% within 10 redox cycles. The high stability of perovskite supported oxygen carrier is attributable to its high mixed ionic–electronic conductivity. Deactivation of ceria supported samples results from solid-state migration of iron cations and subsequent enrichment on the oxygen carrier surface. This leads to agglomeration and lowered lattice oxygen accessibility. Activity of MgAl2O4 supported oxygen carrier is found to increase during redox cycles in methane. The activity increase is a consequence of surface area increase caused by filamentous carbon formation and oxygen carrier fragmentation. While higher redox activity is desired for chemical looping processes, physical degradation of oxygen carriers can be detrimental.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Galinsky, Nathan L. and Shafiefarhood, Arya and Chen, Yanguang and Neal, Luke and Li, Fanxing}, year={2015}, month={Mar}, pages={371–379} }
 @article{shafiefarhood_hamill_neal_li_2015, title={Methane partial oxidation using FeOx@La0.8Sr0.2FeO3-delta core-shell catalyst - transient pulse studies}, volume={17}, ISSN={["1463-9084"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84947779267&partnerID=MN8TOARS}, DOI={10.1039/c5cp05583k}, abstractNote={Study on the mechanism of C–H bond activation and kinetic pathways of methane conversion using FeOx@La0.8Sr0.2FeO3 redox catalyst.}, number={46}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Shafiefarhood, Arya and Hamill, Joseph Clay and Neal, Luke Michael and Li, Fanxing}, year={2015}, pages={31297–31307} }
 @article{zhou_cheng_neal_zhao_ludden_hagelin-weaver_bowers_2015, title={Parahydrogen enhanced NMR reveals correlations in selective hydrogenation of triple bonds over supported Pt catalyst}, volume={17}, ISSN={["1463-9084"]}, DOI={10.1039/c5cp04223b}, abstractNote={The surface processes resulting in the correlation of semi-hydrogenation selectivity and stereoselective addition to propyne are revealed by parahydrogen enhanced NMR.}, number={39}, journal={PHYSICAL CHEMISTRY CHEMICAL PHYSICS}, author={Zhou, Ronghui and Cheng, Wei and Neal, Luke M. and Zhao, Evan W. and Ludden, Kaylee and Hagelin-Weaver, Helena E. and Bowers, Clifford R.}, year={2015}, pages={26121–26129} }
 @article{zhou_zhao_cheng_neal_zheng_quiñones_hagelin-weaver_bowers_2015, title={Parahydrogen-Induced Polarization by Pairwise Replacement Catalysis on Pt and Ir Nanoparticles}, volume={137}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/JA511476N}, DOI={10.1021/JA511476N}, abstractNote={Pairwise and random addition processes are ordinarily indistinguishable in hydrogenation reactions. The distinction becomes important only when the fate of spin correlation matters, such as in parahydrogen-induced polarization (PHIP). Supported metal catalysts were not expected to yield PHIP signals given the rapid diffusion of H atoms on the catalyst surface and in view of the sequential stepwise nature of the H atom addition in the Horiuti-Polanyi mechanism. Thus, it seems surprising that supported metal hydrogenation catalysts can yield detectable PHIP NMR signals. Even more remarkably, supported Pt and Ir nanoparticles are shown herein to catalyze pairwise replacement on propene and 3,3,3-trifluoropropene. By simply flowing a mixture of parahydrogen and alkene over the catalyst, the scalar symmetrization order of the former is incorporated into the latter without a change in molecular structure, producing intense PHIP NMR signals on the alkene. An important indicator of the mechanism of the pairwise replacement is its stereoselectivity, which is revealed with the aid of density matrix spectral simulations. PHIP by pairwise replacement has the potential to significantly diversify the substrates that can be hyperpolarized by PHIP for biomedical utilization.}, number={5}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Zhou, Ronghui and Zhao, Evan W. and Cheng, Wei and Neal, Luke M. and Zheng, Haibin and Quiñones, Ryan E. and Hagelin-Weaver, Helena E. and Bowers, Clifford R.}, year={2015}, month={Jan}, pages={1938–1946} }
 @article{neal_shafiefarhood_li_2014, title={Dynamic Methane Partial Oxidation Using a Fe2O3@La0.8Sr0.2FeO3-delta Core-Shell Redox Catalyst in the Absence of Gaseous Oxygen}, volume={4}, ISSN={["2155-5435"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84907855041&partnerID=MN8TOARS}, DOI={10.1021/cs5008415}, abstractNote={Chemical looping reforming partially oxidizes methane into syngas through cyclic redox reactions of an active lattice-oxygen (O2–) containing redox catalyst. The avoidance of direct contact between methane and steam and/or gaseous oxygen has the potential to eliminate the energy consumption for generating these oxidants, thereby increasing methane conversion efficiency. This article investigates redox catalysts comprised of iron oxide core covered with lanthanum strontium ferrite (LSF) shell. The iron oxide core serves as the primary source of lattice-oxygen, whereas the LSF shell provides an active surface and facilitates O2– and electron conductions. These core–shell materials have the promise to provide higher selectivity for methane conversion with lower solid circulation rates than traditional redox catalysts. Methane oxidation by this catalyst exhibits four distinct regions, i.e. deep oxidation; competing deep and selective oxidation; selective oxidation with autoactivation; and methane decompositio...}, number={10}, journal={ACS CATALYSIS}, author={Neal, Luke M. and Shafiefarhood, Arya and Li, Fanxing}, year={2014}, month={Oct}, pages={3560–3569} }
 @article{neal_everett_hoflund_hagelin-weaver_2011, title={Characterization of palladium oxide catalysts supported on nanoparticle metal oxides for the oxidative coupling of 4-methylpyridine}, volume={335}, ISSN={1381-1169}, url={http://dx.doi.org/10.1016/j.molcata.2010.11.036}, DOI={10.1016/j.molcata.2010.11.036}, abstractNote={Palladium catalysts supported on various metal oxides were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) to investigate why these catalysts do not show any correlation between the measured Pd surface area and the catalytic activity for the oxidative coupling of 4-methylpyridine to 4,4′-dimethyl-2,2′-bipyridine. The XPS data confirm the classification of n-Al2O3(+), n-MgO and p-SiO2 as non-interacting supports, since the Pd 3d5/2 binding energy (BE) of palladium on these supports is 336.1 eV, consistent with bulk PdO. In contrast, catalysts supported on p-TiO2, n-ZnO, n-ZrO2, n-ZrO2(CeO2), and n-CeO2 have Pd 3d5/2 BEs ranging from 336.3 to 337.4 eV, which reveal varying degrees of metal-support interactions. Metal support interactions leading to electron deficient Pd2+ species are likely beneficial for the reaction due to a facilitated C–H insertion step. While both the PdO/p-TiO2 and PdO/n-TiO2 catalysts have a Pd 3d BE of 336.3 eV, their differences in activity can be attributed to (1) the PdO/n-TiO2 catalyst as prepared having a significantly higher number of hydroxyl groups on the surface compared with the PdO/p-TiO2 catalyst, and (2) the p-TiO2 support being crystalline with an anatase phase, while the n-TiO2 support is nearly amorphous. The presence of surface hydroxyl groups before reaction could hinder the first C–H activation step, and an anatase phase of the support can result in more favorable palladium-support interactions compared with an amorphous TiO2. The XPS data also indicates that while Pd-support interactions are beneficial, very strong interactions, such as in the case of CeO2, can lead to migration of the support over Pd, which reduces the Pd surface area and explains the lower than expected activity of the PdO/n-CeO2 catalyst. On some supports in this study leaching may occur during the reaction, but the characterization data indicate that other factors of catalyst deactivation are more important. XRD reveals that the complete reduction of the PdO particles on the surface is very fast compared to the reaction time. This observation explains why reducible supports with mobile oxygen are beneficial in this reaction. These supports can facilitate the reoxidation of palladium due to strong metal-support interactions. Migration of the support over the active palladium species is another deactivation pathway that appears to be more severe than leaching on these catalysts.}, number={1-2}, journal={Journal of Molecular Catalysis A: Chemical}, publisher={Elsevier BV}, author={Neal, Luke M. and Everett, Michael L. and Hoflund, Gar B. and Hagelin-Weaver, Helena E.}, year={2011}, month={Feb}, pages={210–221} }
 @article{dodson_neal_hagelin-weaver_2011, title={The influence of ZnO, CeO2 and ZrO2 on nanoparticle-oxide-supported palladium oxide catalysts for the oxidative coupling of 4-methylpyridine}, volume={341}, ISSN={1381-1169}, url={http://dx.doi.org/10.1016/j.molcata.2011.03.022}, DOI={10.1016/j.molcata.2011.03.022}, abstractNote={Abstract 4,4′-Dimethyl-2,2′-bipyridine is a useful but expensive chelating agent. Having more efficient routes to the synthesis of this compound would be advantageous to the wide-spread use of this fine chemical. In this work, the effects of adding strongly interacting oxides (ZnO, CeO 2 , and ZrO 2 ) to PdO catalysts supported on high surface area n-Al 2 O 3 (+), n-MgO, and n-TiO 2 prepared via co- and sequential precipitation were investigated. The product yields obtained from these catalysts in the oxidative coupling of 4-methylpyridine are dependent on the additive, the support, and preparation method. Evidently, these are complex catalytic systems in that the PdO–additive and PdO–support interactions must be right to promote product formation while preventing palladium leaching and support or additive migration over the active Pd/PdO sites. Although PdO/n-ZnO catalysts are reasonably active in the coupling reaction, ZnO addition to PdO catalysts supported on n-Al 2 O 3 (+), n-MgO, or n-TiO 2 does not increase the yield in any case. CeO 2 and ZrO 2 can increase the product yields in the reaction depending on the support used. Due to strong PdO–CeO 2 interactions, the addition of CeO 2 in some cases results in CeO x -migration and coverage of active PdO species or disrupts favorable PdO–support interactions leading to Pd leaching. Therefore, ZrO 2 is the better additive with co-precipitated PdO/ZrO 2 /n-Al 2 O 3 (+) consistently producing yields in excess of 3.4 ± 0.1 g/g catalyst which is 36% higher than the 2.5 ± 0.16 g/g catalyst obtained from the PdO/n-Al 2 O 3 (+) (5 wt% Pd), the best catalyst previously reported for this reaction.}, number={1-2}, journal={Journal of Molecular Catalysis A: Chemical}, publisher={Elsevier BV}, author={Dodson, Justin J. and Neal, Luke M. and Hagelin-Weaver, Helena E.}, year={2011}, month={May}, pages={42–50} }
 @article{jones_neal_everett_hoflund_hagelin-weaver_2010, title={Characterization of ZrO2-promoted Cu/ZnO/nano-Al2O3 methanol steam reforming catalysts}, volume={256}, ISSN={0169-4332}, url={http://dx.doi.org/10.1016/j.apsusc.2010.05.021}, DOI={10.1016/j.apsusc.2010.05.021}, abstractNote={Three Cu/ZnO/ZrO2/Al2O3 methanol reforming catalysts were investigated using X-ray photoelectron spectroscopy (XPS). The catalysts which contained ZrO2 from a monoclinic nanoparticle ZrO2 precursor exhibit both a higher activity toward the methanol steam reforming reaction and a lower CO production rate compared to catalysts composed of an XRD-amorphous ZrO2 produced by impregnation using a Zr(NO3)2 precursor. The presence of a monoclinic phase appears to result in an increased charge transfer between the Zr and Cu species, as evidenced by a relatively electron-rich ZrO2 phase and a partially oxidized Cu species on reduced catalysts. This electron deficient Cu species is more reactive toward the methanol reforming reaction and partially suppresses CO formation through the reverse water gas shift or methanol decomposition reactions.}, number={24}, journal={Applied Surface Science}, publisher={Elsevier BV}, author={Jones, Samuel D. and Neal, Luke M. and Everett, Michael L. and Hoflund, Gar B. and Hagelin-Weaver, Helena E.}, year={2010}, month={Oct}, pages={7345–7353} }
 @article{neal_jones_everett_hoflund_hagelin-weaver_2010, title={Characterization of alumina-supported palladium oxide catalysts used in the oxidative coupling of 4-methylpyridine}, volume={325}, ISSN={1381-1169}, url={http://dx.doi.org/10.1016/j.molcata.2010.03.024}, DOI={10.1016/j.molcata.2010.03.024}, abstractNote={A number of PdO/Al 2 O 3 catalysts were characterized using XPS, TEM and XRD. The results reveal that the most active catalysts (palladium oxide supported on nanoparticle alumina; PdO/n-Al 2 O 3 (+)) have both PdO x ( x > 1) and Pd 0 species, in addition to PdO, on the surface. Small nm-sized structures in the support are also important for a high catalytic activity. A number of palladium and palladium oxide on alumina catalysts for the oxidative coupling of 4-methylpyridine were characterized using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) to obtain more information about the properties that govern these reactions. The most active catalysts, the impregnated and precipitated PdO/n-Al 2 O 3 (+), were found to have very broad Pd 3d peaks, suggesting the presence of both PdO 2 and Pd 0 , in addition to PdO, on the surface. This could be due to strong metal–support interactions, which result in more electrophilic palladium or a reduced palladium catalyst that is easier to reoxidize, both of which are expected to result in high catalytic activities. As the PdO is completely reduced to Pd metal on spent catalysts (according to XPS and XRD), facilitated reoxidation could be important in this reaction. While reoxidation is a potential deactivation pathway, carbon deposition is also evident in the XPS spectra and this could block active sites. In contrast, both the XPS and the XRD data indicate that Pd leaching into the reaction solution is not a significant deactivation pathway in the PdO/n-Al 2 O 3 (+) catalyst system. The nm-sized fine structure observed in the supports of the PdO/γ-Al 2 O 3 and PdO/n-Al 2 O 3 (+), together with their measured activities compared to the poorly active PdO/n-Al 2 O 3 (−) catalyst with no such fine structure, supports our hypothesis that low-coordination sites on a support can result in strong metal–support interactions and very active catalysts. Highly active crystalline PdO particles with sizes of 5 nm or below may explain the observed lack of correlation between the measured Pd surface area (which should correlate with the PdO surface area) and the catalytic activity.}, number={1-2}, journal={Journal of Molecular Catalysis A: Chemical}, publisher={Elsevier BV}, author={Neal, Luke M. and Jones, Samuel D. and Everett, Michael L. and Hoflund, Gar B. and Hagelin-Weaver, Helena E.}, year={2010}, month={Jun}, pages={25–35} }
 @article{neal_hernandez_hagelin-weaver_2009, title={Effects of nanoparticle and porous metal oxide supports on the activity of palladium catalysts in the oxidative coupling of 4-methylpyridine}, volume={307}, ISSN={1381-1169}, url={http://dx.doi.org/10.1016/j.molcata.2009.03.006}, DOI={10.1016/j.molcata.2009.03.006}, abstractNote={The oxidative coupling of 4-methylpyridine to 4,4′-dimethyl-2,2′-bipyridine over palladium oxide is a simple, environmentally friendly, one-step process to produce bipyridines, which are commonly used with transition metal ions to form complexes with interesting properties. However, the reaction is slow and the palladium catalyst deactivates during reaction, which means that catalyst improvements are needed for large-scale production of more economically viable bipyridine products. In this study, a number of metal oxides were investigated as catalyst supports and compared to the best performing catalysts to date, i.e. Pd/C and Pd/n-Al2O3(+). Catalysts supported on several nanoparticle oxides with varying properties as well as some conventional supports were prepared and characterized in an attempt to determine properties that lead to high catalytic activities in the oxidative coupling of 4-methylpyridine. It was found that two general categories of active catalysts can be prepared; (1) palladium supported on very high surface area materials, such as Pd/n-Al2O3(+) and Pd/MgO, and (2) palladium supported on metal oxides known to induce strong palladium-support interactions, e.g. Pd/ZrO2, Pd/(n-ZrO2 + n-CeO2) and Pd/n-ZnO. While there is no simple correlation between the palladium surface area and the catalytic activity, higher palladium dispersions generally gave higher yields compared to lower dispersion catalysts. The results indicate that the reaction is structure sensitive, i.e. not all the palladium on the surface is equivalent and some palladium species are more active than others. The acidic and basic properties of the supports were determined via chemisorption of ammonia and carbon dioxide, respectively. The data indicate that there is no correlation between the acidic or basic sites of the supports and the palladium dispersion or the catalytic activity, although highly acidic or highly basic supports should be avoided as they resulted in lower dispersions than expected from their corresponding surface areas. In terms of economic viability the porous TiO2 support was determined to be the most competitive with the nanoparticle alumina support as it results in a catalyst with comparable yields and is less expensive compared with nanoparticle alumina. The palladium supported on nanoparticle ZrO2 and MgO are also promising catalysts.}, number={1-2}, journal={Journal of Molecular Catalysis A: Chemical}, publisher={Elsevier BV}, author={Neal, Luke M. and Hernandez, Daniel and Hagelin-Weaver, Helena E.}, year={2009}, month={Jul}, pages={29–36} }
 @article{neal_hagelin-weaver_2008, title={C–H activation and C–C coupling of 4-methylpyridine using palladium supported on nanoparticle alumina}, volume={284}, ISSN={1381-1169}, url={http://dx.doi.org/10.1016/j.molcata.2008.01.008}, DOI={10.1016/j.molcata.2008.01.008}, abstractNote={The C–H activation and C–C coupling of 4-methyl pyridine to 4,4′-dimethyl-2,2′-bipyridine was studied over palladium catalysts supported on nanoparticle alumina [nano-Al2O3(+)]. Even though Pd/Al2O3 catalysts are traditionally poor catalysts in this reaction, the Pd/nano-Al2O3(+) catalysts prepared via the precipitation method give the highest yield observed to date for this reaction system. The catalytic activity is very dependent on the catalyst preparation as Pd/nano-Al2O3(+) catalysts prepared via the wet impregnation method exhibit poor activities in the reaction. Additionally, a catalyst prepared using another nanoparticle alumina with larger particle sizes [nano-Al2O3(−)] does not have a significant activity. It was shown that using a commercial bimodal γ-Al2O3 support can result in an active catalyst if prepared via the precipitation method, but compared to the best performing catalyst, Pd/nano-Al2O3(+), the yields obtained from Pd/bimodal-γ-Al2O3 are lower and less reproducible. Pd surface area measurements indicate that the reaction is structure sensitive as there is no correlation between the Pd surface area and the catalytic activity. The reaction is also very sensitive to reactant quality and the 4-methyl pyridine must be distilled over KOH to ensure reproducible yields. Additional experiments indicate that this reaction requires a solid phase for catalysis.}, number={1-2}, journal={Journal of Molecular Catalysis A: Chemical}, publisher={Elsevier BV}, author={Neal, Luke M. and Hagelin-Weaver, Helena E.}, year={2008}, month={Apr}, pages={141–148} }
 @article{jones_neal_hagelin-weaver_2008, title={Steam reforming of methanol using Cu-ZnO catalysts supported on nanoparticle alumina}, volume={84}, ISSN={0926-3373}, url={http://dx.doi.org/10.1016/j.apcatb.2008.05.023}, DOI={10.1016/j.apcatb.2008.05.023}, abstractNote={Methanol steam reforming was studied over several catalysts made by deposition of copper and zinc precursors onto nanoparticle alumina. The results were compared to those of a commercially available copper, zinc oxide and alumina catalyst. Temperature programmed reduction, BET surface area measurements, and N2O decomposition were used to characterize the catalyst surfaces. XRD was used to study the bulk structure of the catalysts, and XPS was used to determine the chemical states of the surface species. The nanoparticle-supported catalysts achieved similar conversions as the commercial reference catalyst but at slightly higher temperatures. However, the nanoparticle-supported catalysts also exhibited a significantly lower CO selectivity at a given temperature and space time than the reference catalyst. Furthermore, the turnover frequencies of the nanoparticle-supported catalysts were higher than that of the commercial catalyst, which means that the activity of the surface copper is higher. It was determined that high alumina concentrations ultimately decrease catalytic activity as well as promote undesirable CH2O formation. The lower catalytic activity may be due to strong Cu-Al2O3 interactions, which result in Cu species which are not easily reduced. Furthermore, the acidity of the alumina support appears to promote CH2O formation, which at low Cu concentrations is not reformed to CO2 and H2. The CO levels present in this study are above what can be explained by the reverse water-gas-shift (WGS) reaction. While coking is not a significant deactivation pathway, migration of ZnO to the surface of the catalyst (or of Cu to the bulk of the catalyst) does explain the permanent loss of catalytic activity. Cu2O is present on the spent nanoparticle catalysts and it is likely that the Cu+/Cu0 ratio is of importance both for the catalytic activity and the CO selectivity.}, number={3-4}, journal={Applied Catalysis B: Environmental}, publisher={Elsevier BV}, author={Jones, Samuel D. and Neal, Luke M. and Hagelin-Weaver, Helena E.}, year={2008}, month={Dec}, pages={631–642} }