@article{jiang_savithri_du_pawar_jameel_chang_zhou_2017, title={Fractionation and Characterization of Kraft Lignin by Sequential Precipitation with Various Organic Solvents}, volume={5}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.6b02174}, abstractNote={The value-added utilizations of technical lignin are restricted by its heterogeneous features, such as high polydispersity, complex functional group distribution, ununiformed reactivity, etc. Fractionation of lignin into more homogeneous parts represents a promising approach to overcome this challenge. In the present study, softwood kraft lignin was fractionated into four different portions (F1, F2, F3, and F4) by first dissolving it in a methanol–acetone mixture followed by sequential precipitation with various organic solvents (ethyl acetate, 1:1 ethyl acetate/petroleum ether, petroleum ether) of decreasing solubility parameters. The yields of various fractions F1, F2, F3, and F4 were 48%, 39%, 10%, and 3%, respectively. The results from gel permeation chromatography indicated that the molecular weights of each fraction decreased from F1 to F4. The lowest molecular weight fraction F4 contained mainly monomeric and dimeric aromatic structures such as guaiacol and vanillin formed from lignin degradation. ...}, number={1}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Jiang, Xiao and Savithri, Dhanalekshmi and Du, Xueyu and Pawar, Siddhesh and Jameel, Hasan and Chang, Hou-Min and Zhou, Xiaofan}, year={2017}, month={Jan}, pages={835–842} }
 @article{du_lucia_ghiladi_2016, title={A Novel Approach for Rapid Preparation of Monophasic Microemulsions That Facilitates Penetration of Woody Biomass}, volume={4}, ISSN={2168-0485 2168-0485}, url={http://dx.doi.org/10.1021/acssuschemeng.5b01601}, DOI={10.1021/acssuschemeng.5b01601}, abstractNote={Microemulsions are a straightforward, efficient, and highly useful complex media for flooding/wetting substrates as a result of their low surface tension and viscosity. Among the four broad general classes of microemulsions (Winsor-I, -II, -III, and -IV), Winsor-IV is by far considered the ideal microemulsion type within the context of woody biomass pretreatment because it is a single phase. In the present study, a never-before reported titration method was developed with the intent of providing a rapid online determination of Winsor-IV type microemulsion formulations under fixed surfactant concentrations for expressly treating woody biomass. A total of 108 surfactant-oil–water formulations based on a sodium dodecylsulfate/pentanol/water/sodium chloride/dodecane system were investigated for their phase behavior, 54 of which yielded Winsor-IV type microemulsions. The ability of the selected microemulsions to affect the crystallinity of cellulose was studied by X-ray diffraction as was the synergetic effect...}, number={3}, journal={ACS Sustainable Chemistry & Engineering}, publisher={American Chemical Society (ACS)}, author={Du, Xueyu and Lucia, Lucian A. and Ghiladi, Reza A.}, year={2016}, month={Feb}, pages={1665–1672} }
 @article{du_lucia_ghiladi_2016, title={Development of a Highly Efficient Pretreatment Sequence for the Enzymatic Saccharification of Loblolly Pine Wood}, volume={4}, ISSN={2168-0485 2168-0485}, url={http://dx.doi.org/10.1021/acssuschemeng.6b00198}, DOI={10.1021/acssuschemeng.6b00198}, abstractNote={The efficient pretreatment of lignocellulosic materials for bioenergy production is a critical step upon which efficient saccharification is highly dependent, particularly in softwoods due to both their high lignin content and condensed lignin structures. In the present study, preliminary pretreatment steps (e.g., Wiley milling, acetone extraction, autohydrolysis, and disc refining) and economical subsequent/core-pretreatment steps (e.g., reagents immersion, hydrothermolysis, dilute acid hydrolysis, and ionic liquids treatment) were systematically investigated to identify which combinations led to effective enzymatic saccharification of loblolly pine wood, the dominant softwood resource in the US. The results demonstrated that 85% phosphoric acid based immersions were highly efficient for both cellulose crystallinity degradation and enzymatic hydrolysis, and thus can be included as core pretreatment steps. The highest glucan recovery yield obtained was 93.0% after enzymatic hydrolysis when a pretreatment ...}, number={7}, journal={ACS Sustainable Chemistry & Engineering}, publisher={American Chemical Society (ACS)}, author={Du, Xueyu and Lucia, Lucian A. and Ghiladi, Reza A.}, year={2016}, month={Jun}, pages={3669–3678} }
 @article{hu_du_liu_chang_jameel_2016, title={Structural Characterization of Pine Kraft Lignin: BioChoice Lignin vs Indulin AT}, volume={36}, ISSN={["1532-2319"]}, DOI={10.1080/02773813.2016.1214732}, abstractNote={BioChoice lignin (BCL) is a newly commercialized pine kraft lignin from Plymouth Mill of Domtar, which is precipitated from black liquor of bleachable-grade pulp. Indulin AT is a pine kraft lignin commercialized by Meadwestvaco for the past 60 years, which is precipitated from black liquor of linerboard-grade pulp. Thus, the two technical lignins are produced under quite different conditions in terms of alkali charge and pulping time/temperature. While the chemical structure of Indulin AT is well documented, that of BCL is totally unknown. In this study, chemical structures of BCL and Indulin AT are characterized using modern analytical techniques and compared with those of pine milled wood lignin (MWL) in order to elucidate the structural changes that occur during kraft pulping and the structural differences, if any, between BCL and Indulin AT. Both BCL and Indulin AT are structurally very different from the native lignin (MWL) in wood, indicating drastic structural modification during the kraft pulping process. Surprisingly, BCL and Indulin AT are structurally very similar, in spite of the fact that they are produced under different process conditions. However, there are subtle structural differences between BCL and Indulin AT. BCL has higher phenolic hydroxyl, catechol, enol ether, and stilbene contents, but lower methoxyl and β-O-4 contents. These differences are explained by the different pulping conditions under which the two technical lignins are produced.}, number={6}, journal={JOURNAL OF WOOD CHEMISTRY AND TECHNOLOGY}, author={Hu, Zhoujian and Du, Xueyu and Liu, Jie and Chang, Hou-min and Jameel, Hasan}, year={2016}, pages={432–446} }