@article{xu_carbonell_kiserow_roberts_2005, title={Hydrogenation of polystyrene in CO2-expanded solvents: Catalyst poisoning}, volume={44}, ISSN={["0888-5885"]}, DOI={10.1021/ie040243q}, abstractNote={Organic solvents expanded with supercritical carbon dioxide can be excellent media for hydrogenation reactions. However, catalyst poisoning by CO formed via the reverse water-gas-shift reaction occurs during many hydrogenations in the presence of CO2. In this research, the hydrogenation of polystyrene in CO2-expanded decahydronaphthalene was studied in a batch reactor using two hydrogenation catalysts, 5%Pd/BaSO4 and 65%Ni/Al2O3/SiO2. The 5%Pd/BaSO4 catalyst deactivated at 150 °C and CO2 pressures of 250−2250 psig (1.8−15.6 MPa). Approximately 50 ppm CO was present in the CO2-rich light phase after about 10 h at 150 °C, 750 psig H2 pressure, and 2250 psig CO2 pressure. A model that incorporates CO poisoning was developed to describe deactivation of the Pd/BaSO4 catalyst. The 65%Ni/Al2O3/SiO2 catalyst was more active for ring hydrogenation than 5%Pd/BaSO4, and very little CO was formed in the presence of CO2. The Ni catalyst deactivated in the presence of CO2 at 180 °C, possibly due to H2O formed in a meth...}, number={16}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Xu, DW and Carbonell, RG and Kiserow, DJ and Roberts, GW}, year={2005}, month={Aug}, pages={6164–6170} }
 @article{whittier_xu_zanten_kiserow_roberts_2006, title={Viscosity of polystyrene solutions expanded with carbon dioxide}, volume={99}, ISSN={["1097-4628"]}, DOI={10.1002/app.22483}, abstractNote={AbstractThe viscosity of solutions of polystyrene (PS) in decahydronaphthalene (DHN) was measured in the presence of carbon dioxide (CO2) with a moving‐piston viscometer. The effects of the CO2 pressure (0–21 MPa), polymer concentration (1–15 wt %), temperature (306–423 K), and polymer molecular weight (126 and 412 kDa) on the viscosity were investigated. In the absence of CO2, the increase in the viscosity with increasing polymer concentration was approximately exponential in concentration and was well described by the Martin equation. All the data fell on a single line when the relative viscosity was plotted against cM0.50 (where c is the concentration of the polymer in solution and M is the molecular weight of the polymer). The viscosity of the polymer solution decreased with increasing CO2 pressure under otherwise constant conditions. For a given CO2 pressure, the viscosity reduction was greatest when the relative viscosity was high in the absence of CO2, that is, for high‐molecular‐weight polymer, high polymer concentrations, and low temperatures. Reductions in the relative viscosity of almost 2 orders of magnitude were observed in some cases. The viscosity of solutions of PS in DHN also was measured in the presence of sulfur hexafluoride (SF6). At a given pressure, SF6 was about as effective as CO2 in reducing the solution viscosity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 540–549, 2006}, number={2}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Whittier, RE and Xu, DW and Zanten, JH and Kiserow, DJ and Roberts, GW}, year={2006}, month={Jan}, pages={540–549} }
 @misc{roberts_xu_kiserow_carbonell, title={Hydrogenation of polymers in the presence of supercritical carbon dioxide}, volume={7,408,009}, number={2007 Apr. 11}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Roberts, G. W. and Xu, D. and Kiserow, D. J. and Carbonell, R. G.} }