Catalytic properties of different copper-containing catalysts synthesized from different precursors were studied in the hydrogenation of lactic acid at mild conditions. The most active catalyst was found to be chrysocolla-like copper hydroxysilicate with the copper loading of about 50 at%. At the optimal reaction conditions (T = 473 K, WHSV = 0.08 h -1 ), 95% conversion of lactic acid over this catalyst and 65% selectivity to 1,2-propylene glycol were achieved. The effect of the weight hourly space velocity (WHSV) on the lactic acid conversion and selectivity to propylene glycol was studied. It is found that the formation of propylene glycol and propanoic acid as a byproduct proceeds via parallel pathways.
This paper reports the results of a study of a water-gas shift reaction over nickel-ceria catalysts with different metal loading. Within this study, the overall CO conversion and observed kinetic behavior were investigated over the temperature range of 250-550 • C in different reactor configurations (fixed-bed and microchannel reactors). The quasi-steady state kinetics of the CO water-gas shift reaction was studied for fractions of Ni-containing cerium oxide catalysts in fixed-bed experiments at lab-scale level using a very dilute gas (1% CO + 1.8% H 2 O in He). A set of experiments with a microchannel reactor was performed using the feed composition (CO:H 2 O:H 2 :N 2 = 1:2:2:2), representing a product gas from methane partial oxidation. The results were interpreted using computational models. The kinetic parameters were determined by regression analysis, while mechanistic aspects were considered only briefly. Simulation of the WGS reaction in the microreactor was also carried out by using the COMSOL Multiphysics program.
Nickel-containing mixed ceria-zirconia oxides also doped by Nb and Ti have been prepared by a citrate route and by original solvothermal continuous flow synthesis in supercritical alcohols. Nickel was subsequently deposited by conventional insipient wetness impregnation. The oxides are comprised of ceria-zirconia solid solution with cubic fluorite phase. Negligible amounts of impurities of zirconia are observed for samples prepared by citrate route and doped by Ti. Supports prepared by supercritical synthesis are single-phased. XRD data, Raman, and UV-Vis DR (diffuse reflectance) spectroscopy suggest increasing lattice parameter and amount of oxygen vacancies in fluorite structure after Nb and Ti incorporation despite of the preparation method. These structural changes correlate with the catalytic activity in a methane dry reforming reaction. Catalysts synthesized under supercritical conditions are more active than the catalysts of the same composition prepared by the citrate route. The catalytic activity of samples doped with Ti and Nb is two times higher in terms of TOF (turnover frequency) and increased stability of these catalysts is attributed with the highest oxygen mobility being crucial for gasification of coke precursors.
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