Weimiao Chen

Glycerol dehydration to acrolein over activated carbon-supported silicotungstic acids

Activated carbon (AC)-supported silicotungstic acid (H-4[SiW12O40] center dot nH(2)O, HSiW) catalysts were employed to produce acrolein from glycerol dehydration. The results indicated that catalysts with 10% HSiW loading exhibited the highest activity and selectivity. The space time yield of acrolein reached 68.5 mmol/(g.h), which is the best result ever reported in the literature. The properties of the catalysts were closely related to the HSiW dispersion and the relative quantities of strong acid sites.

Solvent Effect on Selective Dehydroxylation of Glycerol to 1,3-Propanediol over a Pt/WO3/ZrO2 Catalyst

Different solvents were studied for dehydroxylation of glycerol to1,3-propanediol over a Pt/WO3/ZrO2 catalyst. Protic solvents such as ethanol and water favored the formation of 1,3-propanediol from glycerol. Binary solvents containing a protic component showed a synergetic solvent effect on the selective dehydroxylation of glycerol to 1,3-propanediol. The protic component in the binary solvent influenced the performance of the Pt/WO3/ZrO2 catalyst.

Synthesis of Mixed Alcohols from CO Hydrogenation over Iron and Nickel Metal Phosphide Catalysts

A series of silica supported iron and nickel metal phosphides with different molar ratios of P to metal were synthesized by the temperature programmed reduction method. Their catalytic performance for CO hydrogenation in a fixed bed reactor was tested with the conditions of 553 K, 5.0 MPa, and H2:CO = 2 (molar ratio). With the FePx/SiO2 catalysts (x denotes the molar ratio of P to metal), the product was a mixture of oxygenates containing methanol as the major component. With the NiPx/SiO2 samples, the liquid product was mainly methanol. The Fe2P, Fe3P, Ni, Ni2P, Ni3P, and Ni12P5 phases were stable during CO hydrogenation, while most of the metallic Fe phase transformed into iron carbide.

Temperature-programmed desorption and surface reaction studies of CO on Co2C

Cobalt carbide(Co2C) samples were prepared by carburizing Co with CO at 473 K for in excess of 400 h and were characterized by X‐ray diffraction, transmission electron microscopy, CO temperature‐programmed reduction, CO temperature‐programmed desorption(CO‐TPD), and CO temperature‐programmed surface reaction. The prepared Co2C samples were composed of bulk Co2C with a surface CoO passivation layer. The passivation layer could be removed by reaction with CO at 477 K.CO desorbing at low temperature in CO‐TPD experiments likely originated from chemisorbed CO. CO desorbing at high temperature was likely due to residual CO within the Co2C crystal lattice. CO adsorbed on Co2C reacted with H2 to form alcohol.

Fischer-Tropsch synthesis: Characterizing and reaction testing of Co2C/SiO2 and Co2C/Al2O3 catalysts

SiO2- and Al2O3-supported CO2C catalysts were prepared by carburizing supported Co precursors with CO. The catalysts were characterized by N-2 physisorption, X-ray diffraction and H-2 temperature-programmed reduction techniques, and evaluated by the Fischer-Tropsch (F-T) reaction. The results showed that SiO2- and Al2O3-supported Co2C catalysts could be successfully obtained but sufficient carburization time was required. All of the as-prepared supported Co2C catalysts exhibited activity and selectivity towards alcohols. It is considered that surface metallic Co species contributed to the activity, surface Co2C species were responsible for the formation of alcohols, and bulk CO2C species were inert during the F-T reaction

Fischer-Tropsch reaction over cobalt catalysts supported on zirconia-modified activated carbon

An attractive Fischer-Tropsch catalyst was prepared using an activated carbon as carrier to support cobalt based catalysts. Zr promoted Co/AC catalysts remarkably enhanced the activity and the selectivity toward diesel distillates and lower the methane selectivity. This modification may be attributed to specific behavior of activated carbon with high surface area and the weak interaction between metallic cobalt active sites and activated carbon. It was emphasized that the pore size of activated carbon played a very important role in restricting the growth of carbon chain to wax.

Promotional effects of Cr and Fe on Rh/SiO2 catalyst for the preparation of ethanol from CO hydrogenation

A series of Cr and Fe promoted Rh-based silica supported catalysts were prepared by an incipient co-impregnation method. The performance of the catalysts was investigated by the hydrogenation of carbon monoxide to ethanol. The catalysts were characterized by N2 adsorption–desorption, X-ray diffraction, transmission electron microscopy, H2 temperature-programmed reduction, temperature programmed surface reaction, and Fourier transform infrared spectroscopy. The results revealed that addition of 0.2–0.4 wt% Cr to Rh/SiO2 increased its activity significantly. However, further addition of 0.1–0.2 wt% Fe lowered CO conversion slightly, while the selectivity towards ethanol was enhanced significantly. Therefore, high catalytic activity and selectivity toward ethanol were achieved by simultaneous introduction of 0.4 wt% Cr and 0.2 wt% Fe to Rh/SiO2. This may be due to improved dispersion of Rh particles, moderate ability to dissociate CO molecules, and high ratio of Rh+ sites to Rh0 sites.

The promotion effects of Mn, Li and Fe on the selectivity for the synthesis of C2 oxygenates from syngas on rhodium based catalysts

Abstract Rh-based catalysts with the promoters of Mn, Li and Fe were prepared. The activity of the catalyst for C2 oxygenates formation enhanced with the addition of additives. The promotion effects of these additives were investigated by means of FT-IR, CO-TPD and TPSR of adsorbed CO with H2. IR results suggested that Fe, Mn and Li might be in close contact with Rh, and formed new active sites, which promoted CO activation on Rh surface and favored the formation of C2 oxygenated intermediates. The results of CO-TPD and TPSR showed that only a part of adsorbed CO on the catalyst could be hydrogenated into CH4. The ratio of CH4 quantity in TPSR to that of desorbed CO in CO-TPD on various catalysts was calculated, and it decreased in the order: Rh/SiO2 >Rh-MrdSiO2 >Rh-Mn-Li/SiO2 >Rh-Mn-Li-Fe/SiO2,whichimpliedthat non-dissociated CO increased in the reverse order. Which was consistent with the catalytic activity of C2 oxygenates formation sequence. The improvement of the space-time yield (STY) and selectivity towards C2 oxygenates could be explained based on that the increase of the nondissociative CO and the decrease of dissociative CO on the catalyst favored the insertion of CO into CHx.

Different Carriers-Supported Rh-Based Catalysts for Oxidative Bromination of Methane: Different Carriers-Supported Rh-Based Catalysts for Oxidative Bromination of Methane

Oxidative bromination of methane over Rh-based catalysts supported on different carriers was studied using a conventional fixed-bed reactor at atmosphere pressure. It was found that inert supports such as SiC and SiO(2) were in favor of the selectivity for bromomethanes, whereas deep oxidation occurred over ZrO(2) and TiO(2) oxides. H(2)-temperature-programmed reduction experiments confirmed that inert carrier-supported Rh catalysts were more difficult to be reduced than the metal oxide-supported Rh catalysts. Thermodynamic analysis revealed that the steam reforming of bromomethanes was promoted at higher reaction temperatures. It was concluded that the superior performance of the inert carrier-supported catalysts could be ascribed to the medium redox ability, which suppressed the steam reforming reaction. Among the catalysts studied, Rh/SiC showed the highest methane conversion and selectivity for bromomethanes, and therefore the key parameters of catalyst preparation and reaction conditions were optimized on this catalyst. About 20% methane conversion and 90% total selectivity for bromomethanes were achieved on a single pass at 620 degrees C with the gas hourly space velocity and liquid hourly space Velocity of 900 and 3.0 ml/(g.h), respectively. No deactivation happened during 100 h time-on-stream.