Pingkai Ouyang

In situ hydrogenation and decarboxylation of oleic acid into heptadecane over a Cu–Ni alloy catalyst using methanol as a hydrogen carrier

In this work, supported Cu–Ni bimetallic catalysts were synthesized and evaluated for the in situ hydrogenation and decarboxylation of oleic acid using methanol as a hydrogen donor. The supported Cu–Ni alloy exhibited a significant improvement in both activity and selectivity towards the production of heptadecane in comparison with monometallic Cu and Ni based catalysts. The formation of the Cu–Ni alloy is demonstrated by high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM), energy dispersive X-ray spectroscopy (EDS-mapping), X-ray diffraction (XRD) and temperature programmed reduction (TPR). A partially oxidized Cu in the Cu–Ni alloy is revealed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) following CO adsorption and X-ray photoelectron spectroscopy (XPS). The temperature programmed desorption of ethylene and propane (ethylene/propane-TPD) suggested that the formation of the Cu–Ni alloy inhibited the cracking of C–C bonds compared to Ni, and remarkably increased the selectivity to heptadecane. The temperature programmed desorption of acetic acid (acetic acid-TPD) indicated that the bimetallic Cu–Ni alloy and Ni catalysts had a stronger adsorption of acetic acid than that of the Cu catalyst. The formation of the Cu–Ni alloy and a partially oxidized Cu facilitates the decarboxylation reaction and inhibits the cracking reaction of C–C bonds, leading to enhanced catalytic activity and selectivity.

Enhancement in the aromatic yield from the catalytic fast pyrolysis of rice straw over hexadecyl trimethyl ammonium bromide modified hierarchical HZSM-5

Modified H-type ZSM-5 (HZSM-5) catalysts were prepared using hexadecyl trimethyl ammonium bromide (CTAB) as mesopore templates to enhance the activity for the catalytic fast pyrolysis of rice straw for aromatics compounds. A certain quantity of CTAB added into the HZSM-5 (HZ) forming hierarchical structure exhibited an improvement in the yield of the aromatics and a decrease in the yield of coke in comparison with that of bare HZ. In contrast, excessive CTAB addition resulted in a decrease in aromatic yield and an increase in coke yield. The effects of crystallinity, textural properties, morphological structure and acidity distribution on the production of aromatic compounds were measured by XRD, BET, TEM and NH3-TPD. The good crystallinity, small amount of mesopore formation and highest total acidity discovered in HZ-0.01 (the mole ratio of CTAB/SiO2 is 0.01) provided the highest aromatic compound yield of 26.8% and the lowest coke yield of 39.2%.

Catalytic decarbonylation of stearic acid to hydrocarbons over activated carbon-supported nickel

In this study, the deoxygenation of stearic acid over a series of Ni-based catalysts in the absence of hydrogen and solvents was investigated. Ni/Al2O3, Ni/TiO2, Ni/ZrO2, and Ni/AC (activated carbon) were synthesized using the wetness impregnation method, and Ni/AC showed the best activity for deoxygenation. X-ray diffraction, transmission electron microscopy, H2 temperature-programmed reduction, and N2 adsorption–desorption analyses revealed that Ni had an average particle size of about 9.6 nm with good crystallinity, the largest surface area and strong Ni–carrier interactions in Ni/AC. These properties of Ni/AC contributed to its good deoxygenation activity. Ni/AC produced hydrocarbons (71.4% yield) such as heptadecane, heptadecene, aromatics, and cracking paraffins under optimized reaction conditions. Furthermore, it was found that the deoxygenation of stearic acid over Ni/AC in the absence of hydrogen and solvent proceeds mainly via decarbonylation.