Ethanol dehydration to diethyl ether over ZSM-5 and β-Zeolite supported Ni W catalyst

Value-added bioproducts by bioethanol dehydrogenation to acetaldehyde through Cu and Zn modified biochar catalysts

In this study, the efficiency of a series of biochar-supported Cu catalysts, biochar-supported Zn catalysts, and biochar-supported Cu-Zn catalysts was determined through bioethanol dehydrogenation to the high-value chemical, acetaldehyde. Each metal, with weight percentages of 10, 20, and 30, and the combination of Cu-Zn, including 10 wt% of Cu and Zn, 15 wt% of Cu - 5 wt% of Zn, and 15 wt% of Cu and Zn, were fully loaded onto biochar using an incipient wetness impregnation technique. Subsequently, all biocatalysts were subjected to bioethanol dehydrogenation reactions in a temperature range of 200-400 °C. The optimum metal loading for the catalyst was found to be the combination of 15 wt% Cu and 15 wt% Zn. This catalyst resulted in a reasonable acetaldehyde yield of 56.2%, an initial bioethanol conversion of 57.3%, and a very high acetaldehyde selectivity of 98.1% at a mild reaction temperature of 300 °C and ambient pressure. These results were attributed to the optimal concentration of weak-medium acid and medium base sites. Active acid and base sites were identified through temperature-programmed desorption of ammonia (NH3-TPD) and temperature-programmed desorption of carbon dioxide (CO2-TPD), respectively. Furthermore, the reaction stability test of the best biocatalyst (15Cu-15Zn/BB) was proven by maintaining this reaction at the same temperature (300 °C) for 10 h. However, the catalytic performance slightly decreased due to the coke formation of Cu species.

Enhanced Isopropyl Alcohol Conversion over Acidic Nickel Phosphate-Supported Zeolite Catalysts

In this preliminary research, the catalytic activity of isopropyl alcohol conversion to diisopropyl ether through dehydration reaction catalyzed by zeolite-Ni and zeolite-Ni(H₂PO₄)₂ was comparatively described. The natural zeolite was treated with 1% HF and 6 N HCl prior to modifications using the impregnation method. Isopropyl alcohol conversion was examined at a mild temperature of 150 °C for 3.5 h on the reflux system with various catalyst loadings. X-ray diffraction and Fourier transform infrared analysis confirmed the successful impregnation of nickel and nickel phosphate into the zeolite. Scanning electron microscopy analysis revealed a cubic-like structure on zeolite-Ni(H₂PO₄)₂, whereas homogenously distributed nickel species were observed on the zeolite-Ni catalyst. Energy-dispersive X-ray spectroscopy analysis reinforced the accomplishment of zeolite modifications. The N₂ physisorption isotherms showed a decline in the surface area and total pore volume of the zeolite because of the blocking of pores. The zeolite-Ni(H₂PO₄)₂ catalyst had higher acidity than unmodified zeolite and zeolite-Ni catalysts, which inherently suggested that the presence of phosphate groups results in higher catalytic activity toward isopropyl alcohol. The highest catalytic activity was attained by 8 mEq/g metal loading zeolite-Ni(H₂PO₄)₂ with isopropyl alcohol conversion of 81.51%, diisopropyl ether yield, and selectivity of 40.77 and 33.16%. The reusability study suggested that the zeolite-Ni(H₂PO₄)₂ catalyst was still active and had sufficient catalytic activity stability toward isopropyl alcohol after the third cycle was reused. This nickel phosphate-based modified zeolite was adequately potential for diisopropyl ether production through isopropyl alcohol dehydration.