Effect of zeolite structure and Si/Al ratio on cotton stalks hydropyrolysis.

Zeolites, being acidic, act as the most promising catalytic materials for deoxygenating reactive oxygenated compounds produced during the pyrolysis of lignocellulosic biomass. Herein, two zeolites, HY and HZSM-5, with different Si/Al ratios, were employed to investigate the effect of zeolite structure on aromatic hydrocarbons (AHs) production during flash hydropyrolysis of cotton stalks (Temperature = 800 ˚C, H2 pressure = 10 bar). Both the zeolites enhanced AHs production. However, the pore structure and pore size of HZSM-5 marked a pronounced effect on the reduction of oxygenated compounds. With an increase in Si/Al ratio, AHs area% was found to decrease owing to the decrease in acidity. Ni/zeolite catalysts were also investigated to look into the effect of metal loading on the catalytic properties of zeolites. Ni/zeolite catalysts enhanced the aromatic and aliphatic hydrocarbon production by further conversion of phenolics and other oxygenated compounds due to the promotion of direct deoxygenation, decarbonylation and decarboxylation reactions.

Anisole hydrodeoxygenation over Ni-Co bimetallic catalyst: a combination of experimental, kinetic and DFT study.

Catalytic hydrodeoxygenation (HDO) of anisole was performed with a series of Ni and Co containing catalysts with different weight ratios on activated carbon (AC) for cyclohexanol production. The catalytic activities of various catalysts revealed that Ni5Co5-AC was the best catalytic system. Structural analysis obtained from XRD, TPR, XPS, and TEM evidently demonstrates that Ni5Co5-AC sample consists of a distorted metal alloy spinel structure and optimum particle size, enhancing its catalytic performance. Kinetics were investigated to identify cyclohexanol production rate, activation energy, and reaction pathway. Structural, experimental, kinetics and density functional simulations suggested that high amount of distorted metallic alloy in Ni5Co5-AC, presence of water, high adsorption efficiency of anisole, and low adsorption tendency of cyclohexanol on metallic alloy surface were the critical factors for HDO of anisole to cyclohexanol.

Oxidative valorisation of lignin into valuable phenolics: Effect of acidic and basic catalysts and reaction parameters.

The aromatic nature of lignin makes it a good source for the production of numerous platform chemicals. The valorization of lignin into valuable compounds depends upon the type of bonds and functionality present in lignin. Here, we have studied the depolymerization of rice straw alkali lignin in N2 and O2 with acidic (ZSM-5), basic (MgO) catalyst and with their mixtures (1:1, 3:7 and 7:3). The effect of hydrogen peroxide on lignin depolymerization was also examined. Maximum yield of bio-oil (50 wt%) was obtained with pure ZSM-5 and 1 ml hydrogen peroxide in nitrogen atmosphere, while maximum conversion (60%) was observed in oxygen environment during the non-catalytic depolymerization of lignin. Bio-oil characterization through GC-MS showed maximum selectivity towards 2-methoxy-4-vinylphenol with 38.5 area% in the bio-oil of ZSM-5-N2. The bio-oils have also been characterized using 1H NMR, FT-IR and GC-MS.