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Kinetics of guaiacol hydrodeoxygenation (HDO) was studied using supported MoxC–SBA-15 and as a comparison 5 wt% Pt/C under 30 bar hydrogen at 200 °C and 300 °C. Catalyst characterization was done by a range of physical methods including also determination of the amount of coke and the nature of adsorbed species. Pt/C gave 2-methoxycyclohexanol as the main product, whereas Mo2C–SBA-15 promoted direct deoxygenation exhibiting also strong adsorption of guaiacol on the catalyst surface and formation of oligomers. Thermodynamics of guaiacol HDO was elucidated and the reaction network was proposed based on which kinetic modelling was done. Graphic Abstract: [Figure not available: see fulltext.]

Transformations of glucose to 1,2-propylene glycol were studied over a mechanical mixture of ZnO and Ru/C catalysts in the presence of hydrogen. Different reaction conditions were evaluated by changing the reaction temperature and hydrogen pressure. In addition to the cascade mode of operation, also separate steps in the overall reaction network, such as hydrogenation of pyruvaldehyde and hydroxyacetone to 1,2-propylene glycol were investigated. Fructose as a starting material was also studied resulting in a propylene glycol yield of 37.5%. The optimal temperature for glucose transformation to propylene glycol was found to be 165 °C. The influence of temperature on the catalytic behavior was more prominent than the effect of hydrogen pressure. Thermodynamic analysis of glucose transformation to 1,2-propylene glycol was performed and a plausible kinetic model reflecting a complex reaction network was developed being able to describe the data in a reliable way.

Dehydration and etherification of bio-ethanol was studied in a microreactor using γ-alumina, H-Beta-38 and Sn-Beta-38 as catalysts. An extensive series of kinetic experiments was carried out in the microreactor device operating at ambient pressure and temperatures 225–325 °C. The H-Beta-38 catalyst coated microplates exhibited the highest production rate of ethene. While the fresh H-Beta-38 catalyst allowed complete conversion of ethanol and 98% selectivity towards ethene, the catalyst deactivated significantly with time-on-stream. Diethyl ether was the dominating co-product, whereas trace amounts of acetaldehyde were detected in the experiments. Based on the kinetic studies, thermodynamic analysis and catalyst characterization results obtained with SEM-EDX, TEM, nitrogen physisorption, FTIR-Pyridine and white light confocal microscopy, a surface reaction mechanism was proposed. The fundamental hypothesis of the reaction mechanism was the co-existence of two kinds of active sites on the catalyst surface, namely the Bronsted sites promoting dehydration and the Lewis sites responsible for etherification. The Bronsted sites deactivate, whereas the Lewis sites are more stable, which leads to a shift of the product distribution during long-term experiments, from ethene to diethyl ether. The rate equations were implemented in the microreactor model. The kinetic and adsorption parameters included in the model were estimated by non-linear regression analysis. The experimental data were satisfactorily described by the proposed mechanism. The work demonstrated that microreactors are strong tools in the determination of catalytic kinetics and catalyst durability.