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Bifunctional palladium-based catalysts with zeolite supports were investigated in phenol hydroalkylation, representing high-potential model reaction for transformation of lignocellulose-derived compounds to automotive and jet fuels. Conversion of phenol correlated with the amount of accessible acid sites and textural properties of the solid acid support: under the same reaction conditions and at the same Pd loading. The highest phenol conversions (99–100%) were obtained for large-pore zeolite Beta and mesopore-containing MCM-36/56 materials. The selectivity towards the targeted cyclohexylcyclohexane on different supports decreased in the following order Beta (57%) > MCM-36 (42%) ≈ MCM-56 (37%) > MCM-22 (20%), while the contribution of undesired reaction termination through formation of non-reactive cyclohexane was more pronounced for the expanded MCM-36/56 based catalysts. Substrate consumption after 60 min over the least active MCM-22-based catalysts increased with increasing Pd content as follows 27% (0.3 wt % Pd), 80% (0.5 wt % Pd) and 98% (0.7 wt % Pd). High activity of Pd/Beta catalysts was not vitiated even by sintering effects being the most pronounced for Beta as a support. [ABSTRACT FROM AUTHOR]

Sulfur-free Mo carbide catalysts supported on Al 2 O 3 and TiO 2 have shown good activity during the co-processing of middle distillates with vegetable oils in prior studies. However, their hydrotreating activity is low compared with that of conventional hydrotreating catalysts. To increase the hydrotreating effectiveness, promoter metals, such as Ni or Co, can be added. This paper describes an extensive study on the use of four sulfur-free Ni-Mo and Co-Mo carbide catalysts (supported on Al 2 O 3 and TiO 2) for the hydrotreatment of atmospheric gasoil (AGO) and co-processing with rapeseed oil (RSO). The tests were conducted in a fixed bed reactor unit at 330–350 °C, 5.5 MPa, a weigh hourly space velocity (WHSV) = 1–2 h−1, and AGO/RSO of 100/0, 95/5, 90/10, and 75/25 wt.%. Analogous to conventional hydrotreatment catalysts, adding the promotor metals significantly increased the product quality and the hydrodesulfurisation and hydrodenitrogenation efficiencies at higher temperatures or at lower WHSVs. In the case of RSO co-processing, all the tested catalysts promoted the hydrodeoxygenation pathway instead of (hydro)decarboxylation/decarbonylation with an insignificant decrease in the hydrodesulfurization efficiency at lower AGO/RSO ratios. Therefore, our results suggest that promoting Mo carbide catalysts with Ni or Co significantly improves their catalytic properties, making them more competitive with conventional hydrotreating catalysts. [ABSTRACT FROM AUTHOR]

Generally, the commercial catalysts for hydrotreatment in refineries are supported sulfide transition-metal-based catalysts. However, the co-processing of vegetable oils reduces their hydrodesulfurization (HDS) efficiency by leaching sulfur from the active sites of the catalyst. The present work reports the use of six sulfur-free MoCx and MoNx catalysts (supporter with Al 2 O 3 , TiO 2 or ZrO 2) for the hydrotreatment of atmospheric gasoil (AGO) and co-processing of rapeseed oil (RSO – 5, 10 and 25 wt%). The screening tests were carried out in a fixed bed reactor at industrial operating conditions (330–350 °C, 5.5 MPa, WHSV = 1–2 h−1). Higher reaction temperatures and lower WHSV had a positive effect on catalyst activity and product quality. In case of co-processing, the hydrodeoxygenation reaction mechanism was found to be dominant, producing n-C 16 and n-C 18 n-alkanes at all AGO/RSO ratios used. Overall, our results suggest that alumina supported catalysts are the most promising materials, exhibiting a combination of excellent stability, high activity and no negative effects on HDS efficiency during AGO/RSO co-processing. [ABSTRACT FROM AUTHOR]