Alexey L. Nuzhdin

Hydrodeoxygenation of methyl palmitate over sulfided Mo/Al2O3, CoMo/Al2O3 and NiMo/Al2O3 catalysts

The catalytic properties of sulfided Mo/Al2O3, CoMo/Al2O3 and NiMo/Al2O3 catalysts in the hydrodeoxygenation of methyl palmitate as a model compound for triglyceride feedstock were studied at 300 °C and 3.5 MPa in the batch reactor using n-tetradecane, m-xylene and hydrotreated straight-run gas oil (HT-SRGO). The comparison of catalysts performance in n-tetradecane allowed us to see that the sulfided Mo/Al2O3, CoMo/Al2O3 and NiMo/Al2O3 catalysts revealed the same rate of the methyl palmitate conversion but the rate of the intermediate oxygenates conversion decreased in order: CoMoS/Al2O3 > NiMoS/Al2O3 > MoS2/Al2O3. A mixture of linear saturated and unsaturated C15 and C16 hydrocarbons was produced when the oxygenates were fully consumed. The main products obtained over the Mo/Al2O3 and CoMo/Al2O3 catalysts were C16 hydrocarbons (C16/C15 – 16.1 and 2.79, respectively); however, C15 hydrocarbons were preferentially formed over the NiMo/Al2O3 catalyst (C16/C15 – 0.65), highlighting the different contributions of the hydrodeoxygenation (HDO) and decarboxylation/decarbonylation (DeCOx) pathways during the hydroconversion of methyl palmitate over these catalysts. Investigating the solvents influence on the activity of the CoMo/Al2O3 and NiMo/Al2O3 catalysts in the methyl palmitate HDO revealed that the reaction rate was decreased in the following order: n-tetradecane > HT-SRGO > m-xylene. The aromatic compounds did not retard the methyl palmitate transformation, but inhibited the conversion of the intermediate oxygenates. Decreased C16/C15 ratios were observed over both catalysts when m-xylene was used as the reaction medium instead of n-tetradecane.

Catalytic properties of CoMo/Al2O3 sulfide catalysts in the hydrorefining of straight-run diesel fraction mixed with rapeseed oil

CoMo/Al2O3 sulfide catalysts varying in preparation method and Co/Mo ratio have been tested in the hydrorefining of a mixture of straight-run diesel fraction and rapeseed oil in a flow reactor at a temperature of 340–360°C, a hydrogen pressure of 4.0–7.0 MPa, and a liquid hourly space velocity of 1–2 h−1. A comparison between catalysts prepared using citric acid (CoMo/Al2O3-1.5) and both citric and orthophosphoric acids (CoMoP/Al2O3-1.5) as promoters, with Co/Mo = 0.3 and 0.5, has demonstrated that the most active catalyst in hydrodesulfurization and hydrodenitrogenation is the phosphorus-containing Co/Mo ≈ 0.5 sample. The addition of rapeseed oil to straight-run diesel fraction lowers the hydrodesulfurization and hydrodenitrogenation activities of the CoMo sulfide catalysts, irrespective of the method by which they were prepared. The fatty acid triglyceride conversion selectivity of these catalysts depends on the Co/Mo ratio and on reaction conditions: decreasing the Co/Mo ratio from 0.46 to 0.26, lowering the reaction temperature, and raising the hydrogen pressure and hydrogen-to-feedstock ratio increase the C18/C17 hydrocarbon ratio in the hydrogenated product. The addition of rapeseed oil improves the quality of the product; however, for attaining the preset residual sulfur level in this case, the process needs to be conducted at a higher temperature than the hydrorefining of straight-run diesel fraction containing no admixture.

Study of Catalyst Deactivation in Liquid-Phase Hydrogenation of 3-Nitrostyrene Over Au/Al2O3 Catalyst in Flow Reactor

For the first time, we report the results of the study of dynamics of the Au/Al2O3 catalyst deactivation during the selective liquid-phase 3-nitrostyrene (3-NS) hydrogenation in a fixed bed flow reactor. It is shown that the formation of carbonaceous deposits is the main reason of catalyst deactivation, while the leaching of gold from the Au/Al2O3 catalyst or enlargement of the gold particles has not been detected. The content of the carbon deposits on the spent catalyst at the inlet of the reactor is higher than at the outlet and increases as the initial concentration of 3-NS grows. The character of carbonaceous deposits allocation and analysis of reaction products point out to 3-vinylnitrosobenzene as the main source of the Au/Al2O3 catalyst deactivation coinciding with the speculation arising from the kinetic modeling.Graphical Abstract

Flow synthesis of secondary amines over Ag/Al2O3 catalyst by one-pot reductive amination of aldehydes with nitroarenes

An alumina-supported silver catalyst was investigated in the one-pot reductive amination of aldehydes with nitroarenes in a continuous flow reactor using molecular hydrogen as a reducing agent. A series of secondary amines containing alkyl, OH, OCH3, Cl, Br and CC groups was synthesized in good to excellent yields. The yield of the secondary amine depends on the rate of formation of an intermediate imine. It was shown that the accumulation of carbonaceous deposits on the catalyst is the main reason of catalyst deactivation. The spent catalyst can be easily regenerated and reused without losing catalytic activity.

Preparation of HKUST-1@silica aerogel composite for continuous flow catalysis

HKUST-1@silica aerogel composite pellets (HKUST-1@SiO2) were prepared by the coupled sol–gel and water-in-oil emulsion method using supercritical CO2 drying. The structure and morphology of HKUST-1@SiO2 were characterized by X-Ray diffraction, scanning electron microscopy and low-temperature nitrogen adsorption. According to these data, the composite represents physically dispersed micron-sized domains of HKUST-1 in the silica aerogel pellets. It was shown that the HKUST-1@SiO2 pellets can be used as a catalyst for isomerization of styrene oxide to phenyl acetaldehyde in a continuous flow reactor.Graphical abstract

Use of a Dual-Bed System for Producing Diesel Fuel from a Mixture of Straight-Run Diesel and Rapeseed Oil over Sulfide Catalysts

A dual-bed catalytic system including MoS2/Al2O3 and Co–MoS2/Al2O3 catalysts is proposed for the process of production of diesel fuel with the sulfur content of less than 10 ppm from a straight-run diesel fraction containing 10–45 wt % rapeseed oil. The conversion of rapeseed oil to alkanes proceeds in the MoS2/Al2O3 catalyst bed via the route of “direct” hydrodeoxygenation without the formation of carbon oxides, and the hydrodesulfurization of the diesel fraction occurs in the bed of the Co–MoS2/Al2O3 hydrotreating catalyst. Using this system provides an increase in the yield of diesel fuel and a decrease in the formation of greenhouse gases in comparison with conventional Co(Ni)–MoS2/Al2O3 catalysts.