Catalysis in Industry最新文献

Cyclooctene and alkylbenzenes are subjected to co-oxidation in oxygen and a system of two catalysts. Radical catalyst Fe(acac)₃/NHPI mediates the formation of alkylbenzene hydroperoxides, which are consumed in situ during the MoO₃/SiO₂-catalyzed epoxidation of cyclooctene. The chain oxidation rate is limited in cyclooctene and MoO₃/SiO₂, but radical catalyst Fe(acac)₃/NHPI retains fairly high activity in the oxidation of alkylbenzene in hydroperoxide. It is found that isopropylbenzene is a better co-reducing agent than ethylbenzene because it ensures more vigorous and selective formation of epoxycyclooctane. At optimized amounts of components and a temperature of 80°C, selectivity toward epoxycyclooctane reaches 92 and 96% in ethylbenzene or isopropylbenzene, respectively, with more than 70% conversion of cyclooctene.

In this paper, high-loaded copper-containing catalysts synthesized by the different methods (sol–gel, fusion, coprecipitation) have been studied in furfural hydroconversion in a batch reactor at a hydrogen pressure of 5.0 MPa and a temperature of 100°C. The reduction temperatures and phase composition of the catalysts have been determined by physicochemical methods. It has been shown that the highest activity in the studied process is exhibited by a coprecipitated copper–alumina catalyst, which provides the production of furfuryl alcohol with a selectivity of 100% at 100–130°C; in addition, in the presence of this catalyst, 2-methylfuran can be synthesized with a yield of 65% at 200°C. The phase composition of the catalyst reduced at a selected temperature and the catalyst after reaction has been determined.

The review addresses the main approaches used in the thermochemical and catalytic conversion of microalgae biomass (hydrothermal liquefaction, gasification, transesterification, pyrolysis) to produce biofuels. The key conditions that determine the reaction product yield using bio-oil production catalysts and approaches to bio-oil refining are discussed. It is shown that the use of bifunctional acid–base catalysts is most relevant for transesterification processes. The gasification and pyrolysis processes are used less frequently, because the former is accompanied by the formation of CO₂, and the latter is characterized by the formation of a large amount of oxidized compounds that deteriorate the quality of bio-oil.

The paper provides a review of reports in the field of microalgae biomass conversion to various types of biofuels (fatty acid methyl esters, ethanol, butanol, hydrogen) and marketable chemicals, in particular, polyunsaturated fatty acids, pigments, and proteins, using modern chemical and biotechnological approaches. This review addresses the synthesis of products using various strategies applied to develop modern approaches to the integrated biorefinery of microalgae biomass.

Exhaustive enzymatic hydrolysis is performed for semi-bleached sulfate hardwood cellulose (a semi-finished pulp and paper product) at ultra-high concentrations of it in a reaction mixture (up to 300 g/L per dry compound). Russian commercial enzyme preparations are used for hydrolysis. The best seems to be Agroxil Plus, which has high cellulase and endoxylanase activities. A total of 290 g/L of sugars (including 210 g/L of glucose and 30 g/L of xylose) is obtained using Agroxil Plus (20 mg protein/1 g substrate) in combination with an auxiliary β-glucosidase enzyme preparation (2 mg protein/1 g substrate) at an initial semi-bleached cellulose concentration of 300 g/L. The dosage of Agroxil Plus can be halved (10 mg of protein/1 g of substrate with a total concentration of semi-bleached cellulose of 300 g/L) with a high yield of hydrolysis product (270 g/L of sugars, including 200 g/L of glucose and 30 g/L of xylose), due to the fractional addition of a substrate.

Results of studying ethanol conversion to aromatic hydrocarbons (benzene, toluene, xylenes) that are currently available in the scientific literature are discussed and systematized. The features of ethanol conversion in the presence of zeolite catalysts and the mechanism of each individual stage of ethanol conversion to aromatic hydrocarbons are discussed. The effect of the zeolite catalyst composition, the feedstock composition, and ethanol conversion process conditions is demonstrated. The effect of the modifier of a zeolite catalyst on the aromatic hydrocarbon selectivity is shown. This review can be of interest and of use to researchers of zeolite catalyst systems and alcohol conversion processes.

Under slurry reactor conditions, the products of condensation are generrally formed on strong Mg/HZSM-5 acid sites independently of the SiO₂/Al₂O₃ molar ratio in the zeolite. The composition of condensation products remains virtually unchanged as the molar ratio grows and basically consists of trimethyl and tetramethyl benzenes, but their content falls as the volume of mesopores grows with increasing SiO₂/Al₂O₃. This lowers the hindrances to diffusion and the contribution from secondary reactions to improve the removal of coke precursors from the zeolite’s surface and favorably affect the catalyst’s activity (DME conversion doubles). The composition of reaction products changes slightly with an increase in the SiO₂/Al₂O₃ molar ratio, and the total selectivity toward lower olefins is ~70 wt %. A rapid loss in Mg/HZSM-5 activity upon extending the period of operation under slurry reactor conditions is not due to coking, but to the catalyst being clogged by dispersion medium (polydimethylsiloxane) decomposition products.

Adapting domestic commercial catalysts for use in such important technological processes as the environmentally friendly production of hydrogen accompanied by СО_х and NО_х emissions is in demand under import substitution conditions. Ammonia seems to be the most promising Н₂ accumulator, due to its high hydrogen density and simple storage and transportation. This work considers the possibility of using the domestic NIAP-03-01, NIAP-07-01, NIAP-06-06 catalysts and Со-Al₂O₃/SiO₂ developed by the authors in the ammonia dissociation reaction. The conversion and hydrogen production capacity grow in the order NIAP-06-06<NIAP-03-01<NIAP-07-01<Со-Al₂O₃/SiO₂. The conversion of ammonia on Со-Al₂O₃/SiO₂ is close to 100% at 550°C and a gas hourly space velocity (GHSV) of 3000 h⁻¹. The effective activation energies of all the catalysts are comparable to the available literature data for the ammonia decomposition reaction to potentially enable their application at moderate temperatures.

The paper provides a review of reports on the results of studies in the field of microalgae biomass cultivation and conversion to marketable chemicals using modern bioengineering approaches. The review discusses approaches to producing biofuels (biodiesel, ethanol, hydrogen) from microalgae. Data on biomass pretreatment methods and various procedures for isolating metabolites and converting them to biofuels are provided.

The aim of this review is to summarize and comparatively analyze recent reports on studying carbon dioxide conversion to methanol, dimethyl ether, and C₂₊ hydrocarbons, in particular, olefins, by catalytic hydrogenation. It is shown that the main approaches to providing high activity and selectivity of these processes are the targeted design of catalysts and the selection of conditions for hydrogenation processes, in particular, the use of supercritical CO₂ and procedures that are alternative to conventional physicochemical methods for CO₂ activation (electrocatalysis, photocatalysis).