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.
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.
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.
Adapting domestic commercial catalysts for use in such important technological processes as the environmentally friendly production of hydrogen accompanied by СОх and NОх 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.
An adsorbent consisting of a granular NаX zeolite with a hierarchical porous structure and a high degree of crystallinity and phase purity is used for the efficient drying and purification of natural and associated gases from H2S. The possibility of using KZhV, MP KAKh, KCh-2, and KR-2 kaolins produced in Russia as temporary binder materials during its production is studied. It is found that KZhV and MP KAKh kaolins do not require additional treatment to prepare such an adsorbent. KCh-2 and KR-2 kaolins require additional dispersion.
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).
The effect of the content of metallic (Co–Al2O3/SiO2 catalyst) and acidic components (ZSM-5 zeolite in H-form) on the properties of a bifunctional catalyst for the integrated synthesis of low-pour-point diesel fuel by the Fischer–Tropsch method has been studied. The catalysts in the form of a composite mixture with a binder (boehmite) have been characterized by XRD, BET, and TPR methods. The tests are conducted in a fixed-bed flow reactor at a pressure of 2.0 MPa, a temperature of 240°C, and a gas space velocity of 1000 h–1. The activity and selectivity of catalysts and the fractional and hydrocarbon compositions of products as a function of the ratio of components have been compared. It has been found that the synthesis productivity with respect to С5+ hydrocarbons and selectivity to products of the С11–C18 diesel fraction with a high content of isomeric products correlate with the ratio of metallic and acidic components in the catalyst composition. The catalyst recommended for use in diesel fuel production has a composition with a ratio of metallic and acidic components of 1.17.
A way of hydrodebrominating 2,3,4,5-tetrabromothiophene (1) to 3,4-dibromothiophene (2) on a 5% Pd/Sibunit catalyst is proposed. The effect of solvent, alkaline agent, temperature, and concentration of 1 on the yield of 2 is studied. The optimum conditions are catalyst : substrate mass ratio, 1:10; temperature, 80°С; H2 pressure, 0.7 MPa; solvent, dimethylformamide; alkaline agent, triethylamine in amounts of 2.2 mol per 1 mol of substrate 1. The yield of 2 is 97.5% in this case. The catalyst can be reused in at least 15 cycles with high yields of 2. The new approach appears to be highly productive with little waste, compared to the conventional chemical reduction of 1 with zinc in CH3COOH.
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