GENERAL PROBLEMS OF CATALYSIS
The paper considers the main methods used to obtain aluminum oxides; the advantages of using hydrargillite thermal activation products for the synthesis of catalysts, supports and sorbents; the factors affecting the properties of thermal activation products and aluminum oxides obtained by thermal activation; and examples of the efficient application of hydrargillite centrifugal thermal activation products in the synthesis of catalysts, supports and sorbents.
CATALYSIS IN CHEMICAL AND PETROCHEMICAL INDUSTRY
This is the third concluding part of a series of reviews devoted to the direct synthesis of organotin compounds. This review considers conditions and results of the interaction between metallic tin and carbofunctional organohalogenides. Efficiency of the catalysts application and advantages of the direct synthesis for the production of carbofunctional organotin compounds are analyzed.
The synthesis of glycerol carbonate from glycerol and dimethyl carbonate in the presence of strongly basic styrene-divinylbenzene anionites Dowex 1×2, Dowex 1×4 and Dowex 1×8 in the –OH form with different cross-linking degree of polystyrene matrix (the divinylbenzene content of 2, 4 and 8 wt.%) at 90–105 °C and a dimethyl carbonate/glycerol molar ratio equal to 2 was studied. The yield of glycerol carbonate was shown to decrease with an increase in the cross-linking degree of the anion-exchange resin. The maximum conversion of glycerol (95 %) and selectivity to glycerol carbonate (45.5 %) were observed in the presence of Dowex 1×2 at 105 °C after 5 h of the reaction. Advantages of the studied systems were demonstrated in comparison with the anion-exchange and cationexchange resins proposed in the literature.
The possibility to use the zinc-copper catalyst NIAP-06-06 for steam conversion of CO in the synthesis of methanol was explored. The catalyst was characterized by means of TPR H2, XRD and SEM methods and tested in the methanol synthesis in flow and circulation modes at a pressure of 5.0 MPa and gas hourly space velocity of 3000 h–1 over a temperature range of 220–260 °С. The catalyst was shown to be highly active and selective toward the methanol synthesis from a gas with the H2 /СО ratio 3.9, which is obtained by steam conversion of methane. The use of tubular catalytic reactors connected in series in the flow-circulation mode makes it possible to convert more than 70 % of CO and obtain crude methanol with the concentration of 95 %. In the circulation mode, a methanol output of 427.7 kg/(m3 cat·h) was achieved on the catalyst.
Ni catalysts with the carbon-mineral supports obtained from sapropel were synthesized and studied in the catalytic hydroliquefaction of sapropel. It was found that catalysts with the supports obtained from mineral sapropel are more active as compared to those based on organic sapropel; therewith, bimetallic NiW catalysts showed a higher activity than monometallic nickel, irrespective of the support nature. The conversion of the organic matter of sapropel and the composition of liquid products are affected by both the features of supported metal and the composition of support. The liquid products of hydroliquefaction contain mostly the nitrogen- and oxygen-containing compounds. The maximum yield of С5-С21 hydrocarbons is achieved for the catalysts with the supports obtained from mineral sapropel. The composition of the liquid products of sapropel hydroliquefaction is similar to that of biofuels obtained from other renewable sources; such products can be introduced in the known schemes of further processing.
BIOCATALYSIS
Nowadays, Sugar esters (SEs) have become the focus of researchers due to their biocompatibility and extensive industrial applications as surfactants. This trend provides new methods and opportunities for the development of green synthetic chemistry. Taking the above into consideration, a critical review presented in this work emphasized the efficiency of catalyzing the synthesis of SEs with minimal hazardous by-products. These catalytic media have been employed with various impacts involving chemical, biological, and other catalytic materials. Chemical methods have been reported to show limitations in terms of preparation and bio-compatibility. To solve these shortcomings, therefore, other technologies have been adopted; ionic liquids (eutectic solvents), chemo-enzymatic systems and chemo-enzymatic systems on a catalytic surface. The use of chemo-enzymatic systems on catalytic surfaces has proved to be suitable in solving biocompatibility and stability problems and correspondingly increasing the yield of esters formed. Therefore, finding an improved catalytic surface, and the sustainable optimal reaction conditions for enzymes will be vital to improving sugar ester conversion. This study highlights the different catalytic advances employed in the esterification of SEs.
The review discusses the results of recent studies in the promising field of integrated processing of lignocellulosic biomass – the reductive catalytic fractionation (RCF). The effect of catalysts, cocatalysts, solvents, hydrogen sources and features of lignocellulosic feedstock on the selectivity of monomeric products formation from lignin is considered. RCF processes are performed mostly with the heterogeneous catalysts, which allow implementing the reductive depolymerization of lignin to obtain low-molecular compounds and preserve carbohydrate components of biomass. Among the studied catalysts based on platinum group metals and transition metals, the highest activity is observed for the catalysts containing Pd, Pt, Ru and Ni. Features of the metal also affect the composition of the resulting products. Thus, ruthenium catalysts make it possible to obtain 4-propylguaiacol as the main product, while Ni and Pd – 4-propanolguaiacol. Mo-containing catalysts, owing to their lower hydrogenating activity, can be used to obtain monolignols or their etherified derivatives with the preservation of carbohydrate components of lignocellulosic biomass. However, most efficient in RCF processes are the bifunctional catalysts, which have both the acidic and metallic active sites. Acidic sites promote the cleavage of the ether β-O-4 bonds, whereas metallic sites – the reduction of the formed intermediate compounds. An important aspect of choosing the appropriate catalysts for RCF process is the possibility of their repeated application. The use of a ferromagnetic catalyst or a catalyst basket allows separating the catalyst from the products.
INFORMATION
ISSN 2413-6476 (Online)