Petroleum Chemistry (v.56, #3)
Triptane synthesis from methanol and dimethyl ether: A review by S. N. Khadzhiev; M. V. Magomedova; E. G. Peresypkina (181-196).
The review summarizes and analyzes the results of research in the field of triptane synthesis from methanol and dimethyl ether (DME). The reaction with a fairly high triptane yield occurs in the presence of both homogeneous and heterogeneous catalysts. It has been shown that InI3 and ZnI2 are the most commonly used catalysts for the homogeneous process, while zeolite systems based on H-BEA and H-Y are promising catalysts for the heterogeneous process. The effect of the catalyst nature (acidity and structure) on the type of resulting intermediates and the reaction mechanism has been described. Currently available approaches to describing the kinetics of the complex triptane synthesis reaction and the engineering aspects of the process have been discussed.
Keywords: high-octane component of motor fuel; triptane; triptene; mechanism of triptane synthesis from oxygenates; zinc and indium iodides; H-BEA and H-Y zeolite catalysts
New heterogeneous catalysts based on zeolites with hierarchical pore system by E. V. Parkhomchuk; K. A. Sashkina; V. N. Parmon (197-204).
The results of synthesis and packing of crystallized iron-containing nanosized zeolites of MFI structure in dense and loose structures having different textural properties are reported. Data on the formation of additional meso- and macropores immediately during zeolite crystallization using polystyrene microspheres in the form of an aqueous suspension (latex) and as a dry template of closely packed particles are also presented. Advantages and disadvantages of these procedures for preparing hierarchical iron-containing MFI structure zeolites have been compared. Values of the external surface area and the total pore volume of hierarchical Fe-silicalites are significantly higher than those for a reference sample. Using the polymer template to synthesize the hierarchical material consisting of zeolite nanocrystals makes it possible can significantly reduce the synthesis time and simplify the preparation procedure.
Keywords: iron-containing zeolites; synthesis; hierarchical pore system; micro-meso-macropores
Synthesis of N-methylaniline over molecular sieve catalysts by M. V. Belova; O. A. Ponomareva; I. I. Ivanova (205-210).
The preparation of N-methylaniline in two various processes: alkylation of aniline with methanol and hydroalkylation of nitrobenzene with methanol has been studied. Bifunctional molecular sieves containing metal copper as the hydrogenating component and zeolites BEA, MOR, MFI, FAU (Y) and mesoporous material MCM-41 as an alkylating component were used as catalysts. It has been shown that the modification of samples with copper nitrate increases the number of Lewis acid sites and decreases the number of Brønsted acid sites as copper embeds into cation exchange positions. It has been determined that the catalyst modification with copper increases the activity and enhances the selectivity towards N-alkylated products.
Keywords: aniline; nitrobenzene; methanol; N-methylaniline; alkylation; hydroalkylation; zeolites; molecular sieves
Composite catalysts for selective catalytic reduction of NO x and oxidation of residual NH3 by A. I. Mytareva; D. A. Bokarev; G. N. Baeva; D. S. Krivoruchenko; A. Yu. Belyankin; A. Yu. Stakheev (211-216).
A comprehensive study has been performed on the catalytic properties of composite catalysts [Mn/support + FeBeta] and their individual components (Mn/support and FeBeta) in the selective catalytic reduction of nitrogen oxides and the ammonia oxidation reaction. It has been shown that mixing the oxide component with the zeolite not only leads to an increase in NO x conversion, but also improves the selectivity in the oxidation of residual ammonia, thus making it possible to conduct both processes in a single catalytic unit.
Keywords: MnO x ; FeBeta; N x ; selective catalytic reduction; ammonia oxidation
Methanol to olefins conversion over silicoaluminophosphates with AEI structure: Effect of the active site type by V. I. Kasnerik; S. V. Konnov; I. V. Dobryakova; A. O. Ivanov; E. E. Knyazeva; I. I. Ivanova (217-223).
Effect of the type of active site on the catalytic properties of microporous crystalline silicoaluminophosphates with AEI structure synthesized at 150, 170, and 190°C has been investigated. The state of the active site was changed by varying the catalyst synthesis conditions. It has been established that during the synthesis of silicoaluminophosphates with the AEI structure from the reaction mixture of the same composition, an increase in the temperature and crystallization time leads to an increase of the silicon content and crystal size growth. The observed changes in the physicochemical properties are accompanied by the change of the silicon state in the structure of silicoaluminophosphates with the predominant formation of silicon “islands” via the SM3 mechanism. According to 29Si NMR data, the formation of active sites of silicoaluminophosphates via the SM2 mechanism in the form of isolated silicon atoms in the structure is also observed for these materials. The presence of such sites, along with the morphological features of the crystals, determines the unusual catalytic properties of silicoaluminophosphate with AEI structure in MTO process, which are a high ethylene yield up to 41 wt % at an ethylene: propylene molar ratio of 1: 6.
Keywords: silicoaluminophosphates; morphological features; acid properties; type of active site; conversion of methanol into olefins
Production of aviation fuel by bioethanol conversion on zeolite catalysts by V. F. Tret’yakov; R. M. Talyshinskii; A. M. Ilolov; A. D. Budnyak (224-229).
The catalytic process of two-stage conversion of ethanol into jet fuel, wherein the second step is the hydrogenation of aromatic hydrocarbons obtained in the first step, has been studied. It has been shown that at 400°C and an ethanol space velocity of LHSV = 2 h–1, aromatic hydrocarbons are produced, which are hydrogenated on a Pt/C catalyst in an autoclave at 80–100 atm and T = 200–250°C for 1.5 h with a final yield of naphthenic hydrocarbons on a fed ethanol basis of 15–20%.
Keywords: alternative energy; environmental protection; ethanol; jet fuel; green biomass
Dehydration of 2,3-butanediol over zeolite catalysts by M. A. Nikitina; V. L. Sushkevich; I. I. Ivanova (230-236).
2,3-Butanediol as a product of biomass processing is a cheap alternative raw material for synthesis of methyl ethyl ketone (MEK) and butadiene-1,3. The catalytic activity of Al- and Zr-containing BEA zeolites and an alumina-based catalyst in 2,3-butanediol dehydration has been investigated. It has been shown that the presence of Brönsted (H-BEA) or Lewis (Al2O3) sites leads to the selective formation of MEK and the combination of two types of sites (Zr-BEA) facilitates the formation of heavy products of condensation.
Keywords: 2,3-butanediol; butadiene; methyl ethyl ketone; zeolites; Zr-BEA; Lewis sites; Brönsted sites
A ZSM-5 zeolite-based catalyst for oligomerization of the butane–butylene fraction by A. G. Popov; D. A. Fedosov; I. I. Ivanova; O. S. Vedernikov; A. V. Kleimenov; D. O. Kondrashev; V. D. Miroshkina; P. A. Abrashenkov; S. E. Kuznetsov (237-243).
The effect of localization of acid sites and the nature of the modifier metal on the activity, selectivity, and operation stability of a ZSM-5 zeolite-based catalyst in the oligomerization of the butane–butylene fraction (BBF) has been examined. It has been shown that the selective poisoning of acid sites on the external surface of zeolite crystals reduces coking and increases the yield of the desired gasoline fraction. Introduction of a promoter metal insignificantly affects the catalytic properties of the zeolite. Among Zn, Ga, and La, gallium appears to be the best modifier, which provides an increase in the yield of the desired gasoline fraction by 0.9%. As a result of the study, a BBF oligomerization catalyst has been developed that ensures a threefold increase in the catalyst on-stream time and a 7% increase in the yield of the gasoline fraction as compared with its commercial counterpart.
Keywords: oligomerization; butane–butene fraction; zeolite catalysts; modification of catalysts
Effect of the type of silicon source on the physicochemical and catalytic properties of mesoporous silicoaluminophosphate molecular sieves by G. V. Echevsky; Qi Weixing; A. V. Toktarev; W. Wei (244-252).
Silicoaluminophosphates with the ATO structure have been synthesized using two types of silicon source (metakaolin and silica sol). To determine the composition, morphology, and acid properties, SAPO-31 samples have been characterized by various methods. It has been found that the samples synthesized using different silica sources have very different properties. Samples of SAPO-31 synthesized with metakaolin have a higher acidity and are more active in the catalytic hydroisomerization of n-decane as compared with their counterparts prepared with silica sol. The difference in the effect of the type of silicon source has been explained by morphological features of silica particles formed during the dissolution of silicon source (spherical particles of a ~10 nm size in the case of silica sol and nanoplates of a ~1 nm size in the case of metakaolin). On the basis of data on the enhancement of acidic properties in the SAPO-31 samples with an increase in silicon concentration therein, it has been doubted that the SM3 mechanism of incorporation of Si atoms into the aluminophosphate ATO framework really operates (in any of its form). It has been shown that the SM2 mechanism alone operates instead, involving the independent formation of regions with an aluminosilicate composition.
Keywords: silicoaluminophosphates; SAPO-31; mechanism of incorporation of isomorphically substituting elements
Production of isobutylene from acetone over micro–mesoporous catalysts by O. A. Ponomareva; A. A. Mal’tseva; A. A. Maerle; L. I. Rodionova; V. S. Pavlov; I. V. Dobryakova; M. V. Belova; I. I. Ivanova (253-258).
The production of isobutylene from acetone over micro–mesoporous catalysts with different mesopore contents, which have been prepared using hydrothermal recrystallization of mordenite (MOR) zeolite modified with cesium acetate by incipient wetness impregnation, has been studied. It has been shown that cesium is inserted into the cation positions during the modification, at the same time the number of Brønsted acid sites in the samples decreased. It has been found that an increase in the content of mesopores in the catalyst leads to an increase in the initial rates of acetone conversion and isobutylene formation as a result of removing diffusion limitations. Brønsted acid sites have been shown to be preferable for the selective production of isobutylene from acetone. Micro–mesoporous materials operate more stably as compared to microporous materials.
Keywords: acetone; isobutylene; micro–mesoporous catalysts; cesium; mordenite
Theoretical aspects of methanol carbonylation on copper-containing zeolites by A. A. Rybakov; I. A. Bryukhanov; A. V. Larin; G. M. Zhidomirov (259-266).
The experimental data have been considered to match the theoretical mechanisms proposed previously to describe processes of oxidative carbonylation of methanol on copper-containing catalysts. The schemes examined cover methoxy intermediates, carbomethoxy intermediates, carbonates, and Cu(OCH3)2Cu binuclear clusters. The attack of the first methanol molecule on copper carbonate has been simulated in terms of the isolated cluster (8R) model with periodic boundary conditions (on CuMOR zeolite), and parameters of the individual steps involving description of the transition states have been evaluated.
Keywords: methanol carbonylation; carbonates; zeolites; copper-containing catalysts; DFT
Formation of active sites in titanium-containing zeolites with MFI structure in propylene epoxidation with hydrogen peroxide by I. A. Tyablikov; L. I. Rodionova; P. D. Sobolev; I. I. Ivanova (267-274).
Propylene epoxidation with hydrogen peroxide on titanosilicates with different Si/Ti ratios and various states of titanium in the catalysts, prepared by hydrothermal crystallization according to two different procedures, has been investigated. It has been demonstrated that a change in the pH of the crystallizing gel leads to a change in the sequence of titanium insertion in the zeolite structure at a hydrothermal synthesis temperature of 170°C. It was shown that titanium incorporated in the zeolite framework in the tetrahedral positions is an active site in the epoxidation reaction, whereas titanium in the form of titanium dioxide leads to unproductive degradation of hydrogen peroxide.
Keywords: epoxidation of propylene; propylene oxide; titanosilicate TS-1; active site
Fischer–Tropsch synthesis with cobalt catalyst and zeolite multibed arrangement by E. Yu. Asalieva; E. V. Kul’chakovskaya; L. V. Sineva; V. Z. Mordkovich; B. M. Bulychev (275-280).
The role of zeolite in transformations of hydrocarbons produced from CO and H2 over a Fischer–Tropsch cobalt catalyst under the conditions of multibed arrangement of the cobalt catalyst and the zeolite has been determined. Hydrocarbon conversion over the HBeta zeolite occurs via the bimolecular mechanism, as evidenced by a low methane yield and a high yield of unsaturated gaseous and liquid hydrocarbons. The conversion over the CaA zeolite obeys the unimolecular mechanism, as evidenced by the formation of increased amounts of methane and saturated gaseous C2–C4 hydrocarbons.
Keywords: Fischer–Tropsch synthesis; cobalt catalyst; zeolite; skeletal cobalt