The studies were focused on changes in the structure, texture and acid properties of the Mg-HZSM-5/Al2O3catalyst upon its treatment at different temperatures (400 and 500 °С) and times (6 and 12 h). Physicochemical techniques such as X-ray fluorescence analysis, XPS, solid-state27Al NMR, nitrogen adsorption, DRIFT spectroscopy, ammonia TPD were used for sample characterization. The catalytic activitites of the initial and treated samples were studied regarding conversion of dimethyl ether (DME) to lower olefins. It was shown that the initial activity of the Mg-containing zeolite catalyst was dependent of the total acidity of the surface and independent of the initial strength distribution of the acid sites, and the catalyst stability depended on the morphology.

Gasoline has been synthesized from oxygenates (dimethyl ether and methanol) on a HZSM-5 zeolite catalyst, modified by palladium and zinc, in a micropilot unit operating in the continuous recycle flow mode. The influence of the gas atmosphere composition—synthesis gas, hydrogen, and methane—on the gasoline selectivity, and on-stream stability of the catalyst has been determined for dimethyl ether (DME) used as a feedstock. The hydrocarbon composition and the carbon distribution in the products have been compared using DME and methanol as the feedstock in the synthesis-gas atmosphere. It has been shown that the higher gasoline selectivity production in the case of methanol is due to the higher concentration of aromatic hydrocarbons, which is achieved by decreasing the intensity of their dealkylation.

Systematic studies of olefin synthesis from dimethyl ether (DME) in the presence of a hydrothermally treated HZSM-5 zeolite catalyst modified with magnesium have been conducted. Dependences of DME conversion, product yield and selectivity, and lower olefin ratio on space time in the temperature range of 320–360°C have been analyzed. The type of the resulting products has been determined, and assumptions about the reaction chemistry have been made to reveal the role of methylation and hydrogen-transfer reactions in the products formation.

The known hydrocarbon synthesis technologies from synthesis gas through methanol and/or dimethyl ether (DME), which were implemented in different scales plants are analyzed. Common features, advantages, and disadvantages of each technology have been noted. Several designs of TIPS RAS GTL-technology based on the original DME single-step and gasoline catalysts have been calculated and the influence of the syngas composition on the gasoline specific yield for the optimal design has been studied.

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.

Comparative data obtained by studying the synthesis of С5+ hydrocarbons from dimethyl ether (DME) on catalysts using MFI zeolites available from different manufacturers are presented. It has been shown that MFI zeolite samples substantially differ in their acidic properties and structural, morphological, and textural characteristics. The catalysts based on different MFI zeolites also noticeable differ in the yield and chemical composition of С5+ hydrocarbons. By switching from the stand-alone operation of a DME conversion reactor to the joint operation of two reactors for synthesis of oxygenates (DME and/or methanol) from synthesis gas and synthesis of hydrocarbons from oxygenates connected by a single circuit, high selectivity for hydrocarbons of the gasoline fraction is achieved with the catalyst based on the MFI zeolite, for which the bands characteristic of Н3О+ acid sites are observed in diffuse reflectance IR spectra.

В обзоре представлены различные подходы к описанию кинетики реакции и синтеза олефинов из метанола/диметилового эфира для двух типов цеолитных катализаторов – ZSM-5 и SAPO-34. Показано, что наряду с феноменологическими моделями в настоящее время активно используются и микрокинетические модели, разработанные с учетом детального механизма реакции, и квантово-химические расчеты, основанные на теории активных соударений и теории активированного комплекса. Для описания скоростей элементарных стадий предлагаются как степенные зависимости, так и выражения типа Хоугена–Уотсона.

The review summarizes various approaches to the description of the olefins synthesis kinetics from methanol/dimethyl ether for two types of zeolite catalyst, ZSM-5 and SAPO-34. It has been shown that along with phenomenological models, microkinetic models derived with taking account of the detailed reaction mechanism and quantum-chemical calculations based on the single-event concept of the reaction rate and the transition state theory are being widely used now. Both power laws and the Hougen—Watson equations are proposed to describe the rates of elementary steps.

This review presents various first C-C bond and lower olefins formation mechanisms during the conversion of methanol or dimethyl ether (DME) over zeolite catalysts. The reaction is commonly described using both consecutive and parallel mechanisms. In terms of the first one concept, the oxonium ylide, carbene, carbocationic, methane-formaldehyde, and free radical mechanisms are analyzed. The parallel formation of the C-C bond is represented as the “hydrocarbon pool” mechanism which assumes the reaction occurs through alkene and arene cycles. It is shown that in the case of the arene cycle, olefins can be formed owing to the side chain growth of polymethylbenzenes (the so-called side-chain mechanism) or owing to the number of carbon atoms decrease in the aromatic ring (paring mechanism). Along with the isomerization and synchronous mechanisms wich assume that the route of the process substantially determined by the temperature range and the catalysts properties are discussed.

В обзоре рассмотрены различные типы механизмов образования первой С–С-связи, а также низших олефинов в процессе конверсии метанола и диметилового эфира (ДМЭ) на цеолитных катализаторах. Для описания реакции широко используется как последовательный, так и параллельный механизмы. В рамках представлений о последовательном образовании С–С-связи проведен анализ оксоний-илидного, карбенового, карбокатионного, метан-формальдегидного и свободно-радикального механизмов. Параллельное образование С–С-связи представлено в виде механизма “hydrocarbon pool” и показано, что реакция протекает по алкеновому и ареновому циклам. Показано, что для аренового цикла образование олефинов может протекать за счет роста боковой цепи полиметилбензолов (так называемый side chain-механизм) или за счет уменьшения числа углеродных атомов в составе ароматического кольца – paring-механизм. Наряду с указанными, рассмотрены изомеризационный и синхронный механизмы, согласно которым протекание процесса по тому или иному маршруту в значительной степени определяется температурным интервалом проведения процесса и свойствами катализатора.