Petroleum Chemistry (v.49, #1)

Toughening the quality standards for petroleum fuels suggests a substantial reduction in the amount of aromatic hydrocarbons in these fuels; in particular, the benzene content should not exceed 1.0%. Securing these requirements by legislation forces oil refiners to revise the hydrocarbon-group composition of motor gasolines and, hence, the engineering basis of their manufacture. The main world tendency for the hydrocarbongroup composition of motor gasoline is to increase the proportion of isoparaffins from 20 to 45%, which is equivalent to a reduction in the amount of aromatic hydrocarbons from 42 to 25%. The designing of a new industrial process for isobutane alkylation with olefins and the discovery of the new reaction of reductive dehydration of alcohols yielding isoparaffinic and, in particular, alkylcyclopentane hydrocarbons contribute to the production of alternative, environmentally safe motor fuels.

MCM-41 molecular sieves modified with γ-aminopropyltriethoxysilane, as well as an imidazole ionic liquid with palladium chloride, exhibit high activity in the liquid-phase Knoevenagel and Heck reactions.

By means of IR diffuse reflectance spectroscopy, it was shown that aromatization of light paraffins on the GaZSM-5 and ZnZSM-5 catalysts occurs through different routes. The first step of transformation on GaZSM-5 is the oxidative addition of paraffin molecules to Ga+ ions resulting in homolytic dissociation and the appearance of particles [H-Ga-R]+, whereas dehydrogenation on zinc-containing high-silica zeolites results from heterolytic dissociative adsorption on acid-base pairs yielding Brönsted acid centers and alkyl groups bonded to zinc. The subsequent degradation of the alkyl fragments leads to the formation of zinc hydrides or gallium dihydrides and olefins. The oligimerization of olefins in the case of ZnZSM-5 can occur on both acidic hydroxyl groups produced via paraffin dissociation and on the Zn2+ cations per se already at ambient temperature. In the case of GaZSM-5, the appearance of Brönsted sites in the catalyst is achieved via incomplete replacement of OH groups with gallium cations.

Dimerization of vinylarenes on zeolite catalysts by N. G. Grigor’eva; R. R. Talipova; A. N. Khazipova; S. V. Bubennov; B. I. Kutepov; U. M. Dzhemilev (16-22).
The main features of dimerization of vinylarenes, such as styrene, α-methylstyrene, β-methylstyrene, p-methylstyrene, p-methoxystyrene, p-methoxy-β-methylstyrene, m-chlorostyrene, and m-nitrostyrene used as an example, over zeolite catalysts were studied, and the high activity and selectivity of these catalysts in the reaction was shown. For styrene and α-methylstyrene, the vinylarenes having the largest production volume, catalysts that hold promise for industrial application were developed. Conditions for the selective linear dimerization (85–93%) and cyclodimerization (85–98%) of styrene and α-methylstyrene at a high conversion (100%) were determined.

Approaches to the structuring and functionalizing of molecular sieves by V. G. Il’in; A. V. Shvets; P. S. Yaremov; N. D. Lysenko; N. A. Yaroshenko; F. M. Bobonich (23-29).
On the basis of data available in the literature and the experimental results obtained by the authors, general developmental trends in studying the chemistry of microporous and mesoporous molecular sieves are discussed. The most important lines and objects of research were outlined, in particular, template synthesis of extra-large pore zeolites (silicates, germinates, phosphates, etc.) and mesoporous molecular sieves (MMS) of various types and compositions based on Si, Al, Ti, Zr, Ge, Sn, and some transition metal oxides and phosphates, as well as carbon MMS. Some of the current approaches and new ideas and approaches to the structuring and functionalizing of molecular sieves related to the chemistry of the template action; the specifics of isomorphism of the template action in phosphate and germanate zeolite-forming systems, as well as in MMS; the solubilization effect, etc. are considered.

The influence of the nature of anion X in the tetraethylammonium salt [N(C2H5)4]X on the selectivity of the formation zeolite beta in the SiO2-Al2O3-Na2O-[N(C2H5)4]X-H2O system under hydrothermal conditions without seed crystals was studied. It was shown that the test anions can be arranged in the following series in terms of the preferential formation of zeolite beta: F, SO 4 2− , PO 4 3− , (CH2COO) 2 2− > HCOO > (COO) 2 2− , CH3COO ≫ Cl ∼ NO 3 ≫ Br ≫ I ≫ ClO 4 . In particular, the fluoride and the anions of polybasic acids facilitate the formation of zeolite, whereas perchlorate, bromide, and iodide ions inhibit its formation. The experiments showed that anions facilitating the formation of zeolite beta make it possible to synthesize zeolite within the same broad range of chemical composition of the reaction mixture as in the case of [N(C2H5)4]OH. The reveled classification of anions into groups coincides with their categorization by Samoilov into anions with positive and negative hydration.

Binder-free syntheses of high-performance zeolites A and X from kaolin by M. L. Pavlov; O. S. Travkina; R. A. Basimova; I. N. Pavlova; B. I. Kutepov (36-41).
The crystallization behavior of metakaolin (Al2Si2O7) at 25–100°C in solutions of sodium hydroxide and sodium silicate with different concentrations was studied, and the conditions for its conversion into finely divided, high-crystallinity zeolites of types A and X were determined. On the basis of the product zeolites and kaolin, procedures were developed for the preparation of pelleted, binder-free materials as polycrystalline accretions of zeolites A and X, which do not rank below pelleted zeolites obtained from synthetic feedstock.

Conversion of dimethyl ether into C2-C4 olefins on zeolite catalysts by N. V. Kolesnichenko; O. V. Yashina; N. A. Markova; E. N. Biryukova; T. I. Goryainova; R. V. Kulumbegov; S. N. Khadzhiev; L. E. Kitaev; V. V. Yushchenko (42-46).
The effect of the nature of the metal introduced into HZSM-5 on the properties of the catalysts for the synthesis of olefins from dimethyl ether was studied. By means of the ammonia temperature-programmed desorption technique, it was shown that a decrease in the total amount of acid sites increases the selectivity for lower olefins. As the ratio of the medium to strong acid sites increases, the yield of olefins increases. The effect of the nature of gaseous additives in the feedstock on the selectivity for lower olefins was studied at T = 340°C, p = 0.1 MPa, and ν 0 = 2000 h−1.

Natural gas conversion on ZSM-5 zeolites modified with zirconium and molybdenum nanopowders by L. N. Vosmerikova; A. V. Vosmerikov; Ya. E. Barbashin; V. I. Zaikovskii; V. V. Kozlov (47-52).
The joint promoting action of zirconium and molybdenum nanosized powders on the catalytic properties of ZSM-5 zeolite with different silica ratios in the conversion of natural gas into liquid hydrocarbons was studied. By means of thermal analysis and high-resolution transmission electron microscopy, data on the amount and nature of the coke deposit produced during the reaction on the surface of the Zr-Mo/ZSM-5 catalyst were obtained. It was shown that the addition of zirconium to the molybdenum-containing catalyst leads to enhancement of the catalyst activity and selectivity in the formation of aromatic hydrocarbons from natural gas components. It was found that the maximal amount of aromatic compounds is formed in the presence of zeolite having a silica ratio of 40 and containing 0.5% Zr and 4.0% Mo.

State of the metal and the mechanism of transformations of alkanes on platinum-containing zeolite catalysts by M. N. Mikhailov; I. V. Mishin; L. M. Kustov; A. Yu. Stakheev (53-58).
The structure and reactivity of Pt6 particles in silicalite and the sodium and hydrogen forms of zeolite ZSM-5 were investigated by density functional theory. In the case of adsorption on the sodium form and silicalite, the interaction energy is 15 and 9 kcal/mol, respectively, and a negative charge appears on the metal cluster. In the channels of the hydrogen form, the energy of absorption of a metal particle increases to 45 kcal/mol and oxidized platinum species is formed. The formation of the active center on the zeolite H-form involves the interaction of the platinum particle with an acid site, resulting in the suppression of the acidity of the support. An alternative alkane conversion mechanism is proposed, which avoids the involvement of the acid sites. Predictability of the direction of transformation of alkanes adsorbed on metal particles is shown.

Synthesis of ethylbenzene on zeolite catalysts by I. M. Gerzeliev; S. I. Myachin; I. D. Tasueva; S. N. Khadzhiev (59-65).
Scaling of the process for zeolite-catalyzed ethylbenzene synthesis used as an example is shown, and the catalyst characteristics and product yields are given. The properties of the catalysts and their stability were studied in laboratory, micro-pilot, pilot, and demonstration units with reactor volumes of 0.01, 1, 100, and 1000 dm3, respectively, a sequence that, in combination with the selection of an optimal catalyst, made it possible to determine more exactly the role of each scaling level. The design of the last reactor was practically identical to that of the industrial reactor. The results of the experiments showed that the product quality and the catalyst service life were the same in the pilot and demonstration reactors operating at identical temperatures, feedstock compositions, and olefin space velocities. To confirm the results under conditions identical to those of an industrial reactor and to devise a mathematical model of the process, the pilot and demonstration units used were designed in such a manner that the basic engineering principles of the industrial reaction could be verified. As a result, the domestic technology of industrial-scale ethylbenzene production on heterogeneous catalysts was implemented.

Hydroalkylation of benzene and ethylbenzene over metal-containing zeolite catalysts by I. B. Borodina; O. A. Ponomareva; V. V. Yushchenko; I. I. Ivanova (66-73).
The hydroalkylation reaction of benzene and ethylbenzene over BEA zeolites with a Si/Al ratio of 9–190, MOR with Si/Al = 48, and MFI with Si/Al = 25 containing ruthenium, rhodium, platinum, or palladium was studied, as well as over the Ru/BEA zeolites with Si/Al = 42 doped with a second metal: nickel, cobalt, or rhodium. The catalytic experiments were conducted under flow conditions in the temperature range 130–190°C, a pressure of 1 MPa, a feed weight hourly space velocity of 2–64 h−1, and a stoichiometric reactant ratio. It was shown that the main reaction routes are the complete hydrogenation of benzene and ethylbenzene yielding cyclohexane and ethylcyclohexane, respectively; hydroalkylation yielding cyclohexylbenzene, para- and meta-ethylcyclohexylbenzenes, and diethylcyclohexylbenzenes; and alkylation resulting in dicyclohexylbenzenes and ethyldicyclohexylbenzenes. The ruthenium-promoted (1 wt %) zeolite BEA with Si/Al = 42 displayed the highest activity and selectivity in the benzene and ethylbenzene hydroalkylation reactions. Doping of the catalyst with cobalt and rhodium did not improve its catalytic properties, presumably, owing to the fact that the dopant metals largely occur in the cationic form according to the IR data for adsorbed CO. An admixture of nickel (0.5 wt %) to the catalyst increases the catalyst operation stability without reducing the yield of ethylcy-clohexy lbenzenes.

The properties of the Pt-SAPO-31 catalyst in hydrocarbon feed conversion depending on the catalyst chemical composition and crystallinity has been studied on the laboratory scale. The results of pilot testing of a Pt-SAPO-31 catalyst specimen in hydroisomerization reactions of real diesel fractions are presented. It is shown that the catalyst has high activity and selectivity in feedstock transformation as confirmed by a decrease in the cloud- or freezing point of diesel fuel with a yield of 96–98%. Catalyst life tests have shown high operation stability over more than 800 h without variations in the catalytic activity and the temperature characteristics of the product. Hydrogenation of unsaturated compounds present in the feedstock also results in diesel fuel upgrade.

Hydroisomerization of n-octane on platinum-containing micro-mesoporous molecular sieves by S. V. Konnov; Yu. V. Monakhova; E. E. Knyazeva; V. V. Yushchenko; O. A. Ponomareva; I. I. Ivanova (79-85).
The hydroisomerization reaction of n-octane at atmospheric pressure and a temperature of 230°C on platinum-containing catalysts with a combined micro-mesoporous structure synthesized on the basis of MOR and BEA zeolites was studied. The influence of the nature of zeolite, the relative amount of micropores, the platinum content, and the Si/Al ratio on the catalytic activity was examined. The microporous materials showed a considerably higher n-octane conversion and a higher isomerization selectivity as compared to both starting zeolites and mesoporous catalysts. It was found that the BEA-based micro-mesoporous materials are more active and selective than mordenites. An increase in platinum loading from 0.2 to 0.7 wt % leads to a rise in the yield of octane isomers, and a further increase in the platinum content does not result in a substantial change in the characteristics of the processes. It was shown that a change in the Si/Al ratio has a considerable effect on the formation of polybranched C8 isomers.

Manufacturing of alkylate gasoline on the polycation-decationated form of nickel-and cobalt-promoted zeolite Y by R. R. Shiriyazdanov; U. Sh. Rysaev; S. A. Akhmetov; A. P. Turanov; Yu. V. Morozov; E. A. Nikolaev (86-89).
The synthesis of alkylation catalysts based on ultrastable zeolites Y in the polycation-decationated form promoted with the transition metals nickel and cobalt is described, and the results of catalyst testing in the alkylation of the recycle fraction for the manufacturing of oligomer gasoline are presented.

Decalin ring opening reactions on ruthenium-containing zeolite MCM-41 by D. Yu. Murzin; D. Kubicka; I. L. Simakova; N. Kumar; A. Lazuen; P. Mäki-Arvela; M. Tiitta; T. Salmi (90-93).
Ruthenium catalysts supported on the mesoporous carrier MCM-41 were synthesized and characterized. It was found that the presence of the metal markedly accelerated decalin ring opening reactions as compared to the acid support alone, and it increases the selectivity owing to inhibition of protolytic cracking. It was shown that activity of ruthenium catalytic systems is lower than that of platinum catalysts supported on MCM-41 and much lower than the activity of platinum on zeolites. The low activity of catalytic systems based on the mesoporous support MCM-41 is due to its substantially lower acidity in comparison with zeolites beta and Y. Thus, it is concluded that the use of MCM-41 in decalin ring opening reactions is limited even in the presence of the metal, first of all, because of the low acidity of the support.

The tetrahydrofuran-nitrile (CH3CN, n-C4H9CN, C6H5CN)-zeolite (faujasites, mordenite, beta, pentasils) system and its transformations under supercritical conditions were studied. The feasibility of direct synthesis of the corresponding N-acylpyrrolidines from THF and nitriles of aliphatic and aromatic acids was shown for the first time. The dependence of the THF reaction with nitriles on the temperature, the reaction time, the nature of the exchanged cations in zeolite, the type of zeolite, and the catalyst pretreatment conditions was revealed. Acid zeolites were shown to exhibit a high catalytic activity. The yield of N-acylpyrrolidines at 350°C in the presence of the most active catalysts (HNaY and HCaLnY) was 10–40% at a selectivity of up to 80%. The key role of H2O was found, and a two-step scheme of the process, including the hydrolysis of nitrile to amide and the reaction of the latter with tetrahydrofuran resulting in the formation of N-acylpyrrolidine, was proposed.

Nanostructured (I) Fe2O3 and Co3O4 stabilized in the mesopores of an MCM-41 sieve and immobilized (II) FeCl2, Fe(acac)3, and FePc on the surface of an MCM-41 sieve functionalized with 3-aminopropyltriethoxysilane (3-APTES) were synthesized and examined. The materials were characterized by elemental analysis, H2 -TPR, X-ray diffraction analysis, IR and electronic absorption spectroscopy, as well as by low-temperature N2 adsorption. The catalytic activity was evaluated in the reaction of liquid-phase oxidation of benzene and phenol with hydrogen peroxide. Catalysts I showed a low activity in benzene oxidation, whereas catalysts II were active in the oxidation of phenol.