Petroleum Chemistry (v.48, #1)
Conversion of lower alcohols into C2–C4 olefins over acid-base catalysts by R. V. Ermakov; V. A. Plakhotnik (1-5).
The conversion reactions of methanol, ethanol, and their ethers in the presence of acid-base catalysts based on mesoporous ZSM-5 and ZSM-11 zeolites, microporous SAPO zeolites, heteropoly acids, and perfluorinated sulfonated cation exchangers are discussed. The set of reactions reflects the formation of olefins beginning from ethylene to butenes. The heats of reaction were estimated from the calculated values of the equilibrium constants and enthalpies at 700 K. It was assumed that the available experimental data for all three types of catalysts should be described by a complex mechanism of transformations of alcohols and ethers. The reaction sequence includes fast dehydration of alcohols into ethers. It is likely that, at temperatures of 512–573 K, the initial reactions have a common initiation mechanism for all three types of catalysts, which involves the formation of the protonated forms of substrate molecules that trigger the olefin synthesis reactions. For thermally stable catalysts (zeolites), the mechanism with participation of free radicals and olefins generated from the alkoxylated hydroxyl groups of zeolites is possible above 573 K. As the degree of conversion of ethers increases, carbenium and arenonium ions begin to play a progressively increasing role as active intermediates instead of the alkoxy groups. This crossover may be responsible for changes in both the kinetic parameters of the substrate transformation and the direction of the reaction over zeolites at 573–623 K. The schemes proposed in some published works for the conversion of oxygen-containing organic compounds and olefins with participation of superacid centers of the catalysts in question should be considered speculations in light of the effect of water leveling the strength of Brönsted sites.
Study of nonisothermal gas-oil catalytic cracking applying the microactivity test by K. Sertić-Bionda; Z. Gomzi; M. Fabulić-Ruszkowski; M. Muźic (6-14).
Catalytic cracking of gas oils has been studied in a standard microactivity test (MAT) reactor. The cracking product distribution was measured as a function of temperature. Based on these experimental results, a four-lump kinetic model was developed. Kinetic constants were estimated using the sequential step-optimization method. A nonisothermal nonsteady-state model for a fixed-bed MAT reactor was proposed. The overall heat of the reactions were taken from the macroscopic differences in the enthalpies of the products and reactants. The influence of the feedstocks used and reactor temperature were discussed. The reactor and kinetic model were validated with results from MAT test data. The simulation results are in good agreement with the experimental data.
Production of lower unsaturated hydrocarbons via catalytic conversion of dimethyl ether by A. V. Abramova; R. V. Kulumbegov; T. I. Goryainova; S. N. Khadzhiev (15-21).
Conversion of dimethyl ether over high-silica zeolite catalysts of the ZSM-5 type was studied. It was shown that the introduction of metals into the catalyst composition affects the activity and selectivity of the catalysts. It was found that the catalysts modified with Zr and P are most selective for light olefins. The influence of the addition of water to feedstock on the yields of the desired products was demonstrated; the results are similar to the data obtained by the Lurgi company.
Steam reforming of methane mixtures with ethylene over an industrial nickel catalyst by L. P. Didenko; V. I. Savchenko; V. S. Arutyunov; L. A. Sementsova (22-27).
Steam reforming of methane mixtures with ethylene (1.4–3.8 vol % C2H4) in the presence of the industrial nickel catalyst S11-9-09 (12.8 wt % Ni/α-Al2O3) at 750°C was studied. It was shown that the addition of ethylene to the methane-steam mixture reduces the conversion of methane to carbon oxides and increases coke formation. The unfavorable effect of ethylene on the reaction decreases with an increase in the ratio of the catalytic surface area to the free reaction volume. Presumably, this effect is caused by an increase in the contribution of the heterogeneous component of steam reforming, a change that results in an increase in the rate of the interaction of the formed coke with steam.
Conversion of n-butane to isoparaffins over modified mordenite-zirconia catalysts by D. B. Tagiev; A. A. Imanova; R. V. Starikov; M. I. Rustamov (28-31).
The catalytic properties of modified mordenite-zirconia catalysts in the conversion of n-butane to isoparaffins have been investigated. It has been shown that the modification with nickel, cobalt, and sulfate ions increases the activity of the mordenite-zirconia catalysts, thereby making it possible to lower the temperature of the process to 190–220°C. At lower temperatures, dilution with hydrogen retards the formation of isoparaffins.
Kinetic simulation of distribution of Fischer-Tropsch synthesis products on a cobalt catalyst at medium pressure by M. N. Yakubovich (32-35).
It was shown that the molecular-mass distributions of hydrocarbons formed on a Co-ThO2-MgO-kieselguhr industrial catalyst at 1MPa pressure differ from those found at low pressures and are adequately described by the previous mathematical model based on the data obtained on cobalt catalysts at high pressures. This indicates that secondary Fischer-Tropsch synthesis reactions at moderate pressures mainly follow the mechanism characteristic of high pressures. The causes of deviations of molecular-mass distributions of hydrocarbons formed under these conditions from the Anderson-Schulz-Flory ideal distribution with an increase in the synthesis temperature are discussed.
The influence of organic additives on the regioselectivity of oxygenation of alkanes with hydrogen peroxide in the presence of TS-1titanium silicalite by G. B. Shul’pin; T. Sooknoi; L. S. Shul’pina (36-39).
Hydrogen peroxide oxidizes n-hexane, n-heptane, and n-octane at 50°C in the presence titanium silicalite TS-1 as a catalyst, forming isomeric mixtures of ketones and alcohols. Admixtures of organic acids, alcohols, benzene, and ethylbenzene sharply change the ratio of position isomers. For example, the normalized ratio is C(4): C(3): C(2) = 0.44: 1.0: 0.47 for n-heptane oxidation in the absence of additives, but it becomes 0.52: 1.0: 1.00 in the presence of benzyl alcohol and the addition of ethylbenzene changes it to 0.16: 1.0: 0.94.
Difference in the mechanism of oxidation of alcohols and sulfides with oxygen in the presence of aldehydes by A. D. Malievskii (40-45).
It was shown that the mechanism of the joint liquid-phase oxidation of sulfides and aldehydes by air oxygen radically differs from that of the joint oxidation of alcohols and aldehydes. In the former case, the mechanism involves oxygen atom transfer to a sulfide by hydroperoxide or peroxide radicals produced upon aldehyde oxidation, yielding sulfoxide (or sulfone); in the latter case, an alcohol gives semiacetal in the reaction with aldehyde and the oxidation of the semiacetal results in ester formation.
Influence of the composition of vacuum residues as oxidation feedstock on the performance characteristics of road asphalts by S. V. Kotov; S. V. Levanova; Z. R. Madumarova; V. A. Pogulyaiko; L. V. Zinov’eva; V. A. Tyshchenko (46-50).
The hydrocarbon-group composition of short residues having different values of the specific viscosity was studied. The influence of the hydrocarbon-group composition of short residues from West Siberian crude oils on the properties of petroleum air-blown road asphalts was examined.
Effect of magnetic field on the paramagnetic, antioxidant, and viscosity characteristics of some crude oils by Yu. V. Loskutova; N. V. Yudina; S. I. Pisareva (51-55).
The effect of a magnetic field on the structural and rheological properties of crude oils with various concentrations of resins, asphaltenes, and paraffin hydrocarbons was examined. It was found that magnetic treatment leads to substantial changes in the paramagnetic, antioxidant, and viscosity characteristics of paraffin-base and high-viscosity oils. A factor that characterizes the quantity of inhibition centers increases with an increase in the amount of alcohol-benzene-extractable resins in the oils. The time of complete recovery of paramagnetic and antioxidant properties coincides with the recovery time of the rheological characteristics of petroleum.
Biodegradation of Baku oil and hydrocarbons by micromycetes by M. G. Veliev; B. Danielsson; M. A. Salmanov; S. R. Alieva; N. R. Bektashi (56-62).
Degradation of Baku oil, refinery products (diesel fuel, kerosene, and gasoline), and some individual aromatic hydrocarbons (toluene, p-xylene, and ethylbenzene) by micromycete cultures isolated from Caspian Sea water and coastal soil near the Apsheron peninsula was studied. The intensity of biodegradation of crude oil and petroleum products with micromycetes was determined by measuring carbon dioxide evolution and biomass formation. The conditions for chromatographic analyses of biodegradation products were determined. The dynamics of structure and composition of the test petrochemicals during oxidation with micromycetes was studied by means of gas-liquid and gas-solid chromatography and IR and 1H NMR spectroscopy. It was found that, under cooxidizing conditions, microorganisms convert toluene and p-xylene into the corresponding monocarboxylic acids and acetophenone (35–40%) and phenylacetic acid (60–65%) are formed in the case of ethylbenzene.
Study of aminomethylated derivatives of allylphenols as antimicrobial additives for TS-1 jet fuel by A. M. Magerramov; M. R. Bairamov; G. M. Mekhtieva; M. A. Agaeva; P. Sh. Mamedova; D. M. Kulieva; I. G. Mamedov (63-66).
A series of aminomethylated allylphenol derivatives was studied as antimicrobial additives for the jet fuel TS-1. It was found that these compounds at concentrations of 0.25 and 0.5% suppress the growth of microorganisms and do not rank below the well-known antibacterial additive 8-hydroxyquinoline in performance; moreover, 2-allyl-6-(dimethylamino)methylphenol,2-allyl-6-(diethylamino)methylphenol, and 2-allyl-6-piperidinomethylphenol are superior to this additive and, as such, can be recommended as effective antimicrobial additives for the TS-1 fuel. The formation of intermolecular and intramolecular hydrogen bonds in the reactants and the synthesized products was also studied.
Utilization of water treatment sludge in processes of oil recovery from aqueous media by L. Yu. Novoselova; E. E. Sirotkina; N. I. Pogadaeva (67-70).
The potential use of iron removal sludge of freshwater treatment facilities for the recovery of oil from aqueous media was established. A high adsorption capacity for oil of this material was shown using the deep-well water iron removal sludge from the Tomsk Akademgorodok water intake site. The oil-absorbing capacity of as-recived sludge was studied, conditions for its thermal treatment were chosen, and the ability of the thermally activated sludge to recover oil from aqueous media was examined.
Chemical behavior of 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene, and related compounds as a key to understanding specifics of radiation-chemical processes: 3. The structure of 5-vinyl-2-norbornene and 2-vinylnorbornane radical cations by I. Yu. Shchapin; O. V. Makhnach; V. L. Klochikhin; Yu. G. Osokin; A. I. Nekhaev (71-82).
Cyclic and distonic forms of radical cations were recorded by ESR in x-ray irradiated frozen solutions (1.0 vol %) of 5-vinyl-2-norbornene (VNB) and 2-vinylnorbornane in Freon 113 (CFCl2CF2Cl). In both cases, mixtures of isomers in a ratio of endo-: exo-= 66: 34 were used. It was shown that, in the general case, the endo-VNB radical cation rearranges into the radical cation of cis-3a,4,7,7a-tetrahydroindene through a multistage mechanism involving the intermediate formation of the distonic radical cation, not via the earlier suggested one-stage concerted mechanism. The interconversions of endo-and exo-VNB in γ-irradiated solutions of VNB in CCl4 were studied chromatographically. A general scheme of VNB transformations with allowance for the intermediate formation of the cyclic and distonic forms of the VNB radical cations is proposed. It was found that the structures of the radical cation distonic form and VNB homopolymer are identical, a resemblance that indicates the occurrence of VNB polymerization via the radical cation mechanism during its γ-irradiation.