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Изомеризация парафиновых углеводородов является одним из важнейших процессов нефтеперерабатывающей промышленности, направленный на получение высокооктановых экологичных компонентов современных бензинов. Актуальным направлением в изомеризации является переработка фракции, содержащей С7-алканы. Обзор посвящен современным представлениям о закономерностях формирования активной поверхности вольфраматсодержащего диоксида циркония, который представляет собой высокоактивную каталитическую систему для реакции изомеризации гептанов. В обзоре рассматриваются вопросы по влиянию способа синтеза вольфраматсодержащего диоксида циркония, его химического состава, фазового строения и кислотных свойств на формирование активной поверхности систем WO3/ZrO2 и их каталитическую активность. Рассмотрена роль платины в каталитических системах WO3/ZrO2 для реакции изомеризации С7-алканов.

The influence of aromatic hydrocarbons (benzene, toluene) on isomerization of n-heptane over Pt/MOR/Al 2 O 3 and Pt/WO 3 /ZrO 2 catalysts was studied. The presence of aromatic hydrocarbons was shown leads to the necessary temperature elevation by 20–30 °C in order to provide the conversion identical to that of individual n-heptane. In the mixture of n-heptane with aromatic hydrocarbons, the yield of heptanes isomers was established to be 1.5 times less (from 60.1 to 39.9 wt %) in the presence of Pt/MOR/Al 2 O 3 but to remain at the same level (60.4–68.0 wt %) in the presence of Pt/WO 3 /ZrO 2 . The developed catalysts can be used in industry for isomerization of C7 fraction isolated from straight-run gasoline and from catalytic reforming gasoline, the presence of aromatic hydrocarbons in the feedstock being undesirable.

The effect of fluorine additives (1.5–3 wt.%) in Pt/WO3−ZrO2−Al2O3 catalysts on n−hexane isomerization was studied. The best performance was obtained in the presence of catalyst with the fluorine content 2.5 wt.% at 240°C: conversion – 80.0 %, selectivity – 88.5%, yield of stable catalyzate – 93.2 wt.%, yield of the sum of hexane isomers – 70.8 wt.%, and yield of high-octane dimethylbutanes (DMB) – 16.1 wt.%. Fluorine additives were shown to change the unit cell parameter a of tetragonal zirconia due to the substitution of oxygen atoms by fluorine atoms.The effect of fluorine additives (1.5–3 wt.%) in Pt/WO3−ZrO2−Al2O3 catalysts on n−hexane isomerization was studied. The best performance was obtained in the presence of catalyst with the fluorine content 2.5 wt.% at 240°C: conversion – 80.0 %, selectivity – 88.5%, yield of stable catalyzate – 93.2 wt.%, yield of the sum of hexane isomers – 70.8 wt.%, and yield of high-octane dimethylbutanes (DMB) – 16.1 wt.%. Fluorine additives were shown to change the unit cell parameter a of tetragonal zirconia due to the substitution of oxygen atoms by fluorine atoms.

Sulfated zirconia catalysts supported on SiO 2 and Al 2 O 3 were prepared and studied. Phase composition of the catalysts, acidic properties in CO adsorption, and textural characteristics were assessed. Activity of the catalysts in isomerization of n-hexane was measured. Alumina was shown to be a promising support for the synthesis of such catalysts. A new step of additional sulfation after platinum deposition was proposed for the synthesis of alumina-supported catalysts. It was found that strong Lewis acid sites with CO absorption bands at 2210 and 2224 cm -1 are formed in the catalysts. The yield of the sum of hexane isomers for the alumina-supported catalysts reached 80 wt.%.

The effect of concentration of the metallic component – platinum (0.1-2 wt.%) – and its electronic state in Pt/WO3/ZrO2 catalysts on characteristics of n-heptane isomerization was studied. It was found that a rise in the platinum concentration to 1.5 wt.% increases the yield of the target products of n-heptane isomerization – high-octane di- and trimethyl-substituted isomers (DTMS). Calcination of the catalyst in flowing air was shown to facilitate the formation of charged platinum, the presence of which enhances the catalyst activity.

An attempt was made to use particle swarm optimization (PSO) method for solving the inverse chemical kinetics problem for the n-hexane isomerization process on a sulfated zirconia catalyst sample. A perspective supported isomerization catalyst based on sulfated zirconia supported on alumina was chosen. Also the optimal coefficients for this problem were chosen. Method of determining the kinetic rate constants for the hexane isomers interconversion was tested. Model of hexanes interconversion based on calculated kinetic rate constants was built.

Modification of Pd/SO4/ZrO2/Al2O3 catalysts with HF, HNO3 and H2C2O4 acids during the support synthesis upon mixing of aluminum and zirconium hydroxides was studied. The amount of HF and HNO3 inorganic acids was found to exert a significant effect on the textural characteristics, such as specific surface area, pore volume and effective pore diameter. In the case of oxalic acid used at the concentrations characterized by variation of acidic modulus from 0.001 to 0.1, the pore structure parameters of the catalysts remained virtually unchanged. The XRD study demonstrated that modification with HF, HNO3 and H2C2O4 acids allows controlling the ratio of tetragonal and monoclinic phases of zirconia. It was found that among the tested acids the most pronounced effect on n-hexane isomerization was exerted by the introduction of hydrofluoric acid.Modification of Pd/SO4/ZrO2/Al2O3 catalysts with HF, HNO3 and H2C2O4 acids during the support synthesis upon mixing of aluminum and zirconium hydroxides was studied. The amount of HF and HNO3 inorganic acids was found to exert a significant effect on the textural characteristics, such as specific surface area, pore volume and effective pore diameter. In the case of oxalic acid used at the concentrations characterized by variation of acidic modulus from 0.001 to 0.1, the pore structure parameters of the catalysts remained virtually unchanged. The XRD study demonstrated that modification with HF, HNO3 and H2C2O4 acids allows controlling the ratio of tetragonal and monoclinic phases of zirconia. It was found that among the tested acids the most pronounced effect on n-hexane isomerization was exerted by the introduction of hydrofluoric acid.

The effect of Pt and Pd concentration in WO3/ZrO2 catalysts on their acidic and catalytic properties in isomerization of n-heptane has been studied. It was found that the highest yield of the target products of the reaction – di- and trimethyl substituted (DTMS) high-octane heptane isomers – is reached on the samples with the platinum content of 1.0–1.5 wt.% and is equal to 29.2–29.3 wt.%. When Pd is used as a metallic component, the DTMS yield of ca. 29.1 wt.% is attained at a palladium content of 0.1 wt.%. Pt(Pd)/WO3/ZrO2 catalysts were subjected to thermal treatment in a hydrogen medium and effect of the treatment conditions on isomerization of n-heptane was investigated. The reduction of the catalysts at temperatures above 300°C was shown to reduce tungsten atoms with the formation of Lewis acid sites (LAS), thus promoting the side reactions leading to cracking of heptanes.

The performance analysis of the reforming catalyst PR-9 and its replacement prediction on the catalyst PR-81for production reforming unit L-35-11/450K have been carried out using a mathematical model. The effect of feedstock composition on product yield has been studied. It is shown that the feedstock composition decisively influences the yield and octane number. The model study have shown that the replacement for the PR-81 catalyst will increase the yield of 2.5-3.5% wt.

Researches of catalysts Pt/WO 3 /ZrO 2 (Pt content is 1 wt.%) at varying WO 3 concentrations (10-35% wt.) are carried out in the isomerization reaction of n-heptane, under the following conditions: temperature range is 140-220°C, pressure is 1.5 MPa, the ratio H 2 /n-heptane is 3 (mol.), heptane volume velocity is 1h-1. X-ray analysis, N 2 adsorption-desorption, infrared spectroscopy, temperature-programmed desorption of ammonia are used to characterize the physical and chemical properties of the prepared catalysts, atomic emission spectrometry with inductively coupled plasma is for WO 3 analysis. Maximum catalysts activity and selectivity in the isomerization reaction of n-heptane is obtained at the reaction temperature of 170°C on the catalyst with a content of 25% wt WO 3 .: conversion of n-heptane is 84%, the selectivity to the heptane isomers sum is 71.9%, dimethyl and trimethyl heptane isomers yield is 22.8% wt.

The effect of palladium concentration in a range from 0.02 to 1.6 wt.% on characteristics of n-hexane isomerization was studied. The (O2-Hchem) titration and O2 chemisorption study revealed that palladium in Pd/SO4/ZrO2/Al2O3 systems adsorbs hydrogen in a ratio H/Pds = 1.13-1.65 at./at. Investigation of the charge state of the metal by IR spectroscopy of adsorbed CO showed the presence of both the metallic (Pd0) and charged palladium species. Pd/SO4/ZrO2/Al2O3 catalysts with charged palladium atoms exhibit high activity and selectivity in n-hexane isomerization.

The effect of zirconia precursor in Pt-containing WO3/ZrO2 catalysts on isomerization of n-heptane was studied. Samples synthesized with zirconium sulfate as a ZrO2 precursor were shown to be more ...

Pd/Al2O3, Pd/SiO2 and their mechanical mixtures with SO42-/ZrO2/Al2O3 were prepared and tested in isomerization of n-hexane. The best catalytic performance was reached on the alumina systems where a part of palladium atoms was in the charged state.

Pd/SO 4 2 -/ZrO 2 /Al 2 O 3 catalysts are prepared and investigated in reaction of isomerization of N-hexane in the work. For comparison Pt/SO 4 2 -/ZrO 2 /Al 2 O 3 catalysts are investigated. It is established that in the field of low temperatures (140 °C) the catalyst on the basis of palladium shows high rates comparable to the Pt-containing catalyst. At more high temperatures yielding of isomers for Pd/SO 4 2 -/ZrO 2 /Al 2 O 3 catalyst are lower, than for Pt/SO 4 2 -/ZrO 2 /Al 2 O 3 . However, isomerization depth (the maintenance of a 2, 2-dimetilbutan in mix of C 6 isomers) for the palladic catalyst in all studied range of temperatures exceeds for 6-10% a similar indicator for the platinum catalyst. For clarification of the role of condition of palladium the catalysts Pd/Al 2 O 3 , Pd/SiO 2 were prepared and investigated. It was established that the best indicators are reached on the aluminum oxide systems in which palladium is in the oxidized state.

The paper presents the results of the carrier acidity impact studying on the Pt-Re/Al 2 O 3 catalytic properties in gasoline reforming. The Pt-Re/Al 2 O 3 catalyst preparation based on the superacidity carrier in consequence of the presence of promotor - the bayerite phase of aluminum hydroxide resulted in the H-C 7 predominat cracking to C 3 -C 6 light paraffins. The obtained catalyst allows to produce the reduced aromatics content reformed gasoline (55%wt).

Pt/MOR–Al2O3 catalysts, with platinum supported from H2PtCl6 and [Pt(NH3)4]Cl2 solutions are investigated in the work with the methods of IR spectroscopy. The received results testify about platinum fixing mainly in channels of a mordenite in case of supporting from an ammine, and its localization on Al2O3 surface when supporting from chloroplatinic acid. Small concentration of the absorption bands referred to bridging CO species on platinum testify about high dispersion of metal on samples. Data explain higher activity of the catalysts prepared with [Pt(NH3)4]Cl2 in reactions of a hydroisomerization of benzene and an isomerization of cyclohexane.