Aluminoplatinum Catalyst Research Articles

ИСПОЛЬЗОВАНИЕ ГИДРОКРЕКИНГА ПРИ ПЕРЕРАБОТКЕ СВЕРХВЯЗКОЙ НЕФТИ АШАЛЬЧИНСКОГО МЕСТОРОЖДЕНИЯ

The high necessity of development of innovative technologies for heavy oil processing is caused by decreasing reserves and increasing volumes of conditioned oil and gas fields in the world. One of the alternatives to primary processing of heavy oils, implemented at the fields, can be technologies based on extraction processes to obtain deasphalted oil. The present study is aimed at studying the products of various stages of hydrotreating of heavy high-sulfur deasphalted oil from the Ashalchinskoye field (Tatarstan, Russia) in the presence of aluminocobaltmolybdenum and aluminoplatinum catalysts. Conversion of deasphalted heavy oil on aluminocobaltmolybdenum catalyst in the hydrocracking process led to changes in the properties and composition of distillate fractions. Decrease in the content of bicyclic aromatic hydrocarbons, increase in the amount of monocycloaromatic and paraffin-naphthenic hydrocarbons, decrease in refractive indices, density and viscosity of distillate fractions were found. The revealed regularities in the composition of hydrotreating products testify to the hydrogenation reactions of polycyclic aromatic compounds, naphthene rings splitting, decomposition of long paraffin chains and their isomerization. It was shown that sulfur compounds contained in different fractions of deasphalted heavy oil differ in their stability to transformation reactions under conditions of catalytic hydrogenation on aluminocobalt-molybdenum catalyst. The second stage of hydrogenation on aluminoplatinum catalyst allowed to reduce the sulphur content in the final product to 0.035 % wt. The obtained data on the composition and technological properties of products of catalytic hydrotreating of heavy deasphalted oil from Ashalchinskoye field indicate the possibility of using widely available aluminocobaltmolybdenum catalysts in processing to obtain high quality hydrocarbon feedstock for petrochemical processes.

Low-Temperature Sorption–Luminescence Determination of Platinum Using Silica Chemically Modified with N-Allyl-N"-Propylthiourea and N-Phenyl-N"-Propylthiourea

Silicas chemically modified with N-allyl-N"-propylthiourea and N-phenyl-N"-propylthiourea were proposed for the low-temperature sorption–luminescence determination of platinum. The sorption of platinum(II) and platinum(IV) at the surface of sorbents yields coordination compounds luminescing at 77 K under UV irradiation. Luminescence spectra of platinum(II) complexes of thiourea derivatives covalently bonded to the silica surface exhibit a broad structureless band with a maximum at 585 nm. For the sorbent with N-allyl-N"-propylthiourea groups, the detection limit of platinum is 0.1 μg per 0.1 g of the sorbent. The calibration plot is linear up to 50 μg/0.1 g. The detection limit and the linearity range of calibration plots depend on the mass of the sorbent. The proposed procedure was used for the analysis of aluminoplatinum catalysts.

Modernization of a reformer unit with a lower operating pressure

Modernization of the first-stage of the L–35–11/1000 plant of the OAO “Angarskaya neftekhimicheskaya kompaniya” [“Angarskaya Petrochemical Company” (Open Joint Stock Company)] reduced the pressure in the reformer unit from 2.3 to 1.7 MPa and the hydrogenous gas circulation ratio, from 1550 to 1100 m3/m3. The catalyzate yield increased by 2.1 wt.% while the motor octane number (MON) increased by 1.6. After the second stage of the highly efficient domestic catalysts KR–108U and RB–22U fed into the reformer unit will increase the reformate yield with MON=87 to 89 wt. %. Catalyzate from the L–35–11/100 plant is the main component of high-octane gasolines in the Angarskaya Petrochemical Company. This typical plant was built during the development of the country's catalytic reformer technology [1] according to a design by Lengiproneftekhim (Leningrad State Institute for the Design of Oil Refining and Petrochemical Plants). Initially, the intention was to use the aluminoplatinum catalyst AP–64 in the reforming of hydrofined feedstock in the following mode: reactor pressure in the last stage 3.5 MPa, feedstock volumetric flow rate 1.2 h−1, and hydrogenous gas (HG) circulation ratio 1800m3/m3. The process flow diagram, however, made no provision for booster compressors for the excess HG. As a result substantial lowering of the pressure in the reformer unit was not possible when the plant was switched to more stable polymetal catalysts [2].

Effect of the surface area of platinum on the activity of a bifunctional aluminoplatinum catalyst in the synthesis of alkylimidazoles from diamines and carbonyl acids

An investigation has been conducted into the effect of the acid and dehydrogenating functions of an aluminoplatinum catalyst on the synthesis of 2-methylimidazole from ethylenediamine and acetic acid. It has been established that formation of the intermediate 2-methylimidazoline involves the acid Al2O3 centers and its rate of formation is greater than the rate of its subsequent dehydrogenation to 2-methylimidazole on the Pt centers. The symbatic nature of the variations in the 2-methylimidazole yield and the surface area of the platinum in the aluminoplatinum catalyst has been demonstrated.

The staged synthesis of 2-methylimidazole from ethylenediamine and acetic acid in the presence of a bifunctional aluminoplatinum catalyst

An investigation has been conducted into the staged synthesis of 2-methylimidazole from ethylenediamine and acetic acid in the presence of a bifunctional aluminoplatinum catalyst. It has been shown that the formation stage of 2-methylimidazoline occurs more quickly on γ-Al2O3 than its dehydrogenation on the Pt centers. From a comparison of the processes of dehydrogenation of 2-methylimidazoline in the molten phase and in aqueous solution it follows that the water eliminated in the imidazoline formation stage could cause the decrease in activity during the dehydrogenation on the Pt centers. The structures of the secondary and intermediate products have been established for each stage of the process and their formation routes are discussed.

Dehydrogenation of propane on aluminoplatinum catalysts modified with Re, Zr, Sc, and Sn

The effect of addition of Re, Zr, Sc, and Sn on an aluminoplatinum catalyst in the reaction of dehydrogenation of propane was investigated. It was shown that addition of 0.2–0.5% Zr, Sc, or Re virtually does not alter the catalytic properties of the aluminoplatinum catalyst (APC); addition of 0.2% Sn increases the activity, selectivity, and stability of Pt/Al2O3. The amount of coke deposited on the APC after the first 5 min of work decreases by three times in the presence of Sn. The coke is more enriched with hydrogen than the other systems formed on the surface of Pt-Sn/Al2O3.

Methane and butane oxidation on aluminoplatinum catalysts

Methane and butane oxidation by oxygen (air) on once used AP-56 reforming catalyst has been studied at temperatures 663–773 and 493–533 K, respectively. Kinetic equations for these reactions are proposed and the difference in their oxidation mechanisms is discussed.

Catalytic and physicochemical properties of aluminoplatinum catalysts modified with indium and gallium

1. It was shown that the increase in the catalytic activity of aluminoplatinum catalysts modified with indium and gallium is not due to a change in the dispersion and electron donoracceptor properties of the platinum. 2. Introduction of the promoting additive results in an increase in the Dumber of sites of high-temperature dissociative adsorption of hydrogen on the surface of the catalysts, and they are apparently included in the active sites of the reaction of dehydrogenation of higher n-paraffins.

Effect of Germanium and Zirconium on the activity of a platinum catalyst in dehydrocyclization of n-hexane

The addition of zirconium and germanium to an alumino-platinum catalyst (atomic ratio of E/Pt being 1:2) increases its activity and selectivity for dehydrocyclization of n-hexane, apparently due to the part played in the reaction by transition metal clusters containing variable valency platinum.

Study of alumino-platinum-lithium catalysts during dehydrogenation of n-decane using the pulse method

Considerable practical significance is attached at the present time to catalytic dehydrogenation of C/sub 10/ and higher n-paraffins into mono-olefins, which form a raw material for obtaining surface-active substances (SAS) subjet to bio-decomposition. Alumino-platinum (AP) catalysts with alkali additives, mainly lithium are the most popular, according to data in patent literature. The effect of the latter on the ratio of products formed during this process has been insufficiently investigated. A study is made in this paper of dehydrogenation of n-decane in the presence of AP catalysts containing a varying amount of lithium, in order to establish the relation between the lithium additive and the variation of physico-chemical and catalytic properties of these catalysts and establish the causes of increased selectivity of catalysts in the formation of monoolefins.

The effect of titanium on the dispersity of platinum particles in aluminoplatinum catalysts

1. X-ray analysis, oxygen chemisorption measurements, and curves of the radial distribution of atoms have been used to study the formation of platinum particles on a: γ-Al2O3 surface in the presence of titanium. 2. The addition of Ti to the system affected the dispersity of the platinum particles in every case. This action arises from the preferential interaction with the added TiO2, and depends on the Pt and Ti concentrations.

A kinetic isotope study of the mechanism of C5-dehydrocyclization of paraffin hydrocarbons on aluminoplatinum catalysts

1. Kinetic isotope methods have been used to study the catalytic reactions of 2-methylpentane on bifunctional aluminoplatinum catalysts, working over the temperature interval from 330 to 400°C. 2. C5-dehydrocyclization of alkanes proceeds along two different reactions paths on these catalysts, by direct cyclization to the cyclane and through intermediate olefin formation.

The configurational isomerization of stereoisomeric dimethyl-cyclohexanes on aluminoplatinum catalysts

1. The configurational isomerization of cis-1,4- and trans-l,3-dimethylcyclohexanes was studied on bifunctional aluminoplatinum catalysts. 2. The reaction takes place similarly on 0.6% Pt/Al2O3 and 20% Pt/C catalysts: zeroorder kinetics relative to the hydrocarbon, similar activation energies, and the necessary participation of hydrogen. 3. It was proposed on the basis of the data obtained that the configurational isomerization of dimethylcyclohexanes on Pt/Al2O3 takes place by an associative mechanism similar to that proposed earlier for Pt/C.

Dependence of the directions of hydrolysis of methylcyclopentane on Pd-Al2O3 on the distribution of electron density in the molecule

1. Raising the pressure from 10 to 40–50 atm leads to opposite changes in the direction of hydrogenolysis of methylcyclopentane, depending on the catalyst: in experiments with an aluminoplatinum catalyst, the ratios of n-hexane to 2-methylpentane formed, n-hexane to 3-methylpentane, and 3-methylpentane to 2-methylpentane increase, while in the case of an aluminopalladium catalyst these ratios decrease. 2. The results obtained agree with the earlier hypothesis of a dependence of the direction of the hydrogenolysis reaction on the charges of the carbon atoms and charges of the metal atoms contained in the catalyst.

Aromatization of n-nonane in the presence of alumino-platinum catalysts

Aromatization of n-nonane in the presence of alumino-platinum catalysts

Catalytic reforming of gasoline by alumino-platinum catalysts promoted by rare-earth elements

1. The effect was investigated of additions of rare-earth elements on the properties of alumino-platinum catalysts in gasoline-reforming reactions. 2. It is found that alumino-platinum catalysts promoted by rare-earth elements have greater activity, selectivity, and thermal stability in comparison with unpromoted samples.

The unique influence of the pressure of hydrogen and adsorbed water on the activity of an aluminoplatinum catalyst in the hydrogenolysis of methylcyclopentane

1. The influence of hydrogen pressure and adsorbed water on the activity of a 0.3% Pt-Al2O3 catalyst in the hydrogenolysis of methylcyclopentane was investigated. 2. The activity of the catalyst decreases both with increasing hydrogen pressure from 2 to 49 atm in experiments with a catalyst containing adsorbed water, and when water is removed from the catalyst in experiments at a total pressure of 10 atm. 3. The activity of the catalysts increases both when the hydrogen pressure is increased from 9 to 49 atm in experiments with a catalyst freed of adsorbed water and when water is removed from the catalysts in experiments at a total pressure of 50 atm. 4. On the basis of the assumption of two mechanisms of the reaction, an explanation was suggested for the opposite changes in the activity of the catalyst with increasing hydrogen pressure or with the removal of water from the system.

The stepwise mechanism of the aromatization of n-hexane in the presence of aluminoplatinum and aluminopalladium catalysts

1. In a comparative study of the aromatization of n-hexane in the presence of 0.6% Pt/Al2O3 and 0.6% Pd/Al2O3, the formation of aromatic hydrocarbons proceeds in both cases through reactions of C6- and C5-dehydrocyclization. 2. In the presence of Pd/Al2O3, the aromatization of n-hexane occurs primarily according to a reaction of C6-dehydrocyclization, while the reaction of C5-dehydrocyclization is secondary. 3. In the presence of Pt/Al2O3, the relative importance of the reaction of C5-dehydrocyclization, followed by dehydroisomerization to aromatic hydrocarbons, is substantially greater than for the palladium catalyst. 4. The reaction of C6-dehydrocyclization of n-hexane in the presence of both catalysts represents a consecutive process of successive dehydrogenation with the formation of monoolefin, a diene, and a triene, which are readily converted to an aromatic hydrocarbon.

Hydrogenation of benzene and isoprene on aluminoplatinum catalysts modified with manganese and chromium

1. Modification of an aluminoplatinum catalyst with manganese in a ratio Pt∶Mn=10∶1 promotes an increase in the activity of this catalyst in the reaction of hydrogenation of benzene and a decrease in the effect of poisoning by thiophene. The addition of chromium in the same amount reduces the activity and stability of the catalyst with respect to poisoning by thiophene. 2. In the case of modification of an aluminoplatinum catalyst with additions of manganese and chromium, the activity of the catalysts obtained in the liquid phase low-temperature hydrogenation of isoprene is increased.

The role of the carrier in aluminoplatinum catalysts

1. An investigation was made of a 5% aluminoplatinum catalyst in the hydrogenolysis of methylcyclopentane. A comparison of the results obtained with previously published data permits us to conclude that with respect to a number of characteristics, a 5% aluminoplatinum catalyst is similar to platinized charcoal and silica gel and differs sharply from an aluminoplatinum catalyst containing 0.3% of the metal. 2. In aluminoplatinum catalysts, the aluminum oxide not only provides for high dispersion of the applied metal, but also determines its catalytic properties, evidently as a result of a change in the electronic state of the atoms adjoining the surface of the carrier.