CS234481B1 - Process for producing cyclohexane from petroleum gasoline fractions while producing n-hexane concentrates - Google Patents

Abstract

The invention describes the production of cyclohexane from petroleum gasoline fractions with the simultaneous production of n-hexane concentrates by a combination of distillation and very low-temperature hydrogenation associated with isomerization of cyclanes on a catalytic system consisting of platinum and chlorinated alumina.

Description

The present invention relates to a process for the production of cyclohexane from petroleum naphtha fractions in the simultaneous production of n-hexane concentrates by a combination of rectification, catalytic isomerization and optionally recirculation of methylcyclopentane.

The n-hexane concentrates are very suitable solvents in the Ziegler olefin polymerization because they excel by the inertness of the reaction mixture and thus guarantee the formation of preferred types of polymers. in the polymerization of propylene or ethylene propylene and the like. In addition, their properties guarantee low catalyst deactivation and a reduced concentration of volatile components in the resulting polymerization product. The prerequisite is a low content of aromatic and unsaturated hydrocarbons and an adequate concentration of methylcyclopentane. A maximum of one-tenth% of benzene and olefins are permitted. The methylcyclopentane concentration should not exceed about one percent. However, the raw materials from which this concentrate is produced do not comply with the strict requirements mentioned and must be treated chemically and physically-chemically. Petroleum desulphurized light gasoline contains hydrocarbons up to Crj, in which, depending on the type of oil, up to several% of benzene is present, the content of unsaturated hydrocarbons defined by the bromine index is often several hundred mg Br / 100 g _by weight. the ratio of n-hexane to methylcyclopentane is up to 1; 1. The removal of benzene and olefins is predominantly by catalytic vapor phase hydrogenation under pressure in the presence of platinum or nickel or tungsten and oxides of nickel or molybdenum and nickel on alumina. In particular, the hydrogenation of benzene is demanding in view of the need for high conversion. Low volumetric speeds and high working pressure are selected. The separation of n-hexane and methylcyclopentane is always a problem caused by near boiling points, and decreasing the ratio of n-hexane to methylcyclopentane worsens the yield of n-hexane concentrate with a defined concentration of methylcyclopentane and n-hexane.

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The methylcyclopentane present is a high-quality, high-octane component. can be dehydroisomerized to benzene. Its conversion to the important organic intermediate cyclohexane is adversely affected by thermodynamic equilibrium; % of cyclohexane in the mixture rapidly decreases with temperature and at hydrogenations above 200 ° C the cyclohexane content of the mixture is small and it is necessary to select multiple recirculation of unreacted methylcyclopentane to obtain it.

The main process for producing cyclohexane is based on benzene by catalytic hydrogenation while circulating the product on metal catalysts. A pressure of 2 to 5 MPa must be used and the usual catalyst is nickel or platinum. The benzene must have a purity of 99.8 to 99.9% to achieve the desired purity of cyclohexane. The catalysts are very sensitive to poisons, especially sulfur, and benzene has to be expensive to clean. A considerable excess of hydrogen (4-11 mol / mol benzene) was added. To remove the high heat of the reaction, the product must be recycled, cooled between the catalyst layers and a second reactor is added to complete the reaction (99.5%). · Cyclohexane isolated from petroleum fractions does not have the required purity for further processing.

The invention provides a novel solution for the production of acyclohexane from petroleum naphtha fractions while producing n-hexane concentrates. The process consists in the treatment of petroleum hydrotreated petroleum with a boiling point of 30 to 180 ° C and containing below 1 ppm of sulfur,

A of water and nitrogen is rectified by distillation to a fraction boiling in the range of 20 to 75 [deg.] C., containing in the mixture of iso- and n-alkanes 2 to 20% by weight. % methylcyclopentane (I) and cyclohexane (II) in wt. ratio 100: 1 to 20, in a molar ratio of I: II 200 to 3: 1, fraction A is optionally additionally mixed with methylcyclopentane concentrate B in wt. a ratio of 100: 1 to 20 per mixture C which is passed at a temperature of 30 to 150 ° C to a catalyst containing 0.2 to 0.8 wt. platinum on alumina activated 3 to 20 wt. chlorine at a rate of 1 to 12 vol% of mixture A or C / vol catalyst per hour, at a pressure of 2 to 10 MPa in the presence of a hydrogen containing gas in addition to light saturated hydrocarbons and max. or C, 1 to 5: 1 and 1 to 5: 1

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000 ppm wt. chloro derivative of hydrocarbon with atomic carbon: chlorine ratio min. 1: 2. The product is then separated by distillation in three stages into hydrocarbons together with hydrogen chloride, C 1 and C 8 hydrocarbons, n-hexane concentrate and a mixture of methylcyclopentane with cyclohexane. This is divided into methylcyclopentane kocentrate B, which optionally returns to fraction A, and cyclohexane. The methylcyclopentane isomerization catalyst preferably contains 0.3 to 0.45% by weight of platinum and is activated by 3 to 8% by weight. % aluminum chloride and may contain 0.01 to 0.8 wt. water. Carbon tetrachloride, trichloromethane, dichloromethane and the like are preferably used as activators. hexachloroethane. The hydrogen-containing gas comes from the catalytic reforming of gasolines and contains 60-95% by volume of hydrogen. The N-hexane concentrate isolated 2 of the product has a content of 50 to 90% by weight. % of n-hexane in addition to 3-methylpentane and methylcyclopentane and the methylcyclopentane concentrate has 50 to 95 wt. methylcyclopentane in addition to n-hexane and cyclohexane.

An analysis of the invention reveals a series of fastenings prior to the prior art. The production of cyclohexane and methylcyclopentane with the simultaneous production of n-hexane concentrate is less costly and energy-intensive. Isolation of cyclohexane from petroleum fractions by rectification is virtually impossible for contamination with isoheptanes. Cyclohexane production from benzene is based on an expensive raw material and is more energy and technologically demanding. In the technology of the present invention, cyclohexane is virtually the last hydrocarbon of the isomerization product and can be easily distilled to isolate, since the boiling point difference against methylcyclopentane is 9 ° C, making cyclohexane a valuable product that economically and energetically makes n-hexane concentrates more efficient. It is to be understood that the chlorine-activated platinum catalyst is either dry or 1-80% deactivated with water. The reaction conditions are adapted to the degree of deactivation. also the upper limit of pressure. In parallel, the invention puts two kinds of low-temperature isomerization catalysts, both activated in situ by hydrocarbon halides and off-screen by aluminum chloride, which is included in the concentration of chlorine on the catalyst.

Illustratively, the invention is shown by way of example, the conditions of which

- 4 should not, however, limit its scope.

Example 234 481

From the petroleum gasoline 30 to 180 ° C after hydrotreating, the C 1 to C 8 fraction whose composition is shown in Table 1 was separated by rectification. This fraction is characterized by a high ratio between methylcyclopentane and isohexane. The fraction was dried with a mixture of molecular sieves and alumogel to moisture below 1 ppm by weight. and together with 200 ppm CCl2 and a gas containing 85% by volume of hydrogen in addition to saturated hydrocarbons in mol. A ratio of 1 s 3 was fed under a pressure of 3.5 MPa into a reactor containing a platinum catalyst. Catalyst composition: 0.35% platinum, 5% chlorine on alumina. Isomerization conditions: 2.0 vol. Fraction / vol. catalyst · h, reaction temperature 120 ° C. Table 1 shows the chromatographic composition of the product.

The table shows that methylcyclopentane was virtually isomerized to equilibrium and the product was recovered from the product by redistillation of the n-hexane isolation residue from every 1000 t of product about 30 t of cyclohexane without recycle of methylcyclopentane and over 50 t of recirculation. In practical distillation on a 40-bed column, 92% cyclohexane was recovered as a residue in 90% yield.

Table

Composition of C5 to Cg fraction from petroleum and product

hydrocarbon raw material product butane 3.8 3.8 isopentane 21.3 23.0 n-pentane 32.2 30.5 isohexane 23.2 27.0 n-hexane 12.7 11.9 methylcyclopentane 5.0 2.5 cyclohexane 0.8 3.2 benzene 0.4 0 ^{+ C} 7 ⁺ 0.6 0 olefins according to Br- index mg Br / 100 g 8 1

⁺ according to UV spectrometer - below 10 ppm

Claims (7)

SUBJECT OF THE INVENTION CLAIMS 1. A process for the production of cyclohexane from petroleum naphtha fractions in the simultaneous production of n-hexane concentrates by a combination of rectification, catalytic isomerization and possible methylcyclopentane recirculation, characterized in that the hydrotreated naphtha is petroleum. 30 to 180 ° C, containing below 1 ppm of sulfur, water and nitrogen, is rectified by distillation to a fraction A boiling in the range of 20 to 75 ° C, containing in the mixture of iso- and n-alkanes 2 to 20 wt. methylcyclopentane (I) and cyclohexane (II) in molar ratio I; II 100 to 3; 1, fraction A is optionally additionally mixed with methylcyclopentane concentrate B in wt. a ratio of 100: 1 to 20 per mixture C, which is fed at a temperature of 30 to 150 ° C to a catalyst containing 0.2 to 0.8 wt% platinum on alumina activated 5 to 20 wt%. chlorine at a rate of 1 to 12 vol% of mixture A or C / vol. catalyst per hour, at a pressure of 2 to 10 MPa in the presence of a hydrogen-containing gas in addition to light saturated hydrocarbons with a max. 1 ppm by volume of water at a molar ratio of hydrogen: hydrocarbons of mixture A or C1 to 5; 1 and 1 to 2000 ppm by weight. a carbon atom of a hydrocarbon chloro derivative; chlorine min. 1; 2, the product is then sequentially separated by distillation in three stages into up to C C hydrocarbons together with hydrogen chloride, C ^ hydrocarbons and hydrocarbons, n-hexane concentrate and a mixture of methylcyclopentane and cyclohexane are separated into methylcyclopentane concentrate B, which optionally returns to fraction A, and cyclohexane. , 2. Process according to claim 1, characterized in that fraction A or fraction C contains up to 5% by weight of the composition. benzene. 3. The process according to claim 1, wherein the catalyst preferably contains from 0.3 to 0.45% by weight. % platinum and is activated 3 to 8 wt. aluminum chloride. 4. A process according to any one of claims 1 to 3, wherein the catalyst comprises from 0.01 to 0.8% by weight of water. 5. A process as claimed in any one of claims 1 to 4 _, wherein the hydrocarbon chloro derivative is carbon tetrachloride, trichloromethane or dichloromethane, respectively. hexachloroethane. • G234 481 6. A process according to any one of claims 1 to 5, wherein the hydrogen-containing gas is derived from catalytic reforming of gasolines and contains 60 to 95% by volume of hydrogen. 7. The process of claim 1 wherein the n-hexane concentrate has from about 50% to about 90% by weight. % of n-hexane in addition to 3-methylpentane and methylcyclopentane and the methylcyclopentane concentrate has 50 to 90 wt. methylcyclopentane in addition to n-hexane and cyclohexane. Printed by Moravian Printing Works, Price: CZK 2,40 with operation 12, cl. Lidove milici 3, Olomouc