CS217005B1 - A method for obtaining a C7 to C11 alkanic hydrocarbon mixture - Google Patents

Abstract

The invention relates to a method for producing a technically pure mixture of alkane hydrocarbons C? to C1;L, free from cyclic unsaturated hydrocarbons and containing up to 2% unsaturated and aromatic hydrocarbons from crude oil or its distillates, in which the fraction 120 to 220 °C is first distilled from crude oil, which is subjected to hydrorefining, hydrogen sulfide is removed from it by distillation and then brought into contact with a reforming catalyst in 3 stages at gradually increasing temperatures, the reforming product is extracted with diethylene glycol, the resulting raffinate is redistilled and further refined by percolation or hydrogen refining on a platinum-rhenium catalyst. The product is suitable as a medium for a liquid photoelectric developer.

Description

The invention relates to a process for producing a technically pure mixture of C1 to C2 alkyl hydrocarbons by a combination of crude refining processes from petroleum fractions containing higher concentrations of cyclic and aromatic hydrocarbons.

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Alkenyl hydrocarbon mixtures containing practically unsaturated hydrocarbons, aromatics or cyclane hydrocarbons have so far had to be prepared synthetically by a combination of polymerization and hydrogenation or alkylation of olefins and olefins, which are economically demanding processes and require the construction of new facilities. It is also possible to start from the raffinate remaining after the extraction of aromatics from a mixture of aromatics with non-aromatics, which originate from catalytic reforming or pyrolysis gasoline. However, the contents of higher alkane hydrocarbons are small and, in addition, they are contaminated with higher concentrations of residual cyclanes originating from lower fractions and relatively resistant to dehydrogenation. Such mixtures are in great demand in various fields, especially where hygienic safety, very high electrical resistivity, low dissolving power for polymeric materials and the ability to peptize for dispersion systems are required. A typical use is, for example, a liquid for electrophotography, where ee requires practically all of the above properties.

The invention solves the production of a mixture of hydrocarbons from crude oil or its fractions in a conventional refining plant, in which the arrangement of conditions ensures the maximum yield of C? to ^C 11 alkanes and minimal contamination with aromatics, olefins and cyclanes. The process consists in that the crude oil fraction is hydrotreated at temperatures of 90 to 220 °C, preferably 135 to 185 °C,

280 to 330 °C under a hydrogen pressure of 1.0 to 5.0 MPa with a space velocity of 2 to 8 vol.

-1—1 vol. h on a catalyst containing 8 to 15 wt. % MoO^ and 2 to 6 wt. % cobalt and/or nickel oxides, is freed from dissolved hydrogen sulfide by distillation, then brought into contact with a reforming catalyst containing platinum and rhenium on alumina, namely 0.25 to 0.40 wt. % each of the metals, 0.1 to 1.5 wt. % halogen, especially chlorine, and 0.05 to 2 wt. % of titanium oxide, in three stages at a gradually increasing inlet temperature in the range of 450 to 500 °C and under a pressure of up to 3.0 MPa, with a space velocity of up to 2 vol. vol. ^-3- h ^-1 and with a molar ratio of hydrogen to hydrocarbons preferably higher than 5 5 1, while the inlet temperatures on the individual catalyst layers are maintained at an increasing rate of 2 to 15 °C, preferably 5 to 10 °C. Dissolved butanes are then removed from the reforming product ae by distillation, after which ee is extracted with diethylene glycol at a temperature of 150 to 220 °C with a volume ratio of raw material and extraction agent of 1 : 10 to 1 : 50 vol., from the resulting raffinate a fraction of 100 to 220 °C, preferably 140 to 175 °C is obtained by redistillation.

This alkane fraction can then be advantageously freed from residual olefins by percolation on clay at 150 to 250 °C, with a space velocity of 0.5 to 4.0 vol. vol. ^-1 h ^-1 and at a pressure of 1.0 to 3 MPa, or from olefins and aromatics by transfer over the above-mentioned platinum-rhenium catalyst at a pressure of 1.0 to 5.0 MPa, a temperature of 100 to 250 °C and a space velocity of 1 to 2.5 vol. vol. ^-1 h ^-1 .

The main features leading to the highest purity of the product and its highest yield, which also distinguish the invention from the usual conditions of refinery processes, are primarily

217 005 selection of the distillation fraction, especially in the specified suitable distillation range of 135 to 185 °C, which ensures that intermediate products of conversion of higher-boiling and/or lower-boiling fractions do not pass into the product during catalytic processes, e.g. hydrocracking, disproportionation, etc., further conditions for hydrorefining, which show that a hydrorefining product with a minimum concentration of olefins is obtained, with the lower part of the temperature range being preferred. The essence of the procedure is the use of the reforming process to obtain a product without cyclanes with a low concentration of olefins and with maximum preservation of the desired alkanes, which under usual reforming conditions are very easily hydrocracked to lower-boiling alkanes and dehydrocyclized to aromatics. Adjustments of all parameters serve this purpose: the reduction of olefins is achieved by an increasing temperature regime and an increase in the partial pressure of hydrogen given by increased circulation. Relatively low temperatures mean that the only reaction is the dehydrogenation of cyclohexanes and the dehydroisomerization of cyclopentanes to aromatics, which is also accelerated by the reduced pressure in the system. The catalysts used in both catalytic stages of the process guarantee the highest effect in the desired directions of reactions: low hydrotreating temperature and stability of the reforming process even with hydrocarbons boiling above 180 °C, which are significantly more susceptible to coking.

No less important are other physical isolation stages, where the advantage of diethylene glycol is used to almost completely extract the less polar C aromatics from the reforming product with a significant range of extraction ratio and temperature. However, it is not possible to achieve such an effect that the extraction product alone, free from light fractions, would be suitable as a product. A difference in extraction efficiency was found for c ₉ and σ _1θ aromatics. The latter remain more in the raffinate. Therefore, redistillation is necessary, in which the aromatics are removed to the residue and an alkane-rich cut free from aromatics is obtained.

If the process is carried out under the optimal combination of conditions, the concentration of alkanes is 98 to 99 wt. % and the remainder is cyclanes, olefins and aromatics. Complete removal of olefins and aromatics can optionally be carried out advantageously either by hydrogenation or adsorption (for olefins). The invention includes the advantageous use of a Pt-Re catalyst. Of the clays, natural clay used in the range of 0.1 to 0.5 mm for the purification of oils or aromatics is suitable. The product is then suitable for the most demanding use in the most adverse operating conditions.

The process implicitly includes the fact that the removal of cyclanes from the raw material by reforming is achieved by choosing the maximum temperatures, because under usual reforming conditions new cyclanes appear in a concentration of up to 3% by weight, which is then about 6 to 8% by weight in the raffinate. The low temperature in the 1st reaction layer, which is about 1/7 of the total catalyst, causes a reduction in the olefin concentration by up to 1/3.

The following example shows the procedure under selected conditions corresponding to the subject matter of the invention.

217,005

Example ’

By the process according to the invention, a Cg-O^Q alkanoic liquid suitable as a liquid for electrophotography was produced - with a flash point of 32 °C, a distillation range of 145 to 169 °C, a content of 0.3 wt. % aromatics, practically free of cyclanes and an 8 Br-number of 1.2 Br/100 g (0.6 wt. % olefins).

For production, a petroleum fraction of 130 to 210 °C is used, which is then fed to a hydrotreating and catalytic reforming unit, where sulfur is first removed and then the cyclanes are converted into aromatics.

Conditions:

hydrotreating catalyst - Mo-Ni-Co oxides (12%, 2% - 2%) on alumina pressure - 3.5 MPa temperature - 310 °C

LHSV - 3.5 h" ¹ reforming catalyst - Pt-Re on alumina (0.32 and 0.32% wt., 0.7% Ol and 0.15% TiOg) pressure - 2.5 - 2.8 MPa

LHSV - 1.8 h ¹ circulation 5.5 : 1 molar (Hg : CH) inlet temperatures - 475/480/482.°C

Between both stages there is a redistillation column, where hydrogen sulfide and residual water, and possibly light hydrocarbons, are distilled off under a pressure of 0.2 MPa.

Change of composition during these marches:

type file hydrocarbons aromatics olefins cyclanes alkanes. With ppm dest.no.°G raw material 15.0 0.3 25.0 59.7' 100 130 to 210 after hydrosfiliation 15.0 0.03 25.0 59.7 2 120 to 210 after reformation 45.0 0.6 0 54.4 1 40 to 225 Product reforming is extracted with diethylene glycol in a mass ratio of 1 : 20 at 180 °C and a pressure of 1.5 MPa and to raflnát ee redistills to 2 stills columns so that

in the 1* column, the fraction up to 135 °C and the residue are distilled off. This is sent to a second distillation, where the Cg-C^Q fraction of the composition stated at the beginning of the example is obtained, the residue contains about 15 wt. % aromatics 0^0+·

217,005

Characteristics of redistillation products: 50% point 95% point end dest, °C d 20% beginning of dest. remainder of the 1st column 141 154 176 209 0.722 100 distillate from the 2nd round 145 150 159 169 0.727 80 remaining from round 2. 169 175 .193 243 0.779 20

In the usual procedure from the broad fraction (100 to 180 °C) without using the conditions of the invention, ^9-^0 frekoe with 4 to 8 wt. % cyclanes, 1.2 to 1.8 wt. % aromatics and also the Br-number is about a third higher (1.8 g Br/100 g) than in the product obtained according to the invention is obtained. In the usual procedure, it is necessary to process 120% more gasoline than in the procedure according to the invention to obtain the same amount of fraction θ9θιθ*

Since the olefins produced during production are concentrated in the raffinate, they were removed by filtration on percolating clay at 200 °C to 90% of the breakthrough value. In parallel, hydrogenation removal was also tested at 225 °C and under a pressure of 3.5 MPa and the removal of aromatics below 0.01% by weight of olefins was achieved practically completely (Br number*0.001).

217 005

Claims (6)

object of the invention 1. A process for obtaining a mixture of alkane hydrocarbons C? % to _C11 , especially C8 and _C10 , practically free of cyclic saturated hydrocarbons and with concentrations of unsaturated and aromatic hydrocarbons up to 2.0 wt. or a fraction thereof, characterized in that the petroleum fraction 190 to 220 ° C, preferably 135 to 185 ° C, is successively contacted with the hydrotreating catalyst at temperatures of 280 to 330 ° C under a hydrogen pressure of 1.0 to 5.0 MPa and volumetric velocities of 2 to 8 v / v ¹ h ^-1 , freed from hydrogen sulphide by distillation, and then contacted with a platinum and rhenium alumina reforming catalyst in three stages at successively increasing inlet temperatures ranging from 450 to 500 ° C and under pressure up to 3.0 MPa and volume velocities up to * 1 - 1 2 v / v and having a molar ratio of hydrogen to hydrocarbons preferably greater than 5 ·· 1, the reforming product is extracted after distillation of dissolved butanes by diethylene glycol at a temperature of 150 to 220 ° C with a volume ratio of raw material and extracting agent 1 with 10 to 1: 50, a fraction of 100 to 220 ° C, preferably 140 to 175 ° C is obtained by redistillation from the resulting raffinate. 2. A process according to claim 1, characterized in that the petroleum fractions blended contain from 25 to 25% 40 wt. % of cyclanes and 5 to 20% by weight of aromatics. s · 3. The process of claim 1 wherein said hydrotreating catalyst comprises from about 8% to about 15% by weight. % MoO 2 and 2 to 6 wt. cobalt and / or nickel oxides in a ratio of 2: 1 to 1: 2. 4. The process of claim 1 wherein said platinum-rhenium catalyst comprises from about 0.25% to about 0.40%. % of each metal and activated from 0.1 to 1.5 wt. % of halogen, especially chlorine, and titanium oxide in a concentration of 0.05 to 2 wt. Process according to Claims 1 and 4, characterized in that the inlet temperatures on the individual catalyst layers during the reforming are maintained ascending at 2 to 15 ° C, preferably 5 to 10 ° C. 6. The method of claim 1, wherein the fraction obtained from 100 to 220 ° C percolated on clay at 150 to 250 ° C with a space velocity of 0.5 to 4.0 vol. Vol. ^"1 h" ¹ and at a pressure 1.0 to 3.0 MPa or transfer via the above platinum-rhenium catalyst at a pressure of 1.0 to 5.0 MPa and a temperature of 100-250 ° C and a space velocity of 1 to 2.5 h ^_1.