CS218948B1 - Process for obtaining mixtures of virtually pure saturated hydrocarbons from petroleum - Google Patents

Abstract

The invention relates to obtaining mixtures of practically pure saturated hydrocarbons from crude oil by a combination of distillation, distillation hydrogenolysis, hydrogenation and superfractionation isolation. The raw material is a saturated hydrocarbon fraction with hydrocarbons with a number of carbon atoms of 5 and 6 or 8, 9 and 10, contaminated with admixtures of olefins, aromatics and with a sulfur content of 10 to 1000 ppm. Hydrogenation processing takes place on a polysulfide catalyst, hydrogen sulfide and water are removed by distillation and aromatics are removed on a dioxide catalyst by further hydrogenation. A hygienically harmless hydrocarbon solvent is obtained.

Description

The invention relates to a process for producing mixtures of practically pure saturated hydrocarbons from crude oil, whereby a combination of distillation isolation, hydrogenolysis and hydrogenation with modified catalysts with final distillation treatment is used for isolation.

Maintaining and improving the environment in all types of human activity is becoming increasingly important and there is a constant pressure to eliminate harmful substances affecting nature and human organisms. In accordance with these trends, technological processes are also being adjusted so that the savings in materials and energy are constantly increasing, i.e., to work with minimum temperatures, pressures and with the most efficient use of all materials, raw materials and catalysts.

One typical example is the ever-increasing need for hygienically safe solvents free from aromatic hydrocarbons and other impurities such as sulphur compounds or unsaturated hydrocarbons. These hydrocarbon mixtures are suitable for technological processes with sensitive catalysts and for removing impurities, especially oily ones, from the surfaces of various devices where people come into contact with their vapours or with the liquid phase.

There are a number of known processes for obtaining such solvents containing predominantly saturated hydrocarbons. The processes are demanding, above all, on energy and on the quality of the raw material. For example, saturated hydrocarbons are isolated on molecular sieves, by solvent extraction, or by multi-stage catalytic processes; however, the purification efficiency is often not at the desired level. For example, hydrocarbon mixtures contaminated with even tenths of a percent of aromatics or olefins are obtained, and the energy consumption, especially steam and liquid or gaseous fuels, is high.

The invention represents a new method for the improved production of mixtures of practically pure saturated hydrocarbons from crude oil, especially C6 to C10 alkanes and/or cyclanes by a combination of distillation, hydrogenolysis, hydrogenation and superfractionation isolation, and consists in isolating from crude oil by distillation a fraction containing predominantly saturated hydrocarbons of the same hydrocarbon number, contaminated with 50 to 5000 ppm of olefins and 0.5 to 20 wt. % of aromatics and 10 to 1000 ppm of sulfur bound in organic compounds, especially in thiophenic or mercaptan types. The mixture is first stripped of sulfur, olefins and part of the aromatics by pressure hydrogenation on a highly active polysulfide catalyst, then of hydrogen sulfide and part of the water by distillation under a pressure of 0.1 to 0.5 MPa and then stripped of the aromatics on an active and stable bimetallic catalyst by hydrogenation under pressure in an ultra-dry environment with gas humidity below 5 ppm vol. in one to four stages with a gradually increasing inlet temperature. The resulting product is finally treated by redistillation on a column with 30 to 100 theoretical plates. The same carbon number of the raw material and then the product can be 5 or 6, or 8 or 9 or 10. The highly active polysulfide catalyst for hydrogenolysis and hydrogenation consists of molybdenum disulfide and non-stoichiometric cobalt or nickel sulfides of the general formula Me _x S _y , where Me is nickel or cobalt and x is greater than y, on the gamma ahimine. In this case, high activity of the polysulfide catalyst is achieved by heating the metal oxides on the said support in a stream of a mixture of hydrogen and hydrogen sulfide under a pressure of 1 to 4 MPa gradually from 20 ^° C to 250°C to 450°C, preferably 350°C to 400 ^° C.

In the hydrogenation stage, the process is characterized by the presence of a bimetallic dioxidic catalyst containing platinum and rhenium on alumina with titanium dioxide, the high activity and stability of which for the process is achieved by heating under a pressure of 1 to 4 MPa in the temperature range of 350 to 520 °C successively with nitrogen, hydrogen and again hydrogen, finally in the presence of carbon disulfide. A preferred embodiment of the hydrogenation consists in the circulation of hydrogen gas through a layer of a desiccator, especially an aluminogel at normal temperature and under a pressure of 0.2 to 5.0 MPa. Both subsequent catalytic processes are carried out at a pressure of 1.0 to 5.0 MPa, with temperatures of 220 to 450 °C, an hourly liquid space velocity of 0.5 to 0.8 vol/ /vol, a volume ratio of gas to raw material of 50 to 5000 1 vol.: 1 being maintained in hydrogenolysis and at 100 to 350 °C, an hourly liquid space velocity of 0.5 to 2.5 vol/vol and a volume ratio of gas to raw material of 500 to 2000 : 1 in the post-hydrogenation. The final stage is the redistillation of the products on a column of 30 to 100 theoretical plates. The procedure is carried out so that the final product has, for example, more than 80 wt. % n-hexane, less than 0.1 wt. % benzene, less than 0.01 wt. % olefins and below 1 ppm S or has more than 99 wt. % of alkanes and cyclanes of Cs to C10, less than 0.1 % by weight of olefins and less than 0.5 % of aromatics:

The process according to the invention has a number of advantages over other processes, some of which are worth explaining in more detail.

The process according to the invention uses practically complete reforming lines with previous and subsequent distillation treatment. In doing so, it successfully starts from oil fractions with a wider distillation cut (range 30 to 250 °CJ) than required by the finished product and with a relatively high content of impurities. The most important components of the process are the catalysts and conditions of both catalytic stages; these are the processes used in the reforming unit for other raw materials, especially for wide gasoline fractions. The highly active treatment of the hydrogenolytic and hydrogenation catalyst allows the least energy-intensive to be selected from a wider range of conditions: lower pressure, lower circulation and high volume velocity.

The main feature is the high dryness of the dehydrogenation environment and the method of achieving it. The products are suitable, for example, as a hexane solvent for polymerization reactions or as a non-aromatic solvent in the cleaning of metal and non-metal objects and equipment.

The examples give practical compositions of raw materials, catalysts and conditions from the full scope of the invention as typical.

Examples

A fraction boiling between 65 and 85 °C was isolated from the crude oil, the composition of which is given in Table 1, and a fraction boiling between 130 and 180 °C, the composition of which is given in Table 2.

Impurities were removed from both fractions by hydrogenolysis and hydrogenation under the following conditions:

Catalyst

Hydrogenolysis of 12% MoOs- 3.5% CoO on alumina

Hydrogenation

0.30% Pt and 0.30% Re on alumina with 0.15% TiOz

pressure ‘MPa) 3.0 2.0 LHSV*) (hi) 4.0 1.5 gas ratio sur; (vol.) 100 :1 1000 : 1 temperature (°C) 300 180

*) LHSV = liquid hourly space velocity

Tables 3 and 4 show the intermediate products after each stage from both raw materials, and Tables 5 and 6 show the quality of the finished products treated by distillation.

Experiments show that it is possible to prepare highly pure products from crude oil under relatively mild conditions with catalysts whose metal content, especially in the dehydrogenation stage, has been reduced to a technically acceptable minimum.

Compared to previous processes (combination of distillation, high-pressure hydrogenation and extraction or combination of inefficiently activated catalysts in the unit), the following was achieved:

— a cleaner product by up to 1 order of magnitude, especially in the content of aromatics and olefins, — reduced energy consumption by 20 to 30%. The improved product gave further advantages in subsequent processes and applications in terms of saving sensitive polymerization catalyst and in improved hygienic conditions when using a heavier solvent.

TABLE 1

Characteristics of light oil fraction dzo 0.698

Br. index 150 mg Br/100 g benzene 1.1 % wt. toluene 1.0 % wt. distillation curve — beginning 63 °C 10% vol. 71 °C 30% vol. 73 °C 50% vol. 76 70% vol. 80 90% vol. 87 95% Order 90 QQ end 96 sulfur 50 ppm

TABLE 2

Characteristics of heavy gasoline fraction

d20 0.729 Br. index 2000 mg Br/100 g aromatics 1.8 % wt. distillation curve — beginning 143 °C 50% vol. 150 °c 98% vol. 165 °C end 171 CQ sulfur 1 ppm

TABLE 3

Intermediates from light Inaction after individual stages according to the invention

Intermediate degree hydrogenolytic hydrogenation Br. index (mg Br/100 g) 96 5 benzene + toluene (% wt.) 1.8 0.005 S (ppm) under 1 under 1

TABLE 4 Intermediates from the heavy fraction after the individual stages according to the invention hydrogenation ¹ Intermediate degree hydrogenolytic Br. index (mg Br/100 g) 130 5 aromatics (% wt.) 1.7 0.1

TABLE 5 Quality of the finished product from the light fraction st. of ordinary ‘production Carbon number 6 Br. index (mg Br/100 g) under 10 50 —100 aromatics (% by weight) below 0.01 0.1— 0.2 S (ppm) from 1 under 1 TABLE 6 Quality of the finished product from heavy faction Carbon number 9 + 10 current production Br. index (mg Br/100 g) under 10 200 —300 aromatics (% wt.) below 0.1 0.8— 1.8

subject

Claims (6)

A process for obtaining a mixture of virtually pure saturated hydrocarbons from petroleum by a combination of distillation, distillation hydrogenolysis, hydrogenation and superfractionation isolation, characterized in that the desired fraction containing predominantly saturated hydrocarbons of the same carbon number contaminated from 50 to 5000 ppm olefins and 0.5 to 5 ppm 20 wt. aromatics and 10 to 1000 ppm of sulfur bound in organic compounds, in particular thlophenic or mercaptan types, the mixture is first dehumidified by sulfur, olefins and part aromatics by hydrogenation on a highly active polysulfide catalyst, hydrogen sulfide and part water by distillation under a pressure of 0.1 to 0; 5 MPa and then the aromatic residue on the highly active and stable bimetallic dioxidic catalyst by hydrogenation under pressure in an environment with a gas humidity below 5 ppm by volume in one to four stages with gradually increasing inlet temperature followed by redistillation on a 30 to 100 theoretical tray column. 2. The method of claim 1, wherein: OF THE INVENTION the same carbon number of the hydrocarbon is 5 or 6, optionally 8 or 9 and 10. 3. The process of claim 1 wherein the highly reactive polysulfide catalyst is comprised of molybdenum disulfide and non-stoichiometric cobalt or nickel sulfides of the formula Me _x S _y , wherein Me is nickel or cobalt and x is greater than y, on gamma alumina, the polysulfide catalyst is achieved by heating the metal oxides on said support in a stream of hydrogen-hydrogen sulfide under a pressure of 1 to 4 MPa successively from 20 ° C to 250 ° C to 410 ° C, preferably 350 to 400 ° C. 4. The process of claim 1 wherein the bimetallic dioxidic catalyst comprises platinum and rhenium on alumina with titanium dioxide and the high activity and stability is achieved by heating under a pressure of 1-4 MPa and in the temperature range of 350-520 ° C sequentially with nitrogen, hydrogen, air and hydrogen again, finally in the presence of carbon disulphide in the temperature range of 350 to 520 ° C. 2 1 8 N 4 8 5. Process according to claim 1, characterized in that the circulating hydrogen gas during the hydrogenation is exclusively passed through a layer of desiccator, in particular alumogel, at a temperature of 0 to 30 [deg.] C. and under a pressure of 0.2 to 5 bar. 6. The process of claims 1, 3 and 4 wherein hydrogenolysis maintains temperatures of 220-450 [deg.] C., a pressure of 1.0-5.0 MPa, an hourly liquid space velocity of 0.5-0.8 v / v, and the volume ratio of gas to feedstock is 50 to 5000: 1 and in hydrogenation the inlet temperatures are 100 to 350 ° C, the pressure is 1.0 to 5.0 MPa, the hourly space velocity of the liquid is 0.5 to 2.5 vol / vol and the volume ratio 500 to 2000: 1 vol.