CS232903B1 - A method of joint processing of distillates from thermal conversion of coal to gasoline - Google Patents

Abstract

The invention relates to petrochemical processing of crude oil and describes a method for co-processing distillates from thermal conversion of coal with gasolines from pyrolysis of hydrocarbons. Distillates from thermal conversion of coal boiling up to 180 °C are catalytically hydrogenated refined, after which the obtained hydrogenate is freed from dissolved gases, possibly C5 hydrocarbons, by distillation and, thus treated, is subjected to dealkylation on a chromium catalyst together with the benzene-toluene-xylene fraction separated from hydrogenated pyrolysis gasoline in a ratio of 1:20 to 20:1, and benzene is separated from the reaction product.

Description

(54) Method for co-processing distillates from thermal conversion of coal with gasolines

The invention relates to petrochemical processing of crude oil and describes a method for co-processing distillates from thermal conversion of coal with gasolines from pyrolysis of hydrocarbons. Distillates from thermal conversion of coal boiling to

180 °C are catalytically hydrogenated refined, after which the obtained hydrogenate is freed from dissolved gases, possibly C ₅ hydrocarbons, by distillation and, thus treated, is subjected to dealkylation on a chromium catalyst together with the benzene-toluene-xylene fraction separated from hydrogenated pyrolysis gasoline in a ratio of 1:20 to 20:1, and benzene is separated from the reaction product.

Λ

The invention relates to a method for co-processing distillates originating from the thermal conversion of coal with pyrolysis gasoline. Thermal processing of coal also processes liquid fractions as by-products, distilling in the range corresponding to gasoline. Depending on the technology used and the quality of the processed coal, these fractions contain valuable aromatic hydrocarbons, which are, however, accompanied by a significant amount of sulfur, nitrogen and oxygen organic compounds and also by a quantity of easily polymerizing unsaturated hydrocarbons.

In the past, a number of demanding technologies were proposed for the use of liquid fractions from thermal processing of coal. The most common were two-stage hydrotreating and the recovery of aromatic hydrocarbons by one of the separation techniques, such as extraction or extractive or azeotropic distillation. These processes are very capital-intensive and have high operating costs. To ensure sufficient economy of these processes, it is necessary to build units with a significant capacity and to process the raw materials, often at great distances from the place of their origin to the place of processing.

In conventional pyrolysis units, pyrolysis gasoline is selectively hydrogenated before the actual hydrotreating. This process usually uses nickel catalysts, which allow the processing of feedstock with only a limited sulfur content (about 0.4% by weight Pd - catalysts and 0.04% by weight Ni - catalysts).

Selective hydrogenation is intended to remove the most reactive, easily polymerizing hydrocarbons and does not allow the removal of sulfur and nitrogen compounds, which cause difficulties during the actual hydrorefining. If, for example, the raw material processed by hydrorefining contains 1,000 mg/1 or more of nitrogenous bases, expressed as NH^, they cannot be completely removed by simple hydrorefining without simultaneously causing the double bonds of aromatic hydrocarbons to be saturated, which is uneconomical and therefore undesirable.

This is because the hydrogenation of nitrogen-containing heterocycles is hindered by their strong chemisorption on the active surface of the catalyst, enabled by the lone electron pair of nitrogen. This property of nitrogen-containing compounds is so strong that they are considered catalytic poisons. Also, ammonia, formed as a reaction product, has an adverse effect on the catalytic effect of hydrogenation catalysts.

This unfavorable behavior of nitrogen heterocycles is mitigated with the severity of hydrogenation conditions, especially with increasing temperature, at which, however, hydrogenation of double bonds of aromatics occurs. The difficulty of processing gasoline fractions from tars is evident from the fact that they can contain up to 3,000 mg/l of nitrogen bases.

The above-mentioned problems are eliminated according to the invention by a method of co-processing distillates from thermal conversion of coal with hydrocarbon pyrolysis gasolines, in which distillates from thermal conversion of coal boiling up to 180 °C are hydrogenated on hydrorefining catalysts, such as cobalt-molybdenum or nickel-molybdenum on alumina, at a pressure of 2.5 to 22.5 MPa, a temperature of 270 to 360 °C in the presence of hydrogen circulating gas at a partial hydrogen pressure of 2 to 18 MPa, and a ratio of circulating gas to raw material of 300 to 1,000 m^. m catalyst space loading 0.3 to 1 m\h ^- liquid raw material per 1 m^ catalyst and in the recycling of hydrogenated distillates to unhydrogenated raw material up to 5, after which the obtained hydrogenate is freed by distillation of dissolved gases, or hydrocarbons up to C 5 and thus treated together with the benzene - toluene - xylene fraction, separated from hydrogenated pyrolysis gasoline, in a ratio of 1:20 to 20:1, is subjected to dealkylation on a chromium catalyst at a pressure of 5 to 6.4 MPa at a temperature of 560 to 640 °C, in the presence of hydrogen circulation gas, at a molar ratio of hydrogen to aromatics of 5 to 10, after which benzene is obtained from the reaction product by rectification.

The advantage of the method according to the invention is that it enables the economical processing of distillates from the thermal conversion of coal with the aforementioned gasolines.

Gasoline fractions from thermal conversion of coal processed according to the invention have, for example, the following composition and properties.

Tar gasoline Rectisol gasoline Density at 20 °C 771 795 kg/ ^m3 Bromine number 26 50.6 Wrists 6 8.6% by weight Pβ resin 100 ml ²² 247 mg Total Sulfur 0.6 1.3% by weight Thiefenic Sulfur 220 520 ppm Nitrogenous bases expressed as NH-j 1,005 92 mg/1 Distillation - the beginning 53 69°C - end 150 160°C Composition - non-aromatics 67.3 47.2% by weight - benzene 9.1 28.4% by weight - toluene 10.1 18.0% by weight - xylene + ethylbenzene 12.1 4.8% by weight - higher aromas 1.4 1.5% by weight The benzene - toluene - xylene fraction of coal conversion has, for example, this composition (BTX fraction) together and properties. processed with gasolines from thermal

Density 832 kg/ ^m3 Total Sulfur 195 ppm Bromine number ' 25.0 Diene number 0.9 Beginning of distillation 76°C End of distillation 149°C Flavors - benzene 36.2% by weight - toluene 19.3% by weight - xylene + ethylbenzene 14.9% by weight - styrene 0.4% by weight C 9 aromatics '6.0% by weight Non-aromatic 23.2% by weight

According to the invention, the gasoline fraction from the thermal conversion of coal with a distillation end of up to 130 °C is subjected to hydrogenation. It is advantageous if they are freshly distilled beforehand and an oxidation inhibitor is added to them in an amount of 0.01 to 0.1% by weight. The inhibitor may be a mixture of dihydric phenols. Other oxidation inhibitors may also be used.

Hydrogenation takes place on a hydrogenation catalyst at a pressure of 2.5 to 22.5 MPa, at a temperature of 270 to 360 °C, at a space loading of 0.3 to 1 a\h”';injection per 1 nP of catalyst in the presence of a circulating gas containing more than 70% mol. hydrogen. The ratio of circulating gas to hydrogenation injection is 500 to 1,000 mjJ . m ^- ^, but it can be higher, especially if it is necessary to reduce the temperature in the catalyst bed, which has increased due to a strongly exothermic reaction.

The hydrogenation catalyst is, for example, a catalyst whose active components are cobalt and molybdenum, or nickel and molybdenum, or nickel, cobalt and molybdenum, or tungsten and nickel, or molybdenum itself on alumina or alumina silicate. A combination of catalysts can be advantageously used, for example a Ni-Co-Mo catalyst with a Mo catalyst, with the molybdenum catalyst being ranked second.

The hydrogenate of the gasoline fraction from the feed is distilled, where hydrogen sulfide is separated together with the distillation gas, or possibly with the light gasoline fraction. Part of the hydrogenate or hydrogenated gasoline can be recycled to the feed in order to improve the hydrogenation of nitrogen bases and reduce the temperature in the catalyst bed, which has increased due to the exothermic reaction during the hydrogenation of unsaturated hydrocarbons.

The ratio of recycles to raw material depends on the composition of the raw material and can be up to 5. Stabilized hydrogenated gasoline is processed by dealkylation in a mixture with the BTX fraction from the pyrolysis of coal hydrocarbons on a chromium catalyst at a pressure of 5 to 6.4 MPa, a temperature of 560 to 640 °C, in the presence of a circulating gas containing mainly hydrogen, at a molar ratio of hydrogen to aromatics of 5 to 10. High-purity benzene containing at least 55.92 Sv by weight of benzene is obtained by distillation of the dealkylated product. The effect of the invention is illustrated by the example.

Example'·'

A mixture of tar gasoline and rectisol gasoline with a distillation end of 160 °C was hydrogenated over a catalyst consisting of a combination of Co-Mo and Mo-catalyst in a 1:1 ratio under the following conditions:

Spray properties

Density 784 kg/pc Total Sulfur 2,000 ppm Thiophenic sulfur 1,800 ppm nitrogenous bases like NHj 307 mg/1 bromine number 17.8 beginning of distillation 56 °C end of distillation 159 °c aromatics. - benzene 20.3 % by weight - toluene 19.5 56 weights - xylenes * ethylbenzene 10.2 56 weights - higher aromatics 1 .0 56 weights

Reaction conditions

Pressure in the reaction space 4.4 to 4.0 MPa

Temperature 270 to 310 °C

Space loads 0.5 m ³ .m ^_3 .h”'

Circulating gas to injection ratio 1,000 m ³ .m ^-3

Hydrogen content in the circulating gas 84 mol %

Hydrogenated gasoline recycle to injection ratio 1

Hydrogenated gasoline was obtained by stabilizing hydrogenates.

Properties of hydrogenated gasoline

Density

Total sulfur

Thiophene sulfur Nitrogenous bases as NH^ Bromine number

Start of distillation End of distillation

795 kg/m ³ 6 ppm <2 ppm <2 ml/1

0.04 76°C 160°C

Aromas

- benzene

- toluene

- xylenes and ethylbenzene

- increases aromas

25.6'% by weight 31.7% by weight 11.3% by weight

1.1% by weight

Non-aromatics

40.3% by weight

Hydrogenated gasoline together with a benzene - toluene - xylene fraction in a ratio of 1:4 was subjected to hydrodealkylation on a catalyst whose active component was chromium trioxide on alumina under the following conditions:

BTX features

Density

Total sulfur Bromine number Start of distillation End of distillation

Aromas

- benzene

- toluene

- xylenes + ethylbenzene

- C 9 aromatics

Non-aromatics

830 kg/m ³ 250 ppm 21.5 75 °C 145 °C

37.5% by weight 20.0% by weight

17.7% by weight 1.0% by weight

23.8% by weight

Λ

Spray properties

Density 802 kg/ ^m3

Total sulfur 200 ppm

Nitrogenous bases as NH^ kl ppm

Bromine number 17.1

Start of distillation 74 °C

End of distillation 1 59 °C

Aromas

- benzene

- toluene

- xylenes + ethylbenzene

- Cg aromatics

35.1% by weight 20.3% by weight

16.2% by weight 1.1% by weight

Mearomatics

27.3% by weight

Reaction conditions

Pressure 6.0 to 5.3 MPa Temperature 570 to 630 °C Spatial device of the catalyst 0.21 m ³ .m" ³ .h" Hydrogen/aromatics molar ratio 8.7 Chemical hydrogen consumption per 1 t spray 22.4 kmol Adiabatic heating 175°C Δ T on reactors 85.6°C

Aromatic conversion in one pass 73%

Benzene yield

64.9% by weight

Quality of benzene produced

Density

Benzene

Toluene

Sulfur

Thiophene

Crystallization Refractive index Bromine number Distillation range

883 kg/m ³ 99.98% by weight 11.0 ppm <1.0 ppm <1.0 ppm 5.48 °C 1.501 1 0.002 7 0.31 °C

Claims (3)

r S e D η i n vy zu zu Process for co-treating distillates from the thermal conversion of coal with gasoline from the pyrolysis of hydrocarbons characterized in that the distillates from the thermal conversion of coal boiling up to 180 ° C are hydrogenated on hydrotreating catalysts such as cobalt-molybdenum or nickel-cobalt-molybdenum catalyst on alumina. at pressure 2.5 to 22.5 MPa, a temperature of 270 to 360 ° C in the presence of a hydrogen circulating gas, at a partial hydrogen pressure of 2 to 18 MPa, a ratio of circulating gas to feedstock of 300 to 1000 mLm ^- spatial load 3-1.3 ⁿ catalyst of 0.3 to 1 m, h of liquid feed per 1 m of catalyst and up to 5 of recycled hydrogenated distillates to unhydrogenated feedstock, after which the hydrogenate obtained is freed from dissolved gases or hydrocarbons to C 5 and treated in this way together with the benzene-toluene-xylene fraction separated from hydrogenated pyrolysis gasoline at a ratio of 1:20 to 20: 1 subjected to dealkylation on a chromium catalyst at a pressure of 5 to 6.5 MPa, at a temperature of 560 to 640 ° C, in the presence of a circulating gas containing hydrogen at a molar ratio of hydrogen to aromatics of 5 to 10, whereupon benzene is obtained from the reaction product by rectification.