CS243166B1 - Method of tar rectisoled petrol treatment - Google Patents

Abstract

A method for upgrading tar rectisol gasoline by catalytic selective hydrogenation with subsequent cracking to benzene, in which rectisol gasoline is refined in a mixture with pyrolysis gasoline in a ratio of 0.5 : 99.5 to 10 : 90 on a catalyst containing as active components rare metals of Group VIII of the Periodic Table on active alumina, at a temperature of 50 to 200 °C and a pressure of 2 to 6 MPa, with 80 to 95% of the liquid product of selective hydrogenation being recycled and the remainder being subjected to distillation to obtain a concentrate of aromatics Cg to Cg, which is catalytically cracked to benzene

Description

(54) A method for treating tarry rectisol gasoline

Process for evaluating tar rectisol gasoline by catalytic selective hydrogenation followed by cleavage to benzene, wherein the rectisol gasoline is refined in a mixture with pyrolysis gasoline in a ratio of 0.5:: 99.5 to 10: 90 on a catalyst containing noble metals VIII as active ingredients. of the periodic system on active alumina, at a temperature of 50 to 200 ° C and a pressure of 2 to 6 MPa, whereby 80 to 95% of the liquid product of the selective hydrogenation is recycled and the residue is subjected to distillation to obtain a Cg to Cg aromatic concentrate which is catalytically breaks down into benzene.

The present invention relates to the treatment of rectisol gasoline resulting from the pressure gasification of coal into generator gas.

This gasoline is scrubbed from the cooled crude generator gas with supercooled methanol along with hydrogen sulphide and carbon dioxide; it consists of the lower-boiling tar fractions formed in the carbonization zone of the pressure generator.

Until now, this rectisol gasoline has been further recovered together with tar gasoline distilled from low temperature tar boiling to about 220 ° C, from which the contained monovalent phenols Cg to Cg were isolated. For example, a blend of phenolized tar gasoline and rectisol gasoline is hydrotreated and further utilized in fuel production.

It is also proposed to mix the mixture after hydrotreating or fraction up to 180 ° C with the benzene-toluene-xylene (BTX) fraction from selectively refined pyrolysis gasoline and further catalytically cleave to benzol. The disadvantage of this process is that mixing the rectisol gasoline with the tar reduces the aromatics content compared to the content in the rectisol gasoline itself, and a further reduction occurs when the hydrotreating of the mixture is separated in order to refine the nitrogen compounds. The resulting relatively high non-aromatic content is then adversely affected by catalytic resolution in a mixture with the BTX fraction to benzene.

It has now been found that rectisol gasoline obtained in pressurized gasification plants, coal-gasifying coal-free coal gasoline, is advantageously selectively hydrotreated directly in admixture with pyrolysis gasoline and further cleaves the obtained raffinate or benzene-toluene-xylene fraction into benzene, and; catalytically or thermally.

Typically, the amount of rectisol gasoline produced is considerably less than the amount of pyrolysis gasoline produced in the high capacity pyrolysis unit for pyrolysis of primary petroleum gasoline, kerosene and atmospheric gas oil, and thus the addition of rectisol gasoline only partially influences the resulting blend. However, the addition of rectisol gasoline to pyrolysis gasoline is economically very advantageous.

Both gasolines - pyrolysis and rectisol - have similar characteristics in that they contain unstable, easily polymerizing moieties, characterized as a diene number.

These unstable fractions must be removed before further processing. As has been verified, the rectisol gasoline can be selectively hydrogenated in a mixture with pyrolysis gasoline to a device that is a conventional part of a pyrolysis unit.

The process of evaluating tar rectisol gasoline by catalytic selective hydrogenation followed by cleavage to benzene is according to the invention in that the rectisol gasoline is selectively refined in a mixture with pyrolysis gasoline in a ratio of 0.5: 99.5 to 10: 90, preferably in a ratio of 3: 97 to 6: 94 on a catalyst containing noble metals as active ingredient VIII. groups of the periodic system, in particular palladium, deposited on active alumina, at temperatures of 50 to 200 ° C, pressure of 2 to 6 MPa, whereby 80 to 95% of the liquid selective hydrogenation product is recycled and part of the feedstock, 20 to 5 S, is distilled to give a aromatic concentrate of Cg to Cg, which is catalytically cleaved to benzene. The selective hydrogenation is carried out in the liquid phase.

The catalyst is charged into an adiabatic reactor in a fixed bed; selective refining is exothermic, and to increase the reaction temperature to be slow and uniform, it is added to the fresh feed as a diluent circulating the selectively refined product. At the inlet of the hydrogenation reactor, the feed temperature is maintained. mixed feed is usually in the range of 50 to 200 ° C, depending on the activity of the loaded catalyst.

The activity of the catalyst used is gradually reduced by the deposition of polymeric and resinous substances on its surface. The reduction in catalyst activity is counteracted by gradually increasing the feed temperature; this is achieved by less cooling the recycled selective hydrogenation product.

When the upper limit of the working temperature of the filled catalyst, e.g. 150 to 200 ° C, then the charged catalyst is oxidatively reactivated with a mixture of air and water vapor.

As has been found, the addition of rectisol gasoline to pyrolysis gasoline does not result in a forced change in reaction conditions. Nor is it necessary to increase the excess hydrogen required for the selective hydrogenation of dienes, styrene and other substances.

A portion of the selectively hydrogenated product distills off the aromatic concentrate Cg to Cg, which is thermally or catalytically cleaved to yield benzene.

The addition of rectisol gasoline does not adversely affect the quality indicators of the benzene produced. Rectisol gasoline can also be desulphurized with monoethanolamine prior to admixture and reduced the sulfur content by 30 to 50%. For example, refining rectisol gasoline with a 10% MEA solution (1: 1 ratio, for 5 minutes) reduces the sulfur content by 36.5%.

The course of selective hydrogenation of rectisol gasoline in a mixture with pyrolysis gasoline is evident from the example.

Example

28 t / h of pyrolysis gasoline were injected into a hydrogenation reactor filled with 16 t of hydrotreating catalyst (0.3% Pd on alumina), from which the pyrolysis Cg fraction and 300 t / h of selectively hydrogenated recycle were separated by distillation.

To this feed is added 1.65 t / h of rectisol gasoline; at the same time about 500 kg of hydrogen containing about 4% methane is metered in. The working pressure is maintained at 4.2 MPa. The mixed feed temperature is gradually increased from about 50 ° C to about 120 ° C.

Added rectisol gasoline for the following characteristics:

density at 20 ° C 0.809 rain. curve distillation start 68 ° C 25% 86 ° C 50% 96 ° C 75% 115 ° C end of distillation Mp 162 ° C benzene content 30% toluene content 19% xylene content 4.5% bromine number 56 dienové číslo 2.1 The sulfur content of the ppm varies, e.g. 12 570 organic base content mg / l 1.7

Claims (1)

OF THE INVENTION Process for the treatment of tarry rectisol gasoline by catalytic selective hydrogenation followed by cleavage to benzene, characterized in that rectisol gasoline is selectively refined in a mixture with pyrolysis gasoline in a ratio of 0.5: 99.5 to 10: 90, preferably in a ratio of 3: 97 to 6-i. 94 on a catalyst comprising noble metals VIII, groups of the periodic system, in particular palladium deposited on active alumina at temperatures of 50 to 200 ° C, at a pressure of 2 to 6 MPa, 80 to 95% of the selective hydrogenation liquid product being recycled; in an amount of 20-5% was subjected to distillation and is obtained from the aromatics concentrate C _g to C, that is catalytically cleaved to benzene. Severography, n Price 2,40 Kčs