SU789463A1 - Method of isopropylbenzene production - Google Patents

Description

(54)

METHOD FOR PRODUCING ISOPROPYLBENZENE

one

This invention relates to petrochemical processes for the alkylation of aromatic hydrocarbons with olefins in the presence of an AtCf-based catalyst. and aims at improving the benzene recycling system and the conditions of the alkylation process itself.

Aluminum chloride has long been used as a catalyst in the alkylation of aromatic hydrocarbons with olefins. Typically, the amount of catalyst used is by weight, based on benzene or an aromatic hydrocarbon, and includes both fresh and a return catalyst, which results from the formation of sludge and. catalyst recycle to cracking, dehydrogenation and other undesirable reactions.

Therefore, improved synthesis processes have been created, a characteristic feature of which is to conduct the reaction using a certain soluble amount of catalyst in one pass, i.e. without sedimentation and catalyst recycling, but using higher molar ratios (up to 4: 1) ol "fin: benzene, significant product residence time in the alkylation zone (1-3 hours) and higher temperatures (up to 1302PO), which significantly reduces the effect of reducing the concentration of Afct in the reaction zone l.

The closest to the proposed technical essence and the achieved result is the method of obtaining isopropyl benzene by azeotropic distillation of technical benzene with separation of the hydrocarbon fraction from the azeotrope obtained and subsequent alkylation of the remaining benzene with propylene at elevated temperature and pressure in the presence of aluminum chloride. The method regulates the operating conditions of the azeotropic dehydration column of benzene and

20 provides for the return of the hydrocarbon layer after separation of water.

The purpose of the invention is to increase the yield and purity of the target product.

The goal is achieved by

25 that in the method of producing isopropyl benzene by azeotropic distillation of technical benzene with separation of the hydrocarbon fraction from the resulting azeotrope and subsequent alkylization of benzene with yropylene at elevated temperature and pressure in the presence of aluminum chloride, the separated hydrocarbon fraction is fed to the rectification with a selection of istils and aluminum in the presence of aluminum chloride. 7-10 wt.% From the initial hydrofluoric fraction and in the form of the bottom product of benzene, which is fed to the alkylation.

Alkylation is carried out at an EB-IC temperature with and at a pressure of 0.41, 0 atm. For 8-14 minutes.

Compliance with the above conditions for the rectification promotes the achievement of the minimum yield of all by-products (and most importantly, the minimum yield of such an undesirable by-product as n-propyl benzene), contributes to maintaining the high catalytic properties of the return complex and reducing the chemical losses of benzene and propylene.

The recirculation system for the return benzene provides for the release of undesirable impurities of non-aromatic hydrocarbons accumulating over time in benzene, especially sulfur compounds (carbon disulfide and thiophene), concentrated in the azeotrope hydrocarbon condensate from the azeotropic distillation column of benzene, as part of the benzene fraction of distilled distillation blender. the hydrocarbon condensate from the azeotropic distillation of benzene serves. This ensures high quality of reusable baseball on carbon disulfide and thiophene, which significantly reduces the yield of propyl, thiophenes in the alkylate (Formed in the alkylation of thiophene with propylene on Atcf-j, provides a high quality of commercial isopropyl benzene in the content of sulfur compounds, and At the same time, due to a decrease in the amount of CSrj in the alkylate, the solubility of Afcf in the latter decreases, reduces the removal of A1C1 "on the decomposition system, as a result, the active catalytic complex is returned to the alkylation process CS, which reduces the total raskhs yes.

The hydrocarbon fraction of the azeotrope from the column of azeotropic dehydration of benzene (bt / h) is fed to the gaseous column / pre benzene fraction. The distillate, wiped from the top of the column, contains non-aromatic and sulfur compounds and some benzene (5-10 wt.%). Benzene, freed from sulfur

and non-aromatic compounds are withdrawn from the bottom of the column.

The degree of extraction of non-aromatic and sulfur compounds is required and is governed by the amount of distillate column drawn from above.

. Changes in the quality of the bottom product of the column and, accordingly, marketable isopropyl benzene (IPB) depending on the amount of distillate taken are presented in Table. one.

As can be seen from the above data, the optimal amount of distillate withdrawn is 7-10% by weight of the feedstock fed to the column. Maintaining distillate selection below 7 wt.%

5 does not provide the required quality of marketable isopropyl benzene for sulfur compounds (GOST organizes 5. S - no more than 0.0002 wt.%), And above 10 wt.% Increases significantly

0 loss of benzene with pre-benzol fraction (30% and higher instead of 5-10% at the proposed selection value).

The change in the content of sulfur compounds in the alkylation of the alkylation plant during the operation of the node for the extraction of the prebenzene fraction and without it is presented in Table. 2

As can be seen from the above data, the use of the output column of the prebenzene fraction makes it possible to obtain high-quality isopropylbenzene in terms of the content of sulfur compounds by reducing the content of the latter in the alkylate and in the recirculating benzene.

 .le respectively 6-7 times and 1820 times.

The effect of the time of benzene propyl alcohol in the presence of Afcfj on the technical, economic and qualitative indicators of the process is presented in Table. 3

J The effect of the conditions for carrying out the process of alkylation of benzene with propylene on the yield in the alkylate and the product API of the main undesirable by-product of n-propylbenzene with a reaction time of 14 minutes is presented in Table. four.

As can be seen from the above data

to ensure the high quality of the alkylate and, accordingly, marketable isopropylbenzene, the content of n-propylbenzene: it should not exceed 0.05 Bes.%.

5 The proposed method allows to obtain highly pure isopropyl benzene with the content of the main substance not lower than 99.92-99.95 wt.%.

Table 1

Vbnzol coal brand pure for nitration, 1.2 grade 0.0005 0.00006 0.0001 Benzene 0.0001 0.000025 0.00006 petroleum

The composition of the alkylate, wt.%: Benzene

ethylbenzene isopropylbenzene

normal propyl benzene

alfa-methyls tyrol butylbenzene polyalkylbenzenes

Content .SS, weight%

.Table 3 0.0004 0.0015 0.00015 0.0005 2

Selectivity, wt.% Consumption And I C 1, kg / t IPB

Content of impurities in commercial isopropylbenole, May, c.%:

ethylbeneol normal propyl Continuation tabl, 3

75.27

78.66 6.5-7.2 4.2-4.5

0.02

0.01

Claims (2)

The claims. = 1. A method of producing isopropylbenzene by azeotropic distillation of technical benzene with separation of the hydrocarbon fraction from the obtained azeotrope and subsequent alkylation of the remaining benzene with propylene pru) elevated temperature and pressure in the presence of aluminum chloride, characterized in that; In order to increase the yield and purity of the target product, the hydrocarbon fraction is fed for distillation with the selection of the pre-benzene fraction in the form of a distillate in the amount of 7-10 wt.% of the initial hydrocarbon fraction and in the form of a cubic benzene product, which is fed for alkylation. 2. The method of pop. 1, characterized in that the alkylation is carried out at a temperature of 95-115 ^about With, a pressure of 0.4-1 ATM for 8-14 minutes