RU2178398C1 - Method of synthesis of olefinic hydrocarbon - Google Patents

Abstract

FIELD: petroleum chemical industry, chemical technology. SUBSTANCE: paraffin hydrocarbons are dehydrogenated in the presence of catalyst of the following composition, wt. %: Cr₂O₃, 10.0-30.0; ZnO, 30.0-45.0; and Al₂O₃, the balance. After dehydrogenation stage catalyst is fed to regeneration and reduction stages that are performed at temperature from 640 C to 700 C, under atmosphere pressure, slightly less or above of atmosphere pressure, at volume gas rate from 40 to 60 h^-1 and residence time of catalyst in reductive zone from 1 to 3 min. EFFECT: enhanced effectiveness of process, increased yield of end product. 4 cl, 1 tbl, 4 ex

Description

The present invention relates to the field of producing olefinic hydrocarbons, in particular C ₂ -C ₂₀ olefinic hydrocarbons, by dehydrogenation of the corresponding paraffin hydrocarbons.

 Known methods for producing olefin hydrocarbons by dehydrogenation at elevated temperatures of the corresponding paraffinic hydrocarbons in the presence of noble metal catalyst compositions (US Pat. Nos. 3,531,543, 4,786,625, European Patent No. 3,51067), and also based on metal oxides in the presence of promoters, in most cases it is supported oxide chromium (US patent N 2945823, 2956030, 2991255 and British patent N 2162082). However, both groups of these compositions have disadvantages. Compositions based on noble metals require special treatment at the stage of regeneration in order to maintain the activity of noble metals, for example, treatment with chlorine-containing substances, followed by reduction (US patent N 4438288). Compositions based on chromium oxide deposited on alumina, silica, alumina - silica, etc., have insufficient selectivity and activity.

Closest to the proposed is a method for producing olefinic hydrocarbons by dehydrogenation of the corresponding paraffinic hydrocarbons in the presence of a catalyst composition, wt. %:
Cr ₂ O ₃ - 6.0-30.0
SnO - 0.1-3.5
Me ₂ O - 0.4-3.0
SiO ₂ - 0.08-3.0
Al ₂ O ₃ - Else
The dehydrogenation process is carried out at a temperature of from 450 to 800 ^o C, a pressure of from 0.1 to 3 atm abs. and space velocity from 100 to 1000 hour ^-1 . After dehydrogenation, the catalyst is regenerated and then hexavalent chromium compounds formed on it are restored (RF Patent N 2127242, 03/10/99, Bull. No. 7). The olefin yield in this method is not high enough. In addition, significant reducing agent costs are required. This is explained as follows. The content of hexavalent chromium compounds from 2 to 3 wt. % in fresh and not less than 0.45-0.6 wt. % of the catalyst from the dehydrogenation system. With a decrease in the concentration of hexavalent chromium compounds to 0.45 wt. % and less dehydrogenation indices drop. After regeneration, before being fed to the reactor, the catalyst is preliminarily reduced in a special apparatus. This operation is necessary, because otherwise hexavalent chromium compounds, which are a very strong oxidizing agent, will be restored by oxidizing the hydrocarbon supplied to dehydrogenation. At the same time, selectivity will be significantly reduced. Typically, natural gas or, less commonly, vapors of raw materials are used for reduction (this is better since less water is formed during recovery, but more expensive).

CH ₄ + CrO ₃ ⇒ CO ₂ + CO + H ₂ O + Cr ₂ O ₃
Catalyst recovery in industry is carried out with methane or n-butane vapors for 1-3 min at a space velocity of 100-300 h ^-1 (Industry SK, TsNIITEneftekhim, M., N 2, 1971, 1-3, AC N 134693, 1959, BI. N 15, 1963).

 After recovery, the catalyst is desorbed with nitrogen to remove the products of combustion - carbon dioxide and water, which is a catalytic poison. The problem solved by the present invention is to increase the efficiency of the process for producing olefinic hydrocarbons.

A method for producing olefinic hydrocarbons by dehydrogenation of the corresponding paraffinic hydrocarbons in the presence of a catalyst composition, wt. %:
Cr ₂ O ₃ - 10.0-30.0
ZnO - 30.0-45.0
Al ₂ O ₃ - Else
After the dehydrogenation step, the catalyst is sent for regeneration and reduction, which is carried out at a temperature of from 640 to 700 ^o C, atmospheric, slightly lower or slightly higher atmospheric pressure (0.95-2.1 atm abs.), Gas volumetric velocity from 40 to 60 hour ^-1 and the residence time of the catalyst in the recovery zone from 1 to 3 minutes. The inventive process can be used for any dehydrogenation technology in a fixed, fluidized or moving catalyst bed.

Preferred are the following embodiments of the new method:
- dehydrogenation, regeneration and recovery is carried out in a fluidized bed of catalyst;
- dehydrogenation is carried out at temperatures of 500-620 ^o C, a pressure of 1-2 ATM abs. and space velocity from 100 to 600 hour ^-1 ;
- the regeneration of the catalyst is carried out in the presence of air or other oxygen-containing gas at a temperature of 630-670 ^o C, atmospheric or slightly higher atmospheric pressure (1-2 atm abs.), the gas volumetric velocity from 100 to 500 hours ¹ and the residence time of the catalyst in the regeneration zone from 10 to 60 minutes.

The use of the inventive dehydrogenation of the proposed catalyst reduces coke formation, contributes to a more complete and faster occurrence of redox reactions on the catalyst. This increases the activity and selectivity of the process, resulting in an increase in the yield of olefinic hydrocarbons. The new catalyst contains a significantly smaller amount of hexavalent chromium compounds: respectively, in fresh about 0.5 wt. % and working in the dehydrogenation system of 0.12-0.2 wt. % The low content of hexavalent chromium compounds simplifies and makes the obligatory catalyst recovery process after the regenerator more complete. The application of the new method allows recovery at lower volumetric feed rates of methane: 40-60 hour ^-1 . This allows you to reduce energy consumption by approximately 2 times: natural gas and nitrogen. For a plant with a capacity of 80,000 t / year, the consumption of natural gas will decrease by approximately 500,000 nm ³ . In addition, the low content of hexavalent chromium compound reduces the toxicity of the catalyst and improves the environment.

 The process of obtaining the catalytic system used in the new method consists in dispersing chromium compounds on a carrier consisting of aluminum and zinc oxides.

 Example 1

Aluminum zinc spinel is obtained from zinc aluminate by calcination at 1000 ^° C. for 4 hours in a stream of air. A microspherical alumina-chromzinc catalyst having a particle diameter of 5 to 250 μm is obtained by spray-drying a suspension obtained from 1440 g of alumina-zinc spinel, 330 g of chromium trioxide and 3800 ml of water in a bead mill with stirring for 5 hours at a temperature of 20 ^o C. A sample of the catalyst is subjected to heat treatment, consisting of calcination at 680 ^o C for 4 hours in a stream of air. The resulting product has the following composition, wt. %:
Cr ₂ O ₃ - 14.9
ZnO - 37.7
Al ₂ O ₃ - 47.3
Dehydrogenation of propane to propylene is carried out in a unit with a fluidized bed of catalyst, consisting of a reactor and a regenerator with continuous circulation of the catalyst between them. The dehydrogenation process is carried out when 5500 g of catalyst is loaded into the reactor-regenerator system.

Dehydrogenation temperature - ~ 590 ^o C
Regeneration temperature - 650 ^o C
Volumetric speed - 200 hours ^-1
The pressure in the regenerator is 1.1 atm abs.

After regeneration, the catalyst, before being fed into the reactor, is restored at a temperature of 660 ^° C. for 2 minutes in order to remove hexavalent chromium compounds (0.12 wt%) formed in the regenerator. For recovery, natural gas is used, supplied to the reducing agent with a bulk velocity of 50 h ^-1 , the pressure in the reducing agent is 1.25 atm. After reduction of hexavalent chromium compounds in the catalyst are absent. The test results are shown in the table.

 Example 2

A microspherical alumochromzinc catalyst having a particle diameter of 5 to 250 μm is obtained by spray-drying a suspension obtained from 1440 g of alumina-zinc spinel synthesized as described in Example 1, 500 g of chromium trioxide and 4200 ml of water in a bead mill with stirring for 4 hour at a temperature of 30 ^o C. the Catalyst sample is subjected to heat treatment, consisting of calcination at 720 ^o C for 4 hours in a stream of air. The resulting product has the following composition, wt. %:
Cr ₂ O ₃ - 20.8
ZnO - 35.1
Al ₂ O ₃ - 44.1
The dehydrogenation of isobutane to isobutylene is carried out in a unit with a fluidized bed of catalyst, consisting of a reactor and a regenerator with continuous circulation of the catalyst between them. The dehydrogenation process is carried out when 5500 g of catalyst is loaded into the reactor-regenerator system.

Dehydrogenation temperature - ~ 590 ^o C
Regeneration temperature - 660 ^o C
Volumetric speed - 400 hour ^-1
The pressure in the regenerator is 0.9 atm abs.

After regeneration, the catalyst, before being fed into the reactor, is reduced at a temperature of 670 ^° C for 1 minute in order to remove hexavalent chromium compounds (0.15 wt%) formed in the regenerator. For recovery, natural gas is used, supplied to the reducing agent with a space velocity of 60 h ^-1 , the pressure in the reducing agent is 0.95 atm. After reduction of hexavalent chromium compounds in the catalyst are absent. The test results are shown in the table.

 Example 3

A microspherical alumochromzinc catalyst having a particle diameter of 5 to 250 μm is taught by spray-drying a suspension obtained from 1440 g of alumina-zinc spinel synthesized as described in Example 1, 820 g of chromium trioxide and 4600 ml of water in a bead mill with stirring for 2 hour at a temperature of 50 ^o C. the Sample of the catalyst is subjected to heat treatment, consisting of calcination at 780 ^o C for 3 hours in a stream of air. The resulting product has the following composition, wt. %:
Cr ₂ O ₃ - 30.1
ZnO - 31.0
Al ₂ O ₃ - 38.9
The resulting catalyst was tested in the process of dehydrogenation of propane.

 Dehydrogenation of propane to propylene is carried out in a unit with a fluidized bed of catalyst, consisting of a reactor and a regenerator with continuous circulation of the catalyst between them. The dehydrogenation process is carried out when 5500 g of catalyst is loaded into the reactor-regenerator system.

Dehydrogenation temperature - 620 ^o C
Regeneration temperature - 670 ^o C
Volumetric speed - 600 hour ^-1
The pressure in the regenerator is 1.4 atm abs.

After regeneration, the catalyst, before being fed into the reactor, is restored at a temperature of 680 ^° C. for 3 minutes in order to remove hexavalent chromium compounds (0.2 wt%) formed in the regenerator. For recovery, natural gas is used, supplied to the reducing agent with a space velocity of 60 h ^-1 , the pressure in the reducing agent is 1.5 atm. After reduction of hexavalent chromium compounds in the catalyst are absent.

 The results are shown in the table.

 Example 4

A microspherical alumochromzinc catalyst having a particle diameter of 5 to 250 μm is obtained by spray-drying a suspension obtained from 1440 g of alumina-zinc spinel synthesized as described in Example 1, 204 g of chromium trioxide and 3400 ml of water in a bead mill with stirring for 3 hour at a temperature of 50 ^o C. the Sample of the catalyst is subjected to heat treatment, consisting of calcination at 850 ^o C for 2 hours in a stream of air. The resulting product has the following composition, wt. %:
Cr ₂ O ₃ - 9.7
ZnO - 40.0
Al ₂ O ₃ - 50.3
The resulting catalyst was tested in the process of isobutane dehydrogenation.

 The dehydrogenation of isobutane to isobutylene is carried out in a unit with a fluidized bed of catalyst, consisting of a reactor and a regenerator with continuous circulation of the catalyst between them. The dehydrogenation process is carried out when 5500 g of catalyst is loaded into the reactor-regenerator system.

Dehydrogenation Temperature - 550 ^o C
Regeneration temperature - 640 ^o C
Volumetric speed - 120 hour ^-1
The pressure in the regenerator is 1.9 atm abs.

After regeneration, the catalyst, before being fed into the reactor, is reduced at a temperature of 650 ^° C. for 1 minute in order to remove hexavalent chromium compounds (0.15 wt%) formed in the regenerator. For recovery, natural gas is used, supplied to the reducing agent with a bulk velocity of 40 h ^-1 , the pressure in the reducing agent is 2.1 atm. After reduction of hexavalent chromium compounds in the catalyst are absent. The results are shown in the table.

Claims (4)

1. The method of producing olefin hydrocarbons by dehydrogenation of the corresponding paraffin hydrocarbons in the presence of an aluminum-chromium-containing catalyst, followed by its regeneration and recovery, characterized in that they use a composition catalyst, wt. %:
Cr ₂ O ₃ - 10.0 - 30.0
ZnO - 30.0 - 45.0
Al ₂ O ₃ - Else
and the recovery is carried out at a temperature of 640 - 700 ^o C, atmospheric, slightly less or slightly greater than atmospheric pressure, a gas volumetric velocity of 40-60 h ^-1 and the residence time of the catalyst in the recovery zone 1-3 minutes.  2. The method according to p. 1, characterized in that the dehydrogenation, regeneration and recovery is carried out in a fluidized bed of catalyst. 3. The method according to p. 1, characterized in that the dehydrogenation is carried out at a temperature of 500-620 ^o C, a pressure of 1-2 atmospheres of absolute and a volumetric gas velocity of 100 - 600 h ^-1 . 4. The method according to p. 1, characterized in that the regeneration of the catalyst is carried out in the presence of air or other oxygen-containing gas at a temperature of 630-670 ^o With, atmospheric or slightly higher atmospheric pressure, gas volumetric velocity of 100 to 500 h ^-1 and the residence time of the catalyst in the regeneration zone 10 - 60 min.

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