RU2035444C1 - Method of conversion of isobutane to isobutylene - Google Patents

Abstract

FIELD: chemical technology. SUBSTANCE: isobutane is converted to isobutylene at 610-680 C on the catalyst containing 2-6 wt.-% chrome and 2-6 wt. -% manganese on aluminium oxide in the presence of carbon dioxide at molar ratio of isobutane and carbon dioxide 0.8-1.4:1. EFFECT: improved method of conversion. 1 tbl

Description

 The invention relates to a method for processing paraffin hydrocarbons, specifically to carbon dioxide conversion (dehydrogenation) of isobutane to isobutylene and carbon monoxide, and can be used in the chemical and oil and gas industry.

A known method of dehydrogenation of paraffin hydrocarbons With ₄ -C ₅ , in particular isobutane, on a Pt-Al ₂ O ₃ catalyst at a temperature of 540-570 ^about [1] The yield of isobutylene is 36.4% with a selectivity of 91.1 wt.

 The disadvantages of the method are the use of precious platinum metal, insufficiently high yield of isobutylene, coke formation on the catalyst.

Also known is a method of dehydrogenation of isobutane using catalyst Al ₂ O ₃ -Cr ₂ O ₃ at 580-620 ^{° C} [2] The yield is 30-33% of isobutylene selectivity to olefins 72-76%
The disadvantages of the method are the insufficiently high yield of isobutylene, coke formation, wear of the catalyst when it is circulated in a reactor with a moving stream.

The closest to the proposed method for the conversion of isobutane to isobutylene is a method for the conversion of isobutane with carbon dioxide, which carries at 750 ^{° C} on the catalyst, which is a system consisting of Mn and Fe oxides (17 and 4% respectively), [3] The yield of isobutylene is equal to 28 wt. selectivity of 53 wt. The ratio of isobutane and carbon dioxide is 1: 1.

 The disadvantages of the prototype are the low yield of isobutylene and selectivity.

 The aim of the invention is to increase the yield of isobutylene and increase selectivity.

This goal is achieved in that the conversion process of isobutane with carbon dioxide is carried out in the presence of a catalyst containing 2-6 wt. Cr and 2-6 wt. Mn on γ-Al ₂ O ₃ at a temperature of 610-680 ^C and a ratio of isobutane, carbon dioxide, equal to 0.8-1.4: 1.

The essence of the method is as follows: the process of carbon dioxide conversion of isobutane to isobutylene and CO is carried out in a flow system with a quartz reactor with a diameter of 7 mm 4 cm ^{3 of} catalyst are loaded into the reactor; the particle diameter of the catalyst is 2-4 mm.

The catalyst is prepared by impregnation of γ-Al ₂ O ₃ with a solution of carbon dioxide Cr (CH ₃ COO) ₃ based on the content of 2-6% C in the catalyst. The impregnated γ-alumina is dried at ¹⁰⁰ ° C for 3 hours. After drying, the catalyst was calcined in a muffle furnace at 850 ^{° C} for 3 hours. Then, the impregnation of the catalyst obtained sodium acetate manganese Mn (CH ₃ COO) ₂ .4H ₂ O calculated on the content of 2-6% Mn in the catalyst, followed by drying and calcination under the indicated conditions.

In the resulting catalyst lead conversion of isobutane in the presence of carbon dioxide at a temperature of 610-680 ^{° C,} ratio of carbon-dioxide isobutane of 0.8-1.2: 1, the feed space velocity 720 h ^-1.

PRI me R 1. The process of conversion of isobutane to carbon dioxide is carried out at a temperature of 660 ^about With the ratio of isobutane-carbon dioxide of 0.8: 1, the volumetric feed rate of 720 h ^-1 on the catalyst Cr-Mn-O / Al ₂ O ₃ with a content of 4% Cr and 4% Mn.

The catalyst is prepared as follows: 4.1 g of γ-Al ₂ O _{3 are} mixed with a solution of Cr (CH ₃ COO) ₃ (0.74 g in 50 ml of water). The suspension was stirred for 2 hours, then dried at ¹⁰⁰ ° C for 3 hours. After drying, the catalyst was calcined at ⁸⁵⁰ ° C (3 h). Then, the resulting catalyst is impregnated with a solution of manganese acetate Mn (CH ₃ COO) ₂ (0.75 g in 50 ml of water), followed by stirring, drying, and calcination under the indicated conditions.

Missed feed gas, l / h: iC ₄ H ₁₀ 1.65
СО ₂ 1.35 Thus obtained: iC ₄ H ₈ 0.84
CH ₄ 0.26
C ₃ H ₆ 0.22
СО 0.24
H ₂ 0.20 iC ₄ H ₁₀ 0.63
СО ₂ 1.19 Conversion iC ₄ H ₁₀ , 62.5 Selectivity, 80.0 Output i-С ₄ Н ₈ , 50.0
PRI me R 2. The process is carried out according to the method described in example 1, at a temperature of 630 ^about C and the correspondence of isobutane-carbon dioxide 1: 1 on a catalyst containing 2% Cr and 5% Mn. Missed feed gas, l / h: iC ₄ H ₁₀ 1.5
CO ₂ 1,5
In this case, obtained: i-C ₄ H ₈ 0.72
CH ₄ 0.24
C ₃ H ₆ 0.21
SD 0.18
H ₂ 0.15 iC ₄ H ₁₀ 0.75
СО ₂ 1.34 Conversion iC ₄ H ₁₀ , 53.2 Selectivity, 78.4 Output i-С ₄ Н ₈ , 53.2
PRI me R 3. The process is carried out according to the method described in example 1, at a temperature of 670 ^about C and the ratio of isobutane-carbon dioxide 1: 1 on a catalyst containing 6% Cr and 2% Mn.

Missed feed gas, l / h: iC ₄ H ₁₀ 1.5
СО ₂ 1,5
Thus obtained: iC ₄ H ₈ 0.90
CH ₄ 0.28
C ₃ H ₆ 0.23
СО 0.26
H ₂ 0.23 iC ₄ H ₁₀ 0.58
CO ₂ 1.12 Conversion iC ₄ H ₁₀ 68.7 Selectivity 81.3 Output iC ₄ H ₈ 55.8
PRI me R 4. The process is carried out according to the method described in example 1, at a temperature of 660 ^about C and the ratio of isobutane-carbon dioxide of 1.4: 1 on a catalyst containing 2% Cr and 6% Mn.

Missed feedstock, l / h: iC ₄ H ₁₀ 1.75
СО ₂ 1.25 Thus obtained: iC ₄ H ₈ 0.82
CH ₄ 0.25
C ₃ H ₆ 0.25
СО 0.23
H ₂ 0.20 i-C ₄ H ₁₀ 0.65
СО ₂ 1.20 i-С ₄ Н ₁₀ conversion, 60.4 Selectivity, 78.8 i-С ₄ Н ₈ output, 47.6
The remaining examples are carried out similarly. The data on examples are given in the table. Examples 1-4 are basic.

As can be seen from examples 1-4, when carrying out the process in the stated conditions, there is an increase in the selectivity of the process for isobutylene to 78.4-81.3%, i.e., 25.2-28.1 points higher, compared with the prototype. The yield of isobutylene reaches 55.8% i.e. 28.1% higher than in the prototype. The table also shows examples for comparison: examples 5-6 on the transcendental ratio of iC ₄ H ₁₀ / CO ₂ , examples 7, 8 on the transcendental content of chromium and manganese in the catalyst, examples 9, 10 on transcendental temperature values.

 As can be seen from the table, the implementation of the process at a ratio below and above the claimed limit does not lead to the achievement of the goal. In this case, the yield of isobutylene remains at the prototype level or lower. The exception is example 10, where the yield of isobutylene is higher than in the prototype, however, the selectivity is 5.1% lower than in the prototype. When carrying out the process at a concentration of chromium and manganese below and above 2-6%, a decrease in selectivity for isobutylene from 78.4-81.3% to 48.9-49.1% is also observed. The same changes occur when the temperature changes below and above the claimed the limit.

 The results obtained indicate the effective acceptance of Cr-Mn by the carbon dioxide system and the creation of a more oxidized surface on which coke formation does not occur and the yield of isobutylene decreases.

Claims (1)

METHOD FOR CONVERSION OF ISOBUTANE TO IZOBUTYLENE in the presence of carbon dioxide at elevated temperature on a manganese-containing catalyst on an alumina support, characterized in that the process is carried out on a catalyst containing 2 to 6 wt. chromium and 2 to 6 wt. manganese on alumina at 610 680 ^o With a molar ratio of isobutane and carbon dioxide of 0.8 1.4 1, respectively.

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