RU2351580C1 - Method of isobutylene production - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention refers to method of isobutylene production by decomposition methyl-tertiary-butyl ether with heterogeneous catalyst at raised temperature and pressure, characterised that catalyst is multi-purpose synthetic zeolite NaX, while process is enables at atmospheric pressure with water vapour with observing the conditions as follows: temperature 200-250°C, volumetric MTBE feed rate 1.0-2.0 h^-1. These conditions ensure minimal generation of MTBE decomposition by-products.

EFFECT: MTBE conversion per run is 96-99% with isobutylene selectivity at least 99%.

1 cl, 3 tbl, 9 ex

Description

The invention relates to a method for producing olefins, in particular to a method for producing pure isobutylene by decomposition of methyl tertiary butyl ether (MTBE).

A known method of producing isobutylene by decomposition of MTBE in the presence of acidic cation exchanger KU-2FPP [PATENT of the Russian Federation No. 2083541, class. C07C 1/213, 1997] (Analog).

The disadvantages of this method is the low productivity and low selectivity of the process.

A known method of producing tertiary olefins by decomposition of tertiary alkyl esters at elevated temperatures (160-230 ° C) and a pressure of 0.6 MPa in the presence of a catalyst - alumina modified with silicon-organic compounds selected from the series: Si (OC ₂ H ₅ ) ₄ , SiCl ₄ , Cl ₂ Si (CH ₃ O) ₂ , Cl ₂ Si (C ₂ H ₅ O) ₄ [USSR PATENT No. 799641, bull. No. 3, 1981] (Analog).

The disadvantages of this method: - the use of scarce and expensive organosilicon compounds, and also - low productivity (volumetric feed rate of not more than 1 h ^-1 ) and low selectivity - a large number of by-products (DME, cis-butene-2, etc. )

Closest to the claimed method according to the technical essence is a method for producing C4-C5 tert-olefins by splitting the corresponding methyl tert-alkyl esters in the presence, as a catalyst, of H ⁺ - mordenite [USSR PATENT No. 1176825, bull. No. 32, 1985] (Prototype). According to this method, a zeolite with a mordenite structure in H ⁺ form, which is preactivated with hydrogen at 100-450 ° C and a pressure of 1 to 50 bar for 1-60 hours, is used as a decomposition catalyst for MTBE.

The disadvantages of this method are: low productivity (volumetric feed rate not more than 1 h ^-1 ) and insufficient selectivity inherent in all acidic catalysts, as well as rapid coking of the catalyst due to the formation of by-products and resins and its frequent regeneration.

The aim of the invention is to simplify the process technology, increase productivity and increase selectivity by reducing the formation of by-products and resins.

This goal is achieved by the process of decomposition of MTBE at 200-250 ° C and atmospheric pressure in the presence of water vapor over a zeolite catalyst, which is used as a synthetic general purpose NaX zeolite with a binder.

Synthetic zeolite NaX is used in the processes of adsorption drying and gas purification [N. V. Keltsev, “Fundamentals of adsorption technology”, M., Chemistry, 1984] and is not deficient. No further processing of zeolite is required.

Table 1 Physico-chemical properties of synthetic general purpose NaX zeolite with a binder. The name of indicators NaX according to TU 2163-077-05766575-99 Top grade First grade 1. Bulk density, g / cm ³ , not less 0.60 0.60 2. The size of the granules by the average diameter, mm 2.9 ± 0.3 2.9 ± 0.3 3. Mechanical crushing strength, kg / mm ² , not less 1,0 0.8 4. Mass fraction of water resistance,%, not less than 98 97 5. Dynamic capacity for water vapor for the size of the granules in the average diameter of 3.6 ± 0.4 mm, mg / cm ³ , not less 108 106

This method is illustrated by the following examples.

. На выходе из реактора получают газ и водный слой, содержащий метанол.Example 1. In a flowing metal cylindrical reactor with a diameter of 2.5 cm and a height of 21 cm load 100 cm ³ synthetic zeolite NaX. The reactor is equipped with electric heating. MTBE is passed through the reactor at a temperature of 250 ° C with a space velocity V _MTBE = 2.0 h ^-1 and water with a space velocity

. At the outlet of the reactor, gas and an aqueous layer containing methanol are obtained.

Gas composition: isobutylene - 97.36%, MTBE - 0.55%, methanol - 1.02%, DME - 0.12%, water - 0.24%, isobutylene dimers - 0.22%, cis-butene - 2 - 0.40%, trimers of isobutylene - 0.01%.

At the same time, MTBE conversion is achieved - 99.4%, and selectivity for isobutylene - 99.5%.

The MTBE conversion is calculated as the ratio of the converted MTBE to that fed to the reaction in wt%.

Isobutylene selectivity is calculated as the difference: 100% - impurities (DME, TMK, isobutylene dimers, cis-butene-2, isobutylene trimers)%.

The compositions of the products and the results of the experiments are summarized in tables 2 and 3.

.Example 2. The decomposition of MTBE is carried out under the conditions of example 1 at a temperature of 230 ° C, V _MTBE = 1.7 h ^-1 ,

.

Gas composition: isobutylene - 95.86%, MTBE - 0.86%, methanol - 2.32%, DME - 0.06%, water - 0.28%, TMK - 0.01%, isobutylene dimers - 0, 39%, cis-butene-2 0.22%.

At the same time, MTBE conversion is achieved - 99.3%, selectivity for isobutylene -99.50%.

.Example 3. The decomposition of MTBE is carried out under the conditions of example 1 at a temperature of 990 ° C. V _MTBE = 2.2 h ^-1 ,

.

Gas composition: isobutylene - 89.34%, MTBE - 7.86%, methanol - 2.13%, DME - 0.01%, water - 0.29%, TMK - 0.06%, isobutylene-0 dimers, 31%

At the same time, MTBE conversion is achieved - 90.7%, selectivity for isobutylene -99.61%.

.Example 4. The decomposition of MTBE is carried out under the conditions of example 1 at a temperature of 200 ° C, V _MTBE = 1.5 h ^-1 ,

.

Gas composition: isobutylene - 91.52%, MTBE - 4.18%, methanol - 3.44%, DME - 0.01%, water - 0.26%, TMK - 0.01%, isobutylene dimers - 0, 58%

At the same time, MTBE conversion is achieved - 96.0%, selectivity for isobutylene - 99.63%.

.Example 5. The decomposition of MTBE is carried out under the conditions of example 1 at a temperature of 200 ° C, V _MTBE = 1.2 h ^-1 ,

.

Gas composition: isobutylene - 93.90%, MTBE - 3.35%, methanol - 1.72%, DME - 0.01%, water - 0.21%, isobutylene trimers - 0.02%, isobutylene dimers - 0 , 78%.

At the same time, MTBE conversion is achieved - 96.0%, selectivity for isobutylene - 99.63%.

.Example 6. The decomposition of MTBE is carried out under the conditions of example 1 at a temperature of 180 ° C, V _MTBE = 0.5 h ^-1 ,

.

Gas composition: isobutylene - 89.92%, MTBE - 7.88%, methanol - 1.60%, DME - 0.001%, water - 0.24%, TMK - 0.02%, isobutylene dimers - 0.33% , trimers of isobutylene - 0.01%.

At the same time, MTBE conversion is achieved - 81.4%, selectivity for isobutylene - 99.7%.

Example 7. In a flowing metal cylindrical reactor with a diameter of 2.5 cm and a height of 21 cm load 100 cm ³ synthetic zeolite NaX. The reactor is equipped with electric heating. MTBE is passed through the reactor at a temperature of 230 ° C with a space velocity V _MTBE = 1.4 h ^-1 . At the outlet of the reactor receive gas.

Gas composition: isobutylene - 96.29%, MTBE - 0.47%, methanol - 1.46%, DME - 0.66%, water - 0.25%, isobutylene dimers - 0.16%, cis-butene - 2 - 0.91%. Trimers of isobutylene - 0.01%.

At the same time, MTBE conversion is achieved - 99.5%, selectivity for isobutylene - 98.7%.

Example 8. The decomposition of MTBE is carried out under the conditions of example 7 at a temperature of 200 ° C, V _MTBE = 1.4 h ^-1 .

Gas composition: isobutylene - 90.08%, MTBE - 0.69%, methanol - 7.73%, DME - 0.11%, water - 0.19%, isobutylene dimers - 0.21%, cis-butene - 2 - 0.96%. Trimers of isobutylene - 0.02%.

At the same time, MTBE conversion is achieved - 97.46%, selectivity for isobutylene - 99.10%.

Example 9 (prototype). The decomposition of MTBE is carried out on H ⁺ - mordenite treated with hydrogen at 450 ° C for 60 hours. The decomposition of MTBE is carried out at a temperature of 160 ° C, a pressure of 10 bar, the consumption of 1 g of raw material per 1 g of catalyst per hour, V _MTBE = 1.3 h ^-1 . The decomposition product has the composition: MTBE - 9.2%, isobutylene - 57.8%, methanol - 30.5%, DME - 1.8%, water - 0.7%.

After distillation, the target product has the composition: isobutylene - 97.5%, methanol - 2.5%. Moreover, the MTBE conversion per passage is 90.8%, and the selectivity for isobutylene is 96.8%.

table 2 The composition of the gas. Composition, wt.% 1 experience 2 experience 3 experience 4 experience 5 experience 6 experience 7 experience 8 experience 9 experience (prototype) iC ₄ H ₈ 97.36 95.86 89.34 91.52 93.90 89.92 96.29 90.08 57.8 MTBE 0.55 0.86 7.86 4.18 3.35 7.88 0.47 0.69 9.2 CH ₃ OH 1,02 2,32 2.13 3.44 1.72 1,60 1.46 7.73 30.5 DME 0.12 0.06 0.01 0.01 0.01 0.001 0.66 0.11 1.8 H ₂ O 0.24 0.28 0.29 0.26 0.21 0.24 0.25 0.19 0.7 TMK - 0.1 0.06 0.01 - 0.02 - - - Dimers iC ₄ H ₈ 0.22 0.39 0.31 0.58 0.78 0.33 0.16 0.21 - Cis-butene-2 0.40 0.22 - - - - 0.91 0.96 - IC ₄ H ₈ Trimers 0.01 - - - 0.02 0.01 0.01 0.02 -

Table 3 The results of experiments on the decomposition of MTBE on a NaX catalyst. No. Catalyst T, ° С Volumetric speed of raw materials, h ^-1 Volumetric velocity in water, h ^-1 The conversion of MTBE, wt.% Selectivity, wt.% one Nax 250 2.0 1,1 99,4 99.5 2 Nax 230 1.7 0.9 99.9 99.5 3 Nax 220 2.2 1,0 90.7 99.6 four Nax 200 1,5 1,0 96.0 99.6 5 Nax 200 1,2 0.5 95.9 99.3 6 Nax 180 0.56 0.25 81.0 99.7 7 Nax 230 1.4 - 99.5 98.7 8 Nax 200 1.4 - 97.5 99.1 H ⁺
mordenitis 160 1,0 - 90.8 96.8 9

As can be seen from the above examples, the claimed method achieves almost 100% conversion of MTBE per pass, with a selectivity of isobutylene formation of at least 99%. The formation of such an “harmful” impurity for isobutylene as DME is reduced 180–1800 times.

When the volumetric feed rate of more than 2.0 h ^-1 (example 3, table 3) there is a decrease in the conversion of MTBE to 90.7%. Raise the temperature in the reactor over 250 ° C, i.e. increase energy consumption and reduce the volumetric feed rate of less than 1.0 h ^-1 , i.e. to reduce productivity is not economically feasible. An increase in temperature also leads to the appearance of a “harmful” impurity — DME and cis-butene-2 — the product of isobutylene isomerization (examples 1, 2 of Table 2).

Optimum process parameters: temperature 200-250 ° C, V _MTBE = (1.0-2.0) h ^-1 . Mass ratio of H ₂ O: MTBE = (0.25-0.5): 1.

Carrying out the process in the presence of water vapor reduces the formation of by-products: DME, isobutylene dimers, cis-butene-2, thereby increasing the selectivity of the process. In addition, water vapor removes the resulting resins from the surface of the catalyst, thereby increasing the inter-regeneration range. The resulting water-soluble reaction products — methanol and DME impurities — pass into the water layer upon cooling and condensation, and isobutylene passes into the organic layer, which simplifies the technological scheme for the separation of reaction products and the isolation of pure isobutylene.

Claims (1)

A method of producing isobutylene by decomposition of methyl tertiary butyl ether on a heterogeneous catalyst at elevated temperature and pressure, characterized in that the catalyst is a synthetic general purpose zeolite NaX and the process is carried out at atmospheric pressure in the presence of water vapor under the following conditions: temperature 200- 250 ° C, the volumetric feed rate of MTBE is 1.0-2.0 h ^-1 .