RU2555879C2 - Method of modifying crystalline zeolite zsm-5 and use of obtained zeolite with deactivated external surface - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of modifying crystalline zeolite ZSM-5 includes deactivating the external surface thereof by treating initial zeolite with an organosilicon compound and calcining the treated zeolite, wherein treatment is carried out by incipient wetness impregnation with a solution of tetraethyl orthosilicate or polymethylsiloxane in an organic solvent with the weight ratio of the organosilicon compound to the zeolite of (0.1-0.2):1, wherein impregnation is carried out in two steps with drying after each impregnation step at 100-110°C.

EFFECT: obtaining crystalline zeolite with high selectivity and high degree of conversion of olefin-containing material.

6 cl, 1 tbl, 13 ex

Description

The claimed group of inventions relates to methods for modifying zeolites and can be used to obtain zeolite with deactivated acid centers located on the outer surface of zeolite crystals, and their application.

The prior art methods for producing zeolites with a deactivated surface. Zeolites modified to deactivate the external surface are recommended for use in catalytic processes. Various modification methods lead to the production of zeolites with different properties, and therefore, the area of its use directly depends on the method of zeolite modification.

A known method of producing zeolite ZSM-5, including its modification with organosilicon compounds in the gas phase. The method includes treating the zeolite with vapors of an organosilicon compound containing at least two silicon atoms. The obtained modified zeolite is recommended for the conversion of aromatic hydrocarbons into products containing para-isomers of dialkylbenzenes (US 5516736, May 14, 1996).

A known method of obtaining a selective metallosilicate composition used for the conversion of alkylaromatic compounds. The method involves (1) contacting the mesoporous metallosilicate with an organosilicon compound in a solvent, (2) reacting a metallosilicate treated with an organosilicon compound with water, (3) repeating steps (1) and (2) and (4) calcining the catalyst in an oxygen-containing atmosphere (US 7094941, 08/22/2006).

A known method of treating molecular sieves such as SAPO or ZSM-34 with tetraethylorthosilicate or trimethylethyl silicate in the liquid or gas phase in a closed system for more than 20 days, followed by high-temperature calcination. The resulting product is proposed to be used to obtain olefins from oxygen-containing organic raw materials (US 2005/0003957, 01/06/2005).

A known method of modifying MFI zeolite, which is pre-calcined, then modified with a solution of an organosilicon compound in an organic solvent, is then mixed with a binding agent and subjected to granulation. Zeolite is recommended for use in hydrocarbon conversion processes in the production of para-xylene (US 6066770, 05.23.2000).

A known method for the conversion of light olefins on zeolites with a deactivated external crystal surface, which is deactivated by treating a zeolite from the group: ZSM-22, ZSM-23, ZSM-57 with rare earth or yttrium oxides. The oligomerization process is carried out at 200-300 ° C, 0.18-10 h ^-1 and a pressure of 5 MPa. The conversion of 2-butene under these conditions reaches 91% with a selectivity of C ₅₊ in liquid products up to 97%.

The disadvantages of the method are the high pressure during oligomerization, the presence of high-boiling C ₁₆₊ oligomers in the products, as well as the low degree of branching of oligomeric products, which negatively affects the octane number of the liquid fraction (US 7759533, 2010).

A known method of modifying a zeolite of type ZSM-5, including treating it with a reagent selected from tetraethylorthosilicate or ammonium heptamolybdate, or a phosphate compound in which the starting zeolite is not calcined before modification. The resulting modified product has blocked centers in the pores and surface acid sites with protected acid sites. The product is recommended for the conversion of oxygen-containing raw materials, including hydrocarbons, methanol and dimethyl ether, to high-octane gasoline (US 8450545, 05/28/2013).

The disadvantage of this method is that the resulting product does not have selectivity in the processes for the catalytic production of gasoline from the butane-butylene fraction (BBP).

The aim of the invention is to develop a method for producing crystalline zeolite with a deactivated external surface, which has increased selectivity and a high degree of conversion of olefin-containing raw materials upon receipt of the target fraction C ₅₊ .

The problem is solved by the described method of modifying a crystalline zeolite of the ZSM-5 type, which involves the decontamination of its external surface, carried out by treating the initial zeolite with an organosilicon compound and calcining the treated zeolite, while the treatment is carried out by the method of impregnation in water capacity with a solution of tetraethylorthosilicate (TEOS) or polymethylsiloxane (polymethylsiloxane) in an organic solvent with a mass ratio of organosilicon compound to zeolite (0.1-0.2): 1, while impregnating about uschestvlyayut in two steps with performing drying after each impregnation step at 100-110 ° C. The mass ratio of the organosilicon compound to the zeolite (0.1-0.2): 1 corresponds to the complete coating of the outer surface of the zeolite with a modifier. Reducing the mass ratio below 0.1: 1 does not allow to achieve complete coverage of the surface and, thereby, completely deactivate the outer surface. With an increase in the mass ratio above 0.2: 1, excessive coating of the zeolite surface with a modifier leads to blocking of the micropores of the zeolite and a decrease in the efficiency of the catalyst. Lowering the drying temperature below 100 ° C increases the drying time, which is technologically impractical; raising the temperature above 110 ° C does not affect the drying procedure, but leads to an increase in energy consumption at this technological stage.

Preferably, a solution of tetraethylorthosilicate in cyclohexane or polymethylsiloxane in octane is used for impregnation.

As the initial zeolite, a ZSM-5 type zeolite with a Si / Al molar ratio of 40, which contains γ-alumina in the amount of 30 wt.% As a binder, is used.

The method may include an additional step, in which the initial zeolite is impregnated with an organosilicon solution by impregnation with an aqueous solution of a metal salt selected from the series: Ga, Zn, La, followed by calcination.

Preferably, the zeolite impregnated with an organosilicon compound is calcined at 500 ° C.

When carrying out the method in the scope of the set of features mentioned above, a product was obtained that is a crystalline zeolite of the ZSM-5 type with a deactivated external surface, which we proposed for use in the oligomerization of a butane-butylene hydrocarbon fraction to obtain a gasoline hydrocarbon fraction. When implementing the method, poisoning of the strongest acid centers is achieved, which are located on the outer surface of ZSM-5 zeolite crystals and which are responsible for the side cracking process.

The proposed group of inventions provides the possibility of production of gasoline from BBF. In particular, raw materials were used that contain 77% butylenes and 20% butanes. The production process is reduced to the contact of BBP at a temperature of 300-450 ° C, a pressure of 1.5-2.3 MPa, a volumetric feed rate of liquid raw materials 1-4 h ^-1 on a stationary layer of solid catalyst particles, which is used as modified according to the proposed method zeolite with a deactivated outer surface. As confirmed by the examples presented below, the technical result is achieved: high selectivity for the formation of the target C ₅₊ fraction (up to 95%) with high stability of the catalyst over time.

The following are specific methods for implementing the claimed modification process and presents the results on the use of the obtained zeolite as an oligomerization catalyst.

BBP oligomerization in general is as follows. The preliminary preparation of the catalyst is carried out by heating it in a stream of inert gas (nitrogen, helium) to 300 ° C and calcining at this temperature for 30 minutes. BBF is fed to a flow-type reactor with a fixed catalyst bed. At the outlet of the reactor, the resulting products are separated into liquid and gaseous, the component composition is determined by chromatographic method.

Example 1

As the initial zeolite, the H-form of zeolite ZSM-5 (Si / Al = 40) is used, treated with TEOS by the method of impregnation by moisture capacity. To do this, the zeolite is impregnated with a solution of TEOS in cyclohexane from the calculation of TEOS: zeolite 0.2: 1 and dried at 110 ° C. Then the procedure of impregnation and drying is repeated. After that, the sample is calcined in a stream of dry air at 500 ° C.

The catalyst is placed in a flow reactor, purged with nitrogen at a temperature of 300 ° C and a pressure of 1.5 MPa for 1 h, then, at the same temperature and pressure, a feed is fed - BBP, containing 77% butylenes, 20% butanes and 3% pentanes, s mass speed 4 h ^-1 . The reaction is carried out for 6 hours

The butylene conversion is 94%, the selectivity of the C ₅₊ gasoline fraction for converted butylene is 95%. The results of the experiment are presented in table 1.

Example 2. (Comparative)

As the oligomerization catalyst, the H-form of zeolite ZSM-5 (Si / Al = 40) is used without additional treatments.

The oligomerization process is carried out as in example 1 with a butylene conversion of 98% and a selectivity of C ₅₊ 87%. Process indicators are presented in table 1.

A comparison of examples 1 and 2 illustrates the advantages of the proposed method for the modification of zeolite (increase selectivity of the catalyst).

Example 3

As the initial product, the H-form of zeolite ZSM-5 (Si / Al = 40) is used, which is treated with PMS by the method of impregnation by moisture capacity. To do this, the zeolite is impregnated with a solution of PMS in octane from the calculation of PMS: zeolite 0.1: 1 and then dried at 110 ° C. Treatment with a PMS solution and drying are repeated. After that, the sample is calcined in a stream of dry air at 500 ° C.

The oligomerization process is carried out as in example 1 with a butylene conversion of 96% and a selectivity of C _{5+ of} 93%. Process indicators are presented in table 1.

Example 4

The oligomerization process is carried out as in example 2, the difference is that the zeolite ZSM-5 is used as a catalyst, as in example 2, but with the addition of 1.0 wt.% Zn.

To do this, zeolite ZSM-5 (Si / Al = 40) is impregnated with an aqueous solution of zinc salt and dried at 110 ° C. After that, the sample is placed in a reactor and calcined in a stream of dry air at 500 ° C. Subsequent processing of TEOS is carried out as in example 1.

Process indicators are presented in table 1.

Example 5

The oligomerization process is carried out as in example 1, the difference is that zeolite ZSM-5 treated with TEOS is used as a catalyst, as in example 1, but with the addition of 1.0 wt.% Ga.

To do this, zeolite ZSM-5 (Si / Al = 40) is impregnated with an aqueous solution of gallium salt and dried at 110 ° C. After that, the sample is placed in a reactor and calcined in a stream of dry air at 500 ° C. Subsequent processing of TEOS is carried out as in example 1.

Process indicators are presented in table 1.

Example 6

The oligomerization process is carried out as in example 5, the difference is that when modifying the zeolite instead of the gallium salt, a zinc salt is used.

Process indicators are presented in table 1.

Example 7

The oligomerization process is carried out as in example 5, the difference is that instead of the gallium salt, the lanthanum salt is used to modify the zeolite.

Process indicators are presented in table 1.

Example 8

The oligomerization process is carried out as in Example 5, the difference is that for impregnation with a gallium salt followed by TEOS treatment, instead of pure ZSM-5 zeolite, the zeolite is modified with the addition of γ-alumina.

For this, a weighed portion of zeolite ZSM-5 (Si / Al = 40) is mixed with wet aluminum hydroxide at a ratio of 70:30 based on dry weight, extrudates are molded and dried at room temperature, then at 110 ° C, and then calcined at 500 ° C.

Process indicators are presented in table 1.

Example 9

The process is carried out as in example 8, the difference is that the oligomerization process is carried out at a mass feed rate of 1.5 h ^-1 instead of 2.7 h ^-1 .

Process indicators are presented in table 1.

Example 10

The process is conducted as in example 9, the difference is that the oligomerization process is carried out at 1.9 MPa instead of 1.5 MPa.

Process indicators are presented in table 1.

Example 11

The process is conducted as in example 9, the difference is that the oligomerization process is carried out at 2.3 MPa instead of 1.5 MPa.

Process indicators are presented in table 1.

Example 12

The process is conducted as in example 8, the difference is that the oligomerization process is carried out at a mass feed rate of 1.0 h ^-1 instead of 2.7 h ^-1 .

Process indicators are presented in table 1.

Example 13

The process is conducted as in example 8, the difference is that the process occurs on a deactivated catalyst.

The results are presented in table 1.

Claims (6)

1. A method of modifying a crystalline zeolite of type ZSM-5, including deactivating its outer surface by treating the initial zeolite with an organosilicon compound and calcining the treated zeolite, characterized in that the treatment is carried out by impregnation by the moisture capacity of a solution of tetraethylorthosilicate or polymethylsiloxane in an organic solvent with a mass ratio of organosilicon to zeolite (0.1-0.2): 1, while the impregnation is carried out in two stages with drying after each stage and impregnation at 100-110 ° C. 2. The method according to claim 1, characterized in that a solution of tetraethylorthosilicate in cyclohexane or polymethylsiloxane in octane is used for impregnation. 3. The method according to claim 1, characterized in that a zeolite of the ZSM-5 type with a Si / Al molar ratio of 40 containing γ-alumina in the amount of 30 wt.% As a binder is used as the initial zeolite. 4. The method according to claim 1, characterized in that the initial zeolite before impregnation with a solution of organosilicon compound is impregnated with an aqueous solution of a metal salt selected from the series: Ga, Zn, La, followed by calcination. 5. The method according to claim 1, characterized in that the calcination of the zeolite is carried out at 500 ° C. 6. The use of crystalline zeolite type ZSM-5 with a deactivated outer surface obtained by the method according to claims 1-5, for oligomerization of the butane-butylene fraction of hydrocarbons to obtain a gasoline fraction of hydrocarbons.