RU2568117C1 - Method of preparing catalyst for aromatising light paraffins - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of preparing a catalyst for aromatising light paraffins, based on mixing microporous material with a pentasil-type zeolite structure with pore size of not less than 5E and zinc-containing aluminium oxide. The zinc-containing aluminium oxide is obtained using aluminium hydroxide obtained by hydrolysis of aluminium isopropoxide with 0.5% aqueous isopropanol solution of methanoic acid with molar ratio aluminium isopropoxide:water:isopropanol of 1:(3-10):(10-20) and hydrolysis temperature of 30-40°C, characterised by average diameter of transport pores of 55-65 nm.

EFFECT: method enables to obtain catalysts, the use of which increases the output of aromatic compounds.

1 tbl, 9 ex

Description

 The invention relates to catalytic chemistry, in particular to methods for the preparation of catalysts for aromatization of light paraffins, and may find application in the chemical industry.

The process of producing aromatic hydrocarbons from light paraffins is carried out in the presence of catalytic systems based on finely porous materials - zeolites of the type ZSM-5, ZSM-11, CVN, CVM, BETA, etc., as well as element silicates with the structure ZSM-5, ZSM-11, BETA (for example, Advances in Chemistry. - 1990. - T. 52. - Issue 9. - P. 1552-1554; Izv. RAS, Ser. Chem. - 1993. - T. VII. - No. 4. - P. 15 -21).

To modify the catalytic properties of the above finely porous materials, metal additives or metal oxides such as zinc, gallium, rare earth, noble metals, etc. are used. (Pat. RF 2144845, publ. 01/27/2000, bull. No. 3; Pat. RF 2165293, publ. 04/20/2001, bull. No. 11; Pat. RF 2221643, publ. 20.01.2004, bull. No. 2; Pat RF 2148431, publ. 05/10/2000, bull. No. 13; Pat. RF 2372988, publ. 11/20/2009, bull. No. 32; Pat. RF 2367643, publ. 09/20/2009, bull. No. 26; Pat. RF 2307117 , publ. 07/10/2007, bull. No. 27; Pat. RF 2302291, publ. 10.07.2007, bull. No. 19).

The composition of aromatization catalysts, in addition to microporous material and modifiers, includes a binder or carrier, which, having a certain set of characteristics (specific surface area, pore structure, presence of acid-base centers, impurity composition), affect the activity, stability of work, strength characteristics of the catalyst (Dorogochinsky A.Z. et al. Aromatization of low molecular weight paraffin hydrocarbons on zeolite catalysts // TsNIITEneftekhim. - Petrochemistry and oil shale processing. - M .: - 1989. - 84 p.).

A known method of producing a catalyst for aromatization of light paraffin-containing hydrocarbon fractions (RF Patent 2172212, publ. 20.08.01).

In accordance with this method, a wet cake of aluminum hydroxide or another binder is mixed with a zeolite of the pentasil group in ammonium form (Na ₂ O content not more than 0.4 wt%). The mass is thoroughly mixed, and then evaporated to a plastic state and granulated by extrusion. The obtained granules are dried at a temperature of 110 ° C for 8-10 hours and calcined at a temperature of 550 ° C for 6 hours. Zinc, gallium, rare earth, magnesium and iron (III) nitrates are applied to the calcined catalyst precursor by impregnation from an aqueous solution. The catalyst granules are dried at 110 ° C and calcined at 550 ° C.

By this method, a catalyst is obtained with the following ratio of components,% mass .: zeolite - 40-80; ZnO - 0.4-4.0; Σ (REE) ₂ O ₃ - 0.3-3.0; Fe ₂ O ₃ - 0.01-1.0; MgO - 0.01-1.0, binding compounds - the rest.

The disadvantage of this method is to obtain a catalyst of complex chemical composition and low activity. So, in the process of converting propane to aromatic hydrocarbons in the presence of this catalyst in the following process conditions: temperature - 540 ° C; pressure - 4 atm; the volumetric feed rate is 500 h ^-1 , the yield of aromatic hydrocarbons was 31.5% of the mass.

Closest to the proposed invention in its technical essence and the achieved effect is a method of producing a catalyst described in patent 2302291 (publ. 10.07.2007, bull. No. 19).

According to this method, the catalyst is prepared by mixing a microporous material — zeolite type ZSM-5, ZSM-11, BETA, or an aluminum silicate element with a structure like ZSM-5, ZSM-11, BETA and zinc or / and gallium-containing alumina; moreover, for the preparation of zinc - and / or gallium-containing alumina using biporous aluminum hydroxide with a transport pore size of 40-50 nm.

The use of such biporous aluminum hydroxide allows evenly applying a modifying metal in the required concentration; to freely carry out mass transfer of the molecules of the starting hydrocarbons and reaction products between the microporous material and the modifying metal.

In this method, the catalyst is prepared as follows.

Zinc or / and gallium-containing alumina is pre-synthesized by applying zinc acetate or / and gallium nitrate to biporous aluminum hydroxide, followed by drying and calcination of the composition at 500 ° C.

To obtain the actual catalyst, a microporous material is mixed — a zeolite of the type ZSM-5, ZSM-11, BETA, or an aluminum silicate element with a structure of ZSM-5, ZSM-11, BETA and zinc or / and gallium-containing alumina; the resulting catalyst is calcined at 500 ° C.

The disadvantage of this method is to obtain a catalyst characterized by low activity.

So, when carrying out the process of aromatization of n-butane in the presence of a catalyst sample obtained by the described composition method:% mass. - ZSM-5 - 71.5; Zn - 3.5; Al ₂ O ₃ - 25 at the technological mode: temperature - 550 ° C, butane space velocity - 700 h ^-1 , pressure - 0.4 MPa, aromatic hydrocarbon yield was 39.7%.

The objective of the present invention is to provide a method for the preparation of a catalyst for aromatization of light paraffins, characterized by higher activity than in the known method.

The technological result of the claimed method of preparing a catalyst for aromatization of light paraffins is to increase the yield of aromatic carbohydrates.

This is achieved by replacing biporous aluminum hydroxide with an average transport pore size of 40-50 nm with aluminum hydroxide obtained by hydrolysis of aluminum isopropoxide with a 0.5% aqueous isopropanol solution of formic acid at a molar ratio of aluminum isopropoxide: water: isopropanol as 1: (3- 10) :( 10-20) and a hydrolysis temperature of 30-40 ° C, characterized by an average transport pore diameter of 55-65 nm.

и цинксодержащего оксида алюминия, отличающегося тем, что для приготовления цинксодержащего оксида алюминия используют гидроксид, полученный гидролизом изопропоксида алюминия 0,5%-ным водно-изопронольным раствором муравьиной кислоты при мольном соотношении изопропоксид алюминия:вода:изопропанол как 1:(3-10):(10-20) и температуре гидролиза 30-40°C, характеризующийся средним диаметром транспортных пор 55-65 нм.The essence of the invention is expressed in the fact that the catalyst for aromatization of light paraffins is obtained by a method comprising mixing microporous material with the structure of zeolites such as pentasils with a pore size of at least

and zinc-containing aluminum oxide, characterized in that for the preparation of zinc-containing aluminum oxide using hydroxide obtained by hydrolysis of aluminum isopropoxide with 0.5% aqueous isopronol solution of formic acid with a molar ratio of aluminum isopropoxide: water: isopropanol as 1: (3-10) : (10-20) and a hydrolysis temperature of 30-40 ° C, characterized by an average transport pore diameter of 55-65 nm.

, отношением SiO₂/Al₂O₃=30-50 моль/моль, остаточным содержанием Na₂O - не более 0,07 масс.; изопропоксид алюминия плотностью 0,936-0,938 г/см³ (при 70°C); кинематической вязкостью - 51-51,3 (70°C); температурой кипения при 5 мм рт.ст. - 132-136°C.To obtain the aromatization catalyst by the indicated method, a microporous material with a structure of pentasil type zeolites with a pore size of at least

, the ratio of SiO ₂ / Al ₂ O ₃ = 30-50 mol / mol, the residual content of Na ₂ O is not more than 0.07 mass .; aluminum isopropoxide with a density of 0.936-0.938 g / cm ³ (at 70 ° C); kinematic viscosity - 51-51.3 (70 ° C); boiling point at 5 mm Hg - 132-136 ° C.

Example 1

51 g of molten aluminum isopropoxide are introduced into a glass reactor equipped with a stirrer, thermometer, reflux condenser, and dropping funnel and 209 ml of a 0.5% aqueous solution of formic acid are added dropwise with vigorous stirring, while the molar ratio of aluminum isopropoxide to water and isopropanol is like 1: 3: 10, respectively. The hydrolysis temperature is maintained at 30 ° C.

After the completion of the hydrolysis step, the resulting suspension of aluminum hydroxide is settled; the precipitate is filtered on a Buchner funnel with a filter of needle-punched fabric. Wet aluminum hydroxide is dried at a temperature of 105 ° C for 8-10 hours.

By impregnation, a sample of the zinc-containing oxide component of the catalyst is prepared.

For this, 40 g of aluminum hydroxide is impregnated with an aqueous solution of zinc acetate containing 7.19 g of salt. The amount of water required to prepare a solution of zinc acetate is determined taking into account the moisture absorption of aluminum hydroxide.

The resulting alumina-zinc mass is dried for 10 hours and calcined at 500 ° C.

50 g of powdered zeolite ZSM-5 with a ratio of SiO ₂ / Al ₂ O ₃ = 40 mol / mol are mixed with zinc-containing alumina. The resulting catalyst was calcined at 500 ° C. Prepared according to the described method, the catalyst has a composition,% mass .: zeolite - 70.0; Al ₂ O ₃ - 27, zinc - 3.0.

Obtained by the proposed method, the catalyst was tested in the process of aromatization of n-butane.

Aromatization of n-butane was carried out at a temperature of 550 ° C, a space velocity of 750 h ^-1 , a pressure of 0.4 MPa.

Under these conditions, the yield of aromatic hydrocarbons, in terms of the feed, was 44.6% (see table).

In examples 2-8, the catalysts were prepared according to the method described in example 1, with varying conditions for the production of aluminum hydroxide.

In example 2, the molar ratio of aluminum isopropoxide, water and isopropanol was maintained at 1:10:10, respectively, and the hydrolysis temperature was 30 ° C.

After carrying out, according to Example 1, tests of the catalyst during aromatization, the yield of aromatic hydrocarbons (C ₆ -C ₉ ), in terms of the feed, was 44.5% (see table).

In Example 3, the molar ratio of aluminum isopropoxide to water and isopropanol was maintained as 1: 3: 20, respectively; and the hydrolysis temperature is 30 ° C.

After carrying out, according to Example 1, tests of the catalyst during aromatization of n-butane, the yield of aromatic hydrocarbons (C ₆ -C ₉ ), calculated on the basis of the feed, was 44.6% (see table).

In Example 4, the molar ratio of aluminum isopropoxide to water and isopropanol was maintained at 1: 3: 10, respectively, and the hydrolysis temperature was 40 ° C.

After the tests of the catalyst carried out in Example 1 during the aromatization process, the yield of aromatic hydrocarbons (C ₆ -C ₉ ), in terms of the feed, was 44.6% (see table).

In Example 5, the molar ratio of aluminum isopropoxide to water and isopropanol was maintained as 1:12:10, respectively; and the hydrolysis temperature is 30 ° C.

After carrying out, according to Example 1, tests of the catalyst during aromatization, the yield of aromatic hydrocarbons (C ₆ -C ₉ ), in terms of the feed, was 42.2% (see table).

In example 6, the molar ratio of aluminum isopropoxide to water and isopropanol was maintained as 1: 3: 8, respectively, and the hydrolysis temperature was 40 ° C.

After carrying out, according to Example 1, tests of the catalyst during the aromatization process, the yield of aromatic hydrocarbons (C ₆ -C ₉ ), in terms of the feed, was 42.3% (see table).

In example 7, the molar ratio of aluminum isopropoxide to water and isopropanol was maintained as 1: 3: 22, respectively, and the hydrolysis temperature was 30 ° C.

After tests of the catalyst carried out in Example 1 during aromatization, the yield of aromatic hydrocarbons (C ₆ -C ₉ ), calculated on the basis of the feed, was 44.5% (see table).

In Example 8, the molar ratio of aluminum isopropoxide to water and isopropanol was maintained at 1: 3: 10, respectively, and the hydrolysis temperature was 45 ° C.

After carrying out, according to Example 1, tests of the catalyst during the aromatization process, the yield of aromatic hydrocarbons (C ₆ -C ₉ ), in terms of the feed, was 40.3% (see table).

When the molar ratio of water to isopropoxide is less than “three”, the hydrolysis of aluminum isopropoxide occurs partially; at a hydrolysis temperature below 30 ° C, a clumping process of the resulting aluminum hydroxide is observed.

Example 9 (prototype).

The catalyst is prepared according to the method described in the prototype.

30 g of aluminum hydroxide with an average transport pore size of at least 20 nm was impregnated with an aqueous solution of zinc acetate based on 14% mass, zinc, after which the sample was dried and calcined at 500 ° C to obtain the ΖnΟ / γ-Al ₂ O ₃ composition.

25 g of zeolite powder ZSM-5 was mixed with a sample of ΖnΟ / γ-Al ₂ O ₃ from the calculation to obtain 25% of the mass. Αl ₂ Ο ₃ in the final catalyst, which corresponded to 3.5% of the mass. zinc in the final sample of the catalyst. The resulting catalyst was calcined at 500 ° C and tested in the process of aromatization of n-butane.

Aromatization of butane was carried out at a temperature of 550 ° C, the volumetric feed rate of n-butane was 750 h ^-1 , and the pressure was 0.4 MPa.

Under these conditions, the yield of aromatic hydrocarbons (C ₆ -C ₉ ), in terms of the feed, was 39.7% (see table).

Claims (1)

A method of preparing a catalyst for aromatization of light paraffins based on a mixture of microporous material with a structure of zeolites such as pentasils with a pore size of at least

and zinc-containing alumina, characterized in that to obtain zinc-containing alumina, aluminum hydroxide is used, obtained by hydrolysis of aluminum isopropoxide with a 0.5% aqueous isopropanol solution of formic acid at a molar ratio of aluminum isopropoxide: water: isopropanol as 1: (3-10 ) :( 10-20) and a hydrolysis temperature of 30-40 ° C, characterized by an average transport pore diameter of 55-65 nm.