RU2466789C1 - Method of preparing catalyst for isomerisation of c4-c6 hydrocarbons - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of preparing catalyst for isomerisation of C₄-C₆ hydrocarbons includes mixing sulfonated zirconium hydroxide powder with powder of binding agent - aluminium hydroxide, plasticisation of mixture of powders by peptisation with mixture of mineral acids, granulation by extrusion, thermal processing of carrier, application of platinum, and thermal processing of catalyst, contact of powders with mixture of acids-peptisers being performed in two stages: first, entire amount of sulfonated zirconium hydroxide and part of aluminium hydroxide are peptised with application of calculated amount of sulfuric acid and up to 3/4 of amount of nitric acid, after that, the remaining amount of aluminium hydroxide and the remaining amount of nitric acid are added to obtained peptised products, ratio of zirconium and aluminium hydroxides in finished catalyst constitutes from 85:15 to 70:30 respectively.

EFFECT: increase of catalyst activity, increase of its mechanical strength and simplification of technology of its obtaining.

2 cl, 6 ex

Description

The invention relates to the refining industry and is intended for use in the manufacture of catalysts for the isomerization of C ₄ -C ₆ paraffin hydrocarbons of normal structure.

In industrial practice, several types of catalysts are used for isomerization of light hydrocarbons: 1) zeolite-containing, 2) based on chlorinated eta-alumina, 3) based on fluorinated gamma-alumina, and 4) based on sulfated zirconium oxide. The latter type of catalyst is finding wider application and seems to be the most promising.

Zirconium catalysts are capable of replacing all of the other types of isomerization catalysts listed above; they are close in efficiency to chlorinated catalysts, and they are quite simple in technology and devoid of the disadvantages of chlorinated contacts, D do not require deep drying of the system and purification of raw materials from a number of harmful impurities, and also do not need constant replenishment of chloragent.

The introduction of sulfate ions into the composition of the zirconium oxide composition leads to the production of super acid exceeding 100% sulfuric acid in acidity, which predetermines high activity in acid catalysis reactions, in particular, in alkane isomerization. All known methods for the preparation of zirconium oxide catalysts differ in the details of the technology and the parameters of the individual stages.

The technology for preparing these catalysts is as follows. Salts of zirconyl mineral acids - zirconyl chloride, zirconyl nitrate, etc. are used as the initial zirconium-containing material, which are converted into zirconium hydroxide (Zr (OH) ₄ ) by precipitation with an alkaline agent (ammonia or sodium hydroxide). The deposition method is described in detail in the literature and mastered in industry, so you can use ready-made commercial zirconium hydroxide obtained by a known method as a source of zirconium [RF Patent No. 2236291, 2004, US patent No. 7252767, 2007].

As a rule, already at this stage sulfate groups are introduced into zirconium hydroxide in order to obtain their desired content in the finished catalyst.

Next, sulfated zirconium hydroxide (powder or “cake”) is mixed with a binder - usually pseudoboehmite aluminum hydroxide, peptized with mineral acids and granulated, usually by extrusion. The extrudates are calcined in air at high temperature, and to obtain the maximum content of active tetragonal modification, calcination is carried out at a temperature of at least 650-750 ° C.

Then, a hydrogenating metal — usually platinum from an aqueous solution of platinum chloride hydrochloric acid — is applied in a known manner to the surface of the obtained support.

After the final calcination and reduction in hydrogen by known methods, the catalyst is used in the isomerization process.

Known methods for the preparation of catalysts containing, along with sulfated zirconium oxide, aluminum oxide and a metal of group VIII (Pt) additives promoters from among manganese oxide, titanium oxide, tungsten oxide, etc. (RF Patent, No. 2401162, 2010, RF patent No. 2321575, 2008, US patent No. 7041866, 2006).

A composition of metal oxides is prepared by mixing zirconium hydroxide, aluminum, titanium, manganese, tungsten, etc., while observing the required molar ratio of oxides, followed by extrusion, drying and calcination at a temperature of 500-900 ° C. The resulting composition of metal oxides is impregnated with solutions of metal compounds of the 8th group of the Periodic system of elements. Sulfuric acid is added to the impregnation solution. After impregnation, the catalyst is calcined at a temperature of 400-700 ° C. The isomerization of n-butane on the resulting catalyst is 47-50% with an isomerization depth not higher than 42%. In addition, the promotion of the catalyst complicates the technology of preparation of the catalyst, while the activity of the catalyst increases slightly.

A known method of preparing an isomerization catalyst based on sulfated zirconium oxide, in which a platinum group metal, mainly palladium, is used as a hydrogenating component (US Patent No. 5516964, 1996). Despite the obvious cheapening of the contact, replacing platinum with palladium does not give an increase in activity and in some cases reduces the stability of the catalyst and its resistance to the action of poisons. The conversion of n-butane does not exceed 49% with an isomerization depth of not more than 43%.

A known method of preparing a catalyst based on sulfated zirconium oxide, which consists in precision regulation of the distribution of platinum on the surface, which allows to optimize the composition of the catalyst and stabilize its activity. However, the activity of such a catalyst is still insufficient (45-49% conversion, isomerization depth up to 43%) (US patent No. 7026268, 2006).

A known catalyst based on sulfated zirconium oxide and a method for its preparation, comprising the use of various organic complexes, which, while maintaining certain synthesis parameters, allows to obtain a highly effective isomerization catalyst. In addition to the complexity of the proposed technology, the catalyst obtained by this method has insufficiently high activity. The conversion of isomerization of n-butane does not exceed 48% at a low depth of isomerization (US patent No. 5786294, 1998, RF patent No. 2264256, 2004).

The closest to the proposed technical essence and the achieved effect is a method of preparation of zirconium oxide catalyst, which involves the synthesis of zirconium hydroxide, its sulfation by treatment with sulfuric acid, mixing with a binder - aluminum hydroxide, peptization of a mixture of hydroxides with an acid solution, including sulfuric acid, heat treatment of the carrier, impregnation of the carrier platinum with a platinum-containing solution with the addition of hydrochloric acid, followed by drying and calcination in a stream of air at a temperature of 5 00 ° C. The introduction of a mixture of acids into the composition of hydroxides leads to the predominant interaction of sulfuric acid with aluminum hydroxide (and not with zirconium hydroxide), which reduces the proportion of ZrOSO ₄ in the composition of the catalyst and thereby reduces the activity of the catalyst in isomerization. In addition, the proposed method makes it difficult to obtain the maximum possible active tetragonal phase and reduces the mechanical strength of the contact [US Pat. RF №2171827, 2001].

In order to increase the isomerizing activity of the catalyst based on sulfated zirconium oxide, increase its mechanical strength and simplify the technology of preparation of the catalyst, it is proposed to prepare the catalyst according to the following technology.

Sulfated zirconium hydroxide is mixed with a portion (up to 50% of the total content) of aluminum hydroxide (preferably pseudoboehmite of alcoholate origin with a particle size of 5 to 90 microns), the resulting mixture is peptized with a total calculated amount of sulfuric acid and up to 3/4 of the calculated amount of nitric acid. The remaining amounts of aluminum hydroxide and nitric acid are added to the peptized product. The resulting peptized mass is granulated by extrusion, the formed granules are dried and calcined. Platinum is applied to the calcined granules by soaking them with an aqueous solution of hydrochloric acid platinum, after which the resulting catalyst is dried and calcined at a temperature of 400-500 ° C.

The ratio of zirconium and aluminum oxides in the finished catalyst is from 85:15 to 70:30, respectively.

A significant difference of the proposed method is the introduction of aluminum hydroxide in a mixture with sulfated zirconium hydroxide in two doses. Initially, the entire amount of zirconium hydroxide and not more than 50% aluminum hydroxide are peptized with the total calculated amount of sulfuric acid and up to% of the amount of nitric acid, then the remaining quantities of aluminum hydroxide and nitric acid are added to the obtained peptized product.

Obtained by the proposed method, the catalyst was tested in test isomerization reactions:

1) n-butane at a temperature of 160-220 ° C, atmospheric pressure, relative volumetric feed rate of 1 hour ^-1 , hydrogen flow rate from 0.05 to 0.25 mol of H ₂ per mole of hydrocarbon;

2) pentane-hexane fraction at a pressure of 30 MPa, a volumetric feed rate of 2.0 hours ^-1 , and a temperature of 140 ° C. In the first case, the effectiveness of the catalysts was judged by the total conversion of n-butane (in wt.%) And the depth of isomerization, expressed as iC ₄ / ΣC ₄ , where “iC ₄ ” is the content of isobutane in the catalysis, “SC ₄ ” is the total content of butanes in catalysis. In the second, the yield of liquid catalysis was evaluated, as well as the yield of isopentane (iC ₅ / ΣC ₅ ) in the sum of C ₅ hydrocarbons and the yield of 2,2-dimethylbutane (2,2-DMB) in the sum of C ₆ hydrocarbons (2,2-DMB / ΣC ₆ ) in wt.%.

EXAMPLE No. 1

Take 100 g of the finished sulfated zirconium hydroxide (product of the company "MEL") in the form of a powder containing 10% bound sulfate ions and having an SPP at 850 ° C of 29 wt.%. The calcined product based on this corresponds to 71.0 g It contains 10% of the ions SO4 ^2- or _4, the rest - of zirconium oxide, namely - 63.9 g

Catapal A-type aluminum hydroxide powder was taken as the second component in a total amount of 29.00 g, which in terms of the calcined product (Al ₂ O ₃ ) is 21.17 g (SPP at 850 ° C = 27 wt.%). Catapal A pseudoboehmite is synthesized from aluminum alcoholates, and the particle size of the powder (d ₅₀ ) is 5-10 microns.

Half of the indicated amount of pseudoboehmite, 14.5 g, is mixed with a powder of sulfated zirconium hydroxide (100 g) in dry form, homogenizing the mixture by stirring for 15 minutes in a Werner mixer with Z-shaped blades. To the resulting homogeneous mixture was added 0.635 ml of concentrated (12 N) nitric acid and 2.11 g of 100% sulfuric acid diluted in 120 ml of distilled water. Stirred for 0.5 hours, and then another 14.5 g of pseudoboehmite and again 0.635 ml of concentrated HNO _{3 were} added to the resulting composition. The peptized mass is stirred for 0.5 hours, and then granulated by extrusion through a matrix with a hole diameter of 2.0 mm PPP mass, ready for molding, is approximately 50 wt.%.

The formed extrudates of the carrier are dried in an atmosphere of air at a temperature of 120 ° C for 2 hours, and then calcined at a temperature of 700 ° C for 2 hours, withstanding a rate of temperature increase of 50 ° C / hour during heating.

The obtained ~ 78 g of calcined carrier granules are used for platinum deposition. An impregnation solution is prepared comprising 0.42 g of H ₂ PtCl ₆ (0.2 g of Pt), the rest is water. The total volume of the solution is 28 ml.

The prepared solution is poured onto a weighed portion of the carrier with continuous stirring and the system is kept in contact for 1 hour without external heating.

At the end of the impregnation, the catalyst is dried at a temperature of 100-120 ° C for 1 hour, and then calcined in air at 400 ° C for 2 hours.

Before use in the test isomerization reaction, the catalyst is reduced with electrolytic hydrogen at a temperature of 150-200 ° C for 1 hour.

The finished catalyst has a ratio of 75% zirconia to 25% alumina and contains 0.28% Pt and 6.4 wt.% SO ₄ ^2- .

Testing was carried out using pure n-butane as a raw material at a temperature of 180 ° C, atmospheric pressure, a feed rate of 1 h ^-1 and a hydrogen flow rate of 0.25 mol per mole of butane.

Under these conditions, the synthesized catalyst sample showed a n-butane conversion of 51% at an isomerization depth of 44%.

When testing the isomerization of the pentane-hexane fraction under the above conditions, the following results were obtained: the yield of liquid catalysis is 90.2%, the yield of isopentane is 69.9%, the yield of 2.2-DMB is 29.1 wt.%.

EXAMPLE No. 2.

The same as in example No. 1, but pseudoboehmite taken in an amount of 29 g is divided into two portions: 30 and 70% of the total amount, or 8.7 and 20.3 g, respectively, which are administered respectively on the 1st and 2nd th stage. The consumption of nitric acid in the first stage is reduced to 0.38 ml, in the second - increased to 0.89 ml; however, the consumption of sulfuric acid and the method of its introduction do not change.

The rest is as in example No. 1.

In test tests in the isomerization of n-butane, a catalyst sample gave the following results: butane conversion - 52%, isomerization depth - 43%.

In the isomerization of the pentane-hexane fraction, liquid catalysis was obtained with a yield of 90.1%, while the yield of isopentane was 69.8%, and the yield of 2.2-DMB-29.3 wt.%.

EXAMPLE No. 3

The same as in example No. 1, but with a changed ratio of the main oxide components, namely: 85% ZrO ₂ + 15% Al ₂ O ₃ (pseudoboehmite is divided into two equal halves, as in the first example). At the same time, the consumption of sulfuric acid is not changed, and the consumption of nitric acid is reduced by a factor of 2, with half of it being introduced together with sulfuric acid, and the second half after adding the remaining amount of aluminum hydroxide.

The test results of the catalyst in the isomerization of butane:

the conversion of n-butane is 53%, the depth of isomerization is 44%.

EXAMPLE No. 4

The same as in example No. 1, but the zirconium and aluminum oxides were taken in a ratio of 70: 30% and 1.41 g of H ₂ SO _{4 was} additionally added to the platinum impregnating solution.

The finished catalyst contains 6.9% SO ₄ ^2- .

The remaining parameters and ratios do not differ from those in example No. 1.

The results of a test test using butane as a raw material: n-butane conversion - 50%, isomerization depth - 46%.

EXAMPLE No. 5

The same as in example No. 1, but pural pseudoboehmite powder of the brand Pural SB-1 (Sasol) with a predominant particle size of the powder (d ₅₀ ) of 90 μm was used as the starting aluminum hydroxide.

The finished catalyst contains 5.9% sulfate ions.

Test results: n-butane conversion - 50%, isomerization depth - 44%.

EXAMPLE No. 6

The same as in example No. 1, but with a changed proportion of aluminum hydroxide (in terms of oxide) introduced in the first peptization stage, namely: 5% Al ₂ O ₃ (pseudoboehmite is divided into two parts, as in the first example, but added in a proportion of 5: 95%). The carrier contains a mixture of zirconium and aluminum oxides and sulfate ions (about 10%), while 100 g of the oxide mixture contains 70 g of ZrO ₂ and 30 g of Al ₂ O ₃ , and 1.5 g of aluminum oxide (in the form of hydroxide) is introduced in the first stage, which is 5% of the total amount, and in the second stage, the remaining amount is introduced - 28.5 g of Al ₂ O ₃ or 95%. Thus sulfuric acid consumption is not changed, and the consumption of nitric acid is increased to 2 times, and _^3/4 is administered in the first step (0.95 mL) and ^{a _1/4} - after addition of a second portion of aluminum hydroxide (0.32 ml) .

The test results of the catalyst in butane isomerization: n-butane conversion - 55%, isomerization depth - 45%.

Claims (2)

1. A method of preparing a catalyst for the isomerization of C ₄ -C ₆ hydrocarbons, comprising mixing a powder of sulfated zirconium hydroxide with a binder powder - aluminum hydroxide, plasticizing a mixture of powders by peptization with a solution of a mixture of mineral acids, granulation by extrusion, heat treatment of the carrier, deposition of platinum and heat treatment of the catalyst, characterized in that the contacting of the powders with a mixture of acid-peptizing agents is carried out in two steps: first, the entire amount of sulfated gypsum is peptized zirconium oxide and part of aluminum hydroxide, using the full calculated amount of sulfuric acid and up to 3/4 of the amount of nitric acid, then the remaining amount of aluminum hydroxide and the remaining amount of nitric acid are added to the obtained peptized product, and the ratio of zirconium and aluminum oxides in the finished catalyst is from 85 : 15 to 70:30, respectively. 2. The method according to claim 1, characterized in that pseudoboehmite of alcoholate origin with a particle size of 5 to 90 microns is used as a binder.