LT3678B - Process for activating catalyst precursors for the dehydrogenation of c2-c5 paraffins and a catalytic composition activated by the process - Google Patents

Abstract

Method of activation of catalytic dehydration or paraffin composition containing gallic, aluminium oxide, silica dioxide (not necessary) and/or one or more alkali or earth alkali metals and covering thermal activation in the air and a "post-activation" afterwards consists of the following stages: - oxidation by air and/or by oxygen or inertia gases and oxygen mix; - blow out inertia gases; - reduction by hydrogen ora mix of hydrogen and inertia gases. Catalytic composition is activated by the method indicated has gallic, aluminium oxide and by choice one or more of alkali or earth alkali metals. Aluminium oxide is in a δ or θ phase or δ + θ or δ + θ + α phase mix.

Description

The present invention relates essentially to a process for the dehydrogenation of C ₂ to C ₅ paraffins (i.e. having from 2 to 5 carbon atoms) to the activation of the corresponding precursors of the olefin catalysts and to the composition activated in the manner indicated.

Olefins are important intermediates in the production of widely used chemicals: polypropylene, MTBE, high octane gasoline, alkylated derivatives and many other products.

Despite the growing demand for such derivatives, the expansion of their manufacturing industry is often limited by the lack of olefins (e.g., isobutene in the production of MTBE).

This requires the search for sources of olefins other than the conventional (FCC - pseudo- cracked, cracked) olefins. Among them, dehydrogenation of light paraffins is probably the most important. Although simple in terms of stoichiometry, it has thermodynamic and kinetic problems.

The reaction is endothermic and regulated by thermodynamic equilibrium; for example, it requires the dehydrogenation of C ₂ to C ₅ paraffins above 500 ° C with economically acceptable conversion for each cycle. In addition, the system requires constant heating to ensure the endothermic nature of the reaction.

Although operating at high temperatures, the rate of dehydrogenation is low and this reaction must be carried out using a suitable catalyst. In order to ensure the selectivity of the reaction with respect to the synthesized olefin and to minimize the side reactions of isomerization, cracking and coking, it must be thermally stable.

The inevitable formation of coke on the catalyst causes a progressive decrease in catalytic activity and requires periodic regeneration.

It took a lot of serious effort to find catalytic compositions that would meet the process requirements of a particular type. In this regard, the patent literature describes many catalytic compositions, either on the basis of precious metals or in combination with other chemical compounds (U.S. Patent Nos. 3531543, 4786625, 4886928, EP 351067), or of metal oxides in combination with promoters and generally consisting of deposited on a substrate Cr ₂ O ₃ (U.S. Patent Nos. 2945823, 2956030, 2991255; British Patent No. 2162082). However, both options have their drawbacks. In order to maintain activity, catalysts for dehydrogenation require special treatment from the recovery of precious metals (U.S. Patent No. 4,438,288). Chromium oxide-based catalysts include environmental problems and decreasing activity over time if not adequately stabilized.

Recently, a number of patents have been published offering catalytic compositions containing gallium or its compounds for dehydrogenation of paraffins (U.S. Pat. No. 40,565,776) or aromatization (U.S. Pat. No. 509825, AU No. 565365, U.S. Pat. No. 4704494). which yield unsaturated compounds with low conversion and selectivity.

We have unexpectedly found a new method of activating catalysts capable of converting C ₂ to C ₅ paraffins to provide relatively high conversion and particularly selectivity.

A key aspect of the present invention is a process for activating a catalyst precursor containing gallium, alumina, possibly SiLT 3678B lithium dioxide and / or one or more alkali metals, comprising thermal activation in air at 450-1000 ° C followed by post-activation, consisting of the following stages:

- oxidation with air and / or oxygen or with an inert gas mixture with an oxygen concentration of at least 5% by volume for a period of 1 to 180 minutes (preferably 30 to 90 minutes) at 500 to 1000 ° C (preferably 550 to 700 ° C) ;

flushing with inert gas for 1 to 10 minutes (preferably 3 to 5 minutes);

reduction with hydrogen or a mixture of at least 5% by volume of hydrogen and an inert gas for a period of from 1 to 120 minutes (preferably from 30 to 90 minutes) at 450 to 800 ° C (preferably from 500 to 700 ° C).

Inert gas may be argon or helium, and purge may also use CO ₂ . In our experiments, we have found that this process of activation for a new catalytic composition is new, with improved catalyst performance (especially for olefin selectivity) compared to the process described above, with known catalysts.

Further in accordance with the invention, a C ₂ -C ₅ paraffins dehydrogenation catalytic composition containing gallium, alumina, silica and possibly one or more alkali or alkaline earth metals, in that it can produce ₂ O ₃ in the form of from 00:10 to 33.6% by weight (preferably 0.50% to 2.5%), silica 0.08 to 3% by weight, alkali metal in the form of 0 to 5% by weight and the remainder up to

100% is alumina in the δ or Θ phase, or in the δ and θ phase mixture, or in the phase mixture (δ + θ + a).

If an alkali metal (preferably potassium) is used, its content in the form of K ₂ O is preferably 0.1 to 1% by weight.

This composition should be activated as described above. The process for its preparation consists essentially of dispersing the gallium compound on a carrier consisting of alumina (in either a δ or θ phase or a mixture of δ + θ or δ + θ + a phases) and silica.

Some methods of dispersing gallium on a carrier are provided below, but are not limited to the invention. The dispersion procedure may consist of impregnating the indicated carrier with gallium-containing precursor solution and subsequent drying and calcining, or may be effected by ion exchange with gallium-salt solution and subsequent liquid removal, drying and activation of the solid product, or by adsorption of volatile gallium compounds on the surface by calcining the solid product.

Of the above procedures, moistening the carrier and immersing it in a solution containing the precursor is preferred.

If alkaline or earth alkaline metal is used, its insertion methods:

- parallel loading of the carrier;

- addition of alkali metal to the precursor carrier prior to dispersion on the gallium;

treatment of a solid product with an ionic exchange, impregnation with alkali or alkaline - earth metals, and

The present invention further relates to the use of a catalyst precursor activated in the above manner and consisting of gallium, alumina, possibly silicon oxide and / or one or more alkali compounds, or the use of the above-mentioned catalytic composition and activated in the specified manner C ₂ - C _{5 for} dehydration of paraffins.

The method for dehydrating paraffins is known to those skilled in the art. The C ₂ - C ₅ paraffins are fed into the reactor, preferably in a fluidized bed using a suitable catalyst and at a reaction temperature of 450 to 700 ° C and a pressure of 1 to 2 kg / cm ³ with GHSV between 100 and 10000 or ¹ (carbohydrate volume / val.catalyst liters).

The following are some examples, but should not be construed as limiting the present invention in any way.

EXAMPLE

Microspherical pseudobohemite is prepared by spray drying a suspension of aluminum hydroxide obtained by precipitation from a solution of aluminum and silicon salts, with the addition of silica (1, 2% by weight) with a particle diameter of 5 to 500 µm. An example of pseudobohemite is heat treated: initial calcination at 450 ° C for one hour, followed by calcination at 1070 ° C for 8 hours in a stream of water saturated with steam. During calcination, the product has a specific surface area of 100 m / g and consists of δ, θ, and α alumina as in Figs. 1 in the X-ray spectrum. Immerse 150 g of this alumina by wetting with an aqueous solution of 8.21 Ga (NO ₃ ) ₃ .9H ₂ O and 0.78 KNO _{3 in} 67.3 cm ^{3 of} deionized water. The impregnated material is left for 24 hours at room temperature and then dried at 150 ° C for 24 hours. Subsequently, the LT 3678 B dried material is activated for 4 hours in a stream of dry air at 600 ° C.

The composition of the catalyst composition (expressed as oxides of both ends and dowels) is 1.21% Ga ₂ O ₃ , 0.24%

K ₂ O, 1.57%. SiO ₂ , zator characteristic of the pseudosolid

Al ₂ 0 ₃ - Balance up to 100

Table 1 and Table 2, respectively, for the dehydrogen layer of catalipropane and butane. After the catalyst tests it is further activated in the following cycles: 60 minutes oxidation with air, 3 minutes purge with nitrogen, 60 minutes reduction with hydrogen at 650 ° C. After 180 hours of activation in this manner, the catalyst is again used to dehydrate the same paraffin (Tables 3 and 4).

Activation in the oxidation and reduction cycles was used for all the catalysts described in the examples below.

The following table shows the catalytic activity of this catalyst and of the subsequent catalysts activated in the above manner by dehydrogenation of isobutane at the same temperature and at the same volumetric rate as in the second example of U.S. Patent No. 4056576.

EXAMPLE

Gamma alumina (X-ray spectrum Fig. 2), having a specific surface area of 250 m / g and a total porosity of 0.55 cm / g, is obtained by calcining pseudobohemite (used in the previous example) at 450 ° C for 1 hour and then steam-saturated water for 4 hours. in current at 650 ° C. 150 g. gamma alumina is soaked in 82.5 cm ³ aqueous solution containing the same quantities of dissolved Ga (NO ₃ ) ₃ .9H ₂ O and KNO ₃ as in Example 1, in the same manner and with the same composition of catalyst. Its characteristics are shown in Tables 1, 2, 3, 4 and 5.

EXAMPLE

150 g of calcined alumina containing the components of Example 1 (delta, theta and alpha) are impregnated with an aqueous solution of 8.18 g of Ga (NO ₃ ) ₃ .9H ₂ O in 67.5 cm ^{3 of} deionized water. Immersion, drying and activation are carried out in a known manner (Example 1). The composition of the catalyst composition is 1.21% Ga (N0 ₃ ) ₃ .9H ₂ O

1.58% SiO ₂ , Al ₂ O ₃ - up to 100%. The characteristics are presented in Tables 1, 2, 3, 4 and 5.

EXAMPLE

The catalyst thus obtained is obtained as follows: 0.76% Ga ₂ O ₃ , 1.58% SiO ₂ , Al ₂ O ₃ - up to 100% by soaking 150 g of the alumina of Example 3 with 4.5 g of dissolved Ga (NO ₃ ) ₃ .9H ₂ O. The catalytic properties of the system are given in Tables 1, 2, 3, 4 and 5.

EXAMPLE

The same amount of alumina as in the sample is impregnated with 67.5 cm ^{3 of a} solution containing 28.1 g of dissolved Ga (NO ₃ ) ₃ .9H ₂ O. The composition of the catalyst in this case is: 3.76% Ga ₂ O ₃ , 1.54% SiO ₂ and A1 ₂ O ₃ to 100%. The characteristics are presented in Tables 1, 2, 3, and 5.

EXAMPLE

The alumina used in Example 2 is impregnated with a specific composition of Ga (NO ₃ ) ₃ .9H ₂ O to give the following composition of catalyst: 1.21 Ga ₂ O ₃ ,

1.58% SiO ₂ , Al ₂ O ₃ - up to 100%. The properties are presented in Tables 1, 2, 3, 4 and 5.

EXAMPLE

The pseudobohemite obtained in the manner described in Example 1 is heat treated for one hour at 450 [deg.] C. and then for 8 hours at 380 [deg.] C. in a stream of saturated water. The product obtained has a specific surface area of 128 m ² / g and a total porosity of 0.48 cm ³ / g. It is structurally composed of delta alumina (X-ray structural spectrum shown in Figure 3). 150 g of calcined alumina were impregnated with 78 cm ^{3 of} an aqueous solution obtained by dissolving 8.18 g of Ga (NO ₃ ) ₃ .9H ₂ O. Composition of catalyst composition: 1.21% Ga ₂ O ₃ , 1.58% SiO ₂ , Al ₂ O ₃ - up to 100%. Its catalytic properties are shown in Tables 1, 2, 3, 4 and 5.

EXAMPLE

The microspheroidal pseudobohemite obtained by the method of Example 1 but not containing silica having a particle size of 5-200 μg is calcined under the same conditions as in Example 2. The calcined product is gamma alumina (as shown in the diffraction spectrum in Fig. 4) with a specific surface area of 200 m ² / g and a total porosity of 0.52 cm / g. 150 g of calcined alumina impregnated with 78 cm ^{3 of} an aqueous solution containing 8.18 g of Ga (NO ₃ ) ₃ .9H ₂ O using the impregnation, drying and calcining procedure described in Example 1. The resulting catalyst composition contains 1.21% Ga ₂ O ₃ and the remainder Al ₂ O ₃ . Its catalytic characteristics are shown in Tables 1, 2, 3, 4 and 5.

EXAMPLE

150 g of microspheroidal silica having particles of 5 250 m in diameter, specific surface area of 254 m / g and total porosity of 0.6 cm / g Soaked in 90 cm solution containing the same amount as in Example 8 Ga (NO ₃ ) ₃ .9H ₂ O. In the manner described in Example 1. Final composition of catalyst: 1.21%

Ga ₂ O ₃ , SiO ₂ - up to 100%. The characteristics are presented in Tables 1, 2, 3, 4 and 5.

table

Catalytic activity after 4 hours activation in air at 600 ° C

Dehydrogenation of Propane

T = 590 ° C GHSV = 400 or ¹

EXAMPLES

1 2 3 4 5 6th 7th 8th 9th masses Oh, o SiO ₂ 1.57 1.57 1.58 1.59 1, 54 1.58 1.58 abs. 98.79 masses oh, 0 K ₂ O 0.24 0.24 abs abs abs abs abs abs abs masses oh, 0 Ga ₂ O ₃ 1.21 1.21 1.21 0, 67 3.76 1.21 1.21 1.21 1.21 masses o 0 ai ₂ o ₃ bil. bil. bil. bil. bil. bil. bil. bil. abs. masses o. o c ₃ h ₈ conv 10th 6th 12th 9.5 26th 9th 12th 19th 14th masses o. o C ₃ H _s Sel 76 50 77 82 60 58 68 56 74 masses o 0 c ₃ h ₆ 7.6 3 9.3 7.8 15, 6 5.2 8.2 10, 6 10.4 masses o 0 Sel (ΒΤΧ) abs. abs. abs. abs. 5 abs. abs. 2 abs.

table

Catalytic activity after 4 hours in air activation at 600 ° C

Dehydrogenation of isobutane

T = 580 ° C GHSV = 400 or

EXAMPLES

1 2 3 - 4 5 6th 7th 8th 9th % by weight SiO ₂ 1.57 1.57 1.58 1, 59 1.54 1.58 1, 58 abs. 98.79 % by weight K ₂ O 0, 24 0, 24 abs. abs. abs. abs. abs. abs. abs. % by weight Ο · 3 · 2θ3 1.21 1.21 1.21 0.67 3.76 1.21 1.21 1.21 1.21 % by weight A1 ₂ O ₃ bil. bil. bil. bil. bil. bil. bil. bil. abs. % by weight i - C ₄ CONV 34 32 40 35 40 38 28th 44 10th % by weight i - C ₄ Sel 83 50 63 74 40 41 55 25th 58 % by weight i - C ₄ Sel * 86 58 72 84 55 58 69 44 80 % by weight iC ₄ 28.2 16th 25.2 25.9 16th 15.6 15.4 11th 5.8 yield % by weight ί ”C 4 29.2 18.6 28.8 29.4 22nd 22.1 19.3 19.3 8th yield % by weight (ΒΤΧ) abs. 5 8.9 1 13th 1. 8th 6.4 11th 4 *: C ₄ H _s + C ₄ Hg + 2 Cis C ₄ Hg + trans c ₄ h ₈

table

Catalytic activity after 180 hours of activation in oxidation / reduction cycles

Dehydrogenation of Propane

T = 590 ° C GHSV = 400 or ¹

EXAMPLES

1 2 3 4 5 6th 7th 8th 9th wt% SiO ₂ 1.57 1.57 1.58 1, 59 1, 54 1.58 1, 58 abs. 98.79 mass% K ₂ O 0.24 0.24 abs. abs. abs. abs. abs. abs. abs. wt% Ga ₂ O ₃ 1.21 1.21 1.21 0, 67 3, 76 1.21 1.21 1.21 1.21 by weight% A1 ₂ O ₃ bil. bil. bil. bil. bil. bil. bil. bil. abs. by weight% C ₃ H ₈ ODNV 33 30th 39 30th 24th 37 31st 29th 10th by weight% C ₃ H ₆ Sel 89 82 84 85 76 77 81 60 67 by weight% C ₃ H _g 29.4 24.6 32.7 25.5 18.2 28.5 25.1 17.4 6.7 (output) wt% Sel (ΒΤΧ) 0.5 0.2 2.5 0.1 1 1.8 1.1 3.6 3.5 Table 4 Catalytic activity PO 180 hours activation

oxidation / reduction cycles

Dehydrogenation of isobutane

T = 590 ° C GHSV = 400 or ' ¹

EXAMPLES

1 2 3 4 5 6th 7th 8th 9th masses o 0 SiO ₂ 1.57 1.57 1.58 1.59 1, 54 1.58 1.58 abs. 98.79 masses o. 0 K ₂ O 0.24 0.24 abs. abs. abs. abs. abs. abs. abs. masses 0, o GcipOj 1.21 1.21 1.21 0, 67 3.76 1.21 1.21 1.21 1.21 masses o. 0 A1 ₂ O ₃ bil. bil. bil. bil. bil. bil. bil. bil. abs.

1 2 3 4 5 6th 7th 8th 9th mass% i - C ₄ CONV 48 46 52 41 38 53 43 44 16th by weight% i - C ₄ Sel 87 67 67 69 50 04/05 65 31st 55 % by weight - C ₄ Sel * 90 77 80 82 65 68.4 78 48 77 mass% i - C ₄ 41.7 30.8 34.8 28.3 19th 28.8 27.9 13.6 8.8 yield mass% i - C ₄ 43.2 35.4 41.6 33.6 24.7 36.3 33.5 21st 12.3 yield * % by weight (ΒΤΧ) 1 4.6 3.4 2.6 8th 8.5 4.7 13.5 3.2 *: i C ₄ H ₈ + C ₄ H ₈ + 2 Cis C ₄ H ₈ + trans C ₄ H 8th Table 5 Catalytic activity after oxidation / reduction cycles 180 hours activation Dehydrogenation of isobutane T = 550 ° C GHSV = 570 or " ¹ EXAMPLES 1 2 3 4 5 6th 7th 8th 9th

masses O o SiO ₂ 1.57 1.57 1.58 1.59 1.54 1.58 1.58 abs. 98.79 masses oh, 0 K ₂ O 0.24 0.24 abs. abs. abs. abs. abs. abs. abs. masses 0. o Ga ₂ O 3 1.21 1.21 1.21 0, 67 3.76 1.21 1.21 1.21 1.21 masses o 0 A1 ₂ O ₃ bil. bil. bil. bil. bil. bil. ' bil. bil. abs. masses 0, 0 i - C ₄ CONV 40 38 43 36 25th 45 34 36 8.4 masses O 0 i - C ₄ Sel 93 82 78 80 65 68 78 36 72 masses O O i - C ₄ Sel * 94 87.8 85 86 79 79 87 52 88

123456789 mass% i - C ₄ yield mass% i - C ₄ mass% (ΒΤΧ) *: i C ₄ H ₈ + C ₄ H

37.2 31.2 33.5 28.8 16.3 30.6 26.5 13 8

37.6 33.4 31 31 19.8 35.5 29.6 18.7 7.4

0.2 1.2 2.3 1.3 4 4.2 1.6 12 1.2 + 2 Cis C ₄ H ₈ + trans C ₄ H ₈

Claims (7)

DEFINITION OF INVENTION A process for the activation of a catalytic composition containing gall, alumina, optionally silica and / or one or more alkali or earth alkaline metals comprising thermal activation in air at 450-1000 ° C, characterized in that post-activation is used after said activation. (a) shall be carried out in the following stages: - oxidation with air and / or oxygen or a mixture of inert gases with an oxygen concentration of at least 5% by volume for a period of 1 to 180 minutes at 500-1000 ° C; - flushing with inert gas for 1 to 10 minutes; - reduction with hydrogen or a mixture of at least 5% by volume of hydrogen and an inert gas for a period of from 1 to 120 minutes at 450 to 800 ° C. 2. A process according to claim 1, wherein the oxidation is carried out for 30 to 90 minutes at 550-700 ° C, blown for 35 minutes and reduced for 30 to 90 minutes at 500-700 ° C. 3. Catalytic composition for the dehydrogenation of C ₂ -C ₅ paraffins containing gall, alumina, silica and optionally one or more alkali or alkaline-earth metals, characterized in that the gallium, Ga ₂ O _{3, is present in a} concentration of 0.1 to 33, 6% by weight, 0,08 to 3% by weight of silica, 0 to 5% by weight of alkali metal in the form of oxide, the remaining content up to 100% being alumina Θ either in the δ phase or δ + θ or δ + θ + α in the phase mixture. 4. The catalytic composition of claim 3, wherein the gallium in the form of Ga ₂ O ₃ is 0.5 to 2.5% by weight. 5. The catalytic composition of claim 3, wherein the alkali metal is potassium. 6. The catalytic composition of claim 5, wherein the potassium in the form of K ₂ O is from 0.1 10 to 1% by weight. Use of a catalytic composition obtained according to the process of claim 1 for the dehydrogenation of C ₂ -C ₅ paraffins. Use of a catalytic composition according to any one of claims 3 to 6 for the dehydrogenation of C ₂ -C ₅ paraffins.