JP3127556B2 - Method for producing isobutane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing isobutane by isomerizing n-butane.

Isobutane is industrially important as an alkylating agent, and isobutene produced by dehydrogenation is a valuable raw material in the petrochemical industry. Many industrial processes using isobutene as a starting material have been developed. ing.

[0003]

In the isomerization reaction, a Friedel-Crafts metal halide catalyst such as aluminum chloride or aluminum bromide is used together with anhydrous hydrogen chloride or hydrogen bromide, and a metal component having a hydrogenation function, for example, nickel, It can be broadly classified into three types: a so-called dual-function catalyst in which platinum, palladium and the like are supported on a heat-resistant oxide such as alumina or zeolite, and a composite catalyst of platinum-alumina-halide.

[0004]

However, since a catalyst mainly using a metal halide such as aluminum chloride is highly corrosive, it is necessary to use a corrosion-resistant alloy in a main part of the apparatus.

On the other hand, so-called bifunctional catalysts such as platinum-alumina do not have the drawbacks of aluminum chloride catalysts, but in order to obtain a practical reaction rate, a method of sublimating or impregnating such catalysts with aluminum chloride. , CC
It must perform an activation treatment for the reaction and a method for introducing onto the catalyst by adsorption or chemical bonding a halogen element is reacted gases and their catalyst containing vapor of haloalkanes, such as l _4. In this case, a step for separating hydrogen chloride by-produced during the reaction from the isobutane must be provided, and the step is complicated.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conventional n
The present invention provides a method for producing isobutane which does not have the above-mentioned disadvantages of the method for isomerizing butane, specifically, a method for producing isobutane by isomerizing n-butane in the presence of a heteropolyacid catalyst.

The heteropolyacid used as a catalyst in the present invention contains at least one element selected from the group consisting of Mo, W and V as a condensed coordination element, and further condenses another element such as Nb or Ta. It may be contained as a coordination element. The central elements of this heteropolyacid are P, Si, As, Ge, Ti, Ce, T
h, Mn, Ni, Te, I, Co, Cr, Fe, Ga,
One kind selected from the group consisting of B, V, Pt, Be and Zn, and the condensed coordination element / center element (atomic ratio) in the heteropolyacid is 2.5 to 12. Further, as the heteropolyacid, not only a monomer but also a polymer such as a dimer and a trimer can be used.

Specific examples of these heteropolyacids include phosphomolybdic acid, phosphotungstic acid, phosphomolybdovanadic acid, phosphomolybdung tungstovanadic acid, phosphorus tungstovanadic acid, phosphomolybdniobic acid, silicotungstic acid, silicomolybdic acid , Molybdo tungsten tungstic acid, silicate molybdenum tungstovanadic acid, borotungstic acid, boromolybdic acid, boromolybdo tungstic acid, boromolybdo vanadic acid, boromolybdo tungstovanadate, cobalt molybdate, cobalt tungstate, arsenic Molybdic acid, arsenic tungstic acid and the like.

These heteropolyacids may be used as a commercial product or may be synthesized from starting compounds. As a raw material compound for the synthesis, salts such as nitrates, ammonium salts, organic acid salts, and halogen compounds of each element, and oxides can be used in combination.

Platinum and palladium are nitrates of these metals,
Halogen compounds, ammine complexes, organic complexes and the like can be used.

It is effective to add platinum or palladium so that the weight ratio with respect to the heteropolyacid is 0.0001 to 20.

Although the catalyst used in the method of the present invention is effective without a carrier, it is preferably used by being supported on an inert carrier such as silica, silicon carbide or diatomaceous earth.

The amount of the heteropolyacid used is not particularly limited, but is usually at least 1% by weight, preferably at least 10% by weight, based on the total weight of the catalyst.

It is effective that the platinum or palladium supported on the finished catalyst is 0.01 to 20% by weight.

As a method for preparing the catalyst used in the present invention, various known methods such as an evaporation to dryness method, a precipitation method and an oxide mixing method can be used. For example, the following method is mentioned as an example of the evaporation to dryness method. An aqueous solution in which hexachloroplatinic acid is dissolved in pure water is prepared. Separately, an aqueous solution in which a heteropoly acid is dissolved is prepared. The heteropolyacid aqueous solution is added to the platinum acid aqueous solution and stirred. Thereafter, the solid obtained by heating and concentrating and evaporating to dryness is dried, molded and calcined by air. The firing temperature is 250 to 500 ° C, preferably 300 to
400 ° C.

In practicing the present invention, the reaction temperature is 100
To 400 ° C, preferably 200 to 350 ° C. The reaction pressure is several tens mmHg to 90 Kg / cm ² G, preferably 1
５０50 Kg / cm ² G. At the start of the reaction or at the inlet of the flow reactor, the molar ratio of hydrogen to n-butane is 0.1
-20 is required, and preferably in the range of 0.5-10. The space velocity is from 300 to 10,000 hr ^-1 , preferably from 500 to 3000 hr ^-1 .

The reaction gas may contain a gas inert to the reaction, for example, nitrogen, helium, argon or the like.

[0018]

EXAMPLES The preparation method of the catalyst according to the present invention and a reaction example using the catalyst will be specifically described below.

Example 1 2 g of hexachloroplatinic acid was dissolved in 200 ml of pure water and stirred. Separately, phosphotungstic acid 8 in 200 ml of pure water
An aqueous solution in which 0.7 g was dissolved was added with stirring. Finally, 375 g of Snowtex N (manufactured by Nissan Chemical Industries, Ltd.), which is colloidal silica, was added, and the mixture was heated, concentrated and evaporated to dryness with stirring. The obtained solid was dried at 120 ° C. for 12 hours, molded, and fired at 350 ° C. for 3 hours in an air stream.

5 g of the catalyst was charged into a stainless steel fixed bed reactor, heated to 300 ° C., and reduced with hydrogen for 1 hour. Next, n-butane, hydrogen and nitrogen were passed at a molar ratio of 1: 4: 11, and the space velocity was set to 1000.
h- ¹ was introduced into the catalyst layer. The product was analyzed by gas chromatography to find that the conversion was 16% and the selectivity for isobutane in the product was 93%.

Example 2 A reaction was carried out in the same manner as in Example 1 except that n-butane and hydrogen were passed at a molar ratio of 1: 4. As a result, the conversion was 24% and the selectivity for isobutane in the product was 96%.
Met.

Example 3 86.5 g of heteropolyacid as silicotungstic acid
A catalyst was prepared and reacted in the same manner as in Example 1 except that was used. As a result, a conversion of 25% and a selectivity of isobutane in the product of 91% were obtained.

[0023]

When the heteropolyacid according to the present invention is used, it is less corrosive and the process complexity due to a special activation treatment of organic chlorine or the like is eliminated.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-255132 (JP, A) JP-A-3-48629 (JP, A) JP-A-2-14739 (JP, A) JP-A-1- 228923 (JP, A) JP-A-63-72349 (JP, A) JP-A-62-230734 (JP, A) JP-A-52-138449 (JP, A) JP-A-49-35305 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C07C 5/27 C07C 9/00-9/22 C07B 61/00 300

Claims (1)

(57) [Claims] 1. A process for producing isobutane, wherein n-butane is isomerized in the presence of a heteropolyacid and platinum or palladium.