DE3300982A1 - Process for the preparation of C2- to C4-olefins from methanol/dimethyl ether - Google Patents

Abstract

The application relates to a process for the preparation of olefins by reaction of methanol and/or dimethyl ether in the presence of zeolite catalysts at elevated temperature, in which, as catalysts, borosilicate zeolites are used which are shaped with binder mixtures of silica and alumina whose aluminium content is </= 10 % by weight. The advantage lies in an improved yield of C2-C4-olefins at the expense of the formation of higher hydrocarbons and the formation of undesired by-products such as methane.

Description

Process for the production of C2 - to C4-olefins from

Methanol / Dimethylether In recent times, efforts to use methanol are gaining ground to use for the production of olefins is of increasing interest.

Methanol can be obtained from coal, via coal gasification and manufacture of synthesis gas, easily produced with the help of proven technologies. Succeeds, Converting methanol into lower olefins economically is something they can do today They are also used for further processing in the chemical industry of coal as a raw material. In the past few years, therefore Processes have been developed that allow the production of olefins from methanol and / or Have dimethyl ether as an object.

Such a method is described in DE-OS 26 15 150, for example. An aluminosilicate zeolite ZSM> 5 is used as the catalyst, which is actually is an aromatization catalyst. However, the implementation can be done through various measures, in particular by shortening the residence time, steered in the direction of olefin formation will. further parameters favoring olefin formation are, in particular, the Dilution of methanol or dimethyl ether with inert, g2sen or

Steam. Experience shows that high olefin yields can only be achieved by a very strong dilution of methanol and / or dimethyl ether with inert gas or Water vapor are to be achieved.

Other known methods have the disadvantage of a low load capacity and rapid coking of the catalyst.

The dilution of the catalyst with binder should also be a for the formation of olefins there may be advantageous, but the hitherto used binders based on aluminum oxides side reactions and also deactivation caused by the catalyst.

It has now been found that C2 to C4 olefins can be obtained in high yield from methanol and / or dimethyl ether by catalytic conversion at elevated temperature obtained in the presence of zeolite catalysts if borosilicate zeolites are used as catalysts used with binder mixtures, made of silicon dioxide and aluminum oxide, whose Aluminum oxide content is <10% by weight, are deformed.

It is advisable to use e.g. binder mixtures for the deformation made of highly dispersed silicon dioxide and highly dispersed aluminum oxide, or binder mixtures made of highly dispersed silicon dioxide and boehmite or binder mixtures made of silica gel and boehmite.

It is advantageous to use catalysts in which the borosilicate zeolites with a highly dispersed binder, which consists of 90 - 98% by weight of highly dispersed SiO2 and 10 - 2% by weight of highly dispersed Al203 is formed. As another beneficial Suitable binders are silica gel and / or fumed silica mixed with boehmite (# 10 wt%). Highly dispersed SiO2 and A1203 are oxides that are derived from the corresponding halides have been prepared by pyrolysis. The surfaces of SiO2 measured by Brunner, Emmert, Teller in qm2 / g are 130 to 380 and the surfaces of Al203 100 to 200 m2 / g and the mixture of SiO2 and Al203 80 up to 170 qm2 / g.

It is essential to the invention that the catalyst have a residual aluminum oxide content must have; The presence of alumina is particularly advantageous in the Implementation of the conversion of methanol in a tubular reactor under isothermal conditions, around the first stage of the reaction - the dehydration of the methanol to dimethyl ether - 9 initiate. The boron zeolite stranded with aluminum oxide is more or less a bifunctional one Catalyst; the aluminum oxide is used to dehydrate the methanol to dimethyl ether and the boron zeolite converts this to the desired olefins. Exclusively require borosilicate zeolites stranded with silica gel or highly disperse silicic acids for the reaction with methanol temperatures whether erhalb 550 ° C or the feed or back-mixing of olefins or the use of pure dimethyl ether.

To produce the catalysts, the borosilicate zeolites are used with the respective binders or binder mixtures together to form tablets or Deformed strands.

When carrying out the process, methanol3 becomes that with dimethyl ether is in equilibrium, at a pressure between normal pressure and about 30 bar, preferably at 0 to 1 bar and at temperatures between 3000C and 650 ° C, preferably at 400 ° C to 550 ° C, implemented over the catalysts described above. The methanol can have a water content of up to 90% by weight; it is expedient to use it as the starting material Raw methanol, which contains around 20% water.

Other lower alcohols can also be added to the methanol be. The loading of the catalyst, expressed in WHSV = h-1 - g of methanol per g of catalyst and hour - is expediently chosen so that the starting materials as possible be implemented quantitatively, so that no separation and recycling problems for not converted 15tethanol / dimethyl ether arise. In general, therefore, the IESV in the range from 0> 5 to 50 h-1, preferably in the range from 2 to 15 -1.

The inventive method, the olefin selectivity in C2 to C4 range in the conversion of methanol to hydrocarbons, in particular significantly increased in the temperature range from 4000C to 6000C.

The formation of undesirable by-products such as methanol and aromatics, the aromatics produced when using aluminum oxide binders are caused by the Catalyst according to the invention strongly pushed back. This fact is beneficial in increasing the running time of the catalyst used.

Running time is the time between two regenerations. The overall life of the catalytic converter is also extended. The inventive The runtime improvement effect is particularly evident when implementing high Temperatures, e.g. in the range from 4500C to 550 ° C.

It is another advantage of the invention that one can implement it too C2 - to C4-olefins with raw methanol without further addition of inert diluents like N2, He or H20 can perform.

3ie «implementation of the inventive method is based on the The examples below are explained in more detail.

Examples Catalyst A (according to the invention) The boron zeolite is In a hydrothermal synthesis from 64 g SiO2 (fumed silica), 12.2 g H3BO3, 800 g one aqueous 1,6-hexanediamine solution (mixture 50:50) 170 ° C under autogenous pressure in a stirred autoclave. After filtering off and washing, the crystalline reaction product is dried at 110 ° C / 24 h and calcined at 500 ° C / 24 h. This borosilicate zeolite is composed of 94.2 Wt% SiO2 and 2.32 wt% 3203.

60 g of this borosilicate zeolite are mixed with 36.5 g of highly dispersed SiO2 and 3.5 g of highly disperse Al 2 O 3 formed into 2 mm strands at a pressure of 70 bar. The extrudate is dried at 110 ° C. for 16 hours and calcined at 5000 ° C. for 16 hours.

Catalyst B (according to the invention) Catalyst B becomes like catalyst A, only 30 g of highly dispersed SiO2 (Aerosil) and 10 g of boehmite are used.

Catalyst C (According to the Invention) The method of making catalyst C corresponds to that of catalysts A and B, except that 30 g of silica gel are used here and 10 g of boehmite used as a binder.

These catalysts A, 3, C are under isothermal conditions crude methanol with 20% by weight of water at 550 ° C. and ISiSV = 7.8 in a tubular reactor h-1 converted quantitatively with respect to the CH3OH used. The yields based on CH2 used are indicated in the table - columns A, B, C.

The following catalyst was used to compare the yields was tested under the same reaction conditions as catalysts A, B, C.

Catalyst D Catalyst D is obtained by extrusion of the borosilicate zeolite described above with boehmite in a ratio of 60:40. Drying takes place at 110 ° C. for 16 hours and calcination at 500 ° C. for 16 hours. ABCD catalyst C2H4 11.3 10.7 7.4 12.0 C3H6 42.6 39.8 39.5 32.9 C4H8 23.1 20.7 20.1 16.1 CH4 1.5 3.6 2.6 7.9 C2H6 0.3 0.6 0.3 0.6 C3H8 1.7 1.9 1.8 2.1 C4H10 1.1 1.3 1.2 1.2 C5 + aliphatics 12.2 10.5 15.0 9.4 C6 + aromatics 4.1 8.9 10.2 15.9 Running time h 15 10 10 7 g CH3OH / g catalyst 117 78 78 55

Claims (4)

Process for the production of olefins by catalytic Conversion of methanol and / or dimethyl ether in the presence of zeolite catalysts at elevated temperature, characterized in that the catalysts used are borosilicate zeolites used with binder mixtures of silicon dioxide and aluminum oxide, their Aluminum oxide content is <10 total%, are deformed. 2) Method according to claim 1, characterized in that for the deformation binder mixtures of highly dispersed silicon dioxide and highly dispersed Used alumina. 3) Method according to claim 1, characterized in that for deformation Binder mixtures of highly dispersed silicon dioxide and boehmite used. 4 The method according to claim 1, characterized in that for the deformation binder mixtures of silica gel and boehmite are used.