EP3177631A1

EP3177631A1 - Method for the direct synthesis of methyl chlorosilanes in fluidized-bed reactors

Info

Publication number: EP3177631A1
Application number: EP15801138.7A
Authority: EP
Inventors: Javad MOHSSENI; Jochen Gross; Konrad Mautner; Natalia SOFINA; Till Wüstenfeld
Original assignee: Wacker Chemie AG
Current assignee: Wacker Chemie AG
Priority date: 2014-12-10
Filing date: 2015-11-19
Publication date: 2017-06-14
Also published as: KR20170047373A; DE102014225460A1; WO2016091551A1; US20170305939A1

Abstract

The invention relates to a method for the production of methyl chlorosilanes by reaction of chloromethane with a contact mass, in which a mixture containing silicon, copper catalyst and promoter (contact mass 1) is fed into a first fluidized-bed reactor (fluidized-bed reactor 1), active contact mass (contact mass 2) is formed in the presence of chloromethane at 200 to 450 °C, a part of the contact mass (2) is removed from the fluidized-bed reactor (1) and fed into a second fluidized-bed reactor (fluidized-bed reactor 2) and reacted at 200 to 450°C with chloromethane, wherein, per time unit in fluidized-bed reactor (1), at least 20 parts by weight of contact mass 2 per 100 parts by weight of contact mass (1) are recycled, and wherein contact mass (2) fed into fluidized-bed reactor (2) and recycled in fluidized-bed reactor (1), is not cooled to a temperature below 150 °C after removal from the fluidized-bed reactor (1).

Description

Process for the direct synthesis of ethylchlorosilanes in

Fluidized bed reactors

The invention relates to a process for the direct synthesis of methylchlorosilanes by reacting with chloromethane

Contact mass containing silicon, copper catalyst and

Promoter.

In the Müller-Rochow direct synthesis, chloromethane is reacted with silicon in the presence of a copper catalyst and suitable promoters to methylchlorosilanes, in addition to the highest possible productivity (amount of silanes formed per unit time and reaction volume) and the highest possible selectivity - based on the target product dimethyldichlorosilane - Also, the highest possible use of silicon, combined with a safe and flexible operation of the entire system is required. For example, dimethyldichlorosilane is needed for the preparation of linear polysiloxanes.

The direct synthesis can be carried out batchwise or continuously. Continuous direct synthesis is carried out in fluidized bed reactors in which chloromethane is used simultaneously as fluidization medium and reactant. The required silicon is previously ground to a powder with a grain size up to 700 pm and mixed with copper catalysts and promoters to the contact mass; this is called fresh contact mass (= contact mass 1). Contact mass 1 is then introduced into the fluidized bed reactor and reacted at a temperature in the range of 260-350 ° C

brought. This forms active contact mass (= contact mass 2), ie contact mass containing active centers. (Lewis and Rethwish, Catalyzed direct reaction of Silicon, Stud. Org.

Chem. 1993, 49, 107) At these active sites, methylchlorosilanes are formed in an exothermic reaction. Unreacted chloromethane, the gaseous

Methylchlorosilanes and contact mass components leave the reactor. In order to ensure a high silicon utilization, these components can completely or partially the

Reactor can be supplied. For example, the coarser part of the entrained one or more cyclones

Contact mass particles separated from the gas stream and optionally recycled through intermediate collection container back into the reactor. Since it was activated

Components of the contact mass acts, these are one

Subset of contact mass 2.

The finest-grained, entrained particles (= contact mass 3), which in addition to silicon still high copper and minor constituent parts, must also be separated from the gas stream. This can be done for example by a gas filtration and / or one or more subsequent cyclones. By this procedure with discharge of reacted particles a continuous procedure can be made possible and a high

Silicon use be ensured.

Alternatively, the entire entrained solids flow can be separated and discharged from the system at all times or only at certain intervals.

For example, in US-A-4281149, Fig. 1 is such

System consisting of reactor, main cyclone with recirculation and post cyclone shown with dust collector. The crude silane is then separated from unreacted chloromethane and fed to a distillation. Purified, not

Reacted chloromethane can be fed back into the reactor.

The collected contact mass 3 must be discharged, since various minor elements and slag fractions, which are introduced with the silicon, in this product flow

enriched, and in the case of a complete return into the reactor, by catalytic effects of these impurities, the selectivity would be greatly reduced. Likewise, there would be an enrichment of inert

Side elements that would reduce the reactor runtime. The ratio of contact mass 1 to contact mass 2, in particular by the above-described feedback can vary widely. Contact compound 2 is an active contact material and already possesses sufficient copper content and promoters. Contact mass 2 is able to react with chloromethane at lower temperatures and to produce silanes with higher productivity and dimethyldichlorosilane selectivity. When mixing from

Contact mass 1 and contact mass 2 in the reactor can lead to an unfavorable distribution of catalyst and promoters, since catalyst constituents also bind to activated particles and, thus, e.g. unnecessarily increase the consumption of catalyst or cause a misallocation of the active ingredients.

To address these disadvantages, it is state of the art to thermally pretreat the fresh contact mass. In US

2003/0220514 describes a process in which silicon is treated with copper oxide and / or copper chloride at temperatures between 250-350 ° C thermally. The by-product is SiCl4. This preformed contact mass is not

formed silicon mixed and used in the Müller-Rochow synthesis. Concentrated contact masses can be prepared by this method which are diluted with catalyst-free silicon prior to alkylhalosilane synthesis. US 6528674B1 describes a 2-stage process in which silicon is treated with a copper compound at a temperature below 500 ° C, in a second step, this is pretreated

Contact mass aftertreated at temperatures above 500 ° C under inert gas. This contact mass thus treated is used in Müller-Rochow synthesis for the production of dimethyldichlorosilane. WO 99/64429 describes a method for Preparation of alkylhalosilanes by reaction of a thermally pretreated contact mass with alkyl halide. The pretreatment involves a reaction of silicon with

Catalysts and promoters at temperatures between 270 to 370 ° C with carbon monoxide, an increase in the

Production rate results.

DE102011006869 A1 describes a method in which a contact mass, in which silicon, copper compound,

Copper metal, zinc, zinc compound, tin, tin compound, wherein at least the copper catalyst or promoter contains a chloride, and mixing the mixture under a stream of carrier gas selected from N ₂ , noble gases, CO ₂ , CO and H ₂ at a temperature between Heated to 200 ° C and 600 ° C and used for the production of methylchlorosilanes.

The activation of the contact mass before the reaction with

For example, chloromethane through a prereactor with HCl is known from US-A-4864044. There is one in the examples

However, in the absence of silicon, copper catalyst and optionally tin promoters are described

Zinc promoters at about 325 ° C can be activated by HCl. The disadvantages of this form of activation can be seen in the fact that zinc or zinc compounds only after the

Activation can be added because zinc with HCl under the specified reaction conditions easily sublimable

Zinc chloride forms and thus can be removed during activation from the contact mass, that for the activation of a separate reactor is required or the reaction products of the activation, in particular trichlorosilane and

Tetrachlorosilane, undesirable by - products of

Methylchlorsilansynthese represent that by activation at least 1 to 2% of the raw material used silicon is consumed and that a relatively high

Activation temperature is needed.

Also DE 19817775A1 describes that fresh contact mass is not active enough. It should be activated with HCl, for example. There are further disadvantages of a separate pre-treatment of the fresh contact mass. Fresh contact mass must be heated to 370 ° C for a certain time. It leads to high operating costs and investments. Steam is usually the one

Heat source in industrial plants. 300 ° C can only be achieved with steam under extreme pressure, which is available in very few companies.

During the preforming, CuCl and silicon give rise to silanes, in particular chlorosilanes, which have to be removed and treated.

In US2389931 reactor cascades (fluidized bed reactors) are described in which strongly reacted contact material is separated from a reactor, cooled and introduced into a second reactor. This makes the use of silicon more effective, but the drastic reaction conditions produce much more methyltrichlorosilane. Even when cooled, the contact mass loses reactivity and selectivity.

The invention relates to a process for the preparation of ethylchlorosilanes by reacting with chloromethane

Contact mass, in which in a first fluidized bed reactor (fluidized bed reactor 1), a mixture containing silicon, copper catalyst and promoter (contact mass 1) is fed in the presence of chloromethane at 200 to 450 ° C active contact mass (contact mass 2) is formed,

a part of the contact mass 2, preferably via cyclones of

Fluidized bed reactor 1, preferably by means of reaction gas, preferably chloromethane, taken from the fluidized bed reactor 1 and in a second fluidized bed reactor (fluidized bed reactor 2) is fed and is reacted at 200 to 450 ° C with chloromethane, wherein per unit time in fluidized bed reactor 1 at least 20 parts by weight of contact mass 2 per 100

Parts by weight contact mass 1 are recycled and wherein the fed into the fluidized bed reactor 2 and in

Fluidized bed reactor 1 returned contact mass 2 after removal from the fluidized bed reactor 1 not one

Temperature of 150 ° C is cooled.

The contact mass 2 is compared to a fresh

Contact mass (contact mass 1) and to a preformed

Contact mass - which was activated under N _2, for example at about 300 ° C - much more active. The reaction of chloromethane with activated Si particles releases energy. It leads to local temperature increases up to several 100 ° C, in addition, the surface is freed from oxide layers and other passivating layers.

For the preparation of contact material 2 no separate device must be provided. It can be used the existing fluidized bed reactors.

The fluidized-bed reactors 1 and 2 can be operated with different parameters, such as pressure and temperature, and thereby be adapted to the differences in the contact masses 1 and 2 with different properties. Completely reacted contact material is preferably discharged via a cyclone arranged downstream of the fluidized-bed reactor 2.

In a particular embodiment, from the

Fluidized bed reactor 2 or from the fluidized bed reactors 1 and 2 with the gas stream discharged contact mass components (contact mass 3) completely or partially in the

Fluidized bed reactor 2 returned. Preferably, the Contact mass 3 with one or more cyclones separated from the gas stream.

Preferably, the fluidized bed reactor 1 is operated at a higher temperature than the fluidized bed reactor 2.

Preferably, the fluidized bed reactor 1 at 300 - 350 ° C and fluidized bed reactor 2 is operated at 250 - 300 ° C, wherein preferably the temperature in the fluidized bed reactor 1 is higher. This makes the fluidized bed reactor 1 more active and the fluidized bed reactor 2 more selective. This leads to an overall better performance of the fluidized bed reactors with higher selectivity with respect to dimethyldichlorosilane.

In a particular embodiment of the

2 further catalysts and / or promoters added to fluidized bed reactor 1 taken contact mass.

Preferably 1 to 80 wt .-%, particularly preferably 10 to 50 wt .-% of the fed into the fluidized bed reactor 1 contact mass 1 per unit time as contact mass 2 from the

Fluidized bed reactor 1 and taken in the

Fluidized bed reactor 2 fed.

In a particular embodiment, several,

in particular 2 to 5 fluidized bed reactors 1 are used.

In each case from 1 to 50% by weight, particularly preferably in each case from 5 to 20% by weight, of the fed-in contact material 1 as contact mass 2 is taken from these fluidized-bed reactors 1 and fed into the fluidized-bed reactor 2.

Preferably, 30 to 50 parts by weight of contact mass 2 per 100 parts by weight of contact mass 1 are recycled per unit time in fluidized bed reactor 1. In a particular embodiment, the contact mass 2 withdrawn from one or more fluidized-bed reactors 1 is collected in a collecting container and fed from the collecting container into one or more fluidized-bed reactors 2.

In a particular embodiment, several,

in particular 2 to 5 fluidized bed reactors 2 are used.

In a particular embodiment, the contact mass 2 is mixed with thermally conductive material before it in the

Fluidized bed reactor 2 is fed. This improves the heat transfer of the contact mass particles (hotspots) to a heat removal system, for example cold fingers.

Preferably, the thermally conductive material is selected from silicon, silicon carbide or silica having a

preferred grain size between 100-800 microns, more preferably 200-400 microns. Preferably, 100

Parts by weight of contact mass 2 with up to 40 parts by weight, in particular with up to 20 parts by weight of heat-conducting

Material mixed.

Preferably, the in the fluidized bed reactor 2

fed contact mass 2 after removal from the

Fluidized bed reactor 1 is not cooled below a temperature of 180 ° C, especially not lower than 200 ° C.

The contact mass 2 is preferably by means of reaction gas, preferably chloromethane, from the fluidized bed reactor. 1

taken. Preferably, the contact mass 2 and

optionally also the contact mass 3 in the

Fluidized bed reactor 2 fed in fluidized form with chloromethane. The silicon used in the process preferably contains not more than 5% by weight, more preferably not more than 2% by weight, in particular not more than 1% by weight, of other elements than

Impurities. The impurities which are at least 0.01% by weight are preferably elements selected from Fe, Ni, n, Al, Ca, Cu, Zn, Sn, C, V, Ti, Cr, B, P, O.

The particle size of the silicon is preferably at least 0.5 microns, more preferably at least 5 microns, especially at least 10 microns, and preferably

at most 650 microns, more preferably at most 580 microns, especially at most 500 microns.

The mean particle size distribution of the silicon is the d50 value and is preferably at least 180 microns, more preferably at least 200 microns, especially at least 230 microns and preferably at most 350 microns, more preferably at most 300 microns, especially at most 270 microns.

The copper for the catalyst can be selected from metallic copper, a copper alloy or a

Copper compound. The copper compound is preferred

selected from copper oxide and copper chloride, in particular CuO, CU2O and CuCl or a copper-phosphorus compound (CuP).

Alloy). Copper oxide may be, for example, copper in the form of copper oxide mixtures and in the form of copper (II) oxide.

Copper chloride can be used in the form of CuCl or in the form of CUCI2, and corresponding mixtures are also possible. In a preferred embodiment, the copper is used as CuCl.

Preferably, at least 100 parts by weight silicon

0.1 parts by weight, more preferably at least 1

Part by weight of copper catalyst and preferably at most 10 parts by weight, in particular at most 8 parts by weight Copper catalyst, each used based on metallic copper.

Preferably, the contact mass 1 contains a zinc promoter, which is preferably selected from zinc and zinc chloride.

At least 0.01 part by weight of zinc promoter, more preferably at least 0.1 part by weight of zinc promoter and preferably at most 1 part by weight, in particular at most 0.5 part by weight, are preferably added per 100 parts by weight of silicon

Zinc promoter, each used based on metallic zinc.

Preferably, the contact mass 1 contains a tin promoter, which is preferably selected from tin and tin chloride.

Preferably, for every 100 parts by weight of silicon, at least 0.001 part by weight of tin promoter is particularly preferred

at least 0.05 parts by weight of tin promoter and preferably at most 0.2 parts by weight, in particular at most 0.1

Parts by weight of tin promoter, each used based on metallic tin.

Preferably, the contact mass 1 contains a combination of zinc promoter and tin promoter and in particular additionally phosphorus promoter. Preferably, at least 30 wt .-%, in particular at least 50 wt .-% of the sum of copper catalyst and promoters

Chlorides of copper, zinc and tin.

In addition to the zinc and / or tin promoters, it is also possible to use further promoters which are preferably

are selected from the elements phosphorus, cesium, barium, manganese, iron and antimony and their compounds. The P promoter is preferably made of CuP alloys

selected.

The pressure during the reaction is preferably at least 1 bar, in particular at least 1.5 bar and preferably at most 5 bar, in particular at most 3 bar, in each case indicated as absolute pressure.

The produced methylchlorosilanes are in particular

Dimethyldichlorosilane, ethyltrichlorosilane, trimethylchlorosilane and H-silanes.

The process may be batchwise or preferred

be carried out continuously. Continuously means that reacted silicon and optionally with the

Reactive dust discharged catalysts and promoters are continuously replenished, preferably as premixed contact material 1 and contact material 2 and optionally

Contact compound 3. Preferably, chloromethane is in the

Fluidized bed reactors 1 and 2 used simultaneously as a reactant and fluidization medium.

In the following examples, unless otherwise indicated, all amounts and percentages are by weight, all pressures are 0.10 MPa (abs.) And all temperatures are 20 ° C.

Examples:

I) Investigation of the power of contact mass 2:

1. There were 50 g of contact mass 2 from an industrial

Fluidized bed reactor in a laboratory fluidized bed reactor with about 201 / h chloromethane reacted at 340 ° C, according to 7 Hours of reaction were 103 g of crude silane, with one

Dimethyldichlorosilane selectivity of 71% (73 g

Dimethyldichlorosilane).

There were added to 50 g of contact mass 2 from an industrial fluidized bed reactor 280 ppm P and reacted in a laboratory fluidized bed reactor with about 201 / h of chloromethane at 340 ° C. After 7 hours of reaction, 93 g of crude silane were obtained, with a dimethyldichlorosilane selectivity of 78% (73 g of dimethyldichlorosilane). However, adding P to contact mass 2 results in less activity

Increase the selectivity, so that in the end the same amount of dimethyldichlorosilane with significantly less

Nebensilanen be generated.

There were reacted 50 g of contact mass 2 from an industrial fluidized bed reactor in a laboratory fluidized bed reactor with about 201 / h of chloromethane at 320 ° C, after 7 hours of reaction, 86 g of crude silane, with a

Dimethylsichlorosilane selectivity of 74% (64 g

Dimethyldichlorosilane). The temperature reduction leads to less activity but better

Selectivity.

Examination of the power of 50% contact mass 2 + 50% contact mass 1:

25 g of contact mass 2 from an industrial fluidized-bed reactor with 25 g of contact mass 1 were reacted in a laboratory fluidized-bed reactor with approx. 201 / h of chloromethane at 340 ° C. After 7 hours of reaction, 33 g of crude silane, with a dimethyldichlorosilane selectivity of 76% (25 g of dimethyldichlorosilane) were obtained. The addition of contact mass 1 leads to significantly less activity.

Claims

Patent claims

1. Process for the production of methylchlorosilanes

Implementation of chloromethane with contact mass,

in which in a first fluidized bed reactor

(Fluidized bed reactor 1) a mixture containing silicon, copper catalyst and promoter (contact mass 1) is fed in, active contact mass (contact mass 2) is formed in the presence of chloromethane at 200 to 450 ° C, part of the contact mass 2 is removed from the fluidized bed reactor 1 and into a second fluidized bed reactor

(Fluidized bed reactor 2) is fed in and is reacted with chloromethane at 200 to 450 ° C, with at least 20 parts by weight of contact mass 2 per 100 parts by weight of contact mass 1 being recycled per unit of time in the fluidized bed reactor 1 and whereby the in the

Fluidized bed reactor 2 fed and in

Fluidized bed reactor 1 returned contact mass 2 after removal from the fluidized bed reactor 1 is not cooled below a temperature of 150 ° C.

Method according to claim 1, in which the from the

Fluidized bed reactor 2 or discharged from the fluidized bed reactors 1 and 2 with the gas stream

Contact mass components (contact mass 3) are completely or partially returned to the fluidized bed reactor 2.

3. Method according to one or more of the preceding

Claims, in which the fluidized bed reactor 1 is operated at a higher temperature than the fluidized bed reactor 2. Method according to one or more of the preceding claims, in which several fluidized bed reactors 1 are used.

Method according to one or more of the preceding claims, in which several fluidized bed reactors 2 are used.

Method according to one or more of the preceding claims, in which the silicon used in the method contains at most 2% by weight of elements other than impurities.

Method according to one or more of the preceding claims, in which the contact mass contains a zinc promoter.

Method according to one or more of the preceding claims, in which the contact mass contains a tin promoter.

Method according to one or more of the preceding claims, in which the copper catalyst is selected from copper oxide and copper chloride and a copper-phosphorus compound.