DE4412837A1 - Prodn. of methyl-chloro-silane esp. di:methyl-di:chloro-silane - Google Patents

Abstract

The prodn. of methylchlorosilanes (I) comprises reacting chloromethane with Si in the presence of Cu, Zn and V together with Sn, Sb or P.

Description

The invention relates to a method for producing Me thylchlorosilanes by reacting chloromethane with sili cium in the presence of copper, zinc and vanadium and one Metal that is selected from tin, antimony and phosphorus.

In the production of methylchlorosilanes from silicon and Chloromethane according to the Rochow method in the presence of a Copper catalyst and optionally promoter substances (Direct synthesis process) a mixture of methyl chlorine is formed silanes and in a smaller amount of other by-products. At for example, in US Re. 33,452 a direct synthesis process with a catalyst combination of the elements or Compounds of copper, zinc and tin are described.

The raw material silicon is used in electrically heated furnaces by reducing silicon dioxide with reducing agents, such as coal, petroleum coke and wood chips. By ver Silicon always contains impurities in the materials used Foreign elements. Some of these are foreign elements, such as aluminum minium, iron, calcium desirable. Their concentration will then targeted. Some of these are foreign elements such as titanium, lead, chrome and nickel are undesirable. Their Concentration is then kept low.  

In H.M. Rong, Silicon for the Direct Process to Methylchlo rosilanes, Ph. D. Thesis, The Technical University of Nor way, Trondheim, 1992 is vanadium as a foreign element in Sili cium described in a concentration up to 500 ppm. Lubose vich et al., Journal Applied Chemistry USSR, 49 (1976) 2158- 2168, describes vanadium in intermetallic phases complex nature in silicon, which from the elements iron, titanium, silicon, manganese, vanadium and phosphorus consist. This intermetallic phase is inert, thus vanadium should have no effect on direct syn run out of thesis process. A. Tuset, H.M. Rong and A.G. Forwald in proc. Conf. Silicon for Chemical Industry, 1992, 11-23, describe that vanadium is in an intermetallic phase consisting of iron, silicon, titanium, aluminum, manganese and Vanadium is present and that this phase with chloromethane under the conditions of direct synthesis does not respond.

In the direct synthesis process there is a high selectivity of dime thyldichlorosilane aimed. The selectivity is exerted expresses as a proportion of the dimethyldichlorosilane in the mass of Methylchlorosilanes.

The object of the invention was to provide a method for producing of methylchlorosilanes by reacting chloromethane with Provide silicon, with this method a should have high selectivity of dimethyldichlorosilane.

The invention relates to a method for producing Me thylchlorosilanes by reacting chloromethane with sili cium in the presence of copper, zinc and vanadium and one Component that is selected from tin, antimony and phos phor.  

Copper, zinc, tin, antimony, phosphorus and vanadium can be found in elementary form or in the form of their compounds become. The above elements or compounds can can be mixed with the silicon, they can also last be part of the silicon.

In the method according to the invention, 10 to 500 ppm, preferably 100 to 400 ppm and in particular 200 up to 300 ppm vanadium, each based on the weight of Si used licium.

In the process according to the invention, 0.5 to 10% by weight, in particular 0.7 to 7% by weight, of copper, based on silicon used, 1 are particularly preferred up to 5% by weight.

In the process according to the invention, preferably total 30 to 3000 ppm by weight, in particular 100 to 2000 ppm by weight Tin, antimony and phosphorus, based on copper. There can only be one item that is selected from tin, anti mon and phosphorus or their compounds, it can also two or all three elements or connections are used become.

In the method according to the invention, one is preferred Embodiment silicon with a grain size of less than 700 µm and larger than 20 µm, particularly preferably in a grain size smaller than 250 µm and larger than 70 µm.

The silicon used and the elements copper, zinc, Tin, antimony, phosphorus and vanadium and their compounds can also be foreign elements such as alkali metals, Alkaline earth metals, aluminum, iron, titanium, lead, chrome and Contain nickel. Their presence can be desirable or un  be desired. For example, the silicon can be 0.1 to 0.25% by weight aluminum, 0.01 to 0.1% by weight calcium and 0.15 contain up to 0.4 wt .-% iron. The concentration of the un desired foreign elements are kept as low as possible. In the direct synthesis process there is also a high space-time lei of the reactors aimed at by the activity of the Reaction mixture consisting of silicon, copper catalyst and promoters depends. A meaningful size for that Specification of the space-time performance in relation to methylchlorosila ne is the product related to the surface of the silicon tion rate PR2

The reference to the surface is made because the Re actions take place on the surface of the silicon.

High production rates of methylchlorosilanes in addition to high selectivity of dimethyldichlorosilane are achieved, if the silicon used contains vanadium as a constituent holds.

The vanadium can be used in the reduction of silicon dioxide Reducing agents come from raw materials containing vanadium or have been alloyed with the silicon.

The process is preferably carried out in a fluidized bed reactor, preferably in the temperature range from 250 to 400 ° C, esp performed especially at 250 to 360 ° C. Because this is the ge requires the least effort, the procedure is usually at Pressure of the surrounding atmosphere (i.e. around 0.1 MPa) to 0.5 MPa, but higher pressures can also be applied be turned.  

The process can be done with pure methyl chloride or methyl chloro rid / inert gas mixtures are carried out as an inert gas For example, nitrogen or argon can be used the. The amount of gas flow is preferred in the leadership form chosen so that a fluidized bed in the reactor is formed.

Methyl chloride or methyl chloride / inert gas mixtures in a preferred embodiment of the invention Process continuously passed through the contact mass, which creates a fluidized bed. Not implemented Methyl chloride and optionally inert gas and the formed gaseous methylchlorosilanes leave the reactor.

The process can be continuous or discontinuous be performed. Continuous means that the quantities on reacted silicon and with the reaction dust gene catalysts are continuously replenished.

Continuous operation of a reactor falls short selectivity of the direct synthesis process related to dimethyldichlorosilane. Therefore must the production is stopped after a certain time.

The selectivity of the direct synthesis process can be longer be maintained in the future when vanadium is added to the Time at which the selectivity drops, the reaction gene is metered in. The selective can be particularly effective be maintained when the reaction mixture before adding very little, for example below 50 ppm by weight Contains vanadium, based on silicon. Preferably be the reaction mixture 10 to 500 ppm, preferably 100 to 400 ppm and especially 200 to 300 ppm vanadium, each based on the weight of silicon metered.  

In the examples below, if not each otherwise stated

• a) all quantities based on weight;
• b) all pressures 0.10 MPa (abs.);
• c) all temperatures 20 ° C

Examples example 1

Influence of vanadium content in standard silicon low in calcium. In the silicon was alloyed with vanadium. Then it froze Silicon slowly.

In a laboratory fluidized bed reactor (diameter 25 mm) with Heating winding, gas distribution frit, distillation bridge with Brine cooling and plunger were 120 g silicon grit with different vanadium content of the grain size 70-240 µm known specific surface mixed with 6 g Copper (II) oxide, 1 g zinc oxide and 1300 ppm tin based on Copper (II) oxide heated to 340 ° C under 40 l / h nitrogen. Then 40 l / h of chloromethane were introduced and up 395 ° C heated. After the start of the formation of methylchlorosi The temperature was reduced to 360 ° C and 50 ml of Me thylchlorosilane caught. Then another 30 ml of methylchlorosilanes collected. The time for education 30 ml of methylchlorosilane is used as the production phase records, the production rate PR2  is calculated according to the above formula. The content of dime thyldichlorosilane (M2) in the 30 ml of methylchlorosilanes the production phase was by means of GC analysis in weight percent determined.

Table 1

Examples 1a-1e

The direct synthesis proceeds with high selectivity and acti vity.

Example 2

Influence of vanadium content in water-granulated silicon calcium rich. Vanadium was alloyed into the silicon. After that the liquid silicon became granular by pouring it into water liert.

Analogously to Example 1, various water-granulated Si Licium types tested with different vanadium contents.

The direct synthesis proceeds with high selectivity and acti vity.

Example 3 Influence of adding vanadium

Analogously to Example 1, silicon with 0.2% aluminum, 0.026% calcium and 10 ppm vanadium tested, the Reak tion mixture different amounts of vanadium added were.

The reaction proceeds with high selectivity. The activity the reaction mixture is significantly lower than in the case of the play 1 and 2.

Example 4 Influence of vanadium addition in a continuous experiment

In a fluidized bed reactor (diameter 100 mm) with auto dosing of the reaction mixture, pressure control, Temperature control, condensation of the methylchlorosilanes in Product reservoir and pressure difference measurement as a measure of the fluidized bed height was 6000 g of a mixture of 5880 g silicon with 0.21% aluminum, 0.2% calcium and 10 ppm Va nadium, 90 g copper (II) oxide doped with 1300 ppm tin and 30 g of zinc oxide and placed at 1.5 bar pressure at 290 ° C. heats. The experiment was conducted so that Reak consumed tion mass, regulated by the drop in the pressure difference in the Reactor, was continuously re-introduced, thus the Reactor filling remained constant. A discharge of feast was deliberately avoided in order to increase the effects of To make impurities clear. So was one Trial run (L2 without vanadium added for comparison) over 98 h, the methylchlosi formed was formed every 4 h lane on the content of dimethyldichlorosilane using GC-Ana lysis examined. In this trial run, averages were Lich formed 0.64 kg / h methylchlorosilanes. Another ver search run (L1 with vanadium addition) was analogous to the first carried out, with a reaction mi from operating hour 60 with 360 ppm added vanadium with a grain size of 40 µm was re-launched. Here an average of 0.62 kg / h of methylchlorosilanes. The course of the salary Dimethyldichlorosilane (M2) in the crude product of the two experiments The table below shows the duration of the experiment.

A satisfactory selectivity in the test run L1 is about maintain the 60th hour of operation and increase even up to the 90th hour of operation.

Example 5 Comparative example; Influence of vanadium addition without tin addition

Example 5 was analogous to Example 1 with the omission of Tin doping of the copper (II) oxide was carried out.

Claims (4)

1. Process for the preparation of methylchlorosilanes by Reaction of chloromethane with silicon in the presence of Copper, zinc and vanadium and a component that is selected from tin, antimony and phosphorus. 2. The method of claim 1, wherein 10 to 500 ppm Vanadi um, based on the weight of silicon used the. 3. The method according to claim 1 or 2, wherein the used Contains silicon vanadium as an ingredient. 4. The method of claim 1, 2 or 3, wherein vanadium the time when the selectivity with respect to Di methyldichlorosilane drops, zudo the reaction mixture is settled.