GB2153697A - Catalysts for the production of organohalosilanes - Google Patents

Abstract

There is provided a method for making organohalosilanes comprising effecting reaction between an organohalogen compound and powdered silicon in the presence of an effective amount of catalyst comprising (a) a mixture of Cu DEG , Cu2O and CuO, (b) from about 200 to about 5000 ppm tin or tin-containing compound as tin relative to copper and (c) from about 50 to about 5000 ppm aluminum or aluminum-containing compound as aluminum relative to copper. r

Description

SPECIFICATION Catalyst composition and process for using Background of the invention The present invention relates to a catalyst composition for effecting reaction between powdered silicon metal and organohalogen compounds to produce organohalogen silanes. More particularly, the present invention relates to a copper catalyst composition containing critical amounts of tin, aluminum, iron and lead and a process involving the reaction of an organohalide, preferably an alkylhalide such as methyl chloride, with powdered silicon metal in the presence of such catalyst to yield organohalogensilanes, particularly methylchlorosilanes.

It was well known prior to the present invention that alkylhalosilanes could be prepared by the direct reaction of organic chlorides with elemental silicon in the presence of a copper catalyst, for example, as taught by Rochow in U.S. Pat. No. 2,380,995. In practice, this reaction is usually carried out in a stirred bed reactor of the type described in U.S. Pat. No. 2,449,821 to Sellers et al., in a fluidized bed reactor of the type described in U.S. Pat. No. 2,389,931 to Reed et al., or in a rotary kiln. Generally the reaction is carried out by passing the organic halide in vaporous form over the surface of the powdered silicon metal while maintaining the reaction mixture at an elevated temperature.Typically the elemental silicon is mixed with finely divided copper powder as described in the aforementioned Rochow patent, the copper serving as a catalyst for the reaction between the organic halide and the silicon.

In the production of organohalosilanes by the Rochow direct process the two primary reaction products are organotrihalosilane (T) and diorganodihalosilane (D). It is preferred that the diorganodihalosilane be produced in as great a quantity as possible since it can be further reacted to produce polydiorganosiloxane polymers useful for manufacturing room temperature vulcanizable rubber compositions and heat curable rubber compositions. Unfortunately the reaction between the organic halide and elemental silicon utilizing the Rochow direct process produces an excess of organotrihalosilane and an insufficient amount of diorganodihalosilane. Additionally other by-products such as polysilane residue and hydrogen containing monomeric silanes are also generated.Accordingly catalysts and processes are continually sought which maximize diorganodihalosilane production and minimize organotrihalosilane and other by-products produced in the Rochow direct process reaction.

Rochow et al. in U.S. Pat. No. 2,383,818 disclosed that utilization of copper oxides rather than elemental copper increases the reactivity of the reaction mass so as to provide larger yields of diorganodihalosilane. It should be noted, however, that the ratio of organotrihalosilane to diorganodihalosilane is not necessarily decreased by employing a copper oxide catalyst in place of a copper catalyst.

A further improvement in the rate of production of diorganodihalosilanes was achieved when zinc was used in combination with the copper catalyst as shown in U.S. Pat. No. 2,464,033 to Gilliam. While such zinc promoter provides only a small increase in the reaction rate, a significant increase in the amount of diorganodihalosilane is obtained due to the improved selectivity of the reaction.

Rossmy, U.S. Pat. No. 3,069,452, discloses a new type of copper catalyst for improving the yield of diorganodihalosilane in the direct process. Generally the catalyst of Rossmy is a brittle, easily grindable silicon-copper alloy wherein the silicon content can vary within the range of 1 to 50% by weight. The efficiency ofthe catalyst is improved by employing accelerators such as aluminum or zinc.

Petrov et al. reported in "Synthesis of Organosilicon Monomers", authorized translation from the Russian by C. N. Turton and T. I. turton, Consultants Bureau (1964), that while copper has been found to be the best catalyst, the direct process is also accelerated by adding silver, aluminum, zinc, nickel, cobalt, iron and other metals more electropositive than silicon to the silicon or to the silicon-copper mixture. However, according to Petrov et al. these elements generally are not of independent value and only improve the properties of the silicon-copper mixture to some extent. Petrov et al. also teach that traces of metals have a great effect on the activity of contact mixtures, for example, traces of such metals as lead, tin and bismuth, even in extremely small amounts (0.01 to 0.005%) sharply reduce the activity of silicon-copper alloys.

Bazant, in "Direct Synthesis of Organohalogensilanes", Institute of Chemical Process Fundamentals, Czechoslovak Academy of Sciences, Prague, Czechoslovakia (1965), determined that in the direct process elementary copper acts as a catalyst in the same sense as in other catalytic reactions. Furthermore Bazant discloses that the form in which copper is introduced to the contact mass is of no important consequence and that if admixtures to the contact mass recommended as promoters influence the process, then they decrease the conversion to dimethyldichlorosilane. The most effective admixture is aluminum, a small amount of which (up to 1%) increases the overall reaction rate. Bazant also reports that small admixtures of impurities incorporated into the lattice of silicon seem to have the decisive influence on the activity of the contact mass.

Eaborn and Bott in an article entitled "Synthesis and Reactions of the Silicon-Carbon Bond" provide a summary of prior art teaching and point out the conflicting results of many researchers. The authors also report that most proposed modifications to the original direct process conditions involve changes to the catalyst. These modifications include changes in the method of preparing the silicon-copper contact mass, the addition of promoters to the catalyst and the use of metals other than copper as catalyst or no catalyst at all. Variations in the method of preparing the contact mass or in the amount of trace impurities (which are often not determined or not stated) in the copper or silicon can also have pronounced effects on the rate and selectivity of the reaction. Because of this, Eaborn and Bott concluded that results are often difficult to reproduce even by the same workers.Another difficulty noted was that the effect of a promoter varies considerably with the method of preparation of the contact mass and with the nature of impurities present.

Moreover, copper-silicon alloys and copper-silicon mixtures are often affected differently.

Maas et al., U.S. Pat. No. 4,218,387, is an excellent example of Eaborn and Bott's conclusion that variations in the method of preparing the catalyst has a pronounced effect on reactivity and selectivity. Maas et al.

found that enhanced catalytic reactivity resulted when the oxidation of elemental copper to cuprous oxide is carried out with oxygen at a reduced partial pressure compared with that of air.

Radosavlyevich et al. found that micro quantities of silver added to contact masses resulting from the reaction of powdered silicon and methyl chloride in the pesence of cuprous chloride decreased the yield of methylchlorosilanes, while tin and calcium chloride increased the rate of formation of methylchlorosilanes as reported in "Influence of Some Admixtures on the Activity of Contact Masses for Direct Synthesis of Methyichlorosilanes", Institute of Inorganic Chemistry, Belgrade, Yugoslavia (1965).

R. Voorhoeve, "Organohalosilanes- Precursors to Silicones", Elsevier Publishing Company, Amsterdam, Netherlands, points out that results of experiments employing the direct process are rarely in agreement and are of poor reproducibility. Voorhoeve states that the cause of the failures remains an enigma but it is probably connected with one of the greatest problems in the direct synthesis, namely the effect of impurities.

Although the relevant investigations have not been sparse they have been almost entirely confined to silicon and copper present in an inaccurately defined state. Among the findings of Voorhoeve is that the presence of iron, even in a fairly large amount (up to 5%) in a silicon-copper contact mixture seems to have only a small effect on the reaction with methyl chloride. Voorhoeve also reports that the effect of tin is uncertain; while it was reported to have no effect, later work showed the presence of antimony in the alloys used and hence the results were inconclusive. Voorhoeve further notes with repect to selectivity that iron has a detrimental effect, though often only to a small, imperceptible extent.

Believing that such unpredictable results were due to impurities contained in the precipitated, natural copper catalysts normally employed in the direct process (i.e. copper derived from leachate recovery processes), the present applicants set out to provide a synthetic copper catalyst composition which avoided the prior art shortcomings. It was first determined that the copper employed shou Id be electrolytic grade copper so as to minimize the possibility of impurities adversely affecting the reaction of organic halide with elemental silicon. Impurities would thereafter be added in various combinations to determine the optimum matrix for providing maximum reactivity and selectivity.It should be noted that selectivity is the ratio of organotrihalosilane to diorganodihalosilane (T/D) as well as minimization of other by-products to maximize the yield of diorganodihalosilane, such that the lower the ratio the more selective the process. Also, the reactivity or inherent reaction rate, as indicated by the rate constant is defined as the number of grams of silane produced per number of grams of silicon metal introduced into the reaction mixture per hour. A more detailed discussion of the foregoing T/D ratio and Kp values can be found in the copending patent application of Ward et al., Serial No. 518,236filed filed July28, 1983.

In addition to providing a catalyst composition having suitable reactivity and selectivity, the present applicants set out to minimize the high boiling residue content of the crude organohalosilane product stream. Residue can be defined as products in the methylchlorosilane crude having a boiling point greater than 70"C at atmospheric pressure. Residue consists of such materials as disilanes, disiloxanes, disilmethylenes and other higher boiling species such as trisilanes and trisiloxanes. The amount of residue remaining in prior art process typically was about 10% by weight Minimization of residue not only enhances direct process monomeric yields but also reduces subsequent processing requirements to generate additional organohalosilanes from the disilanes.

In a similar attempt to avoid the shortcomings of prior art catalysts prepared from copper mine leachate and processes for making organohalosilanes, Ward et al. in copending patent application serial number 518,236, filed July 28, 1983, found that contact masses containing silicon, copper catalyst, and a combination of tin and zinc promoters provided Kp values about twice thatfortin promoted or zinc promoted systems while simultaneously improving the selectivity over zinc or tin promoted contact masses. Furthermore, the residue of the crude product was reduced from about 10 weight percent to as low as one or two weight percent.

Summary of the invention It is an object of the present invention to provide a copper catalyst from electrolytic grade copper useful for catalyzing the reaction between elemental silicon and organohalogen compounds.

It is another object of the present invention to provide a copper catalyst containing critical amounts of specified components or impurities so as to provide a suitable reaction rate and suitable selectivity while minimizing the residue resulting from the reaction between elemental silicon and organohalogen compounds.

A further object of the present invention is to provide a process for producing organochlorosilanes from elemental silicon and organohalogen compounds such as methyl chloride.

In acordance with the foregoing objects and other objects which will be apparent from the following detailed description of the invention, there is provided by the present invention a copper catalyst composition consisting essentially of: (a) a mixture of Cu", Cu2O and CuO, (b) from about 200 to about 5000 ppm tin, relative to copper and (c) from about 50 to about 5000 ppm aluminum relative to copper.

In another aspect of the present invention there is provided a method for making organohalosilanes which comprises effecting reaction between an organohalogen compound such as methyl chloride and powdered silicon metal in a reactor in the presence of an effective amount of catalyst composition consisting essentially of: (a) a mixture of Cu", Cu2O and CuO, (b) from about 200 to about 5000 ppm tin, relative to copper and (c) from about 50 to about 5000 ppm aluminum relative to copper.

In addition to the tin and aluminum promoters, the copper catalyst of the present invention can include iron and zinc, but it must be substantially free of lead which acts as a poison.

It is particularly preferred to practice the method of the present invention in a fluidized bed reactor in a continuous manner where silicon-containing material having catalyst values is elutriated from the reactor and can by recycled. This method serves to maximize yield based on silicon material inputs.

Methyl chloride or an inert gas such as argon, or mixtures thereof, can be used to fluidize the bed of silicon particles in the reactor with or without catalyst values. The silicon present in the fluidized bed can have a particle size below 700 microns, with an average size of greater than 20 microns and les than 300 microns.

The mean diameter of the silicon particles is preferably in the range of 100 to 150 microns.

Description ofthe invention In one aspect of the present invention there is provided a copper catalyst composition consisting essentially of: (a) a mixture of Cu", Cu2O and CuO, (b) from aout 200 to about 5000 ppm tin ortin-containing compound as tin relative to copper, and (c) from about 50 to about 5000 ppm aluminum or aluminum-containing compound as aluminum relative to copper.

Such copper catalyst composition can further include up to about 7500 ppm iron or iron-containing compound as iron relative to copper and from about 0.01 to 0.5 part of zinc per part of copper. It is important that the catalyst composition be substantially free of lead which acts as a poison. By substantially free of lead is meant as small an amount as possible but not to exceed 2000 ppm lead relative to copper.

In another aspect of the present invention there is provided a method for making methylchlorosilanes comprising effecting reaction between an organohalogen compound, preferably an alkyl halide and most preferably methyl chloride, and powdered elemental silicon metal in a reactor in the presence of an effective amount of the aforementioned copper catalyst composition.

The copper is in the form of a mixture of free or elemental copper, cuprous oxide and cupric oxide and comprises from about 0.1 to about 10 percent by weight of the contact mass. More preferably such copper mixture comprises from about 0.5 to about 5.0 weight percent of the contact mass. Typically the elemental copper makes up from about 5 to about 20 percent by weight of the copper mixture, the cuprous oxide makes up from about 25 to about 60 percent by weight of the copper mixture, and the cupric oxide makes up from about 25 to about 50 percent by weight of the copper mixture. More preferably the elemental copper ranges from about 14 to about 18 weight percent, the cuprous oxide ranges from about 39 to about 50 weight percent and the cupric oxide ranges from about 35 to about 43 weight percent.

Ideally the elemental copper, cuprous oxide and cupric oxide mixture is prepared from an electrolytic grade scrap so as to minimize the likelihood of impurities being present which could adversely affect reactivity or selectivity in the process. Briefly, in the case of recovery processes such partially oxidized copper can be prepared by passing a solution of copper compound over scrap iron which results in the deposition of metallic copper in the form of a fine precipitate. The precipitate is then subjected to a pyrometallurgical process which results in oxidation of the copper. Other methods for preparing the copper mixture of the present invention are well known to those skilled in the art, for example, as described in U.S.

Pat. No.4,218,387 to Maas et al. which is incorporated herein by reference.

One example of a preferred partially oxidized copper which can be used as the source of copper to make the catalyst of the present invention can be characterized approximately as follows: Component Weight% Cu" 7-10% Cu2O 50- 52% CuO 37 - 40% Sn 200 ppm relative to copper Al 20 ppm relative to copper Fe 400 ppm relative to copper Pb 20 ppm relative to copper Insolubles approximately 0.05% The amount of tin present in the catalyst of the present invention can range from about 200 ppm to about 5000 ppm relative to copper. Although it is preferable that the tin be added as elemental tin of at least 99% purity, for example as minus 325 ASTM mesh tin metal dust, it may be added in the form of a tin halide, tin oxide, alkylated tin such as tetramethyl tin and alkyl tin halides.Other suitable tin sources can be determined without undue experimentation. Most preferably, thetin metal ortin-containing compound is present in the range of from about 300 to about 1800 ppm as tin metal relative to copper.

Aluminum or aluminum-containing compound is present in the range of from about 50 to about 5000 ppm as aluminum. Preferably the aluminum is added as elemental aluminum or as aluminum oxide (Al203), however, other suitable aluminum compounds can be determined without undue experimentation. In a more preferred embodiment the aluminum or aluminum-containing compound is added in an amount ranging from about 100 to about 2000 ppm as aluminum relative to copper.

Iron or iron-containing compounds may optionally be added in an amount ranging from trace amounts up to 7500 ppm relative to copper.

Furthermore, zinc or zinc-containing compounds can be incorporated in the catalyst of the present invention according to the teaching of the copending patent application of Ward et al., serial no. 518,236, filed July 1983. This patent application is incorporated by reference into the instant disclosure.

In practicing the process of the present invention the catalyst of the present invention is introduced into the reaction mixture at a rate sufficient to maintain in the reactor a catalyst having an average composition of 0.5 to 10% by weight copper relative to silicon, 200 to 5000 ppm tin relative to copper, 50 to 5000 ppm aluminum relative to copper, and, optionally, a trace to 7500 ppm iron relative to copper and 0.01 part to 0.5 part zinc per part of copper.

The silicon employed in the process of the present invention is usually obtained at a purity of at least 98% by weight silicon, and it is then comminuted to particles of silicon of less than 700 microns, with an average size greater than 20 microns and less than 300 microns. The mean diameter of the silicon particles is preferably in the range of 100 to 150 microns. The comminuted silicon particles are then fed into the appropriate reactor as needed. Although a fluidized bed reactor is preferred, the process of the present invention can be utilized in other types of reactors, such as fixed bed and stirred bed. A fluidized bed reactor is preferably utilized since optimum selectivity and the maximum amount of chlorosilane, particularly diorganodichiorosilane, is obtained.The process of the present invention can be carried out at a temperature in the range of 250 - 350"C and more preferably at a temperature in the range of 260 - 330us. Reaction can occur under continuous conditions or as a batch reaction. If desired a contact mass of powdered silicon with copper-tin-aluminum catalyst can be made prior to contact with methyl chloride to facilitate the generation of methylchlorosilanes.

It is advisable to carry out the process of the present invention under a pressure of 1-10 atmospheres in instances where a fluid bed reactor is used since higher pressure increases the rate of conversion of methyl chloride to methylchlorosilanes.

Methyl chloride gas can be continuously passed through the reactor to fluidize the reaction mass, and there can be passed out of the reactor gaseous methylchlorosilanes as well as the unreacted methyl chloride.

The gaseous crude product mixture and entrained reaction particulates are passed out of the fluidized bed reactor and passed through one or more cyclones so as to separate the larger particles of materials from the product gas stream. These particles having catalyst values can be returned to the reactorforfurther utilization in the process so as to maximize the yield of dimethyldichlorosilane from the silicon. Smaller particles are passed out with the product stream and the stream is subsequently clarified and condensed.

Purified methyl chloride is heated and recycled through the fluidized bed reactor for the further production of methylchlorosilanes. The crude methylchlorosilane stream is passed to a distillation train so as to distill in essentially pure form various chlorosilane fractions produced by the process. It is necessary to distill and purify the thus produced dimethyldichlorosilane and other chlorosilanes so that they can be utilized in the manufacture of silicone materials such as room temperature vulcanizable compositions and heat curable silicone rubber. Those skilled in the art are familiar with the processes for making organochlorosilanes from elemental silicon and for making silicon compositions from such organochlorosilanes.

In order that those skilled in the art will be better able to practice the invention, the following examples are given by way of illustration and not by way of limitation. All parts are by weight unless otherwise noted.

EXAMPLES Example 1 A mechanical mixture of 50 parts chemical grade silicon powder having a BET specific surface area of 0.5 m21gm having the following nominal composition: Component ppmw Aluminum 2800 Calcium 500 Iron 5000 Titanium 400 (the balance being predominantly silicon), 2.9 parts of a precipitate based copper oxide material having the following composition: Component Weight% Cu2O 40.6 CuO 41.4 Free Cu 14.5 Fe 0.69 Pb 0.11 Sn 0.42 Al 0.24 Si 0.95 (approximately 1 weight percent being considered acid insolubles in this free flowing powder having a median particle size of approximately 5 microns and a BET specific surface area of about 3m21gm), and 0.25 parts of finely divided zinc powder was formed.The mixture was then charged to a 1 inch internal diameter stainless steel stirred bed reactor controlled at 300"C through which was flowing an equimolar mixture of methyl chloride and dimethyldichlorosilane vapor such that the total throughput was 0.25 mole per hour.

After one hour the feed was switched to methyl chloride gas exclusively at a molar rate comparable to the binary feed which served for contact mass activation. Methylchiorosilane generation was immediately observed and a maximum Kp of approximately 45 glhr g Si was measured.Product composition was monitored by gas chromatography with the following achieved through 43% silicon utilization (based on initial batch silicon charge): Component Weight % (CH3)2Si Cl2, D 77.68 CH3Si Cl3, T 7.94 (CH3)3Si Cl, M 3.08 CH3Si HCl , MH 0.21 (CH3)2Si HCI, M2H 0.08 Residue 10.66 CrudeTiD 0.102 Example 2 A second mechanical mixture was prepared using 50 parts powdered silicon metal as in Example 1, and 2.9 parts of a mixed copper oxide catalyst based on electrolytic copper having the following composition:: Component Weight% Cu2O 56.7 Cu 0 34.9 Free Cu 7.3 Fe 0.024 Pb 0.027 Sn 0.140 Al 0.0125 Si Trace (only a trace of the material is considered as acid insolubles in this free flowing powder having a median particle size of approximately 4 microns and a BET specific surface area of about 2 m2/gm) and 0.25 parts zinc as in Example 1.

The tin and aluminum were intentionally added to the relatively clean copper approximately intermediate in the manufacturing process but prior to oxidative roasting.

The direct process reaction to form methylchlorosilanes was carried out in an identical manner to that of Example 1. A maximum Kp of about 38g/hr g Si was measured. Product composition for approximately 45% silicon utilization (based on initial silicon batch charge) was as follows: Component Weight% (CH3)2 SiC12, D 78.80 CH3 SiCI3, T 7.20 (CH3)3 SiCI , M 2.96 CH3SiHCl2,MH 0.37 (CH3)2 Si HCl, M2H 0.07 Residue 10.04 CrudeTiD 0.091 Thus a synthetic catalyst system was devised wherein comparable or superior performance to a natural, precipitate-based copper oxide system was demonstrated..

Example 3 Athird mechanical mixture was prepared using 50 parts powdered silicon metal as in Examples 1 and 2 and 2.9 parts of a mixed copper oxide catalyst based on electrolytic copper having incorporated in the initial copper melt the following trace metals: Component Weight % Fe 0.66 Sn 0.10 Al 0.21 Cu2O, CuO and free copper distribution and physicals (e.g. BET, specific surface area, and median particle size) approximated those of the catalysts of Examples 1 and 2. As in Examples 1 and 2,0.25 part zinc powder was also incorporated in the contact mass mechanical mixture.

The direct process reaction to form methylchlorosilanes was carried out in a manner identical to that of Examples 1 and 2. A maximum Kp of approximately 23g/hr g Si was measured as was the following product composition for about 28 percent silicon utilization (based on initial batch silicon charge): Component Weight% (CH3)2 SiCI2, D 80.97 CH3 Sic3, T 8.22 (CH3)3SiCl,M 2.19 CH3SiHCl2,MH 1.26 (CH3)2 Si HCI, M2H 0.25 residue 6.9 CrudeT/D 0.102 Thus an enhancement of the net desired component resuted from a synthetic formulation incorporating Sn, Al and Fe in a contact mass utiizing Zn such that Cu/Zn and other trace metal ratios were held in specified ranges.

Claims (24)

1. A method for making organohalosilanes comprising effecting reaction between an organohalogen compound and powdered silicon in the presence of an effective amount of catalyst consisting essentially of (a) a mixture of Cu , Cu2O and CuO, (b) from about 200 to about 5000 ppm tin or tin-containing compound as tin relative to copper and (c) from about 50 to about 5000 ppm aluminum or aluminum-containing compound as aluminum relative to copper.

2. The method of Claim 1 wherein the catalyst further consists essentially of up to about 7500 ppm iron or iron-containiny compound as iron relative to copper.

3. The method of Claim 1 wherein the catalyst further consists essentially of from about 0.01 to about 0.5 part zinc or zinc-containing compound as zinc per part copper.

4. The method of Claim 2 wherein the catalyst further consists essentially of from about 0.01 to about 0.5 part zinc or zinc-containing compound as zinc per part copper.

5. The method of Claim 1 wherein the catalyst is substantially free of lead.

6. The method of Claim 1 wherein the catalyst comprises from about 0.1 to about 10 percent by weight of the contact mass.

7. The method of Claim 1 wherein the catalyst comprises from about 0.5 to about 5.0 weight percent of the contact mass.

8. The method of claim 1 wherein the elemental copper makes up from about 5 to about 20 weight percent of the catalyst, the cuprous oxide makes up from about 25 to about 60 weight percent of the catalyst and the cupric oxide makes up from about 25 to about 50 weight percent of the catalyst.

9. The method of Claim 1 wherein the elemental copper makes up from about 14 to about 18 weight percent of the catalyst, the cuprous oxide makes up from about 39 to about 50 weight percent of the catalyst and the cupric oxide makes up from about 35 to about 43 weight percent of the catalyst.

10. The method of claim 1 wherein the partially oxidized copper of the catalyst is prepared from electrolytic grade scrap of essentially high purity.

11. The method of Claim 10 wherein the partially oxidized copper is prepared by passing a solution of copper compound over scrap iron to form a fine precipitate and partially oxidizing the copper in said precipitate by a pyrometallurgical process.

12. The method of Claim 1 wherein the organohalogen compound is methyl chloride.

13. The method of Claim 1 which is practiced under continuous conditions in a fluid bed reactor.

14. The method of Claim 1 which is practiced in a stirred bed reactor.

15. The method of Claim 1 which is practiced in a fixed bed reactor.

16. The method of Claim 1 which is operated in a batch mode.

17. The method of Claim 1 which is practiced at a temperature in the range of 250- 350"C.

18. The method of Claim 1 wherein tin metal dust is used as the source of tin for the catalyst.

19. The method of Claim 1 wherein aluminum metal dust or aluminum oxide powder is used as the source of aluminum for the catalyst.

20. A method for making methylchlorosilanes which enhances the rate of dimethyldichlorosilane formation, while reducing the weight ratio of methyltrichlorosilane to dimethyldichlorosilane, and maintaining or reducing the percent by weight of products in the resulting methylchlorosilane crude having a boiling point of greater than 70"C at atmospheric pressure which comprises, effective reaction between methyl chloride and powdered silicon in a reactor in the presence of an effective amount of catalyst consisting essentially of:: (a) a mixture of from about 5 to about 20 weight percent of the catalyst of elemental copper, from about 25 to about 60 weight percent of the catalyst of cuprous oxide and from about 25 to about 50 weight percent of the catalyst of cupric oxide, (b) from about 200 to about 5000 ppm tin ortin-containing compound as tin relative to copper, (c) from about 50 to about 5000 ppm aluminum or aluminum-containing compound as aluminum relative to copper, (d) up to about 7500 ppm iron or iron containing compound as iron relative to copper, and (e) 0.01 to 0.5 part zinc or zinc-containing compound as zinc per part of copper, wherein said catalyst is introduced along with powdered silicon at a rate sufficient to maintain in the reactor a catalyst content of from about 0.1 to about 10 weight percent of the catalyst-silicon contact mass and wherein said reaction is effected at a temperature in the range of 250- 350or.

21. A powdered silicon-copper catalyst contact mass consisting essentially of 0.1 to 10% by weight copper based on silicon, from about 200 to about 5000 ppm tin ortin-containing compound as tin per part of copper, and from about 50 to about 5000 ppm aluminum or aluminum-containing compound as aluminum per part of copper.

22. The composition of Claim 21 further consisting essentially of up to 7500 ppm iron or iron-containing compound as iron per part of copper.

23. The composition of Claim 21 further consisting essentially of from about 0.01 to about 0.5 part zinc or zinc-containing compound as zinc per part of copper.

24. The composition of Claim 21 wherein the copper consists essentially of from about 5 to about 20 weight percent elemental copper, from about 25 to about 60 weight percent cuprous oxide and from about 25 to about 50 weight percent cupric oxide.