DD265407B5 - Process for the preparation of methylchlorosilanes - Google Patents

Description

For this 6 pages drawings

Field of application of the invention

The invention relates to the preparation of methylchlorosilanes according to the principle of direct synthesis according to Müller-Rochow, Methylchlorosilanes with the main product dimethyldichlorosilane are the precursors of a wide range of technically and economically important silicone products such. As silicone coatings, oils, rubbers.

Characteristic of the known state of the art

It is known to prepare methylchlorosilanes according to the principle of direct synthesis according to Müller-Rochow (see, for example, R. J. H. Voorhoeve, "Organohalosilanes", Elsevier, Amsterdam, 1967).

The results of the synthesis reaction, d. H. the activity of the powdery mixture of silicon and catalyst (hereinafter called contact mass), the temporal stability of the activity, the selectivity of the reaction towards the preferred main product dimethyldichlorosilane (DDS) and the utilization of the raw materials are, apart from the reactor design, the reaction and the Qualities of the starting materials silicon and chloromethane to a great extent dependent on the nature of the copper-containing catalyst used. For selective DDS synthesis, copper as the metal or in the form of its compounds is the best catalyst so far. It has been used in the form of:

1. metallic copper, as:

a) mechanically comminuted electrolyte copper (e.g., DE-OS 2212218)

b) cement copper (eg DD-PS 21 380, DE-OS 2214611, GB-PS 1 201 466)

2. Alloying component of the silicon or copper silicide, in particular Cu ₃ Si (eg DE-PS 1158976, US-PS 2380995, M.Dvorak, Technical Direst. Prague, 1968, No.10, p.301)

3. Copper compounds, as:

a) oxidic copper, for example by pyrometallurgical process made of cement copper (DE-OS 3235943). In DE-OS 3312775 it is proposed to modify such partially oxidized copper preparations by adding portions of Kupferformiatzu to reduce the proportion of products having boiling points above 70 ⁰ C. The disadvantage of this procedure is mainly in the complicated production of partially oxidized copper.

b) copper salts such as CuCl (U.S. Patent No. 2,464,033, FR-PS 2,552,437), CuCl ₂ (U.S. Patent No. 2,464,033, FR-PS 2252437, FR-PS 2,552,438), Cu (O ₂ CH) ₂ (inter alia Radoslavljivic Khim.i Prakt.Primeninie Kremneorg.Soedinenie, Trudy Konf. Leningrad, 1958, No.6, p.37).

In DD-PS 250536 it has been proposed to use a mechanical mixture of copper powder and copper salts of lower aliphatic saturated mono- or dicarboxylic acids as catalysts with advantages for activity and selectivity of the reaction.

c) oxides; Hydroxides (SU-PS 130882; Trambouze, J.Chim.phys. 1954, No.51, S.5O5)

US Pat. No. 4,5000,772 claims a mixed catalyst based on copper-zinc-zinc, in which copper can also be used in the form of an anhydrous copper salt of an organic acid. The disadvantage of this method is the necessary use of pure silicon (over 98 mass% Si).

The variants described under 3. require the use of copper compounds. The compounds mentioned under 3b) and 3c) are commercially available products. The disadvantage of the compounds summarized under 3b) is the predominant formation of MTS in the start-up phase (Sadowski et al., React., KinetCatal., Lett, Vol.7, No. 1,1977, pp. 1-6). In general, all these catalysts in terms of activity, stability of activity and DDS selectivity still in need of improvement. Improvements have been made by the developments outlined above and also by the addition of a

Wide variety of activators and promoters sought to contact mass. Much of the elements of the periodic table have been proposed, but the results obtained by different authors are often contradictory. Already well-known activators and promoters are z. Zn, Al, Cd, Sb or their compounds; L (eg US Pat. No. 4,602,101, DE-OS 3501085, FR-PS 2552437), Cs (FR-PS 2552437), alkali metals (FR-PS 2552438 ) and alkaline earth metals (FR 8502550). Proposals for the use of novel activators and promoters can not be accepted without criticism, since their effect depends to a great extent on concrete boundary conditions, in particular on the catalyst system used and on the specific type of silicon used.

Object of the invention

The aim of the invention is an improved process for the preparation of methylchlorosilanes, with which the degree of conversion of chloromethane and silicon can be increased and the yield of dimethyldichlorosilane can be increased.

Explanation of the essence of the invention

The invention was based on the object, by developing a catalyst system which combines a high economy in the production with an improvement in the activity, the temporal stability of the activity and the DDS selectivity, the production of methylchlorosilanes with a high proportion of dimethyldichlorosilane (DDS) more effective. Surprisingly, it has been found that this object is achieved by the addition of a catalyst system to the contact mass, wherein the catalyst system consists of anhydrous copper salts of lower aliphatic saturated mono- or dicarboxylic acids and antimony or antimony compounds. Particularly suitable mono- or dicarboxylic acids are the first three members of the homologous series.

The contact material according to the invention contains 0.5 to 20% by mass, preferably 1 to 10% by mass, of copper in the form of a copper salt of a lower aliphatic, saturated monocarboxylic or dicarboxylic acid, e.g. Copper formate or copper oxalate, and 0.0005 to 0.05 mass%, preferably 0.001 to 0.01 mass%, antimony in the form of elemental antimony or an antimony compound, e.g. B. antimony (III) chloride. In addition, conventional activators (eg, Zn, Al or their compounds) and conventional promoters (eg, Sn, P and their compounds) can be blended in amounts known from the literature.

The contact material according to the invention is obtained by simple mechanical mixing of all components, for. As stirring, shaking, vortexing in the gas stream produced.

The direct synthesis is carried out in reactors, such as e.g. B. fluidized bed, fluidized bed or Rührbettreaktoren performed at temperatures ranging from 250 to 400 ° C, wherein the resulting gaseous reaction products are removed from the reaction zone. The contact material according to the invention already ensures a high proportion of DDS in the reaction product in the lower range of the stated temperatures and when using small copper catalyst amounts. Under these conditions, a di & selectivity reducing copper accumulation in the contact mass is avoided in continuous driving. Advantages of the procedure according to invention are a high activity of the contact mass, a high temporal stability and a very high DDS selectivity. Compared to the use of a conventional contact material based on copper powder, the contact material according to the invention also leads to a shortening of the formulation phase, d. h., the fresh contact mass, which is constantly added to the continuous, technical reactor, contributes to the reaction result after a short time.

embodiments

The results were determined on a rotationally shaken, gradient-free reactor according to Baglaj (Baglaj, B.I. et al., Kin. I. Cat. 1975, 16,804).

Reaction conditions:

Shaking frequency of the reactor 25 s " ¹ Contact Mass: • technical silicon (Si), grit d = 50 μπι - Si content = 96Ma .-% Fe content = 3.4Ma .-% - Al content = 0.25Ma .-% - Co-content = 0.3 mass% - miscellaneous = 0.05Ma .-% • copper-containing catalyst Chloromethane throughput 2,7 th- ¹ used contact material 10g

The experimental evaluation was determined by gas chromatography as a function of the duration of the experiment:

Activity in% by mass of methylchlorosilane in the gaseous reaction product at the reactor outlet Part a of the graphs

Selectivity in% by weight of DDS in the mixture of methylchlorosilanes

Part b of the graphic illustrations

Example 1 (result see Fig. 1 a, b) Contact mass according to the invention: Simit3Ma .-% CualsCu oxalate

0.003% by weight as Sb dust

0.25 mass% as Zn-dust reaction temperature. 320 ° C

Fig. 1 demonstrates the merits of the contact composition of the invention: high and stable activity, very high DDS selectivity.

Example 2 (result see Fig. 2 a, b) Contact mass according to the invention: Si with 3 mass% Cu as Cu-oxalate

0.003 mass% Sb as SbCl ₃

0.25 mass% Zn dust

Reaction temperature: 32O ⁰ C

Fig. 2 demonstrates the benefits of the contact material of the invention as in Example 1

Example 3 (result see Fig.3a, b)

Contact mass: Simit5Ma .-% Cu powder

0.25 Ma. -% Zn dust

Reaction temperature: 34O ⁰ C

Fig. 3 demonstrates the inferiority of a contact mass based on copper powder catalyst over the contact material according to the invention (Fig. 1 and 2) despite increased copper concentration and elevated reaction temperature

Example 4 (result see Fig. 4a, b)

Contact mass: Si with 5Ma .-% Cu powder

0.25 mass% Zn dust

0.003 mass% Sb dust reaction temperature: 340 ^° C

FIG. 4 shows that the Sb doping of the contact mass based on copper powder catalyst leads to an improvement in activity and DDS selectivity, but that the performance of the contact mass according to the invention is not achieved.

Example5 (result see Fig. 5a, b)

Contact mass: Simit 5Ma .-% as Cu-oxalate

0.25 mass% Zn dust

without Sb doping

Reaction temperature: 340 ^° C.

Fig. 5 gives an impression of the completely unsatisfactory performance of a contact mass based on an organic copper salt without Sb doping.

Examples (result see Fig. 6a, b)

Contact mass: Si with 3Ma .-% Cu formate

0.25 mass% Zn dust

0.003 mass% Sb-dust reaction temperature: 32O ⁰ C.

FIG. 6 shows that copper formate as the copper salt of a saturated carboxylic acid in combination with Sb doping also brings about the advantages according to the invention.

Claims (8)

1. A process for the preparation of methylchlorosilanes by reaction of gaseous chloromethane with a contact mass containing powdered silicon and copper-containing catalyst and optionally other known additives, characterized in that the copper-containing catalyst system is an anhydrous copper salt of lower aliphatic, saturated mono- or dicarboxylic acids and anitone or Anitmonverbindungen is used. 2. The method according to claim 1, characterized in that the catalyst system is contained with a copper content of 0.5 to 20 wt .-% in the contact mass. 3. The method according to claim 2, characterized in that the catalyst system is contained with a copper content of 1 to 10 wt .-% in the contact mass. 4. The method according to claim 1, characterized in that the catalyst system contains as copper salt copper (II) formate. 5. The method according to claim 1, characterized in that the catalyst system contains copper (II) oxalate as the copper salt. 6. The method according to claim 1, characterized in that the catalyst system is contained with an antimony content of 0.0005 to 0.05 Ma .-% in the contact mass. 7. The method according to claim 6, characterized in that the catalyst system is contained with an antimony content of 0.001 to 0.01 Ma .-% in the contact mass. 8. The method according to claim 1, characterized in that the catalyst system contains antimony in the form of antimony (III) chloride.