Process for preparing chlorosilanes

Abstract

The present disclosure relates to a process for producing chlorosilanes in a fluidized bed reactor by reacting a hydrogen chloride-containing reaction gas with a particulate contact mass containing silicon and optionally a catalyst. The chlorosilanes have the general formula H.sub.nSiCl.sub.4-n and/or H.sub.mCl.sub.6-mSi.sub.2. The reactor design is described by an index K1, the constitution of the contact mass without catalyst is described by an index K2.sub.uncat, the constitution of the contact mass with catalyst is described by an index K2.sub.cat, and the reaction conditions are described by an index K3.

Claims

1. A process for producing chlorosilanes in a fluidized bed reactor, comprising: reacting a hydrogen chloride-containing reaction gas with a particulate contact mass containing silicon and optionally a catalyst, wherein the chlorosilanes have the general formula H.sub.nSiCl.sub.4-n and/or H.sub.mCl.sub.6-mSi.sub.2 where n=1-3 and m=0-4, and wherein the reactor design is described by an index $K1=.Math.\frac{V_{\mathrm{reactor},\mathrm{eff}}}{A_{\mathrm{tot},\mathrm{cooled}}.Math.d_{\mathrm{hyd}}}$ wherein is a fill level of the reactor; wherein V.sub.reactor, eff is an effective volume of the reactor [m.sup.3]; wherein A.sub.tot, cooled is a sum of cooled surface areas in the reactor [m.sup.2]; wherein d.sub.hyd is a reactor diameter [m]; and wherein V.sub.reactor, eff=1 to 60 m.sup.3 and d.sub.hyd=0.7 to 1.8 m; wherein the constitution of the contact mass without the catalyst is described by an index $K{2}_{\mathrm{uncat}}=R_{\mathrm{Si}}.Math.\frac{B_{\mathrm{AK}}}{d_{32}}$ wherein B.sub.AK is a breadth of the particle size distribution of the contact mass [m]; wherein d.sub.32 is a particle Sauter diameter [m]; wherein R.sub.Si is a purity of the silicon; and wherein B.sub.AK is 10 to 1500 m and d.sub.32 is 10 to 1000 m; wherein the constitution of the contact mass with catalyst is described by an index $K{2}_{\mathrm{cat}}=\frac{{}_{\mathrm{rel}}}{R_{\mathrm{si}}};$ wherein .sub.rel is a relative catalyst distribution in the contact mass; wherein .sub.rel is 0.005 to 3; and wherein R.sub.Si is 0.75 to 0.9999; wherein the reaction conditions are described by an index $K3=\frac{u_L}{v_F.Math.{10}^6}.Math.\frac{p_{\mathrm{diff}}}{g}.Math.\frac{1}{{}_F}$ wherein u.sub.L is a superficial gas velocity [m/s] of the gaseous reaction mixture in an interior of the reactor; wherein .sub.F is a kinematic viscosity [m.sup.2/s] of gaseous reaction mixture measured at the temperature in the interior of the reactor; wherein .sub.F is a density [kg/m.sup.3] of the gaseous reaction mixture in the portion of the reactor in which the fluidized bed is formed; wherein p.sub.diff is a pressure drop over fluidized bed [kg/m*s.sup.2]; and wherein u.sub.L is 0.05 to 4 m/s, .sub.F is 3*10-6 to 2/5*10-5 m.sup.2/s, .sub.F is 1.5 to 5 kg/m.sup.3 and p.sub.diff is 10 000 to 400 000 kg/m*s.sup.2; wherein K1 has a value of 1 to 10, wherein K2.sub.uncat has a value of 0.1 to 10 or wherein K2.sub.cat has a value of 0.005 to 3; and wherein K3 has a value of 1 to 700.

2. The process of claim 1, wherein K1 has a value of 1.2 to 9.

3. The process of claim 1, wherein K2.sub.uncat has a value of 0.5 to 8.

4. The process of claim 1, wherein K2.sub.cat has a value of 0.0075 to 2.

5. The process of claim 1, wherein K3 has a value of 1.5 to 600.

6. The process of claim 1, wherein the effective reactor volume V.sub.Reactor, eff is 3 to 40 m.sup.3.

7. The process of claim 1, wherein the hydraulic plant diameter d.sub.hyd is 0.8 to 1.7 m.

8. The process of claim 1, wherein the pressure drop over the fluidized bed reactor p.sub.diff is 20,000 to 100,000 kg/m*s.sup.2.

9. The process of claim 1, wherein the particle Sauter diameter d.sub.32 is 50 to 800 m.

10. The process of claim 1, wherein the breadth of the particle size distribution of the contact mass B.sub.AK is 100 to 1000 m.

11. The process of claim 1, wherein the relative catalyst distribution in the contact mass .sub.rel is 0.009 to 2.

12. The process of claim 1, wherein the superficial gas velocity u.sub.L is 0.06 to 2 m/s.

13. The process of claim 1, wherein the absolute pressure in the fluidized bed reactor is 0.1 to 1 MPa.

14. The process of claim 1, wherein the reaction is performed in a temperature range of 280 C. to 380 C.

15. The process of claim 1, wherein the fluidized bed reactor is integrated into an integrated system for production of polycrystalline silicon.

16. The process of claim 1, wherein the relative catalyst distribution in the contact mass .sub.rel is described by an index ${}_{rel}=.Math.\frac{o_{s\mathrm{pec},\mathrm{cat}}}{o_{\mathrm{spec},\mathrm{SiK}}};$ wherein is a mass ratio of catalyst/silicon granulation or catalyst loading; wherein O.sub.spec, cat is an average specific surface area of the catalyst determined according to BET method [m.sup.2/kg]; and wherein O.sub.spec, SiK is an average specific surface area of the silicon granulation determined according to BET method [m.sup.2/kg].

17. The process of claim 1, wherein the reactor diameter d.sub.hyd is described by an index $d_{hyd}=4.Math.\frac{A_{q,\mathrm{free}}}{U_{\mathrm{tot},\mathrm{wetted}}};$ wherein A.sub.q,free is a free flow cross section area of the portion of the reactor in which the fluidized bed is formed in interior [m.sup.2]; and wherein U.sub.tot, wetted is a wetted perimeter of all internals [m].

Description

EXAMPLES

(1) In order to apply the findings and correlations to productivity in the production of chlorosilanes and to define the ranges for the indices K1, K2 (K2.sub.uncat or K2.sub.cat) and K3 (operating ranges) detailed investigations on continuously operated fluidized bed reactors of different sizes were performed.

(2) Various experiments V were performed (Table 1: V1 to V28 for uncatalyzed HC and Table 2: V1 to V16 for catalyzed HC), wherein varied in each case were the hydraulic plant diameter d.sub.hyd with values from 0.7 m to 1.8 m, the superficial gas velocity u.sub.L with values from 0.05 m/s to 4 m/s, the particle Sauter diameter d.sub.32 with values from 5 m to 1000 m, the breadth of the operating granulation B.sub.AK with values from 10 to 1500 m and the relative catalyst distribution over the contact mass .sub.rel with values of 0.005 to 3, the purity with values of 0.75 to 0.9999, the catalyst loading A with values of 0.001 to 0.1 and the pressure drop over the fluidized bed p.sub.diff with values of 5000 to 400 000 kg/m*s.sup.2.

(3) The particle solids density .sub.P may be assumed to be approximately constant. The fluid density .sub.F is typically in a range from 1.5 to 5 kg/m.sup.3. The kinematic viscosity .sub.F is typically in a range from 3*10.sup.6 to 2.5*10.sup.5 m.sup.2/s.

(4) In the catalyzed variant only two optimized cases of combinations of K1 and K3 were reported to elucidate the effect of K2.sub.cat. The indices K1, K2.sub.uncat, K2.sub.cat and K3 resulted from the chosen parameters. The productivity [kg/(kg*h)], i.e. the produced amount of chlorosilanes per hour [kg/h] based on the amount of operating granulation employed in the reactor [kg], was used as a basis for evaluation of the selected combinations K1, K2.sub.uncat, K2.sub.cat and K3 and for definition of the optimal ranges. A productivity of >0.01 kg/(kg*h) is considered optimal/acceptable for both variants.

(5) TABLE-US-00002 TABLE 1 Productivity Experiment K1 K2.sub.uncat K3 [kg/(kg*h)] V1 0.84 2.61 4.08 <0.01 V2 2.94 1.64 7.61 0.225 V3 3.46 1.90 7.25 0.287 V4 1.37 2.16 6.80 0.087 V5 5.54 0.32 10.87 0.137 V6 3.92 2.24 0.78 <0.01 V7 2.68 2.33 31.80 0.331 V8 3.92 2.24 39.14 0.360 V9 2.40 12.28 71.36 <0.01 V10 2.95 3.28 75.14 0.501 V11 3.43 3.01 43.96 0.293 V12 4.33 1.90 40.77 0.420 V13 3.27 1.71 18.12 0.344 V14 5.62 0.19 10.87 0.021 V15 4.50 5.14 96.11 0.444 V16 4.06 5.78 84.46 0.627 V17 5.10 5.36 103.10 0.534 V18 4.80 6.93 178.39 0.112 V19 5.07 4.46 180.57 0.216 V20 4.55 3.82 441.73 0.199 V21 2.40 0.0098 408 <0.01 V22 3.93 9.90 271.83 0.034 V23 8.90 2.72 58.10 0.103 V24 6.06 3.54 475.71 0.091 V25 14.50 2.33 679.58 <0.01 V26 6.76 2.48 509.68 0.075 V27 8.31 2.97 611.62 0.029 V28 3.92 2.24 783 <0.01

(6) TABLE-US-00003 TABLE 2 Experiment K1 K2.sub.cat K3 Productivity V1 3.46 0.013 58.2 0.422 V2 3.46 0.369 58.2 0.473 V3 3.46 0.467 58.2 0.299 V4 3.46 0.876 58.2 0.232 V5 3.46 2.336 58.2 0.086 V6 3.46 2.947 58.2 0.017 V7 3.46 0.004 58.2 <0.01 V8 3.46 4.505 58.2 <0.01 V9 6.06 0.013 152.9 0.507 V10 6.06 0.369 152.9 0.511 V11 6.06 0.467 152.9 0.320 V12 6.06 0.876 152.9 0.245 V13 6.06 2.336 152.9 0.091 V14 6.06 2.947 152.9 0.019 V15 6.06 0.004 152.9 <0.01 V16 6.06 4.505 152.9 <0.01

(7) The experiments demonstrate that for both variants of the HC chlorosilanes are producible with particularly high productivity when the process is performed in the optimal ranges of the indices K1, K2.sub.uncat, K2.sub.cat and K3.