PROCESS FOR PRODUCING TRICHLOROSILANE WITH STRUCTURE-OPTIMISED SILICON PARTICLES

Abstract

Chlorosilanes and methods of producing chlorosilanes. The process for producing chlorosilanes includes the step of selecting a chlorosilane having a general formulae (1) H.sub.nSiCl.sub.4-n and (2) H.sub.mCl.sub.6-mSi.sub.2 wherein n is 0 to 3 and m is from 0 to 4. The chlorosilane selected is then placed within a fluidized bed reactor. A hydrogen chloride-containing reaction gas is reacted with a particulate contact mass containing silicon at temperatures of 280° C. to 400° C. Where the operating granulation, understood as meaning the granulation or granulation mixture introduced into the fluidized bed reactor, contains at least 1% by mass of silicon-containing particles S described by a structural parameter S and wherein S has a value of at least 0 and is calculated as follows

[00001]$S=\left({\phi }_s-0.70\right).Math.\frac{{\rho }_{SD}}{{\rho }_F}$

Wherein φ.sub.S is symmetry-weighted sphericity factor, ρ.sub.SD is poured density [g/cm.sup.3], and ρ.sub.F is average particle solids density [g/cm.sup.3].

Claims

1-7. (canceled)

8. Process for producing chlorosilanes, the process comprises: selecting a chlorosilane having a general formulae (1) or (2)
H.sub.nSiCl.sub.4-n  (1)
H.sub.mCl.sub.6-mSi.sub.2  (2) wherein n is 0 to 3 and m is from 0 to 4; and placing the selected chlorosilane in a fluidized bed reactor, wherein a hydrogen chloride-containing reaction gas is reacted with a particulate contact mass containing silicon at temperatures of 280° C. to 400° C., wherein the operating granulation, understood as meaning the granulation or granulation mixture introduced into the fluidized bed reactor, contains at least 1% by mass of silicon-containing particles S described by a structural parameter S and wherein S has a value of at least 0 and is calculated as follows: $\begin{array}{cc}S=\left({\phi }_s-0.70\right).Math.\frac{{\rho }_{SD}}{{\rho }_F},& \mathrm{equation}\left(1\right)\end{array}$ wherein φ.sub.S is symmetry-weighted sphericity factor, wherein ρ.sub.SD is poured density [g/cm.sup.3], and wherein ρ.sub.F is average particle solids density [g/cm.sup.3].

9. The process of claim 8, wherein the symmetry-weighted sphericity factor φ.sub.S of the particles S is 0.70 to 1 and wherein the sphericity of the particles S describes the ratio between the surface area of a particle image and the circumference.

10. The process of claim 8, wherein the average particle solids density ρ.sub.F of the particles S has a structural parameter S≥0 is 2.20 to 2.70 g/cm.sup.3 and wherein the determination is carried out according to DIN 66137-2:2019-03.

11. The process of claim 8, wherein the operating granulation has a particle size parameter d.sub.50 of 70 to 1000 μm and wherein the particle size parameter is determined according to DIN ISO 9276-2.

12. The process of claim 8, wherein before entry into the reactor the reaction gas comprises at least 50% by volume of hydrogen chloride.

13. The process of claim 8, wherein the HCl and silicon are present in a molar ratio of HCl/Si of 5:1 to 2.5:1.

14. The process of claim 8, wherein the produced chlorosilane of general formula (1) is trichlorosilane (TCS).

Description

[0082] FIG. 1 shows by way of example a fluidized bed reactor 1 for performing the process according to the invention. The reaction gas 2 is preferably blown into the contact mass from below and optionally from the side (for example tangentially or orthogonally to the gas stream from below), thus fluidizing the particles of the contact mass to form a fluidized bed 3. To start the reaction the fluidized bed 3 is generally heated using a heating apparatus arranged externally to the reactor (not shown). Heating is typically not required during continuous operation. A portion of the particles is transported out of the fluidized bed 3 into the void 4 above the fluidized bed 3 with the gas flow. The void 4 is characterized by a very low solids density which decreases in the direction of the reactor outlet 5.

EXAMPLES

[0083] All examples employed silicon of the same type in terms of purity, quality and content of secondary elements and impurities. The grain fractions employed in the operating granulations were produced by crushing chunk Si.sub.mg (98.9% by mass Si) and subsequent milling or by atomization techniques known to those skilled in the art to produce particulate Si.sub.mg (98.9% by mass Si). Said fractions were optionally classified by sieving/sifting. Grain fractions having certain values for structural parameter S were thus produced in targeted fashion. Contact masses having defined mass fractions of silicon-containing particles having a structural parameter S of not less than 0 were subsequently blended by combining and mixing these grain fractions. The remainder of the grain fractions comprised silicon-containing particles having a structural parameter S of less than 0. The grain fractions together summed to 100% by mass. The granulations employed in the experiments had particle size parameters d.sub.50 between 330 and 350 μm. To ensure the greatest possible comparability between the individual experiments no additional catalysts or promoters were added.

[0084] The following process was employed in all examples. During the experiments the operating temperature of the fluidized bed reactor was about 320° C. This temperature was kept approximately constant over the entire experimental duration using a cooling means. HCl and the operating granulation were both added in such a way that the height of the fluidized bed remained substantially constant over the entire experimental duration and a constant molar ratio of the reactants (HCl:Si) of 3:1 was established. The reactor was operated at 0.1 MPa of positive pressure over the entire experimental duration. Both a liquid sample and a gas sample were respectively taken at run times of 48 h and 49 h. The condensable proportions of the product gas stream (chlorosilane gas stream) were condensed at −40° C. using a cold trap and analyzed by gas chromatography (GC) before TCS selectivity and the proportion of high boilers [% by weight] were determined therefrom. Detection was via a thermal conductivity detector. The uncondensable content of the product gas stream was analyzed on unreacted HCl [% by volume] using an infrared spectrometer. The obtained values after 48 and 49 h were averaged in each case. After each run the reactor was emptied completely and refilled with contact mass.

[0085] The employed contact masses and the results of the experiments are summarized in table 1. ms is the mass fraction of particles S having a structural parameter S>0.

TABLE-US-00001 TABLE 1 Experi- mS ≥ 0 [% TCS selectivity Productivity HCl [% by ment S by mass] [% by mass] [kg/(kg*h)] volume] VB1* 0.005 0.02 84 0.36 8 VB2* 0.005 0.2 85 0.34 7 VB3* 0.005 0.5 85 0.37 8 AB1 0.005 1 87 0.52 4 AB2 0.005 5 88 0.51 4 AB3 0.005 10 88 0.54 3 AB4 0.005 20 89 0.56 3 AB5 0.005 50 89 0.57 3 AB6 0.005 75 90 0.59 2 AB7 0.005 95 88 0.59 2 AB8 0.050 20 90 0.56 3 AB9 0.053 20 91 0.61 2 AB10 0.040 20 89 0.58 3 *not inventive