Process for preparing methylchlorosilanes with structure-optimised silicon particles

A process for producing methylchlorosilanes of general formula 1

• (CH3)nHmSiCl4-n-m (1),
• in which
• n represents values from 1 to 3 and
• m represents values of 0 or 1
• in a fluidized bed reactor, wherein a chloromethane-containing reaction gas is reacted with a particulate contact mass containing silicon in the presence of copper catalyst,
• wherein an operating granulation, i.e. 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, wherein S has a value of greater than 0 and is calculated as follows:
• S=(φ_s−0.04)·ρ_SD/ρ_F equation (1),
• S-(q_s-0.70);p_SD/p_F equation (1),
• wherein
• φS is symmetry-weighted sphericity factor
• ρSD is poured density [g/cm3]
• ρF is average particle solids density [g/cm3],
• the symmetry-weighted sphericity factor QS of the particles S is greater than 0.70 and equal to or less than 1, and
• the sphericity of the particles S describes the ratio between the surface area of a particle image and the circumference, wherein the average particle solids density ρF is 2.20 to 2.70 g/cm3, according to DIN 66137-2:2019-03.