Durable reactor for high temp. hydrogeneration of chloro-silane cpds. - consists of carbon@ fibre composite coated with silicon carbide, pref. with heating element of same material insulated with silicon nitride

摘要

Reactor for bringing chlorosilanes and H2 gases into contact at temps. above 600 deg.C has a chamber of SiC-coated C fibre composite material (I). The reaction chamber contains a heating element, also made from (I), pref. with electrical insulation of Si3N4, esp. hot pressed Si3N4. Pref. (I) has a 0.02-0.13 mm thick SiC coating and a matrix of C and C fibres with a density of 1.5-2.0 g/cc, Young's modulus of elasticity of 200-600 GN/m2 and tensile strength of 1500-8000 N/mm2. The C fibre content is 50-70 vol.%. USE/ADVANTAGE - The reactor is useful in the hydrogenation of SiCl4, SiHCl3, SiH2Cl2 and SiH3Cl. (I) has high strength, good elastic properties and great resistance to damage by pressure and thermal stress. The expansion coefft. of the matrix can be matched to that of the SiC coating. The coating protects the matrix from redn., which could destroy the appts. and contaminate the hydrogenated chlorosilanes. In an example, tests were carried out on samples of (A) pressed Si3N4 (`Cl32/HP'; RTM), (B) reaction sintered Si3Nr (`NCX5301'; RTM), (C) quartz, (D) SiC-coated C fibre composite (`CF222P22'; 55-65 vol.% C fibre; bulk density 1.6-1.7 g/cc), (E) uncoated C fibre composite (`CF212'; RTM), (F) another uncoated C fibre composite (`CX21'; RTM), the samples being dried for 72 h under N2. These were exposed to a stream of 464 cc/min mixt. of 25 mole-% SiCl4 and 75 mole-% H2 (1) for 6 h at 1150 deg.C + 15 h at 1350 deg.C or (2) at (A-C) 800 deg.C or (D-F) 1200 deg.C, with test after 462, 905 and 1367 h. In test (1), the loss in mass was (A) 0.131, (B) 0.185, (C) 6.113, (D) O, (E) +3.140, (F) +6.281%, the increase in mass of (E, F) being caused by reaction with SiCl4 to form SiC; and the gas leaving the reactor contained (A) 26, (B) 27, (C) 9, (D) 42, (E) 252, (F) 104 ppmv CH4 and (A) 12, (B) 2, (C) 125, (D) 29, (E) 5, (F) 8 ppmv CO. In test (2), the loss in mass was (A) 0.03, (B) 0.10, (C) 0.13, (D) 0.01, (E) 0.80% after 462 h; (A) 0.00, (B) 0.02, (C) 0.03, (D) -0.58, (E) -9.75% after 905 h; and (A) 0.03, (B) 0.10, (C) 0.16, (D) -0.45, (E) -9.05% after 1367 h.