Process Design and Production of Boron Trichloride from Native Boron Carbide in Lab-Scale

Turkiye owns the biggest boron mine reserves of the world, so it is a necessity to research the possibilities of obtaining high-tech products of boron. This study is oriented to provide one of two main inputs, boron trichloride (BCl₃) gas and carbon/tungsten core, for production of boron fiber manufactured by well-hidden hot filament CVD method. In this study, the production of BCl₃ from native boron carbide (B₄C) was aimed. In the production process, two different originally designed set-ups were used. In the set-ups, the reaction occurred by passing chlorine gas (Cb) through B4C layer (10-110 g) which has different heap heights. The reactor was a vertical quartz tube heated up to 850°C by a tube furnace with silicon carbide (SiC) heating element. Chlorine as reaction gas and nitrogen as purging gas were dried in two different columns with calcium chloride (CaCl₂) and molecular sieve package. Flow rates of Cl₂, pressure and temperature changes in the set-ups were controlled respectively by rotameter, mass-flow controller (MFC), mercury U-tube manometer, thermocouple and thermometers which were placed in different zones. The product gases were separated in consecutive distillation columns and waste gases were conveyed to a rashing ring packaged gas scrubber. In pipelines, traps and condensers, various metal (i.e. Fe, Al, W, Si, and Cr) halides depending on the impurities of B4C were detected in different phases. The products in form of gas, liquid and solid were analyzed with FTIR, AAS, XRD and SEM/EDS. Production efficiencies (up to 85%) and consumption rate of CI₂ (up to 91%) were assigned.