Rate constants determination for reactions of B₂O₃ with H₂O and HCl at high temperature using ab initio calculations

Primary combustion of boron-based fuel-rich propellants produces large amounts of HCl(g) and H₂O(g) which may react with B₂O₃(g) during the secondary combustion at high temperature. The reaction paths of the two reactions were expedited with Gaussian-09 program at CCSD(T)/aug-cc-pvtz//M062X/aug-cc-pvtz level, and the rate constants and Arrhenius parameters were estimated by using conventional transition state theory, variational transition state theory and variational transition state theory with interpolated single-point energies. The calculation results show that rate constant of the two reactions is in the range of 6.17 × 10⁻¹⁶ to 3.57 × 10⁻¹⁵ cm³ molec⁻¹ s⁻¹ and 1.58 × 10⁻¹⁶ to 1.47 × 10⁻¹⁵ cm³ molec⁻¹ s⁻¹ at temperature 2500–3500 K with activation energy of 118.01–136.29 kJ/mol and 155.12–168.28 kJ/mol, respectively.