Boron-doped activated carbon catalyzed reduction of dilute nitrite acid in oxidative esterification reaction in the coal to ethylene glycol process

Abstract

Coal to ethylene glycol (CTEG) technology has attracted more and more attention in the past decades. However, the by-production of nitric acid (NA) during oxidative esterification reaction not only causes equipment corrosion but also increases the cost of nitrogen replenishment and wastewater treatment, therefore it is meaningful to convert NA to useful feedstock. Herein, non-metallic B doped activated carbon (B-AC) was prepared and used to activate the reduction of NA. The structure and physicochemical properties of B-AC were firstly examined by SEM, ICP-OES, N2 adsorption and desorption isotherms, FT-IR, Raman, and XPS spectrum. Furthermore, the catalytic performance and stability of B-AC were evaluated in the batch experiments. Results showed that BET surface area and pore volume of B-AC decreased with the increase of B doping amount, and the content of BC3 component enhanced with the increase of calcination temperature. B-AC-800(10) with the mass ratio of AC to BA of 10 and the calcinated temperature of800 °C performed the best activity with about 85% and 66% conversion under 2% and 5% of NA solution, and each catalytic performance of B-AC is about 10% higher than pure AC. The slight blockage of pore structure due to the residual NA and the fall of B atoms from B-AC together lead to a decline of about 20% in NA conversion after five cycles. These findings indicated the application of B-AC as a promising catalyst to reduce NA wastewater in the CTEG process.