低浓度亚硫酸铵氧化动力学的研究

Kinetics of Heterogeneous Oxidation of Low Concentration Ammonium Sulfite

亚硫酸铵直接氧化是实现新型氨法脱硫技术工业化的关键问题。采用搅拌反应器在硫酸铵浓度为3.70 mol/L、温度为45℃的溶液中,以硫酸钴为催化剂,对低浓度亚硫酸铵氧化气液反应动力学进行了研究。亚硫酸铵浓度、气相氧气分压和催化剂浓度范围分别为0.001～0.05 mol/L、0.02～0.1 MPa和10^-6～10^-4mol/L。实验结果表明,亚硫酸铵的氧化速率随着催化剂浓度的增加而增大,当亚硫酸铵浓度增加,可能存在催化剂临界浓度。当催化剂浓度大于临界点,氧化速率不再变化。反应分别对亚硫酸铵和气相氧气分压呈二级和一级。溶液pH=6时反应活化能是32.69kJ/mol。氧化速率最大时的溶液pH值随亚硫酸铵浓度的增大而增大。实验为新型氨法脱硫技术工业化提供了理论指导。

Direct oxidation of ammonium sulfite in aqueous solution is of commercial importance to industrialization of novel ammonia desulfurization technology. A stirred vessel is used to study the oxidation kinetics of low concentration ammonium sulfite which is catalyzed by cobalt sulfate in the solution contained 3.70 mol/L ammonium sulfite at 45 ℃. The concentration ranges of ammonium sulfite, cobalt sulfate and oxygen in gas phase are 0.001 -0.05 mol/L, 10^-6 - 10^-4 mol/L and 0.02 - 0. 1 MPa respectively. The oxidation rate increases with catalyst concentration. As the ammonium sulfite concentration increases, there is possibly a critical catalyst concentration beyond which the oxidation rate remains constant. The reaction is found to be first order with respect to oxygen and second order with respect to ammonium sulfite. The apparent activation energy for the overall reaction is 32.69 kJ/mol at pH 6.0. At the critical pH value the maximum oxidation rate increases with the increase of ammonium sulfite. The results provide reliable kinetic data for industrial operation.