脉冲放电等离子体对La_2O_3催化剂组成的影响

Influence of Pulse Discharge Plasma on Composition of La_2O_3 Catalyst

选用稀土La2 O3 催化剂对CO进行了催化还原脱硫反应 .考察了在脉冲放电等离子体协同催化作用下 ,催化剂组成随反应温度和放电电压的变化规律以及其与常规催化作用下的不同之处 .结果表明 ,反应温度较低 (<377℃ )时 ,脉冲放电等离子体对催化剂组成的影响作用明显 ;反应温度较高 (>377℃ )时 ,脉冲放电等离子体仅影响催化剂各组分的含量 .LaOOH的生成是La2 O3 催化剂活性组分生成的关键步骤 ,并受温度的影响较大 ;存在一最佳放电电压效应 .

The catalytic activity of La 2O 3 catalyst influenced by plasma-temperature and temperature alone was studied. The reduction of SO 2 by CO over La 2O 3 catalyst was carried out in a stainless-steel needle-gauze reactor. The changing rules of the catalyst components and their phase contents with the increase of temperature and discharge voltage, and the difference while the catalyst working under plasma-temperature and temperature alone were studied, respectively. Before the reaction, the La 2O 3 catalyst was treated by hydrolysis. After the catalyst was subjected to plasma-temperature or temperature alone for 2 h, its XRD pattern was immediately measured for determining the catalyst composition and calculating their contents. The results showed that when the temperature was lower, the influence of pulse discharge plasma on the phase contents of the catalyst was notable. In the range from room temperature to 300 ℃, there was a new phase (LaO) 2(SO 4) appearing in plasma-temperature manner, however, in the range from 400 to 500 ℃, the catalyst composition had no difference in the two manners but the phase contents had different changing trends, compared with that in lower-temperature range. The emergence of the new phase (LaO) 2(SO 4) was due to plasma heating and plasma oxidation. The formation of LaOOH, which was greatly influenced by temperature, was the key process for active component of La 2O 3 catalyst. There was a most suitable discharge voltage for the reaction.