用TPD研究SO_2对NO催化氧化过程的影响

Effect of SO_2 on NO Catalytic Oxidation Studied by TPD Method

针对活性氧化铝载体及过渡金属氧化物催化剂上SO2 增强NO吸附并促进其氧化的实验事实 ,考察了反应温度对SO2发挥促进作用的影响 .结果发现 ,在 5 0～ 2 5 0℃间存在一适宜的温度范围 ,能使氧化铝上原本不氧化的NO在SO2 气氛中发生氧化 .对氧化铝预吸附不同组成的气体及在不同温度下吸附NO O2 SO2 后进行了TPD研究 .结果表明 ,SO2 的存在对NO氧化吸附生成NO2 高温脱附物种有利 .对Co3 O4/Al2 O3 催化剂上吸附SO2 NO2 的TPD研究结果显示 ,SO2 先吸附或与NO2共吸附都能使NO2 高温物种脱附增强 ,同时SO2 的弱吸附物种转变成强吸附物种或表面硫酸盐物种 ,意味着弱吸附的SO2 能与NO2 形成稳定的物种 ;而后吸附的SO2 竞争占据NO2 的吸附位 .推测表面上弱吸附的SO2 与NO O2 或NO2

Simultaneous removal of SO 2 and NO x from flue gas can be achieved with high efficiency using Al 2O 3 based sorbents through oxidative adsorption. The enhancement of NO adsorption and oxidation induced by SO 2 over active Al 2O 3 and supported transition metal oxide catalysts was observed in the experiments. The influence of reaction temperature on SO 2 promotion was investigated in a gas flow fixed bed reactor. Within the range of 50～250 ℃, NO could be oxidized largely over the active Al 2O 3 support as well as the supported catalysts into NO 2 in the presence of SO 2. The NO 2 production reduced rapidly beyond the temperature range. The TPD study was carried out for Al 2O 3 when it had preadsorbed reactive gases with different components or at different temperatures. The adsorption of SO 2 on the support surface favored the formation of NO 2, which could be desorbed at higher temperatures, from NO oxidative adsorption species. The effect of SO 2 on NO 2 adsorption over Co 3O 4/Al 2O 3 catalyst was also studied by TPD method. The pre adsorption of SO 2 or its co adsorption with NO 2 could prevent the NO 2 adsorption species from decomposition, meaning that the SO 2 on the surface of support or catalyst can interact with NO 2 and stabilize it. And the weakly bonded SO 2 species changed into strong adsorption species or surface sulfates after NO 2 desorption. Nevertheless, SO 2 in the gas phase competed for the sites that had been occupied by NO 2. One kind of multi molecular intermediate species formed by combining weakly adsorbed SO 2 and NO O 2 in an appropriate temperature range was suggested as active species for producing NO 2 in the presence of SO 2.