MoO_3/ZrO_2-TiO_2固体酸催化水解HCFC-22和CFC-12的研究

氟利昂无害化与资源化处理技术已成为当今环保领域的研究热点.采用混合沉淀过饱和浸渍法制备MoO_3/ZrO_2-TiO_2固体酸催化剂.将氟利昂通入以石英砂为催化剂填料载体的催化反应床中,利用管式炉加热,进行催化水解实验.从水解温度、水蒸气体积分数等反应条件考察了MoO_3/ZrO_2-TiO_2固体酸催化剂对CHClF_2(HCFC-22)和CCl_2F_2(CFC-12)降解效果的影响.结果表明,500℃焙烧的MoO_3/ZrO_2-TiO_2固体酸在相同的条件下催化水解HCFC-22和CFC-12,HCFC-22的降解率高于CFC-12,HCFC-22比CFC-12容易水解.两者的主要水解产物均为CO、CO_2、HF和HCl.被吸收后的产物为氟离子和氯离子,成分简单,经简单处理可被回收利用.反应60 h后HCFC-22和CFC-12的降解率仍维持在70%以上.由此可见,MoO_3/ZrO_2-TiO_2固体酸催化剂催化水解HCFC-22活性高且稳定性好.XRD和SEM表征表明,MoO_3/ZrO_2-TiO_2催化剂的主要结构为四方晶相的Zr(MoO_4)2掺杂锐钛型的TiO_2.

Catalytic hydrolysis of CHClF_2 and CCl_2F_2 over MoO_3/ZrO_2-TiO_2 solid acid catalyst

Chlorofluorocarbons( CFCs) have brought about many destroys on human health,as well as ecological and global environments because CFCs are greenhouse gases. The technology of harmless CFCs as a resource has became one of the research focuses in the environmental protection. The mixed precipitation with the saturated impregnation method was used to prepare MoO_3/ZrO_2-TiO_2 solid acid. Freon was introduced into the catalytic reaction bed with quartz sand as the catalyst-packing carrier,and the catalyst was heated by the tube furnace to carry out the catalytic hydrolysis experiment. The catalytic performance of MoO_3/ZrO_2-TiO_2 solid acid catalyst at the catalytic hydrolystic temperature and water vapor concentration for the catalytic decomposition of CHClF_2( HCFC-22) and CCl_2F_2( CFC-12) was investigated. The results showed that the catalytic decomposition of HCFC-22 and CFC-12 by MoO_3/ZrO_2-TiO_2 solid acid catalyst calcined at 500 ℃ in the same conditions revealed that the degradation rates of HCFC-22 are better than CFC-12,while HCFC-22 is easier than CFC-12 hydrolysis.The main degradation products were CO,CO_2,HF and HCl. The absorbed product is the fluoride ion and chloride ion with simple composition,and is used for recycling directly. The degradation rate of HCFC-22 and CFC-12 remained above 70% after 60 h. It can be seen that MoO_3/ZrO_2-TiO_2 solid acid catalyst catalyzes the high activity and stability of HCFC-22 and CFC-12. The XRD and SEM result revealed that the main phase of MoO_3/ZrO_2-TiO_2 catalyst was tetragonal Zr( MoO_4)_2 doped anatase TiO_2.