Ce_(0.8)Zr_(0.2)O_(2)催化剂在催化氧化甲醛反应中的失活及再生

Deactivation and regeneration of Ce_(0.8)Zr_(0.2)O_(2) catalysts in the catalytic oxidation of formaldehyde reactions

Ce_(0.8)Zr_(0.2)O_(2)催化剂是由非离子表面活性剂F68为模板剂辅助合成,经HCHO催化氧化过程后导致催化剂失活.本研究考察了热处理和水洗两种再生手段对失活后Ce_(0.8)Zr_(0.2)O_(2)催化剂活性恢复的影响,并通过SEM、TEM、XRD、BET、XPS、FT-IR等表征手段对催化剂失活前后及再生后性能变化进行了分析.表征结果表明,新鲜催化剂的比表面积为98.7 m^(2)·g^(-1),失活后相较于新鲜催化剂比表面积下降至92.8 m^(2)·g^(-1),并且孔径增加,孔容减小,表面空位氧的含量下降最终导致催化剂失活,再生后催化剂能恢复一定的比表面积和孔容.其中,水洗再生能洗去覆盖在催化剂表面的积碳,但活性组分大大降低,催化氧化甲醛效果不佳,甲醛降解率仅恢复到75.2%,300℃热焙烧再生手段则可以恢复到96.0%.因此,热处理再生手段更优于水处理手段,且经过4次300℃热焙烧循环后,甲醛降解率在第6 h为56.1%.

The Ce_(0.8)Zr_(0.2)O_(2) catalyst was synthesized using nonionic surfactant F68 as a template for the catalytic oxidation of HCHO,which led to the catalyst deactivation.The effects of two regeneration means including thermal treatment,wash washing on the catalytic activity of the deactivated Ce_(0.8)Zr_(0.2)O_(2) catalyst were investigated.The fresh,used and regenerated catalysts were analyzed by SEM,TEM,XRD,BET,XPS,and FT-IR.The results showed that the specific surface area of deactivated catalyst(92.8 m^(2)·g^(-1))decreased compared to the fresh catalyst(98.7 m^(2)·g^(-1)).Moreover,the pore volume and the surface vacancies oxygen content of deactivated catalyst also decreased.After regeneration,a certain amount of the specific surface area and pore volume could be partially recovered.Among them,the water washing regeneration can remove the carbon covering the catalyst surface,but the active component was greatly reduced,and catalytic oxidation capacity for formaldehyde was not satisfactory(only 75.2%).The thermal regeneration at 300℃can recover the catalytic oxidation of formaldehyde to 96.0%.Therefore,thermal treatment model was better than water wash.And after four thermal roasting cycles at 300℃,the degraded formaldehyde was 56.1%after sixth hour.