水热合成甲烷催化燃烧催化剂条件探讨及优化

Investigation and Optimization of Hydrothermal Synthesizing Condition of Catalysts for Low—Temperature Methane Catalytic Combustion

用正交实验的方法对水热合成甲烷燃烧催化剂制备条件进行了研究和分析。结果表明,在起燃阶段催化剂活性组分是主要影响因素,在中期和完全燃烧阶段所有被考虑因素均对催化剂活性有重要的影响。正交实验分析优化的反应条件为:以 Co(NO_3)_2为前驱反应物,尿素加入量为反应所需物质的量的4.5倍,反应温度160℃下保持反应4 h,120 C 干燥15 h 后500℃焙烧3 h。正交实验15号样品 T_(90%)最低,为549℃,在最优条件下合成所得17号样品活性得到大幅度提高,其中T_99%为447℃。XRD 和 HET 实验结果表明,催化剂在500～800℃焙烧后为同一晶体结构,随温度的升高晶体粒径增大,比表面积下降,从而导致催化剂活性下降。

The hydrothermal synthesizing condition of catalysts for low- temperature methane catalytic combustion was investigated and analyzed through the orthogonal experiment. The results show that the activity of catalyst is influenced mostly by the activity components in the initial phase of combustion, in the middle and final phase all the factors influence the activity of catalyst mostly. The proper hydrothermal synthesizing condition was that using Co（NO3 ）2 as reactant, carbamide was 4.5 times than what was needed, the reaction maintains 4 h at 160 ℃. Then dried 15 h at 120 ℃ and roasted 3 h at 500℃. The No. 15 sample of orthogonal experiment acquired the best activity and the T99% was 549 ℃. The activity of the additional sample synthesized at the optimized condition improves largely and the T99%. was 447℃ . X--ray diffraction（XRD） and BET reveal the catalysts maintain the same crystal structure at a temperature range from 500 ℃ to 800 ℃, the particle size increases and the surface area is decreased with the increasing of calcination temperature, as a result the activity of catalyst is decreased.