尿素燃烧法制备镍基甲烷化催化剂及其催化反应性能

以拟薄水铝石、硝酸镍以及镁、钴、镧和铁的硝酸盐为原料,尿素为燃烧剂,采用尿素燃烧法制备系列镍基(以及含助剂)甲烷化催化剂。通过XRD和BET等对催化剂结构进行表征,采用固定床反应器评价催化剂的合成气甲烷化催化反应性能,考察Ni含量、尿素与原料质量比、焙烧温度和不同助剂等对催化剂结构和性能的影响,评价催化剂的稳定性。结果表明,Ni O质量分数为7.5%~44.8%时,采用尿素燃烧法均可制备γ-Al2O3为载体的镍基甲烷化催化剂,最佳制备条件为:尿素与原料质量比3∶1,焙烧温度450℃,燃烧时间40 min。26.1%Ni O/γ-Al2O3催化剂表现出较好的催化性能,在230℃和常压条件下,CO转化率和CH4选择性分别达99.5%和98.3%。26.1%Ni O-2.6%La2O3/γ-Al2O3催化剂在(230~700)℃经过多次升降反应温度和1 460 h的长周期稳定性测试,表现出较好的稳定性和耐热冲击性能。

Preparation of nickel based methanation catalysts by urea combustion method and their catalytic properties

Using pseudo boehmite as aluminum source,nickel nitrate as nickel source,magnesium nitrate,cobalt nitrate,lanthanum nitrate and ferric nitrate as the promoter source,a series of Ni based methanation catalysts with the promoters was prepared by urea combustion method.The structure of the catalysts was characterized by XRD and BET.The performance of the catalysts for syngas methanation was evaluated in a fixed bed reactor.The effects of NiO contents,mass ratios of urea and raw material,calcination temperatures and the promoters on the structure and performance of the catalysts were investigated.The results indicated that the syngas methanation catalysts with NiO mass fraction of 7.5%-44.8% and γ-Al₂O₃ support were prepared by urea combustion method.The optimal preparation condition was as follows:mass ratio of urea to raw material nitrate 3∶1,calcination temperature 450 ℃ and calcination time 40 min.Among all the catalysts,26.1%NiO/γ-Al₂O₃ catalyst exhibited the excellent performance for syngas methanation reaction.Under the condition of reaction temperature 230 ℃ and atmospheric pressure,the conversion of CO and the selectivity to CH₄ reached 99.5% and 98.3%,respectively.26.1%NiO 2.6%La₂O₃/γ-Al₂O₃ catalyst possessed good stability and heat shock resistance during 1 460 h stablity test after the reaction temperature was increased and then decreased many times in the range of (230-700) ℃.