载体结构对异丁烷脱氢催化剂反应性能的影响

The influence of carrier structure on the reaction performance of the catalyst for isobutane dehydrogenation

以拟薄水铝石为主要原材料,采用不同的处理方式得到4种氧化铝载体并进一步制备负载型PtSnNa/Al_(2)O_(3)脱氢催化剂。XRD和N2吸附测试结果证明,拟薄水铝石原料经乙醇溶剂回流处理,然后在氮气气氛中焙烧,可以得到具有γ-Al_(2)O_(3)晶相的氧化铝载体(比表面积248 m^(2)·g^(-1)、总孔容0.89 mL·g^(-1)、平均孔径15.5 nm)。而直接在空气中焙烧得到的氧化铝的比表面积、总孔容和平均孔径都相对较小。将PtSnNa/Al_(2)O_(3)脱氢催化剂应用于异丁烷脱氢制异丁烯反应。反应性能评价测试结果表明,优良的贵金属脱氢催化剂载体应该具备较大的孔容和孔径。具有上述结构特征的氧化铝载体能够制备性能优异的异丁烷脱氢催化剂。该催化剂的异丁烷平均转化率47.2%,异丁烯平均选择性96.3%,并且该催化剂的寿命超过100 h。反应后积炭催化剂的热分析表征结果表明,通畅的孔道结构有利于反应中间物种迁移及反应产物的脱除,同时提高催化剂的容炭能力。

Four types of alumina carriers were obtained with pseudo-boehmite as the main raw material through different treatment methods,and further supported PtSnNa/Al_(2)O_(3)dehydrogenation catalysts were prepared.The test results of XRD and N 2 adsorption demonstrate that the treatment process of pseudo-boehmite had a significant effect on the structural characteristics of alumina support.An alumina support withγ-Al_(2)O_(3)crystal phase can be obtained by refluxing the pseudo-boehmite with ethanol solvent and subsequent calcining in a nitrogen atmosphere.Thisγ-Al_(2)O_(3)support has a specific surface area of 248 m^(2)·g^(-1),a total pore volume of 0.89 mL·g^(-1),an average pore size of 15.5 nm.However,the specific surface area,total pore volume,and average pore size of the alumina sample obtained by direct calcination in air are relatively small.Four PtSnNa/Al_(2)O_(3)dehydrogenation catalysts were used for catalyzing the reaction of isobutane dehydrogenation to isobutene.The PtSnNa/Al_(2)O_(3)catalyst made of alumina support with larger pore volume and pore size shows the optimal catalytic performance in isobutane dehydrogenation reaction.The average conversion of isobutane on this catalyst is as high as 47.2%,the average selectivity of isobutene is as high as 96.3%,and the lifetime of the catalyst exceeds 100 hours.The carbon-deposited catalyst after the reaction was investigated by thermal analysis method.The characterization results indicate that a smooth pore structure is conducive to the migration of intermediate species and the removal of reaction products,while improving the carbon capacity of the catalyst.