La/Ni改性SO_4~(2-)/ZrO_2-Al_2O_3催化正丁烷异构化反应性能研究

利用浸渍法和共沉淀法得到La-Ni改性的硫酸化氧化锆催化剂,并对其在正丁烷异构化反应的性能进行考察。结果表明:改性方法对其催化异构化反应性能具有显著影响;用共沉淀法制得的催化剂在不降低异丁烷收率的前提下,通过减少副反应的发生来提高异丁烷选择性;而用浸渍法得到的催化剂表现出很高的异丁烷选择性,但正丁烷转化率显著降低,造成异丁烷收率也明显降低。利用Py-FTIR、低温氮气吸附-脱附、红外硫碳分析等表征,发现La-Ni改性处理对正丁烷在催化剂表面氧化脱氢能力影响不大,但对质子活化途径影响较大。共沉淀得到的催化剂表面超强B酸位密度的适度降低有利于提高单分子异构化途径所占的比例,而浸渍法所得催化剂表面B酸密度的显著降低导致其正丁烷转化受阻。

STUDY ON N-BUTANE ISOMERIZATION OVER La/Ni MODIFIED SO42-/ZRO2-AL2O3 CATALYST

The La-Ni modified sulfated zirconia-alumina catalysts were prepared by impregnation and co-precipitation method, respectively, and investigated the properties for n-butane isomerization. The results showed that the preparation method has a remarkable influence on n-butane isomerization. The catalyst prepared by co-precipitation method improves the selectivity of isobutane by reducing the side reactions and maintains the isobutene yield. Though the catalyst by impregnation promotes the selectivity of isobutane, the conversion of n-butane is decreased significantly, resulting in lower yield of isobutane. The characterization of the catalysts with Py-FTIR, low temperature nitrogen absorption and desorption, infrared sulfur and carbon analysis finds that La-Ni modification has markedly influence on carbocation formation pathway from n-butane but little effect on the oxidative dehydrogenation ability. The moderately decrease in density of surface strong Br?nsted acid by co-precipitation enhances the proportion of monomolecular isomerization. However, the impregnation method leads to a remarkable decrease of strong Br?nsted acid density on the surface and the n-butane conversion.