一种用于正戊烷异构化的超强酸催化剂的合成与表征

SYNTHESIS AND CHARACTERIZATION OF MESOPOROUS ZIRCONIA MOLECULAR SIEVE FORn-PENTANE ISOMERIZATION

以水合无机硝酸锆为锆源、水合氯化铬为铬源,采用直接合成法制备含铬介孔氧化锆分子筛,并分别将纯相介孔氧化锆和掺铬介孔氧化锆经硫酸溶液浸渍制备相应的固体超强酸;采用X射线衍射、氨程序升温脱附等方法对所制分子筛及超强酸的物相及表面酸性进行表征,考察铬的掺入量及三乙醇胺的加入对合成产物的物相及性能的影响,并对超强酸催化正戊烷异构化反应活性进行评价。结果表明:铬的掺入使得氧化锆的四方相稳定存在,减少了向单斜相转化的可能性,增加了介孔氧化锆的热稳定性;三乙醇胺的加入使得含铬介孔材料的有序度增加,并有利于铬的均匀分散;在介孔氧化锆中掺铬后增加了固体超强酸的催化活性,不论是正戊烷转化率还是异戊烷选择性及收率都非常稳定,产物异戊烷的选择性在40%左右、收率在10%左右。

A Chromium-doped mesoporous zirconia molecular sieve was directly synthesized using zirconium nitrate hydrate and chromium chloride hexahydrate and then impregnated in H2 SO4 solution to make a super acid solid catalyst. XRD and NHa-TPD were adopted to characterize the phase and superfi- cial acidity of the as-synthesized molecular sieve and catalyst. The influence of the addition of triethano- lamine and chromium on synthesised products was studied in detail. The isomerization of n-pentane was used to evaluate the catalytic activities of the as-synthesized super acid samples. It is found that the addi- tion of chromium is helpful to the thermal stability of mesoporous zirconia because the possibility that the quadratic crystal of the zirconia transforms to monoclinic phase reduces and that the addition of tri- ethanolamine increases the order degree of the Cr mesoporous zirconia and the dispersion of chromi- um. The isomerisation results show that with chromium incorporation the acid sites and acid intensity of the mesoporus zirconia are increased, resulting in stable pentane conversion and isopentane selectivi- ty. The selectivity and yield of i-pentane are 40% and 10%, respectively.