NH3处理的HY分子筛催化甲醛异丁烯Prins缩合反应

Formaldehyde and isobutene condensation via Prins reaction on HY zeolites treated with NH3

摘要:

对HY分子筛进行高温NH3处理，制备了一系列含氮样品。利用XRD、元素分析、29Si MAS NMR、NH3-TPD、CO2-TPD和TG等技术对NH3处理后样品的结构、酸碱性和反应后积碳量进行了深入表征。考察了其催化甲醛与异丁烯经Prins缩合制3-甲基-3-丁烯-1-醇(MBO)的催化性能，评价了反应条件及不同气氛氮化催化剂对反应性能的影响。结果表明，在温度为230 ℃、时间为4 h的条件下，以含水的体积分数为5%的氨气为氮源制备的催化剂对MBO的选择性达到89%，产率达到82%，并且反应后积碳量从未氮化HY催化剂上的27%显著下降到氮化催化剂上的4.3%。样品的酸性和碱性表征结果表明，NH3处理后的Y分子筛酸量减少而中等强度的碱量增加，从而抑制了副反应进行，提高了MBO的选择性，降低了积碳量。

Abstract:

A series of samples were prepared by treating HY zeolites with NH3 under high temperature. Their structures, acidity and basicity as well as the coke contents after reaction were systematically characterized by means of XRD, elemental analysis, 29Si MAS NMR, NH3-TPD, CO2-TPD and TG techniques. Their catalytic performances in the formaldehyde–isobutene Prins condensation were evaluated. The effects of samples nitridated under different atmosphere and reaction conditions were investigated in details. It is found that the selectivity of 3-methyl-3-buten-1-ol (MBO) increases to 89% and its yield is up to 82% on catalyst nitridated with NH3 containing 5% water under the optimized reaction temperature of 230 ℃ and reaction time of 4 h. Moreover, the coke contents decrease obviously from 27% on HY zeolite to 4.3% on nitridated sample after reaction. The acidity and basicity characterizations of the samples indicate that treating HY zeolites with NH3 leads to the decrease of the acidic sites and increase of the medium-strong basic sites, which inhibits the side reactions and enhances MBO selectivity. Meanwhile, the coke content decreases obviously on the nitridated sample due to its fewer acid sites and appropriate amount of basic sites.