碱性助剂对负载型固体酸催化剂上异丁烯齐聚的影响

Effect of Alkaline Additive on Isobutene Oligomerization over Supported Solid Acid Catalyst

采用浸渍法制备了Al2(SO4)3/SiO2催化剂,用热重-微商热重分析、X射线衍射、氨程序升温脱附和吡啶吸附傅里叶变换红外光谱等表征手段,研究了催化剂表面活性组分的存在状态,以及添加碱性助剂NaOH对催化剂酸性质的影响。表征结果显示,添加NaOH后,不改变Al2(SO4)3在载体表面的高度分散状态;Al2(SO4)3/SiO2催化剂表面基本为B酸中心,添加NaOH后,部分中强酸中心转化为弱酸中心;在40℃的低温条件下,中强酸中心是催化异丁烯齐聚反应的活性中心。稳定性实验结果表明,添加适量的NaOH后,Al2(SO4)3/SiO2催化剂具有高且稳定的二异丁烯(DIB)选择性,二聚体中DIB的选择性在反应时间70h内始终高达95%。

Supported Al2（SO4 ）3/SiO2 catalyst was prepared by impregnation. The existing state of Al2 （ SO4） 3 and the effect of NaOH addition on acidity of Al2 （ SO4 ） 3/SiO2 catalyst were studied by means of TG-DTG, XRD, NH3-TPD and Py-FTIR. Al2 （SO4 ）3 was highly dispersed on surface of support and remained without obvious change after addition of NaOH. Brtnsted acid sites dominated the solid surface. Addition of NaOH led to partial conversion of medium-strong acid sites to Weak ones. The high activity of the catalyst attributed to the medium-strong Brtnsted acid sites of the catalyst when isobutene oligomerization was carded out at 40 ℃. The stability test showed that Al2 （ SO4 ） 3/ SiO2 catalyst modified with suitable amount of NaOH exhibited high and stable diisobutene selectivity. The selectivity to diisobutene in dimers maintained as high as 95% during the on-stream period of 70 h.