钛硅催化剂的酸碱改性处理

在甲醇－水体系中进行丙烯环氧化反应时，丙烯与双氧水在骨架钛上生成环氧丙烷，TS－1中含有的微量酸中心能够导致环氧丙烷与溶剂反应生成丙二醇，1－甲氧基－2－丙醇和2－甲氧基－1－丙醇，还能促进双氧水的分解，降低双氧水的有效利用率，这种酸中心主要来自于TS－1中硅羟基，配位不饱和的Ti^4 产生的L酸中心与微量铝产生的B酸中心，考察了TS－1催化的丙烯与双氧水环氧化过程中的酸碱效应，以及微量添加物的作用，结果表明：添加微量钠盐（Na2CO3或NaSO4)或NH4OH可以明显提高环氧丙烷选择性，采用氨水作为微量添加物能够明显提高催化剂的稳定性，酸处理无法脱除催化剂中微量铝，反而引入了部分酸中心，结果导致环氧丙烷选择性下降。

Pretreatment of acid and base over titanium silicalite

In methanol water solution,framework Ti can catalyze propylene and H-2O-2 to PO. The minimum acidity in TS 1 can catalyze the solvolysis reaction of PO to propylene glycol, 1 methoxy 2 propanol and 2 methoxy 1 propanol. Acidity in TS 1 can also decompose H-2O-2 and decrease H 2O 2 utilization rate. Acidity of TS 1 came from Si-OH, framework Ti acted as Lewis acid sites and minimum Al .In this paper, the effect of acid and base, and the effect of additives in solvent on the epoxidation of propylene catalyzed by TS 1 was studied. It was found that PO selectivity increased significantly if a small amount of additives(Na-2CO-3, Na-2SO-4, NH-4OH) was added in the solvent. NH-4OH is the most optimum additive because it can increase the stability. Acid treatment can not get rid of the small amount of Al of TS 1.On the contrary, acid treatment can introduce a part of unwanted acid center .Thus acid treatment decreased PO selectivity in epoxidation of propylene.