改善β沸石水热稳定性的研究

Study on Improving Hydrothermal Stability of β Zeolite

考察了不同浓度的盐酸、柠檬酸、酒石酸、草酸和磺基水杨酸溶液对Hβ沸石的脱铝效果 .结果表明 ,酸处理可以明显提高 β沸石的硅铝比 ,但沸石的相对结晶度显著降低 .然而 ,低浓度柠檬酸溶液处理不仅可以提高 β沸石的硅铝比 ,而且可以提高沸石的相对结晶度及水热稳定性 .在引入外来硅源的情况下 ,考察了低浓度柠檬酸溶液对 β沸石的脱铝补硅作用 ,提出了一种既可有效提高 β沸石硅铝比 ,又可使 β沸石具有较高结晶保留度的脱铝补硅方法 .采用该方法改性的催化剂 ,对丙烯水合醚化反应连续运转 72 0h ,丙烯转化率由 5 6 6 %仅降为 5 2 % 。

βzeolite shows high catalytic activity for hydration etherification of propene, but its stability needs to be improved. The most important reason for the deactivation of the catalyst is the structural aging caused by working under hydrothermal conditions. The effective way to increase the stability of the catalyst is to improve the hydrothermal stability of β zeolite. The dealumination of Hβ treated by hydrochloric acid, citric acid, oxalic acid, tartaric acid and sulfosalicylic acid was studied. Acid leaching can remarkably increase the n (SiO 2) / n (Al 2O 3) ratio of β zeolite, while its relative crystallinity decreases. Acid leaching with 0 25 mol/L of citric acid can increase the n (SiO 2) / n (Al 2O 3) ratio as well as the relative crystallinity of β zeolite. The dealumination and reinsertion of Si for β zeolite were studied by using low concentration of citric acid plus silicasol. A kind of method for dealumination and reinsertion of Si was proposed, which can increase the n (SiO 2) / n (Al 2O 3) ratio, relative crystallinity and hydrothermal stability of β zeolite. On unmodified β zeolite, the propene conversion decreased from 60% to 44% after 500 h running period, but on modified β zeolite, the propene conversion only decreased from 56 6% to 52 0% after 720 h running period.