Dawson结构磷钨酸稀土盐的制备、表征及其催化合成四氢呋喃研究

Preparation,characterization of rare earth phosphotungstates with dawson structure and their catalytic properties in synthesis of tetrahydrofuran

用复分解法合成出通式为RE2P2W18O62(RE=La,Ce,Y)的3种Dawson结构磷钨酸稀土盐,利用IR、SEM、XRD、Py-IR对其结构和酸性进行了表征,并用于催化1,4-丁二醇液相环化脱水合成四氢呋喃。考察了稀土元素种类、催化剂用量、反应时间、反应温度等因素对四氢呋喃收率的影响。结果表明La2P2W18O62表现出优异的催化活性,当磷钨酸镧用量占1,4-丁二醇质量的1.2%,反应温度为180℃,反应时间为25min,THF收率可达97.6%,催化剂重复使用5次,催化活性有所降低,THF收率仍可达86.6%。采用TG-DTA和Py-IR方法对使用前后催化剂表征结果显示,积碳结焦使催化剂Lewis酸中心减小是催化剂失活的原因。与传统酸性催化剂相比,采用La2P2W18O62作为反应催化剂不仅提高了反应收率(高于浓硫酸),简化了工艺流程,无酸腐蚀和污染问题,且催化剂无需处理即可重复使用多次。

Three kinds of rare earth phosphotungstates with dawson structure tormutateo as RE2P2W18O62 （RE=La,Ce,Y）were prepared and used in catalytic synthesis of tetrahydrofuran from 1,4-butanediol. The cata lysts were charactered by FT-IR, XRD and SEM. The influences of rare earth element, catalyst dosage, reac- tion temperature and reaction time were investigated. The results indicated that La2P2W18 062 showed the best catalytic properties in synthesis of tetrahydrofuran among the three rare earth heteropoly salts. Under the opti- mal condition, i.e. m（catalyst） 1.2%（relative to the dosage of 1,4 butanediol）, the reaction temperature（oil bath） was 180℃, the reaction time was 25 rain, the average yield of tetrahydrofuran could reach 97.6G. After reaction these catalysts could be recycled and still exhibited catalytic activity with a yield of 86.6% after five cy- cle reactions. It was found by means of TG-DTA and Py IR that the catalyst deactivation was due to decrease of the Lewis acid sites,which was caused by coking on catalyst surface. Compared with using sulfuric acid as cata lyst, the present procedure is a green productive technology characterized by process simplification, higher yield and no corrosion for facilities. Moreover, the La2PeWlsO62 can be used for many times.