活性炭负载硅钨酸催化合成三聚甲醛的研究

以10%硝酸溶液处理过的活性炭(AC)为载体,采用不同质量分数的硅钨酸(SiW_(12))溶液为浸渍液,制备了不同负载量的SiW_(12)/AC催化剂,考察了催化剂在合成三聚甲醛中的催化性能,并用XRD、FT-IR、NH_3- TPD、BET、TG-DSC等手段对SiW_(12)/AC催化剂晶粒大小、催化剂表面的酸量及酸强度、比表面积及热稳定性等微观特性进行了表征。结果表明:AC上负载的SiW_(12)仍保持着Keggin结构;SiW_(12)/AC催化剂用于浓甲醛合成三聚甲醛的催化活性主要取决于催化剂表面的SiW_(12)分散度、总酸量和中强酸强度;SiW_(12)/AC催化剂SiW_(12)适宜负载量为30%,此时SiW_(12)分散度高,总酸量大和中强酸强度高,合成三聚甲醛的催化活性最高;SiW_(12)负载在AC上,热稳定性得到明显提高。

STUDY ON SiW12/AC CATALYSTS FOR PREPARATION OF TRIOXANE BY LIQUID PHASE METHODS

A series of SiW_(12)/AC catalysts with different silicotungstic acid loadings supported on acti- vated carbon which was treated with 10% HNO_3 solution were prepared by an impregnation method and the catalytic performance of SiW_(12)/AC for the synthesis of trioxane were investigated.The crystal size,acid strength,surface acid amount,specific surface area and thermal stability of the SiW_(12)/AC catalysts were characterized by XRD,FT-IR,NH_3-TPD,BET and TG-DSC.It was found that the SiW_(12)/AC acid had the better catalytic performance for trioxane synthesis.The heteropoly acid SiW_(12) supported on activated carbon still kept the Keggin structure when its loading amount were in the range of 20%-60%.The dispersion of silicotungstic acid,surface acid amount and acid strength of SiW_(12)/AC catalysts were correlated with their catalytic activity.When silicotungstic acid loadings were 30%,the SiW_(12)/AC acid had the highest catalytic activity for the trioxane synthesis,which had higher dispersion of silicotungstic acid,higher total acid content and higher strong acid strength.The thermal stability of the catalysts was improved when the silicotungstic acid catalyst was supported on activated carbon.