多孔SiC陶瓷微孔道内合成Silicalite-2分子筛膜

Growth of Silicalite-2 Zeolite Film in Microchannels of Biomorphic Porous SiC Ceramics

榉木经高温热解转化为生物碳模板,通过液相渗硅反应工艺制备了保持木材微观结构的多孔SiC陶瓷.在生物形态多孔SiC陶瓷载体上采用原位沉积晶种-二次生长法在其微孔道内壁形成了一层5μm厚的Silicalite-2分子筛膜.利用XRD,SEM和BET对复合材料的相组成、微观结构和比表面积进行了表征,研究了水热晶化温度对原位沉积晶种和二次生长成膜的影响.经原位沉积(120℃,36h)晶种涂层后在载体孔道表面形成了一层球形颗粒堆积的连续晶种层,经170℃,36h的二次生长,晶种不断长大并交织生长形成连续致密单层分子筛膜.在多孔SiC陶瓷微孔道中沿垂直于载体表面方向形成了一层对齐排列的Silicalite-2棒状晶体,颗粒生长主要沿晶体的最长轴[101]方向进行.Silicalite-2/SiC复合孔结构材料的微孔体积为0.013cm3/g,BET比表面积为43.2m2/g,而相应的分子筛负载量为9.5%.

Aligned Silicate-2 zeolite membrane was synthesized by in situ seeding and secondary crystal growth in microchannels of biomorphic porous SiC ceramics support. The Silicate-2/SiC composite materials were characterized by XRD, SEM and BET. The effects of synthesis temperature and seed surface pre-treatment of the beech-derived SiC monolith were studied. The results show that a homogeneous coverage of 5 μm thick zeolite membrane within the pores channel of SiC monolith by Silicate-2 crystals was reached after in situ seeding at 120 ~C for 36 h with a following hydrothermal treatment at 170 ℃ for 36 h. The film oriented with [ 101 ] axis perpendicular to the substrate surface. The structure composites exhibit a hierarchical pore structure with a BET specific surface area of 43.2 m^2/g and microporous volume of 0. 013 cm^3/g. The weight percent of Silicate-2 in the final Silicate-2/SiC composites is about 9.5% after a coating procedure.