摘要
合成了纳米Beta沸石,并采用X射线衍射（XRD）、透射电镜（TEM）、比表面（BET）、程序升温脱附（NH3-TPD）以及吡啶-红外光谱（Py-IR）等方法对其结构和酸性进行了表征。比较了纳米Beta和常规大晶粒Beta沸石的催化性能,对纳米Beta沸石催化烷基化的关键参数进行了优化。结果表明：在硅铝物质的量比为25~30时,所合成的纳米Beta沸石具有较高的结晶度,晶粒尺寸在20 nm左右。同常规Beta沸石相比,纳米Beta沸石具有更大的BET比表面积和孔容,其比表面积可达600 m2/g,总孔容达0.42 cm3/g,介孔和大孔贡献超过50%。纳米Beta沸石具有较高的总酸量和B酸含量。作为苯和丙烯的烷基化催化剂,纳米Beta沸石具有更好的反应稳定性和选择性。在苯烯比3.0,反应温度150~160℃的条件下,异丙苯选择性可达89%,杂质正丙苯含量可降到极低水平。在工业试验中,纳米Beta沸石也表现出良好的综合性能,催化剂的稳定性和选择性优于同类Beta沸石催化剂。
Nano-Beta zeolite was synthesized and characterized by various techniques, such as X-ray diffraction（XRD）, transmission electron microscope（TEM）, low-temperature isotherm of nitrogen adsorption and desorption（BET）, NH3 temperature-programmed desorption（NH3-TPD） and pyridine infrared spectroscopy（Py-IR）. The catalytic performance of nano-Beta were also investigated in comparing with that of conventional Beta with large crystal size and the key parameters of alkylation were optimized in order to reach best performance in industrial cumene process. The results showed that the nano-Beta with molar ratio of Si O2 to Al2O3 25-30 had higher crystallinity and very small crystal size about 20 nm. Compared to conventional Beta with large crystal size, the nano-Beta had much larger BET surface area of 600 m2/g and higher pore volume of 0.42 cm3/g, which mainly came from mesopore and macropore, and possessed higher concentration of total acid sites and Bronsted acid sites. As catalyst for alkylation of benzene with propylene, nano-Beta zeolite was more stable and more selective. Under the conditions of benzene to propylene molar ratio of 3.0 and reaction temperature of 150-160 ℃, nano-Beta zeolite exhibited the best catalytic performance. Cumene selectivity reached as high as 89% and impurity, especially, n-propylbenzene decreased to very low level. During long term industrial test, nano-Beta catalyst also had much longer life span and higher selectivity than conventional Beta.
出处
《化学反应工程与工艺》
CAS
CSCD
北大核心
2015年第2期142-149,共8页
Chemical Reaction Engineering and Technology
