摘要
采用溶胶-凝胶法制备了Fe-Al-P-O催化剂,用N2物理吸附、透射电镜、红外光谱、 X射线衍射、程序升温脱附和微反技术研究了催化剂的物化性质和催化性能. 结果表明, Fe-Al-P-O催化剂平均粒径为20～40 nm, 比表面积为87 m^2/g. 催化剂表面由Lewis酸位Fe^3＋和Al^3＋及Lewis碱位 P = O 构成. Fe-Al-P-O催化剂催化丙烯在临氧条件下选择氧化的产物主要是丙烯醛; 在临氢和氧条件下,选择氧化产物则以环氧丙烷为主. 适当条件下,丙烯转化率可达9.6%, 环氧丙烷的选择性大于63%. 在原料气中引入水蒸气可以降低副产物丙烯醛的产率.
Fe-Al-P-O catalysts were prepared by the sol-gel method and characterized using N2 adsorption, transmission electron microscopy, X-ray diffraction, infrared spectroscopy, and temperature-programmed desorption （TPD）. The Fe-Al-P-O catalysts are highly dispersed and homogenous particles with diameter of 20-40 nm. There are Lewis acid sites, Fe^3＋ and Al^3＋ , and Lewis base sites, terminal oxygen of the P=O double bond, on the surface of the Fe-Al-P-O catalysts. TPD results show that propylene is adsorbed on the Lewis acid sites and the Lewis base sites with C=C double bonds and allylic hydrogen, respectively. H2O can also be adsorbed on Fe^3＋ and P=O with hydrogen and oxygen atoms. The catalytic performance of Fe-Al-P-O for the epoxidation of propylene was tested in a microreactor. The main selective oxidation product is acrolein with a feed gas composed of C3H6, O2, and N2, whereas the main selective oxidation product is propylene oxide if the feed stream is composed of C3H6, O2, H2, and N2. Under the conditions of atmospheric pressure and 100～300℃ , the conversion of propylene is 5.9 % ～ 9.6 % and the selectivity for propylene oxide is over 63 %. The epoxidation of propylene to propylene oxide is parallel with the oxidation of propylene to acrolein. The propylene adsorbed on the P=O sites with allylic hydrogen is oxidized into acrolein, whereas the propylene adsorbed on the Lewis acid sites, Fe^3＋ , with C=C double bonds transforms into propylene oxide. Adding H20 to the feed gas can inhibit the formation of acrolein because water decreases the adsorption amount of propylene.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2006年第6期522-526,共5页
基金
国家自然基金资助项目(20076035).
关键词
铁
铝
磷
氧
丙烯
环氧化
环氧丙烷
iron
aluminum
phosphorus
oxygen
propylene
epoxidation
propylene oxide
