氨合成铁催化剂上化学吸附物种的in－situ　FTIR谱

In-situ FTIR Spectra of Chemisorbed Species on Iron Catalysts for Ammonia Synthesis

应用原位傅里哀变换红外光谱方法，分别在４００～４５０℃、常压、高空速（１２０００～１４４００ｈ．ｓ．ｖ．ｇ．）的Ｈ２、Ｎ２／３Ｈ２或Ｎ２气氛的动态条件下，检测了双促进氨合成铁催化剂上的化学吸附物种，并分别在Ｄ２、Ｎ２／３Ｄ２或１５ＮＨ３／Ｈ２气氛中，进行了常规同位素验证实验．结果表明，催化剂表面的主要含氮化学吸附物种是分子态的Ｎ２．ａｄ，其ｕ（Ｎ－Ｎ）＝２０３６ｃｍ－１（ｓ），２０１２ｃｍ－１（ｗ）和１９３５ｃｍ－１（ｗ），而不是原子态的Ｎａｄ，其ｕ（Ｆｅ－Ｎ）＝１０８７ｃｍ－１（ｖｗ），和ＮＨａｄ其ｕ（Ｆｅ－Ｎ）＝８８６ｃｍ－１（ｖｗ），表面有相当量的化学吸附氢存在，其ｖ（Ｆｅ－Ｈ）＝２０５６ｃｍ－１（ｓ），１９５０ｃｍ－１（ｍｓ），１９３１ｃｍ－１（ｍ），１９０２ｃｍ－１（ｗ），９１５ｃｍ－１（ｓ，桥式）等．作为与报道过的激光拉曼光谱的互补研究，本结果支持了以缔合式途径为主、解离式途径为次的平行竞争缔合式合成氨催化反应机理．

Chemisorbed species on doubiy promoted ammonia synthesis iron catalysts are investigated by in-situ Fourier transform infrared spectroscopy under dynamic conditions of H2, N2/3H2, and N2, respectively, with high space velocity (12 000～14 400 h-1) at 1 atm and400 ～450℃. Also, the general isotopic verifications are carred out with D2, N2/3D2, and NH3/H2, respectively. The results indicated that, under above reaction condition, the most aboundant chemisorbed N-containing species are molecular N2,ad with u(N--N ) =2 036 cm-1 (s), 2 012cm-1 (w) and 1 935 cm-1 (w), rather than atomic Nad with u(Fe-N )= 1087 cm-1 (vw) andNHad with u(Fe-N) = 886 cm-1 (vw). There are a lot of chemisorbed hydrogen with u(Fe-H)= 2 056 cm-1(s), 1 950 cm-1 (ms), 1 931 cm-1 (m), 1 902 cm-1 (w) and 915 cm-1 (s, bridge).As a complementary study for the laser Raman spectra previously reported, this paper supported the associative catalytic reaction mechanism of ammonia synthesis with both parallel competitive major associative pathway and minor dissociative pathway.