On the reaction mechanism for hydrocarbon formation from methanol over SAPO-34 .2. Isotopic labeling studies of the co-reaction of propene and methanol
On the reaction mechanism for hydrocarbon formation from methanol over SAPO-34 .2. Isotopic labeling studies of the co-reaction of propene and methanol
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DOI：
10.1006/jcat.1996.0188
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发表时间：
1996-06-01
影响因子：
7.3
通讯作者：
Kolboe, S
中科院分区：
文献类型：
--
作者：
Dahl, IM;Kolboe, S
[C-13]甲醇和[C-12]丙烯（作为异丙醇进料，其立即转化为丙烯）在400 ℃下使用氩气作为载气在流动系统中在SAPO-34上共反应。进料在C-13和C-12原子中是等摩尔的。通过气相色谱-质谱法分析产物，从而允许确定同位素组成。虽然甲醇完全或几乎完全转化为烃，但大部分丙烯未反应。产物乙烯和丁烯主要由甲醇形成，并且含有大量过量的C-13原子。丙烯流出物主要由全C-12或全C-13分子组成，并且仅在很小程度上由同位素混合分子组成。随着催化剂失活的进行，丙烯出现未反应和所有新的烃由甲醇形成的趋势变得更加明显。结果表明，在该催化剂上，本体气相丙烯的连续甲基化不生成高级烃。先前提出的“碳池”机制可以解释在产物和同位素分布中看到的总效应，但指出SAPO-34中丙烯的非反应性可能是由丙烯在孔中的缓慢扩散引起的。(C)出版社：Academic Press，Inc.
[C-13]Methanol and [C-12]propene (fed as isopropanol, which is immediately converted to propene) have been co-reacted over SAPO-34 in a flow system at 400 degrees C using argon as a carrier gas. The feed was equimolar in C-13 and C-12 atoms, The products were analyzed by gas chromatography-mass spectrometry, allowing determination of the isotopic composition. While the methanol was completely or almost completely converted to hydrocarbons, the larger part of the propene emerged unreacted. The products ethene and butenes were mostly formed from methanol and contained a large excess of C-13 atoms, The propene effluent consisted mainly of all-C-12 or all-C-13 molecules and, only to a small extent, isotopically mixed molecules. The tendency for propene to emerge unreacted and all new hydrocarbons to be formed from methanol became more pronounced with progressing catalyst deactivation. The results show that the higher hydrocarbons are, over this catalyst, not formed by successive methylations of bulk gas-phase propene. A previously proposed ''carbon pool'' mechanism can explain the gross effects seen in the product and isotopic distribution, but it is pointed out that the nonreactivity of propene in SAPO-34 may be caused by slow diffusion of propene in the pores. (C) 1996 Academic Press, Inc.