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>A chemical titration method for quantification of carbenes in Mo- or W-containing catalysts for metathesis of ethylene with 2-butenes: verification and application potential
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A chemical titration method for quantification of carbenes in Mo- or W-containing catalysts for metathesis of ethylene with 2-butenes: verification and application potential
We introduce and experimentally validate a simple titration method for quantifying the number of carbenes acting as active sites in the metathesis of ethylene with 2-butenes over Mo- or W-containing catalysts. This method is based on the experimentally proven mechanistic sequence of carbene formation through the reaction of ethylene with oxidized metal oxide species: (i) reduction of M(vi) to M(iv) by ethylene, (ii) addition of ethylene to M(iv) to yield MC2H4 carbene and (iii) transformation of the latter to MCH2 upon reaction with C2H4 yielding C3H6. As MCH2 cannot produce C3H6 when reacting with C2H4, the amount of C3H6 formed in step (iii) corresponds to the number of catalytically active carbenes. The applicability of this method was supported by establishing a correlation between this number and the steady-state rate of propene formation in the metathesis of ethylene with 2-butenes.
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机译：我们和实验验证一个简单的介绍滴定方法量化的数量碳烯作为活跃的网站交换乙烯与2-butenes Mo -或W-containing催化剂。的实验证明了机械的序列碳烯形成的反应乙烯氧化金属氧化物物种:(i)减少M (vi) M由乙烯(iv), (2)添加乙烯产量MC2H4 M (iv)碳烯和(iii)转换的后者收益率与C2H4 C3H6 MCH2在反应。MCH2不能产生C3H6与C2H4反应时,C3H6步骤(3)中形成的数量对应的数量催化地活跃碳烯。通过建立关系的支持这个数字和丙烯的稳态速率在乙烯的置换作用形成2-butenes .
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