ISSN:
1572-879X
Keywords:
Mechanism of ethanol synthesis
;
rhodium-based catalysts
;
chemical trapping reaction
;
isotopic exchange reaction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The mechanism of ethanol synthesis from syngas over promoted rhodium catalysts has been studied by chemical trapping and isotopic exchange experiments. Mono-deuterated acetaldehyde (CH3CDO) was formed in chemical trapping reaction with CO + D2 as the syngas source and CH3I as the trapping agent, indicating that formyl adspecies was a C1-intermediate in the ethanol synthesis. In the experiment of in-situ chemical trapping and isotopic exchange reactions with D2 18O followed by purging with methanol in N2 stream, CH2DC18(16)OOCH3, CH3C18(16)OOCH3 and CH3CH18 2OH, CH3CH18O were formed, showing the existence of ketene and acetyl intermediate adspecies and the occurrence of oxygen-isotope exchange between these intermediates and D2 18O, respectively. Based on the mode of oxygen-isotope exchange between ketene (as well as acetyl) intermediate adspecies and the water formed in reaction, the isotopic repartitioning previously observed by Takeuchi and Katzer [1] can be explained without recourse to the hypothesis of the existence of highly strained oxirene intermediate. These results give further support to the ethanol-formation mechanism proposed by us [2]. Besides these, with substitution of D2 for H2 in the syngas conversion reaction, noticeable deuterium inverse isotope effects both on methanol and on ethanol formation were observed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00767191
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