Historic Developments and Recent Progress

Despite the obvious improvements achieved in the hydrocarbonylation of methanol, several problems remain to be solved before a technical realization of this process is achieved. One serious drawback is the formation of side products. Tlie liquid phase contains not only alcohols, aldehydes and acetals but also ethers, acetates, and minor amounts of acetic add accompanied by the 

Year Catalyst Syngas pressure fbar) H2/CO ratio Temp. rc Time (h Methanol conv. m Ethanol selectivity (%) Ref. 

At prolonged reaction times, increasing amounts of high molecular weight condensates are funned. In the gas phase, products like methane, dimethylether and CO2 are found in addition to the syngas components. All reaclion products have been identified by GC/MS measurements and by comparison of CjC reten tion limes with authentic samples [23, 24]. The product composition of a typical methanol homologation run obtained by a cobalt/iudine catalyst is given in Table H. 

Another unsolved problem is catalyst recycling, especially when bimetallic cobalt systems are used. In summary, it must be Slated that the known processes for methanol homologation still lack sufficient conversion rates and ethanol/ acetaldehyde selectivittes. 0 far. no ethanol yields exceeding 40% have been reported under acceptable catalyst concentrations and reaction conditions. 

Tlte hydrocarbonylation of methanol has been shown to be sensitive towards several parameters concerning both catalyst composition and reaction conditions. Methanol conversion and ethanol/acetaldehyde selectivity thus strongly depend on the nature and relative molar ratio of the cobalt compounds, ligands. 

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