Formation of carboxylic acids from small alkanes in zeolite H-ZSM-5
The activation of propane and isobutane in acidic zeolite H-ZSM-5 in the presence of both CO and H2O has been studied by in situ solid-state NMR and GC analysis. Evidence was provided for the conversion of propane to isobutyric acid at 373-473 K by cleavage of the C-C bond; methane and ethane are also produced. Isobutane is transformed into pivalic acid with simultaneous production of hydrogen. The low conversion (1-2%) at this temperature was rationalized by the existence of a small number of sites that are capable of generating carbenium ions which are trapped by CO at this temperature. A formate species was observed when CO and H2O were present on H-ZSM-5. This species disappeared in the presence of the alkane. At 573 K, the generation of large amounts of CO2 indicates a much higher conversion of the alkanes into carboxylic acids which, however, decompose under the reaction conditions.
Luzgin
MV
Group of NMR Spectroscopy for Catalytic Hydrocarbon Conversion, Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk.
Stepanov
AG
Sassi
A
Sommer
J