Decomposition of simple alcohols, ethers and ketones in a microwave discharge

Abstract

The decomposition of various oxygen‐containing organic compounds including alcohols, ketones and ethers was studied in a microwave discharge at 0.3–2.0 torr in the absence of a diluent. Both gases and polymeric films were formed in each case and the extent of decomposition approached 100%. Hydrogen and carbon monoxide accounted for 90% of the total gaseous products. Trace amounts of gaseous low molecular‐weight hydrocarbons were also observed. The effect of pressure on the distribution of gaseous products was small. The gaseous products were similar to those predicted from reported high‐temperature equilibrium calculations. The C:O and the H:C ratios in the parent molecules were important parameters which determined the amount and the composition of the polymer film, respectively. The polymeric films formed in the discharge were characterised by several techniques including carbon‐hydrogen analysis, and i.r. and e.s.r. spectroscopy. The films were shown to have an average empirical formula of CH1.41O0.06 and to contain structural moieties of CO, CH3, CH2, CH and CC. The insoluble films were amorphous and contained free radicals. The polymeric films were thermally stable up to 200°c and decomposed at higher temperatures. The polymeric films formed were similar in all cases and independent of the nature of the parent molecule. It was inferred from the decomposition products that both the gases and the polymeric films were‐formed by the reaction of simple species such as CH and H in the microwave discharge.

Studies of the Glow Discharge Reactions of Methanol and Ethanol

“…The amounts of hydrocarbons C 3 in case of methanol and ethanol were not very significant. Comparison of the present results with those of Liu and Wight-man [ 7 ] is interesting. Thus, the decomposition of the parent compounds in the microwave discharge [ 7 ] approached 100 per cent for the seven oxygencontaining compounds, whereas hydrogen and carbon monoxide were the main (90%) decomposition products.…”

“…Comparison of the present results with those of Liu and Wight-man [ 7 ] is interesting. Thus, the decomposition of the parent compounds in the microwave discharge [ 7 ] approached 100 per cent for the seven oxygencontaining compounds, whereas hydrogen and carbon monoxide were the main (90%) decomposition products. Gases observed in the microwave discharge of alcohols are similar to those predicted for high temperature reactions [ 9 ].…”

“…The decomposition of various hydrocarbons in glow discharge has been shown to be independent of bonding in the parent molecules as well as of the reaction conditions [ 4 6 ]. The effect of various functional groups on the chemical reactions under non-equilibrium plasma conditions is of interest, but no systematic study has been reported for any functional group, except for the investigations of Liu and Wightman [ 7 ] and Hiraki [ B ], in which the effect of the functional groups containing oxygen on the reactions of organic compounds, such as alcohols, ethers and ketones in the electric discharge has been investigated.…”

“…Liu and Wightman [ 7 ] have found that in a microwave discharge alcohols, ethers and acetone decompose, and both gaseous products and polymeric film are formed.…”

Advantages and Limitations of Microwave Reactors: From Chemical Synthesis to the Catalytic Valorization of Biobased Chemicals

“…Thanks to Albert Wallace Hull, inventor of the magnetron, microwave technology was developed first by the military in radar applications and later as microwave oven and wireless radio communication . The first applications in chemistry followed in the late 1950s/early 1960s, mostly on decomposition or recombination of gases − or organics − and their polymerization. , Among the first were reports on gas phase and were said to be catalytic in naturecatalyzed by one of the gases present in the mixture . The first heterogeneous catalytic study on microwaves was possibly the one by Greaves and Linnett who investigated recombination of oxygen on different solid surfaces.…”