Chemical processing of binary mixtures in a continuous flow microwave discharge reactor

The chemical processing of binary mixtures of benzene and acetylene with ammonia or carbon monoxide has been studied in the continuous flow microwave discharge reactor at 2450 MHz. The microwave discharge was modelled as a CSTR reactor, and the volume was assumed to be proportional to the power absorbed. Reynolds numbers in the lamina region were calculated for the gas flows in the silica reactor tube. The operating variables investigated were reactant ratios, reactor pressures, the effect of nickel in the discharge zone, flowrate through the reactor and the power absorption. Two microwave cavities were used. No reaction occurred in either of the carbon monoxide binary systems. The prime product of the reaction between benzene or acetylene with ammonia was hydrogen cyanide. No reaction or decomposition occurred below a critical mole ratio.in either system. Hydrogen and nitrogen were also formed on reaction in both systems together with small quantities of polymer. Acetylene, butadiene and aniline were also formed in the benzene/ammonia system. No azo-benzenes were produced. The selectivity of the hydrogen cyanide formation was ~ 90% in the acetylene/ammonia system and ~ 50% in the . benzene/ammonia system. The maximum yield of hydrogen cyanide was ·27.5 gm/kW.h in the acetylene/ammonia system and 35.0 gm/kW.h in the benzene/ammonia system. The rate of production of hydrogen cyanide was found to have an order of 1.5 with respect to the acetylene and uammonia in the acetylene/ammonia system in one set of experimental runs and was zero order with respect to the benzene and ammonia in the benzene/ammonia system, The values of the rate constants were dependent upon the cavity and the power absorbed. Comparison with other discharge processes indicates that increased frequency increases the production of hydrogen cyanide. In conclusion it was proposed that as the difference in ionization potential between the two compounds in the binary mixture increases it becomes progressively more difficult for reactive species to be produced in the microwave discharge, This was thought likely to be due to a change in the electron energy distribution in the microwave discharge .