Thermo-chemical energy conversion and storage. Final report

Abstract

Research support for the cyclohexane/benzene heat pipe development program at Sandia Laboratories is reported. The apparent kinetics of the gas-phase catalytic dehydrogenation of cyclohexane to benzene in an internally recirculated (gradientless) reactor over the temperature range from 500 to 800/sup 0/F at 1 atm at various space velocities was studied. A kinetic model was developed based on a reversible mass-action rate expression and a catalyst effectiveness factor which is able to correlate both the conversion and reaction rate data very well over the temperature range 500 to 750/sup 0/F. The data taken at 800/sup 0/F appear to be qualitatively and quantitatively different than the data taken at the lower temperatures. It is not as yet clear, whether this can be attributed to a change in kinetic mechanism or some reversible alteration of the catalyst surface at the higher temperature. The formation of side products in this system over the same temperature range was also studied. Both the number and amount of side product(s) formed increases with increasing temperature and residence time. Over the temperature range from 500 to 600/sup 0/F the side products produced appear to be strongly related to the presence of low molecular weight unsaturated hydrocarbon impurities inmore » the (reagent grade) cyclohexane feed and it is possible that no side products would be formed were it not for the presence of these impurities. At temperatures above 600/sup 0/F, both the number and amount of side product(s) produced increases markedly. A test loop was designed and partially fabricated which will permit the study of the effects of long term continuous cycling of the system on catalyst activity and side product formation.« less