Catalytic research, Fixed Nitrogen

Professor H.S. Taylor, who was considered during his lifetime to be the dean of American Catalytic Chemists, is quoted as remarking that the work at the Fixed Nitrogen Research Laboratory could be considered as the basis of a textbook on heterogeneous catalysis. It included catalyst development, reactor design and basic catalyst studies. These latter included the usual basic studies of the physical and chemical adsorption of reactants, the kinetics of the reaction, studies of the catalyst surface and finally, mechanism studies and conjectures. In line with this suggestion we shall now give a compact summary of the basic work. 

This technological problem has stimulated a great deal of basic research into understanding how certain bacteria "fix" nitrogen at atmospheric pressure to make NH3. An enzyme called nitro-genase is responsible for Nj fixation in these bacteria.This enzyme contains Fe and Mo, which may play a catalytic role. 

Only the first step differs from the tertiary butyl alcohol conversion scheme. It has given rise to considerable research, particularly by Asahi, Dow, Japan Catalytic, Kureha, Mitsubishi, Montedison, Nippon Kayaku, Nippon Zeon, Sohio, Toyo Soda Ube, etc. It takes place in the vapor phase, between 300 and 40O°C, at 0.1 to 0.5 Pa absolute in the presence of a fixed bed of unsupported mixed oxides based on molybdenum, bismuth, tellurium and various additives. To avoid the flammability range, the isobutene and air feed must be diluted with nitrogen and possibly steam. With a residence time of 2 to 3 s, once-through conversion is better than 95 per cent and the molar yield of methacrolein is up to 85 to 90 per cent... 

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