Ammonia-hydrogen process

The choice of H2S rather than H2 as the circulating gas, in spite of the fact that the latter would give much higher effective separation factors, is based on the fact that to date no stable effective catalysts have been found which will catalyze the H2-H2O exchange with liquid water. The use of water vapor as in the Barr type tower makes the H2-H2O process unfavorable compared to the H2S-H2O process. Only the ammonia-hydrogen process (5) catalyzed in the liquid phase by potassium amide has emerged as competitive with the H2S-H2O exchange. A full... 

Solutions used in the ammonia-water, water-hydrogen, and ammonia-hydrogen processes are relatively noncorrosive and may be handled in ordinary steel equipment. Solutions used in all of the other processes are relatively corrosive, and require use of stainless steel or other expensive construction materials. 

Availability of this catalyst has led to interest in its possible use in dual-temperature water-hydrogen exchange processes. With liquid-water feed and recirculated hydrogen gas, this catalyst could be used in a dual-temperature process similar in principal to the GS process, with a schematic flow sheet like Fig. 1325. With ammonia synthesis-gas feed and recirculated water, this catalyst could be used in a dual-temperature process similar to the ammonia-hydrogen process flow scheme of Fig. 13.37, provided that impurities in synthesis-gas feed that would poison the catalyst can be recovered sufficiently completely. 

AECL did extensive development of a variant of the ammonia-hydrogen process based on aminomethane (CH3NH2) rather than ammonia. This has better kinetics and a wider envelope of operating temperatures but can only be configured bithermally. This process was superseded by development of processes based on water-hydrogen exchange. 

Steam Reforming Processes. In the steam reforming process, light hydrocarbon feedstocks (qv), such as natural gas, Hquefied petroleum gas, and naphtha, or in some cases heavier distillate oils are purified of sulfur compounds (see Sulfurremoval and recovery). These then react with steam in the presence of a nickel-containing catalyst to produce a mixture of hydrogen, methane, and carbon oxides. Essentially total decomposition of compounds containing more than one carbon atom per molecule is obtained (see Ammonia Hydrogen Petroleum). 

A variant of the H2/NH2 chemical exchange process uses alkyl amines in place of ammonia. Hydrogen exchange catalyzed by NH2 is generaHy faster using alkyl amines than ammonia, and a dual-temperature flow sheet for a H2/CH2NH2 process has been developed (69). 

A substantial portion of fhe gas and vapors emitted to the atmosphere in appreciable quantity from anthropogenic sources tends to be relatively simple in chemical structure carbon dioxide, carbon monoxide, sulfur dioxide, and nitric oxide from combustion processes hydrogen sulfide, ammonia, hydrogen chloride, and hydrogen fluoride from industrial processes. The solvents and gasoline fractions that evaporate are alkanes, alkenes, and aromatics with relatively simple structures. In addition, more complex... 

Dr. Woodward May I just make one comment to emphasize and to repeat what was said earlier Thermodynamics and kinetics. Yes, under the inlet conditions of several SNG processes, and also of methanation in ammonia and hydrogen processes, thermodynamically they are inside the carbon-forming region. At the exit they tend not to be. In practice, carbon is not formed. One could, therefore, conclude very simply that kinetics outweighs thermodynamics. 

Each year, about half the 3 X 108 kg of hydrogen used in industry is converted into ammonia by the Haber process (Section 9.12). Through the reactions of ammonia, hydrogen finds its way into numerous other important nitrogen compounds such as hydrazine and sodium amide (see Section 15.2). 

Chevron WWT [Waste water treatment] An integrated process for treating sour water from oil refineries, particularly for removing ammonia, hydrogen sulfide, and carbon dioxide. Only physical processes are used—volatilization and condensation under various conditions. Developed by Chevron Research Company and used in 14 plants worldwide in 1985. Martinez, D., in Chemical Waste Handling and Treatment, Muller, K. R., Ed., Springer-Verlag, Berlin, 1986, 180. 

F-S [Ferrous sulfate] A process for removing ammonia, hydrogen sulfide, and hydrogen cyanide from coke-oven gas by scrubbing with aqueous ferrous sulfate solution obtained from steel pickling. A complex series of reactions in various parts of the absorption tower yield ammonium sulfate crystals and hydrogen sulfide (for conversion to sulfur or sulfuric acid) as the end products. Developed in Germany by F. J. Collin A.G. 

Many of the undesirable substances present in gaseous or liquid streams form volatile weak electrolytes in aqueous solution. These compounds include ammonia, hydrogen sulfide, carbon dioxide and sulfur dioxide. The design and analysis of separation processes involving aqueous solutions of these materials require accurate representation of the phase equilibria between the solution and the vapor phase. Relatively few studies of these types of systems have been published concerning solutions of weak electrolytes. This paper will review the methods that have been used for such solutions and, as an example, consider the alkanolamine solutions used for the removal of the acid gases (H2S and C02) from gas streams. 

Atmospheric and vacuum distillation units (Figures 4.3 and 4.4) are closed processes, and exposures are expected to be minimal. Both atmospheric distillation units and vacuum distillation units produce refinery fuel gas streams containing a mixture of light hydrocarbons, hydrogen sulfide, and ammonia. These streams are processed through gas treatment and sulfur recovery units to recover fuel gas and sulfur. Sulfur recovery creates emissions of ammonia, hydrogen sulfide, sulfur oxides, and nitrogen oxides. 

Ammonia is one of the world s most important chemicals, in terms of the quantity manufactured. Some ammonia is processed into nitric acid and various polymers. Roughly 80% of ammonia is used to make fertilizers, such as ammonium nitrate. In the Haher process for manufacturing ammonia, nitrogen and hydrogen combine in the presence of a catalyst. 

Now chemists at the Central Research Laboratories of Produits Chimiques Ugine Kuhlmann (PCUK) at Lyons, France, developed beginning in 1970, under the direction of Dr F. Weiss, a novel continuous process for manufg hydrazine. The process is based on the discovery that ammonia, hydrogen peroxide, and a carbonyl compd, such as methyl ethyl ketone, react in presence of an amide and catalytic quantities of a phosphate to form an azine intermediate. This intermediate hydrolyzes quantitatively to hydrazine and to carbonyl compd which is recycled. The yield is claimed to be better than 75%... 

By analyzing energy barriers for product desorption under ammonia synthesis, CO hydrogenation, and NO reduction by CO, we can refine the models further. For these three processes, the reaction conditions are very different. The ammonia synthesis process is weakly exothermic, whereas the CO hydrogenation reaction has... 

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