Reformate ammonia

Co-adsorption experiments show a complex role of the nature and concentration of chemisorbed ammonia species. Ammonia is not only one of the reactants for the synthesis of acrylonitrile, but also reaction with Br()>nsted sites inhibits their reactivity. In particular, IR experiments show that two pathways of reaction are possible from chemisorbed propylene (i) to acetone via isopropoxylate intermediate or (ii) to acrolein via allyl alcoholate intermediate. The first reaction occurs preferentially at lower temperatures and in the presence of hydroxyl groups. When their reactivity is blocked by the faster reaction with ammonia, the second pathway of reaction becomes preferential. The first pathway of reaction is responsible for a degradative pathway, because acetone further transform to an acetate species with carbon chain breakage. Ammonia as NH4 reacts faster with acrylate species (formed by transformation of the acrolein intermediate) to give an acrylamide intermediate. At higher temperatures the amide may be transformed to acrylonitrile, but when Brweakly bonded, acrylic acid. The latter easily decarboxylate forming carbon oxides. 

Four hydrogen production techniques are reviewed hydrocarbon reforming ammonia cracking and two other, less common, production techniques, pyrolysis and aqueous phase reforming. 

In addition the investment cost for conventional water electrolysis is rather high, about 1 000 DM/kWe] in 1989. This would give a total investment for a world-size plant capacity 1 200 t/d of ammonia, which is about 2.5 times the value of a natural-gas-based steam reforming ammonia plant [590],... 

Table 33. Examples of aMPF.A process options in steam reforming ammonia plants ...

After bulk removal of the carbon oxides has been accomplished by shift reaction and C02 removal, the typical synthesis gas in steam reforming ammonia plants still contains 0.2-0.5 vol% CO and 0.005-0.2 vol% C02. In partial oxidations the residual CO content after the shift conversion is usually higher, around 1.5-2.5%. These compounds and any water present have to be removed down to a very low ppm level, as all oxygen-containing substances are poisons for the ammonia synthesis catalyst [735). 

Figure 104. Block diagram and gas temperature profile for a steam reforming ammonia plant...

Table 35. Main energy sources and sinks in the sleani reforming ammonia process... 

Table 36. Development of ilie nei energy consumption of natural gas based steam reforming ammonia plants (rea plant data) in GJ/t NH ...

Steam Reforming Ammonia Plants. Table 42 summarizes the achievable emission values for steam reforming ammonia plants [1323]. 

Mohri, T., Takemura, K., and Shibasaki, T., Application of advanced material for catalyst tubes for steam reformers. Ammonia Plant Safety, 33 86-100 (1993). 

TABLE 9.8. The First US Steam Reforming Ammonia Plants." ... 

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