Nickel catalyst Nitrogen monoxide

Nitrogen-hydrogen mixtures resulting from low temperature conversion contain only 0.1 to 0.3% by volume of carbon monoxide. In this case the ca. 0.01 to 0.1% by volume of carbon monoxide and carbon dioxide present after carbon dioxide scrubbing is hydrogenated to methane (methanation) in the presence of nickel catalysts on a carrier in an exothermic reaction at 30 bar and 250 to 350°C ... 

In addition to the successful reductive carbonylation systems utilizing the rhodium or palladium catalysts described above, a nonnoble metal system has been developed (27). When methyl acetate or dimethyl ether was treated with carbon monoxide and hydrogen in the presence of an iodide compound, a trivalent phosphorous or nitrogen promoter, and a nickel-molybdenum or nickel-tungsten catalyst, EDA was formed. The catalytst is generated in the reaction mixture by addition of appropriate metallic complexes, such as 5 1 combination of bis(triphenylphosphine)-nickel dicarbonyl to molybdenum carbonyl. These same catalyst systems have proven effective as a rhodium replacement in methyl acetate carbonylations (28). Though the rates of EDA formation are slower than with the noble metals, the major advantage is the relative inexpense of catalytic materials. Chemistry virtually identical to noble-metal catalysis probably occurs since reaction profiles are very similar by products include acetic anhydride, acetaldehyde, and methane, with ethanol in trace quantities. 

Catalysts help customers comply cost-effectively with clean-air regulations. Hydrocarbons, carbon monoxide, and nitrogen oxides can be removed using supported precious metal catalysts. Organic sulfur compounds are converted to H2S using nickel/molybdenum or cobalt/molyb-denum on alumina catalysts. Sulfur can be recovered in a Claus process unit. The Claus catalytic converter is the heart of a sulfur recovery plant. 

The catalyst system for the modem methyl acetate carbonylation process involves rhodium chloride trihydrate [13569-65-8]y methyl iodide [74-88-4], chromium metal powder, and an alumina support or a nickel carbonyl complex with triphenylphosphine, methyl iodide, and chromium hexacarbonyl (34). The use of nitrogen-heterocyclic complexes and rhodium chloride is disclosed in one European patent (35). In another, the alumina catalyst support is treated with an organosilicon compound having either a terminal organophosphine or similar ligands and rhodium or a similar noble metal (36). Such a catalyst enabled methyl acetate carbonylation at 200°C under about 20 MPa (2900 psi) carbon monoxide, with a space-time yield of 140 g anhydride per g rhodium per hour. Conversion was 42.8% with 97.5% selectivity. A homogeneous catalyst system for methyl acetate carbonylation has also been disclosed (37). A description of another synthesis is given where anhydride conversion is about 30%, with 95% selectivity. The reaction occurs at 445 K under 11 MPa partial pressure of carbon monoxide (37). A process based on a montmorillonite support with nickel chloride coordinated with imidazole has been developed (38). Other related processes for carbonylation to yield anhydride are also available (39,40). 

As in the case of homogeneous catalysis, poisons can also lead to deactivation of heterogeneous catalysts. Soluble or volatile metal or nitrogen compounds can destroy acid sites, while carbon monoxide and sulphur compounds almost invariably poison nickel and noble metal hydrogenation catalysts by bonding strongly with surface metal atoms. These considerations often lead to the selection of less active, but more poison-resistant, catalysts for industrial use. 

A particular issue is the deactivation of methanation catalysts by carbon formation. Kuijpers et al. [345] observed significant carbon formation over a nickel/kieselgur catalyst containing 54wt.% nickel when exposed to a mixture of 10 vol.% carbon monoxide, 15 wt.% hydrogen, with a balance of nitrogen at 0.6 bar pressure and a 250 °C reaction temperature. Carbon filaments were found, which contributed to 10 wt.% of the catalyst mass at the inlet of the fixed bed. A nickel/silica catalyst showed practically no coke formation for 1000 h duration under the same conditions. 

In secondary reforming, the exit gas from the primary tubular reformer reacts adiabatically with air over a nickel-based catalyst. In this way, residual methane in the process gas is reduced to a low level and at the same time the nitrogen part of the ammonia synthesis gas is added. In most cases, the amount of air is adjusted in such a way that the stoichiometric ratio of hydrogen to nitrogen equal to 3.0 is obtained in the synthesis gas after carbon monoxide conversion and gas purification. However, there are also process schemes in which non-stoichiometric amounts of air are used this is discussed in Sect. 6.5. 

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