Ammonia, catalytic dehydrogenation

Zhou, X., et ah, Deposition ofFe-Ni nanoparticles on polyethyleneimine-decoratedgraphene oxide and application in catalytic dehydrogenation of ammonia borane. Journal of Materials Chemistry, 2012. 22(27) p. 13506-13516. 

Substrates which can undergo partial oxidation are characterized by a 7T-electron system or unshared electrons olefins and aromatics contain the first, methanol, ammonia and sulphur dioxide the second. Alkanes do not contain such electrons. Their selective oxidation appears to demand (thermal or catalytic) dehydrogenation to alkenes as the initial process. 

The benzoic acid might also be made by the Diels-Alder reaction of 1,3-butadiene with acrylic acid followed by catalytic dehydrogenation. Treatment of phenol with ammonia at high temperatures produces aniline, as mentioned in Chap. 2. Ethylbenzene can be rearranged to xylenes with zeolite catalysts. Thus, it could serve as a source of ph-thalic, isophthalic, and terephthalic acids by the oxidation of o, m, and p-xylenes. (The xylenes and other aromatic hydrocarbons can also be made by the dehydrocyclization of ethylene, propylene, and butenes, or their corresponding alkanes.44 Benzene can also be made from methane.195)... 

Catalytic Dehydrogenation of Diethanolamine Monsanto has developed a new method for production of the herbicide that eliminates most manufacturing hazards and all use of cyanide, ammonia, and formaldehyde in the synthesis of the key intermediate, DSIDA. Monsanto s novel catalytic synthesis of DSIDA uses a copper catalyst, and is safer because it is endothermic, produces higher overall yield, and has fewer process steps. 

For more examples of synthetic approaches that have reduced the use of ammonia, see also the case studies describing catalytic dehydrogenation of diethanolamine, HCN-free synthesis of the amino acids, and HCN-free synthesis of the specialty chemical, sarcosinate, all listed under the section on hydrogen cyanide, and the case study describing synthesis of the drug aprepitant. 

The adiabatic fixed-bed reactor with periodic flow reversal has three commercial applications, oxidation of SO2 for sulfuric acid production, oxidation of volatile organic compounds (VOCs) for purification of industrial exhaust gases, and NO, reduction by ammonia in industrial exhaust gases. Other possible future applications are steam reforming and partial oxidation of methane for syngas production, synthesis of methanol and ammonia, and catalytic dehydrogenations (Matros and Bunimovich, 1996). 

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

Consequently, by choosing proper conditions, especially the ratios of the carbonyl compound to the amino compound, very good yields of the desired amines can be obtained [322, 953]. In catalytic hydrogenations alkylation of amines was also achieved by alcohols under the conditions when they may be dehydrogenated to the carbonyl compounds [803]. The reaction of aldehydes and ketones with ammonia and amines in the presence of hydrogen is carried out on catalysts platinum oxide [957], nickel [803, 958] or Raney nickel [956, 959,960]. Yields range from low (23-35%) to very high (93%). An alternative route is the use of complex borohydrides sodium borohydride [954], lithium cyanoborohydride [955] and sodium cyanoborohydride [103] in aqueous-alcoholic solutions of pH 5-8. 

Platinum also is used extensively as a catalyst in hydrogenation, dehydrogenation, oxidation, isomerization, carbonylation, and hydrocracking. Also, it is used in organic synthesis and petroleum refining. Like palladium, platinum also exhibits remarkable abdity to absorb hydrogen. An important application of platinum is in the catalytic oxidation of ammonia in Ostwald s process in the manufacture of nitric acid. Platinum is installed in the catalytic converters in automobile engines for pollution control. 

Compound 85 was dehydrogenated at 300° over palladium black under reduced pressure to a pyridine derivative 96 which was independently synthesized by the following route. Anisaldehyde (86) was treated with iodine monochloride in acetic acid to give the 3-iodo derivative 87. The Ullmann reaction of 87 in the presence of copper bronze afforded biphenyldialdehyde (88). The Knoevenagel condensation with malonic acid yielded the unsaturated diacid 91. The methyl ester (92) was also prepared alternatively by a condensation of 3-iodoanisaldehyde with malonic acid to give the iodo-cinnamic acid (89), followed by the Ullmann reaction of its methyl ester (90). The cinnamic diester was catalytically hydrogenated and reduced with lithium aluminium hydride to the diol 94. Reaction with phosphoryl chloride afforded an amorphous dichloro derivative (95) which was condensed with 2,6-lutidine in liquid ammonia in the presence of potassium amide to yield pyridine the derivative 96 in 27% yield (53). 

The gas phase acid-catalyzed synthesis of pyridines from formaldehyde, ammonia and an alkanal is a complex reaction sequence, comprising at least two aldol condensations, an imine formation, a cyclization and a dehydrogenation (9). With acetaldehyde as the alkanal, a mixture of pyridine and picolines (methylpyridines) is formed. In comparison with amorphous catalysts, zeolites display superior performance, particularly those with MFI or BEA topology. Because formation of higher alkylpyridines is impeded in the shape-selective environment, the lifetime of zeolites is much improved in comparison with that of amorphous materials. Moreover, the catalytic performance can be enhanced by doping the structure with metals such as Pb, Co or Tl, which assist in the dehydrogenation. 

Figure 2 Volcano plots illustrating how catalytic activities depend on the nature of the metal used as catalyst, (a) Correlation between catal)hic activity for formic acid dehydrogenation and enthalpy of formation of metal formates. (Ref 10. Reproduced by permission of John Wiley Sons, Inc.) (b) Correlation between catal)hic activity for ammonia synthesis and degree of d-band fiUing in the metal used as catalyst. (Ref 12. Reproduced by permission of John Wiley Sons, Inc.) ...

A further method for the synthesis of the title compounds with only hydrogen as byproduct is the base-catalyzed dehydrogenative coupling (index D) of ammonia and tris(hydridosilylethyl)boranes, B[C2H4Si(R)H2]3 (R = H, CH3). Initially, the strong base, e.g. n-butyl lithium, deprotonates ammonia. The highly nucleophilic amide replaces a silicon-bonded hydride to form a silylamine and lithium hydride, which then deprotonates ammonia, resuming the catalytic cycle. Under the conditions used, silylamines are not stable and by elimination of ammonia, polysilazane frameworks form. In addition, compounds B[C2l-L Si(R)H2]3 can be obtained from vinylsilanes, H2C=CHSi(R)H2 (R - H, CH3), and borane dimethylsulfide. 

---