Stoichiometric synthesis

The Schwechat plant was operated with a stoichiometric synthesis gas in a long term test of 5000 hrs. The residual hydrogen content could be decreased to 2.2 vol % which resulted in a heating value of 950 Btu/scf when about 1 vol % nitrogen was present in the synthesis gas. 

A significant feature of the operation of the two plants is that only a small deviation in feed gas composition is tolerable when using a stoichiometric gas. Greater deviations in the H2/CO ratio and in the residual C02 content of the feed gas will cause serious problems regarding SNG specifications. Thus, methanation of a stoichiometric synthesis gas is reasonable only when there are no stringent requirements for SNG specification. 

The dehydration reaction of aldoxime to form nitriles using the resting cells of Rhodococcus sp. YH3-3 was optimized. We found that the enzyme was induced by aldoxime and catalyzed the stoichiometric synthesis of nitriles from aldoximes at pH 7.0 and 30°C. Phenylacetonitrile once synthesized from phenylacetaldoxime was hydrolyzed to phenylacetic acid, since the strain has nitrile degradation enzymes such as nitrile hydratase and amidase. We have been successful in synthesizing phenylacetonitrile and other nitriles stoichiometrically by a selective inactivation of nitrile hydratase by heating the cells at 40°C for 1 h. Various nitriles were synthesized under optimized conditions from aldoximes in good yields. 

Unlike both the petrochemical and fermentation industries [1, 2], stoichiometric synthesis has for many years been a satisfactory tool for the preparation of molecules for application in life science industries. In recent years, however, the timely introduction of bio- and chemocatalysis has allowed organic synthesis in the fine chemical industry to meet both higher demands in molecular complexity of its products and a better process efficiency. 

The metal-ligand fragment L M, the number of carbon atoms x, and the substituents at the terminal sp -carbon may vary considerably and, correspondingly, the properties and reactivities. The early members of the series of cumulenylidene complexes (x=l, 2, 3 carbene, vinylidene and allenylidene complexes) have established themselves as invaluable building blocks in stoichiometric synthesis and as highly potent catalyst precursors. The higher members might potentially be very useful candidates for application as one-dimensional wires and in opto-electronic devices. 

Depending upon the stoichiometry of the feedstock source, a stoichiometric synthesis gas is achieved by adjusting the carbon/hydrogen ratio via shift conversion... 

If one assumes that the lithiation of 2 gives 17 [Eq. (15)], then Eqs. (15), (17), and (18) represent a very mild nickel(0)-induced stoichiometric synthesis of Li[Al(C2H5)3H] from lithium, hydrogen, and A1(C2H5)3. 

Description The gas feedstock is compressed (if required), desulfurized (1) and sent to a saturator (2) where process steam is generated. All process condensate is reused in the saturator resulting in a lower water requirement. The mixture of natural gas and steam is preheated and sent to the primary reformer (3). Exit gas from the primary reformer goes directly to an oxygen-blown secondary reformer (4). The oxygen amount and the balance between primary and secondary reformer are adjusted so that an almost stoichiometric synthesis gas with a low inert content is obtained. The primary reformer is relatively small and the reforming section operates at about 35 kg/cm2g. 

Montedison Low-Pressure Process. The Montedison low-pressure process [940], [1036], [1128], [1129] involves a split flow to two primary reformers. About 65% of the feed-steam mixture flows conventionally through the radiant tubes of a fired primary reformer followed by a secondary reformer. The balance of the feed-steam mixture passes through the tubes of a vertical exchanger reformer. This exchanger reformer has a tube sheet for the catalyst tubes at the mixed feed inlet. There is no tube sheet at the bottom of the tubes, where the reformed gas mixes directly with the secondary reformer effluent. The combined streams flow on the shell side to heat the reformer tubes in a manner similar to that described for the M. W. Kellogg KRES reformer, see Sections 4.1.1.8 and 5.1.4.3). The process air flow is stoichiometric. Synthesis is performed at 60 bar in a proprietary three-bed indirectly cooled converter with am-... 

In 2008, BeUer and coworkers reported catalytic and stoichiometric synthesis of novel 3-aminocarbonyl-,3-alkoxycarbonyl-, and 3-amino-4-indolyl-maleimides [162]. For instance, t-butyl ester 117 was prepared in 29% yield from 3-bromo-4-indolyl-maleimide 116 under the palladium-catalyzed carbOTiylation conditimis using f-butanol as the solvent and TMEDA as the base. 

Since the 1950s there have been many variants of the basic phospho-aldol reaction published for the stoichiometric synthesis of a-functionalised phos-phonates. For example, the widely studied Abramov reaction outlined in Scheme 1 b (when R = SiMej, this process can be considered to be a close relative of the Mukaiyama aldol reaction) has been used as a method of building a-functionalised phosphonates both without [4], and more recently with, control over stereochemistry at the a-carbon atom [5]. 

Under mechanochemical conditions, bifunctional benzil 71 is specifically reduced by NaBU, when used in a 4 1 stoichiometric ratio to quantitatively give racemic benzoin 72 (Scheme 6.26). Such result has never been described in solution reactions of these reagents. Furthermore, both carbonyl groups of 71 were quantitatively reduced to dihydrobenzoin (17/18), if a 2 1 ratio of 71 and NaBU, was applied under the otherwise identical conditions of Table 6.17. This stoichiometric synthesis provides meso-13 and rac-74 in 80% and 20% yields, respectively. This stereoselectivity compares with the reported 100 0 ratio in methanol (2h at 25°C) and the 85 15 ratio of 73/74 in ethanol (overnight). 

II.3.2 Stoichiometric Synthesis and Some Notable Properties of Organopalladium Compounds of Pd(0) and Pd(II)... 

II.3.2 STOICHIOMETRIC SYNTHESIS AND SOME NOTABLE PROPERTIES 159 TABLE 6. (Continued)... 

In 1969 Yamada and Otani reported an stereoselective stoichiometric synthesis of 4,4-disubstituted 2-cyclohexenones through an asymmetric Robinson annula-tion between preformed chiral aldehyde L-proline-derived enamines 20 and methyl vinyl ketone (Scheme 2.12) [33]. Surprisingly, only few examples of organocatalyzed Michael additions of aldehydes to enones have been reported since then. 

Owing to the high cost of iridium, this method is presented as a laboratory curiosity without any practical advantage over the classic method that requires five steps [99]. Less expensive metals such as iron, chromium, or manganese are more practical for stoichiometric synthesis. 

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