Dehydrogenations effects

The interpretation of the evaluation results is mostly focused on the undesired metal effects for the purposes of the present study. That is the dehydrogenation effect reflecting in hydrogen and coke extended production. The hydrogen and coke yields are shown in Figures 9.5 and 9.6. As obvious, the hydrogen and coke yields are lower on the catalytic samples deactivated with ADV-CPS than on the samples deactivated with CPS, which means that application of the ADV-CPS protocol is limiting the... 

The largest class consists of those oxides which are reduced to the metal, or a lower oxide, capable of producing a catalytic effect which is superposed upon the initial oxidation. The oxides of nickel and cobalt, of lead (PbOjj, Pb304, PbO), of copper (CuO, Cn20), at 350° belong to this class the reduced metals in these cases have a dehydrogenating effect upon the alcohol, and aldehyde results. 

In this case, the origin of the dehydrogenating effect displayed in the interaction between hydrogen peroxide and the substrate and conjugated dehydrogenation of hydrocarbons in the gas phase is the same. 

The presence of hydrogen is essential to counteract the dehydrogenating effect of ZnCl2 and also to obtain optimal pentane solubility. 

Contaminant-Metal Deactivation and Metal-Dehydrogenation Effects During Cyclic Propylene Steaming of Fluid Catalytic Cracking Catalysts... 

Reggel et al. observed that N-lithioethylenediamine in excess ethylenediamine as solvent rapidly isomerizes terminal alkenes to internal alkenes. Thus 1-octene on being refluxed with the reagent for 2 hrs. affords 90% of internal alkenes, mainly 2-octene. More striking is dehydrogenation, effected under very mild conditions. On addition of 4-vinylcyclohexene (1) to a solution of N-lithioethylenediamine... 

The stronger directing effects present in the indoline ring can sometimes be used to advantage to prepare C-substituted indoles. The aniline type of nitrogen present in indoline favours 5,7-substitution. After the substituent is introduced the indoline ring can be aromatized by dehydrogenation (see Section 15.2 for further discussion). A procedure for 7-acylation of indoline... 

Dehydrogenation of alkylbenzenes although useful m the industrial preparation of styrene is not a general procedure and is not well suited to the laboratory prepara tion of alkenylbenzenes In such cases an alkylbenzene is subjected to benzylic bromi nation (Section 11 12) and the resulting benzylic bromide is treated with base to effect dehydrohalogenation... 

HP Alkylation Process. The most widely used technology today is based on the HE catalyst system. AH industrial units built in the free world since 1970 employ this process (78). During the mid-1960s, commercial processes were developed to selectively dehydrogenate linear paraffins to linear internal olefins (79—81). Although these linear internal olefins are of lower purity than are a olefins, they are more cost-effective because they cost less to produce. Furthermore, with improvement over the years in dehydrogenation catalysts and processes, such as selective hydrogenation of diolefins to monoolefins (82,83), the quaUty of linear internal olefins has improved. 

Figure 5 illustrates a typical distillation train in a styrene plant. Benzene and toluene by-products are recovered in the overhead of the benzene—toluene column. The bottoms from the benzene—toluene column are distilled in the ethylbenzene recycle column, where the separation of ethylbenzene and styrene is effected. The ethylbenzene, containing up to 3% styrene, is taken overhead and recycled to the dehydrogenation section. The bottoms, which contain styrene, by-products heavier than styrene, polymers, inhibitor, and up to 1000 ppm ethylbenzene, are pumped to the styrene finishing column. The overhead product from this column is purified styrene. The bottoms are further processed in a residue-finishing system to recover additional styrene from the residue, which consists of heavy by-products, polymers, and inhibitor. The residue is used as fuel. The residue-finishing system can be a flash evaporator or a small distillation column. This distillation sequence is used in the Fina-Badger process and the Dow process. 

Other Technologies. As important as dehydrogenation of ethylbenzene is in the production of styrene, it suffers from two theoretical disadvantages it is endothermic and is limited by thermodynamic equiHbrium. The endothermicity requites heat input at high temperature, which is difficult. The thermodynamic limitation necessitates the separation of the unreacted ethylbenzene from styrene, which are close-boiling compounds. The obvious solution is to effect the reaction oxidatively ... 

Dehydrogenation. The dehydrogenation of ethyl alcohol to acetaldehyde can be effected by a vapor-phase reaction over various catalysts. 

When Pictet and Finkelstein condensed Aomoveratrylamine with /(omoveratroyl chloride and effected ring closure in the product, they obtained 3 4-dihydropapaverine (VII) but were unable to oxidise this to papaverine. This final step was achieved by Spath and Burger by the use of platinised asbestos at 200° in presence of air, and these authors found that tetrahydropapaverine (X) can be dehydrogenated to papaverine under similar conditions. 

An explanation for the difference in behavior of chloranil and DDQ towards A -3-ketones was first provided by Ringold and Turner. The A -enol (67) is produced faster than the more stable A -enol (68) but is not attacked appreciably by chloranil, which lacks sufficient oxidizing potential. Instead, the more easily oxidized A -enol (68) is dehydrogenated to (69) as it is produced. With DDQ, the faster formed A -enol (67) can be effectively dehydrogenated and the A -3-ketone (70) is formed ... 

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