Hydrocarbons alcohols, dehydrogenation

Indeed, the calculation showed that the activation energy of the dehydrogenation of the saturated hydrocarbons 1 (calculated from activation energies of the alcohol dehydrogenation 2 and its dehydration 3 on catalysts deposited with caustic soda from sulfate solutions) is equal to 97.8 for BeO, 91.7 for MgO, 45.6 for ZnO, and 35.4 kcal (mean) for CdO. The last of these values is already so small that the dehydrogenation of the saturated hydrocarbons becomes possible. 

Although the selectivity of isopropyl alcohol to acetone via vapor-phase dehydrogenation is high, there are a number of by-products that must be removed from the acetone. The hot reactor effluent contains acetone, unconverted isopropyl alcohol, and hydrogen, and may also contain propylene, polypropylene, mesityl oxide, diisopropyl ether, acetaldehyde, propionaldehyde, and many other hydrocarbons and carbon oxides (25,28). 

Methyl /-Butyl Ether. MTBE is produced by reaction of isobutene and methanol on acid ion-exchange resins. The supply of isobutene, obtained from hydrocarbon cracking units or by dehydration of tert-huty alcohol, is limited relative to that of methanol. The cost to produce MTBE from by-product isobutene has been estimated to be between 0.13 to 0.16/L ( 0.50—0.60/gal) (90). Direct production of isobutene by dehydrogenation of isobutane or isomerization of mixed butenes are expensive processes that have seen less commercial use in the United States. 

In 1869 Berthelot- reported the production of styrene by dehydrogenation of ethylbenzene. This method is the basis of present day commercial methods. Over the year many other methods were developed, such as the decarboxylation of acids, dehydration of alcohols, pyrolysis of acetylene, pyrolysis of hydrocarbons and the chlorination and dehydrogenation of ethylbenzene." ... 

Cyclohexane is a colorless liquid, insoluble in water but soluble in hydrocarbon solvents, alcohol, and acetone. As a cyclic paraffin, it can be easily dehydrogenated to benzene. The dehydrogenation of cyclohexane... 

The activity of elemental carbon as a metal-free catalyst is well established for a couple of reactions, however, most literature still deals with the support properties of this material. The discovery of nanostructured carbons in most cases led to an increased performance for the abovementioned reasons, thus these systems attracted remarkable research interest within the last years. The most prominent reaction is the oxidative dehydrogenation (ODH) of ethylbenzene and other hydrocarbons in the gas phase, which will be introduced in a separate chapter. The conversion of alcohols as well as the catalytic properties of graphene oxide for liquid phase selective oxidations will also be discussed in more detail. The third section reviews individually reported catalytic effects of nanocarbons in organic reactions, as well as selected inorganic reactions. 

While alcohols and acids are considered to be primary products (see Figure 4) ketones are probably formed in secondary reactions which only occur at higher temperatures 2). In Table II it can be seen that as the temperature increases, ketone production increases at the expense of alcohols up to a point after which both decrease (due to hydrogenation to hydrocarbons which under FT conditions are thermodynamically more stable (2), It has been suggested (2) that ketones result from the direct reaction between alcohols and surface carbon atoms and/or from the dehydrogenation of secondary alcohols (eg under high temperature FT conditions acetone and isopropyl alcohol are in thermodynamic equilibrium (2). 

Isopropyl alcohol production in 1950 exceeded 800,000,000 pounds, all made from petroleum. This alcohol is used mainly as a raw material for the production of acetone and also as a solvent. Acetone is made by the catalytic high temperature dehydrogenation or air oxidation of isopropyl alcohol. A much smaller part of the total acetone supply comes from fermentation and from hydrocarbon oxidation. Like isopropyl alcohol, part of the consumption is for solvent uses, but most serves as a raw material for other oxygenated compounds. 

In organic chemistry, elimination processes are those decompositions of molecules whereby two fragments are split off and the multiplicity of the bonds between two carbon atoms or a carbon atom and a hetero atom is increased. Such a broad definition also embraces the dehydrogenation of hydrocarbons and alcohols which is dealt with in Chap. 2. Here we shall restrict our review to the olefin-forming eliminations of the type... 

The effect of orientation is illustrated in an interesting manner by some experiments of Palmer and Constable on the rate of dehydrogenation of alcohols in presence of metallic copper. Primary alcohols appear to be adsorbed with the -CH2OH group attached to the catalyst. The hydrogen is lost from this group in the chemical change, so that it appears reasonable to suppose that this is the portion of the molecule which must be activated. The hydrocarbon chain, therefore, would not be expected to have much influence on the process, and it was indeed found by experiment that the rates of reaction of five primary alcohols are equal. Moreover, the temperature coefficients of the reaction velocity are also equal. 

All data on the kinetics of the catalytic dehydrogenation of hydrocarbons, amines, and alcohols obtained in our laboratory are expressed by the equation 12) ... 

Table 1 summarizes the experimental results obtained in our laboratory on the kinetics of the normal dehydrogenation of hydrocarbons (hexahydro-aromatics to aromatics, the open chain compounds butylene to butadiene, and ethylbenzene to styrene), of amines to ketimines, and of alcohols to aldehydes or to ketones, respectively, in the presence of metallic or oxide catalysts. Equation (1) was found to apply in all cases. Ko and h are given by... 

Fig. 20. Volcano-shaped curves for the dehydrogenation of hydrocarbons (I) and alcohols (II) and dehydration of alcohols (III) on CrjOs (85). For E and q, the units are kg. calories.

Experimental Activation Energies 1 e Bond Energies of Atoms in the Reacting Molecules with the Catalyst Qak Adsorption Potentials q and the Heights of the Potential Barriers E kg. cat./mole on Chromias of Different Methods of Preparation-, the Subscripts Designate 1—Dehydrogenation of Hydrocarbons, II—Dehydrogenation of Alcohols and Acids, III—Dehydration of Alcohols ... 

The activities of heat-integrated processes with recuperative heat exchange are mainly devoted to the conversion of primary fuels (hydrocarbons or alcohols) to hydrogen, with few exceptions - for example, investigations on the dehydrogenation of light alkanes in Schmidt s group [3]. The practical relevance and vitality of... 

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