A. A. Balandin

Kinetics of the catalytic reduction of organic peroxides and hydroperoxides Communication 1. hydrogenation of α, α-dimethylbenzyl hydroperoxide, α, α-dimethylbenzyl ethyl peroxide, and 1, 2, 3, 4-tetrahydro-1-naphthyl hydroperoxide

1. n nIt was shown that organic peroxides and hydroperoxides are rapidly hydrogenated to the corresponding alcohols over Raney nickel, which is in accord with calculations based on the multiplet theory. n n n n n2. n nThe kinetics of these reactions were investigated. It was found that the nature and structure of the substituents affect the rate of reduction, and as a consequence di-tert-butyl peroxide is not hydrogenated at all at temperatures ranging up to 50°. n n n n n3. n nThe actions of Raney nickel and palladium catalysts were investigated. The peroxy compounds were hydrogenated over both catalysts, mainly in accordance with a zero-order law. The apparent activation energies for the reduction of peroxides and hydroperoxides were close in value, being 5.4 and 5 kcal/ mole respectively. The hydrogenation of a, α-dimethylbenzyl ethyl peroxide was retarded by the reaction products. n n n n n4. n nThe rate of catalytic reduction depends on the nature of the solvent. In alcoholic solution reaction proceeds more rapidly than in cyclohexane, benzene, or decahydronaphthalene.

Mechanism of the deactivation of nickel catalysts by steam under pressure

1. n nAn investigation was made into the deactivating effect of steam on nickel catalysts in the course of their preparation by reduction with hydrogen under pressure. n n n n n2. n nIt was shown that pretreatment of a mixture of nickelous oxide and carrier (Al2O3, MgO) with steam under pressure results in the formation of catalysts of low activity. Similar treatment of a reduced carriersupported nickel catalyst has a very much smaller effect on activity. n n n n n3. n nIt was shown that steam treatment of a coprecipitated mixture of nickelous oxide and alumina ( or magnesia) under pressure results in a far-reaching irreversible change, namely recrystallization with great reduction in specific surface. n n n n n4. n nIt is evident that the deactivation of reduced nickel catalysts by steam in the course of their use is due to the formation of nickelous oxide films or phases that rapidly recrystallize and are reduced with difficulty with formation of coarsely dispersed nickel. It is probable that the mechanism here proposed is applicable also to the deactivation of iron catalysts by water vapor.

Selectivity of catalysts Communication 3. Hydrogenation of isoprene over Raney nickel

1. n nA study was made of stepwise character of reaction and selectivity in the hydrogenation of the conjugated double bonds of isoprene in presence of Raney nickel. n n n n n2. n nAt 20° and atmospheric pressure the double bonds of isoprene are hydrogenated successively. n n n n n3. n nOver a catalyst whose surface has been blocked with pyridine or quinoline, under normal conditions isoprene is hydrogenated to a mixture of isopentenes, after which reaction stops completely. n n n n n4. n nIn presence of pyridine the selectivity of the process is maintained also in the hydrogenation of isoprene under pressures of up to 88 atm.

Vapor-phase hydrolysis of halobenzenes over a promoted phosphate catalyst

1. n nThe vapor-phase hydrolysis of halobenzenes over a phosphate catalyst promoted with cupric chloride was investigated. n n n n n2. n nIt was shown that, as in the presence of silica gel, in the presence of tricalcium phosphate the hydrolysis of chlorobenzene is promoted by cupric chloride. n n n n n3. n nIt was found that the reactivities of halobenzenes in the investigated reaction fall in the same order as in presence of silica gel. n n n n n4. n nThe question of the ratio between total and active surface in silica gel and phosphate catalysts was discussed. The number of active sites in the catalyst was estimated.

Investigation of the vapor-phase hydrolysis of chlorobenzene in presence of a phosphate catalyst

1. n nThe vapor-phase hydrolysis of chlorobenzene in presence of phosphate catalysts was investigated. The activity of a one-component phosphate catalyst in the absence of promoters was confirmed. n n n n n2. n nThe influence of the temperature on the degree of conversion of chlorobenzene and on the selectivity of the reaction was investigated. It was found that the phosphate catalyst has a higher thermal stability than silica gel and is less sensitive to the deactivating action of inorganic impurities. n n n n n3. n nIt is suggested that the mechanisms of vapor-phase hydrolysis are the same in presence of phosphate and silica gel catalysts.

Relation between the macrostructure of aluminum oxide and the activity of nickel-alumina catalysts with various nickel contents

The properties of nickel-alumina catalysts with various nickel contents depend on the nature of the macrostructure of the aluminum oxide. Catalysts on coarsely porous aluminum oxide with 5 and 10% nickel have high and practically identical activities. The activity of a catalyst with 50% nickel is considerably lower. Catalysts on finely porous aluminum oxide with 5, 10, and 30% nickel have a low activity and are unstable.

Catalytic alkylation of isobutane with ethylene under pressure at high temperatures

1. n nIn the presence of aluminum oxide at elevated temperature and pressure, ethylene reacts with isobutane predominantly at the tertiary C atom and, to a lesser extent, at the primary C atom, 2,2-Dimethylbutane and 2-methylpentane are thus formed. n n n n n2. n nNeohexane obtained in the reaction also reacts with ethylene to form 2,2-dimethylhexane, indicating the stepwise nature of the alkylation process. n n n n n3. n nIn the presence of an aluminum oxide catalyst, an olefin (ethylene and propylene) adds to the tertiary C atom of isobutane with more difficulty than to the secondary carbon atom of n-butane.

Kinetics of the catalytic reduction of peroxides and hydroperoxides

1. n nThe kinetics and sequence of the hydrogenation of the bonds in 3-methyl-1-butyne 3-hydroperoxide and p-nitrobenzoyl peroxide were studied. The reaction order, rate constants and activation energy of the given processes were determined. n n n n n2. n nMaking use of the energetics principle of the multiplet theory, it proved possible to predict the hydrogenation sequence of the bonds in bifunctional compounds on a nickel catalyst. The height of the energy barriers for the hydrogenation of various bonds was calculated. n n n n n3. n nIn complete harmony with the multiplet theory, in the case of 3-methyl-1-butyne 3-hydroperoxide the peroxide group is the first to hydrogenate in the presence of a nickel catalyst, and then the acetylenic bond. In the case of p-nitrobenzoyl peroxide, it is the nitro group that hydrogenates first, and only after this does the peroxide group hydrogenate. n n n n n4. n nThe hydrogenation sequence depends on the nature of the catalyst, which is in harmony with the theory. In the presence of Pd-black, for the case of 3-methyl-l-butyne 3-hydroperoxide, it is the acetylenic bond that hydrogenates first, and only after this does the peroxide group hydrogenate. The last to hydrogenate is the ethylene bond. In the presence of Pt-black, strict selectivity is observed only in the hydrogenation of the triple C≡C and double C=C bonds.

Selective hydrogenation of adiponitrile over a cobalt boride catalyst

1. n nCobalt boride has a high activity and high selectivity in the hydrogenation of adiponitrile. Under optimal conditions, the hexamethylenediamine yield is 90–94% and that of secondary amines, not more than 5–10%. n n n n n2. n nThe catalyst retains its selectivity when small amounts of ammonia (∼6 weight %) are used, when the amount of catalyst is increased to 80% and when the reaction temperature is raised to 125–150°. This indicates that on Co2B reaction (1) strongly predominates over the competing reactions (2) and (3), while reactions (4) and (5) hardly occur.

Relation of the activities and stabilities of nickel—alumina catalysts to the macrostructure of the carrier

1. n nThe relation of the activities and stabilities of nickel-alumina catalysts to the character of the macrostructure of the alumina was studied. n n n n n2. n nA particularly high specific surface is not necessary for a carrier of a highly active nickel-alumina catalyst; its dehydrogenating activity is determined mainly by the character of the porosity of the carrier. n n n n n3. n nCatalysts prepared by the deposition of nickel on coarsely porous alumina have high activities and stabilities, but those having a finely porous alumina as carrier have considerably lower activities.