Showing papers on "Dehydrogenation published in 1975"

Production of alkyl aromatic hydrocarbons

Abstract: Alkyl aromatic hydrocarbons useful as chemical raw material, solvents and the like are provided in high purity by hydrocracking of a fraction rich in alkyl aromatics and lean in aliphatic hydrocarbons over a particular zeolite catalyst associated with a hydrogenation/dehydrogenation component. The charge stock is characterized by substantial absence of hydrocarbons lighter than benzene. The technique is particularly well suited to production of maximum xylenes from a fraction containing higher boiling and lower boiling alkyl aromatics.

Fuel gas production

Abstract: A process is described for the production of methane from methanol by catalytic dehydration and dehydrogenation providing a high initial methane yield and a final substitute natural gas product of high calorific value. The catalytic dehydration and dehydrogenation steps may be effected simultaneously or in sequence. High efficiency in usage of raw materials and thermal requirements of the process are secured. A preferred catalyst containing both dehydration and dehydrogenation functions consists essentially of a major amount of iron oxide and minor amounts of chromium oxide and phosphate or tungstate ions.

Continuous paraffin dehydrogenation process

Abstract: Continuous operation and a high rate of conversion are obtained in a normal paraffin dehydrogenation process through the use of a moving bed non-fluidized reaction zone operated at a subatmospheric pressure. Quantities of catalyst are periodically removed from the reaction zone, passed through regeneration and reducing zones operated at superatmospheric pressures and returned to the top of a reaction zone.

Transfer Hydrogenation and Transfer Hydrogenolysis VII. The Mechanism of Hydrogen Transfer from 2-Propanol to Olefins Catalyzed by Dihydridotetrakis(triphenylphosphine)ruthenium(II)

Abstract: The dihydride complex, RuH2(PPh3)4, has been found to be an excellent catalyst for the hydrogen transfer from 2-propanol to olefins. For cyclohexene in toluene solution, the rate law at 80°C was: Rate=\frac0.04[C]_o[D]1+24[P] where [C]0, [D] and [P] are the concentration of the catalyst, 2-propanol and triphenylphosphine, respectively. It is pressumed that active intermediates of the reaction are not Ru(IV)-species but Ru(0)-species. The rate determining step of the reaction is inferred to be the dehydrogenation of 2-propanol, that is, the hydrogen transfer from the alcohol to Ru(0)-complex to form a hydride complex by oxidative addition.

Study of automotive storage of hydrogen using recyclable liquid chemical carriers

Abstract: The catalytic dehydrogenation of naphthenes to their corresponding aromatic compounds was evaluated as a specific non-cryogenic approach for the on-board recovery of hydrogen for use as an automotive fuel. The dehydrogenation of methylcyclohexane (MCH) to toluene was used in this study as representative of the contemplated storage system. Although not evaluated in detail, it was assumed that by-product toluene would be recycled to a central hydrogenation facility to regenerate the MCH. Thus, in principle, MCH would not be consumed, but would act as a hydrogen storage medium. It was concluded, based on literature information, thermodynamic and kinetic analyses, engineering considerations, and cost estimates that this method of hydrogen storage does not compare favorably with gasoline fueled automobiles. Approximately 16 times more volume of MCH than gasoline would be needed for the same mileage range, thus severely curtailing the range of an automobile with a reasonably sized MCH tank. In addition, an unreasonable amount of time (in excess of 20 minutes) would be needed to bring the dehydrogenation catalyst to operating temperature (589/sup 0/K) from a cold start. Other factors that make the system appear unfavorable when compared to present automobiles are excessive system weight, high cost, and general inflexibility. Nomore » detailed comparisons were made of the MCH/hydrogenstorage system with other automotive hydrogen storage systems or other automotive propulsion systems. (auth)« less

Process for preparation of methacrylic acid

Abstract: PURPOSE: Methacrylic acid is prepared in high yield and high selectivity by the oxidative dehydrogenation of isobutyric acid with an oxygen-containing gas in the presence of a catalyst with intermittent addition of the isobutyric acid. COPYRIGHT: (C)1977,JPO&Japio

Method for preparing polyphenyls

Abstract: Polyphenyls including biphenyl and terphenyl, are prepared by hydroalkylation of a charge benzene, dehydrogenation of hydroalkylate, and separation of desired product polyphenyls.

Crosslinked styrene/divinylbenzene network systems

Abstract: Differences in properties of pure metaand pure para-divinylbenzene crosslinked polystyrene and their sulphonated products have been correlated with probable network structural differences. The para-divinylbenzene copolymerizes more slowly than does the meta isomer to give a crosslinked copolymer which swells less, sulphonates less rapidly, and, when sulphonated, gives an ion exchanger which has lower selectivity. It is concluded, on the basis of copolymerization data, that the para crosslinked network is tighter and less uniform than that of the meta crosslinked network. Techniques have been developed for the synthesis, separation and purification by gas chromatography, polymerization, and copolymerization of 99.5_99.9 per cent pure metaand para-divinylbenzenes. Kinetics of the polymerization and copolymerization have been determined by radiocarbon techniques and computer analysis of high-conversion data. The preparation and sulphonation of the bead copolymers of styrene with the pure metaand para-divinylbenzenes have been developed in detail and the exchange isotherms of the sulphonated beads have been evaluated. INTRODUCTION Most ion exchange resins are prepared from styrene/divinylbenzene crosslinked copolymers in bead form by processes that are not usually specified. These processes use for divinylbenzene the commercially available mixture of the metaand para-divinylbenzene isomers. This mixture also contains varying amounts of other ingredients—chiefly metaand para-ethyistyrenes. This ambiguously defined process leads to a network structure that is difficult to obtain reproducibly, and problems are thus added to the usual complications involved in studies of crosslinked polymer systems. In our studies we have obtained data on the properties of pure metaand pure para-divinylbenzenes2'3' 8,142330; on the kinetics of their poiymerization'2'26 and styrene copolymerization4'9' 152O283233; on the characteristics of the copolymers'8' 19,25, 27 and their suiphonation" 13, 16, 18,21,24; and some data on their suiphonated products" 10, 31, Some related data have been obtained for ort.ho-divinylbenzene, 1,2,4and 1,3,5trivinylbenzenes, and a series of divinyl compounds of the type CH2 CHC6H4—X—C6H4CHCH21'6"7'20'22 57 RICHARD H. WILEY The questions for which we have sought answers are: (1) what kind of data establish a difference between the meta and the para crosslinked systems and (2) what are the structural implications available from such differentiations? It is the extent to which we can provide answers to these questions that we wish to consider in this report. D1V1NYLBENZENE MONOMERS The commercially available divinylbenzene is a complex mixture of 8—12 components. It is made by dehydrogenation of diethylbenzenes, in turn obtained by Friedel—Crafts alkylation of benzene with ethylene. The ethylbenzenes are a mixture of ortho, para and meta isomers. The ortho isomer is converted to naphthalene in the dehydrogenation and there is little to be gained in separating the ethylbenzenes prior to dehydrogenation, as the dehydrogenation catalyst re-equilibrates the isomeric mixture. One dehydrogenation process has been operated using an iodine catalyst which does not equilibrate the isomeric mixture, and during the time of its development relatively pure metaand para-divinylbenzenes were available. Also, a process23 for the separation of the divinyl isomers based on a Werner complex formation was at one time operated on a developmental basis. We have reported analytical gas chromatographic data for commercial divinylbenzene samples. Typical data are given in Figure 1. A complete listing of the components as identified by comparisons with retention times of known mixtures is given in Table 1. It is essential, for the purposes of establishing possible differences in the network systems obtained on copolymerization, that the pure meta and para isomers of divinylbenzene be separated and purified. The methods we have developed for this purpose are based on preparative gas chromatography (° _____________________________________

Dehydrogenation process and catalyst

Abstract: Magnesium chromite dehydrogenation catalyst are improved by preparation in oxygen deficient or essentially inert calcination atmospheres and in the presense of halogen, either singularly or in combination.

The Dehydration and Dehydrogenation of Ethanol Catalyzed by TiO2–ZrO2

Abstract: Ethanol was converted into ether, ethylene, and butadiene over TiO2–ZrO2 with various contents of ZrO2in a flow system. Maximum acidity and activity were obtained at 50% ZrO2. The butadiene formation was explained by both dehydration and dehydrogenation reactions on acidic and basic sites, implying that TiO2–ZrO2 is an acid-base bifunctional catalyst.

Dehydrogenation of paraffins

Abstract: A process for the dehydrogenation of paraffinic hydrocarbons containing from 3 to 6 carbon atoms to the corresponding monoolefin, wherein the process is carried out in the vapor phase, in the presence of oxygen and in the presence of an improved oxidative dehydrogenation catalyst containing cobalt and molybdenum.

Competition of the Two Reaction Mechanisms of Maleic Anhydride Formation in Vapor-Phase Oxidation of Butadiene over Supported Molybdena Catalysts

Abstract: Vapor-phase oxidation of butadiene, 2,5-dihydrofuran and furan over supported molybdena catalysts has been investigated with reference to the reaction mechanism and the rate-determining step of maleic anhydride formation from butadiene. Formation of maleic anhydride during the oxidation of butadiene was found to follow two reaction mechanisms, (a) via 2,5-dihydrofuran and furan, and (b) via 2,5-dihydrofuran but not via furan. The energy barrier for the addition of oxygen species to adsorbed butadiene or furan is very high, i.e., 28.9 or 21.9kcal/g-mol, respectively, as compared to that for the oxidative dehydrogenation of the intermediate compounds such as 2,5-dihydrofuran. Formation of 2,5-dihydrofuran is rate-determining in these mechanisms during the oxidation of butadiene to maleic anhydride. The second mechanism plays a more important role in maleic anhydride formation at low temperatures, the role of the first mechanism increasing with a rise in the reaction temperature.

Oxidative dehydrogenation of alcohols to aldehydes and ketones

Abstract: Monohydric primary or secondary saturated and unsaturated alcohols are oxidatively dehydrogenated to the corresponding aldehyde or ketone over a gold catalyst at temperatures between 280°-600° C. in the presence of oxygen.

Dye-sensitized photooxidation of some substituted 1,3-Diphenyl-2-pyrazolines

Abstract: 1,3-Diphenyl-2-pyrazolines substituted in the 4- and 5-positions with phenyl groups undergo dye-sensitized photooxidation at widely different rates depending on the substitution pattern. Depending on both the solvent and the substitution pattern, two types of reaction are usually observed: (a) dehydrogenation to the corresponding pyrazole and (b) incorporation of oxygen with ring opening to yield carbonyl compounds.

Mechanism of the dehydrogenation of formic acid by iridium and rhodium complexes

Abstract: The homogeneous catalytic process HCOOH→H2+CO2 has been studied in the presence of carbonyl-free phosphine complexes of iridium (I) and (III), and rhodium (I) The rupture of the C−H bond has been found to be the rate-determining step The halide ion and phosphine are first substituted by formate ion in the cordination sphere of the metal The reaction mechanism and its peculiarities are discussed