Reactions Of Methylcyclohexane Research Articles

Chemically synthesized hydrogen fuel from reaction of methylcyclohexane over nanoporous heterogeneous catalysts

ABSTRACT Nanoporous oxides have been prepared, as hosts for the encapsulation of metal nanoparticles, and tested for the catalytic decomposition of methylcyclohexane (MCH) to produce hydrogen gas as a potential fuel source. The aim of the work is to test a range of mixed metal nanoparticle catalysts in the MCH to hydrogen reaction. The work investigates the use of a range of inexpensive metals in conjunction with traditional precious metal e.g. Pt. The objectives of work are prepared nanoporous oxides, comprising MCM- and SBA-types using established methods. Encapsulated metal nanoparticles within the pores of nanoporous oxide. Catalysts have been characterized fully to confirm porosity, surface area, and nanoparticle dispersion. The activity of catalytic of the various nanoporous materials was determined in the MCH to hydrogen reaction, and kinetic models developed from the associated experimental findings.

Influence of the Brønsted acidity, SiO2/Al2O3 ratio and Rh–Pd content on the ring opening. Part II. Selective ring opening of methylcyclohexane

Monometallic and bimetallic Pd–Rh catalysts with various Rh/Pd atomic ratios (=0.5, 1 and 2) and a total metal charge of 1wt% supported on SiO2–Al2O3 (SIRAL 40, 20, 5) were studied for the ring opening of methylcyclohexane (MCH). The results were compared with those obtained previously for ring opening of decalin. It was found that the total acidity and the Brønsted acidity of the support have a higher influence on the activity for ring opening of naphthenic bicycles than on the activity for opening single rings. The influence of the metal charge is more important on the reaction of MCH. All the catalysts display a high MCH conversion, which increases with the reaction temperature. The bimetallic catalyst with the Rh/Pd ratio equal to 2 and supported on SIRAL 40 has the highest yield to ring opening products.

Isomerization of cycloheptane, cyclooctane, and cyclodecane catalyzed by sulfated zirconia—comparison with open-chain alkanes

The skeletal isomerization of cycloalkanes with the number of carbons greater than six, cycloheptane, cyclooctane, cyclodecane, and cyclododecane, was performed over sulfated zirconia in liquid phase at 50°C. A main product of methylcyclohexane was formed from cycloheptane via a protonated cyclopropane intermediate, protonated [4.1.0]bicycloheptane, together with small amounts of trans-1,2-dimethylcyclopentane, cis- and trans-1,3-dimethylcyclopentanes, 1,1-dimethylcyclopentane, and ethylcyclopentane. A major product from cyclooctane was ethylcyclohexane via a protonated cyclobutane intermediate, protonated [4.2.0]bicyclooctane, followed by cis-1,3-dimethylcyclohexane in addition to small amounts of trans-1,2-, -1,3-, -1,4-dimethylcyclohexanes, 1,1-dimethylcyclohexane, and methylcycloheptane. The detailed reaction-paths for cycloheptane and cyclooctane were shown after additional examinations in reactions of methylcyclohexane, ethylcyclopentane, ethylcyclohexane, and 1,2-dimethylcyclohexane. Cyclodecane was dehydrogenated into cis- or trans-decaline with the evolution of a dihydrogen. Cyclododecane was converted into lots of products, more than 30 species.

COMPARATIVE REACTION STUDY OF METHYLCYCLOHEXANE AND 3-METHYLHEXANE IN H2 AND N2 ON Pt/Al2O3 CATALYST

ABSTRACT The reaction of methylcyclohexane and 3-methylhexane were studied in a pulse microcatalytic reactor using H2 and N2 carriers on Pt/Al2O3 catalyst at temperatures from 350 to 500°C, contact times (W/F) of 1.25 × 10−3–3.75 × 10−3 g min/ml and a total pressure of 4.0 kg/cm2. In N2, there was complete conversion of methylcyclohexane to methane, benzene and toluene while similar products were produced for 3-methylhexane, albeit with diminished conversion level. In H2, methane was produced from 3-methylhexane conversion while aromatization without demethylation was obtained in addition to some cracking for methylcyclohexane at the low temperature range (350–400°C); a higher temperature range (460–500°C) resulted in complete fragmentation for methylcyclohexane. In H2–N2 mixtures, the presence of N2 of not less than 50% in the carrier gas stream yielded an aromatic catalyst at conditions where only cracking activity was previously evident. The differences in product distribution and/or product types for the two reactants in H2 and N2 suggest a different reaction mechanism for both reactants.

ChemInform Abstract: Catalytic Reactions of Cyclooctane and Ethylcyclohexane on HY Zeolite

Few systematic studies of the reactions of cycloparaffins on zeolites have been reported, considering their importance as a component of commercial crude feedstocks. Studies of small ring (C/sub 3/, C/sub 4/) cycloparaffins have shown that the primary reaction product is the corresponding olefin. It has not been established, however, that the corresponding olefin is produced as an initial product of the cracking of medium-sized (C/sub 5/, C/sub 6/) rings. Studies of cycloparaffin cracking on silica-alumina catalysts report that the degree of saturation of low-molecular-weight products is much greater than that observed in comparable n-paraffin cracking. Reactions of methylcyclohexane on HY zeolite at 450/sup 0/C have shown that dehydrogenation, isomerization, and cracking are all primary processes. Here the authors report product distributions in the cracking of ethylcyclohexane and cyclooctane on HY zeolite at 400/sup 0/C and compare product distributions for these cycloparaffins. 19 references.

Reactions of methylcyclohexane and n-heptane over supported Pt and PtRe catalysts

Reactions of methylcyclohexane (MCH) and n-heptane were compared, using industrial Pt Al 2O 3 or PtRe Al 2O 3 catalysts. Although the same products were generally observed, product selectivity and rate of catalyst deactivation differed substantially for the two reactants. With n-heptane, greater amounts of light cracked products (C 1C 5), heavy alkylated aromatics, and coke were produced. With n-heptane the total aromatic yield (benzene + toluene yields) was substantially less and the decline in the total aromatic yield during the first feed cycle was in general much greater. Selectivity for aromatic products immediately following hydrogen treatment of the coked PtRe catalysts was less with MCH than with n-heptane. Presulfiding the Pt catalyst slightly poisoned the dehydrogenation and dehydrocyclization activities. However, the presulfided PtRe Al 2O 3 catalyst was very selective for these reactions and a high total aromatic yield was observed with either MCH or n-heptane. Sulfur quenched hydrogenolysis, demethylation, and reactions which form alkylated aromatics of higher molecular weight than toluene.

Catalytic reactions of cyclooctane and ethylcyclohexane on HY zeolite

Few systematic studies of the reactions of cycloparaffins on zeolites have been reported, considering their importance as a component of commercial crude feedstocks. Studies of small ring (C/sub 3/, C/sub 4/) cycloparaffins have shown that the primary reaction product is the corresponding olefin. It has not been established, however, that the corresponding olefin is produced as an initial product of the cracking of medium-sized (C/sub 5/, C/sub 6/) rings. Studies of cycloparaffin cracking on silica-alumina catalysts report that the degree of saturation of low-molecular-weight products is much greater than that observed in comparable n-paraffin cracking. Reactions of methylcyclohexane on HY zeolite at 450/sup 0/C have shown that dehydrogenation, isomerization, and cracking are all primary processes. Here the authors report product distributions in the cracking of ethylcyclohexane and cyclooctane on HY zeolite at 400/sup 0/C and compare product distributions for these cycloparaffins. 19 references.

Demethylation of methylcyclohexane in contact with nickel catalysts under hydrogen pressure

1. The catalytic demethylation of methylcyclohexane on nickel catalysts in a continuous system under a hydrogen pressure of 20 atm. and at 330–360° has been investigated. 2. The most effective catalyst for this reaction is the nickel-aluminum oxide catalyst obtained after a preliminary treatment of the carrier with hydrofluoric acid. The yield of cyclohexane treated on this catalyst is 30.1% per cycle, as calculated on the basis of the methylcyclohexane which has reacted. 3. The demethylation reaction of methylcyclohexane on nickel catalysts is somewhat complicated by the isomerization of a part of the cyclohexane produced to methylcyclopentane, with a subsequent hydrogenolysis of the latter, alkanes being formed.

Some problems in the mechanism of methylcyclohexane conversions over nickel-alum ina catalyst at a high hydrogen pressure

1. An investigation was made of the conversions of cyclohexane, methylcyclopentane, and toluene in the presence of a Ni-Al2O3 catalyst at 360° (20 atm), a molar ratio of hydrogen to hydrocarbon of 4 ∶ 1, and a space velocity of 0.2 hr−1. 2. Under these conditions of catalytic hydrogenolysis of the side group, there were certain side reactions of methylcyclohexane involving contraction of the six-membered to a five-membered ring and partial hydrogenolysis of both the five-membered and six-membered rings.

High-temperature reactions of methylcyclohexane in a continous-flow system in presence of metals of the palladium group and of hydrogen at high pressure

1. An investigation was made of the catalytic properties of finely dispersed platinum, palladium, rhodium, and ruthenium deposited on alumina and on silica gel in the transformations of methylcyclohexane at 460° in presence of hydrogen at 20, 35, and 50 atm in a flow system. 2. It was shown that at 460° and in presence of hydrogen at 20 atm the main reaction of methylcyclohexane is dehydrogenation to toluene. The extent of the dehydrogenation of the original hydrocarbon depends both on the nature of the metal and on the chemical nature of the carrier. 3. It was shown that under the given conditions dehydrogenation is accompanied by isomerization processes with formation of isomer dimethylcyclopentanes and also by the demethylation and methylation of hydrocarbons with participation of methylene radicals. 4. With increase in pressure, other conditions being maintained constant, there is an increase also in the extent to which methylcyclohexane undergoes isomerization with contraction of the ring. 5. Study of the behavior of methylcyclohexane in contact with silica and alumina showed that these oxiden promote partial isomerization of the original hydrocarbon into dimethylcyclopentanes.

Reactions of methylcyclohexane and toluene in contact with aluminum chloride

1. A study has been made of the reactions of methylcyclohexane in the liquid phase in presence of anhydrous aluminum chloride at 80° under normal pressure. 2. It has been established that when methylcyclohexane reacts with aluminum chloride under these conditions it not only isomerizes with shrinkage of the ring into dimethylcyclopentane, but also undergoes the process of methyl-group redistribution to a small extent and, as a result, dimethylcyclohexane and cyclohexane are formed. 3. It has been shown that in the reaction of aluminum chloride with toluene under analogous conditions there is a redistribution of methyl groups resulting in the formation of benzene and a mixture of isomeric xylenes.