Yoshiro Morita

Disproportionation of 1,2,4-trimethylbenzene over montmorillonite pillared by aluminium oxide

Abstract Disproportionation of 1,2,4-trimethylbenzene was investigated in a flow system at 200°C, using montmorillonite intercalated by aluminium chlorohydroxyl complex (Al-mont) as a catalyst. Calcination of the Al-mont at 4000C gave an interlayer spacing of 8.5 A. The Al-mont catalyst was selective for disproportionation to yield 1,2,4, 5-tetramethylbenzene (durene) and xylenes. o-Xylene was produced far more abundantly than expected from thermodynamical equilibrium. A mechanistic consideration suggested that the preferential formation of 1,2,4,5-tetramethylbenzene and o-xylene was a result of restricted transition state selectivity. The catalytic activity decreased with time on stream owing to coke deposition. The catalyst deactivation was, however, prevented by supporting a small amount of Pd on the catalyst and using H 2 as a carrier gas, probably as a result of hydrogen spill-over.

Hydrogenolysis and isomerization of n-pentane on group VIII transition metals

Abstract The reaction of n -pentane in the presence of hydrogen was studied using supported Group VIII transition metals as catalyst. The specific activity for hydrogenolysis referred to unit surface area of the metal was examined and the following sequence was obtained: Ru > Rh > Pt > Ni > Co > Ir > Pd ~ Fe. Hydrogenolysis on nickel proceeded via successive demethylation at the terminal carbon-carbon bond of adsorbed hydrocarbon, whereas on cobalt and iron, the desorption step of surface residues was so slow that the exact mode of hydrogenolysis could not be determined. On Group VIII noble metals, all the carbon-carbon bonds of n -pentane cracked almost statistically. On ruthenium, rhodium, and iridium, multiple bond breaking (extensive degradation) occurred at low partial pressure of hydrogen, although at high partial pressure of hydrogen, the amounts of methane and ethane were equal, respectively, to those of butane and propane. The main features of the product distributions of hydrogenolysis on palladium and on platinum catalysts could be accounted for by assuming that only one carbon-carbon bond was ruptured at the residence of a molecule on the surface. Carbon-supported catalysts produced methane and butane in higher proportion than silica gel supported catalysts. Among all the Group VIII transition metals with the exception of osmium, only palladium and platinum were found to be active for isomerization of n -pentane to isopentane. The selectivity of platinum for isomerization was found to decrease with increasing partial pressure of hydrogen.

Conversion of trimethylbenzenes over montmorillonites pillared by aluminium and zirconium oxides

Abstract On the pillared clays and H-Y catalysts, the reactivity of TrMB isomers decreased with increasing cross-sectional diameter. Especially on montmorillonite intercalated by aluminium oxide (Al-mont-2) of which the layer distance was 5.4 A(0.54nm), there was a remarkable difference in reactivity between the smallest 1,2,4-TrMB and other isomers. Pillared clays showed higher selectivity for disproportionation against isomerization of every TrMB isomers than H-Y. The selectivity of pillared clays was unaccountable on a basis of the interlayer spacing: montmorillonite intercalated by zirconium oxide (Zr-mont) of which the layer distance was 7.1 A and the Al-mont-2 showed higher disproportionation selectivity than an Al-mont-1 having layer distance of 8.5 A, probably due to the difference in acidic property. There was no appreciable difference in the distribution of products for disproportionation of 1,2,3- and 1,3,5-TrMB over the catalysts tested. On the other hand, 1,2,4,5-TeMB and o-xylene were the main products from 1,2,4-TrMB and the selectivity to these products depended on the type of catalysts to decrease in the order: Al-mont-2 >Zr-mont > Al-mont-1 > H-Y. A mechanistic consideration suggests that the preferential formation of 1,2,4,5-TeMB and o-xylene is due to the restricted transition state selectivity.

The reaction of n-heptane on rhodium catalysts in the presence of steam

Abstract The catalytic activities of rhodium supported on γ-alumina for steam reforming and dehydrocyclization (aromatization) have been investigated as a function of the degree of dispersion of rhodium. The state of dispersion of rhodium was characterized by measurements of hydrogen and carbon monoxide chemisorption. The specific catalytic activity expressed by the initial rate at 550 °C per unit surface area of rhodium was found to depend on the degree of dispersion of rhodium. It was suggested that the steam reforming activity was associated with surface atoms existing in crystal faces and the aromatization activity with edge atoms.

Catalytic synthesis of hydrocarbons from carbon monoxide and hydrogen on lamellar compound of graphite intercalated by ferric chloride

From the thermal gravimetric studies of a lamellar compound of graphite (LCG) intercalated by ferric chloride, it was shown that FeCl/sub 3/ in the intercalated layers was reduced to FeCl/sub 2/ and partly to metallic Fe in flowing H/sub 2/ at 400/sup 0/C; The main constituent in the LCG treated in H/sub 2/ for 1 hr was FeCl/sub 2/, and with an increasing period of H/sub 2/ treatment some part of the FeCl/sub 2/ was further reduced to metallic Fe between the graphite layers. The catalytic activity and selectivity of the reduced LCG for hydrocarbon synthesis from CO and H/sub 2/ were investigated at 300 to 500/sup 0/C and 1 to 20 atm. The catalytic activity of the LCG increased with increasing degree of reduction of the FeCl/sub 2/, suggesting that the activity is attributed to metallic Fe. The main reaction products were C/sub 1/--C/sub 4/ hydrocarbons and the formation of higher hydrocarbons or organic oxygenated compounds was negligible. The LCG catalyst gave hydrocarbons in outstandingly high selectivity (more than 90% at 400/sup 0/C) compared with an Fe catalyst merely supported on graphite which gave considerable amount of CO/sub 2/ with hydrocarbons.

Hydrogenolysis of n-pentane on nickel catalyst

Abstract The reaction of normal pentane and hydrogen on a nickel-silica gel catalyst was studied in a flow system under a hydrogen pressure of less than 50 atm. Under the range of temperatures studied (300–400 °C), the predominant reaction was the consecutive removal of terminal methyl groups as methane, and the formation of hydrocarbons containing one less carbon atom. The product distributions varied widely with both variation of the partial pressure of hydrogen and with the reaction temperature. At high partial pressures of hydrogen or low temperatures mainly butane and corresponding amounts of methane were produced. At low partial pressures of hydrogen or high temperatures the pentane was more extensively degraded. Velocity of pentane hydrogenolysis increased with partial pressure of pentane and was inversely proportional to partial pressure of H 2 . The results could be explained by the mechanism involving cracking of terminal carbon-carbon bonds of adsorbed hydrocarbon radicals.

Fischer-tropsch synthesis of hydrocarbons on V2O3-supported ruthenium catalysts

Abstract Hydrogenation of carbon monoxide was studied using ruthenium catalysts supported on various transition metal oxides. Among them, V 2 O 3 -supported catalysts exhibit particular properties relative to Al 2 O 3 - or other supported ruthenium catalysts in the following ways; i) significantly high turnover frequency based on hydrogen chemisorption, ii) product distribution shifted to heavier molecular weight hydrocarbons, iii) relatively high unsaturate/saturate ratio.

Reaction of 1,2,4-trimethylbenzene and methanol on montmorillonite catalysts pillared by aluminium hydroxyl complexes

Abstract Reaction of 1,2,4-trimethylbenzene (TrMB) and methanol was investigated using montmorillonite catalysts pillared by aluminium hydroxyl complexes (Al-mont) in comparison with H-Y and H-mordenite zeolites. It was found that Al-mont catalysts were activated by water produced from methanol but deactivation of catalysts was accelerated by the presence of methanol. The yield and the fraction of 1,2,4,5-tetramethylbenzene (TeMB) produced from the reaction of 1,2,4-TrMB and methanol on Al-monts were greater than those on H-Y because of the difference in microporous structure. The fraction of 1,2,4,5-TeMB decreased with increasing 1,2,4-TrMB conversion in the absence of methanol but it was suppressed in the presence of methanol, which retarded the isomerization of 1,2,4,5-TeMB on all catalysts. On Al-mont catalysts the fraction of 1,2,4,5-TeMB increased with increasing methanol content in the feed but H-Y catalyst did not show a similar effect of methanol content.

The catalytic activity of the zeolite-hydrogen chloride system

Abstract The catalytic action of the zeolite-hydrogen chloride system in cumene cracking was investigated using a flow apparatus. Though sodium faujasite (Linde Y) was completely inactive for the reaction at temperatures ranging from 250 ° to 350 °C, its activity was reversibly induced by the introduction of hydrogen chloride to the reaction system. Assuming the Langmuir adsorption of hydrogen chloride on zeolite in the reaction system, the reaction rate of cumene cracking was proportional to the coverage of hydrogen chloride. The hydrogen chloride effect on calcium faujasite could be treated in a similar manner to the case of sodium faujasite. The activation energy by the former was about two-thirds of that by the latter.

Supported alkali catalysts for steam gasification of carbonaceous residues from petroleum

Abstract Steam reforming of petroleum residues was investigated at 1173 K and atmospheric pressure in a fluidized-bed flow system using a series of alumina-supported catalysts of alkali metal compounds. The catalytic activity increased with decreasing ionization potential of the catalytic alkali metals: Cs >; K >Na >Li. Catalysis was elucidated in terms of an oxygen transfer mechanism proposed for the catalysis by alkali metal compounds in graphite-or char-steam reaction.