Hiromi Matsuhashi

Skeletal isomerization mechanism of alkanes over solid superacid of sulfated zirconia

Abstract Skeletal isomerizations of n-butane and n-pentane were performed over solid superacids of sulfated zirconia and Pt-promoted sulfated zirconia. Changes in apparent activation energy and product selectivity were observed during the reactions. Isomerization proceeded by a monomolecular mechanism on Lewis acid sites in the initial period; then it changed to a bimolecular mechanism on Bronsted acid sites by forming surface alkenes. By addition of hydrocarbons or hydrogen, the monomolecular reaction became predominant. n-Pentane was converted into isopentane with very high selectivity. The overall mechanism of acid-catalyzed skeletal isomerization of alkanes is discussed.

Solid catalyst treated with anion: XIX. Synthesis of the solid superacid catalyst of tin oxide treated with sulfate ion

Abstract A solid superacid catalyst with an acid strength of Ho ⩽ −16.04 was synthesized from tin hydroxide, which was obtained from the solution of pH 10, by exposing to 3 M H 2 SO 4 followed by calcination in air at 823 K; the catalyst, SO 2- 4 /SnO 2 , was active for the skeletal isomerization of butane to isobutane at room temperature. The specific surface area of SO 2- 4 /SnO 2 was much larger than that of SnO 2 without the sulfate treatment; by X-ray diffraction (XRD) analysis the degree of crystallization of the former material was much lower than that of the latter. Infrared (IR) spectra showed the catalyst to possess a bidentate sulfate ion coordinated to the metal. The present superacid showed the catalytic action of oxidation at elevated temperatures of >450 K; acetaldehyde and acetone were obtained as products from the hydration of ethene, and high selectivity of >95% for the formation of cyclohexanone from cyclohexanol was observed in the presence of water.

Determination of acid strength of solid superacids by temperature programmed desorption using pyridine

Acid strength of solid superacids was determined by temperature programmed desorption using pyridine. An approximately linear relationship exists between the acid strengths of solid acids determined by the Hammett method and the termination temperature of pyridine desorption. The acid strength of colored superacids versus temperature relationships practically fell on the linear line.

Activity enhancement of mesoporous silica (FSM-16) by modification with iron (II) sulphate for the isomerization of 1-butene

Abstract The catalytic activity of mesoporous silica (FSM-16) for the isomerization of 1-butene was remarkably enhanced by modification with iron (II) sulphate. The enhancement of the activity of FSM-16 was attributed to the transformation of the silanol groups on FSM-16 into Bronsted acid sites by the inductive effect of FeSO4 and/or sulphate species formed by the decomposition of FeSO4.

Measurement of the relative acid strength and acid amount of solid acids by argon adsorption

The relative acid strength and the number of acid sites of solid acids exhibiting high surface acidity have been determined from argon adsorption isotherms using Langmuirs equation in the temperature range T = 203–243 K and Henrys equation in the temperature range T = 233–313 K. The heat of Ar adsorption from Langmuirs equation was −14.9, −15.6, −17.9, −17.7, −17.1, −26.3, −29.6, −21.4, and −21.6 kJ mol−1 for silica–alumina, H–Y, H–ZSM–5, H–-MOR, and H–Beta zeolites, sulfated ZrO2, sulfated SnO2, tungstated ZrO2, and Pt-loaded tungstated ZrO2, respectively. The corresponding values of saturated adsorption amount were 0.35, 0.35, 0.37, 1.44, 0.10, 0.009, 0.10, 0.04, and 0.07 mmol g−1, respectively. The heat of Ar adsorption from Henrys equation was −14.4, −14.8, −17.3, −17.3, −18.9, −22.4, and −23.5 kJ mol−1 for silica–alumina, H–Y, H–ZSM–5, and H–MOR zeolites, sulfated Fe2O3, sulfated ZrO2, and sulfated SnO2, respectively. The order of the magnitude of heat for silica–alumina, the zeolites, and for the sulfated ZrO2 agree with those evaluated using Ar–TPD and NH3–TPD, and coincide with the values of the heat of adsorption of NH3. The saturated adsorption amounts for H–ZSM–5 and H–MOR are equal to the Al content, which generates acid sites, and approximate to the values for NH3 adsorption reported in the literatures.

Solid catalysts treated with anions: XXI. Zirconia-supported chromium catalyst for dehydrocyclization of hexane to benzene

Abstract A dehydrogenation catalyst for alkanes was obtained by immersing Zr(OH)4 in 0.05M (NH4)2CrO4, followed by calcination in air at 600–800°C and reduction at 550°C (0.5 wt.-% Cr). This catalyst converted hexane into benzene with a selectivity of up to 89% under pulse conditions, and the yield of benzene at 550° C was steady up to 6 h with 76% selectivity in a flow system at atmospheric pressure. HfO2 was also effective as a support, but Al2O3, SiO2, TiO2, and SnO2 were not. Measurements of ESR and XPS showed the ZrO2 catalyst to be CrIII-CrIV, created by reduction of CrO42−/ZrO2.

Catalytic activities of metal oxides containing iron for hydrocracking coal model compounds and Taiheiyo coal

Abstract Twenty-five catalysts of metal oxides principally containing iron were prepared and examined in hydrocracking of coal model compounds: diphenyl ether, diphenylmethane and benzyl phenyl ether. Highly active catalysts were Fe 2 O 3 -I and -II and FE 2 O 3 TiO 2 for diphenyl ether, Fe 2 O 3 -I and -II and Fe 2 O 3 SiO 2 for diphenylmethane, and sulfated Fe 2 O 3 -I, -II and -III and Fe 2 O 3 TiO 2 together with WO 3 /ZrO 2 for benzyl phenyl ether. The best method for preparation of iron oxide was precipitation of the hydroxide from the nitrate with ammonia followed by calcination. The catalysts were tested for the liquefaction of Taiheiyo coal using a high-pressure d.t.a. apparatus; sulfated Fe 2 O 3 TiO 2 was most effective, and the order of activity was similar to that for benzyl phenyl ether. From the results of hydrocracking of model compounds and liquefaction of Taiheiyo coal, both CC and CO bond cleavages are discussed on the basis of acid property and hydorgenation ability of the catalysts.

3.1 Synthesis of Solid Superacid of Borate Supported on Zirconium Oxides

Abstract A solid superacid catalyst was synthesized from hydrated zirconium oxide and boric acid, the latter having quite low acidity. The results of ethanol decomposition revealed that B 2 O 3 /ZrO 2 catalyst, containing 60 mol% B atom and calcined at 673 K, has superacidity. The acid strength was estimated to be closed to Ho=-13 by TPD experiment. The results of IR and XPS show that three coordinated B atoms pull the electron from oxygen of ZrO 2 and the negative charge on B atom is diffused into B 2 O 3 bulk by the resonance which occurs between the lone pair of oxygen and the empty orbital of B. The structure of active site was discussed.

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.

Synthesis of solid superacid of silica treated with sulfuryl chloride

A solid superacid catalyst was synthesized from silica gel, which was obtained from the decomposition of Si(OC2H5)4 with HNO3 solution, by exposing to SO2Cl2 followed by calcination in air at 673 K. The catalytic activity for ethanol decomposition was higher than that of SiO2-Al2O3.