Eisuke Ogata

Effects of iron catalyst precursors, sulfur, hydrogen pressure and solvent type on the hydrocracking of di(1-naphthyl)methane

The effects of various iron catalysts, elemental sulfur, hydrogen pressure and solvents on the hydrocracking of di(1-naphthyl)methane (DNM) were investigated under different conditions. The activities of the iron catalysts were affected by their physical and chemical properties such as surface area and reduced state. The addition of sulfur resulted in a marked increase in DNM conversion at 430 °C. However, at 300 °C the addition of sulfur had a deleterious effect on DNM hydrogenation but a promotional effect on DNM hydrocracking, and Fe and FeS2 catalysed DNM hydrogenation/hydrocracking by substantially different mechanisms. FeS2-catalysed hydrocracking of DNM was retarded by aromatic solvents.

Advances in the study of hydrogen transfer to model compounds for coal liquefaction

The advances in the study of hydrogen transfer to model compounds for coal liquefaction are reviewed. The results from many model reactions indicate that molecular hydrogen promotes thermolysis, hydrogenation, and hydrocracking of model compounds, whereas hydrogen-donating solvents inhibit the reactions. Unlike metallic catalysts such as Fe, Pd, and Ni, their sulfides catalyze radical hydrogen transfer to model compounds. The reactivities of model compounds toward hydrocracking depend not only on their hydrogen-accepting abilities, but also on their adsorption strength on catalyst surface and the stabilities of the resulting leaving groups.

The effect of oxidation state of tungsten on hydrocracking of n-heptane over tungsten oxide

Hydrocracking of n-heptane was investigated with tungsten oxide of various oxidation states under high pressure of hydrogen. It was found that the reaction products definitely change four times with changing oxidation state during the course of reduction of tungsten trioxide. In the presence of slightly reduced tungsten oxide WO3 − a (WO2.84, tungsten oxide reduced at 445 °C), isomerization and subsequent central cracking of n-heptane occurred predominantly, showing that the reaction proceeded by carbonium ion mechanism. As the oxidation state approaches tungsten oxide WO3 − b (WO2 or WO2 + α tungsten oxide reduced at 500 °C to 525 °C), demethylation reaction to form methane and normal paraffins by the selective scission of terminal CC bond took place predominantly. Further reduced tungsten oxide WO3 − c (WO2 − β, tungsten oxide reduced at 580–610 °C) gave isomerized heptane and central cracked products as in the case of WO3 − a. Tungsten oxide WO3 − d reduced almost to tungsten metal above 680 °C again favors demethylation rather than isomerization and central cracking. These results suggest that the oxidation state of tungsten determined the reaction mechanism of hydrocracking of n-heptane.

Thermal cracking of coal model diaryl ethers in aromatic solvent

Abstract Thermal cracking of nine diaryl ethers in a hydrogen donor solvent or 1-methylnaphthalene was studied kinetically. The rate of conversion of the diaryl ethers was first order with respect to the substrate concentration and increased with increase in size of the aryl structure. The relative rate constant of aryloxygen bond cleavage calculated on the basis of first order reaction has indicated that the ease of cracking depends strongly on the aromatic structure and the position of substitution. The conversion rate of 2, 2′-dinaphthyl ether was remarkably enhanced in the presence of hydrogen donor solvent, for example by a factor of ten in the presence of 9, 10-dihydroanthracene. The activation energy of thermal conversion of 2, 2′-dinaphthyl ether was 214 kJ/mole in methylnaphthalene, 151 kJ/mole in tetralin and 88 kJ/mole in dihydroanthracene. The enhancing effect of the hydrogen donor was considered due to hydrogen transfer to the aromatic nucleus of the diaryl ether from the hydrogen donor and successive fast decomposition of hydrogenated ethers.

Thermal decomposition and hydrocracking of hydrogenated di(1-naphthyl)methanes

Abstract The thermal decomposition and hydrocracking of di(1-naphthyl)methane (DNM) and its hydro-derivatives (H-DNMs) were investigated to evaluate the effect of hydrogenation of aromatic rings on the reactivities of the H-DNMs toward thermal decomposition and hydrocracking. In the presence of FeS 2 catalyst and H 2 , DNM rapidly decomposes to naphthalene and 1-methylnaphthalene, even at 300°C, and it seems that the more deeply they are hydrogenated, the more slowly the hydro-derivatives decompose. Without the catalyst or H 2 , however, the reactivities of DNM and H-DNMs toward thermal decomposition appear to be reversed except for di(1-decalyl)methane (20H-DNM), which shows almost no decomposition even at 400°C, independent of the presence of the catalyst and H 2 in the reaction system.

Catalysis of iron sulfates on hydroconversion of 1-methylnaphthalene

Abstract In order to develop suitable catalyst for hydroconversion of heavy hydrocarbon materials, possibility of high quality catalyst production from iron sulfates was pursued on the hydroconversion of 1-methylnaphthalene (1-MN). Catalytic activities of iron sulfates were very low in the absence of sulfur (S). Hydrogenation activity of ferrous sulfate dramatically increased with addition of S. Activity of ferric sulfate, however, did not increase with addition of S. From XRD analysis of catalysts recovered after the reaction, it indicated that ferrous sulfate was transformed to pyrrhotites Fe 1− x S above 350°C in the presence of enough S. But ferric sulfate was not transformed to pyrrhotites easily. Effect of reaction temperature and additive effects of S, presulfiding temperature and sulfuric acid to the activity, selectivity and structure of iron sulfates were investigated in detail. From results of 1-MN hydroconversion, ferrous sulfate is revealed one of useful catalyst precursors for hydrogenation of aromatic hydrocarbon.

Deactivation of pyrite FeS2 catalyst with oxidation and its reactivation

Publisher Summary This chapter discusses the catalysis of iron sulfide catalyst, which is affected by the sulfursulfursulfur to iron (S/Fe) ratio, the activity increased with pyrrhotite formation and accelerated by the presence of excess sulfur. Activity of pyrite for phenanthrene hydrogenation and activity of natural ground pyrites for coal liquefaction decreased with storage under air. The NEDOL process of a coal liquefaction pilot plant of 150 t/d uses pyrites as one of the catalysts for the first stage, because iron sulphide (FeS 2 ) has high activity and is low in price. The relationship between the oxidation of pyrite and the activity and selectivity for the hydrogenation of 1-methylnaphthalene is discussed in the chapter. Effects of the oxidation of pyrite catalyst under air for the hydrogenation of 1-methylnaphthalene are investigated under coal hydro-liquefaction conditions. Pyrite is oxidized to ferrous sulfates at room temperature under atmospheric oxygen, and the catalytic activities of FeS 2 oxidized decreased by increasing the storage time. The deactivation of pyrites is enhanced by raising the atmospheric temperature. It is proved that pyrites deactivated by air oxidation are reactivated by the addition of sufficient sulfur to the reaction system.

Role of additives in diarylalkane degradation as a model reaction of coal liquefaction

Publisher Summary This chapter discusses the role of additives in α, ω-diarylalkane (DAA) degradation as a model reaction of coal liquefaction. Quite different roles between iron (Fe) and iron sulphide (FeS 2 ), molecular hydrogen and hydrogen donors are observed, and the relationship between the structures of DAAs and their reactivities for hydrocracking is revealed. 1-Benzylnaphthalene (1-BN) and di(1-naphthyl)methane (DNM) are synthesized by heating naphthalene with benzyl chloride and 1-chloromethylnaphthalene, respectively, in the presence of zinc powder. 1,2-Di(1-naphthyl)ethane (DNE) and 1,3-di(1-naphthyl)propane (DNP) are synthesized according to the methods of Buu–Hoi and Nishimura, respectively. The results of the reaction of diphenylmethane (DPM) under different reaction conditions are summarized in the chapter. DPM is very stable thermally.

Low temperature oxidation of coals.

The oxidation of different rank coals was carried out at the temperature from 70°C t to 150°C t under oxygen in order to understand the profile of the oxidation of coal. Ox-ygen consumption, weight change of the coals and the amounts of evolved gases such as CO2, CO, CH4 and H2O were measured to monitor the oxidation of coals. Further, the recovered coals were characterized by means of CP/MAS 13C-NMR, IR and elemental analysis.The oxidation of the coals caused a significant decrease in aliphatic carbons resulting in the evolution of CO2 and H2O, and the lower the coal rank such as Yallourn and Taiheiyo coals is, the greater the tendency. The amount of oxygen incorporated into the coals relatively increas-ed with the carbon content in coal. It was suggested that most of the oxygen incorporated was consumed in the formation of polar groups and the other was consumed in the cross-linking of aromatic structures in coal