Mikio Miyake

Improved method to alkylate Yūbari coal of Japan using molten potassium under refluxing THF

A modification to Sternbergs procedures of reductive alkylation of coals is proposed. The ‘coal anion’ formation reaction is conducted under refluxing THF without any electron transfer agent and with molten potassium metal. The method was applied to Yūbari coal (86 wt % C) whereby varying reaction times (0.5–6 h) altered the lengths of alkyl groups (CH3ue5f8C4H9) added. In a typical experiment, a butylated Yubari coal, prepared by the 2 h reaction, contained 7 butyl groups per 100 original carbon atoms and solubility in hot benzene was 75 wt %. The numbers of alkyl groups introduced and the solubilities of coals increased with reaction time. Values obtained were comparable to those reported using conventional procedures which required longer reaction times and an electron transfer agent l.r. spectra of butylated coals showed strong adsorption peaks attributed to aliphatic groups. Benzene-soluble—pentane-insoluble material of the alkylated coal had less condensed aromatic components with more alkyl side-chains compared with Yūbari SRC, which were estimated by the Brown—Ladner method. Contamination of the alkylated coal by THF fragments seems to be negligible, since hydrogenated naphthalene, obtained after treatment with molten potassium, contains no alkylated products. The reaction proceeded also in HMPA, but not in straight-chain hexane.

Coal hydroliquefaction using MoCl3- and NiCl2-containing salts as catalysts: difference in catalysis between solid and molten catalysts

Abstract Both MoCl 3 - and NiCl 2 -LiCl-NaCl-KCl quaternary solid salts and both MoCl 3 - and NiCl 2 -LiCl-KCl ternarly molten salts were examined as catalysts for hydroliquefaction of subbituminous Wandoan coal at 400 °C for 1 h in a batch reactor with an initial H 2 pressure of 9.8 M Pa. Conversions (to pyridine solubles) and yields of hexane solubles (HS) ranged from 80 to 92 wt% and from 55 to 65 wt%, respectively. The results suggested that both solid and molten catalysts are highly effective for hydrocracking of coal, with the latter being superior in terms of conversion and HS yield. H 2 consumption of the reaction suggested that the hydrogenating ability of the catalysts decreases in the following order: NiCl 2 (molten) > MoCl 3 (molten) > MoCl 3 (solid) > NiCl 2 (solid). Cracking ability of these catalysts decreases in the order: MoCl 3 (molten) > MoCl 3 (solid) > NiCl 2 (molten) > NiCl 2 (solid). It was tentatively concluded that the molten catalysts have higher hydrogenating and cracking abilities for coal hydroliquefaction than the corresponding solid ones.

Effects of reductively introduced alkyl groups and hydrogen to mesophase pitch on carbonization properties

Abstract A mesophase pitch, which consisted of developed aromatic rings (15–17 fused rings) and contained only a few alkyl groups per molecule, was subjected to reductive alkylation (methyl and ethyl) and hydrogenation using potassium metal followed by alkyl iodide and alcohol, respectively, in order to assess the effects of reductively introduced alkyl groups and hydrogens on the formation of anisotropic texture. When the hydrogenated pitch was carbonized at 400°C for 10 min, the anisotropic content increased by an increase in the number of introduced hydrogens, while the anisotropic content from the alkylated pitch decreased, depending on the number and steric size of alkyl groups introduced. The original and hydrogenated pitches were nearly stable until 400°C, whereas dealkylation occurred for the alkylated pitches. A degree of the demethylation increased by an increase in a soaking period at 400°C, accompanied by an increase in the anisotropic content. The demethylation led to no significant polycondensation reactions, and resulted in an increase in the stabilized radical concentrations. The bulkiness of the reductively methylated and hydrogenated products was calculated to be 7.6 and 5.2 A by adopting dihydrodimethyl- and dihydro-pyrene as model compounds, respectively. The difference in such steric sizes between the two groups may be responsible for the different tendency in the anisotropic formation when carbonized at 400°C for 10 min.

An electrochemical study of the photocatalytic oxidation of methanol on rutile

Abstract Photocatalytic oxidation of methanol and 2-propanol by oxygen on illuminated rutile catalysts was analyzed by electrochemical measurements, and the indication was obtained that the Wagner-Traud mechanism prevails in the photocatalytic oxidation of these alcohols; i.e., the oxidation reaction consists of the anodic oxidation of the alcohol and the cathodic reduction of either oxygen or a complex consisting of oxygen and an intermediate of oxidized alcohol.

Effect of small amounts of hydrogen introduced reductively into coal on its hydroliquefaction

Abstract Kairan, Miike and Akabira bituminous coals were reductively hydrogenated by treatment with metallic sodium in liquid ammonia or with molten potassium in refluxing THF, followed by hydrogenation with methanol. These pretreatments added some hydrogen to aromatic rings and cleaved some Cue5f8O and/or Cue5f8C bonds connecting the structural units of the coal. Hydroliquefaction at 425 °C in tetralin was enhanced by this pretreatment, with in some cases a reduction in the total hydrogen consumed. For Akabira coal, liquefaction was also performed at 450 °C. Hydrogen introduced into the coal markedly affected both conversion and product distribution, especially in the early stages of liquefaction. This can be partly explained in terms of the shuttling effect of hydrogen added to aromatic rings, stabilizing the reactive coal fragments in the initial stages of the reaction.

Hydrogenation of Yūbari coal coated with ZnCl2-MCln (CuCl, CrCl3 and MoCl5) catalyst melts

Abstract Hydrogenation of Yūbari coal coated with 5 wt% of ZnCl 2 -MCl n (CuCl, CrCl 3 and MoCl 5 ) was carried out at 400 °C for 3 h with an initial hydrogen pressure of 9.8 MPa. The binary melt catalysts showed relatively higher activity in increasing the yield of hexane-solubles than did ZnCl 2 alone. The ZnCl 2 -MoCl 5 catalyst melt was best in view of its highest conversion (90.9 wt%), the highest yield of hexane-soluble material (50.5 wt%) and the smallest hydrogen consumption. In terms of yield of monoaromatics of the hexane-soluble material relative to polar materials, ZnCl 2 -CrCl 3 catalyst was superior to ZnCl 2 -MoCl 5 although its hydrogen consumption was high. The roles of CuCl, CrCl 3 and MoCl 5 in association with ZnCl 2 in coal-hydrogenation are discussed.

Comparison of coal hydroliquefaction catalysed by ZnCl2-MCln (CuCl, CrCl3 and MoCl5) and ZnCl2 melts

Abstract Hydrogenation of four bituminous coals impregnated with 5 wt% of either mixtures of ZnCl 2 - M Cl n (CuCl, CrCl 3 and MoCl 5 ) systems or ZnCl 2 was carried out using a batch autoclave system at 400° for 3 h at 9.8 MPa of initial hydrogen pressure. The ZnCl 2 -MoCl 5 system showed the highest yield of the hexane-soluble (HS) fraction compared with the other systems irrespective of the coal used. The difference between the yields of HS fractions using the ZnCl 2 -MoCl 5 and other systems was most marked for coals of fairly low volatile matter content, though the conversion was relatively low (47–66%), whilst for coals of high volatile matter content HS yields with the binary melt systems were high (86–91% conversion). Elemental analyses of the HS fractions indicated that the ZnCl 2 -MoCl 5 system is most favourable in decreasing the average molecular weight and the heteroatom content of HS, this characteristic trend being confirmed also with five HS fractions separated by Chromatographic techniques. Both elemental analyses and molecular weights of asphaltene (benzene-soluble materials, BS) indicated that the ZnCl 2 -MoCl 5 system is also most effective in cracking coal structure.

Catalytic activities of binary molten salts composed of ZnCl2 and metal chlorides for hydrocracking of phenanthrene

Abstract Phenanthrene, a coal model compound, was hydrocracked in a batch autoclave at 400 °C for 3 h with an initial hydrogen pressure of 9.8 MPa and equimolar concentrations of molten salts. Binary salts composed of ZnCl 2 and metal chlorides, such as CuCl, MoCl 5 CrCl 3 , NiCl 2 , and PdCl 2 , etc., showed superior catalytic activity to pure ZnCl 2 (MCI x /ZnCl 2 molar ratio was fixed to 1 4 ). The isomerization of cyclohexene and H 2 −D 2 exchange reactions were also examined to estimate acid-catalytic and hydrogen-activation abilities, respectively. Both activities were found to increase with the addition of metal chloride to ZnCl 2 , indicating synergistic catalytic activity. Phenanthrene conversions (as a measure of hydrocracking activities of the salts) over some catalysts correlated rectilinearly with yields of isomerized products of cyclohexane.

Carbonization of methylene-bridged aromatic oligomers

Abstract Methylene-bridged oligomers were prepared from naphthalene, binaphthyl, anthracene, tetralin, biphenyl, dibenzofuran, and xanthene by condensation reaction with methyral. These oligomers, NC, BNC, ANC, TETC, BPC, DBC, and XANC, respectively, were carbonized under atmospheric pressure. The oligomers can be classified into two groups from the optical textures of their resultant cokes (i.e., the first group consisting of BPC, DBC, and XANC exhibited isotropic textures after carbonization at 470°C while the second group of NE (NC), BNC, ANC, and TETC produced the anisotropic textures of wide-flow domain type). The differences in carbonization properties among the oligomers are studied from the viewpoint of structural changes during carbonization, on the basis of field desorption mass spectrometric analysis.

Hydrocracking of asphaltene from coal using ZnCl2 as catalyst

Abstract Coal liquefaction catalysis by ZnCl 2 was investigated by analyzing the evolution of structures from a starting material to liquid products under a series of reaction conditions. Asphaltene, derived from reductively methylated coal, has been assumed not to significantly alter macromolecular structures derived from the parent coal because of the large molecular weight of over 3000 and has been adopted as a starting material for hydrocracking. The hydrocracking was carried out using a batch autoclave system at 9.8 MPa initial hydrogen pressure by varying the reaction time (0–5 h), the temperature (350–440°C), and the amount of ZnCl 2 (5–40 wt.%). The hydrocracked products were fractioned by solvents and detailed structural parameters of the materials soluble in n-hexane (HS) and benzene (BS-HI) were estimated. At 400°C with 10 wt.% ZnCl 2 , HS was obtained as the main product. The structural parameters of the soluble derivatives indicate that depolymerization proceeds by cleavage of ether bonds, which occurs easily, even at 350°C. Extension of the reaction time led to an increase in the HS yield and gave rise to the saturation of the aromatic rings and moderate subsequent decomposition of the products containing naphthenic rings. On the other hand, highly developed aromatic nuclei were gradually concentrated in BS-HI. When the amount of ZnCl 2 was increased to more than 10 wt.%, decomposition of the aromatic nuclei proceeded extensively at 400°C, in addition to depolymerization by the cleavage of carbon-carbon linkages. Noticeable dealkylation of the asphaltene took place above 400°C in the presence of 10 wt.% ZnCl 2 .