Natural gas is an abundant resource in the world as well as petroleum.There have been many research activities on the conversion of natural gas to liquid fuels. In New Zealand, the famous GTG (Gas To Gasoline) plant has been operated commercially since 1986, producing gasoline of over 570, 000t/y which is about one third of the domestic demand of liquid fuels in the nation. Another plant converting natural gas to liquid fuels by Fischer-Tropsch process is now being constructed in Malaysia by Shell. However, these indirect processes include syngas production from methane, which needs very high operation cost. On the other hand, direct conversion of methane to liquid fuels without syngas production is a developing technology. It is expected that the fuels are produced in lower cost. The followings are considered as possible processes. 1) Oxidative coupling of methane (OCM)-Oligomerization process, in which methane is converted to C2 compounds with oxygen, followed by polymerization of C2 to liquid fuels. 2) Oxyhydrochlorination (OHC)-Oligomerization process, in which methane is converted to chloromethane with hydrogen chloride and oxygen, followed by polymerization of chloromethane to the liquid. 3) Direct Methanol Synthesis (DMS)-Methanol To Gasoline (MTG) process, in which methane is partially oxidized to methanol, then converted to gasoline by Mobil's MTG process. Among these, the OCM process seems to be the most feasible one at present technology level. A few OCM processes for production of liquid fuels have been developed independently by ARCO (USA), IFP (France) and CSIRO (Australia). Recently, Japan National Oil Corporation has started the joint study project titled “Natural Gas Conversion Process” which is cooperative work with Japan Petroleum Exploration Co., Ltd. and Cosmo Research Institute. In this review, recent advances in direct conversion of methane in the world and the outline of the Japanese new project are described.
The activity of chromium oxide catalysts which promoted the hydrogenation of Yubari coal, were estimated using naphthalenes and 1-naphthol as coal model compounds. Naphthalene was mainly hydrogenated to tetralin, and its yield and selectivity reached approximately 80% and 90%, respectively. Moreover, the activity of chromium oxide catalyst was compared with those of some commercial hydrogenation catalysts. The characteristic of this catalyst was similar to that of Cu-Cr catalyst. From the standpoint of selective formation of tetralin, this catalyst was the best of these commercial catalysts. 1-Methylnaphthalene was mainly hydrogenated to 1- or 5-methyltetralin along with naphthalene and tetralin. In this reaction, two pathways were observed: dealkylation and hydrogenation. Furthermore, the amount of tetralin was fairly large with increasing reaction time. 1-Naphthol was mainly reductive Deoxygenation to naphthalene and hydrogenated to tetralin. The catalyst activity, however, was remarkably depressed under the influence of water formed by the hydrocracking of 1-naphthol. The XRD analysis showed that the chromium oxide catalysts contained too much Cr2O3. Therefore, it was considered that the activity of chromium oxide catalyst was caused by a small amount of undetermined chromium oxides present in chromium oxide catalyst.
SYNOPSIS: -The selection of technologies for supply of electricity and liquid fuel from natutal gas and/or coal was evaluated in this paper from the viewpoint of reduction of CO2 emission in the long run, when petroleum would not be produced. If natural gas would not be supplied enough to satisfy both demands of electricity and liquid fuel and if those technologies would not be improved in the thermal efficiency from the present practical levels, natural gas used for the electricity power generation should be replaced by coal because CO2 emission of its system would be smaller than the system in whish coal is used for the liquid fuel production. However, if the direct coal liquefaction technolgy is improved near the level of theretical reaction, the utilization of coal for the liquid fuel production instead of the electricity pomer generation can reduce CO2 emission in the total system. In this case, if hydrogen produced from natural gas is used for the direct coal liquefaction, CO2 emission will be reduced much more. The integrated energy system, in which excess hydrogen in the liquid fuel production from natural gas is used for the indirect liquefaction of coal, would be useful for the reduction of CO2 emission when the reaction heat of the steam reforming of natural gas is supplied from the outside such as high temperature gas cooled nuclear reactor.
Illinois No.6 and Miike coals were extracted with carbon disulfide-N-methyl-2-pyrrolidinone mixed solvent (CS2-NMP), respectively. The extract was separated into four fractions such as WS (water-acetone soluble fraction), AS (acetone soluble fraction), PS (pyridine soluble fraction), and MS (CS2-NMP soluble fraction) along with residue. Main three samples such as AS, PS, and the residue and their acetylated samples along with original coals and their acetylated ones were analyzed by Curie-point pyrolysis and gas chromatography-mass spectrometry. The acetylation of the samples seems to result in the reduction of coke amount accompanied with pyrolysis. The plot of coke amount of each fraction versus the number of its OH group indicated that coke amounts decrease, in a way to depend upon coal employed, as the number of OH groups decrease. This suggests that the coke formation in the pyrolysis of extracts and residue of both coals has some relation with OH group content. The pyrograms of AS, PS, and the residue were very similar in the same coal; that of Illinois No.6 coal was rich in phenol derivatives while that of Miike coal was rich in saturate compounds. In the total ion chromatograms of the pyrolysate from AS fraction of both coals, more than 130 compounds were identified. As for isomers in the total ion chromatograms of AS fractions from both coals, six ones for C3-benzene and eight ones for C4-benzene were found, while seven isomers for C2-phenol and eight isomers for C3-phenol. Taking into consideration the overlapping of some isomer peaks on gas chromatogram, all isomers of C3-benzene (8) and C2-phenol (9) seem to be contained in the pyrolysates. Relatively small numbers of isomers found as C4-benzene and C3-phenol seem to be limited to the heat history of the coals during their coalification.
In the present study, we examined the production method of the carbonaceous adsorbent, in which acrylonitrile and methyl acrylate copolymers were used as raw materials, and phosphate and zinc chloride were added as carbonization and activation accelerating agents. The raw materials were treated in air for 7hr at temperatures between 120-220°C. Three parts of 50% aqueous solution of phosphate or zinc chloride were added to 1 part of each char (PANACHP, PANACHZ), and the solution was then directly placed in a reaction oven at 600-900°C. The weight reduction rate W/Wo (-) decreased linearly with increased activation time. Both the methylene blue adsorbability (MB) and the internal surface area (S) of the activated material showed a maximum value and then decreased with increased activation time. MB and S of PANACHP and PANACHZ showed the maximum value in conditions with activation temperature of 900°C and activation time of 180min. In these conditions, the following results were obtained: MB: 450mg/g and S: 1, 280m2/g for PANACHP and MB: 310mg/g, S: 1, 080m2/g for PANACHZ, indicating that both PANACHP and PANACHZ were carbonaceous adsorbents which possessed more than twice as much mercaptan gas adsorbability as the activated carbon on the market.