コールベッドメタンは炭層内に含まれる, 石炭生成時に生成したメタンを主成分とするガスであり, 米国における賦存量は400TCF (1.1×10¹³m³) と見積もられている. コールベッドメタンの開発は, 当初鉱山保安のためのガス抜きとその一部の利用にとどまっていたが, 現生ではメタンが強力な温室効果ガスであるため, 地球環境問題の視点から, 従来大気中に放出されていた炭層からのメタンの有効利用が議論され, また, 経済性の点からも天然ガスと同等以上の品質と低廉な採掘コストによりコールベッドメタンは資源として有望視されている. 現在, 米国のコールベッドメタン生産は主にSan JuanおよびBlack Warrior堆積盆で行われており, ここ数年, 生産量は急速に増加し, 1992年の国内生産量は550BSCF (1.5×10¹⁰m³) に達している. 本総説では, 米国において行われているコールベッドメタン研究を、多成分ガスの吸着挙動やメタンの吸着状態の検討による基礎研究, 各種モデルおよびシミュレーション計算による貯留体特性の研究, 坑井仕上げおよび生産井に関する研究の3分野に大別し, 各分野における最近の研究動向を概説する.

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The future global energy demand will increase in exponential progression especially in developing countries. On the side of supply, however, the production of its major components such as oil, coal and natural gas is estimated to reach a plateau towards the earlier half of the 21st century. The objective of the present review is to search approaches how to make up the apparent gap between this demand and supply in near future.
The leading components of energy consumption in advanced countries are fossil fuels, hydraulic, and nuclear powers; however, in developing countries, 2, 000 million people live on firewood while the rest on firewood and fossil fuels as well. Therefore, the future lack in fossil fuels and resulting price hike will lead to overgathering of firewood. This will cause an accelerated deforestation in broader area, and will result in further acceleration in environmental destruction in worldwide scale.
In order to find major countermeasures against this sort of destruction, overall survey for the possibilities is made in the following items: (1) Improvement in efficiency of energy consumption/save-energy, (2) Further promotion of nuclear power, (3) Further development of natural energy resources, (4) Forest management for prevention of its conversion to farmland or pasture ground and overgathering firewood, and (5) Further promotion of sea-food and marine biomass production, etc.
These countermeasure items are closely connected mutually; therefore, further detailed investigation may be advised into the future gross balance of demand and supply by organizing joint-study teams on each specialty and interdisciplinary areas.

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Authors have previously proposed a method to evaluate chemical structure of Akabira coal by combined use of pyrolysis and solid state ¹³C-NMR data. This method is to evaluate distribution of aromatic compounds using pyrolysis data of its extracts. Adjustment of distribution of aliphatic and aromatic carbons was carried out by using CP/MAS ¹³C-NMR data of raw coal.
In this method, volatile fraction of extracts in pyrolysis is assumed to represent whole constituents of the extracts. In order to examine whether above assumption is correct or not, distribution of 9 kinds of carbons in the coal, which is comparable with those from solid state NMR measurement, was calculated based on pyrolysis data. Above calculation was carried out for Illinois No.6 and Miike coals by using several assumptions (i) all alkyl aromatics are present as methylated derivatives, (ii) isomers ratio is equivalent, (iii) non protonated aromatic carbons are included in Ar-C, and (iv) aromatic carbons next to oxygen atom in benzo- and dibenzofuran are included in Ar-O. These results were compared with that of raw coal from CP/MAS ¹³C-NMR. This comparison brought about relatively good coincidence between the carbon distributions of Illinois No.6 coal from pyrolysis and NMR data, while there was a little discrepancy between these carbon distributions for Miike coal. This tendency was discussed briefly.

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In order to clarify the possibility of safe utilization of insulation oil in which contained trace amounts of polychlorinated biphenyls (PCBs)- on the order of 250ppm or less-as fuel, laboratory experiments for evaluation of degradation conditions of PCBs were conducted. Oxidative pyrolysis using a flow reactor and premixed combustion of vaporized oil were performed, and products were analyzed quantitatively for PCBs, polychlorinated dibenzo-p-dioxines (PCDDs) and polychlorinated dibenzofurans (PCDFs).
Pyrolysis experiments at the conditions in which oxygen in excess revealed that the complete degradation of PCBs was attained at 973K or more. This temperature was slightly lower than the case of pure PCBs. At the condition of 923K or less, not a little PCBs were remained and PCDFs were also detected. In combustion experiments, PCBs, PCDDs and PCDFs were not detected at all experimental conditions. Because the hazardous products were not detected at the condition of short residence time after combustion, it is found that the degradation of PCBs were completed in the flame zone.

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The gasification reactivity of the chars prepared from an Australian brown coal, Morwell, by several methods was measured, and was correlated with several char properties. Although the chars were prepared at the same temperature of 750° under the same heating rate, the char yield, the pore surface area and the ultimate analysis varied significantly depending on the coal pre-treatment method and/or the atmosphere during the pyrolysis. The pore surface area, for example, ranged from 240 to 520×10³m²/kg, and the oxygen content varied also from 8.9 to 21.6%. The gasification rate of the char prepared from a coal-methanol mixture was only one-tenth of the char prepared from the raw coal. The reaction rate of the char prepared from a coal pre-swollen with tetralin was almost similar to the reaction rate of the char prepared from the raw coal, although the char yield of the former sample was smaller than that of the latter sample by 10kg/100kg-coal. An excellent correlation whose correlation coefficient was 0.99 was obtained between the gasification rate and the oxygen content of the char. This is because the oxygen content measured in this work well corresponds to the amount of active site of the char.

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The liquid products derived from Miike coal were separated into weakly acidic (WA1), strongly acidic (SA1), neutral-hexane insoluble (N-HI1), basic-benzene soluble (B-BS1), and basic-benzene insoluble and dichloromethane solu-ble (B-BI1) fractions. The additive effects of phenols on their denitrogenation (DN) were investigated in detail by the hydrogenolysis reactions with a sulfided Co-Mo/Al₂O₃ catalyst.
Additive effect of phenol could not be observed in DN of WA1, due to the increased acidity of the catalyst caused by phenols in WA1. However, phenol addition was very effective in DN of SA1 containing only a small amount of phenols. When 7.0% of phenol was added to N-HI1, the hydrogenolysis was promoted by the catalyst of increased acidity. The adsorption of nitrogen-containing aromatic rings of B-BS1 on the catalyst surface was inhibited by the steric hindrance of long-chain alkyl groups bonded to aromatic rings. Therefore, phenol addition did not affect the DN of B-BS1. On the other hand, the DN of B-BI1, which does not have long-chain alkyl groups bonded to aromatic rings, was slightly promoted by phenol addition. Cresol isomers were as effective as phenol for the DN.

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