Coal liquids have a very complex composition including paraffins, naph-thenes, phenols, basic compounds and alkylated aromatics which have so many isomers that it is very hard to separate pure compounds.
Thermal dealkylation is one method for simplifying the composition of coal liquid be-cause nearly all isomers decompose to unsubstituted aromatics.
In the previous studies the authors tried to use methanol as a hydrogen source in-stead of hydrogen itself. Methanol decomposes thermally to carbon monoxide and hydrogen. This hydrogen produced from methanol in situ acts favourably on the dealkylation of coal liquid.
In this study we examined the possibility of recycling excess hydrogen produced as a flow gas and to supply the consumed hydrogen as methanol. Thermal dealkylation of ethylbenzene as a model compound and coal liquid were carried out in the quartz glass tube reactor in H2 flow under normal pressure at 700-950°C varying the H2 flow rate or methanol concentration.
The main results are as follows:
1) In the reaction of ethylbenzene with methanol in N2 flow, with increasing the con-centration of ethylbenzene in methanol, the yield of carbon and heavy condensation products increased and that of benzene decreased, because of the increase of the conde-nsation reaction of aromatic nuclei. In the present results with the quartz tube reactor, the yield of benzene was a little higher than the previous ones with the stainless steel tube reactor at same condition.
2) In the reaction of ethylbenzene with methanol in H2 flow with increasing the con-centration of methanol, the yield of carbon and heavy condensation products decreased and that of benzene increased. It was shown that for dealkylation in H2 flow, methanol addition is very effective.
3) After the reaction of coal liquid (naphtha and light oil) at 850°C 24ml/min of H2 flow rate, and 13 wt‰ of methanol addition, almost all paraffins, naphthenes, phenols and alkylated aromatics disappeared. The composition of liquid product became extreme-ly simple. Each main components will be easily separated by simple method.
