Formation of caking coals

Abstract

Highly caking coals are formed by selective oxygen-alkylation or oxygen-acylation of moderately, weakly or non-caking coals, employing a phase transfer reaction which chemically alters phenolic and carboxylic functional substituents. These two very polar functional groups are converted to relatively non-polar ethers and esters, respectively. The O-alkylation or O-acylation is carried out in a binary liquid phase solution (organic and water phases with a solid phase suspended in the medium). A quaternary ammonium or phosphonium salt is reacted with alkali or alkaline earth base to produce the corresponding quaternary ammonium or phosphonium base (an example of a phase transfer reagent). This quaternary base is non-nucleophilic and readily removes the phenolic and carboxylic protons but does little else to the coal structures. After the removal of the weakly acidic protons by the quaternary base, the phenoxides and carboxylates which are produced then undergo O-alkylation or O-acylation. The alkylating or acylating agent comprises a carbon-bearing functional group and a displaceable leaving group. The process of the invention produces caking properties in non-caking subbituminous coals and increases the caking ability of weakly or moderately caking coals. An important aspect of this invention concerns the coal liquids and gases which are produced during coke formation. The pyrolysis which forms the coke of the O-alkylated or O-acylated coal also produces higher quality coal liquids and gases.