Liquid clathrates coal liquefaction

The first examples of materials that supported liquid clathrate phase formation, in contact with aromatic hydrocarbons, were highly reactive air-sensitive salts containing alkylaluminum anions, first described by At-wood. " Their applications for separations of aromatics from hydrocarbons and in coal liquefaction were extensively explored. However, a drawback of the initial systems studied was their air-sensitivity and reactivity. 

Since the initial discovery of liquid clathrate systems, hundreds of compounds having the structure M[Al2R6X] were found to exhibit liquid clathrate behavior.While these highly reactive air-sensitive salts are useful in such applications ranging from separations of aromatics from hydrocarbons to coal liquefaction, their air-sensitivity and reactivity posed drawbacks to further study. 

Another interesting application of liquid clathrates that was explored is in coal liquefaction. This patented application resulted in the rapid partitioning of 23% of the coal mass into the liquid clathrate phase of a toluene-based liquid clathrate system at It is reported that... 

Liquid clathrates represent an interesting area of supra-molecular chemistry. Over the years, the move from air-sensitive to air-stable liquid clathrate systems greatly simplified their handling procedures. Also, with the emergence of air-stable liquid clathrate systems, their possible applications broadened beyond early useful applications of coal liquefaction and hydrocarbon separations to include aqueous separations and catalytic systems. 

Of the several interesting applications of liquid clathrates is in the area of separations. Since the behavior is found for aromatic molecules but not for aliphatic ones, a separation is possible. It is possible to envision even difficult problems such as the separation of the xylene isomers being attacked by liquid clathrates. Liquid clathrates have also been reported to be useful as solvents for the liquefaction of coal. 

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