University of Utah Process

The residence time of the solids in the reactor is usually less than 12 s, whereupon approximately 60% of the coal is converted to liquid products. Up to 85% of the zinc can be recovered by water-washing the char on the other hand, acid washes of the char are reported to raise the recovery of the zinc from 95% to 99%. 

The use of zinc chloride as a means of liquefying coal is not surprising since there has been an interest in process catalysis by Lewis acids (e.g., zinc chloride) from the very early days of coal liquefaction technology (Nowacki, 1979). The chemistry involved in the hydrocracking (and other) reactions is not fully understood and therefore any mechanistic speculations are not warranted here. 

---

In the University of Utah process (Figure 19.18), crushed coal is impregnated with zinc chloride (approximately 3% w/w of the coal) and the mix is fed from pressurized lock-hoppers into... 

---