Method for recovering sulfuric acid from concentrated acid hydrolysate of plant cellulose material

Abstract

A method for recovering sulfuric acid from concentrated acid hydrolysate of plant cellulose material is disclosed. In some of the examples, the concentrated acid hydrolysate is mixed with a liquid organic precipitant, thereby the sugars in the hydrolysate is precipitated and separated out, and the remained is sulfuric acid and an organic solvent solution. Then the organic solvent is separated by distillation or extraction, thereby obtaining the pure sulfuric acid solution. This precipitation method can recover above 90% sugars and acids with a small amount of organic precipitant, which greatly reduces the recover cost. In the other examples, the method includes: mixing the concentrated acid hydrolysate with a water-immiscible alcohol, thereby separating the sugars with a remainder of acid-alcohol solution containing sulfuric acid; contacting the acid-alcohol solution with water, thereby the sulfuric acid enters into the water phase from the organic phase; then separating the organic phase and the water phase, thereby obtaining the sulfuric acid solution. This method avoids the use of poisonous, inflammable and explosive organic solvents and also avoids the energy consumption for recovering these organic solvents, thereby greatly reducing the cost of acid recovery.

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