Cellulosic materials can be partially or totally hydrolyzed in acetone solution with the addition of small amounts of acidic catalysts. The hydrolysis process can be operated at 145-228°C with 70-100% acetone [162]. In a high concentration acetone solution, the formation of stable complexes with sugars can prevent the degradation of the material. The produced lignin and sugars were claimed to be commercially useful products. By using acetone fractionation process, wood or delignified pulps can be converted into saccharified feedstock to produce pento­sans and hexosans followed by sugars. It has been patented that lignocellulosic material can be cooked at 180-200°C with 60-70% (v/v) acetone containing 0.02-0.25% phosphoric, sulfuric or hydrochloric acids as a catalyst [163]. After the fractionation, a high purity of glucose fraction was obtained with the pre­dominately cellulosic material, whereas mixed pentose and hexoses were produced when applying the whole wood as a feedstock.

Acetone pulping of wheat straw [164-166] and Eucalyptus [167] has also been reported. For instance, a treatment using a temperature of 180°C, an acetone concentration of 40%, a cooking time of 60 min and 1,750 beating revolutions,
resulted in pulp with similar or even better properties than those for soda pulp. It was claimed that the advantages that the process was less contaminating since the acetone was easy to be recovered and that the dissolved liquor rich in lignin had great potential use in the production of new materials. In addition, acetone has been used in mixtures with formic acid [168], ethanol [169] and the mixtures of them [170]. Furthermore, oxygen delignification can be modified to oxygen — acetone delignification process. For instance, oxygen delignification of cotton­wood in acetone/water solutions (60/40, v/v) was evaluated with respect to pulping conditions as well as delignification kinetics [171, 172].

Recently, acetone organosolv fractionation of wheat straw has been studied to produce sugars and lignin [139]. The optimal conditions, i. e., 50% acetone for 1 h at 205°C, resulted in 82% hemicelluloses degradation, 79% delignification and 93% cellulose recovery. It has been shown that the acetone process improves the enzymatic hydroablity. After the fractionation pretreatment, a high glucose con­version yield up to 87% was achieved as compared to 16% for the untreated wheat straw. In another report, Pinus radiata D. Don was subjected to acetone pre­treatment. A higher ethanol yield of 99.5% was achieved under the pretreatment conditions below: 50% acetone, pH 2.0, 195°C and 5 min [138].