Бурение грунтовых зондов, установка энергетических колодцев

Another cellulose solvent that has attracted attention in recent years as a pretreatment medium is N-methyl morpholine N-oxide (NMMO). This polar aprotic solvent is thought to behave somewhat similar to ionic liquids. N-methyl morpholine N-oxide (NMMO) is a direct solvent for cellulose which is industrially used in an envi­ronmentally friendly process for fiber making called the lyocell pro­cess [146]. It is believed that high polarity of N-O bonds in NMMO causes hydrogen bond network in cellulose to break and form new hydrogen bonds [147], allowing cellulose to dissolve in NMMO. In an earlier example, Shafiei et al. showed that it is possible to improve the ethanol yield of hard — and softwood from 18.6% and 6.8% to 85.4% and 89%, respectively, by 3 h pretreatment at 130°C with 85 wt% NMMO solution [148]. In another study, Kuo and Lee treated sugarcane bagasse with NMMO at 130°C for 1 h and the results showed enzymatic hydrolysis that was at least two times better in treated samples, compared with the untreated bagasse [149]. This technique is particularly useful for woody biomass, and NMMO pretreatment has resulted in a nine-fold increase in ethanol yields in the case of birchwood [150]. In a recent study, Karimi and cowork­ers compared the pretreatment efficiencies of NMMO and ionic liq­uid 1-”butyl-3-methylimidazonium acetate (BMIMOAc) using rice straw as the biomass substrate [139]. In this study treatments were conducted with N-methyl morpholine N-oxide (NMMO) and 1-”bu- tyl-3-methylimidazolium acetate (BMIMOAc) at 120°C for 1, 3, and 5 h with 5% rice straw loading. Then, the treated and untreated straws were subjected to enzymatic hydrolysis at 45°C for 72 h by using a mixture of 20 FPU cellulase and 30 IU в-glucosidase per each gram of substrate. Hydrolysis results indicated a complete conversion of glucan in BMIMOAc-treated straw to glucose and a hydrolysis yield of 96% for NMMO-treated samples, while the con­version was only 27.7% for the untreated straw. Hydrolysis yields from rice straw samples subjected to pretreatments with NMMO and BMIMOAc after 24 and 72 h are shown in Figure 5. 10.

Then ethanol production by simultaneous saccharification and fermentation was carried out at 38°C for 48 h. The results showed that ethanol production yield was improved from 35.4% for untreated straw to 93.3% and 79.7% after 5 h pretreatment with NMMO and BMIMOAc, respectively, as shown in the Table 5.7.

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Figure 5.10 Hydrolysis yields of untreated and various treated straws, showing a comparison between N-Methyl Morpholine N-Oxide and 1-”butyl- 3-methylimidazonium acetate pretreatments. The black and dark gray colors represent the sugar yields after 24 and 72 h enzymatic hydrolysis respectively. (Reprinted with permission from reference [139]; copyright 2013 Elsevier).

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