Sorbitol hydrogenolysis

Ruthenium is excellent for hydrogenation of aliphatic carbonyl compounds (92), and it, as well as nickel, is used industrially for conversion of glucose to sorbitol (14,15,29,75,100). Nickel usually requires vigorous conditions unless large amounts of catalyst are used (11,20,27,37,60), or the catalyst is very active, such as W-6 Raney nickel (6). Copper chromite is always used at elevated temperatures and pressures and may be useful if aromatic-ring saturation is to be avoided. Rhodium has given excellent results under mild conditions when other catalysts have failed (4,5,66). It is useful in reduction of aliphatic carbonyls in molecules susceptible to hydrogenolysis. 

Comparison of the catalysts in Figure 1 demonstrates that the Ni/Re catalyst yielded the highest activity of the catalysts under the conditions tested. The Rh/Re catalyst also showed excellent conversion at 240°C as did the Ru catalyst which is also known to be an excellent hydrogenolysis catalyst for conversion of sorbitol to these products [4,5], The Ru/Re and Ru/Re+ catalysts also demonstrated high conversion, especially at high temperatures. 

Normally, however, the reaction involving the formation of hydroxy-methylfurfural proceeds less readily than does the hydrogenation of glucose and fructose to mannitol and sorbitol, but its occurrence is detected by the fact that tetrahydrofuran derivatives have been isolated from the hydrogenation products. Thus, we have isolated tetrahydrofuran 2,5-dicarbinol (identified as its ditosyl derivative), 5-methyltetra-hydrofurfuryl alcohol and 2,5-dimethyltetrahydrofuran (VII) together with hydrogenolysis products of these compounds. 

Hydrogenolysis. C-C and C-O bond breaking by hydrogenolysis of different polyols (glycerol, xylitol, erythritol and sorbitol) has been investigated by Montassier et Predominantly ruthenium and copper-based... 

Table 7.221 Hydrogenolysis of Sorbitol and Glycerol at a Hydrogen Pressure of 2,000 psi (32)...

Fig. 24 Results of sorbitol hydrogenolysis over Ir-Re0 c/Si02 + H-ZSM-5 [68]. Reaction conditions sorbitol 1 g, water 4 g, n-dodecane 4 mL, F(H2) = 8 MPa, T = 413 K, Wcat = 0.15 g, H-ZSM-5 0.06 g. Reprinted from Wiley-VCH [68]...

Another current topic of high interest is the one-pot/direct transformation of cellulose into sugar alcohols such as sorbitol, xylitol, arabinitol, and glycerol via combined hydrolysis/hydrogenolysis reactions [31-33]. The combination of cellulose hydrolysis and hydrogenation can significantly improve the conversion of cellulose and prevent consecutive reactions toward undesired products. Instead, more valuable sugar alcohols (i.e., sorbitol) may be formed as important feedstock for the production of liquid transportation fuels upon their conversion into alkanes [34]. 

Light alkanes by the hydrogenolysis of sorbitol and stepwise OH-removal [24]. 

Liu et al. used the same pathway to produce hexane from cellulose. With an Ir-ReOySiO catalyst combined with a H-ZSM-5 zeolite in a biphasic system (H O—dodecane), they were able to convert ball-milled cellulose and microcrystalline cellulose to hexane in one pot with yields up to 83% and 78%, respectively [179]. The catalytic reaction proceeds via the formation of sorbitol from cellulose afterward it undergoes hydrogenolysis into hexane. Independently... 

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