Hydrogenation of starch

In addition, using ruthenium on an acidic support, it is possible to achieve the hydrolysis and the hydrogenation of starch or other polysaccharides into sorbitol in one sole reactor (Ui ). 

The molecular structure of cellulose, unlike that of starch, allows for strong hydrogen bonding between polymer chains. This results in the formation of strong water-resistant fibers such as those found in cotton, which is 98% cellulose. Cotton actually has a tensile strength greater than that of steel. The major industrial source of cellulose is wood ( 50% cellulose). 

By shaking a solution of ammonia and ammonium pyruvate with colloidal palladium in the presence of hydrogen, employing starch paste to stabilize the colloid. Aubel and Bourguel, Compt. rend. 186, 1844 (1928). 

V. Timme, R. Buczys, and K. Buchholz, Kinetic investigations on the hydrogenation of 3-ketosucrose, Starch Starke, 50 (1998) 29-32. 

There are several examples of one-pot reactions with bifunctional catalysts. Thus, using a bifunctional Ru/HY catalyst, water solutions of corn starch (25 wt.%) have been hydrolyzed on acidic sites of the Y-type zeolite, and glucose formed transiently was hydrogenated on ruthenium to a mixture of sorbitol (96%), mannitol (1%), and xylitol (2%) [68]. Similarly a one-pot process for the hydrolysis and hydrogenation of inulin to sorbitol and mannitol has been achieved with Ru/C catalysts where the carbon support was preoxidized to generate acidic sites [69]. Ribeiro and Schuchardt [70] have succeeded in converting fructose into furan-2,5-dicarboxylic acid with 99% selectivity at 72% conversion in a one-pot reaction... 

The etherified starch was further transformed by hydrogenation of the double bonds to yield the corresponding linear octyl groups using [RhCl(TPPTS)3] catalyst soluble in EtOH-H20 mixtures. Complete hydrogenation was obtained at 40 °C under 30 bar of H2 after 12 h using 0.8-wt.% Rh-catalyst [84]. Other catalytic transformations such as double bond oxidation and olefin metathesis could possibly be used to prepare other modified starches for various applications. 

Starch, either in the presence of amylose alone or combined in native starch, which is more difficult to redisperse. Rapid cooling of starch allows some inter- and intrachain hydrogen bonding, but also allows water molecules to be captured within the precipitating starch allowing it to be more easily redispersed (Figure 9.2). 

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