Hydrolysis of some biopolymers with water and carbon dioxide at high pressures and temperatures

To our knowledge the hydrolysis of starch with water and carbon dioxide at elevated pressure and temperature has not yet been investigated. We have therefore carried out these experiments with the aim of optimizing the reaction conditions to obtain a maximum yield of the valuable products such as maltose, glucose and fructose. The hydrolysis of starch was performed in a tubular reactor measuring 4.02 m in length and having an inner diameter of 6 mm. Experimental conditions were such that the temperature ranged from 170 to 300 degrees C and the pressure was varied between 60 and 240 bar. An increase in the yield of products was observed when carbon dioxide was used as a catalyst. But only the dissolved and dissociated carbon dioxide has an influence on the hydrolysis of starch. The temperature is the parameter which has the strongest influence on the hydrolysis of starch in water. The glucose yield varied only little with the initial starch concentration, eventhough this was, in one case, increased by a factor of 50. The kinetic study was carried out with the assumption, that the type of all reactions are the first order. The activation energy and frequecy factor for the decomposition of starch and formation of products were calculated. We present in this article the hydrolysis of starch with carbon dioxide as catalyst as an alternative to the traditional acid catalyzed process. Comparing with the traditional acid catalyzed process the hydrolysis of starch with carbon dioxide as catalyst has the advantage, that two process units, one for neutralizing the solution and a second one for removing the resulting salt with ion exchangers, could be eliminated.