Sorbitol production with catalytic hydrogenation from glucose

Sorbitol, which constitutes 50% of the sugar alcohol market in the world and is one of the important sugar alcohols, is a commercial product used in especially in the food industry and pharmaceutical, chemical, cosmetic and other industrial fields. It is widely used as commercial sugars substitute in the food industry because of its advantages such as low calorie, non toxic, sweet taste, high solubility in water, positive effects on flavour and aroma, hygroscopic feature, stabilization and moisture, stabiliser and bulking enhancer. Although approximately 800,000 tons of sorbitol is produced every year in the world, the its production and scientific studies on this subject are extremely limited in Turkey. It has been evaluated that more research needs to be done in Turkey regarding the production of sorbitol and its use in foods, and that the production of sorbitol is an important issue in order to reduce import and external dependence. In this thesis, it was aimed to produce sorbitol by catalytic hydrogenation method using glucose and optimize the type of catalyst (ruthenium, palladium and platinum) and hydrogenation conditions (temperature, pressure and time) that are effective on sorbitol production. Limit values of independent variables for optimization of the hydrogenation process were 100-200°C for temperature, 20-60 bar for pressure and 1-5 hours for pressure, and a total of 45 production central composite design was used with response surface method by repeating the midpoint 3 times. According to the sorbitol analysis as a response result, the best catalyst type and optimum hydrogenation conditions were determined. The raw liquid obtained after hydrogenation was passed through columns containing filter and resin for refining. Colour, spectrophotometric colour density, water soluble dry matter, and electrical conductivity analyses were carried out in both raw and refined liquid for quality control. It was determined that while the catalyst type, H2 gas pressure, interaction of catalyst type and H2 gas pressure and temperature were statistically significant, the reaction time was not significant on the amount of sorbitol in hydrogenation. As a result of the 45 hydrogena-tion processes and their analyses, sorbitol production amount varied between 0.16% and 85.53% under selected design conditions and the highest sorbitol production was 85.53% in the presence of ruthenium catalyst at 150°C, 60 bar H2 gas pressure, and 1-hour reaction time. In addition, it was determined that while the colour of the hydrogenated liquid and the spectrophotometric colour density increased with the increase of temperature, the water soluble dry matter content decreased with the temperature. The electrical conductivity of samples also decreased with resin application. As a result; it was determined that optimum conditions for sorbitol production from glucose by hydrogenation was 153°C temperature, 60 bar H2 gas pressure and 1-hour reaction time in the presence of ruthenium catalyst and sorbitol was produced with an average yield of 93.30% with these optimum condition parameters.