Catalyst choise and considerations in the conversion of Glucose to glycerol.

• Through the 20th century the use of glycerine has mainly been focused to the food industry, the cosmetic industry and the pharmaceutical industry. The required volumes for these industries can’t be compared with the larger bulk chemicals produced today. These low requirements together with the increased glycerine production, associated with the biodiesel production from which glycerine is a large by-product, has forced the prices down to approximately 100-150 $/tonne. This low cost crude glycerine has been an initiator for developing methods on how to convert the glycerine to more usable products. A proposed method by the company Biofuel Solutions has been to convert the glycerine into bio-LPG. With the EU directives stating that at least 10 % of the fuels in the transport sector should come from renewable sources this route may turn out favourable. This will though cause a large increase in demand as one of the few new ways to provide bio-LPG and thus increase in price, which will require new ways to produce glycerine.With a possible increased demand on glycerine a proposed route to produce glycerine is via catalytic hydrogenation of glucose to sorbitol and further catalytic hydrogenolysis of sorbitol to glycerine. The production of sorbitol from glucose is today already industrialised with large producers such as Roquette Frères, Cargill and SPI Polyols. The industrial process is historically made batch wise with low cost Raney-nickel catalyst but with the development of good selectivity catalysts with no leaching problems it is assumed that todays’ production is mainly operating with catalyst with noble metals as the active metal, such as ruthenium, in a continuous process. For the hydrogenolysis of sorbitol to glycerine a good method is rather unexplored as the hydrogenolysis is previously mostly performed with either ethylene glycol (EG) or propylene glycol (PG) as the wanted product [1]. In context with the text above it is of great interest to investigate the catalytic hydrogenolysis of sorbitol to glycerine for the further production of bio-LPG.Research made on catalytic hydrogenolysis of sorbitol is done with mostly glycols as the main products, [1]. With the still reasonable selectivity of glycerine, up to 40 % with Raney-nickel as catalyst [2], the proposed research method is similar [1-3]. The planned method performed by Biofuel-Solutions includes trials in an autoclave reactor with the catalyst dispersed in the reactant solution under hydrogen pressure of 20-100 bar and mild temperatures, 100-300 °C, and stirring in resemblance to previous research [4]. As leaching issues has been seen with Raney-nickel in the hydrogenation of glucose to produce sorbitol [5], a similar process, this behaviour is expected to require certain measures which also will be tested. Tests will also include to investigate the influence of the catalyst basicity, which seems to affect the selectivity towards glycerol positively [1,2,5].A final process of producing bio-LPG with the start from glucose is seen in Figure 1 below. In the picture a long chain of processes-steps is displayed. In the blue box the degradation of the lignocellulosic material takes place. This is then led to the fraction where glucose is required from enzymatic hydrolysis. In the grey box to the right the glycerol conversion to LPG is shown, a multi process-step of which most details are already known within the company. 

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering (hsv//eng)

Nyckelord

Conversion of glycose

glycerol

biofuel

Green LPG

propane

Bioenergy Technology

Bioenergiteknik/Energi- och Miljöteknik

Publikations- och innehållstyp

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