Preparation and Application of Silica Catalyst from Geothermal Sludge for Sago Starch Hydrolysis

There has been a growing interest from scientific community to develop catalyst from alternative materials. This study has been focusing on preparing and employing solid catalyst derived from geothermal sludge (GS) as by - product material from Dieng Geothermal Power Plant (PLTPB Dieng, Indonesia) activity. The catalysts were prepared by extracting silica from the sludge material with the use of alkali solution, followed by gelling formation and acidification with sulfuric acid solution. The prepared catalyst was then applied in hydrolysis reaction to convert sago starch flour into monosaccharide of glucose. Catalyst properties were assessed of their morphology (with SEM-EDX), crystallinity (with XRD), functional group (with FTIR) and surface area (with BET). Sample analysis confirmed the produced catalyst was amorphous in general, having 127 m²/g of surface area. In addition, the prepared catalyst contained as much as 79% of silica, an increase silica fraction from that of the raw material of the sludge (silica content is 42–43%). From the catalyst activity test conducted at 100–200 °C (373–473 K) hydrolysis reaction, up to 99% conversion and 57.87% of glucose yield could be obtained from the study. Catalyst performance and stability, however might still need improvements as the catalysts experienced degradation up to 25% at the 3rd-cycle of catalyst reuse in the applied reactions.