ABSTRAK
Pada penelitian ini, katalis H2SO4/SiO2 dibuat dengan menggunakan metode immobilisasi sol-gel dan impregnasi pada silika gel. Katalis H2SO4/SiO2 dikarakterisasi dengan XRD, XRF, dan FTIR. Katalis yang dihasilkan diuji dengan metode leaching untuk mengetahui banyaknya asam sulfat yang terlepas dan digunakan pada reaksi esterifikasi. Persen leaching yang diperoleh dari impregnasi pada silika gel sebesar 4,78% per 0,1 g katalis dan untuk katalis solgel sebesar 7,1% per 0,1 g katalis. Berdasarkan hasil yang diperoleh, katalis solgel selanjutnya digunakan untuk reaksi esterifikasi asam-3,4,5-trihidroksibenzoat (asam galat) dan sukrosa dengan suhu 90 oC dan 110 oC, rasio mol asam galat dan sukrosa 2:3, 8:1, 9:1 dengan suhu optimum 110 oC, waktu reaksi 24 jam, 5% katalis dan pelarut DMSO. Sebelum reaksi esterifikasi, reaktan dicampur dan dipanaskan dalam oven microwave selama 4 menit dan dibandingkan dengan 10 menit. Hasil reaksi esterifikasi dianalisis menggunakan HPLC, FT-IR dan LCESI- MS dan menunjukkan sebagian besar asam galat telah bereaksi. Hasil LC-ESIMS menunjukkan hanya terbentuk monogalloyl glucose. Selanjutnya, produk ester diuji dengan metode DPPH radical scavenging dan menunjukkan bahwa ester yang dihasilkan memiliki IC50 34,68 ppm.

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ABSTRACT

In this research, the catalysts H2SO4/SiO2 were prepared by sol-gel and impregnation methods and were characterized with XRD, XRF and FT-IR. Both catalysts were tested by leaching method to determine the leaching of sulfuric acid and were used on the esterification reaction. Percent leaching of H2SO4 from the impregnated silica gel was 4.78% per 0.1 g catalyst and from the immobilized solgel was 7.1% per 0.1 g catalyst. Based on these results, sol-gel catalyst was used on the esterification reaction between 3,4,5-trihydroxyl benzoic acid (gallic acid) and sucrose at temperatures of 90oC and 110 oC, by varying the molar ratios of gallic acid/sucrose 2/3; 8/1 and 9/1 at optimum temperature of 110 oC, for 24 hours and 5% catalyst using DMSO as solvent. Prior to the esterification reaction, the reactants mixture was heated in a microvawe oven for 4 minutes compare to 10 minutes. The esterification reaction products were analyzed by HPLC, FT-IR and LC-ESI-MS and showed that almost all gallic acid was reacted. The LC-ESI-MS results indicated that only monogalloyl glucose was produced. Furthermore, the esterification product was determined by DPPH radical scavenging method and showed that IC50 from the ester was 34,68 ppm.