Sulfuric Acid-Activated Indonesian Natural Bentonite as Solid Acid Catalysts in Microwave-Protocol Nitrobenzene Synthesis

Research has been conducted on activating Indonesian natural bentonite using sulfuric acid to produce solid acid catalysts for nitrobenzene synthesis in a batch microwave reactor that is in line with green chemistry principles. Indonesian natural bentonite was refluxed with sulfuric acid at various concentrations of 0, 1, 2, 3, and 4 M, followed by calcination with N2 gas flow to obtain NB, SNB-1, SNB-2, SNB-3, and SNB-4. The results showed that activation of natural bentonite by sulfuric acid can change its physochemical properties. SNB-2 (sulfated natural bentonite 2 M) is the best catalyst with the highest acidity value compared to other concentration variations. The synthesis of nitrobenzene was carried out in an 800-watt microwave oven at 60 °C for 2.5 hours with stirring at 600 rpm. We obtained the highest benzene conversion of 33.6% over the SNB-2 catalyst with nitrobenzene selectivity of 100%. Sulfuric acid-activated bentonite has good stability for three consecutive runs, so in the future, we can apply this material as a catalyst candidate for the greener nitrobenzene industry.