Though TOF of few reported solid acid catalysts like Cs-doped heteropolyacid (0.565 min1) [40] and sulfonated single-walled nano-carbon (0.110 min1) [24] was high for the similar reaction, TOF of the SZr catalyst prepared in the present study was found to be higher (0.088 min1) as compared to reported SZr (0.031 min1) and SZr-SBA-15 (0.043 min1) catalysts [29] and also other catalysts such as sulfonated activated carbon (0.06 min1) [24], sulfonic acid-functionalized SBA-1 (0.04 min1) [41], sulfonated chitosan (0.009 min1) [18], poly(vinyl alcohol) cross-linked with sulfosuccinic acid (0.006 min1) [42], and 12-tungstophosphoric acid on niobia (0.0006 min1) [22].