Effect of metal salts existence during the acid-catalyzed conversion of glucose in methanol medium

• Catalytic effect of various metal salts as co-catalyst of sulfuric acid was examined.
• The reaction selectivity is a clear function of the type of metal salts.
• The major product was methyl glucoside in the presence of K2SO4 or Na2SO4.
• For Fe2(SO4)3 and Al2(SO4)3, methyl levulinate was formed in the highest yields.
• Alkali metal sulfates can suppress methyl glucoside isomerize to methyl fructoside.

Catalytic effect of various metal sulfates as co-catalyst of extremely low sulfuric acid on glucose conversion in methanol medium was examined. The typical pathways included the alcoholysis of glucose into methyl glucoside and methyl levulinate, the formation of humin-type polymer from glucose or its degradation products, and the dehydration of methanol medium to dimethyl ether. The reaction selectivity is a clear function of the type of metal sulfates. Both K2SO4 and Na2SO4 can effectively suppress the further transformation of methyl glucoside from glucose, thus lower the polymer formation. For Fe2(SO4)3 and Al2(SO4)3, methyl levulinate was formed in the highest yields.

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