Abstract:Alcoholysis liquefaction synthesis of levulinate esters from crop residues has attracted extensive attentions in recent years. However, the natural dense structures of biomass have become a key obstacle to the efficient use of straw for levulinate production. Ball milling is a new way of mechanical pretreatment which can effectively damage the recalcitrance of biomass and promote the availability in conversion and utilization. Ball milling can increase the production of ethyl levulinate significantly.Sulfuric acid, phosphoric acid, p-toluene sulfonic acid, Al2(SO4)3 have been applied for the conversion of biomass to ethyl levulinate. The results showed that the stronger the acidity of the catalyst was, the better the catalytic effect was under the same H+ concentration. Sulfuric acid was found to be highly active compared with other three catalysts under identical reaction conditions. And the acidity strength in sequence was sulfuric acid, p-toluene sulfonic acid, Al2(SO4)3 and phosphoric acid. The milling time had the most obvious effect on the yield of ethyl levulinate. Elevated miling time can contribute to the enhancement of reaction rate and conversion efficiency. However, the effect of filling rate and volume ratio of the spheroids on the yield of ethyl levulinate was not significant. Furthermore, based on the yield of ethyl levulinate, the optimal ball milling process was as follows: non-catalyst ball milling, 60min of the milling time, 35% of the filling rate, 2 of the volume ratio of spheroids, under this ball-milled condition,the yield of ethyl levulinate was increased from 20.08%(unmilled sample) to 33.34% (milled sample). The research result can provide some references for the production of ethyl levulinate from mechano-catalysis grinding of biomass.
