Mechanical deconstruction of corn stover as an entry process to facilitate the microwave-assisted production of ethyl levulinate

In this study, ball milling was applied as a pretreatment to promote the production of ethyl levulinate (EL) from corn stover under microwave irradiation. The experiments showed mechanical grinding significantly increased the EL yields by 31.23 and 23.31% at 160 and 170 °C, respectively. To further understand the influence of ultrafine grinding on alcoholysis process, we have presented a series of physicochemical and morphological analysis for the ball milled corn stover. The characterization indicated that ball milling sharply reduced the particle size to cellular scale and the intact, smooth surface changed to an open, porous structure during ball milling. It also resulted in the disruption of crystalline cellulose to amorphous state and the depolymerization of polysaccharides with an increase in reducing-ends. In general, mechanical processing approach could efficiently modify the corn stover and facilitate the EL production in the following three ways: firstly, the reduction in particle size with increased surface increased the reaction accessibility of cellulose; secondly, the destruction of compact cellulose crystal structure conduced to the reduction of alcoholysis energy barrier; moreover, the depolymerized polysaccharides resulted in the increase of the reaction sites, which further improved the reaction activity and promote EL conversion. The mechanical processing approach could well hold the key to a better use of the mechanical forces in the alcohol reaction system, providing an environment-friendly method into lignocellulosic biorefinery schemes.