Chemical Modification Of Enzymatic Hydrolysis Lignin Residue And Their Adsorption Of Furfural,5-hydroxymethyl Furfural And Vanillin

Lignocellulose is the most abundant renewable biomass resource on the earth.Producing ethanol and other chemicals from lignocellulose has become an importantpathway to release energy and resources crisis in the future. During the production offuel ethanol from lignocellulose by enzymatic hydrolysis and fermentation, the acidpretreatment method is simple, efficient and low-cost, but its pretreatmenthydrolysates not only contain sugar, but also contain fermentation inhibitors such asfurfural,5-hydroxylmethyl furfural (5-HMF) and vanillin etc. Therefore, pretreatmenthydrolysates should be detoxified before fermentation. Adsorption method is simpleand easy to realize. Treatment with the porous adsorption resin and activated carboncan remove inhibitors (phenols and furfurals) effectively, but their desorption processis complicated and high-cost.The enzymatic hydrolysis lignin (EHL), which is the byproduct of the largestcellulosic ethanol plant based using corn stover as feedstock, was used as anadsorbent to remove inhibitors in this study. The influences of adsorption time andsolid-liquid ratio on the adsorption of furfural and5-HMF by EHL were investigated.Sulfonated enzymatic hydrolysis lignin (SEHL) and hydroxymethyl enzymatichydrolysis lignin (HEHL) was synthesized from EHL by chemical modification. Thenthe influences of the initial concentration, temperature, pH and ionic strength etc. onadsorption of furfural,5-HMF and vanillin by EHL, SEHL and HEHL were separatelyinvestigated. Moreover, EHL, SEHL and HEHL were applied to remove furfural,5-HMF and vanillin in DA pretreatment hydrolysates (DA hydrolysates) and SPORLpretreatment hydrolysates (SPORL hydrolysates) as adsorbents. Interaction betweenfurfural adsorption and5-HMF adsorption on HEHL was studied.The results showed that the order of adsorption capacity of inhibitors (furfural、5-HMF and vanillin) was HEHL> SEHL> EHL. With the increase of initialconcentration, adsorption capacity of inhibitor (furfural,5-HMF and vanillin) byadsorbent (EHL, SEHL and HEHL) increased. The adsorption isotherms of furfural， 5-HMF and vanillin on three enzymatic hydrolysis lignins were found to followFrendlich model well. Adsorption of furfural,5-HMF and vanillin by the EHL, SEHLand HEHL were exothermic. When pH increased from1to10, the removal ratio offurfural and vanillin was maximum at pH=6and pH=7, respectively. The adsorptionof5-HMF was relatively constant at the range of pH used in the study. Adsorptionamount of furfural,5-HMF and vanillin by EHL, SEHL and HEHL increased with saltconcentration range of0~500mM.The order of adsorption capacity of inhibitor (furfural,5-HMF and vanillin) inDA and SPORL hydrolysates was HEHL> SEHL> EHL. The removal ratio of furfural，5-HMF and vanillin in DA hydrolysates by HEHL is21.5%,9.7%and70.1%,respectively. In SPORL hydrolysates, the removal ratio of furfural，5-HMF andvanillin by HEHL is26.1%,17.8%and73.2%, respectively. There is littleinterference between the furfural adsorption amount and the5-HMF adsorptionamount on HEHL. It indicated that adsorption sites of furfural and5-HMF by HEHLwere different.Although the removal ratios of furfural and5-HMF by EHL are lower than thatby the porous adsorption resin or activated carbon, EHL is an alternative to removeinhibitors in acid pretreatment hydrosates by adsorption because it is abundant,low-cost as a byproduct of the downstream process, meanwhile the lignin afteradsoption can be used to burn to gain heat without desorption.