Qiujuan Liu

Structural Properties of the Purified Lignins of Cornstalk in the Cooking Process with a Solid Alkali

To avoid undesired polymerization and maximize the selectivity of alkyl levulinate from the acid-catalyzed conversion of biomass-derived furfuryl alcohol, the effects of catalyst and reaction parameters on the formations of humin and alkyl levulinate were investigated. The results show that Amberlyst 15, of moderate acidic strength, was more favorable for the selective conversion of furfuryl alcohol to alkyl levulinate, and heteropolyacids of strong acidic strength tended to promote furfuryl alcohol polymerization. Compared with water as a reaction medium, alcohol significantly lowered humin formation and enhanced the yield of the resulting products. The formations of humin and alkyl levulinate were both favored at high catalyst loadings and reaction temperatures. An augmentation in initial furfuryl alcohol concentration caused an increase in humin formation and a decrease in alkyl levulinate yield. A high alkyl levulinate yield of up to 94% (100% furfuryl alcohol conversion) was achieved at 110 °C for 4 h with 5 g/L Amberlyst 15 catalyst and an initial furfuryl alcohol concentration of 0.1 mol/L. At this point, about 5% furfuryl alcohol was polymerized to form the humin, and its polymerization occurred mainly during the initial reaction stage.

Improving the efficiency of enzymatic hydrolysis of Eucalyptus residues with a modified aqueous ammonia soaking method

Abstract Eucalyptus residues from pulp mill were pretreated with aqueous ammonia soaking (AAS) method to improve the efficiency of enzymatic hydrolysis. The optimized condition of AAS was obtained by response surface methodology. Meanwhile, hydrogen peroxide was introduced into the AAS system to modify the AAS pretreatment (AASP). The results showed that a fermentable sugar yield of 64.96 % was obtained when the eucalypt fibers were pretreated at the optimal conditions, with 80 % of ammonia (w/w) for 11 h and keeping the temperature at 90 °C. In further research it was found that the addition of H2O2 to the AAS could improve the pretreatment efficiency. The delignification rate and enzymatic digestibility were increased to 64.49 % and 73.85 %, respectively, with 5 % of hydrogen peroxide being used. FTIR analysis indicated that most syringyl and guaiacyl lignin and a trace amount of xylan were degraded and dissolved during the AAS and AASP pretreatments. The CrI of the raw material was increased after AAS and AASP pretreatments, which was attributed to the removal of amorphous portion. SEM images showed that microfibers were separated and explored from the initial fiber structure after AAS pretreatment, and the AASP method could improve the destructiveness of the fiber surface.

Enzymatic Saccharification of Eucalyptus Chips with a Pretreatment Process Using NH4Cl

NH4Cl was used to optimize the pretreatment conditions for biomass pretreatment to improve enzymatic saccharification and hemicellulose degradation of eucalyptus chips. After pretreatment, the solid substrate (SS) and pretreatment liquor (PL) were characterized, and the SS was enzymatically hydrolyzed to detect the conversion yield of cellulose (CYC). For the pretreatment using NH4Cl, the removal rate of hemicellulose reached up to 100% in some cases, but a great proportion of cellulose remained in the SS. The optimized conditions for pretreatment using NH4Cl were 0.3 M NH4Cl at 200 °C for 25 min. A comprehensive evaluation found that the most suitable severity parameter for pretreatment and enzymatic saccharification was 4.5, although a higher severity parameter could increase the CYC. XRD and FTIR analysis showed that the pretreatment had little influence on the cellulose crystalline region, and the lignin was well-retained in the pretreatment process.High biomass loading is a key technique to reduce the pretreatment cost of lignocellulosic biomass. In this work, various biomass species such as bagasse, erianthus, cedar, and eucalyptus were pretreated using an ionic liquid, 1-ethyl-3-methylimidazolium acetate, at different biomass loadings, particularly focusing on a high loading region. Cellulose structural changes in pretreated biomass were investigated via X-ray scattering and 13C solid-state nuclear magnetic resonance (SSNMR) spectroscopy. The structural behaviors roughly fell into two categories, corresponding to either grassy (bagasse and erianthus) or woody (cedar and hardwood) biomass. The grassy biomass gradually transformed from cellulose-I to cellulose-II in a monotonic manner against the biomass loading. In contrast, the transformation in the woody biomass occurred abruptly as solids was decreased within the high loadings range (50 wt% to 33 wt%). Below 33 wt%, a reformation of cellulose-I from cellulose-II proceeded readily. In terms of cellulose crystallinity, erianthus as well as bagasse showed a minimum value at 25 wt% loading, whereas the crystallinity for the woody biomass did not possess such a clear minimum. Acid hydrolysis of these pretreated biomass was also conducted and the relationship between the reactivity and the cellulose structural changes was discussed.

A study of anthraquinone-fortified green liquor pretreatment of loblolly pine chips

Abstract Green liquor (GL) pretreatment for kraft pulping technologies was modified by applying anthraquinone (AQ) during the pretreatment stage. Analysis of the pulp lignin contents and final pulp yields demonstrated that the addition of AQ improved delignification selectivity. A proposed mechanism for the behavior of AQ during the GL pretreatment is that it amplifies delignification rather than preserves hemicelluloses. An analysis of the pulp carboxylic acid groups indicated that AQ did not affect the total carboxylic acid content in the pulp, but provided a lower hexenuronic acid content at a specific level of lignin content. In general, green liquor pretreatment reduces the energy requirement for pulping and improves chemical reactivity during delignification. As a result, net pulping efficiency for a kraft pulping operation can be improved.