Simultaneous Extraction of Carboxylated Celulose Nanocrystals and Nanofibrils via Citric Acid Hydrolysis--A Sustainable Route

In this study, cellulose nanocrystals(CNC) with surface carboxylic groups were prepared from bleached softwood pulp by hydrolysis with concentrated citric acid at concentrations of 60 wt%~80 wt%. The solid residues from acid hydrolysis were collected for producing cellulose nanofibrils(CNF) via post high-pressure homogenization. Citric acid could be easily recovered after hydrolysis reactions through crystallization due to its low water solubility or through precipitation as a calcium salt followed by acidification. Several important properties of CNC and CNF, such as dimension, crystallinity, surface chemistry, thermal stability, were evaluated. Results showed that the obtained CNC and CNF surfaces contained carboxylic acid groups that facilitated functionalization and dispersion in aqueous processing. The recyclability of citric acid and the carboxylated CNC/CNF give the renewable cellulose nanomaterial huge potential for a wide range of industrial applications. Furthermore, the resultant CNC and CNF were used as reinforcing agents to make sodium carboxymethyl cellulose(CMC) films. Both CNC and CNF showed reinforcing effects in CMC composite films. The tensile strength of CMC films increased by 54.3% and 85.7% with 10 wt% inclusion of CNC and CNF, respectively. This study provides detailed information on carboxylated nanocellulose prepared by critic acid hydrolysis; a sustainable approach for the preparation of CNC/CNF is of significant importance for their various uses.

Aromatization and isomerization of methylcyclohexane over Ni catalysts supported on different supports

In this work, nickel metal supported on different supports(SiO_2, Al_2O_3, ZSM-5) were prepared by spraying nickel nitrate on the supports and calcined at 873 K. Then, they were characterized by XRD, XRF, N_2 adsorption–desorption, NH_3-TPD, MCH-TPD, H_2-TPR, and pyridine-FTIR,and tested as catalysts for the dehydrogenation aromatization and isomerization of methylcyclohexane(MCH) under the conditions of S-Zorb catalytic adsorption desulfurization(T ? 673 K, P ? 1.5 MPa, WHSV ? 5 h^(-1)). The H2-TPR results showed that the interaction of NiO with support decreased in the order of NiO/ZSM-5-Fe < NiO/ZSM-5 < NiO/Al_2O_3< NiO/SiO2. The decrease of the interaction appeared to facilitate the reduction of Ni and therefore to promote the dehydrogenation aromatization of MCH.It was found that a direct correlation existed between the gasoline components yields, cracking activity and the total number of different supports acid sites measured by NH_3-TPD tests. Higher total acidity of ZSM-5 resulted in gasoline loss because of higher cracking activity of MCH. The number of total acid sites of NiO/ZSM-5-Fe decreased and the medium strong Br€onsted acid sites necessary for MCH isomerization increased after the modification of ZSM-5 by iron metal. So, NiO/ZSM-5-Fe exhibited enhanced MCH conversion, aromatic and isomerization yields when compared to NiO/ZSM-5 and other Ni-based catalysts. This study shows that NiO/ZSM-5-Fe catalyst may be possible to be integrated into the S-Zorb system achieving the recovery of the octane number of gasoline.

Sustainable preparation and characterization of thermally stable and functional cellulose nanocrystals and nanofibrils via formic acid hydrolysis

In this work,a sustainable method to prepare functional cellulose nanocrystals(CNCs)and cellulose nanofibrils(CNFs)using formic acid(FA)(a recoverable organic acid)was established.After FA hydrolysis,the obtained CNCs could be well dispersed in DMAC.Thus,the CNC products and fibrous cellulosic solid residue(FCSR)in DMAC could be easily separated by a conventional centrifugal process,and the collected FCSR could be further fibrillated to CNFs with relatively low-intensity mechanical fibrillation process.The isolated CNC products showed high crystallinity index(about 75%)and excellent thermal stability(with onset thermal degradation temperature of 325℃).Both the resultant CNCs and CNFs showed better dispersibility in DMSO,DMF and DMAC respectively because of the introduction of ester groups on the surface of the products.The presence of surface ester groups could increase the interface compatibility of nanocelluloses with polymeric matrices and enable their applications in reinforcing polymeric matrix materials(e.g.the composite films like PHVB+CNFs).

Ameliorated enzymatic saccharification of corn stover with a novel modified alkali pretreatment

Enzymatic saccharification/hydrolysis is one of the key steps for the bioconversion of lignocelluloses into sustainable biofuels.In this work,corn stover was pretreated with a novel modified alkali process(NaOH+anthraquinone(AQ)+sodium lignosulfonate(SLS)),and then enzymatically hydrolyzed with an enzyme cocktail(cellulase(Celluclast 1.5L),β-glucosidase(Novozyme 188)and xylanase(from thermomyceslanuginosus))in the pH range of 4.0-6.5.It was found that the suitable pH for the enzymatic saccharification process to achieve a high glucan yield was between 4.2 and 5.7,while the appropriate pH to obtain a high xylan yield was in the range of 4.0-4.7.The best pH for the enzymatic saccharification process was found to be 4.4 in terms of the final total sugar yield,as xylanase worked most efficiently in the pH range of 4.0-4.7,under the conditions in the study.The addition of xylanase in the enzymatic saccharification process could hydrolyze xylan in the substrates and reduce the nonspecific binding of cellulase,thus improving the total sugar yields.

Recent progress on the pretreatment and fractionation of lignocelluloses for biorefinery at QIBEBT

Pretreatment and fractionation are amongst the key steps for the conversion of lignocelluloses to sustainable biofuels,biomaterials or biochemicals,as pretreatment/fractionation can break the natural recalcitrance of lignocelluloses,improving the conversion efficiency of downstream processes.This paper reviews the recent progress on the pretreatment and fractionation of lignocelluloses for biorefinery at the Chinese Academy of Sciences-Qingdao Institute of Bioenergy and Bioprocess Technology(QIBEBT).The main technologies developed at the QIBEBT in recent years include alkaline twin-screw extrusion pretreatment,modified alkali pretreatment,hydrogen peroxide-assisted sodium carbonate pretreatment,fractionation with formic acid,as well as the two-step fractionation by hot water treatment coupling ammonium sulfite treatment.With the development of these technologies,a pilot scale platform for the pretreatment and saccharification of biomass has been established in the pilot plant of QIBEBT.