• Energy Research

The understanding of lignin softening and pyrolysis is important for developing lignocellulosic biorefinery in order to produce carbon fibers, polymers additives, green aromatics, or biofuels. Protobind lignin (produced by soda pulping of a wheat straw) was characterized by thermogravimetry, calorimetry (for glass transition temperature and heat of pyrolysis reactions), in situ 1H NMR (for the analysis of the mobility of protons upon lignin thermal conversion), and solution-state 13C and 31P NMR (determination of functional groups in lignin). In situ rheology reveals the real-time viscoelastic behavior of lignin as a function of temperature. Upon heating, lignin undergoes softening, through glass transition overlapped with depolymerization, and is followed by the solidification of the softened material by cross-linking reactions. The lignin residues were quenched within the rheometer at the midpoint temperatures of softening and solidification regions and were further analyzed by elemental analysis, GPC-U...

Abstract Rapeseed straws are recoverable lignocellulosic biomass for second generation bioethanol production. Therefore, a pretreatment step is recommended in order to increase accessibility of enzymes to sugars. As a pretreatment step in this study, several innovative technologies have been performed in order to investigate their efficiency for delignification and enzymatic hydrolysis purposes: microwaves (MW), high voltage electrical discharges (HVED) and ultrasounds (US). As a key processing parameter, different levels of energy input were studied MW (1832–7328 kJ/kg), US (916–3664 kJ/kg) and HVED (204–814 kJ/kg) corresponding to a treatment duration range of 10–40 min. Treatment temperature (60–90 °C) and medium alkalinity (0.125–0.5 M) impact was also investigated and optimized based on sugar and soluble lignin contents in black liquor, and lignin removal yields. Delignification yields increased from 28.3%, 28.6% and 31.2% for 10 min of treatment to 38.4%, 41.5% and 42.3% for 40 min of treatment, respectively for MW, US and HVED. However, in order to achieve the same efficiency the energy required by HVED is 9 times and 4.5 times less than that required by MW and US respectively. Treatment temperature also revealed to be important as sugars yields increased by 41.6% when temperature increased from 60 °C to 90 °C for HVED and the optimal medium alkalinity was found to be 0.3 M. Finally, better enzymatic hydrolysis yields were obtained and correlated to better delignification performances improving material accessibility.

Three processes for the pretreatment of Miscanthus x Giganteus were compared, namely, dilute sulphuric acid treatment, an ethanol organosolv treatment and a two-step protocol involving a presoaking step prior to the ethanol organosolv treatment. The pretreatment assays were evaluated and compared on the basis of their Combined Severity factors. It was shown that the organosolv processes permitted an efficient removal of both lignin and hemicelluloses from the solid residue. A presoaking step prior to an organosolv process performed at low severity permitted to enhance the removal of lignin and hemicelluloses and the recovery of hemicellulose sugars.

AbstractThe thermochemical conversion of lignocellulosic biomass feedstocks offers an important potential route for the production of biofuels and value‐added green chemicals. Pyrolysis is the first phenomenon involved in all biomass thermochemical processes and it controls to a major extent the product composition. The composition of pyrolysis products can be affected markedly by the extent of softening that occurs. In spite of extensive work on biomass pyrolysis, the development of fluidity during the pyrolysis of biomass has not been quantified. This paper provides the first experimental investigation of proton mobility during biomass pyrolysis by in situ 1H NMR spectroscopy. The origin of mobility is discussed for cellulose, lignin and xylan. The effect of minerals on cellulose mobility is also investigated. Interactions between polymers in the native biomass network are revealed by in situ 1H NMR analysis.

Enzymatic pre-hydrolysis using the industrial enzymatic cocktail Cellulyve® was assessed as a first step in a pretreatment process of Miscanthus biomass involving an aqueous-ethanol organosolv treatment. (13)C and (31)P Nuclear Magnetic Resonance and size exclusion chromatography were used to analyze the cellulose and lignin before and after treatment. It was demonstrated that despite a very low impact on the fibre structure (observed by Scanning Electron Microscopy) and composition (in terms of sugars and polyphenolics content), the enzymatic pre-treatment disrupted the lignocellulosic matrix to a considerable extend. This weakening permitted enhanced removal of lignin during organosolv pulping and increased hydrolysability of the residual cellulosic pulp for the production of monomeric glucose. Using this combined treatment, a delignification yield of 93% and an enzymatic cellulose-to-glucose conversion of 75% were obtained.

Eucalyptus Globulus (EG) is a virtually untapped forest source that belongs to the hardwood family. The objective of this research is to understand the effect of two different isolation techniques, i.e., kraft and organosolv procedures, followed by either acidified sodium chlorite or alkaline hydrogen peroxide treatment on the properties of cellulose and microcrystalline cellulose (MCC) derived from EG. The MCC samples were successfully prepared from cellulose via acid hydrolysis. A comparative study was carried out on the extracted cellulose fibers and MCC samples through deep characterizations of lignocellulosic content, functional groups, crystallinity, thermal properties, and surface morphology. The detailed analyses exhibited that the prepared MCC samples using various approaches are similar to those of commercial MCC. It is revealed that the organosolv treatment followed by acidic bleaching provides the purest MCC with good thermal features, where the obtained cellulose has a glucose content of more than 97% and a degradation temperature of around 343 °C. The present work provides new insight into the effect of various extraction procedures on EG-MCC; these procedures are expected to be used in different industrial applications such as in biorefinery, dietary food, packaging, films, or reinforcement of polymer matrices.

Sustainable polymers are emerging fast and have received much more attention in recent years compared to petro-sourced polymers. However, they inherently have low-quality properties, such as poor mechanical properties, and inadequate performance, such as high flammability. In general, two methods have been considered to tackle such drawbacks: (i) reinforcement of sustainable polymers with additives; and (ii) modification of chemical structure by architectural manipulation so as to modify polymers for advanced applications. Development and management of bio-based polyurethanes with flame-retardant properties have been at the core of attention in recent years. Bio-based polyurethanes are currently prepared from renewable, bio-based sources such as vegetable oils. They are used in a wide range of applications including coatings and foams. However, they are highly flammable, and their further development is dependent on their flame retardancy. The aim of the present review is to investigate recent advances in the development of flame-retardant bio-based polyurethanes. Chemical structures of bio-based flame-retardant polyurethanes have been studied and explained from the point of view of flame retardancy. Moreover, various strategies for improving the flame retardancy of bio-based polyurethanes as well as reactive and additive flame-retardant solutions are discussed.

Abstract In this study, ethanol organosolv pretreatment was investigated and optimized for the pretreatment of empty palm fruit bunch using (1) response surface methodology based on three-variable central composite design and (2) the combined severity parameters. The reaction parameters studied were sulfuric acid concentration (0.5–2.0%), reaction temperature (160–200 °C) and residence time (45–90 min). Both models provide valuable and complementary informations: using combined severity parameters, very good predictions were obtained concerning xylan and lignin extraction whereas central composite design is the best model for glucose production. The optimal values of the variables were as the followings: sulfuric acid 2.0% w/w, 160 °C, 78 min and the experimental values (96.0%) concerning glucose and lignin recovery were in excellent agreement with the central composite design prediction (100%).

Miscanthus represents a key candidate energy crop for use in biomass‐to‐liquid fuel‐conversion processes and biorefineries to produce a range of liquid fuels and chemicals; it has recently attracted considerable attention. Its yield, elemental composition, carbohydrate and lignin content and composition are of high importance to be reviewed for future biofuel production and development. Starting from Miscanthus, various pre‐treatment technologies have recently been developed in the literature to break down the lignin structure, disrupt the crystalline structure of cellulose, and enhance its enzyme digestibility. These technologies included chemical, physicochemical, and biological pre‐treatments. Due to its significantly lower concentrations of moisture and ash, Miscanthus also represents a key candidate crop for use in biomass‐to‐liquid conversion processes to produce a range of liquid fuels and chemicals by thermochemical conversion. The goal of this paper is to review the current status of the technology for biofuel production from this crop within a biorefinery context.