Microwave heating is characterized by high efficiency and selectivity in biomass treatment. Due to the high thermal stability and low polarity of lignin, isolation of lignin by high-temperature microwave treatment is a promising subject for investigation. In this paper, microwave treatment is applied to polysaccharide liquefaction and lignin isolation from softwood at 160–210 °C for 10 min with dilute sulfuric acid. Mass balance/element analysis/FTIR/TG/solid-state 13C NMR/Py-GC/MS are applied to investigate the processed residues (residual lignin). At 190 °C processing temperature, the residual lignin is a material rich in aromatics. High lignin purity (93 wt %) and yield (82 wt %) could be achieved by a simple protocol, which usually takes days or even weeks using conventional milled wood lignin protocols. The Py-GC/MS is applied to check the structure of lignin by a newly developed approach. The liquid phase after isolation is analyzed by GC-MS and liquid carbon NMR. Most chemicals in processed liquid are from cellulose and hemicellulose, suggesting that lignin is preserved well in the residue. By comparison, we found that microwave isolation causes less lignin degradation than conventional acidolysis under equivalent conditions. It is concluded that microwave treatment is potentially a promising tool for isolation of polysaccharide-free lignin with high efficiency.Keywords: Acidolysis; Lignin; Lignocellulosic biomass; Microwave;

A systematic study of the conventional and microwave (MW) kinetics of an industrially relevant demethylation reaction is presented. In using industrially relevant reaction conditions the dominant influence of the solvent on the MW energy dissipation is avoided. Below the boiling point, the effect of MWs on the activation energy Ea and k0 is found nonexistent. Interestingly, under reflux conditions, the microwave-heated (MWH) reaction displays very pronounced zero-order kinetics, displaying a much higher reaction rate than observed for the conventionally thermal-heated (CTH) reaction. This is related to a different gas product (methyl bromide, MeBr) removal mechanism, changing from classic nucleation into gaseous bubbles to a facilitated removal through escaping gases/vapors. Additionally, the use of MWs compensates better for the strong heat losses in this reaction, associated with the boiling of HBr/water and the loss of MeBr, than under CTH. Through modeling, MWH was shown to occur inhomogeneously around gas/liquid interfaces, resulting in localized overheating in the very near vicinity of the bubbles, overall increasing the average heating rate in the bubble vicinity vis-à-vis the bulk of the liquid. Based on these observations and findings, a novel continuous reactor concept is proposed in which the escaping MeBr and the generated HBr/water vapors are the main driving forces for circulation. This reactor concept is generic in that it offers a viable and low cost option for the use of very strong acids and the managed removal/quenching of gaseous byproducts.

For the first time, brown seaweed Ascophyllum nodosum was studied as a feedstock for the production of bioethanol. Saccharification was carried out by microwave assisted acid hydrolysis. The optimal condition was 0.4 M H2SO4, 3.13% (w/v) of biomass concentration, reaction temperature at 150 °C for 1 min, resulting in 127 mg/g monosaccharides of seaweed being released. The hydrolysates solution was concentrated and fermented directly without further detoxification. The concentration of furfural, hydroxymethyfufural and phenolic in the fermentation medium were 0.00, 0.01 and 1.8 g/L, respectively. An ethanol concentration of 5.57 g/L and a conversion efficiency of 60.7% (based on glucose, galactose and mannose) were achieved. More than 50% energy yield of alga residue was recovered after hydrolysis, and the energy densification ranged from 1.4 to 1.7, with HHVs from about 19–24 MJ/kg. The findings of this study demonstrated that microwave heating is a fast and efficient way to produce sugars and biochar in one simple process. And Ascophyllum nodosum can be potentially used as a feedstock for bioethanol and biochar production.Keywords: Ascophyllum nodosum; Biochar; Bioethanol; Microwave assisted hydrolysis; Monosaccharide

A range of carbohydrates has been rapidly and selectively converted to 5-chloromethyl furfural using microwave heating in a biphasic reaction system with a range of organic solvents. Fructose and inulin were especially effective for production of this valuable bio-platform molecule, with yields of >70% obtained in 15 minutes under microwave heating. Yields from cellulose were dramatically increased with ball mill pre-treatment, this being associated with a reduction in polysaccharide crystallinity.

The waste ashes from a commercial biomass combustion facility are successfully converted into mesoporous structured silica utilising a biorefinery approach, with potential high value applications in catalysis, adsorption and separation processes. Potassium silicate solutions are formed via a simple hydrothermal extraction of miscanthus bottom ashes, rich in amorphous silica, with a reproducible extraction of 60–70%. The extension and validation of a rapid and facile infrared method for the quantification of the silicate solutions is demonstrated with important industrial applications for continuous online screening and tuning of the silicate solution ratio and concentration. The alkali solutions from the waste ashes are used for the formation of a structured high surface area mesoporous silica, MCM-41 (1043 m2 g−1, 1.12 cm3 g−1). The resulting mesoporous silica was analysed by XRD, N2 adsorption porosimetry and TEM.