Promotion of biomass pyrolytic saccharification and lignin depolymerization via nucleophilic reagents quenching of the carbonium ions.

The condensation of lignin under acidic conditions inhibited the subsequent value-added utilization of lignin, and the condensed lignin covered the biomass surface. Here, a method of benzenesulfonic acid pretreatment combined with nucleophilic reagents promoted pyrolytic saccharification and lignin hydrogenation was reported. The anhydrosugar content in the pyrolysis bio-oil increased from 66.91% to 69.00%, 72.88%, and 72.16% via adding methanol, propionaldehyde, 3-hydroxylic-2-naphthoic acid, respectively. The characterization of the biomass surface structure and the calculation of bond lengths indicated that carbonium ions prefer to bind with the added nucleophilic reagent rather than the lignin fragment. Furthermore, the quenching of the carbonium ions preserved the ß-O-4 bond, as demonstrated in 2D NMR. In the subsequent hydrogenation reaction, it was found that methanol facilitated the production of lignin monomer. The calculation also revealed that the quenching of the carbonium ions with methanol reduced the bond-breaking energy of the ß-O-4 bond.

Hydrothermal and photocatalytic synergistic pretreatment to improve the full utilization of corn stalk.

In this study, the hydrothermal and photocatalytic synergistic pretreatment for improving the full component utilization of corn stalk based on lignin first biorefining was employed to generate carbohydrates and obtain modified lignin. The results showed that the highest lignin removal ratio (40.70 %) and cellulose retention ratio (92.64 %) were obtained due to the smallest energy gap (6.05 eV) and the largest penetration distance (1.73 Å) between GVL and the lignin. And the yield of carbohydrates increased from 1.95 % to 58.17 % after hydrothermal pretreatment at 180 ℃. Furthermore, the modified lignin enhanced the flocculation effect, resulting in the increase of the removal of safranine-T by 6 times. In addition, the chemical and physical properties of modified lignin were studied and the mechanism of photocatalysis modification was explored. The research provides a new pretreatment method for the utilization of biomass and simultaneously achieves carbohydrate enrichment in bio-oil and purification of dye wastewater.

N,N-Dimethylformamide solvent assisted hydrothermal pretreatment of Chlorella for coproduction of sugar, nitrogenous compounds and carbon dots.

Microalgae are considered as a promising alternative to fossil fuels due to their ease of cultivation, short growth cycle and no occupation of cultivated land. In this study, N,N-Dimethylformamide (DMF) solvent was employed to assist hydrothermal pretreatment of Chlorella for coproduction of sugar, nitrogenous compounds and carbon dots (CDs). The effect of pretreatment conditions on the composition and pyrolysis bio-oil distribution of hydrothermal solid residues as well as CDs characteristic were investigated by varying the temperature (180-220 ℃) and reaction time (1-9 h). The results showed that pretreated residues had higher cellulose. And the yield of sugar and N-contained compounds reached 41.59% and 63.57% in the pyrolysis bio-oil of pretreated algae residues, respectively. Moreover, CDs obtained from hydrothermal solution fluoresced red under 365 nm excitation. The paper provides a new method for the complete utilization of microalgae.

Boosting levoglucosan and furfural production from corn stalks pyrolysis via electro-assisted seawater pretreatment.

The seawater electrochemical pretreatment (ECP) was employed to upgrade the bio-oil of corn stalk in the paper. The seawater and its simulants were used as electrolytes without additional reagents. Moreover, the effect of seawater ECP under different conditions on the products distribution of pyrolysis bio-oil of pretreated corn stalks was investigated. The results showed that pretreatment effectively deconstructed the lignin and made cellulose exposed. Especially, under the optimum conditions (3.5 wt% NaCl, 15 V and 4 h), most of lignin was destroyed, and cellulose and hemicellulose were remained in residual solids. Furthermore, the levoglucosan and furfural were enriched in the pyrolysis bio-oil of corn stalk after seawater ECP, reaching 23.22 % and 14.14 %, respectively. Overall, this work presented a novel and green pretreatment process to optimize the components and structure of corn stalks as well as upgrade the bio-oil of corn stalk pyrolysis.

Enhancing Hydrodeoxygenation of Bio-oil via Bimetallic Ni-V Catalysts Modified by Cross-Surface Migrated-Carbon from Biochar.

Aromatics from selective hydrodeoxygenation (HDO) of biomass-derived bio-oil are an ideal feedstock for replacing industrial fossil products. In this study, biochar-modified Hß/Ni-V catalysts were prepared and tested in the atmospheric HDO of guaiacol and bio-oil to produce aromatics. Compared with unmodified Hß/Ni-V, higher HDO activity was achieved in catalysts with all kinds of biochar modifications. Especially, the pine nut shell biochar (PB)-modified PB-Hß-8/Ni-V showed the highest selectivity to aromatics (69.17%), mainly including benzene and toluene. Besides, under the conditions of 380 °C and weight hourly space velocity (WHSV) of 0.5 h-1, the cleavage of CAr-OH (CAr means the carbon in the benzene ring) was promoted to form more aromatics. Moreover, great recyclability (58.77% aromatics for the reactivated run-3 test) and efficient HDO of bio-oil (44.9% aromatic yield) were also achieved. Based on the characterization results, the enhanced aromatic selectivity of PB-Hß-8/Ni-V was attributed to the synergetic effect between PB and Hß/Ni-V. In detail, a stable surface migrated-carbon layer was formed on Hß/Ni-V via the metal catalytic chemical vapor deposition (CVD) process of the pyrolysis PB volatiles. Simultaneously, a carbothermal reduction driven by the migrated-carbon took place to decorate the surface metals, obtaining more Ni0 and V3+ active sites. With this synergism, increased Ni0 sites promoted H2 adsorption and dissociation, which improved the hydrogenation activity. Furthermore, the higher affinity of the reactant and increased oxygen vacancies both contributed to enhancing the selective surface adsorption of oxygenous groups and the cleavage of the CAr-OH bond, thus improving the deoxygenation activity. Therefore, the HDO activity was improved to form more target aromatics over biochar-modified catalysts. This work highlighted a potential avenue to develop economic and environmental catalysts for the upgrading of bio-oil.

The influence of torrefaction on pyrolysed biomass: The relationship of bio-oil composition with the torrefaction severity.

In this study, three types of biomass were torrefied at different times (0.5, 1, 1.5 h) and temperature (200, 240, 280, 320 °C), which were further pyrolyzed at 550 °C after torrefaction. CEI (carbon element index), which was established based on the carbon content of the torrefied biomass, was chosen as an indicator for reflecting torrefaction severity. The results showed that there was a curvilinear relationship between CEI and the physicochemical characteristics, energy recovery of torrefied biomass, which obtained an average goodness of fit was higher than 0.93. Moreover, the goodness of fit between CEI and pyrolysis carbon and bio-oil yield was higher than 0.95 and 0.91, respectively. Especially, the bio-oil composition and CEI were fitted by a quadratic function (y = a + bx + cx2). Based on the function, the yield of phenols could be predicted based on the CEI value, which would benefit for the preparation of higher quality bio-oil directionally.

High yield self-nitrogen-oxygen doped hydrochar derived from microalgae carbonization in bio-oil: Properties and potential applications.

In this work, the high yield self-N-O doped hydrochar had been prepared through the hydrothermal carbonization of microalgae in the aqueous bio-oil. The effects of temperature, residence time and the ratio of Chlorella and bio-oil on the solid yield were investigated. The results showed that the hydrochar had excellent thermal stability and abundant nitrogen and oxide functional groups, its solid yield reached 199.33%. After activated by KOH at high temperature, the hydrochar was transformed into a porous carbon material with high nitrogen content. The porous carbon showed high CO2 absorption of 5.57 mmol/g at 0 °C and 1 bar. It also exhibited a high specific capacitance of 216.6F/g at 0.2 A/g and a good electrochemical stability with 88% capacitance retention after consecutive 5000 cycles.

Influence of biomass components, temperature and pressure on the pyrolysis behavior and biochar properties of pine nut shells.

The aim of this work was to compare the yields, proximate composition, structure and surface morphology of biochar derived from lignin, cellulose, hemicellulose and pine nut shell (PNS) at 400-700 ℃. PNS biochars obtained at different pyrolysis pressures in the range of 0.1-2.0 MPa were also studied. The results indicate that the interactions of lignin, cellulose and hemicellulose have smaller effects on the ash content, yield and higher heating value (HHV) of the biochar than they do on the fixed carbon and volatile matter contents. Increasing the pyrolysis temperature improves the HHV of the biochar, and increasing the pyrolysis pressure enhances the biochar yield, surface functional groups and combustion characteristics. The kinetic data for Pb2+ adsorption are best fitted by a pseudo-second-order model, indicating a chemisorption-controlled process. The PNSB550 and PNSB1.0 data are optimally fit by the Freundlich and Langmuir models, respectively. The maximum Pb2+ adsorption capacity is 237.3 mg/g.

Prediction Method for Torrefied Rice Husk Based on Gray-scale Analysis.

Torrefaction pretreatment has recently gained attention for the potential improvement in biomass properties. Otherwise, visible image-processing technology for analyzing properties of torrefied biomass was evaluated for possible use in the future online process control. In this study, torrefied rice husk from different torrefaction temperatures (180-330 °C) was obtained. After torrefaction, the biochar was characterized to determine the effects of torrefaction temperature on the properties, including the proximate analysis, solid yield (SY), and higher heating values. In addition, the color values, including red-green-blue (RGB) values, and grayscale (GS) of torrefied rice husk, were measured. The results show that the fixed carbon and ash increased from 17.39 to 35.13 and 7.06 to 38.41%, respectively, while volatile matters decreased from 71.47% to a minimum of 22.89% with the increase of torrefaction temperature from 105 to 330 °C. The SY remained higher than 46% even at the most severe torrefaction condition because of the high ash content and high remaining lignin. Moreover, the higher heating values of torrefied rice husk were increased from 14.80 to 17.82 MJ/kg when increased the pretreatment temperature. RGB values were decreased with the increase of torrefaction temperature. The GS analysis results show that the color of torrefied rice husk changed from yellow to brown at light torrefaction and black at severe torrefaction. GS of torrefied rice husk shows a good correlation (R = 0.9998) with torrefaction temperature. Prediction equations with higher fitting degree between GS and proximate analysis (R 2 > 0.9900), high heat values (R 2 = 0.9999), and SY (R 2 = 0.9979), which are developed to reflect the changing characteristics of torrefied rice husk. The results show that the prediction method based on GS is a promising technology to measure the properties of torrefied rice husk.

Improvement of corn stover fuel properties via hydrothermal carbonization combined with surfactant.

BACKGROUND: Biomass fuel has been used to supply heat or crude materials in industry to replace the traditional fossil fuel which was one of the chief causes of climate warming. However, the large-scale utilization of biomass fuel was restricted due to the low density and high hydrophilicity of biomass, which causes the problem of transportation and storage. Therefore, pelletization of biomass was used to improve its fuel density. At present, the biomass pellet was widely used to supply heat, gas or electricity generation via gasification, which supplied clean and sustainable energy for industry. However, the energy consumption during pelletization and high hydrophilicity of pellets were still the problem for the large-scale application of biomass pellet. In this study, hydrothermal carbonization and surfactant played the role of permeation, adsorption and wetting in the solution, which was expected to improve the fuel properties and pelletization effectivity of corn stover. RESULTS: In the article, surfactant (PEG400, Span80, SDBS) was chosen to be combined with wet torrefaction to overcome the drawbacks and improve the pelletization and combustion properties of Corn stover (CS). Especially, hydrothermal carbonization (HTC) combined with surfactant improves the yield of solid products and reduces the ash content of solid product, which was beneficial for reducing the ashes of furnace during gasification. Meanwhile, surfactant promotes the formation of pseudo-lignin and the absorption for oil with low O and high C during HTC, which improves the energy density of solid product. Furthermore, the oil in solid product plays the role of lubricant and binder, which reduces the negative effect of high energy consumption, low bulk density and weak pellets strength caused by HTC during pelletization. HTC combined with surfactant improved the hydrophobicity of pellet as well as grindability due to the modification of solid product. Moreover, surfactant combined with HTC improved the combustion characteristic of solid product such as ignition and burning temperature as well as kinetic parameters due to the bio-oil absorbed and the improvement of surface and porosity. CONCLUSIONS: The study supplied a new, less-energy intensive and effective method to improve the pelletization and combustion properties of corn stover via hydrothermal carbonization combined with surfactant, and provided a promising alternative fuel from corn stover .

The correlation of physicochemical properties and combustion performance of hydrochar with fixed carbon index.

Hydrothermal carbonization (HTC) is effective method for improving fuel properties of biomass. Investigating the relationship between the HTC severity and the physicochemical properties of hydrochar is beneficial for the large-scale utilization. The fixed carbon index (FCI) based on the hydrothermal carbonization severity is introduced to predict the physicochemical properties, pelletization and combustion performance of hydrochar. The results showed the relationship between decarbonization, dehydrogenation, deoxygenation and FCI fits exponential function. It was predicted that the hydrochar pellets with FCI = 0.15-0.45 possessed the highest bulk density (>1175 kg/m3), the lowest specific energy consumption (<16.07 kJ/kg) and the strongest radial compressive strength (>10.7Mpa). Moreover, the activation energy of hydrochar combustion in FCI (0.15-0.25) is higher (the maximum is 216 kJ/mol). The study provides based datas for predicting the fuel properties of hydrochar and obtains high quality solid fuel.

The mechanism of wet/dry torrefaction pretreatment on the pyrolysis performance of tobacco stalk.

In this work, the influence of dry/wet torrefaction with additives on the pyrolysis performance was investigated. The results showed that the content of phenols and ketones (62% and 42%) was improved and the content of acids decreased from 35% to 4% due to the increase of lignin content in torrefied char. Moreover, the content of aromatic hydrocarbon reached 22%. The mechanism showed that the conversion of "CO/CO" into states of "aromatic CC/CC", the removal of hemicellulose and the formation of pseudo-lignin during wet/dry torrefaction were the key factors for the enrichment of aromatic hydrocarbon. The research supplied an effective and original method for obtaining high value aromatic chemicals from the agricultural and forestry waste via the wet/dry torrefaction pretreatment combining with pyrolysis.

Torrefaction performance of camellia shell under pyrolysis gas atmosphere.

In order to complete using the pyrolysis gas and heat from biomass routine pyrolysis, the camellia shell was torrefied under PG atmosphere. And the chemical and physical properties of torrefied char obtained under N2 and pyrolysis gas were compared as well as the pyrolysis and combustion performance. Moreover, in order to investigate the mechanism of pyrolysis gas torrefaction, the influence of each composition such as H2, CO2 and CH4 in pyrolysis gas on the torrefaction performance was also been studied. The results show pyrolysis gas improves the volatile matter content and heat value of the torrefied char. Moreover, pyrolysis gas promotes the degradation of cellulose and hemicellulose. Chemical structure is different for torrefied char under pyrolysis gas and N2 atmosphere. And each composition in pyrolysis gas plays synergy role to the severity of torrefied char. The combustion kinetic of torrefied char were calculated using the Friedman method and the Ozawa-Flynn-Wall method.

Effect of surfactant on hydrothermal carbonization of coconut shell.

The effect of surfactant on the hydrothermal carbonization performance and pseudo-lignin formation were investigated. Especially, the fuel properties and combustion characteristics of hydrochar and solid product were determined. Furthermore, the mechanism of surfactant acted in hydrothermal carbonization was also identified in this article. The results showed that surfactant improved the content of solid products, lignin, heavy bio-oil (HBO), H2 and CO. Moreover, sodium dodecylbenzenesulfonate promoted the increase of the surface area of hydrochar from 4.93 to 41.43 m2/g. The mechanism showed surfactant formed water/oil film around the hydrochar to prevent HBO from leaving the pore or surface of hydrochar and promoted the condensation and polymerization of 5-hydroxymethylfurfura (5-HMF) with hydroxymethylfurfura (HMF) to form pseudo-lignin. The HBO and pseudo-lignin were beneficial for improving integrated combustion characteristic index (SN) during combustion. The article provides a new method to promote hydrothermal carbonization (HTC) for obtaining high value hydrochar as fuels.

The influence of combined pretreatment with surfactant/ultrasonic and hydrothermal carbonization on fuel properties, pyrolysis and combustion behavior of corn stalk.

The surfactant/ultrasonic combined with hydrothermal carbonization (HTC) were performed to investigate the effect on fuel properties, pyrolysis and combustion behavior of hydrochar under different condition. The results showed that the C/H and O/C ratio of corn stalk (CS) + H2SO4 + tween was 1.1 and 0.29, which were close to coal, and the heat value reached 28.89 MJ/kg. HTC combined with ultrasonic/surfactant realized the complete separation of lignin with cellulose and hemicellulose in CS. Ultrasonic restricted the hydrolysis of lignin under alkaline condition and pseudo-lignin formation under acidic condition. Tween inhibited the formation and deposition of "pseudo-lignin". The thermogravimetric (TG) experiments displayed the tween combined with HTC improved the pyrolysis temperature and decreased activation energy as well as the combustion ignition temperature which showed better pyrolysis and combustion characteristics. The nth-order kinetic mode was fit with the TG datas. The mechanism of tween combined with HTC was also analyzed.

Pyrolysis of Torrefied Biomass.

Pyrolysis, one of the most promising thermal conversion technologies for biomass conversion, can decompose biomass into solid bio-char, liquid bio-oil, and combustible gas to meet different energy needs. However, pyrolysis efficiency and product quality are not as good as expected when raw biomass is used owing to the properties of raw biomass (e.g., high moisture, oxygen, and alkali metal contents). Torrefaction is an emerging biomass pretreatment technology that can improve the physical and chemical properties of raw biomass, and pyrolysis efficiency and final product quality can therefore be improved by using torrefied biomass. We review several advantages of pyrolysis of torrefied biomass in terms of the conversion process and final product quality.

The pelletization and combustion properties of torrefied Camellia shell via dry and hydrothermal torrefaction: A comparative evaluation.

The torrefaction performance and properties of torrefied CS (Camellia shell) bio-char obtained via dry and hydrothermal torrefaction have been compared as well as pyrolysis and combustion properties. And making of torrefied pellets and their properties such as pellet density, Meyer hardness, and energy consumption are also investigated. The results showed that dry torrefied bio-char had higher energy and density at 220 °C and decreased significantly with temperature, while hydrothermally prepared bio-char had stable energy and mass yield with temperature. The coalification status of hydrothermally bio-char is similar to that of sub-bituminous coal. The pellet formed from dry terrified bio-char via quart tube in 220 °C with high pellet density (1048 kg/m3) and low energy consumption (17.6 KJ/kg) in spite of low the Meyer hardness (6.8 N/mm2). As for the process kinetics, the activation energy via dry torrefection with auger showed lower activation energy 43.26 KJ/mol as well as lowest ignition temperature (290 °C), compared to hydrothermal torrefaction.

Influence of biomass pretreatment on upgrading of bio-oil: Comparison of dry and hydrothermal torrefaction.

The dry and hydrothermal torrefacation of on Camellia Shell (CS) was carried on three different devices- batch autoclave, quartz tube, and auger reactor. The torrefied bio-char products were investigated via TGA, elemental analysis and industrial analysis. Moreover, the pyrolysis and catalytic pyrolysis properties of torrefied bio-char were investigated. The results showed torrefaction significantly influenced the content of hemicellulose in CS. And hydrothermal torrefaction via batch autoclave and dry torrefaction via auger reactors promoted the hemicellulose to strip from the CS. Quartz tube and auger reactor were beneficial for devolatilization and improving heat value of torrefied bio-char. The result showed that the main products were phenols and acids. And hydrothermal torrefaction pretreatment effectively reduced the acids content from 34.5% to 13.2% and enriched the content of phenols (from 27.23% to 60.05%) in bio-oil due to the decreasing of hemicellulos in torrefied bio-char. And the catalyst had slight influence on the bio-oil distribution.

Influence of pre-treatment on torrefaction of Phyllostachys edulis.

This study investigated the effects of different pre-treatments on structural changes in Phyllostachys edulis. Samples were pretreated with water, 15% ammonia water, 2% sulfuric acid, hydrothermal carbonization, and ball milling. Moreover, ultrasound was introduced. The influence of pre-treatment on the physiochemical property and composition of P. edulis were studied. Moreover, torrefaction characterization was performed and the distribution of torrefaction products of pretreated samples was determined. Results showed that pre-treatment effectively modified physiochemical structure and the torrefaction property of P. edulis. The pretreatment reduced the ash content and increased the bio-oil content of the torrefaction products. Compared with that of the raw material, the residual bio-char content of the pretreated samples decreased by 2-8%, and degradation temperature of bio-char fluctuated between 365°C and 321°C. The distribution of bio-oil contents, bio-char, and bio-gas in the torrefaction products significantly varied with pretreatments methods.

Treatment of urban sludge by hydrothermal carbonization.

Urban sludge was treated by Hydrothermal carbonization (HTC). The effect of hydrothermal carbonization temperature, mixing with or without catalysts on solid products yield, heavy metal contents, turbidity and COD value was evaluated. The result showed solid products yield decreased from 92.04% to 52.65% when the temperature increased from 180 to 300°C. And the Cu, Zn, and Pb contents under exchangeable states decreased and reached discharge standard. Addition of FeCl3 or Al(OH)3 resulted in a significant increase in the exchangeable states of Zn, Pb, Cr, and Cd and decrease in their residual states. The turbidity and COD value of hydrothermal liquid decreased from 450° to 175°, and 13 to 6.8g/L, with increasing hydrothermal temperature. Comparison with HTC, solid productivity from low-temperature pyrolysis is higher. The exchangeable states of Cu, Zn, and Cr exceeded the limiting values. Our results show HTC can facilitate transforming urban sludge into no-pollution and energy-rich products.