Search

• The effects of AAEMs on the APR of bio-based surrogates over Ni/α-MoO 3 were studied. • AAEMs increased hydrogen yield and promoted TOC removal. • AAEMs prevented Ni leaching and promoted oxygen vacancy formation. • The carbon deposition on the catalyst with Mg was the lowest. Aqueous phase reforming (APR) of biomass derived products is a promising hydrogen generation approach, and many internal alkali and alkaline earth metals (AAEMs) have been proven capable of catalyzing these processes. In this study, APR of various functional groups in biomass derived products over Ni/α-MoO 3 catalyst toward hydrogen production and pollutants control was investigated. The effect of different AAEMs was comprehensively studied under a temperature of 225 °C and a residence time of 30 min. Findings demonstrated that Na, K, Ca, and Mg all showed hydrogen generation and total organic carbon removal capability, whose performances were competitive to Ni/α-MoO 3 catalyst. Moreover, although the presence of single K suppressed the removal of total nitrogen (TN), the combination of K and the Ni/α-MoO 3 catalyst exhibited the optimal removal efficiency of TN (69.92 %). A series of characterization results revealed that the AAEMs effectively prevented Ni leaching in the hydrothermal environment of the Ni/α-MoO 3 catalysts and promoted the formation of oxygen vacancies, inhibiting carbon deposition and deactivation of the catalyst. [ABSTRACT FROM AUTHOR]

• Large particle size biomass is conducted for oxygen-stream gasification. • The spatial distribution of AAEMs are detected and analyzed. • X-ray CT technology is employed to interpret AAEMs catalytic gasification. • The mechanism of AAEMs catalytic gasification for large particle biomass is studied. To evaluate the effect of alkali and alkaline earth metals (AAEMs) species on the catalytic gasification of large particle-size biomass, a vertical fixed-bed reactor is conducted for candlenut wood gasification under the oxygen-stream atmosphere. The biochar samples derived from gasification are characterized by SEM, X-ray CT, BET, and FTIR. Tar and syngas are analyzed via GC–MS and GC respectively. Advanced X-ray CT technology provides beneficial visualization to assist in the interpretation of the catalytic gasification of large particle-size biomass loaded with AAEMs. The results indicate that a progressive augmentation of AAEMs content along the radial direction and end surface for all loaded samples and biochar samples, which could also be visualized from the 3D reconstruction of X-ray CT. Many large pores (40–60 μm) aligned along the grain direction collapse after the gasification and generate numerous micropores in biochar samples. 10–20 μm pores are more prominent in biochar as the biomass samples are loaded with KCl and CaCl 2. The biochar from gasification of biomass loaded with CaCl 2 has more well-developed pores, a larger specific surface area, and –OH compounds, aldehydes, ketones and carboxylic acids. The addition of AAEMs facilitates the high generation of M1 compounds (contains 1 benzene ring) in the tar and suppresses the enhancement of M4 compounds, long-chain alkanes, and other compounds. The lowest carbon conversion (57.12 %) is acquired from acid-washed sample. H 2 concentration augments but CO concentration declines by loading AAEMs. The highest H 2 concentration of 62.1 % is detected by the addition of CaCl 2. When loaded with KCl, the syngas calorific value reduces by 1.37 %, whereas loaded with NaCl, CaCl 2 , and MgCl 2 show an augmentation of 11.48 %, 10.56 %, and 2.55 %, respectively. A decrement of C n H x concentration in the syngas derived from gasification of biomass samples loaded with KCl and MgCl 2 and an increment one loaded with NaCl and CaCl 2 are acquired. [ABSTRACT FROM AUTHOR]

• Three types of solution with different severities were used to wash rice straw. • One sharp peak was in DTG curves for Raw-RS, but two peaks for HCl-RS and APBO-RS. • Evolution of evolved gases (H 2 O, CH 4 , CO, CO 2 , and C O stretching) was analyzed. • APBO pretreatment showed the highest activation energy for rice straw pyrolysis. • The relative content of levoglucosan was increased because of the removing of AAEMs. Washing pretreatment is a promising method for upgrading biomass by removing alkali metal and alkaline earth metals (AAEMs). In this study, three types of solution with different pretreatment severities (i.e., water (H 2 O), dilute hydrochloric acid (HCl) solution, and aqueous phase bio-oil (APBO)) were used to study the effects of the washing pretreatment on the pyrolysis behaviors and kinetics of rice straw. The pyrolysis experiments of raw and pretreated rice straw (Raw-RS, H 2 O-RS, HCl-RS, and APBO-RS) were carried out using TG-FTIR and Py-GC/MS. Results show that among the three types of washing pretreatment methods, the APBO washing pretreatment has the highest removal efficiency of AAEMs: 99.7% of K, 91.7% of Na, 96.6% of Mg, and 95.2% of Ca. According to TG-FTIR results, only one sharp mass loss peak was present in the DTG curves of Raw-RS and H 2 O-RS, whereas two mass loss peaks (one sharp peak and one shoulder peak) were observed in HCl-RS and APBO-RS. The evolution pattern of the volatile compounds (H 2 O, CH 4 , CO, CO 2 , and C O stretching) was thoroughly investigated, and the absorbance intensity of these components increased with the washing pretreatment of APBO and HCl. The APBO washing pretreatment had the highest activation energy in the conversion rate of 0.2–0.75, followed by HCl and H 2 O washing pretreatment. According to the Py-GC/MS results, the washing pretreatment reduced the relative contents of acids, ketones, furans, and phenols in bio-oil, whereas removing of AAEMs increased the relative contents of anhydrosugars (mainly levoglucosan). Among the three types of washing pretreatments, the APBO washing pretreatment had the most remarkable influence on the property of bio-oil, and this indicates that the APBO washing pretreatment is a promising method for upgrading biomass and its pyrolytic product. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 -enhanced water leaching can remove alkali/alkaline earth metals in biochar. • CO 2 -enhanced water leaching is facile without clearly destroying biochar structure. • Pore structure of biochar plays a dominant role in enriching phenols in bio-oil. • Alkali/alkaline earth metals enhance the O -compounds decarbonylation in bio-oil. Catalytic conversion of volatiles from biomass pyrolysis over biochar and its mechanism are important to the efficient utilization. The properties of biochar including alkali/alkaline earth metallic species (AAEMs) and pore structure exert the influence on bio-oil quality. In this work, a facile demineralization method by CO 2 -enhanced water leaching (CEWL) of biochar from bagasse pyrolysis was first applied to catalytic upgrading of pyrolysis bio-oil. The effect of AAEMs content and pore structures in biochar catalysts on upgrading performances was investigated. The results show that the CEWL of biochar can effectively remove most inherent AAEMs without obviously destroying pore structures. Pore structure of catalysts plays a dominant role in increasing phenols contents to 47.7% over CO 2 -activated biochar from 25.8% without biochar. The reaction mechanism was proposed that AAEMs enhanced the polymerization of aromatic hydrocarbons and the decarbonylation of the oxygenated compounds. High temperature is profitable to the generation of phenols and polycyclic aromatic hydrocarbons owing to easier decarbonylation of ketones and demethylation or demethoxylation of phenols. [ABSTRACT FROM AUTHOR]

• Effect of acid-washing pretreatment on the volatile-char interactions was studied. • AAEMs catalyzed both primary pyrolysis and secondary volatile-char interactions. • AAEMs removal and weakened interactions promoted sugar-enriched bio-oil production. • AAEMs removal and weakened interactions reduced char yield with more pores formed. • 63.37% bio-oil was obtained for packed bed by weakened interactions & AAEMs removal. The purpose of this study is to investigate the effect of acid-washing pretreatment on the poplar wood (PW) pyrolysis under different volatile-char interactions, the experiment was conducted in a self-designed fixed-bed pyrolysis reactor. It was found that acid-washing pretreatment could alter the surface morphology of PW, increase the cellulose crystallinity and reduce the inorganic ash components (mainly Alkali and Alkaline Earth Metal species, AAEMs). AAEMs acted as catalysts for sugar ring fragmentation and charring reactions during both primary pyrolysis of biomass and secondary volatile-char interactions. The removal of AAEMs would increase the bio-oil yield and decrease the biochar and non-condensable gas yields, same trend was also observed with the decreasing volatile-char interactions. The removal of AAEMs and weakened volatile-char interactions both resulted in an increase of C content and a decrease of O content of biochar with more pore structures generated, especially micropores, the content of anhydrosugars in bio-oil was also largely enhanced. In addition, the decrease of volatile-char interactions would significantly reduce the effect of AAEMs in biomass on the pyrolysis process. A highest bio-oil yield of 63.37 wt% with 34.38% of anhydrosugars could be obtained even for a packed fixed-bed reactor by intentionally reducing volatile-char interactions and removing AAEMs from biomass during the process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-firing the biomass with high-Ca coal reduces the ash slagging rates by 17–65%. • Co-firing corn stalk with the high-Si/Al coal exacerbates the ash slagging tendency. • Torrefaction aggravates the growth of slagging during combustion except for that of sawdust. • Additional measures are suggested to alleviate the ash slagging of torrefied herbaceous biomass. Torrefaction is a competitive technology for biomass upgrading. Knowing that the effects of torrefaction on ash-related issues during biomass combustion and co-combustion with coal have been less investigated, Parts Ⅰ and Ⅱ of this work investigated the particulate matter emission and ash fouling behavior. To be a continuation, in the present paper, the effect of biomass torrefaction on ash slagging deposition which occurs in the high-temperature areas of the furnace was focused on. Two herbaceous biomass, one woody biomass, and their torrefied chars were fired and co-fired with two coals respectively on a drop-tube furnace at 1300℃. The slags were collected from mullite tubes placed in the furnace for quantification and characterization. Computer-controlled scanning electron microscope (CCSEM) was employed to obtain the distribution of particle size and inorganic species in the bulk ash. The results indicate that co-firing the biomass with high-Ca coal significantly reduces the ash slagging rates due to the substitution of alkalis by Ca from the silicates/aluminosilicates which inhibits the agglomeration and sintering of the ash particles, and finally reduces the inertial impaction and capture of the particles on the tube. Co-firing corn stalk with the high-Si/Al coal promotes the formation of alkaline aluminosilicates which are sticky at a high temperature. Therefore, the slagging tendency is exacerbated. Torrefaction reduces the ash slagging rate of sawdust resulting from the effective removal of S and Cl and the transformation of AAEMs (alkaline and alkaline earth metals) into less-reactive forms during torrefaction which reduces the vaporization and transformation of AAEMs into coarse particles as aluminosilicates by surface reactions. However, the ash slagging rates are increased by torrefaction for other fuels due to more retention of AAEMs after torrefaction resulting in more mixed silicates or aluminosilicates in bulk ash contributing to the growth of slagging deposits during combustion. Measures are suggested to be taken, such as optimizing the operation conditions, co-firing with high-Ca coals, using additives, etc. to alleviate the ash slagging during torrefied herbaceous biomass combustion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Barium modified hydroxyapatite is highly effective for glucose isomerization to fructose in ethanol. • Fructose yield of 35.4% with selectivity up to 93.5% was obtained at glucose loading of 10 wt%. • The catalyst was reused with high recovery rate and ultralow leaching of ions. • The composition, structure and activity of catalyst can be completely restored via calcination. The application of synthetic catalysts to displace costly isomerases for glucose isomerization to fructose has been a long-standing goal in biomass valorization, but current catalysts generally suffer from inferior stability and reusability. Here we show that the combination of barium modified hydroxyapatite (Ba/HAP) as catalyst with ethanol as solvent enables highly efficient and selective isomerization of glucose to fructose, affording fructose yield of 35.4% with selectivity up to 93.5% at high glucose loading (10 wt%). Moreover, the Ba/HAP catalyst was reused with high recovery rate and the leaching of ions was greatly inhibited. The composition, structure and catalytic activity of catalyst can be almost completely restored after calcination. Density functional theory simulations revealed that the formation of relatively stable BaCa 6 (PO 4) 4 O phase is beneficial to the improved catalyst stability. Simultaneously achieving high reaction efficiency and good catalyst reusability in green solvent, our study is an important step towards sustainable catalysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • S and Cl in biomass are significantly removed after torrefaction. • AAEMs in biomass tend to transform to less-reactive forms after torrefaction. • Torrefaction inhibits the mineral vaporization in combustion, thus reduces the emission of PM 1. • PM 1-10 increases due to more retention of the metals or decreases by agglomerating into PM 10+. Torrefaction is a promising technology to scale up the utilization of biomass for power purposes. The ash-related issues during biomass combustion and co-combustion are essential to be addressed, however, on which the effects of torrefaction are seldom concerned and need in-depth and comprehensive investigation. To provide useful information related, the authors conducted a series of studies. In the present work, the particulate matter (PM) emission during combustion is focused on. Three biomasses were torrefied at a fixed-bed reactor, and the elemental release and transformation during torrefaction were characterized through chemical fractionation analysis. The combustion tests of the raw and torrefied biomass and their blends with two typical coals were conducted on a drop-tube furnace at 1300℃ in air. The PM 10 (particulate matter with an aerodynamic particle size below 10 μm) collected by a Dekati low-pressure impactor and PM 10+ (particulate matter with an aerodynamic particle size above 10 μm) collected by a Dekati cyclone were characterized by a scanning electron microscope equipped with energy dispersive spectrometer (SEM-EDS). The results indicate that torrefaction effectively reduces S and Cl in biomass while slightly reducing the alkalis. The contents of refractory elements (Mg, Ca, and Fe) are hardly influenced. Torrefaction promotes the transformation of AAEMs (alkaline and alkaline earth metals) into less-reactive forms (HCl-soluble and insoluble). The vaporization of alkalis, S, and Cl during biomass combustion is reduced and the retention of AAEMs into aluminosilicates is promoted after torrefaction. This reduces the emission of PM 1 (particulate matter with an aerodynamic particle size below 1 μm) from biomass combustion. During co-combustion, the PM emission largely depends on the combined effects of elemental vaporization, competing reactions (alkalis against Mg, Ca, and Fe), retention of metals into aluminosilicates, and sulfation of chlorides. The inhibited effect of torrefaction on mineral vaporization reduces the formation of PM 1 by condensation. The emission of PM 1-10 (particulate matter with an aerodynamic particle size between 1 and 10 μm) either increases due to the promoted retention of the metals in coarse particles or decreases by agglomerating into PM 10+. Torrefaction shows a preferable performance concerning its effects on PM emission during biomass combustion and co-combustion with coal. [ABSTRACT FROM AUTHOR]

[Display omitted] • S and Cl in biomass are significantly removed after torrefaction. • AAEMs in biomass tend to transform to less-reactive forms after torrefaction. • Torrefaction inhibits the mineral vaporization in combustion, thus reduces the emission of PM 1. • PM 1-10 increases due to more retention of the metals or decreases by agglomerating into PM 10+. Torrefaction is a promising technology to scale up the utilization of biomass for power purposes. The ash-related issues during biomass combustion and co-combustion are essential to be addressed, however, on which the effects of torrefaction are seldom concerned and need in-depth and comprehensive investigation. To provide useful information related, the authors conducted a series of studies. In the present work, the particulate matter (PM) emission during combustion is focused on. Three biomasses were torrefied at a fixed-bed reactor, and the elemental release and transformation during torrefaction were characterized through chemical fractionation analysis. The combustion tests of the raw and torrefied biomass and their blends with two typical coals were conducted on a drop-tube furnace at 1300℃ in air. The PM 10 (particulate matter with an aerodynamic particle size below 10 μm) collected by a Dekati low-pressure impactor and PM 10+ (particulate matter with an aerodynamic particle size above 10 μm) collected by a Dekati cyclone were characterized by a scanning electron microscope equipped with energy dispersive spectrometer (SEM-EDS). The results indicate that torrefaction effectively reduces S and Cl in biomass while slightly reducing the alkalis. The contents of refractory elements (Mg, Ca, and Fe) are hardly influenced. Torrefaction promotes the transformation of AAEMs (alkaline and alkaline earth metals) into less-reactive forms (HCl-soluble and insoluble). The vaporization of alkalis, S, and Cl during biomass combustion is reduced and the retention of AAEMs into aluminosilicates is promoted after torrefaction. This reduces the emission of PM 1 (particulate matter with an aerodynamic particle size below 1 μm) from biomass combustion. During co-combustion, the PM emission largely depends on the combined effects of elemental vaporization, competing reactions (alkalis against Mg, Ca, and Fe), retention of metals into aluminosilicates, and sulfation of chlorides. The inhibited effect of torrefaction on mineral vaporization reduces the formation of PM 1 by condensation. The emission of PM 1-10 (particulate matter with an aerodynamic particle size between 1 and 10 μm) either increases due to the promoted retention of the metals in coarse particles or decreases by agglomerating into PM 10+. Torrefaction shows a preferable performance concerning its effects on PM emission during biomass combustion and co-combustion with coal. [ABSTRACT FROM AUTHOR]

[Display omitted] • HTC-derived algal hydrochar was recovered via filtration with and without a solvent. • The two recovery methods greatly affect the yields and properties of hydrochar. • Under identical conditions, filtration without a solvent gives higher hydrochar yield. • The higher hydrochar yield is attributed to the biocrude retained on its surface. This contribution reports the effects of product recovery methods on the yields and properties of hydrochars produced from hydrothermal carbonization (HTC) of algal biomass. A slurry of Chlorella vulgaris with 10 wt% of solid loading was hydrothermally carbonized at 180 – 220 °C with holding time of 15 and 60 min. The resulting hydrochars were recovered by two prevailing methods, namely direct filtration and dichloromethane (DCM)-aided filtration. The results indicate that, under identical HTC conditions, compared with DCM-aided filtration, direct filtration always results in higher hydrochar yield because of the biocrude retained on its surface. The presence of residue biocrude in the hydrochars from direct filtration further leads to considerable differences in their properties, as compared with their counterparts from DCM-aided filtration. Specifically, under identical HTC temperature and holding time, DCM-aided filtration yields hydrochars of lower volatile matter contents but higher fixed carbon and ash contents, as compared with the hydrochars from direct filtration. Direct filtration generally recovers hydrochars of greater higher heating values and energy-based yields as compared to DCM-aided filtration. The product recovery methods show considerable impacts on the concentrations of Na, K, Mg, and Ca and their retentions in the hydrochars at 220 °C for 60 min, with higher concentrations and retentions of these elements being observed in the hydrochars from DCM-aided filtration. The hydrochars at 220 °C for 15 and 60 min from DCM-aided filtration show higher specific reactivity of 0.040 – 0.058 min−1 and 0.066 – 0.096 min−1 at hydrochar conversions of ≤ 82 % and ≤ 78 %, respectively, as compared with their direct-filtration counterparts, due to their higher concentrations of catalytic alkali and alkaline earth metals. These findings highlight the importance of considering product recovery methods when comparing the yields and properties of hydrochars from HTC of algae reported in the literature. [ABSTRACT FROM AUTHOR]

• Biochar samples produced from biomass and lignocellulosic components were studied. • The gasification activation energy of biochar ranged from 109.8 to 196.1 kJ/mol. • Lignin was the most active biomass component determining the biochar reactivity. • Modelled Biochar with 16% cellulose, 24% xylan and 52.5% lignin had the best performance. Biochar can become a renewable substitute to coal in the future's energy mix. This work aims to investigate the optimization of reactivity of biochar samples derived from biomass (Miscanthus) and its lignocellulosic components (i.e. cellulose, hemicellulose and lignin) by studying the material characteristics, composition, thermal behavior and interaction during the CO 2 gasification process. For biochar production, the yield increased with lignin content in the biomass, but high lignin content reduced biochar's porous structure. The conversion characteristic was gradually stimulated by increasing the gasification temperature and heating rate, and the lignin biochar (LB) reactivity was the most promoted. High lignin content was favorable for improving the biochar reactivity. The reactivity of the xylan biochar (XB) was attributed to the high content of alkali and alkaline earth metals, while the activity of the cellulose biochar (CB) was due to the rich porous structure. The activation energy of biochar samples gasification reaction ranged from 109.8 to 196.1 kJ/mol, and the values decreased with the increase of carbon conversion rate. Modelled biomass with 32.5% cellulose, 15% xylan and 52.5% lignin was considered the optimal feedstock to make biochar because of the its low activation energy and high gasification reactivity. [ABSTRACT FROM AUTHOR]

• Two different aquatic biomass were pretreated by water and acid washing. • Comparison was conducted by systematic experiments and equilibrium calculations. • Impact of mineral migration and transformation on inhibiting slagging was investigated. • Leaching investigation showed water washing had better effect on Na, K, and Cl. • It was recommended to use water washing for pretreatment of aquatic biomass. In this study, aquatic biomasses of Ulva lactuca and Hydrilla verticillata were pretreated by water and acid washing. A comprehensive assessment strategy, including systematic experiments and equilibrium calculations, was used to study the migration of elements and transformation characteristics of minerals in aquatic biomass ash before and after leaching pre-treatment. The effect of leaching pre-treatment on slagging inhibition was analyzed. Owing to the different mineral compositions and characteristics of the two types of aquatic biomass, the serious slagging caused by Ulva lactuca was related to the presence of alkali (Na and K) sulfate. In contrast, the presence of silicate/aluminosilicates in Hydrilla verticillata had a greater effect on slagging. The removal of alkali metals (especially Na and K) and Cl from aquatic biomass by leaching pretreatment was conducive to alleviating aquatic biomass slagging. Following leaching pretreatment, the alkali index of the aquatic biomass was reduced to <0.17, and the Cl content was reduced to <0.3%. Furthermore, the abundant alkaline earth metals (Ca and Mg) in aquatic biomass can inhibit slagging by generating high-melting-point alkaline earth metal silicates or phosphates. The removal rate of alkaline earth metal oxides by acid washing was >96% and >78% in Ulva lactuca and Hydrilla verticillata , respectively, while water washing was less effective. Although water and acid washing can alleviate slagging, a comparative investigation showed that water washing of aquatic biomass had better outcomes than acid washing. Therefore, water washing is a better way to comprehensively pre-treat aquatic biomass. The results obtained can help promote the thermochemical utilization of aquatic biomass on an industrial scale. [ABSTRACT FROM AUTHOR]

• Recent progress in Biomass-derived nanoelectrocatalysts was investigated. • Various methods for energy generation from biomass by nano-routes were developed. • The energy generation from biomass is one of strategy to move towards to bioeconomy. • The future outlook and challenges were discussed. The changing global approach for protecting the planet and turning to a low-carbon economy has made the growing demand for biomasses at the core of biochemistry. Biomass contains all the substances in nature that in the recent past were living things, made from living organisms or their wastes. Biomass is carbon-based and is a mixture of organic molecules, including hydrogen, usually oxygen, and often nitrogen, and small amounts of other atoms such as alkali metals, alkaline earth metals, and heavy metals. Production and consumption of biomasses grew in sustainable procedures do not cause a net change in the CO 2 content of the atmosphere. So, the biomasses can be regarded as carbon neutral due to the mentioned net carbon cycle they involve. Energy production from biomass sources is utilized to generate electricity and heat. These sources are renewable sources and CO 2 production of these sources is natural and does not produce greenhouse gases. The development of practical techniques for sustainable energy generation from biomass is one of novel strategy to overcome air pollution and move towards the sustainable bioeconomy. This study reviews recent progress in Biomass-derived nanoelectrocatalysts for the sustainable energy development that includes biomass-based electrocatalyst synthesis, biomass-based nanoelectrocatalysts for water splitting, and biomass-based nanoelectrocatalysts for fuel cells. Finally provides future perspectives to motivate future research such as the necessity to increase agricultural and so food production while reducing inputs to balance biomass valorization for energy production versus biomass upgrading, and to develop practical techniques for cheap pretreatment and metabolic engineering of lignocellulosic and efficient strategies for the commercial-scale production of lignocellulosic based-biofuels. [ABSTRACT FROM AUTHOR]

• Cel -FC covers catalysis by AAEMs in parallel with spontaneous reaction channels. • Data comparisons cover a broad operating domain, including K and Ca loadings to 0.0415 mol cation/mol glucose. • AAEMs catalyze depolymerization plus monomer decomposition and charring. • The catalytic processes impart a stunning breadth of devolatilization behavior. • AAEM catalysis lowers the activation energies for all primary reaction processes. This paper extends cel -FC, the reaction mechanism for the devolatilization of mineral-free cellulose formulated in Part 4 of this series, to cover catalysis by alkali and alkaline earth metals (AAEMs) in parallel with the spontaneous reaction channels. Quantitative comparisons with data cover temperatures to 600 °C, heating rates from 100 to 5000 °C/s, contact times after heatup to 30 s, pressures of vacuum and 0.1 MPa, and K and Ca loadings to 0.0415 mol cation/mol glucose. Collectively the catalytic processes are responsible for an enormous breadth of devolatilization behavior over the range of typical AAEM loadings in whole biomass. AAEMs catalyze depolymerization via scission and unzipping as well as monomer decomposition and charring but with much different sensitivities. AAEM catalysis lowers the activation energies for all four reaction processes. For scission and unzipping, the shift moves the onset of devolatilization toward cooler temperatures. Monomer decomposition has the strongest shift to explain both suppressed oil production, due to the accelerated conversion of labile bridges into refractory char links, and enhanced gas production, as noncondensables are the explicit products of this process. Oil molecular weight distributions (MWDs) become heavier for progressively heavier AAEM loadings due primarily to suppression of isolated modified levoglucosan units. Consequently, the lighter halves of the oil MWDs for vacuum and atmospheric pressure are very similar for the heaviest AAEM loadings, contrary to the preponderance of monomers and dimers in oils from mineral-free cellulose at atmospheric pressure. Depolymerization accelerates compared to monomer decomposition in extrapolations to faster heating rates, which enhances oil yields. Consequently, the impacts of AAEM catalysis are much stronger at slower heating rates than at faster rates. [ABSTRACT FROM AUTHOR]

Abstract: Volatile–char interactions are an important phenomenon in almost all existing gasification processes. The volatile–char interactions can very significantly affect almost every aspect of low-rank fuel gasification, including the volatilisation of alkali and alkaline earth metallic species that are inherent catalysts for gasification, the evolution of char structure, the dispersion of inherent catalysts and thus the reactivity of char. The volatile–char interactions can also influence the formation of pollutant-forming species such as NH3. This paper provides an overview of our recent work in this area. The essence of volatile–char interactions appears to be the interactions between radicals, especially H radicals, and the char during pyrolysis and gasification. The volatile–char interactions must be an important consideration in the development of new gasification technologies for low-rank fuels such as brown coal and biomass to minimise the adverse effects and maximise the positive effects of volatile–char interactions during the gasification of low-rank fuels. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to investigate the effects of inorganic species in biomass, especially the alkali and alkaline earth metallic (AAEM) species (K, Na, Mg and Ca), on the yield and properties of bio-oil from the pyrolysis of biomass. A mallee wood sample from Western Australia was washed with water and a dilute acid solution to remove its AAEM species. The water-washed and acid-washed mallee wood samples were then pyrolysed in a fluidised-bed reactor at 500°C under fast heating rate conditions. The removal of AAEM species did not result in significant changes in the yields of bio-oil and bio-char. However, the bio-oil properties, e.g. viscosity, were drastically affected by the removal of AAEM species. Our results indicate that the water-soluble AAEM species were not as important as the water-insoluble but acid-soluble AAEM species in influencing the bio-oil composition and properties. It is believed that the acid-soluble AAEM species (especially Ca) were more closely linked with the organic matter in biomass and thus were closely involved in the reactions during pyrolysis. The removal of AAEM species, especially the acid-soluble AAEM species, led to very significant increases in the yields of sugars and lignin-derived oligomers, accompanied by decreases in the yields of water and light organic compounds in the bio-oil. [Copyright &y& Elsevier]

[Display omitted] • Ca in biomass can significantly improve the CLG performance. • The excessive Ca will cause obvious agglomeration and sintering. • Ca reduces the activation energy of CLG under the reasonable concentration. • The improvement of (CH 3 COO) 2 Ca is better than that of CaCl 2. • Gasification efficiency increases by 45.61% after adding 6% (CH 3 COO) 2 Ca. As the most abundant trace element in agricultural wastes, Ca can improve the reaction performance, but aggravate the agglomeration and sintering of reaction materials at high temperature during the process of thermochemical conversion. In this paper, the effect of Ca in rice husk was studied in chemical looping gasification (CLG) under different conditions of Ca concentration, Ca solution, temperature and steam/carbon (S/C). The results indicated that Ca would significantly improve the CLG performance, but cause obvious agglomeration and sintering phenomenon at high Ca concentration. Furthermore, the improvement for CLG performance of (CH 3 COO) 2 Ca was greater than that of CaCl 2. After adding 6% (CH 3 COO) 2 Ca, gas yield, carbon conversion efficiency and gasification efficiency increased by 53.30%, 47.06% and 45.61%, respectively. By contrast, they respectively increased by 28.11%, 17.27% and 26.79% after adding CaCl 2. Thermogravimetric analysis showed that the presence of Ca was beneficial to reduce the activation energy of the reaction. In the pyrolysis stage, the maximum reduction of activation energy was 37.43%, while in the gasification stage, the maximum reduction of activation energy was 65.36% after adding Ca in the rice husk. Compared with CaCl 2 , (CH 3 COO) 2 Ca decreased more activation energy of CLG process. Moreover, with the increase of temperature and S/C, the CLG performance increased firstly and then decreased after adding 6% (CH 3 COO) 2 Ca by impregnation on the pickling rice husk. 800℃ and 6.9 was the optimal temperature and S/C to achieve the best gasification efficiency of 65.03% and gas yield of 0.69 Nm3/kg in the CLG process. [ABSTRACT FROM AUTHOR]

• Rich H 2 gas from co-gasification of torrefied biomass and low rank coal. • The enhancing role of dry/wet torrefaction on the H 2 yield was compared during the co-gasification. • Synergetic effect in terms of higher gas yield was manifested. • The catalytic role of AAEMs is the key for synergetic effect. • The co-pyrolysis reactivity and kinetic analysis was investigated via thermogravimetry reactor. In this study, the enhanced rich H 2 gas was produced via the co-gasification of torrefied biomass and low-rank coal in the fixed bed reactor. The properties of wet/dry torrefied char was compared, and then the synergetic effect between dry/wet torrefied char and the low rank coal during the gasification were analyzed to study the enhancing effect of torrefaction on the H 2 yield. Moreover, the co-pyrolysis reactivity and kinetic analysis were investigated to further determine the synergetic mechanism. The results showed that the change of fundamental compositions in biomass after torrefaction, especially, the removal of cellulose played an important role in the enhancement of H 2. Thus, dry torrefaction was more beneficial for improving H 2 yield than the wet one. Besides, an obviously synergetic effect was observed from coal and dry torrefied biomass in their ratio 1:1 and 3:1, which was mainly due to the catalytic role of alkali and alkaline earth metallic species, and the transfer of active OH and H radicals from the torrefied biomass to the coal. The co-pyrolysis reactivity and kinetic analysis further proved the synergetic effect on reducing activation energy. [ABSTRACT FROM AUTHOR]

• Removal rate of AAEMs are remarkably improved by using aqueous phase bio-oil. • Furfural, hydroxyacetone, ethylene glycol, phenol and guaiacol are used for leaching. • Acetic acid is the key component in bio-oil to leach AAEMs from biomass. • Synergistic leaching effect occurred between acetic acid and non-acidic components. • Non-acidic compounds in bio-oil play an important role in leaching of AAEMs. In this study, six dominant organic compounds in biomass pyrolyzed bio-oil, composed of acidic compound (acetic acid) and non-acidic compound (furfural, hydroxyacetone, ethylene glycol, phenol, and guaiacol) were used to remove AAEMs from different lignocellulosic biomass (rice husk, cotton stalk, and fir sawdust) by leaching pretreatment. Other four conventional solutions (deionized water, hydrochloric acid solution, aqueous phase bio-oil, and simulated bio-oil) were selected as control eluents. Results showed that the removal rate of AAEMs was highly affected by the types of immersion solutions, pH values, and the species of biomass. Majority of K in biomass could be removed by leaching of acetic acid. Ca was more difficult to be removed by leaching of water and acetic acid, but could be removed by leaching of HCl. In general, the removal rate of K was highest among the four species of AAMEs by using five non-acidic components, followed by Na, Mg, and Ca. The use of five non-acidic solutions was significantly benefit for the remove of K, Mg, and Na, but, was less useful in removal of Ca in rice husk and fir sawdust. However, the removal rates of Ca in cotton stalk by leaching of phenol, guaiacol, and hydroxyacetone were increased to nearly three times than water leaching. A synergistic effect for removing AAEMs occurred between acetic acid and non-acidic components in bio-oil, indicating that the non-acidic compounds also play an important role in leaching of AAEMs. [ABSTRACT FROM AUTHOR]

• Significant reduction of Alkali and Alkaline Earth Metal (AAEM) in the biomass with acid-leaching treatment. • The Higher Heating Value (HHV) is not significantly influenced by the acid-leaching treatment. • The removal of AAEM significantly affected the degradation of hemicellulose, cellulose, and lignin. • The second order (F2) mechanism can illustrate the catalytic pyrolysis process of lignocellulose biomass. • Acid-leaching process prior to catalytic pyrolysis promotes high devolatilization and reaction rate. Improvements on the pyrolysis process of biomass fuels are needed to obtain a high-quality of bio-oil. Pre-treatment by acid leaching prior to the pyrolysis process is considered to remove Alkali and Alkaline Earth Metal (AAEM) from the biomass, since AAEM adversely affect the catalytic pyrolysis process. Therefore, the main objective of the present work was to determine and compare the effect of mixed-catalysts consisting of H-ZSM-5 and Al-MCM-41, which are used at different ratios in lignocellulose biomass pyrolysis via Thermal Gravimetric Analysis (TGA) for both, un-leached and leached biomass. In addition, the activation energies have been determined based on the solid-state reaction mechanism. The results from the acid leaching treatment showed that the optimum leaching process was set to 30 min, 30 °C and 5 wt% acetic acid in the leaching liquid. This resulted in 59%, 95%, 99%, and 96% reduction degree of Calcium (Ca), Magnesium (Mg), Potassium or Kalium (K), and Natrium (Na), respectively. The Higher Heating Values (HHVs) for un-leached and leached biomass were 19.42 and 19.14 MJ/kg, respectively, calculated by using the Milne formula. The HHV value is not significantly influenced by the acid-leaching pre-treatment. Thermogravimetric analysis showed similar trends for the mass loss as a function of temperature and four stages could be determined from the thermal degradation of biomass. There was no significant shift in the temperature profiles between un-leached and leached biomass degradations. However, the removal of AAEM significantly affected the degradation of hemicellulose, cellulose, and lignin. A 12.4–18.2% increase of mass losses could be found in Phase 2 for leached biomass, compared to un-leached biomass. The mass losses in Phase 2 also increased with increased heating rates. From the un-leached biomass experiments using a catalyst mixture, the percentage of mass loss increased from 64.95 wt% at 10 K min−1 to 68.33 wt% at 50 K min−1. Moreover, for the leached biomass, it rose from 65.71 wt% at 10 K min−1 to 66.73 wt% at 30 K min−1, before decreasing to 62.44 wt% at 50 K min−1. A lower mass loss in Phase 4 for leached biomass compared to un-leached biomass showed the influence of an AAEM removal. The second order (F2) mechanism was able to illustrate the catalytic pyrolysis process, proven by the result that the coefficient of determination (R2) was higher than 0.99, which was high compared to other mechanisms. An acid leaching pre-treatment led to a reduction in the activation energies. The activation energies for the un-leached biomass were 26.94 and 25.56 kJ mol−1 at a heating rate of 10 K min−1 for a process without and with a catalyst mixture, respectively. The activation energies for leached biomass were 24.05 and 21.80 kJ mol−1. The results also showed that the use of the acid leaching process as a treatment prior to catalytic pyrolysis is positive, since it resulted in high devolatilization and reaction rate. [ABSTRACT FROM AUTHOR]