Abstract: Pyrolysis technology has a great application prospect in the future. The essential properties of cellulose, pyrolysis mechanism, research tools, catalyst type and other important factors affecting the products distribution are discussed in detail. Particularly, the addition of a variety of catalysts and the optimum design of reaction device can significantly accelerate the cellulose pyrolysis, improve the product distribution and increase the selectivity of some high-value chemicals, thus effectively enhancing the resource and energy utilization value of pyrolysis products. Last but not the least, the future research orientation of cellulose pyrolysis technology is put forward based on some key questions to be solved.
Abstract: In recent years, the conversion of biomass-derived platform compounds into a variety of high value fuel and chemical products has attracted increasing attention from researchers. 5-Hydroxymethylfurfural (HMF) and furfural (FFR) belong to a class of important biomass-derived platform chemicals. The molecular structure of HMF and FFR is consisted of aldehyde group, furan ring and other functional groups, which endow them with unique chemical properties. In this paper, the research advances on the catalytic hydrogenation of HMF and FFR using various hydrogen sources, such as hydrogen, alcohol, silanes and formic acid, have been reviewed in detail. In addition, the main influencing factors like catalyst type and reaction conditions on the hydrogenation process as well as the reaction mechanism are discussed in depth. Meanwhile, research foreground in the catalytic hydrogenation of HMF/FFR has been prospected.
Abstract: With the booming of biodiesel industry, it is urgent to high-valued to recycle glycerol as the main by-product. The condensation of glycerol (GLY) with acetone to produce acetone glycidol (2, 2-dimethyl-1, 3-dioxolane-4-methanol, Solketal) is promising direction for GLY utilization, because Solketal can function as fuel additive to modify the fuel viscosity and low-temperature performance of oil significantly, and reduce the emission of carbon monoxide, small solid particles and other environmentally unfriendly substances further. However, the reaction needs to be accelerated by the catalyst with acid nature, thus the design and modification over the structure and acid properties of catalysts are dominating the process of glycerol ketonization reaction. So, this paper systematically reviews the progress of homogeneous and heterogeneous acid catalysts, and the reaction mechanism in recent years. It is classified based on the structural properties, advantages and characteristics of different catalysts, and influences of their structural properties on catalytic activity. Finally, some future directions for this research field are pointed out.
Abstract: The goal of “carbon peak and carbon neutrality” provides a powerful engine for the transformation of energy structure in China. As response to the sustainable development and energy structure transformation, the development of biomass high-density fuels is necessary, which can provide renewable alternatives for traditional petroleum-based high-density fuels. Herein, the properties and applications of typical petroleum-based high-density fuels including RJ-4 and JP-10 are reviewed. We also introduce the routes for synthesizing RJ-4, JP-10 and other polycyclic fuels from terpenoids and lignocellulose platform compounds, showing the feasibility of converting biomass to high-density fuels. Finally, we emphasize the current bottlenecks and development trends in the synthesis and application of biomass high-density fuels.
Abstract: In this work, the impacts of ChCl/carboxylic acids, molar ratios of hydrogen bond acceptors to donors, pretreatment temperature and time on the delignification of poplar were investigated. Characteristic methods including XRD, FT-IR, GPC, and HSQC were used to analyze the solid residue and extracted lignin for the study of the structural evolution of the three components. The results showed that under low temperature of 90 ℃, the delignification of poplar wood was 91% with ChCl/FA pretreatment. About 63% of lignin was collected and the purity of lignin was 90%. Over 98% cellulose remained intact with Iβ type crystal form, and the crystallinity was 70%. The β−O−4 bond content of extracted lignin was 84.8% (71% of the original β−O−4 bond), and Mn of the lignin was 1400, suggesting the extracted lignin to be an ideal raw material for monophenlics production.
Abstract: The pyrolysis and gasification characteristics of pelletized cyanobacteria during chemical looping process with red mud oxygen carrier were investigated. The objective is to evaluate influence of red mud oxygen carrier on the pyrolysis and gasification behavior. In a fluidized bed reactor effects of reaction temperature (750−900 ℃) and oxygen carrier to fuel ratio (0.1−0.7) on syngas distribution, carbon conversion and its conversion rate, syngas content and ratio of H2/CO in syngas were investigated. The results indicate that the presence of oxygen carrier has remarkably positive effect on the pyrolysis and gasification processes. It improves pressure gradient caused by devolatilization of the sample. Consequently, the volatiles could be released gradually through the relatively developed channels. During chemical looping gasification H2 content in the syngas has the highest concentration of higher than 45%, followed by CO2, CH4 and CO. The increase of reaction temperature or oxygen carrier to fuel ratio leads to increase in carbon conversion. When reaction temperature increases from 750 to 950 ℃, ratio of H2/CO in the syngas decreases from 7.26 to 4.83. Meanwhile, with increasing oxygen carrier to fuel ratio, ratio of H2/CO first increases and then decreases, and the peak is 5.6 as oxygen carrier to fuel ratio is 0.5.
Abstract: Torrefaction atmosphere is one of the key problems in industrial application of torrefaction technology. In this paper, the effects of oxygen concentration and torrefaction temperature on the physicochemical properties of rice straw during oxidative torrefaction were investigated by simulating the atmosphere of oxy-fuel combustion flue gas. The results show that the effect of temperature on oxidative torrefaction is more significant compared with oxygen concentration. At low temperature (< 250 ℃), oxygen concentration has little effect on the mass and energy yield of torrefied rice straw, but it has obvious effect at high temperature (> 250 ℃). With the increase of temperature (> 250 ℃), the mass and energy yields of torrefied rice straw decrease significantly. When the temperature and oxygen concentration are 250 ℃ and 6%, respectively, it is a suitable oxidative torrefaction condition. Under this condition, the mass and energy yields of torrefied rice straw can be maintained above 70% and 80%, respectively. Increasing the temperature mainly enhances the torrefaction reaction, and the oxidation reaction has an obvious effect when the oxygen concentration exceeds 6%. The retention ratio of chlorine and potassium has an downward trend with the increase of temperature and oxygen concentration, and the effect of increasing temperature is more significant.
Abstract: In the present study, the fast pyrolysis characteristics of sorbitol were deeply explored and the formation mechanism of the main products was revealed using fast pyrolysis experiments and density functional theory (DFT) calculations. The results show that the fast pyrolysis of sorbitol mainly produces low molecular weight products such as hydroxyacetaldehyde (HAA) and hydroxyacetone (HA), furan-based products such as furfural (FF) and 1-(2-furanyl)-ethanone (2-FE), and anhydrosugar product (isosorbitol (IS)). The yield of HA and HAA products is the highest, due to their lower overall energy barriers. Notably, the generation of HA and HAA are simultaneous. The formation of furan-based products 2-FE and FF needs to overcome relatively higher overall energy barriers, despite that some intermediates also appear in the formation of HA and HAA. Hence, the yields of furan-based products are lower than those of low molecular weight products. The reaction intermediates for formation of anhydrosugar IS are different from those of HA/HAA and 2-FE/FF. The overall energy barrier is high that leads to a very low yield of IS. This study provides a theoretical insight into the mechanism research and technique development for selective pyrolysis of sorbitol.
Abstract: Acetic acid, phenol, guaiacol and 4-methylguaiacol in bio-oil aqueous fraction were extracted and separated experimentally with the choice of hydrophobic ionic liquid [Bmim][NTf2] as extractant. The effects of extraction time and extractant dosage on the extraction efficiency were explored. With the help of density functional theory (DFT) calculations, the interaction mechanism between [Bmim][NTf2] and phenol was also clarified. The results showed that under the optimal extraction condition (mIL/mW = 0.4, extraction time = 5 min), the extraction efficiencies of acetic acid, phenol, guaiacol and 4-methylguaiacol in the aqueous fraction were 2.71%, 95.41%, 92.04%, and 97.98%, respectively. It was indicated that [Bmim][NTf2] had better selectivity and superior extraction efficiency for phenols in bio-oil aqueous fraction. The results of DFT calculation demonstrated that the strong hydrogen bonding interaction as well as weak vdW interaction between [Bmim][NTf2] and phenols played an important role in extraction and dephenolization of bio-oil aqueous fraction. The phenols in [Bmim][NTf2] can be effectively removed by alkali washing treatment to achieve recovery of [Bmim][NTf2] and next high efficiency extraction.
Abstract: Deposition or slagging problem caused by the alkali metal species is one of the major obstacles to utilize biomass fuel in combustion and gasification plant. The paper mainly studies the effect of water leaching on alkali-induced slagging properties of corn straw and rice straw. The original mineral form of alkali elements in biomass straw was studied with comparison of low temperature ash of biomass before and after water leaching. The release and transformation of alkali compounds in biomass straw at different temperatures during heating were analyzed with combination of the XRD result of the heated biomass and the chemical composition of the digested samples. The result shows that the potassium in corn and rice straw mainly exists in the form of KNO3, KClO4, K2SO4 and KAlSi3O8, in which KNO3, K2SO4 and KClO4 is mostly removed in water leaching. The fusion temperatures increased after water leaching, especially for rice straw ash, which is a typical sample that the basic compounds are mainly potassium-containing compounds. The decrease of potassium content with temperature in the original corn and rice was because the potassium-containing minerals decomposed and escaped at 25−1000 °C. The release of potassium in the range of 400−800 °C significantly reduced for corn and rice straw after water leaching, but the potassium content will still decrease above 800 °C. The decrease of magnesium content in corn with increasing temperature may be due to the volatilization of magnesium oxide under the action of carbon reduction. For fuels with high alkali metal content after water leaching, the residual alkali metal will still escape and cause deposition or slagging in the furnace, especially in the temperature range above 800 °C.
Abstract: Ru/HZSM-5 was prepared and used to upgrade bio-oil online and the changes of bio-oil yield and physicochemical properties were analyzed through the total quality index ( TQI ). The changes of the chemical compositions of the bio-oils were compared; simultaneously, the coking situation of the catalyst was characterized. The results showed that the yield and physicochemical properties of bio-oil obtained by using fresh catalyst were high, and the TQI increased from 0.15 to 6.45; with the increase of using times, the TQI first increased slightly to 6.68, then decreased rapidly to 1.25, and reduced to only 0.27 after the fourth usage. In the initial stage, a small amount of coking reactions made the strong acid sites partially passivated, which improved the aromatization performance. When the catalyst was used twice, the relative content of hydrocarbons in the bio-oil reached 53.79%, of which the relative content of light aliphatic hydrocarbons was 16.87%, and the relative content of monocyclic aromatic hydrocarbons was 32.65%. After the fourth usage, the relative content of hydrocarbons in the bio-oil was only 9.32%, and the catalyst layer basically lost the upgrading effect, and had adverse effects on pyrolysis vapors such as secondary cracking or polymerization. Before the third usage, the low-temperature pyrolytic coke attached to the catalyst surface was dominant. After the third usage, the low-temperature pyrolytic coke and high-temperature catalytic coke increased significantly, and the catalyst activity decreased sharply. Continuous usage of catalyst slightly increased coke, of which the pyrolytic coke increased mainly.
Abstract: In order to reduce N-/O-compounds content and improve the quality of microalgae bio-oil, the co-pyrolysis/catalytic of Nannochloropsis sp. (NS) and polyethylene (LDPE) were studied in a fixed bed, and the distribution of N and O was discussed, as well as the interaction between microalgae and LDPE and the influence of the addition of catalyst. It was found that co-pyrolysis could effectively inhibit the transformation of O and N to oil, and promote the O release as H2O and N conversion to gas products. In addition, plastic adding significantly reduced the content of O-/N-compounds in oil, such as carboxylic acid, amide and N-heterocyclic, and increased the aliphatics content. Besides, it effectively promoted the formation of hydrocarbon gas, and showed a certain synergistic effect on CO and H2, and the interaction reached the maximum at 25%LDPE. Furthermore, ZSM-5 could promote the formation of hydrocarbon gas, increase the LHV of gas products (35.6 MJ/Nm3), and further reduce the nitrogen compounds in the oil, while the N in microalgae transferred to gas, and O converted to gas and H2O, which resulted in the further reduction of the O and N contents in the oil. Moreover, catalytic co-pyrolysis could inhibit the formation of aromatic hydrocarbons to a certain extent and improve the selectivity of aliphatic hydrocarbons.
Abstract: In this paper, Ru/solid base catalysts were employed to realize the direct hydrogenolysis of furfuryl alcohol into tetrahydrofurfuryl alcohol and 1,2-pentanediol. Moreover, the catalyst preparation, activation and reaction conditions were screened. It was found that the yield and selectivity of 1, 2-pentanediol were improved by the preparation of Ru based catalyst with basic metal oxides as support. The total yield of tetrahydrofurfuryl alcohol (53%) and 1, 2-pentanediol (32%) was 85% under the optimal reaction conditions over Ru/MnO2. Subsequently, N2 adsorption-desorption, XRD and XPS were employed to reveal the catalytic mechanism which suggested that the synergistic between the surface basic groups and active metals might account for the better catalytic performance.
Abstract: β–O–4 is the most abundant linkage in the lignin structure. It is of great significance to convert lignin into monophenols by breaking the β−O−4 linkage. Therefore, β−O−4 dimer model compound was used as raw materials in this paper. The effects of metal catalysts, temperature, time and hydrogen pressure on the conversion of dimer and yield of monophenols were investigated by GC-MS, GC-FID, HSQC NMR characterization methods. The results show that NaOH and carbon-supported metal catalysts have a synergistic effect which can enhance the breakage of β−O−4 linkage, and the best promotion effect is obtained over Pd/C and NaOH with the monomer yield increases from 44.1% to 83.4%. NaOH and Pd/C can inhibit the removal of Cα−OH of the dimer and enhance the breakage of β−O−4 linkage effectively, leading to the increment in monomers. The NaOH and Pd/C catalytic system also shows excellent performance to the breakage of α−O−4. Under the best conditions, alkali lignin is converted into monophenols over NaOH and Pd/C with the yield of 37.5%, and the selectivity of benzyl alcohol is as high as 48%.
Abstract: Lemon peel, as a typical carbon solid waste in fruit processing industry, of which efficient recycling and resource utilization contribute to the development of renewable liquid fuel and economic benefits. Citric acid contained in lemon peel has been proved to be a weak acid that can effectively promote the hydrothermal conversion of biomass and its derivatives to produce high value-added furan products. Therefore, sulfuric acid is used to catalyze the hydrolysis of lemon peel to produce precursor of important liquid fuel, such as levulinic acid (LA) and furfural (FF). The promotion effect of common metal salt on catalysis of sulfuric acid to the hydrolysis process of lemon peel is explored. The citric acid contained in lemon peel promotes the hydrolysis process. Combined with catalysis of sulfuric acid, the LA yield as 22.6% can be obtained under the mild hydrolysis conditions of 170 ℃ and 90 min, and the addition of the KCl can effectively inhibit the secondary reaction of the decomposition process of the lemon peel and enhance the interaction of the sulfuric acid and the lemon peel. Compared with AlCl3 and FeCl3, the LA yield is increased to 27.9% by the addition of KCl. Preparing conditions of glucose and FF are milder than that of LA. Enhancement of temperature and acidic concentration, and prolonging reaction time all lead to significant decrease in glucose and FF yield.
Abstract: The process of directional alcoholysis of cellulose and hemicellulose in bamboo was investigated using solid acid as catalyst and dialkoxymethane/lower alcohol as co-solvent. By adjusting the reaction conditions (composition and ratio of the co-solvent, the type and amount of solid acid catalyst, reaction temperature and time), the optimal reaction conditions were obtained (dimethoxymethane/methanol with a mass ratio of 5 g/15 g, the solid acid catalyst silicotungstic acid 0.002 mol, reaction time 120 min, and reaction temperature 200 ℃), the conversion of bamboo was 81.53%, and the yield of methyl levulinate was 28.39%. At the same time, the conversion process of a variety of biomass model compounds (xylose, glucose, furfural, 5-hydroxymethyl furfural, pentosan and microcrystalline cellulose) was studied in detail, then the fundamental mechanism of directional alcoholysis conversion of cellulose and hemicellulose to produce methyl levulinate was put forward according to the detection results of intermediate products in the reaction process.
Abstract: Xylose is the predominant component of hemicellulose, and converting xylose to valuable compounds is essential to achieve biomass utilization. Herein, N-doped carbon nanotubes encapsulated metal catalysts (Co@NC) with hydrogenation and isomerization capacities were synthesized via bottom-up method for catalyzing xylose hydrogenolysis into 1,2-diols. The physicochemical properties of Co@NC prepared with different calcination temperature were determined by XRD, TEM, XPS and so on. The Co@NC prepared at 600 ℃ exhibited the optimal catalytic activity, and the yield of diols reached 70.1% with ethylene glycol, 1,2-propylene glycol and 1,2-pentanediol being 17.6%, 25.1% and 27.4%, respectively. The doping N species served as the basic sites which benefited the isomerization of xylose to xylulose. Xylulose was subsequently converted to glycolaldehyde and acetol through Retro-aldol reaction, followed by hydrogenation to produce ethylene glycol and 1,2-propylene glycol. 1,2-Pentanediol derived from the selective hydrodeoxygenation of xylose, the yield of which surpassed the results that had been reported. The Co@NC catalysts with high robustness under harsh hydrothermal conditions provided new insights into the effective conversion of lignocellulosic biomass to 1,2-diols.
Abstract: Catalytic cracking of triglycerides and their derivatives (e.g., fatty acid methyl esters, FAMEs) by HZSM-5 zeolite offers a promising route to produce renewable aromatics and olefins, but it is primarily hindered by the rapid catalyst deactivation caused by coke. In this work, the co-cracking of FAMEs and methanol over HZSM-5/Al2O3 composites was developed to regulate the product distribution and slower the catalyst deactivation. Co-feeding methanol with FAMEs enhanced the olefin selectivity at the expense of aromatics, and the total selectivities of aromatics and olefins added up to 70.9% with an optimized methanol content of 60%. The co-feeding of methanol not only promoted the olefin yield but also retarded the consecutive H-elimination of aromatics to polycyclic aromatics, thus reducing the coke formation and prolonging the catalyst lifespan. Under the conditions of 450 °C, 0.16 MPa and a space velocity of FAMEs at 4 h−1, increasing the methanol blending ratio in FAMEs from zero to 50% reduced coke from 17.8% to 10.1% after reaction for 12 h. Besides, the spent catalyst for the co-cracking reaction could be easily regenerated by coke combustion, yielding similar structure, acidity and activity to those of the fresh one.
Abstract: Catalytic lignin depolymerization (CCLD) for liquid fuels and phenolic monomers was investigated over various supports including clays (e.g., sepiolite (SEP), attapulgite (ATP), and montmorillonite (MTM)), and oxides (e.g., Al2O3 and SiO2) as well as their supported Mo-based catalysts under supercritical ethanol. The characterization results demonstrated that different supports with diverse structural properties could affect the textural structures, surface Mo5+ content, and acid sites distribution. Clay-based supports had more strong acid sites as compared with Al2O3 and SiO2, which went against the production of lignin oil (LO) and led to form more solid products during CLD experiments. Meanwhile, the obtained petroleum ether-soluble product (PEsp) in LO catalyzed by sole supports was mainly alkyl/alkoxy substituted phenols. Additionally, Mo species (especially Mo5+) significantly increased the yields of LO and PEsp. Mo/SiO2 had the highest surface Mo5+ species, showing the highest LO yield of 85.2%, in which the produced alkyl/alkoxy substituted phenols reached 450.3 mg/glignin. Among the clay-supported Mo catalysts, Mo/SEP presented superior LO (82.3%) and PEsp (70.8%) yields and the generated substituted phenols reached 398.8 mg/glignin. This paper systematically reported the application of green and environmentally friendly clay-based materials in lignin conversion, which provides some key information for the development of clay catalysts for biomass conversion.
Abstract: After the fuel undergoes pyrolysis and combustion in a biomass boiler, the fly ash contains some unburned carbon with abundant pores. However, their low porosities and specific surface areas cannot meet the requirements of the activated carbon for commercial supercapacitors, and the activation method to improve their pore structures is the key to enhance their applicability. After the one-step KOH activation treatment of the unburned carbon with the particle sizes > 0.2 mm, the results showed that the activated carbon has the largest specific area (1982 m2/g) at an impregnation ratio of 3.5∶1, and the specific capacitance reached 207 F/g at the current density of 1 A/g. The above results indicate that unburned carbon-based activated carbon has a good double layer capacitance performance, providing a reference for the high value-added utilization of biomass fly ash.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
