Abstract: Dry reforming of methane (DRM) technology, converting two kinds of greenhouse gases (CH4 and CO2) into syngas to achieve greenhouse gas emission reduction and resource utilization, has attracted more and more attention from researchers. Due to the advantages of high specific surface area, developed porous structure, high thermal stability, excellent acid and alkali resistance, abundant content of alkali/alkaline earth metals and oxygen-containing functional groups, and low cost, bio-char is suitable for different DRM systems, including shale gas, oil field associated gas, coke oven gas and coal bed methane systems, which can avoid some pretreatment processes such as desulfurization of part of the exhaust. Therefore, bio-char may offer attractive prospects for large-scale DRM industrial applications. Herein, the review briefly summarizes the preparation process of biochar-based catalyst supports for DRM. The different carbonization procedures and their effects on the yield and properties of bio-char are briefly described. The advantages and influence factors of the physicochemical property of bio-char in the reforming reaction are introduced. The influence of different activation methods on the catalytic performance of biochar-based catalysts is also analyzed. Finally, the carbon consumption that affects the stability of the catalyst is briefly introduced.
Abstract: The development of novel carbon dioxide capture or utilization technology is of great significance to reduce carbon dioxide emissions from fossil energy utilization, as well as to alleviate global warming. The integrated carbon dioxide capture and utilization (ICCU) technology, which integrate carbon dioxide adsorption and in-situ conversion to realize efficient conversion of carbon dioxide to carbon containing fuels over dual function material, has attracted extensive attentions due to its advantages of low energy consumption and high efficiency. In this paper, the composition and characteristics of the dual function materials for CO2 capture and methanation were summarized. The factors which affected the methanation process were discussed from the perspectives of reaction temperature, reaction time, feed gas compositions. The challenges and opportunities in the near future were also proposed.
Abstract: The three-component coupling of methanol, CO2 and propargyl alcohol to manufacture dimethyl carbonate (DMC) provides a new, thermodynamic favorable and green chemical synthesis route. In this work, to overcome the problems of low DMC yield and slow conversion rate of intermediates, the synergistic catalytic strategy of silver sulfadiazine and superbase is developed to improve the reaction efficiency. The effect of various parameters i.e. catalyst and cocatalyst types, catalyst loading, solvent, temperature, proportion of raw materials, pressure and time on the coupling reactions is investigated in detail. Under the optimal conditions, the selectivity of DMC is 89.5% with the yield of 55.6%. And the effect of alkyne derivative α-monosubstituted propargyl alcohol on the efficiency and selectivity of DMC are also studied. The mechanism study shows that propargyl alcohols with different structures apparently affect the reaction process, and the synergistic catalysis of silver sulfadiazine/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is the reason for the high yield and selectivity of DMC.
Abstract: In this study, we used density functional theory to study the adsorption and activation capacity of Cu13, Cu12Zn, and Cu12Zr clusters for CO2 reduction. The calculated results showed that Cu12Zr enhanced the adsorption capacity of reactants and intermediates compared with Cu13 clusters, while Cu12Zn clusters decreased the adsorption capacity of reactants and intermediates. We calculated that the energy barriers for CO2 reduction to CO on Cu13, Cu12Zr, and Cu12Zn clusters were 0.65, 0.35 and 0.58 eV, respectively, and the energy barriers for CO2 plus H to generate HCOO were 0.87, 0.77 and 0.49 eV, while the energy barriers of CO2 hydrogenation to COOH were 1.67, 1.89 and 0.99 eV. The doping of Zn and Zr elements improved the CO2 catalytic reduction ability of the Cu clusters, which showed that the Cu12Zr clusters were favorable for the dissociation of CO2 to form CO, and the Cu12Zn clusters were favorable for the hydrogenation of CO2 to HCOO.
Abstract: With dolomite as the main aggregate, a clay ceramic carrier was prepared by one-step powder sintering method. After being impregnated with Ce and calcined, a Ce loaded dolomite based (Ce-Dol) clay ceramic catalyst was prepared, which was used for the catalytic gasification of pine wood. The influence of the addition amount of Ce, steam flow rate, gasification temperature and other parameters on the catalytic gasification of pine wood was investigated using a self-developed two-stage gasifier, and the optimal operating conditions were determined. The results show that the dolomite based clay ceramics loaded with cerium can effectively improve the catalytic activity, reduce the stretching vibration peak absorbance of some functional groups in the gasification products, effectively promote the secondary cracking of tar, and improve the quality of gaseous product. When catalyzed by the Ce-Dol clay ceramic containing 6% cerium, the volume fraction of H2 peaks with 32.43%. With the rise in gasification temperature, aliphatic carboxylic acids and ketones in biomass tar are gradually decomposed into small molecular compounds such as CO, CO2. The content of H2 shows an ascending trend, and a maximum value is reached at 900℃. Moreover, adding an appropriate amount of steam promotes the forward water-gas reaction, and a maximum volume fraction of H2 (37.37%) is achieved at a steam flow rate of 4 mL/min.
Abstract: The isothermal steam gasification experiments of a ternary mixture (BTP) containing black liquor char (BLC), causticizing agent (TiO2), and petroleum coke (PC) were carried out at 850 °C based on a thermogravimetric analyzer (TGA) and a horizontal fixed-bed reactor. A co-gasification process of BLC and PC coupled with TiO2 direct causticization was explored from the aspect of reaction rate as well as the characteristics of gaseous products and gasification residues (GR). The results show that in comparison to the weighted average (BTPtheo) of the independent gasification of TiO2 direct causticized BLC and PC, significant synergistic effects could be aroused during the coupled co-gasification process due to promoting action of mNa2O·nTiO2 on gasification of organic carbon. Specifically, the maximum reaction rate of BTP reaches 7.0%/min, which is 2.9 times that of BTPtheo. The content and yield of effective gas components, i.e., H2+CO, in the gas products, as well as its lower heating value (LHV) of BTP are 81.1%, 2059 mL/g, and 9343 kJ/m3, respectively, which is 6.8%, 137.3%, and 5.5% higher than that of BTPtheo. The carbon conversion and energy output ratio of BTP reaches 95.0% and 1.13, respectively, which is increased by 61.6% and 135.4% relative to the theoretical superposition value. In addition, the relative loss of inorganic salts in BTP during the whole thermochemical conversion process is effectively controlled at a lower level of about 9.4%. Since the Na-containing salts in GR of BTP are mainly mNa2O·nTiO2 with higher thermal stability, and GR maintains good particle flowability, it is conducive to downstream alkali recovery.
Abstract: Thermal degradation mechanism of polybutylene terephthalate (PBT) dimer was studied by density functional theory (DFT) method M06-2X/6-311G(d). Eight possible reaction paths were designed for the thermal decomposition of PBT dimer, and the thermodynamic and kinetic parameters of elementary reaction steps in each reaction path were calculated. Calculation results show that, in the initial pyrolysis process of PBT, the energy barrier of concerted reaction occurring on the main chain is significantly lower than that of the radical reaction, so terephthalic acid, monobutenyl terephthalate, dibutenyl terephthalate and diterephthalate-1,4-butadiester formed by concerted reaction are main products in PBT initial pyrolysis. The energy barrier of the main chain fracture through the six-membered cyclic transition state is lower than that through the four-membered cyclic transition state, and the main chain fracture of PBT is mainly through the concerted reaction with six-membered cyclic transition state. In addition, the secondary degradation reaction of the main products of PBT pyrolysis was also discussed. It is found that the main products such as 1,3-butadiene, tetrahydrofuran, benzene, CO2 and benzoic acid are mainly generated through concerted reaction in the processes of secondary degradation.
Abstract: Elemental distribution, compositional variation, microstructural feature, surface pore structure, pyrolysis characteristic and reactivity of samples derived from inert/oxidative torrefaction performed in 493–573 K were investigated. The results illustrated that reaction temperature was the dominant factor affecting fuel quality of torrefied sample, and the addition of oxidizing agents would strengthen the variations in fuel properties after undergoing torrefaction. Increasing reaction temperature would promote the decomposition of oxygen containing functional groups from the particles, when torrefaction performed in raw flue gas atmosphere at 573 K, the H/C and O/C reached the minimum values (0.188 and 0.259). Additional oxidizing agents would synergistically modify the surface functionality distribution, microstructure and surface physical structure of rice husk particles, and the increase of temperature was beneficial to this phenomenon. The critical values were obtained from the sample torrefied in raw flue gas atmosphere at 573 K, the minimum I(Gr + VL + Vr)/ID value was 1.79 and the maximum specific surface area was 295.78 m2/g. By means of the utilization of Coats-Redfern approximation function, the pyrolysis kinetics (14.84 → 28.82 kJ/mol) and characteristic parameters would be determined via the TGA data for each sample. Flue gas seemed to be more energy-saving and efficient for improving fuel quality and storage stability of biomass.
Abstract: Pyrolysis is an important technology for the harmless reduction of food waste. In this paper, thermogravimetric analysis was used to analyze the pyrolysis characteristics of three typical seafood wastes, namely fish bones, crab shells, and shrimp shells, and to study the characteristic parameters of the pyrolysis process at different heating rates (20, 40, and 60 ℃/min), to analyze the effect of different components on the pyrolysis characteristics of seafood waste. The kinetic analysis of the pyrolysis process was carried out based on the pyrolysis characteristic parameters, combined with the apparent kinetic parameters and the fitting effects of various mechanism models were compared, and a more suitable mechanism model for the pyrolysis process of seafood waste was determined. The results showed that the pyrolysis processes of the three seafood wastes were closely related to their components, and the comparative analysis of TG-DTG curves found that the content of organic matter and inorganic salts were important factors affecting the pyrolysis process. The pyrolysis characteristic parameters of the three seafood wastes showed a consistent increasing trend with the increase of the heating rate. The main pyrolysis process of fish bones conforms to the first-order chemical reaction mechanism, and the organic matter decomposition stage of crab shells and shrimp shells can be described by a 1.5-order chemical reaction process. The large amount of chitin in shrimp shells and crab shells is the main reason for the difference in the order of chemical reactions. The activation energy increases with the increase of the heating rate, while the increment of the activation energy gradually decreases. It could be presumed that the adoption of larger heating rates over 40 ℃/min would probably not arise more severe pyrolysis condition, which would be more economical from technical view. The results achieved in this paper may provide some fundamentals for competitive technology development for seafood wastes pyrolysis and carbonization.
Abstract: The complexity and diversity of lignin derived bio-oil (LDB) has posed a great challenge to the subsequent processing and utilization. In this work, HZSM-5 was modified by sodium hydroxide and followed by Ni, Cu and Ru species. LDB was used as the raw biocrude to prepare bio-oil rich in aromatic hydrocarbons with modified HZSM-5 catalysts under supercritical ethanol conditions (320 °C, 14 MPa). Results showed that the desilicated HZSM-5 with the loading of Ni, Cu and Ru (Ni-Cu-Ru/DeHZSM-5) exhibited the best catalytic performance with a high relative amount of aromatic hydrocarbons of 28.95%. After catalytic hydrodeoxygenation (HDO) of LDB, 80.40% upgraded bio-oil (UBO) with 96.32% energy recovery was obtained in the presence of Ni-Cu-Ru/DeHZSM-5. Demethoxylation and dehydration were the main reactions in the catalytic HDO process. Potential reaction pathways of guaiacol, syringol and creosol were also proposed in this paper. The heating value of UBO reached 35.22 MJ/kg compared with LDB, which was increased by 19.80%. The water content and viscosity of UBO were also significantly improved. The micro-mesoporous structure of modified HZSM-5 with loading of Ni, Cu and Ru was beneficial to promote the yield of the aromatic hydrocarbons.
Abstract: In this work, a series of nano LaCoO3 perovskite catalysts were effectively synthesized by a sol-gel method through modulating the La/Co molar ratio. These catalysts were characterized by ICP, XRD, N2 sorption, H2-TPR, O2-TPD, and XPS, and their catalytic performance in the lean methane combustion were then investigated. The results indicate that highly dispersed Co3O4 nanoparticles on the LaCoO3 perovskite catalysts are beneficial to the activation of CH4 at a low temperature, while the La-Co-perovskite bulk phase can provide a large amount of lattice oxygen, which can enhance the reaction rate of methane combustion and the catalytic stability at a high temperature. Through altering the La/Co molar ratio, the dispersion of Co3O4 nanoparticles in the La-Co-perovskite catalyst can be effectively modulated, to achieve the concurrence of low-temperature activity and high-temperature stability in the lean methane combustion. In particular, the La0.9CoO3 perovskite catalyst with a La/Co molar ratio of 0.9 exhibits excellent performance in lean methane combustion, with a light-off temperature of 382 ℃ at a space velocity of 30000 mL/(gcat·h), the light-off temperature of methane is 382 ℃, and the methane conversion rate is still maintained above 95% after 72 h of stable operation, indicating that the highly dispersed Co3O4 nanoparticles were beneficial to the low-temperature activation of CH4, and the lanthanum-cobalt-perovskite bulk phase in the catalyst could provide a large amount of lattice oxygen, which promotes the catalytic combustion rate of CH4 and the high-temperature stability of the catalyst under high-temperature conditions. By modulating the lanthanum-cobalt ratio, the dispersion state of Co3O4 nanoparticles in the catalyst can be effectively modulated, and then the effective unification of low-temperature activity and high-temperature stability of the catalyst can be achieved, which guides the future development of low-cost, high-activity and high-stability catalysts for methane catalytic combustion.
Abstract: The modified attapulgite was obtained by acid activation and loaded magnetic nano-ferrite composite modification. The applicability of attapulgite in the adsorption furnace of semi-volatile heavy metal PbCl2 vapor in different flue gas atmosphere was explored. Besides, the adsorption mechanism of PbCl2 vapor was investigated by combining FT-IR, BET, XRD and DFT theoretical calculation. The results show that acid activation increases the proportion of surface-active sites by decomposing impurities in the original ore, and the double active adsorption sites formed by the composite modified iron-based oxides and attapulgite lattice oxygen significantly enhance the adsorption capacity of PbCl2. The maximum adsorption capacity of Fe/HP2 samples with the mass ratio of 1∶2 is 67.62 (mg PbCl2/g adsorbent). When the high-temperature flue gas contains O2, SO2 and a small amount of H2O, it can enhance the adsorption capacity of modified attapulgite. In addition, DFT theoretical calculations show that H2O, O2, SO2 and PbCl2 all undergo chemisorption on the surface of ATT(110), and it also demonstrates that H2O promotes the adsorption of PbCl2 on the surface of ATT(110) and Fe/ATT(110) through co-adsorption. Weaker adsorption of PbCl2 at the adsorbed oxygen sites formed by H2O molecules instead of at the lattice oxygen sites can be preferentially bond to double active sites (the lattice oxygen sites and the oxygen site) in the iron oxide clusters through strong interactions on the Fe/ATT(110) surface.
Abstract: The fusibility and viscosity-temperature characteristics of municipal solid waste (MSW) ash slag are important to the optimize design and operation of fixed bed slag gasifier. In this paper, the ash composition characteristics of two MSW samples were analyzed, and the melting mechanism of MSW ash was explored by high temperature heating stage microscope (HTSM), X-ray diffraction (XRD) and FactSage. At the same time, the effect of crystal mineral formation on ash viscosity was analyzed by high-temperature viscometer, SEM-EDS and XRD. The results show that the silica to aluminum ratio of MSW ash are both high, but the contents of aluminum and calcium are different. The flow temperature of YZ ash is about 150 ℃ higher than that of LG ash. Low temperature eutectic of wollastonite is the reason for the lower melting point of LG ash, and the existence of quartz and spinel at high temperature leads to a higher melting point of YZ ash. Ash melting behavior of LG and YZ are both "melt-dissolution" mechanism, and they both undergo shrinkage, melting and diffusion processes with the increase of temperature. The viscosity-temperature curves of LG and YZ are both glassy slag. However, the viscosity-temperature characteristics of YZ ash are relatively poor, which is related to the formation of anorthite during the cooling process. So the application of YZ requires a high slag discharge temperature. LG ash has good fusibility characteristics and viscosity-temperature characteristics, so the gasifier with this material can operate in a wide temperature range.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
