Abstract: A fixed bed reactor and atomic absorption spectroscopy were used to investigate potassium recovery efficiency of Yulin coal loaded with potassium carbonate (ZA-K), Yulin demineralized coal loaded with potassium carbonate (ZA-THK) and synthetic ash (Configurations of four oxides: SiO2, Al2O3, CaO, Fe2O3) loaded with potassium carbonate after reaction. Fourier infrared spectroscopy and Raman spectroscopy were used to study influence of structural evolution of ZA-K and ZA-THK on migration of potassium during pyrolysis. The results show that the yield of water-soluble potassium decreases with increasing temperature. Three times water washing could recover 94.06%−98.80% of the total water-soluble potassium. Formation of insoluble potassium is due to the phase of potassium aluminosilicate formed by potassium, silicon and aluminum in the coal ash. Potassium is easier to volatilize from ZA-THK than that from ZA-K. At 700−850 ℃ potassium in ZA-THK is volatilized 10.28%−44.92% higher than that of ZA-K, resulting from that the ash in ZA-K would fix the loaded potassium in coal ash. Another reason may be caused by decrease in the degree of aromatic polymerization of ZA-THK through demineralization process, leading to more small-ring aromatic structures (2−8 rings) appearing in the coal.
Abstract: The co-combustion of the low-rank coal with coal derived semi-coke is of great significance to solve the urgent problem of excessively produced semi-coke in China. In this research, the oxy-fuel co-combustion characteristics of Zhundong sub-bituminous coal with bituminous coal derived semi-coke are systematically investigated using thermogravimetric analysis. Compared with air combustion, oxy-fuel atmosphere increased the ignition and burnout temperature by 10 and 40 °C, respectively. Increasing the oxygen concentration to 30% strongly compensated for the slight reduction of the combustion parameters under oxy-fuel condition and much better co-combustion performance was obtained. Three iso-conversional methods, namely, Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Starink, were applied to estimate the activation energy, which can be divided into two stages during the co-combustion process. The average activation energy of sub-bituminous coal, the blend and semi-coke were 49.31, 50.82 and 59.00 kg/mol, respectively. Further, the pre-exponential factor and thermodynamic parameters of the enthalpy change, Gibbs free energy change and entropy change were calculated. Interaction indices were innovatively used for both kinetic-thermodynamic parameters and DTG values. An obvious interaction can be observed during the co-combustion process. The kinetic and thermodynamic results demonstrated that the 30% semi-coke ratio was beneficial to co-combustion. Meanwhile, X-ray fluorescence (XRF) and ash fusion analyses proved that the slagging tendency of sub-bituminous coal ash reduced by blending of semi-coke.
Abstract: Efficient separation and high-valued utilization of coal gasification ash or slag limit the clean and green development of coal chemical industry. In this paper, a coal-water slurry gasification fine slag (CWSFS) was studied by wet screening and classification. The relationship between the particle composition with different sizes and the structural characteristics was investigated by means of proximate analysis, XRF, XRD, BET and SEM. A classification method of CWSFS was proposed to guide the high-valued utilization of coal gasification slag. Then, dry separation of a coal-water slurry gasification fine slag was carried out using a combined treatment method of crushing and dissociation and airflow classification. The results show that the CWSFS particles of different sizes have obvious differences in fixed carbon content, ash composition and mineral types. For the CWSFS with the particle size above 74 μm, the fixed carbon content is more than 60%, the calorific value is more than 20 MJ/kg, the specific surface area is relatively high and the main component is the residual carbon that contains magnetite and brookite. For the CWSFS with particle sizes between 13−74 μm, the fixed carbon content is between 20%−60%, the calorific value is between 11−19 MJ/kg, the specific surface area is small and the main mineral types are pyroxene, marcasite and hematite, etc. For the CWSFS with a particle size between 0−13 μm, the fixed carbon content is less than 20% and the calorific value is less than 10 MJ/kg, which mainly includes the amorphous glass phase that was rich in aluminum, iron and calcium, quartz and a small amount of fayalite, muscovite and other minerals. According to the fixed carbon content of CWSFS with different particle sizes, the above three components with varying particle size ranges are defined as high-carbon component, medium-carbon component and low-carbon component, respectively. The dry separation test shows that the air flow crushing and classification process can achieve a higher product yield of 29.60% and a high ignition loss of 93.76%, compared to the traditional disc crushing-classification process. Airflow crushing was proved to be able to effectively increase the dissociation degree of residual carbon and greatly improve the separation and enrichment rate of residual carbon.
Abstract: The pore structure of coal gasification fine slag in Ningxia was characterized and analyzed by low temperature nitrogen adsorption, scanning electron microscope and low field NMR. The pore morphology is mainly fracture shape, and the BET specific surface area of each particle size is large, which is 125.78−589.78 m2/g. The SEM analysis shows that the BJH pore diameter is quite different from the actual situation, and the analysis of pore structure only by low-temperature nitrogen adsorption method has certain limitations. The low field NMR method shows that the products pore sizes of all particle sizes contain micropores, transition pores, mesopores and macropores, and the total porosity is about 27%, mainly mesopores and macropores, followed by micropores and transition pores. The pore structure shows that the products of different particle sizes of coal gasification fine slag have certain adsorption properties, but the medium and large pores are the main storage space of water, resulting in difficulty in dehydration.
Abstract: The clean and efficient utilization of carbon resources is becoming more and more important, in energy, material, and chemical engineering field, but the mechanism of coke oxidation, especially that of the CO2/CO desorption is not fully studied yet. In this paper, density functional theory was used to study the oxidation mechanism of Zigzag char structure with high coverage of O2, which is related to an oxidation under lower temperature or high pressure. Based on the corresponding quantum chemistry calculation, it is shown that there are several possible pathways for the CO2 desorption process, which may need rearrange to form the structure containing O−C−O clusters. And successively, multiple intermediate reaction steps are required to complete the desorption of CO2. Other than in the literature that the COO–O–C functional group formed first, with then the C–O bond broken and CO2 desorbed respectively, a novel pathway with two C–O bonds broken simultaneously to generate CO2 was found. It results from a functional group of COO–char formed, and certain alternative pathways via C–C bonds breaking were also dealt with, as well as related CO desorptions. The reaction model built was validated by theoretical and experimental results from literature satisfactorily.
Abstract: The catalytic performance of three LaBO3 perovskites including LaCoO3, LaFeO3 and LaNiO3 in the liquefaction of lignin was investigate through a series of experimental characterization methods such as GC-MS, FT-IR and elemental analysis as well as DFT calculation. The effects of reaction time, temperature, catalyst amount and B cation on the lignin conversion, bio-oil yield and products distribution were considered. The results indicate that all three perovskite catalysts can promote the liquefaction of lignin to produce aromatic compounds; among them, LaCoO3 shows the highest catalytic performance, following by LaNiO3 and LaFeO3. In particular, by using 5% LaCoO3, the bio-oil yield achieves 67.20% after reaction at 180 °C for 60 min, whilst the relative content of mono-aromatic compounds reaches 89.59%. The adsorption of oxygen atoms on the LaBO3 crystal surface conduces to the decrease of bond dissociation energy for lignin (LaCoO3 shows the moderate redox capacity and greatest adsorption energy), whilst the loose and porous morphology can effectively promote the fracture of C−C and CAr−OCH3 of lignin. All these contribute to the macromolecular depolymerization and demethoxylation reaction, producing high value-added compounds such as phenol.
Abstract: Light aromatics are extremely important building blocks in the chemical industry which can be produced from the co-catalytic fast pyrolysis (Co-CFP) of biomass and waste plastics. In this work, torrefaction pretreatment was first employed to remove the oxygen element from bamboo for improving the the quality of bamboo. Then, the hierarchical HZSM-5 was prepared by alkali pretreatment of HZSM-5 using Na2CO3 solution. At last, the optimal operation condition was investigated during Co-CFP of bamboo and high-density polyethylene (HDPE). Results showed that during torrefaction pretreatment process, the carbon content of bamboo gradually increased with the increase of torrefaction temperature, while the oxygen content decreased. The oxygen removal rate and HHV reached their maximum value of 40.3% and 25.64 MJ/kg at 300 ℃, respectively. The specific surface area, pore volume of mesopore, and average pore size of HZSM-5 increased after alkali pretreatment, indicating the development of the micro-mesoporous hierarchical structure in HZSM-5. The Diels-Alder reaction between the furans from pyrolysis of bamboo and the light olefins from pyrolysis of HDPE was the most important synergistic catalytic reaction which could highly promote the formation of light aromatics. The maximum yield of BTX (benzene, toluene, and xylene) was 3.05×108 p.a./mg when the torrefaction temperature, the concentration of Na2CO3, the mass ratio of torrefied bamboo and HDPE, and the pyrolysis temperature were 250 ℃, 0.6 mol/L, 1∶2, and 800 ℃, respectively.
Abstract: A series of non-sulfurized K-Ni-Mo-based catalysts with close contact between Ni and K2MoO4 were prepared by hydrothermal reduction for higher alcohol synthesis from syngas. The as-prepared catalysts were characterized by XRD, N2 adsorption-desorption, H2-TPR, HR-TEM, SEM-EDS, XPS, H2-TPD, CO-TPD and CO2-TPD techniques. The results indicate that the introduction of K facilitates the formation of the K2MoO4 phase while brings about a decrease of NiMoO4. It can significantly assist the non-dissociative activation of CO for insertion and subsequently alcohol formation. Moreover, the addition of K increases the surface basicity, which leads to more amount of basic hydroxy groups on the catalytic surface. The catalytic basicity ameliorates the production of alcohols. In particular, the K0.4-Ni-Mo catalyst shows the best catalytic behavior with CO conversion of 19.6%, total alcohol selectivity of 57.8% and C2+ alcohol selectivity in the total alcohols of 66.5% at GHSV of 5000 h−1, 240 °C, and 5 MPa.
Abstract: Methyl glycolate (MG) is a high value-added chemical intermediate and widely used in the fields of medicine, chemical industry, fodder and dyes. A series of CuAg/SiO2 catalysts were prepared by sol-gel method for hydrogenation of dimethyl oxalate to MG. The structure of catalysts was characterized by XRD, N2-physical adsorption, FT-IR, TEM, H2-TPR, and XPS, and the influence of Ag loading on catalytic performance was investigated. The 5Ag-Cu/SiO2 catalyst with Ag loading of 5% exhibited the best catalytic performance with DMO conversion of 83.7% and MG selectivity of 72.2%. The characterization results showed that introducing appropriate amount of Ag not only improved the dispersion of copper species, but also increased the content of Cu+, thereby improving the catalytic activity of CuAg/SiO2 catalysts. In addition, the electron transfer between Ag and Cu could effectively stabilize Cu+, and eventually improved the stability of the catalyst.
Abstract: Metal oxide-zeolite (OX-ZEO) bifunctional catalysts have been shown to have excellent aromatic selectivity and catalytic stability in syngas conversion; however, low CO conversion hinders their further development. In this paper, a series of In-ZrO2 bi-metallic oxides with In/Zr molar ratio ranging of 1/100−1/1 were prepared. After thoroughly investigated by X-ray diffraction, transmission electron microscopy, N2 sorption, pyridine-adsorbed infrared spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance and temperature programmed desorption technologies, we found that introduction of indium has significantly influence on the catalytic performance due to the variation of sample’s physicochemical properties. Indium species was benefit to the dissociation of H2 that promotes CO activation. Nevertheless, it also induced the formation of more CH4. In-ZrO2 oxide with In/Zr ratio of 1/50 showed CO conversion of 18.2% with the selectivity of oxygenates of 86.4%. After combined with H-ZSM-5, In/Zr=1/50&H-ZSM-5 gave CO conversion of 46.5% with $ {\rm{C}}_{5+} $ selectivity of 62.6% and the aromatic selectivity in ${\rm{C}}_{5+} $ reached 93.4%. However, the catalytic stability of this bifunctional catalyst was gradually decreased due to the aggregation of indium atoms.
Abstract: The NiO/CeO2 catalytic materials were prepared with ball milling method using CeO2 as carrier and Ni as active component with good CO oxidation performance at low temperature. The catalysts were characterized by XRD, BET, H2-TPR, XRF and XPS. The effects of nickel content on the structure and low temperature oxidation performance of CO were investigated. The results show that the Ni-Ce ratio mainly affects the number of lattice oxygen vacancies and the interaction between the active ingredient and the carrier. Among them, When the Ni/Ce mole ratios is 1∶9, there are more oxygen vacancies on the surface of the catalyst, so it shows excellent catalytic performance. When the reaction temperature is 200 ℃, oxygen excess coefficient is 5 and the total space velocity is 60000 mL/(gcat·h), the CO conversion reaches 99.2%. In addition, compared with the traditional liquid phase catalyst preparation technology, ball milling has the advantages of low pollution, low cost and easy operation, which is beneficial to save energy.
Abstract: Double mental cyanide (DMC) is a catalyst for the ring-opening copolymerization of carbon dioxide and propylene oxide. DMC catalysts are organometallic complexes with crystal structure, and their catalytic activity is closely related to crystallinity. The addition of ligand and co-ligand can destroy the cubic crystal structure, increase the amorphous structure and reduce the crystallinity. A number of studies have proved that tert-butanol as the ligand DMC catalyst has high activity, but there are few reports on the use of co-ligand. In this paper, DMC catalyst was modified with different co-complexing agents (Span80, Tween80, D400, D2000), which decrease crystallinity, catalyst particle size and eventually increase catalyst activity. The properties of the catalyst were investigated by copolymerization of PO with CO2. The results showed that the catalytic activity of DMC+D2000 modified with D2000 as co-ligand was 1547 g/gcat. The molar fraction of carbonate unit in the polymerization product was 25.3%, and the selectivity was 92.1%.
Abstract: MgO-Al2O3 supports with Mg/Al molar ratio of 0, 0.2, 0.5 and 1.0 were synthesized by coprecipitation method. Mo/M-A0-S, Mo/M-A0.2-S, Mo/M-A0.5-S, and Mo/M-A1.0-S catalysts were respectively prepared by molybdenum loading and followed by prevulcanization processes. Their catalytic performances for hydrogenation of COS in coke oven gas were evaluated in a fixed bed reactor. X-ray photoelectron spectroscopy and Raman spectroscopy were used to characterize the structure and Mo species of catalysts, and the effect of Mg/Al molar ratio on the COS hydrogenation performance of catalyst was investigated. The results show that the changing of Mg/Al molar ratio can modify the physical and chemical structure of MgO-Al2O3 support, the dispersion of Mo and its interaction with catalyst support, and the amount and layer number of MoS2 active sites, so that to improve the activity and selectivity of catalyst. The Mg/Al molar ratio 0.5, which is equal to the stoichiometric ratio of Mg to Al in MgAl2O4, is the most favorite value for MgAl2O4 production. MgAl2O4 can reduce the interaction strength between Mo and catalyst support, enhance Mo dispersion, increase MoS2 amount, and thus promote the catalyst performances. Mo/M-A0.5-S is an excellent catalyst, which can convert 97.7% COS through hydrogenation with H2S selectivity 100% in 550 min at 280 ℃ under the space velocity of 62000 h−1.
Abstract: Cu-SAPO-44 zeolite catalysts were synthesized by one-step hydrothermal method using cyclohexylamine (CHA) and Cu-amine complex (Cu-TEPA) as co-template. They were used for selective catalytic reduction of nitric oxide with propylene (C3H6-SCR) under lean burning condition. These catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectroscopy (UV-vis), NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR). Compared with pure SAPO-44, the introduction of Cu-TEPA significantly enhanced the catalytic activity of C3H6-SCR. When Cu/Al was 0.25, Cu-SAPO-44 catalyst had the largest specific surface area, abundant acidic sites and moderate isolated Cu2+ species, thus it had the best deNOx performance. With the increase of Cu-TEPA introduction, copper species would aggregate on the surface of the zeolite and form more inactive CuO, thus reducing the denitrification activity. In situ study by DRIFTS indicated that isolated Cu2+ could contribute to the adsorption and activation of NO and C3H6, thus enhancing in the formation of −NCO, which was a key intermediate of the reaction. The Cu-SAPO-44 catalyst maintained more than 60% NOx conversion and more than 90% N2 selectivity in long term test of 50 h, showing appropriate reaction stability.
Abstract: Mo2C was synthesized by a high temperature solid state method using ammonium molybdate ((NH4)6Mo7O24·4H2O) and dicyanodiamine (C2H4N4) as rawmaterials, then Mo2C/ZnIn2S4 composite was prepared by in-situ growth method. The composition, structure and properties of the materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-vis diffuse reflection (UV-vis) and Kelvin probe (KP). The results show that ZnIn2S4 grows in-situ on the surface of Mo2C particles and forms Mo2C/ZnIn2S4 heterojunctions. The hydrogen evolution rate of Mo2C/ZnIn2S4 composite reaches 1.33 mmol/g/h, which is 5.1 times to that of bare ZnIn2S4. The photocatalytic mechanism analysis shows that Mo2C, as a cocatalyst, has metallic properties, high conductivity and high surface work function. After Mo2C/ZnIn2S4 heterogeneous interface formed between Mo2C and ZnIn2S4, the Mo2C/ZnIn2S4 composite can effectively promote the separation and migration rate of photogenerated charges in ZnIn2S4. Meanwhile, Mo2C becomes the active site of hydrogen evolution reaction due to its low hydrogen evolution overpotential, which effectively reduces the overpotential of ZnIn2S4 in hydrogen evolution reaction, and subsequently improves the photocatalytic hydrogen evolution activity of the composite material.
Abstract: In a fixed bed reactor, the release characteristics of As and Pb and the composition of ash in the combustion/gasification process of different types of organic solid wastes at 800−1100 ℃ were studied. The effects of CaO, SiO2 and Al2O3 on the migration and transformation of heavy metals As and Pb in the gasification process were explored. The results show that the release rates of As and Pb in the organic solid waste gasification process increase with the increase of temperature on the whole, and the release rates of As and Pb in the gasification process are significantly lower than those in the combustion process. The ash yield decreases with the increase of temperature, and the ash mainly contains CaO, Al2O3 and SiO2. Thermodynamic studies show that at high temperature, gasification process mainly produces gaseous As and Pb, while combustion process produces a large number of As2O3 and PbO. The boiling points of As and Pb are higher than those of oxides, so the release rates of As and Pb in gasification process are lower than those in combustion process. Ca3(AsO4)2, Ca2PbO4, PbSiO3 and AlAsO4 can be produced by CaO, SiO2 and Al2O3 reacting with As and Pb below 900 ℃. As the temperature increases, the release rates of As and Pb gradually increase. Therefore, the lower the gasification temperature is, the better it is. The emission of As and Pb in the atmosphere can be reduced by appropriately increasing the contents of Ca, Si and Al in organic solid waste and reducing the contents of S and Cl.
Abstract: On the basis of the principle of Gibbs free energy minimization, a genetic algorithm was used to carry out a comparative study on the heterogeneous thermodynamics of the glycerol etherification with isobutanol, and the glycerol dehydration with tert-butanol to butyl glycerol ethers. Under the conditions in the temperature range of 40−300 ℃, the pressure range of 0.1−0.7 MPa, the feed of 100 mol of glycerol + 600 mol of other reactant, the effects of temperature and pressure on the equilibrium conversions, product selectivities and gas-liquid equilibrium composition were investigated. The results show that for the etherification process, low temperature is conducive to the generation of tri-tert-butyl glycerol ether, while high temperature is conducive to the generation of di-tert-butyl glycerol ether and mono-tert-butyl glycerol ether. The elevated pressures promote the formation of tri-tert-butyl glycerol, while inhibit the production of di-tert-butyl glycerol ether and mono-tert-butyl glycerol ether. For the dehydration process, the equilibrium conversion of glycerol is close to 100%, the selectivity of tri-tert-butyl glycerol ether is more than 90%, the selectivity of di-tert-butyl glycerol ether is less than 10%, and mono-tert-butyl glycerol ether is efficiently converted. The results also show that for the dehydration process, increasing the pressure moves the heterogeneous temperature range to the right, and the liquid phase composition can be adjusted by changing the pressure.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
