Abstract: The liquefaction of Shengli lignite (SL) were studied in the system of syngas (H2+CO) and complex solvent (H2O+THN) and the system of hydrogen (H2) and tetralin (THN). Asphaltene (AS) and preasphaltene (PA) from the two systems were characterized by FT-IR. The results show that both conversion and oil yield of Shengli lignite liquefaction in the (H2+CO)/(H2O+THN) system are significantly higher than those in the H2/THN system. The conversion and oil yield under syngas (H2:CO=1:1) and complex solvent (THN:H2O=1:1) reach respectively 88.79% and 55.47% at 400℃, 4MPa and 30min. The differences in the conversion and oil yield between the (H2+CO)/(H2O+THN) and H2/THN systems are 8.00% and 7.54%, respectively. This suggests that the water-gas shift reaction can produce active hydrogen in the (H2+CO)/(H2O+THN) system, which benefits the hydrogenation of SL and PA. Meanwhile, THN can stabilize the free radicals from SL pyrolysis and dissolve the products (AS and PA) from SL liquefaction. The synergistic effect of two factors results in the improvement of conversion and oil yield. This study shows that it is a new lignite liquefaction technology using the (H2+CO)/(H2O+THN) system.
Abstract: In order to reveal the mechanism of Na2O influence on ash fusion temperatures (AFTs), effect of Na2O on mineral transformation of two coal ashes with different SiO2+Al2O3 levels were investigated by XRD and FT-IR under reducing atmosphere at high temperature. Thermodynamic software package FactSage was used to calculate the ΔG of reactions between minerals to reveal the mechanism of Na2O influence on mineral transformation. It is found that the effect of Na2O on mineral compositions depends on SiO2+Al2O3 levels of coal ash. For ash with 82.89% SiO2+Al2O3 while Na2O content is 5%-20%, albite and nepheline are formed, leading to a decrease of AFTs. However, only nepheline is formed when Na2O content is higher than 20%. For ash with 47.85% SiO2+Al2O3, when Na2O content is less than 10%, no Na-containing mineral is observed. When Na2O content is higher than 10%, Na-containing minerals such as combeite, lazurite and sodium aluminium oxide are formed, resulting in a decrease of AFTs. Furthermore, FactSage results reveal that Na-containing mineral is easily formed at high temperature due to low ΔG of the reactions.
Abstract: Calcium acetate was added into a bituminous coal through physically blending and impregnation to obtain the ble-Ca coal rich in excluded Ca-mineral and imp-Ca coal rich in included Ca-mineral, respectively. The raw coal, ble-Ca coal and imp-Ca coal were burned in a drop tube furnace at 1300℃. The generated particulate matters (PMs) were collected and analyzed to study the influence of different distributions of Ca-mineral in coal on trimodal PM formation during combustion. The results showed that for the three coals, PMs with the ultrafine mode, central mode and coarse mode were all in the size range of < 0.2μm, 0.2-2μm and >2μm, respectively. The included and excluded Ca-minerals can both promote the formation of ultrafine mode PM, and the excluded one had more significant effect. The included Ca-mineral can restrain, while the excluded one can promote the formation of central mode PM. The included Ca-mineral can promote the formation of coarse mode PM, while the excluded one did not have obvious effect.
Abstract: The structural characteristics of 3 coals with different metamorphic degrees were analyzed using high-resolution transmission electron microscopy (HRTEM). Applying FFT-IFFT method, in association with Matlab, Arcgis and AutoCAD softwares, the lattice fringe parameters obtained from HRTEM image were determined using image analysis. The results indicate that the lattice fringes of all the test coal samples exhibit different characteristics. These lattice fringes can be divided into 8 types (1×1-8×8 aromatic fringes) according to the fringe length distribution. Taking the 3×3 aromatic fringe as critical point, the sample ML-8 abundant in 1×1 and 2×2 aromatic fringes while short of 3×3-8×8 aromatic fringes when comparing with sample DP-4 and sample XM-3. The values of d002 obtained from both HRTEM and XRD show a decreasing trend with increasing vitrinite reflectance.
Abstract: Two pulverized coals taken from an entrained-flow pulverized coal gasification unit at different operating periods were adopted as the experimental materials, which were divided into two groups based on the partical size to investigate the effect of raw coal grindability on the uniformity of pulverized blended coal. The coal quality and the ash character of the subsamples were analyzed as well. The results show that the grindability of raw coal has a great influence on the partical size distribution and the uniformity of pulverized blended coal, and the partical size distribution of blended coal is mainly depended on the raw coal with a smaller grindability index. The smaller the raw coal's grindability index, the larger the particle size of the pulverized blended coal. It is therefore concluded that the pulverized blended coal made from similar grindability raw coals is more uniform. On the other hand, different grindabilities of raw coals lead to nonuniformity and segregation of the pulverized blended coal and induce an accumulation of hard coal in the large particles, which will cause the reactivity of the pulverized blended coal decrease.
Abstract: Carbon and oxygen elements were studied to explore the effect of structural differences on wettability of coal dust. Surface distribution characteristics of carbon and oxygen groups in 6 coal dusts with different metamorphic grades were examined through NMR and XPS. The evolution of different types of carbon and oxygen groups was obtained using distance analysis. With increasing metamorphic degree a kind of group changes along with variation of other groups in most case, which is a process of clustering. The carbon in Ar-C, -COOH, CH2 and Ar-O (R-O) has the similar evolution law, the oxygen in -OH and C-O-C is the same case. Factor analysis was used to know effect of group evolution on wettability of coal dust. It is found that Ar-C, as the common factor covering 95.366% to explain coal dust wettability (contact angle), is the main factor of carbon groups; while -OH covering 94.818% is the main factor of oxygen groups.
Abstract: The ash fusion characteristics, physical structure, chemical compositions and gasification reactivity of Zhundong coal (ZD) fly ash from fluidized bed gasification were explored by fusion point analyzer, X-ray fluorescence spectrometer (XRF), scanning electron microscopy (SEM), and thermo-gravimetric analyzer. The results show that the concentrations of minerals in ZD fly ash, such as SiO2, Fe2O3, Na2O, CaO, change greatly during gasification process, but the ash fusion temperature of ZD fly ash is similar to that of ZD. There is a wide particle-size distribution in ZD fly ash, which shows a significant bimodal distribution, and a large difference of elemental compositions for ZD fly ash of different particle size. The reactivity of ZD fly ash increases with the increase in gasification temperature. Compared with the ZD char from pyrolysis, the ZD fly ash has more advanced carbon crystalline structure, a larger surface area and is relatively rich in meso-pores and macro-pores, which results in a higher gasification reactivity.
Abstract: The sequence extraction method was used to analyze the content of alkali metals in different modes of occurrence in Zhundong coal. Most sodium in the coal is water-soluble one, accouting for 59%, while potassium exists mainly in the form of non-soluble aluminosilicates, accounting for 53%. The combustion experiments of Zhundong coal at the temperature ranging from 400 to 950℃ were carried out to study the distribution characteristics of alkali emission between the gas and the solid phase. The results show that the ash yield decreases with the increase in temperature. Sodium releases continuously from coal into the gas phase; However, the content of potassium in the gas phase is lower than that in the solid phase at 400℃, while the content of potassium in gas exceeds that in solid and basically remains the same when the temperature is higher than 500℃. The enrichment of alkali metals in solid occurs and increases with temperature. Moreover, the sodium in the gas phase mainly originates from water-soluble one, and potassium not only releases from soluble ones, but also from non-soluble aluminosilicates. According to the result of XRD, alkali metals will react with SiO2 and Al2O3 to form low-melting-point albite and nepheline.
Abstract: The enrichment characteristics of organic matters were determined by its petrology. The types and contents of macerals in Huadian oil shale were examined with 3 common microscope lighting conditions (transmitted light, reflected polarized light and reflected fluorescent light). Then two separation methods based on density difference were used to study liberation of organic mattes from minerals. A low degree of metamorphism was found for organic matters in Huadian oil shale. The macerals were dominated by bituminite accounting for 85.8%. The contents of vitrinite and inertinite were low. Closely integrated with minerals, the organic matters were formed as organic-mineral aggregates. It was difficult to separate the organic matters from minerals using physical methods. Both the weight loss and differential weight loss of samples with density < 1.40g/cm3 were lower than that of higher density from float-and-sink analysis. This was attributed to that a small amount of vitrinite and inertinite particles was enriched in low density product due to their less integration with mineral matter.
Abstract: The effect of mineral matter on pyrolysis and product evolution of oil shale was studied by GC and FT-IR. Hudian oil shale was treated by sequential washing with HCl and HF/HCl. The results show that carbonate has catalytic effect on conversion of organic carbon and hydrogen from Kerogen to shale oil, which is inhibited by silicate. The H/C atomic ratio in shale oil increases in both carbonate-free and silicate-free oil shale. Carbonate enhances gas yield and inhibits oil yield, while silicate is just opposite. The contents of CO2 and H2 decrease but CO increases in both carbonate-free and silicate-free oil shale. Carbonate can inhibit generation of hydrocarbon in gas product while silicate has catalytic effect on it. All the carbonate and silicate can increase the length and degree of branching aliphatic side chains in shale oil and improve aromatization of the solid product from shale.
Abstract: The homolytic bond dissociation energies (BDEs) of Cα-O and Cβ-O bonds in 27 lignin trimer model compounds were calculated by employing density functional theory methods at M062X level with 6-31++G (d, p) basis set; the effects of various substituent groups (CH3, CH2OH and OCH3) at different positions on the BDEs of Cα-O and Cβ-O bonds were investigated. The results indicated that a single methoxyl group at R2 or R3 has a minor influence on the BDE of Cβ-O bond, whereas two methoxyl groups at R2 and R3 lead to an obvious decrease in the BDE of Cβ-O bond. The decrement in the BDE of Cβ-O bond from the methoxyl groups at R2 and R3 can be enhanced by the methoxyl groups at R4 and R5, but is hardly influenced by the substituent groups at R1. Meanwhile, the BDE of Cα-O bond is gradually reduced when the H atoms at R4 and R5 are successively substituted with methoxyl groups; the decrement in the BDE of Cα-O bond from the methoxyl groups at R4 and R5 can be strengthened by the methoxyl groups at R2 and R3. Furthermore, the methyl and hydroxymethyl groups at R1 can gradually increase the BDE of Cα-O bond and this effect is weakened when the H atoms at R2 and R3 are successively substituted with methoxyl groups. The methyl group at R1 has little influence on the BDE of Cβ-O bond, which is however dramatically increased by the hydroxymethyl group at R1.
Abstract: Phosphotungstic acid is an efficient, green and highly acidic heterogeneous catalyst. Different from other solid heteropholy acids, phosphotungstic acid is dissoluble in alcohols. This research makes the best use of the physicochemical properties of phosphotungstic acid combining with high solubility of supercritical alcohols. Sawdust was liquefied in the supercritical solvent using phosphotungstic acid as catalyst. The effects of different solvents on the solvolysis liquefaction and the compositions of bio-oil were investigated. Each solvolysis experiment was conducted at 260℃ for 30min in a stainless-steel autoclave, in which 1g of fir sawdust, 0.5g of phosphotungsic acid, 150g of alcohol (such as methanol, ethanol, n-propanol or iso-propanol) were added. The liquefaction products were separated by filtration after quenching the reaction. Then, the filtrate was extracted with n-hexane and separated into light bio-oil and heavy bio-oil after removing the solvent. Simultaneously, the residue, heavy bio-oil and light bio-oil were characterized by Fourier transform infrared (FT-IR) and Agilent 7890A/5975C gas chromatography-mass spectrometry (GC-MS). The results show that the reaction pressure and polarity of alcoholic solvents significantly impact the liquefaction efficiency and liquefaction products. The liquefaction yield using methanol, ethanol, n-propanol and iso-propanol is 54.75%, 90.29%, 85.90% and 89.15%, respectively, while the relative content of main compound esters in liquefaction products is 43.759%, 23.531%, 41.761% and 28.619%, respectively. Especially, the relative content of methyl levulinate in methanol system is 33.374%. The main compounds in liquefaction products using methanol, ethanol, iso-propanol as solvent are esters and phenols, while n-propanol system are esters, ketones and alcohols. Meanwhile, levulinate erster, which is produced through the reaction of cellulose/hemicellulose and alcohols, is detected in the liquefaction products of all four solvents. Phenols is determined in the liquefaction products in iso-propanol system with relative content of 24.342%. The aldehyde compounds only exist in methanol system. The absence of phenols in n-propanol system indicates that its weakest polarity provides less hydrogen radical and may lead to difficult degradation of lignin.
Abstract: Layered double hydroxide (LDH) precursors with different metal elements were prepared by co-precipitation method at constant pH value; highly dispersed Cu/Al/Zn, Cu/Al/Ni and Cu/Al/Ni/Zn mixed metal oxygen carriers were obtained by calculation of the corresponding precursors. These oxygen carriers were characterized by XRD, XRF, H2-TPR, SEM and nitrogen adsorption and their activity in the chemical looping gasification (CLG) of biomass was investigated in a fixed bed reactor. The results indicated that typical hydrotalcite structure appears in the three precursors with stable layer board. The interlayer spacing of Cu/Al/Zn precursor is 0.2642nm, larger than that of the Cu/Al/Ni precursor. The oxygen carriers derived from the corresponding precursors display similar elements contents as the preparation reagents. Due to the synergy among various metals, the Cu/Al/Ni/Zn oxygen carrier shows the highest reaction activity and anti-sintering ability. The addition of Ni and Zn has a positive effect on the activity of CuO and reduce its reduction temperature; Zn shows a better synergistic effect than Ni with Cu. The carbon conversion reaches 82.03% for the CLG of biomass with Cu/Al/Ni/Zn as oxygen carrier; the surface area of Cu/Al/Ni/Zn remanis 5.995m2/g after the CLG reaction, suggesting that it could be an ideal candidate for the CLG of biomass.
Abstract: C6-asphaltene and deasphalted oil were obtained by using the Ta-he atmosphere residue (THAR) as the feedstock and n-hexane as the solvent. The deasphalted oil was then mixed with C6-asphaltene to prepare the residue with different asphaltene contents for autoclave hydrothermal cracking experiments. The molecular structure parameters, functional groups, crystal structure and surface morphology of C6-asphaltene were systematically analyzed by elemental analysis, 1H -NMR and 13C-NMR, GPC molecular weight, FT-IR, XRD and SEM. The results show that the aromatics in C6-asphaltene exhibit a highly branched degree and the side chains consist of mainly methyl, ethyl and propyl groups; the aromaticity (fA) of C6-asphaltene reaches 0.57. The aromatic ring systems have the peri-and cata-condensed structures, with high condensation degree and large aromatic slice sheets. The influence of C6-asphaltene content on its hydrothermal cracking behavior was further investigated. The result illustrate that the conversion of the residue oil is gradually increased with the increase of the asphaltene content; however, when the asphaltene content exceeds 5.12%, the increment of conversion is at the cost of the rapid coke formation. In addition, the yield of light oil increases at first and then levels off with the increase of the content of aliphatic carbon (fC3) in long chains, whereas the carbon residue and aromaticity (fA) show a good linear relationship with the yield of coke.
Abstract: The Venezuelan vacuum residue was used as a feedstock for thermal upgrading experiments to investigate the changes in chemical structure and composition and the solvation interaction of heavy oil components in a micro-batch reactor at 410℃ with an initial pressure of nitrogen 2.0MPa. The 1H-nuclear magnetic resonance measurement was applied to analyze the reaction pathway of hydrogen atoms with different chemical shift of the heavy oil components. The average molecular structural parameters of asphaltenes and heavy resins in the oil produced by thermal upgrading of the feedstock were calculated and analyzed by the modified Brown-Lander methods. The vapor pressure osmometry was used to determine the average molecular weights of supramolecular structures formed by asphaltenes and heavy resins in toluene. The results show that both H/C atomic ratio and hydrogen donating ability of asphaltenes and heavy resins decrease with reaction time, and the conjugate degree of aromatic ring system and fA become greater clearly after 45min. The aggregation of asphaltenes rises slowly and increases sharply after 15 min, while there is a slight change of aggregation for the heavy resins during the whole reaction time, and the differences in aggregation correlation values between asphaltenes and heavy resins are increased by 1.5% at 15min, 50.8% at 25min, and 142.3% at 45min, respectively. The solvation interaction of heavy resins with asphaltenes weakens with time, and the solvation parameters decrease from 32.9% at the beginning to 29.5% at 15min, 14.1% at 25min, and 9.6% at 45min, respectively. The changes may contribute to the dropping of thermal colloidal stability of resins and the increasing of spot ratings.
Abstract: CuO-ZnO-ZrO2(CZZ) nanocatalysts were successfully prepared by citrate-gel method. The catalysts and their precursors were characterized by X-ray photoelectron spectroscopy (XPS), N2 adsorption specific surface area measurement (BET), X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), H2 and CO2-temperature-programmed desorption (H2 and CO2-TPD) and thermogravimetric analysis (TG-DTA). Drying time of the wet gel and the dosage of citric acid were systematicly studied, while combustion method was also conducted with the comparison of those obtained catalysts. Results show that, prolonged drying process can effectively prevent particle spattering during calcination, benefit the dispersion of different components in the catalyst, and improve the adsorption ability of catalyst for H2 and CO2. Sample CZZ-48h, which was dried at 112℃, 48h, maintained a much higher BET specific surface area than that prepared by combustion method. The CuO-ZnO-ZrO2 catalyst, in which 100% of stoichiometric amount of citric acid was added, exhibited an optimum catalytic behavior with a space-time-yield of methanol 109.4g·h-1·kg-1 under the condition of 240℃, 2.6 MPa, 3600h-1, H2/CO2=3. The detriment of the catalytic performance excessive amounts of citric acid is ascribed to decline dispersion of the catalyst component, and decomposition residual covering on the surface active species of the catalyst.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
