Abstract: Dehydration and upgrading are essential pretreatment methods for efficient utilization of low-rank coal. In previous works the authors employed degradative solvent extraction method to dehydrate and upgrade low-rank coals and fractionate them into several fractions. For further study of this method, two low-rank coals (MM and LY) were pretreated by acid washing for demineralization or acid washing and Na/Co ion-exchange. The pretreated and raw coals were then extracted by 1-methylnaphthalene (1-MN) at 350 ℃ and fractionated into upgraded coal (UC), high molecular weight extract (Deposit), low molecular weight extract (soluble), as well as a little H2O and gas products. The results show that both acid washing and ion-exchange enhance the yields and carbon contents of the two extracts. Ion-exchange obviously promotes the removal of oxygen-containing functional group during extraction. The yield of high molecular weight extract of demineralized MM increases from 3.5% to 9.5%, and the carbon content and oxygen content of low molecular weight extract of Na ion-exchanged LY are as high as 85.3% and less than 6.4%, respectively. Ion-exchange has a distinct influence on physical and chemical properties of the extracts. The influence of Na ion-exchange is especially remarkable. Thus, demineralization and ion-exchange have evident promotion for the degradative solvent extraction of low-rank coal.
Abstract: The steam gasification experiments with Neimeng lignite, Shenfu bituminous coal, Zunyi anthracite and a petroleum coke were conducted in a thermogravimetric analyzer (TGA) to study the intrinsic kinetics and the macrokinetics with the effects of particle size. By virtue of gas-solid catalysis theory, a method to calculate the internal effective factor was proposed based on the kinetic parameters derived from the nth-order equation. The comparison between calculated and experimental effective factors shows that the method is better to calculate the internal effective factor for quantificationally estimating the effect of internal diffusion on steam gasifiation.
Abstract: The influence of metal ions on the release characteristics of nitrogenous pollutants from pyrolysis of 3 typical coals with different ranks were studied by demineralization and adding metal salts of Fe, Ca and Na. The interactions of coal type and temperature during coal pyrolysis were explored. The results show that yields of HCN and NH3 from the demineralized coals are lower than that from the raw coals. The yield of HCN increases gradually with the increase of temperature, while the yield of NH3 increases first and then decreases, with a maximum value at 800 ℃. Catalytic effects of metal ions on nitrogenous pollutants release from different ranks of coals are different. Fe and Na restrain HCN release from medium rank coals, but promote that from low rank coals, while Ca facilitates the HCN release from all coals to some extent. Three metal ions all inhibit the release of NH3 from medium rank coals, but promote that for low rank coals. Catalysis of each metal ion on yield of HCN and NH3 has its own range of effectiveness. Release of nitrogenous pollutants during coal pyrolysis is influenced by the interactions of many kinds of inherent metal ions in coals.
Abstract: The aim of this research is to design and operate a 10 kW hot chemical-looping gasification (CLG) unit using Fe2O3/Al2O3 as an oxygen carrier and saw dust as a fuel. The effect of the operation temperature on gas composition in the air reactor and the fuel reactor, and the carbon conversion of biomass to CO2 and CO in the fuel reactor have been experimentally studied. A total 60 h run has been obtained with the same batch of oxygen carrier of iron oxide supported with alumina. The results show that CO and H2 concentrations are increased with increasing temperature in the fuel reactor. It is also found that with increasing fuel reactor temperature, both the amount of residual char in the fuel reactor and CO2 concentration of the exit gas from the air reactor are degreased. Carbon conversion rate and gasification efficiency are increased by increasing temperature and H2 production at 870 ℃ reaches the highest rate. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET-surface area tests have been used to characterize fresh and reacted oxygen carrier particles. The results display that the oxygen carrier activity is not declined and the specific surface area of the oxygen carrier particles is not decreased significantly.
Abstract: Mn-doped Fe2O3 oxygen carriers with different molar ratios of Fe to Mn were prepared by co-precipitation method, which were characterized by XRD, BET and TEM. Chemical looping combustion tests between Mn-Fe2O3 and CO at different temperatures were performed to investigate the reaction characteristics, and to determine the optimized Mn doping amount and reaction temperature. The results reveal that a rational Mn doping could enhance the reactivity of iron-base oxygen carrier, and the optimal Fe/Mn molar ratio is 50. Multi-cycle experiments confirm the high stability of the optimized oxygen carrier. Furthermore, the reaction kinetic analysis at heating rates of 30, 40, 50 ℃/min shows that the Avrami-Erofeev model is suitable for the reactions, and the activation energy and pre-exponential factor can be calculated according to the kinetic model.
Abstract: The hydrogenation experiment on the heavy fraction (>350 ℃) of medium/low temperature coal tar, prepared by vacuum distilling, was conducted in an autoclave, and the asphaltene was separated from heavy fraction with n-heptane solvent. The properties such as structure parameters, functional group and microstructure were analyzed by 1H-NMR, XRD, FT-IR, SEM, ultimate analysis and average molecular weight determination (VPO). Moreover, the relevance of coking to C7-asphaltene properties was discussed. The results show that C7-asphaltene units are mainly composed of polycyclic aromatics linked in side with a few and short aliphatic chains (mainly n-alkane less than 3 C atoms). The asphaltene units have small average molecular weights and there is no aromatic sheet stacking structure existing. The propensity to aggregate for asphaltene units was weakened because O atoms in asphaltene are mainly distributed in epoxyalkane or ethers (C-O-C) and they are different from the petroleum asphaltene whose O atoms exist in the peripheral phenolic and alcoholic hydroxyl. So, the intermolecular hydrogen bond is more difficult to build. Furthermore, short chains are not easy to break and fewer polycyclic aromatic radicals are generated in the hydrocracking process, and the asphaltene has a lower coking potential.
Abstract: The catalysis and in-situ regeneration of 1.0%NiO/0.1%MgO-Al2O3 catalyst were investigated in an atmospheric fixed bed reactor, in which the dust was also introduced in the feed to simulate the real dust environment of coal and biomass pyrolysis. The results show that the catalyst has a higher activity but a shorter life as the reaction temperature increases. Cycle regeneration of the catalyst exhibits a good durability, while a significant hydrothermal deactivation phenomenon happens at the regeneration temperature of 800 ℃. As a result, the preferable regeneration temperature range of 600~700 ℃ and regeneration time of 20 min are determined. The increased ratio of air/steam will gradually change the specific surface area and pore structure of the catalyst. EPMA and XRD results show that the introduction of dust does not change the composition of catalyst except the introduction of MgO that will be converted to a new phase of (Mg0.4Al0.6)Al1.8O4. MgO plays a positive anti-carbon deposition role, while SiO2 is reverse. The negative effect of SiO2 on the activity of catalyst can be reduced by a lower operating gas velocity.
Abstract: Unsupported metal nickel catalysts were prepared by liquid phase reduction method. The catalytic performance of the catalysts for syngas methanation were conducted in an autoclave using decalin as the hydrogen donor solvent at different operation conditions, such as temperature, mol ratio of H2/CO in feed gas. And the catalyst characterizations were conducted by means of XRD, SEM, H2-TPR.The results showed that the content of CH4 in the product gas was 89.39% when 2% catalyst was used at 330 ℃, and the corresponding conversions of CO and H2 were 94.56% and 92.60%, respectively. When 4% catalyst was used, the CO conversion was further improved to more than 99% while the content of CH4 in the product gas exceeded 94.26%. The best operation temperature of syngas methanation in liquid phase was 330 ℃and the optimum range of H2/CO mol ratio in feed was 2.20~2.67.
Abstract: The supported Ni-based catalysts were prepared by impregnation method. Effects of different supports (SiO2, ZrO2, CeO2, Al2O3 and Al2O3-CeO2) and water vapour on catalyst microstructure and their performance in biomass pyrolysis gas methanation were investigated. The results indicated that CO conversion increased gradually, and the CH4 selectivity increased firstly, and then decreased with the increase of adding water vapor amount. Compared to SiO2, ZrO2 and CeO2, Al2O3 presented higher BET surface area and Ni metal dispersion, which promoted the activity and selectivity for biomass pyrolysis gas methanation. Furthermore, the Al2O3-CeO2 modified Ni-based catalyst showed more nickel metal loading and active metal dispersion comparing to the Ni-Al2O3 catalyst, exhibiting more excellent methanation performances at lower temperature. CO conversion reached 97%, and CH4 growth rate reached 110% over the Ni-Al2O3-CeO2 catalyst at 300 ℃.
Abstract: Three Ni/SiO2 catalysts with different Ni crystallite sizes were prepared by the incipient wetness impregnation-drying-reduction and incipient wetness impregnation-drying-calcination-reduction methods. The catalysts were characterized by H2-TPR, XRD, TEM, H2 chemisorption, NH3-TPD and TGA techniques. Their catalytic performances in the deoxygenation of methyl laurate to undecane (C11) and dodecane (C12) were evaluated in a fixed bed reactor. The effects of Ni crystallite size on the catalyst structure and performance were investigated. It was found that the impregnation-drying-reduction method gave smaller Ni crystallite size, and the high reduction temperature promoted the growth of Ni crystallite. With the increase of the Ni crystallite size, the turnover frequency of methyl laurate increased, while the total selectivity to C11 and C12 (sC11+C12), C11/C12 mol ratio and the selectivity to cracking products decreased. We suggest that the deoxygenation of methyl laurate on Ni/SiO2 is structurally sensitive. The effects of weight hourly space velocity (WHSV) on performance of Ni/SiO2 were also investigated. As WHSV increased, the methyl laruate conversion, sC11+C12, C11/C12 mol ratio and the selectivity to cracking products decreased. In addition, CO and CO2 generated from the decarbonylation/decarboxylation pathway were converted to CH4, indicating that Ni/SiO2 had high activity for methanation. It was also found that the sintering of small Ni crystallites, the adsorption of organic compounds and carbon deposit led to catalyst deactivation.
Abstract: The preparation of biodiesel from inedible low-cost acid oil with a high average acid value(AV) of about 33.07 mgKOH/g via pre-esterification and transesterification processes in a self-designed continuous biodiesel production apparatus assisted by multi-frequency ultrasonic at high efficiency and low energy consumption was investigated. The influences of operating variables including flow rate of material(residence time), ultrasonic power and frequency or combinations, the amount of catalyst, the molar ratio of methanol to oil at ambient temperature and the specific energy consumption on the transesterification reaction were discussed. The results show that multi-frequency ultrasonic irradiation is superior to single-frequency in enhancing biodiesel production process; the yield of fatty acid methyl esters(FAME) about 96.83% is attained with 15-25-35-40 kHz of frequency combination, 200 W of powers, 25 L/h of flow rates of the processed oil (residence time 54 min), 6:1 mol ratio of methanol to oil,and 1.2% KOH (% of acid oil). 50 L waste acid oil can be converted into 48 L biodiesel that meet the standards GB19147-2009, and the overall electric power and time consumptions are about 5.42 kWh and 8.667 h, respectively.
Abstract: The HPA/Bi2WO6 was prepared with Na2WO4·2H2O, Bi(NO3)3·5H2O and different surfactant templates. The prepared sample was dried by the supercritical fluid drying (SCFD) method. It was characterized with XRD, FT-IR and SEM techniques and N2 sorption experiment. Its photocatalytic properties were evaluated with denitrification of nitrogen-containing simulated oil as model reaction. It was shown that the sodium dodecyl sulfate (SDS) should be chosen as template. With this template, a highly dispersed, crystalline and active photocatalyst was obtained. This catalyst had a larger specific surface area. The SCFD method effectively decreased pore collapse and particles agglomeration degree, consequently increasing the specific surface area and improving the catalytic performance. Immobilization of H3PW12O40 on Bi2WO6 increased the surface acid sites, and hence the photocatalytic activity. When the H3PW12O40 loading was 10%, about 92.08% of nitrogen in simulated oil were removed by shining for 3 h with a xenon lamp at the mcatalysts/msimulated oil ratio of 1:100.
Abstract: Synthesis of polyoxymethylene dimethyl ethers was carried out on HMCM-22, Al-YNU-1 and MOR zeolites by the condensation of trioxane and methanol or methylal. The crystal structures and surface acidity of the catalysts were characterized by XRD, SEM and NH3-TPD. It was found that DMM2~8 selectivity was influenced by the acid strength and density of zeolites and reaction conditions. HMCM-22 showed much higher selectivity to DMM2~8 than Al-YNU-1 and MOR. Under the optimal conditions, the DMM2~8 selectivity reached 65.1% and 90.6% in ME/TRIox and DMM/TRIox systems respectively. It was shown that the moderately strong acid sites were probably responsible for the formation of long chain DMMn, while the strong acid sites werefor DMM.
Abstract: The catalytic performance of various zeolites modified with tungsten oxide in the conversion of dimethyl ether (DME) to toluene in the presence of oxygen was investigated in a continuous flow fixed-bed reactor. The results indicated that WO3/HZSM-5 as a catalyst is highly selective in the conversion of DME to toluene; under the optimized conditions, i.e. atmospheric pressure, 290 ℃, and with a DME/O2 mol ratio of 2:1, the conversion of DME is 98.97%, with the selectivity of 39.71% to toluene. The characterization results about the catalyst structure and acidity illustrate that the porous structure of ZSM-5 is suitable for the formation of toluene from DME. The doping of WO3 adjusts the distribution of the surface acid sites and then inhibits the formation of side-products in the presence of oxygen, which is able to enhance the selectivity to toluene.
Abstract: The adsorption behaviors of linear C2~6 olefins and butene isomers on the H-ZSM-5 zeolite of periodic model were studied by the PBE-D method. The adsorption energies (EPBE-D) and the dispersive correction energies (ED) of C2~6 linear olefins on the zeolite exhibit a linear increase with the number of carbons by -12 kJ/mol and -13 kJ/mol, respectively. The adsorption energies without dispersive correction (E*) is not changed obviously, but it is decreased in the cases of increased space resistance for pentene and hexane. The value of ED is much larger than that of E*, implying that van der Waals' force plays a key role in the adsorption of olefins on the zeolite and its influence on the adsorption is dependent on the carbon number. The adsorption energies of butene isomers decrease in the order of trans-2-butane > cis-2-butene > n-butene > isobutene. Three kinds of n-butene isomers are similar in their ED value, which are larger than that of n-butene. The difference in adsorption energy among the three isomers is caused by E*. The differential charge density analysis shows that the electrons between the alkene double bond and the acidic center are gathered, in consistent with the strength of π-coordination; H atom in the acid site turns to be protonated, with electrons transferred to the nearby O and other atoms.
Abstract: The Cu-containing ionic liquids (IL), like [BMIm]Cl-1.8AlCl3-0.5CuCl and [Et3NH]Cl-1.8AlCl3/ CuAlCl4, were synthesized and characterized. The selectivity of isobutene/butene alkylation of Cu-containing IL was also investigated. The results showed that the selectivity had little relation to the acidity of Cu-containing IL. The research octane number (RON) of [Et3NH]Cl-1.8AlCl3/CuAlCl4 alkylate could be higher than 100, which was better than those obtained by sulfuric acid, common chloroaluminate IL, and composite IL under the identical reaction conditions. The complexation of CuAlCl4 with 2-butene in alkylation process should be accounted for the super selectivity of trimethylpentane (TMP) of isobutane alkylation catalyzed by Cu-containing IL.
Abstract: In order to inhibit the metal catalytic coking, the TiN and TiC coatings were made on the inner surface of stainless steel 304 tubes by chemical vapor deposition (CVD) method. The coatings were characterized by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), metalloscopy and thermal shock. The results show that the thickness of TiN and TiC coatings is about 7.24 μm and 11.52 μm, respectively. And the two kinds of coatings are uniform and dense, which have a good adhesive strength. To evaluate the anti-coking effect of TiN and TiC coatings, the supercritical cracking of hydrocarbon fuel (A) was employed in the temperature programmed mode and the experiment was terminated when the pressure drop of reaction tube is more than 1 MPa. The results show that the experiment with the 304 blank tube is terminated in 180 s at the reaction temperature of 650 ℃, while the experiments with the TiN and TiC coated tubes are terminated in 275 s and 1 560 s only at 780 ℃, respectively. At the same time, the anti-coking effect of the coatings is evaluated by analyzing the pressure drop, gas composition and morphology of coke. It is indicated that the two kinds of coatings could inhibit coking effectively, and TiN is better than TiC.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
