Abstract: In this study, an Fe-Zr oxide (Fe2O3 and ZrO2) modified by K2CO3 was used as the oxygen carrier (denoted as K3-Fe70Zr30) to analyze the effects of the temperature and the char mass ratio on the gas yield and composition during coal char chemical looping gasification for hydrogen production. The results of temperature-programmed experiments show that the reaction of oxygen carrier and coal char starts at 500 ℃, and the reaction rate increases sharply after 750 ℃; the reduced oxygen carrier begins to react with steam when the temperature reaches 400 ℃, and the concentration of hydrogen significantly increases after 500 ℃. The results of isothermal experiments indicate that the reaction rate accelerates with increasing reaction temperature. However, the ratio of CO/CO2 volume ratio increases, resulting in the H2 production decreases as the temperature raises. In addition, an increase in char ratio increases the ratio of CO/CO2 volume ratio in the outlet gas increases, which leads to the hydrogen production firstly increase and reaches a maximum value of 1.734 L/g, and then decrease. The activity of oxygen carrier can keep stable during the first 2 redox cycles, but it decreases in the 3rd cycle. The activity can be renewed by supplement of K2CO3, which suggests that the loss of K2CO3 can contribute to the decreased activity.
Abstract: In-situ char and ex-situ char gasification characteristic was studied by using a newly developed micro fluidized bed reaction analyzer (MFBRA) and the reaction kinetics parameters were obtained. The in-situ char gasification proceeds using the same atmosphere, temperature and reactor in the gasification following the pyrolysis; the ex-situ char 1 gasification is defined as coal pyrolysis in Ar atmosphere and then gasification at hot state in the same reactor; and ex-situ char 2 gasification reaction is defined as coal pyrolysis in Ar atmosphere and then gasification after thermal annealing. By analyzing the three kinds of char, it can be seen that in-situ char has the largest specific surface area, lowest graphitization degree, and strongest sorption ability for CO2. Under the minimized limitations of heat and mass transfer, in-situ char gasification has the highest reaction rate, and lowest reaction energy. The study also proves the reliability of MFBRA for in-situ char gasification reaction.
Abstract: A homemade pressurized pressure-drop measuring device and X-ray diffractometer (XRD) analyzer were used to determine the effects of alkali catalyst addition and different chemical compositions of nine kinds of coal ashes on the ash sintering temperature. The results show that the sintering temperature of WJT coal ash containing higher Fe and Ca compositions declines markedly after adding potassium carbonate catalyst. K minerals react easily with Fe and Ca minerals to produce low-melting-point eutectics, which accelerates the sintering and agglomeration. The sintering temperatures of various coal ashes are closely related to the contents of Si, Al, Fe and Ca in coal ashes. The sintering temperatures increase for the coal ash with higher content of silicon and aluminum, but decrease for the coal ash with higher content of calcium and iron in ash. Adding K catalyst can promote the slagging by forming eutectic matters, especially in the presence of calcium and iron. The three-element phase diagrams of CaO-SiO2-Al2O3, FeO-SiO2-Al2O3 could explain the sintering temperatures variance.
Abstract: Based on the theory of coal structure chemistry, the carbon composition differences between Yongxing lignite and its demineralized sample were comparatively studied with solid state 13C-CP/MAS NMR analysis. The results show that the impact of mixed acid treatment demineralization on the allocation proportion of aromatic carbons and aliphatic carbons is insignificant, but its destructive effects on quaternary carbon, aliphatic carbon bonded to oxygen in cyclic hydrocarbon, aromatic bridgehead carbon and carboxyl carbon are more apparent. While aromatic bridgehead carbon is depleted, the proportion of aromatic methyl does not decrease but slightly increases simultaneously. This indicates that the double/multi-ring structures are destroyed into single-ring ones and the aromatic cluster size shrinks, which is the most critical influence of demineralization by mixed acid treatment on Yongxing lignite structure.
Abstract: The thermal extracts and residues of Shenfu subbituminous coal (SC) obtained from thermal dissolution in 1-methylnaphthalene (1-MN) at different temperatures were characterized by FT-IR, thermo-gravimetric (TG) analysis, GPC and synchronous fluorescence spectrometry. The results show that the thermal extracts contain more amounts of aliphatic compounds than residues. Almost all of the ash is transferred into the residue. TG analysis shows that there exists a significant difference between SC and its residues. With the thermal dissolution temperature increasing from 300 to 360 ℃, the number-average molecular weight of thermal extract increases; however, it decreases at 380 ℃. The condensed aromatic ring number of thermal extract increases with the thermal dissolution temperature rising. When the thermal dissolution of SC was carried out at temperature below initial pyrolysis temperature of SC, the thermal dissolution is dominated by the solvation of 1-MN with coal to break the non-covalent bonds in SC. The light components such as ketone and ester are easy to be released at this temperature. For thermal dissolution carried out above the initial pyrolysis temperature of SC, the pyrolysis of side chains and bridged bonds in SC and condensation reactions of free radicals take place, resulting in an increase of three-fused ring structure in thermal extract.
Abstract: Upgrading and multi-stage separation (UMSS) of rice straw was conducted at different temperatures using 1-methylnaphthalene (1-MN) as solvent. Three main solid products were obtained:low molecular weight extract (soluble), high molecular weight extract (deposit) and extraction residue (residue). The elemental composition, chemical structure and physicochemical characteristic of each component were analyzed in detail. Alkali and alkaline earth metal (AAEM) contents of solid products and rice straw were also measured by ICP-MS. The results showed the yield of soluble increased with temperature, and the carbon-based yield of soluble reached 33.48% at 350 ℃. The carbon content and oxygen content of three solid products (soluble, deposit, and residue) increased and decreased with temperature, respectively. The carbon content of soluble and deposit reached up to 82.36% and 80.59% respectively. Meanwhile the oxygen contents of them were as low as 9.50% and 12.03% respectively. More than 86.99% oxygen of rice straw was removed as H2O and CO2. Soluble was almost free from ash, and the ash content of deposit was also less than 1.50%. The higher heating values (HHV) of three solid products were significantly higher than that of rice straw. The FT-IR results indicated that not only dehydration reaction and decarboxylation reaction occurred, but also including obvious aromatization reaction. The contents of Na, Mg and K of soluble and deposit were extremely low, and they decreased with temperature gradually. In conclusion, the degradative solvent extraction method realized dehydration, deoxygenation and multistage separation of biomass under mild condition, and obtained a variety of products of low ash and oxygen content as well as high carbon content and HHV.
Abstract: The bond dissociation energies (BDE) of C-O and C-C bond in 63 lignin model compounds for six prevalent linkages (β-O-4, α-O-4, 4-O-5, β-1, α-1 and 5-5) were theoretically calculated by using density functional theory methods B3P86 at 6-31G(d,p) level. The effect of various substituents on BDE and the correlation between the bond lengths and the corresponding BDE were analyzed. The calculation results show that C-O bond is generally weaker than C-C bond, and the average bond dissociation energy of Cα-O (182.7 kJ/mol) is the lowest, and that of Cβ-O is second lowest. The substituent group on both the aromatic and alkyl groups can substantially weaken C-O bonds, and C-O bonds do not exhibit such a strong correlation between C-O bond lengths and BDE. Compared with C-O bonds, BDE of C-C bonds are little affected by the substituent on the aromatic groups, but affected obviously by the substituent on alkyl groups. There is a strong linear relationship between C-C bond lengths and BDE. The BDE are weak when the C-C bond lengths are long.
Abstract: To improve the catalytic performance of iron-based catalysts for dehydrogenation of ethylbenzene with CO2, two samples, F4AZ10-imp and F4AZ10-pre, with the same contents of Fe, Al and Zr were prepared by the impregnation method and one-step precipitation method. The catalytic performance of these two samples for the dehydrogenation of ethylbenzene with CO2 was tested at 550 ℃. Both the samples are characterized with XRD, NH3-TPD, CO2-TPD and H2-TPR techniques and N2 sorption experiment. It was shown that the preparation methods had a great effect on the catalytic performance. Compared to the impregnation method, the one-step precipitation method gave a more active catalyst because of a higher dispersion of active Fe2O3 on the catalyst surface and a stronger activation of CO2.
Abstract: Brønsted acidic ionic liquid [BPY]HSO4 was synthesized and characterized by FT-IR and 1H-NMR. [BPY]HSO4 was then used as a catalyst in alkylation desulfurization of FCC gasoline; the effects of the reaction temperature, time and mass ratio of ionic liquid to oil on the desulfurization efficiency and FCC gasoline quality were investigated. The results showed that after reaction for 90 min under 65 ℃ and an ionic liquid to oil mass ratio of 0.09, the sulfur content of FCC gasoline is decreased from 580.0 to 6.4 μg/g, with a desulfurization rate of 98.90%, which can meet the request of Chinese National Standard V for the sulfur content in motor gasoline (< 10 μg/g). A survey on the distribution of sulfur compounds indicated that sulfur compounds are transferred from light fraction (< 170 ℃) to heavy fraction (> 170 ℃) with the help of [BPY]HSO4 and the sulfur compounds in heavy fraction can then be removed further by hydrodesulfurization. PONA results indicated that the alkylation desulfurization catalyzed by [BPY]HSO4 has little effect on hydrocarbon composition and octane number of FCC gasoline. Moreover, the [BPY]HSO4 ionic liquid can be recycled through extraction and reused in the alkylation desulfurization.
Abstract: Mn/Al-SBA-15 absorbent was synthesized by impregnation using Al-SBA-15 prepared by grafting method as support, manganese acetate as precursor of active component. The samples were characterized by means of XRD, N2 adsorption-desorption, NH3-TPD, Py-FTIR and XPS. The adsorbent was used for adsorption desulfurization of simulated gasoline. The optimum molar ratio of Al/Si was determined through combining characterization of samples and their desulfurization performance. The mechanism of adsorption desulfurization was proposed. The regeneration properties were also studied. The results showed that when the molar ratio of Al/Si was 1:45, the performance of adsorbent was the best. The thiophene was adsorbed through acid-base reaction. The introduction of Al improved the stability and the regeneration of the adsorbent.
Abstract: Heteroatomic mesoporous Ce-MCM-41 molecular sieve was synthesized by using hydrothermal synthesis method with cetyltrimethy ammonium bromide (CTMABr) as template, cerium chloride as cerium source and sodium silicate as silica source. X-ray diffraction (XRD) and infrared spectrum (FT-IR) results indicate that the well-ordered meso-porous structure was obtained when the Ce/Si molar ratio is less than 0.04; Ce was incorporated into the framework of MCM-41. Nitrogen physisorption measurements indicate that the average pore diameters of MCM-41 and Ce-MCM-41 are 2.82 and 2.46 nm, with pore volumes of 0.762 1 and 0.689 4 m3/g and BET surface areas of 986.42 and 756.8 m2/g, respectively. Dimethyl sulfide with a molecular size of 0.464 8 nm can easily enter the meso-scale pores of MCM-41 and Ce-MCM-41. NH3-TPD results illustrate that the acidity of Ce-MCM-41 is stronger than that of MCM-41. As a result, for the adsorptive removal of dimethyl sulfide from nitrogen with a dimethyl sulfide content of 58 μg/g, the desulfurization capacity of Ce-MCM-41 is 7.52 mg(S)/g, higher than that of MCM-41 (4.57 mg(S)/g). Furthermore, both MCM-41 and Ce-MCM-41 molecular sieves could be easily regenerated after adsorption of dimethyl sulfide; the desulfurization capacity can be recovered up to 80% of the original capacity after regenerated for three times.
Abstract: HZSM-5 zeolites were respectively treated by Na2CO3,TPAOH and mixed alkali solution of TPA+/CO32-. The samples were characterized by FT-IR XRD, XRF, N2 adsorption/desorption, SEM, NH3-TPD and Py-FTIR techniques. It was found that the microporous and mesoporous hierarchical HZSM-5 (A) catalysts were formed after the treatment and their acidity were modulated. The largest surface area and the most mesoporous were found in the HZSM-5(TPA+/CO32-) treated by the mixed alkali of TPA+/CO32- s. The thiophene alkylation performance of HZSM-5 and HZSM-5(A) zeolites was investigated in a small-scale fixed bed reactor with model compounds as feedstock. The co-sequences displayed that HZSM-5 (TPA+/CO32-) catalysts exhibited the higher conversion of thiophene and selectivity of 1-hexene because the zeolites had proper hierarchical pore diameter and more B-acid sites.
Abstract: The NiO/ZnO-Al2O3 adsorbent was prepared by incipient method and characterized by XRD and mercury porosimeter. The performance of the adsorbent in the removal of COS from the simulated coke-oven gas was tested in a fixed-bed reactor. The results show that the appropriate reaction conditions are 350 ℃, 0.40 MPa and GHSV of 500~1 000 h-1. The adsorbent could remove COS from 320~450 mg/m3 to 0.5 mg/m3 as well as olefins from 2.3%~4.5% to 0 without changing other component. The breadthrough sulfer capacity is 17.18%. The regeneration test shows that the crystal form, pore structure and sulfer capacity of the regenerated adsorbent have no significant change compared with the fresh adsorbent. A desulfurization mechanism is proposed as follows:first COS is absorbed on the reduced Ni atoms to form NiS via the breaking of the S-C bond, then NiS is transformed to H2S in the presence of H2, finally H2S is captured by ZnO.
Abstract: The adsorption of gas-phase As2O3 by metal oxides like CaO, Fe2O3 and Al2O3 was investigated in a fixed bed reactor with an arsenic continuous generation facility. The results indicated that the adsorption of As2O3 on metal oxides is dominated by chemical adsorption at a temperature between 600 and 900 ℃; the adsorption quantity and efficiency are decreased with the increase of temperature. The arsenic adsorption ability of three metal oxide follows the order of Fe2O3 > CaO > Al2O3. The saturation adsorption phenomenon will not occur under the current conditions with the concentration of arsenic in the gas phase in the range between 4.5×10-6 and 13.5×10-6 (volume ratio); the adsorption efficiency for each adsorbent is only affected by the adsorption temperature and the same adsorption efficiency can be achieved with different arsenic concentrations.
Abstract: Ce-based composite oxides (CeM-HT, M=Cu, Mn, Fe, and Co) were prepared by the hard-template method and characterized by XRD, O2-TPD, nitrogen physisorption, and H2-TPR; their catalytic performance in toluene combustion was investigated. The results show that CuO, MnOx, FeOx, and Co3O4 can be well dissolved into the CeO2 lattice, forming Ce-O-Cu, Ce-O-Mn, Ce-O-Fe, and Ce-O-Co solid solutions, respectively. The CeO2 lattice is significantly distorted by the incorporation of Cu and Mn ions, but less affected by the doping of Fe and Co ions. Moreover, a little amount of Co3O4 crystal exists in the CeCo-HT oxide catalyst. The Ce-based composite oxides exhibit excellent catalytic performance in toluene combustion; the toluene conversions over CeFe-HT, CeCo-HT, CeMn-HT, and CeCu-HT oxide catalysts reach 93.7% at 300 ℃, 95.0% at 270 ℃, 96.5% at 260 ℃, and 95.0% at 230 ℃, respectively. The catalytic activity of the Ce-based composite oxides is closely related to their oxygen desorption amount, oxygen storage capacity, and reducibility, following the order of CeCu-HT > CeMn-HT > CeCo-HT > CeFe-HT.
Abstract: Nitrogen emission during chemical looping combustion (CLC) of rice husk based on hematite in a batch fixed bed reactor was studied. Different variables affecting the process, such as reduction temperature and steam content, were tested. The results show that higher reduction temperature results in a higher carbon conversion which reaches the highest value when the steam flow is 1.0 g/min. Furthermore, there are no NO2 detected at all experiments. The rise of reduction temperature from 750 to 900 ℃ could contribute to the rise of NO, whereas the concentration of N2O reaches the highest value at 850 ℃. Both N2O and NO increase remarkably with the increase of steam flow. Nevertheless, the increasing rate of NO is faster than that of N2O. Besides, KAlSi3O8 is detectable in the reduced oxygen carrier, attributing to the reaction of K in biomass with hematite.
Abstract: With MgO as support, powdery Ce-Fe-Zr-O/MgO oxygen carrier was prepared by a ball milling method and monolithic Ce-Fe-Zr-O/MgO oxygen carrier was further obtained by extrusion molding method. The performances of both powdery and monolithic oxygen carriers in partial oxidation of methane to syngas via a chemical looping process were investigated. The results showed that the component of the powdery carrier for oxygen storage is Ce-Fe-Zr-O solid solution, whereas the free oxides of Ce, Zr and Fe may be segregated from the solid solution in monolithic oxygen carrier upon preparation. Two kinds of oxygen species, i.e. surface lattice oxygen and bulk lattice oxygen, can be found on both powdery and monolithic oxygen carriers; bulk lattice oxygen can selectively convert methane to CO and H2, whereas the surface oxygen is very active for methane complete oxidation. Powdery oxygen carrier owns high content of surface lattice oxygen, which results in high concentration of H2O and CO2 in the product. Over the monolithic oxygen carrier, methane can be selectively oxidized to CO and H2 due to the high content of bulk lattice oxygen. Moreover, methane decomposition occurs easily over the powdery oxygen carrier in the redox tests, resulting in a high H2/CO mol ratio (much higher than 2.0) in the product. On the contrary, the monolithic oxygen carrier exhibits a high redox stability and can continuously produce syngas with a H2/CO mol ratio of 2.0 during the successive redox tests.
Abstract: The composite support (PAnC) with conductive polymer polyaniline and activated carbon are prepared. The catalytic performance of the Pd catalyst prepared with PAnC as a support is better than that of the catalyst prepared with activated carbon alone. In addition, the polyaniline carbon support (PAnC-S), which prepared with doping sodium dodecyl sulfate, owns lower charge transfer resistance, more mesoporous between 10~25 nm, larger specific surface area, 94.9 m2/g. PAnC-S and PAnC have uniform particle sizes of about 30 nm. The Pd catalysts prepared with PAnC-S and PAnC support have larger electrochemical surface area, 84.7 and 62.6 m2/g, respectively. Pd/PAnC-S and Pd/PAnC have higher activity and stability for formic acid electrooxidation compared with the Pd/C.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
