Abstract: A series of coal bodies with different foreign moisture was prepared by soaking a long flame coal with low water content. The effects of foreign moisture on the rate of temperature rising and the release of CO and CO2 were studied by simulating coal spontaneous combustion. Moreover, the action mechanism of foreign moisture on the spontaneous combustion of coal was discussed in combination with the characterization of thermal analysis and the pore structure. The action regime of foreign moisture varies with the development of coal spontaneous combustion. At the slow oxidation stage, the foreign moisture plays a physical inhibition effect on coal spontaneous combustion mainly by isolating the contact reaction of coal and oxygen. At the accelerated oxidation stage, the water may involve in the process of the coal-oxygen reaction, promoting the rate of coal self-heating. After entering the rapid oxidation stage, due to the large amount of external water removal during the first and second stages, the pore structure and specific surface area of the coal body are increased; the higher the moisture content of coal, the more active sites will be generated, and the external water presents an indirect promoting effect. When the coal body temperature reaches 180 ℃, with the further increase of coal body temperature, the spontaneous combustion characteristics of coals with different initial external moisture content gradually tend to be consistent.
Abstract: The reaction mechanism for the formation of As2O3 by the homogeneous reaction of O2 with As and AsO in the coal-fired flue gas was investigated by the quantum chemical density functional theory. The structure and energy of each reactant, intermediate, transition state and product were determined and the thermodynamic and kinetic analysis was carried out to explore the reaction mechanism. The results show that the maximum reaction energy barriers for the formation of As2O3 from As and AsO are 32.9 and 157.2 kJ/mol, respectively. The forward and reverse reaction coefficients all increase with an increase of the reaction temperature in the range of 500-1900 K, although the influence extent of temperature varies with different reactions. For the oxidation of As, the equilibrium constants of two reactions are always greater than 105, indicating that the oxidation of As can be carried out completely and regarded as an irreversible reaction. In contrast, for the oxidation of AsO, the equilibrium constants are always less than 105, indicating that the oxidation of AsO is an incomplete reaction. The equilibrium constant of the As2O3(D3H) configuration is extremely low; however, the formation of the As2O3(GAUCHE) configuration is a spontaneous process.
Abstract: The carbothermal interaction between Cu-based oxygen carrier and ash minerals in the chemical-looping gasification of coal and biomass were investigated experimentally by considering three factors of reaction temperature, type of ash and ash content. The chemical-looping gasification was simulated by reciprocally switching the redox atmosphere of the fixed bed and the products were characterized by XRD and SEM-EDS and analyzed by thermodynamic calculation. The results show that Fe2O3 and Al2O3 in the coal ash can easily react with CuO/Cu2O, forming complexes such as CuAl2O4, Cu2Fe2O4 and CuFe2O4, which are difficult to reduce. However, CaO can alleviate the sintering of Cu-based oxygen carriers by hindering the formation of Cu-Al and Cu-Si complexes. The increase of reaction temperature promotes the solid-solid reaction of CuO with silicate minerals such as CaSiO3 and MgSiO3, producing CaCuSi2O6 and CuMgSi2O6 and reducing the reactivity of Cu-based oxygen carriers. With the increase of ash content, Ca2Fe9O13 generated from Ca2+ and Fe3+ can react with SiO2, forming three-phase eutectic CaFeSi2O6 with a high-melting point, which co-fuses with Cu-based oxygen carrier and covers the surface of the oxygen carrier, leading to a decrease in the oxygen release performance.
Abstract: To investigate the influences of ammonium sulfate(AS) on the K/S/Cl transformation and N2O/NO emission, the biomass and semi-coke were co-combusted in a 50 kW circulating fluidized bed under O2/CO2 atmosphere. The experimental results show that AS can reduce the Cl content in deposits obviously and decrease the NO concentration in flue gas significantly. Besides, AS can retain more K in bottom ash and circulating ash, thereby reducing the K content in deposits. In terms of reducing Cl in deposits, the top half of the riser is the optimal position to inject AS.
Abstract: The polypropylene hollow fiber membrane was subjected to dopamine oxidation and silanization two-step surface modification treatment, and then the surface molecular molecularly imprinted polymerization was carried out using methacrylic acid as a functional monomer to prepare a hollow fiber membrane supported-dibenzothiophene molecularly imprinted composite membrane (MIP-PP membrane).The morphology of the imprinted composite membrane was characterized by infrared spectroscopy and scanning electron microscopy, and the desulfurization performance of MIP-PP membrane was measured. The results show that at 298 K, the adsorption of DBT by MIP-PP membrane reaches equilibrium at 180 min, and the maximum adsorption capacity is 133.32 mg/g. The adsorption of DBT by MIP-PP membrane conforms to the Lagergren quasi-first-order kinetic model and the Langmuir adsorption isotherm, which is a spontaneous exothermic process.
Abstract: This study demonstrates the synthesis of MgAl layered double hydroxides (LDHs) intercalated with tungstophosphoric acid (H3PW12O40, HPW) by an ion exchange method, and different interlayer spacings (d003) are obtained by adjusting the ion exchange temperature and time. The crystalline structures, molecular structures, atomic compositions, acidity, and specific surface areas of the LDH samples are rigorously characterized. A relatively high ion exchange temperature is demonstrated to be favorable for the formation of a large d003 value of around 1.46 nm, while a long exchange time is favorable for the formation of a small d003 value of around 1.05 nm. The different values of d003 are the result of different orientations of HPW anions within the interlayer space. Here, d003=1.46 nm is obtained when P2W18O626- and PW11O397- anions are arranged in the interlayer with their C2 axes respectively tilted toward and perpendicular to the LDH layer planes. In contrast, d003=1.05 nm is obtained when PW12O403- anions are grafted onto the LDH layers with their C2 axis perpendicular to the layer planes. Furthermore, the catalytic esterification performance of the samples is investigated for the deacidification of a model crude oil. Compared with PW12O403- anions, the presence of P2W18O626- and PW11O397- anions in the interlayer produce a higher proportion of sites with intermediate acidity that function as catalytic sites. Moreover, a large value of d003 facilitates the diffusion of reactants into the interlayer, which enhances their contact with the catalytic sites, and thereby increases the catalytic esterification performance of the LDHs in the deacidification of crude oil.
Abstract: The effect of carburization and reduction degree on H2O oxidation behaviour for the iron carbides in Fe-based FTS catalyst were firstly investigated using a combination method including X-ray diffraction (XRD), Raman and temperature-programmed-hydrogenation (TPH). The relationship between carbon species transformation and H2O oxidation behaviour of iron carbides was investigated simultaneously. Based on these observations, the influence of typical promoters like K and SiO2 on the structure and H2O oxidation behaviour of Fe-based FTS catalysts was further studied. The results indicated that, for the iron catalyst, the stability of iron carbides against H2O oxidation was increased with the increase of iron carbides content, and the H2O oxidation process led to the formation of more graphitic carbon. The carburization ability was effectively enhanced when certain amount of K promoter was incorporated. Addition of K into Fe-based FTS catalyst increased the number of graphitic carbons, which increased the stability of iron carbides toward H2O oxidation ultimately. It was also found that promotion of SiO2 greatly degraded the carburization degree of the catalyst, while their tendency to be oxidized to form Fe3O4 in the H2O atmosphere was obviously hindered.
Abstract: A series of ZSM-48 zeolites with low Si/Al ratios (Si/Al < 100) were synthesized by hydrothermal synthesis method using hexamethydiammonium bromide as the structure directing agent. ICP-AES results showed that the Si/Al ratio of the synthesized sample was as low as 38.6, indicating the zeolite could be widely used. Pt supported on ZSM-48 with different Si/Al ratios were used for n-paraffin hydroisomerization. The catalytic reaction results showed that Pt/HZSM-48 with Si/Al ratio of 70 exhibited the best catalytic performance. However, the distribution of isomers had not been affected by Si/Al ratio of the ZSM-48, and the central-branched isomers were the main hydroisomerization products.
Abstract: MnαTi1-α catalysts for selective catalytic reduction (SCR) of NO were prepared with impregnation method and their denitration activity and SO2 resistance at medium-low temperature were evaluated. The catalysts were characterized using BET, XRD, XPS, NH3-TPD and H2-TPR. The results showed that the temperature range of the highest denitration activity of MnαTi1-α catalyst shifted to the lower temperature zone along with the increase of MnOx loading. The denitration efficiency of Mn0.1Ti0.9 catalyst reached over 80% at 200-385 ℃. SO2 could bring down denitration activity of MnαTi1-α catalyst greatly and resulted in irreversible deactivation. The specific surface area of the catalyst first increased then slightly decreased with the increase of Mnx loading. Both Mn4+ peak area in H2-TPR and surface chemical adsorbed oxygen increased along with the increase of MnOx loading. All these factors were beneficial to the proceeding of NH3-SCR reaction at low temperature. With the increase of MnOx loading, the acid sites of MnαTi1-α catalyst increased and the reduction peak at low temperature appeared, indicating that MnαTi1-α catalyst had good redox performance at medium and low temperature.
Abstract: Organic-pillared vermiculite supported Ru (Ru/OV) was prepared via adsorption-precipitation method, using RuCl3·xH2O as precursor and applied to catalytic hydrogenation of methyl levulinate (ML). The physicochemical properties of the catalysts were investigated by XRD, N2-adsorption-desorption, TEM and XPS. Effects of reaction temperature, pressure, reaction time on the catalytic performance were studied by orthogonal and single factor experiments. Under the optimum conditions, the conversion of ML and the selectivity of γ-valerolactone (GVL) were 84% and 100%, separately. After being recycled for 20 times, the conversion of ML was above 80% and the 100% selectivity of GVL could be obtained.
Abstract: Ni-Al alloy powder was impregnated with copper nitrate solution, and calcined at different temperatures to obtain Cu-modified Ni-Al alloy powder. The modified alloy powder was leached with a 10% (mass ratio) NaOH solution to obtain the Cu/Raney-Ni catalyst. Elemental composition, crystal structure, pore structure, surface morphology and surface acidity of the Ni-Al alloy powder and corresponding Raney-Ni catalysts were characterized by EDX, XRD, N2 adsorption-desorption, TEM and NH3-TPD. The hydrogenation performance of the Raney-Ni catalysts were evaluated using the reaction of 1, 4-butenediol (BED) hydrogenation to 1, 4-butanediol (BDO) as the probe reaction. The characteristic results showed that the CRT500 catalyst prepared at the calcination temperature of 500 ℃ presented larger specific surface area of 64.96 m2/g, and the proportion of weak acid sites was high of 81.2%. The reaction results proposed that the reactant of BED could be completely converted, and the selectivity and yield of BDO increased firstly and then decreased as the calcination temperature increased. The CRT500 catalyst presented good hydrogenation performance, with BED conversion of 100.00%, BDO selectivity of 61.88%, while the BDO selectivity of the RCT550 and RCT600 were lower, which might be due to the agglomeration or sintering of the catalyst at higher calcination temperature. The CRT500 catalyst showed excellent hydrogenation performance, which might be attributed to the appropriate molar ratio of Ni/Al (3.84), the large proportion of weak acid sites and good dispersion of active component Ni.
Abstract: The dynamic adsorption and desorption behaviors of volatile organic compounds (VOCs, including n-hexane, toluene and ethyl acetate) on various adsorbents (including activated carbon and 5A, NaY, 13X, ZSM-5 (SiO2/Al2O3=27 and 300), Hβ and MCM-41 zeolites) were investigated by gas chromatography and thermogravimetic (TG) analysis; the effect of type, volumetric space velocity (SV) and concentration of VOC on the adsorption capacities was considered. The results show that more VOCs can be adsorbed at higher SV and concentration of VOCs to a certain extent. Activated carbon exhibits the largest adsorption capacity per unit mass towards the VOCs considered in this work, whereas the 13X and NaY zeolites display larger adsorption capacity per unit volume than other adsorbents.
Abstract: A series of CeY zeolites with different cerium loadings and calcined at different temperatures were prepared and used as the adsorbent for the desulfurization of thiophene containing model oil. The CeY zeolites were characterized by XRD, N2 sorption, FT-IR spectroscopy and GC-SCD and GC-MSD techniques. The effects of aromatics and olefins on the adsorption desulfurization performance were investigated and the active species and reaction mechanism for the adsorption desulfurization on CeY zeolites were probed. The results indicate that the CeY zeolite calcined at 150 ℃ is provided with a large number of Brönsted acid sites and hydroxylated cerium species in the supercages, which can synergistically promote the thiophene oligomerization and then enhance the sulfur breakthrough adsorption capacity (18.45 mg (S)/g). However, a further increase in the calcination temperature and cerium loading may greatly reduce the number of active sites for the adsorption desulfurization and suppress the thiophene oligomerization reaction, leading to a significant decrease in the sulfur breakthrough adsorption capacity (4.03 mg (S)/g). For the thiophene model oils containing low concentration of 1-hexene (< 1.0%) or benzene (< 0.1%), the CeY-12.3-150 zeolite (with a cerium loading of 12.3% and calcined at 150 ℃) also exhibits a relatively high sulfur breakthrough adsorption capacity. However, a further increase in the content of 1-hexene or benzene in the feed may lead to a sharp decrease in the sulfur breakthrough adsorption capacity, due to the alkylation of thiophene and the adsorption mode of "S-H" bonding.
Abstract: In situ XRD reaction device combined with the online gas chromatography was used to study the oxidation behavior of the effect of H2O content (4.36%, 1.68%, 0.56%) on the phase and Fischer-Tropsch synthesis (FTS) performance of the single phase Fe5C2. The results show that the oxidation rate of the Fe5C2 phase increases with the increase of the content of injected H2O. Meanwhile, the particle size of Fe5C2 phase decreases and more active sites exposes during the H2O oxidation, resulting in the increase of the FTS activity. Furthermore, the FTS activity increases with the increase of the oxidation times, but the selectivity of CH4 increases and the C5+ selectivity decreases gradually.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
