Abstract: Composition and structure characteristics of fine slag (FS) and coarse slag (CS) discharged from Texaco gasifier with Zhundong coal as raw material were analyzed, and their thermochemical conversion properties were analyzed. Proximate and ultimate analyses show that the contents of fixed carbon in coarse slag are 42.31%, indicating that it can be used as raw material to realize its high-added utilization. Analysis with Fourier transform infare spectrometer (FT-IR) suggest that the absorption peak of Si−O in coarse slag and fine slag is stronger, and there is a small amount of aromatic structure in fine slag. Thermal decomposition behaviors in inert atmosphere show that the maximum weight loss rate peak of coarse slag is located around 600 ℃, while that of fine slag is transferred to about 620 ℃. Results of thermal decomposition in oxidization atmosphere show that there are obvious weight loss rate peaks derived from combustion of the fixed carbon in 500−700 ℃. The weight loss profiles of fine slag and coarse slag in inert and oxidization atmosphere were fitted by Coats-Redfern method. The kinetic parameters including pyrolysis/combustion activation energy and correlation coefficient were calculated. The results show that the fitting effect is better as the reaction order selected as 3 at the intense pyrolysis section (560−640 ℃) for coarse slag in inert atmosphere, with correlation coefficient R2 of 0.99 and activation energy E of 38.85 kJ/mol. Similarly, in the intense pyrolysis stage (590−650 ℃) of fine slag, the fitting effect is better as the reaction order selected 3, with the correlation coefficient R2 of 0.97 and the activation energy E of 79.09 kJ/mol. In oxidization atmosphere, at the intense combustion stage of coarse slag (540−605 ℃) and fine slag (530−605 ℃), the fitting effect is better as n=1 for the both slags, with the activation energy E of 226.46 and 154.73 kJ/mol respectively.
Abstract: Two raw coals and their washery products were collected from two coal-washing plants of Ningwu coal field, Shanxi, China. The migration behaviors of sulfur (S) and arsenic (As) during coal washing process were investigated by the microwave digestion method together with hydride generation-atomic fluorescence spectrometry. Based on the checked mass balance of As, a sequential-chemical-extraction method was used to explore the dependence between speciation transformation and release characteristics of S and As during the combustion process of raw coal, cleaned coal, coal gangue, middling coal, or coal slime. The results show that 20%–28% of S and As in raw coal are migrated to the cleaned coal, and 46%–61% of them to gangue. Pearson correlation coefficient identifies that the inorganic minerals in samples control the migration behavior of S and As. Compared with the elements in raw coal, the proportions of organic S and As in cleaned coal increase to 30%–50%, while the inorganic S and As in coal gangue account for more than 90%, which indicates the dependence between the species of S and As in raw coal and its washery products. The relatively large amount of organic S and As in the cleaned coal obviously release together with water and volatile matters below 500 ℃. While the inorganic bonded As and S in gangue mainly release during the decomposition process of pyrite, sulfate and other inorganic minerals between 500 and 1000 ℃, which shows the consistency of S and As release characteristics during combustion of raw coal or washery product. The release rates of S and As from the cleaned coal are the fastest among all samples and the corresponding maximum release ratios are 80%–95% at 300 s and 60%–75% at 200 s, respectively, whilst their release rates from gangue are the slowest and As reaches the maximum release ratio of 40%–45% at 300 s but S doesn’t get to the maximum release ratio even at 600 s. The release rates of S and As from the middling coal or raw coal are between the cleaned coal and gangue. The different release rates of S and As during the sample combustion are mainly depended on their speciation distributions in nature.
Abstract: In order to analyze the distribution and occurrence of lithium (Li) and gallium (Ga) in coal separately, the No.11 coal seam from the Antaibao mining district was collected as research object. The distribution of Li and Ga in different ash fractions, sulfur fractions, and coal column benches was discussed. The relationship between Li and Ga with other major elements in the micro-area was investigated by time-of-flight secondary ion mass spectrometer (TOF-SIMS) and scanning electron microscope with energy dispersive spectrometer (SEM-EDS). The difference in the occurrence of Li and Ga, and the influencing factors were discussed. The results show that Li is enriched in high-ash coal, while Ga does not change significantly in coal samples in various ash and sulfur fractions. In the longitudinal seam, Li is enriched in the coal bench with sufficient supply of terrestrial source material, while Ga is more evenly distributed in the coal seam. In the in-situ regions, Li occurs only in aluminosilicates, while Ga can occur in kaolinite, boehmite, pyrite, chloride, and sylvite. The correlation coefficient between Li and stable element zirconium (Zr) for all samples is 0.894. Both are mainly derived from acidic magmatic rocks in the source area. Gallium is abundant in both high ash coal and high sulfur coal due to its transitional property as a lithophile and sulphophile element. Its mobility makes it tend to be uniformly distributed in the coal seam.
Abstract: Pyrolysis behavior and kinetics of three typical agroforestry biomasses including apricot shell, wheat straw and poplar sawdust were investigated by thermogravimetric mass spectrometry (TG-MS). The results show that the differences of the main components make the three biomasses exhibit different characteristics in the main reaction range (200–450 ℃). It is found that the average activation energy of apricot shell, straw and sawdust is 188.22, 220.77, and 175.87 kJ/mol, respectively based on the typical isoconversional methods. The average activation energy of each component in biomass was calculated by the distributed activation energy model (DAEM) method, indicating that there is a fourth component with high average activation energy in biomass (297.44 kJ/mol for apricot shell, 284.35 kJ/mol for straw and 309.96 kJ/mol for sawdust). The activation energy of hemicellulose and cellulose shows an increasing order of straw < apricot shell < sawdust. The two kinds of kinetics methods are complementary to each other. The overall calculation results by the isoconversional method are close to those by the single-component distributed activation energy model method, but the isoconversional method is simpler; while the distributed activation energy model method can be used to obtain the kinetic parameters of different components of raw materials, which makes up for the deficiency of the isoconversional method. A combined use of the two methods can form a more comprehensive understanding of the pyrolysis reaction.
Abstract: Carboxylic ionic liquid 1-propionic acid-3-methylimidazolium chloride (CFIL) was immobilized in a metal-organic framework (MOF) material NH2-MIL-101 in one-pot by the in-situ assembly method; as a heterogeneous catalyst with multiple active sites, the catalytic performance of NH2-FMOF-CFIL in the cycloaddition of CO2 with epichlorohydrin (ECH) to synthesize chloropropylene carbonate (CPC) was investigated. The immobilized of CFIL in NH2-MIL-101 was proved by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis, while the powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and N2 adsorption-desorption measurements demonstrated that CFIL neither damages the crystal structure nor blocks the pore of NH2-MIL-101, but induce the formation of mesopores. The catalytic reaction results reveal that there is a catalytic synergy between imidazole N and Cl− on CFIL and Cr3+ and amino group on MOF, which endow the NH2-FMOF-CFIL composite excellent catalytic performance in the cycloaddition of CO2 with ECH; under mild conditions, viz., 0.1 MPa CO2, 25–70 ℃ and without using any solvent and cocatalyst, the CPC yield reaches 99% after reaction for 24 h. Moreover, the crystal structure and high activity of the NH2-FMOF-CFIL catalyst are well preserved even after reuse for 5 cycles.
Abstract: Using cerium nitrate as the source material and urea as the precipitant, nanometer CeO2 carrier was prepared by hydrothermal method, and the microstructure of CeO2 carrier was controlled by changing the hydrothermal reaction temperature. Then the CuO/CeO2 catalytic material was prepared by loading CuO on the CeO2 carrier and evaluated in methanol steam reforming for hydrogen production. Based on the characterization data of low temperature nitrogen adsorption, XRD, H2-TPR and XPS, the effects of hydrothermal reaction temperature on the microstructure of CeO2, the structure of CuO/CeO2 catalytic material and the performance of methanol steam reforming were investigated. The results show that the nanometer CeO2 support prepared at 180 ℃ has a cubic fluorite structure. After loading CuO onto the CeO2, the obtained CuO/CeO2 catalyst exhibits better catalytic activity due to its stronger Cu-Ce interaction, lower reduction temperature of Cu species in the surface, and more oxygen vacancies on the surface of the catalyst. When the reaction temperature is 280 ℃, the molar ratio of water to alcohol (W/M) is 1.2, and the space velocity of methanol vapor gas (GHSV) is 800 h− 1, the methanol conversion rate can reach 91.0%, the mole fraction of CO in reforming gas is 1.29%.
Abstract: The dehydrogenation of propane was carried out with propane containing different proportions of propylene, and the carbon deposition behavior of Pt-based catalyst under propene-rich condition was investigated. The results show that the presence of propylene in the raw material accelerates the rate of carbon deposition, shortening the time of dynamic equilibrium of carbon deposition on the support, and promoting the formation of carbon on the surface area of the active phase and the graphitization of carbon deposition. At the same time, the rich propylene in the raw material increases the amount of unsaturated aliphatic compounds, thus promoting the generation of aromatic carbon and graphitized carbon, but the catalyst structure is not destroyed. In the process of propane dehydrogenation, when the propylene content increases to 1.5%, the carbon “peak I” appears on the surface of the active phase, and the "peak II" moves to the high temperature region. When the alkene content increases by 3.0%, peak I and peak II merge together, and the area of the entire peak increases significantly. When the carbon deposition exceeds 10.26%, the degree of carbon deposition and graphitization of the catalyst becomes higher and higher. The increase of the propylene content accelerates the saturation process of the carbon holding capacity of the carrier. Under the same reaction time, the amount of carbon deposit increases.
Abstract: The effects of extra-aluminum species (Al(OH)2+and Al3+) on the properties of Brønsted acid sites (BAS) were studied using thiophene as the model probe and HFAU as model zeolite by using a periodic DFT study. It is found that the Lewis acid strength of Al3+ species is higher than that of Al(OH)2+ species, and the hydroxyl species Al(OH)2+ in both directions have similar charge properties, that is, similar acid strength. The results of electronic properties combined with deprotonation energies (DPE) show that the BAS in 1-HFAU/Al(OH)2+, 2-HFAU/Al(OH)2+and HFAU/Al3+ zeolites have similar acid strength (1045 ± 11 kJ/mol). It can be concluded that the difference of hydroxyl direction and Lewis acid strength of Al(OH)2+and Al3+ species hardly affect the acid strength of BAS. By simulating the adsorption of thiophene, the adsorption energies and the changes of electronic properties and geometric structure during the adsorption process were obtained. The results show that thiophene in HFAU/Al3+ zeolite is easy to be adsorbed on Al3+ site, which is due to the strong Lewis acid strength of Al3+ adsorption site. The thiophene in HFAU/Al(OH)2+ zeolite is preferentially adsorbed on the BAS rather than the Al(OH)2+ adsorption site. In addition, Al(OH)2+ species can exert a weak interaction (dispersion interaction) on thiophene adsorbed on BAS to promote the adsorption of thiophene. The adsorption modes depend on the structure of Al(OH)2+ species and the direction of hydroxyl groups. This work explored the intrinsic properties of host-HFAU zeolite (containing extra-framework aluminum species) and guest-thiophene molecule from an electronic-level, and revealed the synergistic mechanism between acid sites.
Abstract: In consideration of the inferior performance of ZIF-67 derived Co3O4 catalyst in the low-temperature formaldehyde oxidation, manganese was utilized to modify Co3O4 catalyst. The results showed that the Mn-Co3O4 catalyst exhibited the superior HCHO oxidation activity and achieved 90% HCHO conversion at a WHSV of 60000 mL/(gcat·h) and inlet HCHO concentration of 98.16 mg/m3 at 118 ℃. XRD, Raman and BET results demonstrated that the Mn-Co3O4 catalyst possessed lower crystallinity, more defects and specific surface area, which was conducive to the adsorption of reactants and exposure of more active sites. XPS, H2-TPR and O2-TPD results indicated that the strong interaction between Mn and Co species prominently improved the low temperature reducibility and O2 activation performance of Mn-Co3O4 catalyst, which endowed it with more abundant Co3+ and surface-adsorbed oxygen species. Therefore, the Mn-Co3O4 catalyst exhibited superior HCHO oxidation performance. Based on in-situ DRIFTS results, dioxymethylene and formate species were recognized as the main reaction intermediates of HCHO oxidation over the Mn-Co3O4 catalyst.
Abstract: A series of LaCoO3/MO2 catalysts were prepared by support different carriers (M = Zr, Ti, Ce) through the citric acid sol-gel method, and the catalytic oxidation performance of toluene and NO and critical mechanism were investigated. The results found that the LaCoO3/CeO2 catalyst with CeO2 as the carrier exhibited the best catalytic oxidation performance, the conversion rate of NO reached 68% at 300 ℃ and t90 of toluene was 245 ℃. The physical and chemical properties and microstructure of the supported perovskite catalysts were characterized by BET, XRD, H2-TPR, XPS technologies. The results showed that the supported perovskite had a larger specific surface area. Meanwhile, the supported perovskite catalyst had more active lattice oxygen and better redox performance. Moreover, the interaction between Co and Ce ions existed in the contact interface of LaCoO3 and the carrier CeO2, which was conducive to the formation of oxygen vacancies, thus providing more active sites for the reaction. The reaction mechanism was further explored by in-situ DRIFTs. NO oxidation on LaCoO3/CeO2 catalyst followed the Langmuir-Hinshelwood mechanism, and toluene oxidation followed the Mars-van Krevelen mechanism.
Abstract: The modified activated coke (AC-N) supported Ni-Ce transition metal catalyst prepared by incipient-wetness impregnation method can simultaneously catalyze the ammonia selective catalytic reduction (NH3-SCR) reaction and CO oxidation reaction, realizing the removal of NO and CO under low temperature and oxygen-rich conditions. The Ni-Ce /AC-N catalyst can achieve high-efficiency conversion of NO and CO at 175–250 ℃, and the conversion rates of NO and CO are both above 95% in this temperature range. After modified by nitric acid, the active coke support has a stronger interaction with metal components, which is conducive to better dispersion of the active components on the catalyst surface, and improves the specific surface area and redox capacity of the catalyst. The synergistic effect between Ni and Ce results in more Ni2+ and Ce3+ species on the catalyst surface, which is beneficial to the improvement of catalytic activity.
Abstract: In this paper, Zhundong coal was used as the precursor of carbon material followed by activation by hydrothermal coupling with trace amount of K element. The influence of K concentration on the adsorption performance of as-prepared carbon material of NOx at low temperature was studied. The experimental results showed that when the concentration of K2CO3 in the activation solution was 0.0067 g/mL, the sample had good NOx adsorption performance, and the saturated NOx adsorption time was 3200 s. The pore structure of the sample developed well with the specific surface area of 708.6 m2/g. The samples were characterized by XPS, SEM and the adsorption process was studied by FT-IR. It was found that excellent adsorption properties of Zhundong coal derived carbon material were related with the surface structure. DFT method was employed to verify the reaction mechanism. The results showed that K could promote the formation of C–O bond which was the key factor for promoting the NOx adsorption. The best method and optimal process parameters for preparing Zhundong coal-based carbon materials by hydrothermal coupling with trace amount of K were obtained.
Abstract: With the residual carbon in coal hydrogasification semicoke as both reducing agent and dielectric component, Ni/carbon-based composite materials for microwave absorption were prepared. The synthesis process mainly involved loading of Ni species via an impregnation of nickel nitrate solution and then an in-situ carbothermic reduction. The effects of Ni load on the microstructure and properties as well as the related mechanism were studied. The experimental results showed that the electromagnetic parameters could be readily regulated by changing the Ni load, which occurred as a result of the accompanied changes in carbon content, graphitization degree, as well as the number of interfaces and defects. Hence, a good impedance matching could be easily achieved. At a carbothermal reduction temperature of 700 ℃, the composite with 20% Ni load showed the best microwave absorption performance. For a coating thickness of 2.5 mm, the minimum reflection loss was −42.6 dB and the corresponding effective bandwidth was 4.1 GHz; while the effective bandwidth could be up to 5.6 GHz under 2 mm coating thickness. The dominant microwave absorption mechanism was the dielectric loss, which mainly derived from the conduction loss due to graphite carbon and the polarization relaxation losses because of the existence of interfaces and defects.
Abstract: Transition metal oxide is a kind of catalyst with high catalytic activity for electrocatalytic oxygen evolution reaction. However, the catalytic activity is limited by the low electronic conductivity. The effective way to construct high performance electrode material or electrochemical catalyst is combining the nano material with conductive matrix material. The polymerized porphyrins supported on C3N4 were prepared by solvothermal method. The Co3O4/NC catalyst was prepared by Co modification and heat treatment of BDA-PY/C3N4. The physicochemical properties of the catalyst were characterized by XRD, SEM, TEM, XPS and FT-IR, and so on. The results indicate that Co3O4/NC-600 possesses a super-small nano-Co3O4 structure and high nitrogen content. The strong chemical bond between pyridinic N of the nitrogen-doped carbon and Co is formed, resulting in a synergistic effect, which makes the catalyst show good catalytic performance in OER reaction. Its Tafel slope is only 66.4 mV/dec and the minimum overpotential is 343.3 mV when the current density reaches 10 mA/cm2.
Abstract: Carbon assisted water electrolysis for hydrogen production usually added carbon sources (such as coal and biomass) into anode cell directly to form carbon slurry. This route always suffered from low current density due to the high mass transfer resistance between carbon particles and anode. The coal-based formcoke sacrificial anode was preparaed by co-forming and co-pyrolysis of coal, alkali-activated biomass and conductive graphite, and formcoke sacrificial anode was used in carbon assisted hydrogen production by water electrolysis. The efficiency of carbon assisted hydrogen production could be significantly improved at high current density (50 mA/cm2). The water electrolysis performance of formcoke sacrificial anode and its microstructure evolution were studied. Results showed the current density of formcoke sacrificial anode were 87 times higher than that of Pt anode at 1.23 V( vs. RHE), and the Tafel slopes also reduced by 41% compaired to that of Pt anode. The H2 formation rate of formcoke sacrificial anode was 2.75 times than that of Pt anode at 50 mA/cm2, while the potential of formcoke sacrificial anode was about 85% of Pt anode. The SEM, TGA, BET, FT-IR and XPS results showed that the sacrificial anode itself were oxidized during water electrolysis. Specifically the carboxyl C=O bond was oxidized to CO2, and the content of C–O bond increased significantly. This research provide a new insight and reference for carbon assisted water electrolysis for hydrogen production.
Abstract: Medium temperature coal tar pitch (ZCTP) was separated by Soxhlet extraction using toluene-pyridine and n-heptane-tetrahydrofuran as solvents to obtain the group components. Then, their composition and structure were analyzed. The results show that, in comparison with ZCTP, toluene-insoluble pyridine soluble (TI-PS) and n-heptane-insoluble tetrahydrofuran soluble (HI-THFS) are more thermally stable, exhibiting a decrease weight loss of 41.51% and 28.85% and an increase residual carbon rate of 56.95% and 47.63%, respectively. In addition, the C=C contents of TI-PS and HI-THFS are 6.69% and 3.26% higher than that of ZTCP, reaching 75.57% and 73.14%, and the pyridine nitrogen contents of TI-PS and HI-THFS increase about 16 and 8 percentage points. Both TI-PS and HI-THFS were used to prepare mesophase pitch. It is found that M-HI-THFS is mainly consisted of small and medium area type with some fine mosaic structure and low optical anisotropy content. While M-TI-PS has about 80% optical anisotropy content and displays a wide range of optical weave. However, it is difficult for ZCTP to form a stable regional optical fabric structure, just exhibiting a mosaic optical fabric.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
