Abstract: The catalytic hydrogasification of activated carbon/bituminous char/anthracite char with the different catalysts were performed in a pressurized thermogravimetry analysis (PTGA). The GC, BET were used to characterize the physical structure and chemical reaction process of carbon. The function principle of Co to the carbon-hydrogen reaction was preliminarily obtained. The results showed that the catalytic activity of transition metals (Fe, Co, Ni) was significantly better than that of alkali metals and alkaline earth metals during the process of activated carbon hydrogasification. There were two catalytic zones of low temperature (600−750 ℃) and high temperature (> 800 ℃) in the catalytic process. The emergence of the low temperature catalytic zone could be attributed to the interaction between the transition metal oxides and carbon. The transition metal was embedded in carbon layer structure during the activated carbon hydrogasification, then parts of carbon structure was activated, resulting in the cleavage of carbon-carbon bonds. The adequate active hydrogen could be supplied by Co at 850 ℃ when the pressure was beyond 1 MPa. Briefly, the reaction temperature was the crucial factor for the cleavage of carbon-carbon bonds. The model carbon with higher specific surface area and weaker carbon structure could be converted efficiently even with lower loading amount of catalyst.
Abstract: In this paper, two kinds of coal (Baiyinhua lignite and coal using in Ezhou Power Plant) were selected to study the occurrence of heavy metals including arsenic (As), selenium (Se) and lead (Pb) in coal and their release behaviors during the ashing process. The influence of ashing conditions on the mineral conversion was also examined by the combination with the changes of minerals in coal. The burn-out temperature of the coal was determined from the thermal weight loss curve by extrapolation method, and then the coal sample was ashed according to the National Standard Method of China. The obtained ash samples were characterized by XRD, XRF, and TG-DTG to analyze the change characteristics of coal minerals at different ashing temperatures. The content and occurrence of As, Se and Pb in coal samples were extracted by sequential chemical extraction method. The heavy metals in the ash sample were extracted by HNO3 + HF, and the heavy metal content in the extract was detected by Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The results show that the heavy metal in BYH coal is mainly As in the form of sulfide bound state, which leads to the increasing volatility of As with temperature easily. However, the heavy metal in EZ is mainly sulfide-bound Pb, which makes it easy to release with temperature. Se in coal mainly exists in the form of organic bound state and sulfide bound state. During coal ashing, kaolin is gradually dehydroxylated into metakaolin and finally converted into mullite; pyrite is oxidized to form hematite; gypsum is dehydrated to form anhydrite. The release rate of heavy metals is greatly affected by the combustion temperature during the ashing process. High content of heavy metals in the sulfide bound state results in high release rate with increasing the temperature.
Abstract: In order to obtain the NO formation mechanism during the coal combustion, the heterogeneous oxidation of nitrogen-containing char by CO2 were investigated based on density functional theory. Simplified char models containing pyrrole nitrogen or pyridine nitrogen were selected as the carbonaceous surfaces. Geometric optimizations were carried out at the B3LYP-D3/6-31G(d) level. Energies of optimized geometries were calculated at the B3LYP-D3/def2-TZVP level. The results show that CO2 oxidation of nitrogen-containing char is composed of three stages: namely CO2 adsorption, CO desorption and NO desorption. In the reaction of CO2 heterogeneous oxidation of pyrrole nitrogen-containing char, CO2 molecules tend to absorb in the C−O−down mode (C−C bonding, N−O bonding) to form a five-membered heterocyclic structure containing nitrogen and oxygen atoms. Then, the surface carbonyl groups and N(O) are formation as the C−O bonds of the original CO2 molecules in the five-membered ring broken to desorb CO and NO, respectively. The reaction is 401.2 kJ/mol endothermic, and the highest energy barrier is 197.6 kJ/mol. In the reaction of CO2 heterogeneous oxidation of pyridine nitrogen-containing char, CO2 molecules tend to form six-membered heterocyclic ring containing nitrogen and oxygen atoms after adsorption in the C−O−down and C−C bonding and C−O bonding mode. And then CO and NO molecules are desorbed. The reaction is 598.6 kJ/mol endothermic, and the energy barrier of rate-determining step is 292.0 kJ/mol.
Abstract: The morphological structure of six samples including the rapid pyrolysis soot of solid fuels (coal, biomass), the soot from non-catalytic partial oxidation (NCPOX) of natural gas in a laboratory pilot plant and an industrial plant, the commercial carbon black in natural gas furnace/coal tar furnace, were characterized by using a transmission electron microscope. Based on atmospheric thermogravimetric analyzer, the non-isothermal method (50–800 ℃) was adopted to study the ignition point and the oxidation reaction rate of soot, and the oxidation reaction kinetic parameters of soot was obtained. Studies showed that the physical and chemical properties of various soot were quite different. The soot from the rapid pyrolysis of coal and biomass presented a higher sphericity and a larger particle size. The Lab-NCPOX-soot was formed at a lower temperature which caused the particle being wrapped by a carbon capsule. The Ind-NCPOX-soot had a hollow structure and a small particle size. The reactivity of the Lab-NCPOX-soot is close to that of the Ind-NCPOX-soot, which is 3.1 times that of the commercial natural gas furnace carbon black and 3.2 times that of the commercial coal tar furnace carbon black; the reactivity of NCPOX-soot is 9.0 times of the rapid pyrolysis soot of coal, and 26.6 times of the rapid pyrolysis soot of biomass. The activation energy of 2 kinds of NCPOX-soot and 2 kinds of commercial carbon blacks present staged forms with increasing temperature. The activation energy of the 2 rapid pyrolysis soot was basically unchanged with increasing the temperature.
Abstract: With coal gangue (CG) as the carbon-containing carrier, starch as supplementary C source and nickel nitrate as Ni source, Ni/C/CG composite microwave absorbing materials were prepared by a solution impregnation and then a carbothermal reduction process. The influence of the carbothermal reduction temperature on the composition, microstructure and performance of materials was carefully studied. It was found that, the carbothermal reduction temperature had a great effect on the crystalline state of carbon and Ni, as well as the size of Ni particles, further greatly affected the electromagnetic properties, especially the dielectric properties of the materials. Due to the combination of good impedance match and strong microwave attenuation ability, the Ni/C/CG composites prepared under a wide temperature range of 600−800 ℃ all displayed excellent microwave absorption performance. For the sample heat-treated at 800 ℃, the minimum reflection loss could reach −20.9 dB at 12.9 GHz and the corresponding effective absorption band was 3.7 GHz with a coating thickness of only 2 mm. In addition, the dielectric loss was the dominant microwave absorption mechanism, which mainly originated from the conductive loss caused by the graphite carbon and Ni particles, and the interfacial polarization loss due to the existence of interface between Ni, C and CG.
Abstract: Direct, nonoxidative conversion of methane towards olefins/aromatics is a hot topic in the background of “carbon peak, carbon neutrality”, owing to zero CO2 emissions, high carbon atom utilization efficiency and hydrogen production. In the present paper, the advances of methane dehydroaromatization (MDA) and direct nonoxidative conversion of methane to olefins, aromatics, and hydrogen (MTOAH) are reviewed, based on our research works and the publications from 2018 to 2021. The determination of active sites, reaction intermediates, reaction mechanism, catalyst modification and improvement were considered. Finally, the future prospect was given for the direct nonoxidative conversion of methane to olefins/aromatics.
Abstract: A series of iron sulfide catalysts were prepared in 5% H2S/N2 atmosphere at different pre-sulfidation temperatures, and their catalytic activity for naphthalene hydrogenation was studied at 360 ℃ in 1% H2S/H2 atmosphere at 5 MPa. The component transformation of the catalyst under varied pre-sulfidation temperature and reaction conditions was researched using MES, XRD and XPS. The results revealed that the sulfidation process was in the form of sulfurizing from surface to interior in the order of FeS2→FeS, Fe1–xS→Fe3S4→Fe2O3 during which transferring sulfur to the body phase was benefited from the rise of temperature. After contacting 1% H2S/H2 gas, the particles rapidly transformed to Fe1–xS from outside to the inside. By adjusting sulfidation conditions, the Fe1–xS content was high while the particle size was small, which made it possible to obtain the greatest activity of the catalyst.
Abstract: The Mo1Sn2 catalysts with a Mo/Sn molar ratio of 1∶2 were prepared by the hydrothermal method, and their structure was regulated by changing the calcination temperature (400–700 ℃). The effect of the structural transformation of catalysts on the performance of selective oxidation of dimethyl ether (DME) to methyl formate (MF) was studied. It was found that the Mo1Sn2 catalyst calcined at 400 ℃ exhibited good performance in the oxidation of DME to methyl formate, showing a DME conversion of 9.2% and the MF selectivity of 86.9% at 110 ℃ and under atmospheric pressure without the generation of COx. The catalysts were systematically characterized by XRD, Raman, XPS, TPD, H2-TPR and in-situ FT-IR. The results showed that the low-temperature calcination was favorable for the formation of MoOx structure and more Mo5+ species on the catalyst surface, resulting in the enhanced acidity and redox ability of the catalyst, and the increase of medium to strong basic sites on the catalysts. In such case, the activity and methyl formate production of the catalyst were significantly promoted.
Abstract: Regioselective effects of electron and steric hindrance of catalytically active intermediate HCo(CO)2L coordinated by phosphine ligands on α-hexene hydroformylation were studied based on density functional theory. Phosphine ligands have strong electron-attracting capacity that raises the stability of HCo(CO)2L. PPh3 with large steric hindrance suppresses the coordination of α-hexene with HCo(CO)2L as well as the secondary reaction of the C=C with the Co–H via the branched chain pathway. The energy barrier for the transition state containing linear chain alkyl Co intermediate is lower about 2.73 kcal/mol than that for the transition state with branched chain alkyl Co intermediate, indicating that linear chain pathway is dominant in the addition reaction. Both the electron and steric hindrance effects of phosphine ligands determines the pathway of addition reaction between the C=C of α-hexene and the Co–H. The linear chain addition is preferable that mainly produces linear chain aldehydes.
Abstract: Versatile and environmentally benign dimethyl carbonate (DMC) synthesized by propylene carbonate (PC) and methanol via transesterification is green and energy efficient. A series of solid base catalysts derived from F-Ca-Mg-Al layered double hydroxides (LDHs) with different NaF amount were prepared, characterized and tested for the transesterification reaction. The properties of the catalysts modified by fluorine have improved obviously. The catalytic activity increases in the order of: FCMA-0.8 > FCMA-0.4 > FCMA-1.2 > FCMA-1.6 > FCMA-0, which is consistent with the total basic sites amount and the strong basic sites amount. FCMA-0.8 has the best catalytic activity as pure CaO catalyst, and the PC conversion, DMC selectivity and DMC yield are 66.8%, 97.4% and 65.1%, respectively. Furthermore, the DMC yield for FCMA-0.8 just decreased 3.9% (33.2% for CaO catalyst) after 10 recycles. FCMA-0.8 has good prospects in the transesterification of PC with methanol to DMC for industrial application.
Abstract: Limited by the steric hindrance, hydrogenation of the final unsaturated ring in polycyclic aromatic hydrocarbons remains a challenge. In this work, a series of Pt-Ni/NiAlOx catalysts were synthesized by impregnation method to enhance the adsorption of aromatics, and phenanthrene was served as the model compound. The effects of Pt content on the structure and saturation performance of Pt-Ni/NiAlOxcatalysts were systematically investigated. When the saturation reaction was performed at 300 ℃, 5 MPa and a weight hourly space velocity of 52 h−1, the selectivity of perhydrophenanthrene could be enhanced from 40% over Ni/NiAlOx catalysts to 67% over 0.5Pt-Ni/NiAlOx catalysts with 0.5% Pt loading. Meanwhile, the obvious reaction rate and turnover frequency were also improved from 1.53×10−3 mol·kg−1·s−1 and 14.64×10−3 s−1 to 1.81×10−3 mol·kg−1·s−1 and 22.16×10−3 s−1 respectively. This is related to the modified stability of metallic electron-deficient structure of Ni by Pt introduction in phenanthrene hydrogenation, which can promote the adsorption of aromatic hydrocarbons as well as the hydrogenation activity.
Abstract: To investigate the catalytic properties of β zeolite for catalytic alkylation of C9 aromatics with propylene, β zeolites modified with phosphorus were prepared by using impregnation method. The modified β catalysts with different loading amount of phosphorus were characterized by XRD, SEM, EDX, MAS NMR, Py-IR, N2 adsorption-desorption, and NH3-TPD. The results showed that the morphology and crystal structure of the β zeolite catalysts did not change obviously after modification with phosphorus. However, the specific surface area and the surface Si/Al mass ratio of the β zeolite decreased with the increase of amount of phosphorus. It was proved that the interaction between the phosphorus and β zeolite could affect the acid strength distribution of β zeolite and the catalytic performance of alkylation of C9 aromatics. In comparison with β zeolite, the β zeolite modified with 0.5% phosphorus (β-0.5P) had good catalytic performance in alkylation reaction of C9 aromatics. The ratio of C12+ aromatics in the alkylation products was up to 17%, and the value of m1,3,5-TMB/mC9 was increased by 5.3%. The β-0.5P catalytic activity showed stable after reaction for 10 h. However, when the loading amount of phosphorus on β zeolite was too high, the alkylation activity of the catalyst decreased and the isomerization and disproportionation performance of the catalyst increased.
Abstract: The selective oxidation of primary alcohols represents a premier route for the synthesis of aldehydes as intermediates of multiple commercial fine chemicals such as drugs and perfumes. In particular, catalytically selective oxidation of primary alcohol in use of oxygen is of great interest, owning to its high efficiency, solvent-free, and easy separation. As such, choosing this route to pursue desired atomic economy has been an essential topic of common concern in both academic and industrial circles in recent years. Boron nitride with graphite like structure is a new catalyst developed in recent years, which has the characteristics of stability and good thermal conductivity. In this contribution, three kinds of boron nitride (BN) with different structural characteristics were used as carriers to support Au nano metal for selective oxidation of benzyl alcohol. It is found that the crystallinity and specific surface area of the carriers have a great influence on the size of active phase Au. The specific surface area of Au/BN500 is four times higher than those of the Au/BN600 and Au/BN700. Compared with Au/BN700, Au/BN500 catalyst has better dispersion and smaller particle size (13 vs. 3.2 nm). The catalytic activity of Au/BN500 is about twice as much as those of the other two, and about 30% activity is lost within 5 h. The results in this paper provide enriched experimental and theoretical references for rational design and development of novel high-performance boron nitride-based oxidative dehydrogenation catalysts.
Abstract: Synthesis of low-cost, high-activity and high-stability Pt-based catalysts is of great importance to the large commercialization of proton exchange membrane fuel cell (PEMFC). Doping non-precious metals such as cobalt (Co) with Pt is attractive due to the reduced depletion of Pt and, more importantly, the enhanced activity on the oxygen reduction reaction (ORR) compared with pure Pt. In this work, carbon-supported platinum-cobalt nanoparticles (NPs) were prepared by the impregnation reduction method for the ORR catalyst. By changing the heat treatment temperature, the structure, the crystal phase and the size of the Pt3Co nanoparticles could be controlled. TEM and XRD characterizations show that larger size NPs with higher alloying degree are obtained at higher temperature. The electrochemical results demonstrate that the Pt3Co NPs at 800 ℃ have the highest mass activity (0.41 A/mgPt) and the best stability among all the samples due to their lower particle size and higher alloying degree. Further Density functional theory (DFT) calculation shows that the surface of the Pt3Co structure with high alloying degree can reduce the rate-determining step barrier and improve the ORR activity.
Abstract: BiOCl, BiOBr and BiOI were prepared by hydrothermal and solvothermal methods. XRD, SEM, photocurrent density curve and UV-vis were used to characterize the crystal structure, surface morphology and photoelectric properties. The band structure and density of states of BiOX were calculated by DFT. With the atomic number of halogen increase, the dispersion of the Fermi level near the semiconductor conduction band decreases, and the band gap becomes smaller. The photocatalytic activity of BiOCl, BiOBr and BiOI was evaluated by photocatalytic degradation of Rhodamine B (RhB), and the degradation rate of RhB in 60 min for BiOI could reach 100%. Meanwhile, the main active groups in the process of photocatalytic degradation of RhB were explored by radical trapping experiment.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
