Abstract: Fischer-Tropsch synthesis is the best way and development direction for the conversion of syngas into clean liquid fuels and high value-added chemicals. Iron-based catalysts are widely used in Fischer-Tropsch synthesis reactions. Studies have shown that iron carbide is the active phase of iron-based Fischer-Tropsch synthesis catalysts. In recent years, the preparation of iron carbide for Fischer-Tropsch synthesis directly has become a hot research topic of iron-based Fischer-Tropsch synthesis catalysts. In this paper, the phase types of iron carbide are summarized, the preparation methods of iron carbide (mainly including wet chemical synthesis, heat treatment carburizing, iron-based organic framework material pyrolysis, sol-gel method) and its application in Fischer-Tropsch synthesis are reviewed, and the application prospect and research direction of iron carbide in Fischer-Tropsch synthesis are prospected.
Abstract: SSZ-13 zeolites were synthesized by conventional hydrothermal method and the Cu-SSZ-13 zeolite catalysts were then prepared by Cu ion-exchange and used in the selective catalytic reduction of NOx with NH3 (NH3-SCR); the effect of various preparation parameters including the organic template agent (OSDA) dosage, silicon source, aluminum source, H2O/Si ratio, Si/Al ratio and aging time on the morphology, crystal size, acidity, state of Cu2+ sites and the catalytic performance of Cu-SSZ-13 in NH3-SCR were investigated. The results indicate that silica sol (JN25) and Al2(SO4)3 are appropriate as the silicon and aluminum sources, respectively, to prepare SSZ-13 zeolites with small crystals, high crystallinity and high activity in NH3-SCR. With the increase of Si/Al ratio, the crystal size of SSZ-13 increases and the copper content loaded on Cu-SSZ-13 decreases, leading to the degradation of NH3-SCR activity. A high H2O/Si ratio of 88 is conducive to forming larger SSZ-13 crystals, whilst increasing the OSDA dosage is beneficial to improving the crystallinity, reducing the crystal size, and accordingly enhancing the catalytic activity of Cu-SSZ-13 in NH3-SCR. In addition, a relatively longer aging time can also reduce the crystal size and raise the catalytic activity of Cu-SSZ-13. In particular, the Cu-SZ13-A10 zeolite catalyst synthesized with a Si/Al ratio of 10 (with the gel composition of 1SiO2 : 0.01Al2(SO4)3 : 0.3NaOH : 0.4SDA : 88H2O; JN25 as silicon source and aging for 2 h) exhibits high activity in NH3-SCR; under a high GHSV of 240000 h−1, the NO conversion reaches 60% at 200 ℃ and keeps at 100% in the moderate-high temperature range. These results should be useful for the regulation of SSZ-13 zeolite morphology and the preparation of high efficient Cu-SSZ-13 catalysts for NH3-SCR.
Abstract: A series of Co-doped Mn oxide catalysts with different Co/Mn molar ratios were prepared by co-precipitation method, which was systematically characterized by XRD, SEM, H2-TPR and NH3-TPD etc. Co-doped Mn oxide catalysts are evaluated for NH3-SCR activity and resistance to SO2 and/or H2O, and the Co(1)-MnOx catalyst with Mn/Co molar ratio of 1∶1 performs the best catalytic performance, which achieved higher than 90% NOx conversion in the temperature range of 100−275 °C and possessed better SO2 and H2O resistance. The Co(1)-MnOx catalyst presented a sphere-like structure possessing a relatively large surface area. Doping of cobalt greatly improved the high-valent metal ions and chemisorbed oxygen content of Co(1)-MnOx catalyst surface, and the catalyst possessed abundant active species and acid sites and apparent activation energy of the catalyst was reduced, which makes Co(1)-MnOx a highly effective NH3-SCR catalyst.
Abstract: Based on the complicated preparation of current diesel vehicle exhaust gas denitration catalysts, an in-situ deposited composite oxide catalyst, CeO2-WO3 mixed oxide catalyst, was prepared by electrodeposition and hydrothermal methods, which was loaded on the titanium mesh and applied to the selective catalytic reduction denitration of diesel vehicle exhaust. Denitration performance of the catalysts was tested by a fixed bed reactor, and the influence of different electrodeposition time of CeO2 was investigated. The results demonstrate that 20 min is the best electrodeposition time of CeO2 (100% NOx conversion at 250−350 ℃). The high dispersion of active CeO2 on WO3 promotes the synergistic effects among different components. The as-prepared catalysts were characterized by SEM, XRD, XPS, H2-TPR, NH3-TPD and in-situ DRIFTS. It is evident that Ce3+ is successfully introduced by loading CeO2, which enhances the chemisorption of oxygen. Meanwhile, the increased acidity including both weak acid and medium-strong acid sites of CeO2-WO3 composite catalyst is observed, which improves the co-adsorption of NH3 on Lewis acid and Brønsted acid simultaneously and facilitates the denitration process. Through the characterization by in-situ DRIFTS, it is elucidated that the NH3-SCR reactions are mainly carried out following the Eley-Rideal (E-R) pathway in a medium-temperature range (250−350 ℃).
Abstract: Nitrogen-doped carbons (Nano-NC) are often employed as functional supports for boosting oxygen reduction reaction (ORR) over Pt-based catalysts, however, the mechanism of N doping on the adsorption and activation of molecular oxygen on Pt active sites is still not clear. Herein, Nano-NCs as the supports were prepared by a facile NH3 antipyretic method, which allowed to tune the kinds of nitrogen species in carbon matrix and their contents by adjusting the NH3 antipyretic temperatures. With such an exquisite control, the Pt nanoparticles loaded on the as-obtained Nano-NC showed an optimal Pt particle size (2.10 nm), a higher content of Pt0, a large electrochemically active surface area, and fast electron transport ability. As a consequence, the Pt/Nano-NC-800 catalyst with the optimal N-doping showed an outstanding ORR performance with half-wave potential of 0.80 V vs. RHE, limit diffusion current of 5.37 mA/cm2 and improved methanol/CO anti-poisoning, which is superior to the commercial Pt/C catalyst (20%, JM), and most of previously reported Pt-based catalysts. This work may pave a way for the design of the advanced supports for Pt-based catalysts for the ORR applications.
Abstract: N-doped MoP-based core-shell nanorods (N-MoP/NC-8) were synthesized by in-situ phosphorization of molybdenum trioxide-ethylenediamine organic-inorganic hybrid material (MoO3/EDA) via a gas-solid reaction; their electrocatalytic performance in hydrogen evolution was investigated. The results indicate that N-MoP/NC-8 is composed of N-doped molybdenum phosphide (MoP) coated by N-doped carbon layer. The introduced electronegative atom can regulate the electronic structure of the active phase, whilst the combination of carbon layer and MoP can inhibit the internal agglomeration of MoP, resulting in large pore volume and surface area. Owing to such a dual effect, the N-MoP/NC-8 catalyst shows excellent performance in electrocatalytic hydrogen evolution and great charge transfer ability; the overpotential is 92 mV at 10 mA/cm2 current density in 0.5 mol/L H2SO4 solution, with a Tafel slope of 68 mV/dec and a durability of above 20 h.
Abstract: In this study, a small-sized CoNi bimetallic co-catalyst was synthesized in situ on g-C3N4 nanosheets using a simple chemical reduction method. The physicochemical properties of the prepared CoNi/g-C3N4 were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The photocatalytic degradation of RhB showed that the CoNi bimetallic co-catalyst could effectively improve the separation efficiency of photogenerated carriers in g-C3N4, thus enhancing the photocatalytic activity. The highest catalytic activity of CoNi/g-C3N4 was achieved when the molar ratio of CoNi was 1∶1, with a degradation rate of 0.01633 min−1, which was 3.9 times higher than that of normal g-C3N4 under visible light irradiation. The photocatalyst maintained good photocatalytic activity after five cycles. The main active species of the reaction is the superoxide radical ($\cdot {\rm{O}}^-_2 $).
Abstract: Interface regulation is an effective strategy to improve the interaction between carrier and active metal center, which can improve the catalytic activity and oxygen storage capacity of the catalysts. In this paper, Ni/CeO2 catalysts supported on CeO2 with different morphologies (nanorods, nanocubes, nanoctahedrons and nanopolyhedrons) were synthesized. The structure dependence of the catalysts for the low temperature chemical looping dry reforming of methane (CL-DRM) was investigated. The characterization results showed that Ni species were highly dispersed on the surface of CeO2 carrier, and some Ni ions entered the CeO2 lattice, resulting in the increase of oxygen vacancies. The Ni/ceria-rods catalyst had the highest reducibility, the most oxygen vacancies and the highest oxygen storage capacity. The irregular CeO2 nano single crystal of about 10.3 nm in the Ni/ceria-polyhedra led to high specific surface area and high reducibility which exhibited the highest redox activity and redox stability in low-temperature chemical looping dry reforming of methane at 550 ℃. This study provided a new strategy for the design of efficient metal/CeO2 catalysts, which was expected to promote the application of cerium-based catalysts in chemical looping technology.
Abstract: The hydrolysis process of tetraethyl orthosilicate (TEOS) was tracked by FT-IR analysis, and the effect of hydrolysis time on the distribution of titanium species in TS-1 zeolites was discussed through XRF and UV-Vis. The catalytic oxidation performance of TS-1 zeolite was tested by 1-hexene epoxidation as a model reaction. The results show that moderate hydrolysis of tetraethyl orthosilicate can effectively inhibit the formation of extra-framework Ti and increase the content of framework Ti. However, shorter or longer hydrolysis time is not conducive to the entry of titanium into the skeleton, and reduce the catalytic performance of TS-1 zeolites. TS-1 prepared with 2 h TEOS hydrolysis time has the best catalytic performance for epoxidation of 1-hexene. Under the reaction conditions of atmospheric pressure and 60 ℃, the conversion of 1-hexene can reach 37.5% and the selectivity of 1,2-epoxy hexane can maintain at about 85%, and the result has a guiding role for the development of olefin epoxidation catalyst.
Abstract: In this study, the Co-WOx catalyst was successfully prepared by directly introducing Co2+ dopant in a dynamic solvothermal synthesis process, and the obtained Co-WOx was used for the catalytic epoxidation of 1-hexene. The structures of WOx before and after the doping were analyzed by XRD, SEM, TEM, Raman, XPS as well as in-situ NH3-FTIR. The results show that the doping of Co2+ has not obvious effect on the crystal phase and main growth direction of WOx, but can effectively reduce the content of Brönsted acid (B acid) site on the surface of WOx catalyst and increase the content of oxygen vacancy at the same time. In the epoxidation reaction, the obtained Co-WOx catalyst (Co/W = 0.1) can increase the selectivity of 1,2-epoxyhexane from 26.9% of pure WOx to 55.7% with a 5.3% decrease in 1-hexene conversion. The improvement of Co-WOx performance is mainly attributed to two aspects: (1) the reduction of B acid site on the surface of WOx inhibits the ring opening hydrolysis of 1,2-epoxyhexane; (2) The increase of oxygen vacancies on the surface of WOx promotes the activation of H2O2, ensuring that the conversion rate of 1-hexene does not decrease significantly, and an increase in the utilization of oxidant H2O2 by 13.5%. Combined with the characterization results and reaction data, the epoxidation mechanism of 1-hexene with W−O−OH as active intermediate is proposed.
Abstract: In this paper, four kinds of LaFeO3 perovskite catalytic materials with different ball milling time were prepared by solid phase milling method and used to catalyze the wet air oxidation of phenol. The effect of milling time on the performance of LaFeO3 perovskite catalyst for wet air oxidation of phenol aqueous solution was investigated. LaFeO3 perovskite catalytic materials were characterized by XRD, H2-TPR, TG-DTA, FT-IR, N2 physical adsorption and XPS. The results show that when the reaction temperature is 200 ℃, the air pressure is 5 MPa and the initial concentration of phenol is 4000 mg/L, the final COD removal rate of LaFeO3-6 catalytic material is 94.5% after catalytic oxidation of 240 min.
Abstract: Co/HZSM-5 catalyst was fabricated for catalytic dehydrogenation of propane to propylene, which was pretreated to allow the reaction to react at low temperatures. A response surface approach was employed to examine the effect of process conditions on the reaction. The morphological and oxidative performance of Co/HZSM-5 was characterized by XRD, XPS, SEM, NH3-TPD, H2-TPR, and nitrogen physical absorption-desorption. Besides, the in-situ catalyst performance was evaluated by a fixed-bed reactor. Combining the actual experimental conditions, the optimal process conditions parameters obtained by the response surface method were as follows: a reaction temperature of 461 °C, a Co loading of 2.4%, and a GHSV of 4300 h−1. At this point, the propylene yield reached 27.7% and the corresponding propylene selectivity was up to 93.8%.
Abstract: Oct@PMMA microcapsules phase change materials were synthesized by the emulsion polymerization method, and the energy storage performance and thermal stability was improved by selecting PVP as dispersing agent and PETRA as cross-liking agent. The chemical and physical properties of the microcapsules were characterized by FT-IR, XRD, DSC and TG. The results showed that the thermal performance and yield were improved by PVP, increasing the stability and dispersibility of emulsion droplets, the enthalpy in phase transition was 105.6 J/g and the yield reached 98.01%, the thermal stability was enhanced by PETRA and the decomposition temperature was up to 175 ℃.
Abstract: A series of Mn-Fe binary oxides with different molar ratios were synthesized by coprecipitation method, and their adsorption behaviors of gaseous arsenic and selenium in flue gas at different temperature were investigated. The simultaneous adsorption characteristics of As2O3 and SeO2 on Mn-Fe binary oxide were studied. To avoid secondary pollution for adsorbent utilization, As/Se leaching properties in Mn-Fe binary oxides were evaluated. Results show that the adsorption capacity of As2O3 and SeO2 on the Mn-Fe binary oxides increases firstly and then decreases with the increasing Mn content. The adsorption capacity reaches the maximum when the molar ratio is 1∶1. The optimum adsorption temperatures of As2O3 and SeO2 are 750 and 600 ℃, respectively. During the process for As2O3 and SeO2 adsorption on Mn-Fe binary oxide simultaneously, Mn-Fe binary oxides preferentially adsorb As2O3, while SeO2 is inhibited. In addition, the pre-adsorption SeO2 can enhance the adsorption activities of adjacent atoms, which is beneficial for As2O3 adsorption. The concentration of arsenic and selenium in the leaching solution of spent Mn-Fe binary oxide is far lower than the control limit, which will be no secondary pollution in the process of utilization with fly ash.
Abstract: Two industrial wastes, spent FCC catalyst (sFCCc) and blast furnace ash (BFA), were used as catalysts in the fast pyrolysis of sawdust, and the catalytic pyrolysis reaction characteristics of sawdust in the temperature range of 400−700 ℃ were explored. The results showed that both catalysts promoted the conversion from liquid products to gaseous products, and the highest gas yield was 52.60% at 700 ℃ catalyzed by BFA. The sFCCc had stronger deoxygenation activity at 500−600 ℃, resulting in higher CO and CO2 production in gaseous products. While BFA had higher polycondensation and dehydrogenation activity at 600−700 ℃, and promoted the formation of polycyclic aromatic compounds and H2. Pyrolysis oil was mainly composed of phenols. The sFCCc promoted the conversion of methoxy phenol to benzenediol. FT-IR analysis of pyrolysis oil showed that sFCCc promoted the removal of C−O and C=O, resulting in decreased acid and ester compounds and increased CO2 yield.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
