Abstract: Metal-modified SiO2 supports were prepared by sol-gel method with Mn, Zn, Zr, and Sr cations doping, and then iron-based catalysts supported on modified SiO2 were prepared by the impregnation method. The iron-based catalysts were characterized by XRD, N2 adsorption, and XPS. The reduction adsorption property of H2 and hydrogenation property of CO were studied by temperature programmed methods. The interaction between catalyst and H was studied by kinetic analysis. The results indicate that metal modification has no influence on phase composition of Fe and surface electronic state of Fe species. However, the modification reduces surface area of catalyst and dispersion of active phase, weakens adsorption ability of H2 and lowers H2 desorption activation energy of the catalyst. Zn and Zr doping restrain reduction of catalysts, while Mn and Sr doping promotes reduction of catalysts. The doping of Mn, Zn and Zr inhibits adsorption of CO on the catalyst surface, while Sr promotes dissociation and adsorption of CO. Mn, Zn, Zr and Sr promote C-C coupling and hydrogenation reaction. Among them, Mn and Zr are more prominent.
Abstract: Selective oxidation of methanol to methyl formate (MF) is one of the most attractive processes to get valuable methanol-downstream products, where the supported Au and Pd catalysts were proved rather effective at low temperature. To search for highly active, regenerable and practical catalysts as well as to reveal the synergy of Au-Pd and reaction mechanism for the methanol oxidation, a series of silica supported Au-Pd nanoparticles (Au-Pd/SiO2) were prepared and their catalytic performance in the oxidation of methanol to MF with molecular oxygen was investigated in this work. The results indicate that the Au2-Pd1/SiO2 catalyst with an Au+Pd loading of only 0.6% and a Au/Pd mass ratio of 2 exhibits excellent performance in the methanol oxidation with oxygen; the conversion of methanol over Au2-Pd1/SiO2 reaches 57.0% at 130℃, with a selectivity of 72.7% to MF. Various characterization results illustrate that the Au-Pd bimetallic nanoparticles (2-4 nm) are highly dispersed on the silica surface, inclined to take a twinned structure and present the (111) planes, which may contribute to the high activity of Au-Pd/SiO2 in the oxidation of methanol to MF. A possible reaction mechanism was proposed on the basis of DRIFTS results:methanol was first activated by surface oxygen on the interface of Au-Pd nanoparticles, forming the chemisorbed methoxy species; the methoxy species was then deprotonated to adsorbed formaldehyde species, which reacted with another methoxy species, producing MF by nucleophilic attack and subsequent β-H elimination.
Abstract: In this work, CuZnAlOx (CZA) catalysts prepared by coprecipitation method and a series of yB/CZA catalysts with various boron loadings (y=0.28%, 0.38%, 0.73%, 0.89% and 4.10%) prepared by impregnation method were used in the methanol steam reforming for hydrogen production. In addition, the B-modified CZA catalysts were deeply characterized by different techniques such as ICP, BET, SEM, N2O chemisorption, TEM, XRD, H2-TPR and XPS to explore the structure-activity relationship. The characterization results revealed that the introduction primarily affected the Cu dispersion, reductibility and the interaction between the boron and copper species. The 0.38B/CZA catalyst revealed the optimum catalytic performance among the researched catalysts, which were due to the presence of highly dispersed Cu particles and the strong interaction between the boron and copper species. The 93% methanol conversion, the CO selectivity as low as 0.3%, and the long-time stability with 102 h time on stream were obtained over it when the reaction conditions were 250℃, n(H2O):n(CH3OH)=3 and GHSV=9000 mL/(g·h).
Abstract: Nanosheets MoS2 with only 6 layers have been successfully synthesized by hydrothermal method and used as support to prepare a series of Pt and PtM (M=Ru, Pd, Co and Ni) bimetallic catalysts for low temperature aqueous-phase reforming of methanol (APRM) to produce hydrogen. Among those catalysts, PtCo supported on MoS2 nanosheets catalyst exhibited the best performance, and its turnover frequency (TOF) of H2 formation reached 37142 h-1 at 220℃. The N2 adsorption-desorption, TEM, H2-TPR and XPS results showed that PtCo/MoS2 performed the highest reduction degree, and the strong electronic interaction between Pt and MoS2 enhanced the adsorption and activation of methanol on the electron-deficient Pt, thus promoted the methanol reforming.
Abstract: By comparing the catalytic performance of toluene methanol alkylation over zeolites with different pore structure, it was found that the effective matching of the zeolite pore size with the molecular dynamics size of the target aromatic compounds and the constrained management of the reaction path by pore confinement effect are essential for achieving high performance of alkylation. Combined with XRD, BET, NH3-TPD and SEM characterization, it has been confirmed that ZSM-5 with Si/Al ratio of 60 modified by successively loading La2O3 and P2O5 had better hydrothermal stability of the frameworks and most of the strong acidic sites on its internal and external surface were selectively eliminated while the weak and medium strong acidic sites were remained as the active sites of alkylation. The obtained MAT-HZSM-5 exhibited high methanol alkylation efficiency and good stability under nitrogen reaction atmosphere. There was no obvious deactivation during 500 h reaction. The conversion of toluene was maintained at 35%-38%, the selectivity of xylene was 60%-77%, and the methanol alkylation efficiency was higher than 90%.
Abstract: A series of tungsten modified MnOx-Fe2O3 catalysts with different tungsten contents were prepared by sol-gel method. The influence of tungsten on N2 selectivity of NH3-SCR reaction was investigated particularly. Physical and chemical properties of the catalysts were characterized by means of XRD, BET, XPS, H2-TPR, Raman and in situ DRIFTS. The results showed that N2 selectivity of NH3-SCR at high temperature was significantly improved by introducing tungsten. NH3-SCR possessed the best catalytic performance when the tungsten content was 15% (mass ratio), as well as N2O concentration was less than 0.003% within the range of 50-250℃. The primary causes were the phase change from α-Fe2O3 to γ-Fe2O3 due to the introduction of appropriate amount of WO3. Besides, the interaction between tungsten and manganese formed a new amorphous MnWO4 and obtained a large specific surface area. In addition, the ratio of Mn4+/(Mn3++Mn4+) decreased while the content of Fe2+ and surface chemical adsorption oxygen (Oα) increased, thus the oxidability of the catalyst was reduced. Meanwhile, tungsten doping enhanced the content and strength of Lewis acid sites on the surface of catalysts at high temperatures. Moreover, the adsorption of NH3 was enhanced, thus, NH3-SCR reaction was accelerated. The doping of WO3 inhibited the deep oxidation of NO2 to form nitrate species, reduced the content of by-product N2O produced by nitrate species reduction, and significantly improved the NH3-SCR activity and N2 selectivity of WO3-MnOx-Fe2O3 catalyst at experimental temperature.
Abstract: In order to improve the low temperature activity of Fe/Al-PILC catalysts for SCR of NO, copper doping was used for the modification. xCu-Fe/Al-PILC catalysts were prepared by ultrasonic impregnation technique and characterized by XRD, N2 adsorption-desorption, H2-TPR, UV-vis, XPS and Py-FTIR. The SCR of NO with C3H6 tests were carried out in a fixed bed reactor. The experimental results showed that the xCu-Fe/Al-PILC catalysts can effectively solve the problem of insufficient SCR activity of Fe/Al-PILC catalysts at low temperature and as well as improve the activity at medium and high temperature. High NO reduction efficiency, 80% and beyond could be achieved at a wide temperature range of 200-500℃ by the catalysts, among which 0.13Cu-Fe/Al-PILC exhibited 90% of the NO conversion at 250-500℃ and maximum NO reduction efficiency of 93% at 250℃. XRD and N2 adsorption-desorption results proved that the catalysts modified by copper provided more active sites and increased the reaction rate. The results of H2-TPR indicated that the doping of copper improved the catalyst's redox ability at lower temperature, while enhanced the catalyst's redox ability at medium and high temperature. UV-vis and XPS study showed that the doping of copper not only increased the higher oxidation state of iron but also produced more isolated Fe3+ which is the low-temperature active species. Py-FTIR test illustrated that Lewis acid and Brönsted acid existed simultaneously on the catalyst surface, and Lewis acid sites were the activity center of the SCR reaction.
Abstract: A novel ternary Au NPs/g-C3N4/BiOBr Z-scheme heterojunction composite was fabricated through hydrothermal and in-situ reduction method, and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet-visible diffuse reflection spectroscopy and photoluminescence emission spectroscopy. The photocatalytic activity was evaluated by the degradation of phenol under visible-light irradiation. It was found that Au NPs/g-C3N4/BiOBr showed enhanced photocatalytic activity, which is 3-fold higher than g-C3N4 and 2.5-fold higher than BiOBr. This could be attributed to the effective separation of photogenerated electron-hole pairs, narrowed band gap (2.10 eV) and surface plasmon resonance (SPR).
Abstract: H2WO4/GO was prepared by dipping method using tungstic acid and graphene oxide as raw materials. The morphology and structure of H2WO4/GO were characterized by XRD, FT-IR, SEM and BET. The ultrasonic-oxidation desulfurization of model oil containing DBT was carried out with H2WO4/GO as catalyst, H2O2 as oxidant agent and acetonitrile as extractant. Under the optimum conditions with 5 mL of model oil, 30% of tungstic acid loading(mass ratio), 0.02 g of catalyst, 1 mL of acetonitrile, H2O2/S mol ratio of 8, ultrasonic power of 150 W and at 50℃, the removal rate of DBT, 4, 6-DMDBT and BT can reach 96.6%, 81.2%, 72.8%, respectively. Besides, the recycling use of catalyst and the mechanism of ultrasonic-oxidation desulfurization were investigated.
Abstract: Graphite phase carbon nitride (g-C3N4) and metal oxide tungsten trioxide (WO3) heterojunction nanocomposites WO3/g-C3N4 were prepared by roasting from urea and ammonium tungstate. The physical and chemical properties of the catalysts were investigated by means of XRD, UV-vis, SEM, PL and XPS. The characterization indicated that WO3 and g-C3N4 interacted well in the catalysts, and electron transfer occurred between them, which ensured high oxidative desulfurization activity of WO3/g-C3N4. Supported catalyst WO3/g-C3N4 was prepared using WO3 as the support. Isopropyl peroxide was used as the oxidant to investigate the catalyst performance in oxidative desulfurization of the simulated oil. Under the reaction conditions of 80℃ and the content ratio of O/S at 3, a 72.79% of dibenzothiophene (DBT) conversion could be achieved after 180 min. It was fund that the superoxide free radicals (·O2-), electron (e-) and hydroxyl free radicals (·OH) promoted the reaction rate through free radical capture experiment and the reaction mechanism was proposed.
Abstract: The micron-sized plant fiber filaments were used as templates to obtain cylindrical macropores during the gamma alumina support preparation. The support was then used to prepare the NiMo/alunima diesel hydrodesulfurization catalyst. The prepared catalyst and alumina support were characterized by BET, XRD, SEM, Ruman and TEM. The characterization results showed that the plant fiber filaments in the catalyst constructed some straight holes, the NiMo active components on the catalyst support were highly dispersed and the active phase MoS2 stacked layers were mainly concentrated in 3-5 layers and the average length of MoS2 bars was 4.49 nm. The influence of plant fiber filament content on the performance of diesel hydrodesulfurization catalyst was studied and compared with conventional catalysts. The high-pressure micro-reverse evaluation results show that the developed NiMo diesel hydrotreating catalyst containing 3% (mass ratio) plant fiber filament has 5%-15% higher activity than the conventional NiMo catalyst.
Abstract: A real boiling point distillation apparatus was used to cut the fractions of Baishihu coal liquefied oil. The fraction below 170 ℃ was taken as the catalytic reforming feedstocks of hydrorefining. Meanwhile, the sulfur and nitrogen compounds in liquefied crude oil and refined oil were analyzed and characterized by GC-SCD and GC-NCD to study the transformation rule of sulfur and nitrogen compounds in hydrofining process. The results show that the sulfur compounds in liquefied crude oil are mainly thiophene compounds and mercaptan, which disappear after hydrorefining, and the removal rate of benzothiophenols is lower than that of thiophene compounds. Nitrogen-containing compounds in liquefied crude oil are mainly aniline compounds and indole compounds. After hydrorefining, all indole compounds are basically removed. Aniline and quinoline compounds belong to basic nitrogen-containing compounds, and are the main nitrogen-containing compounds remained in refined oil with a content of 1.61 mg/kg.
Abstract: The adsorption characteristics of As2O3(g) by CaO, Fe2O3, MgO, Al2O3, K2SO4 and Ca/Fe mixed adsorbents under the simulated flue gas atmosphere were studied by using a gas phase arsenic adsorption reaction experimental device at temperatures between 300 and 900℃. The results indicate that the adsorption ability of CaO is the strongest among the five single element adsorbents, while K2SO4 is the weakest. With the increase of temperature, the adsorption amount of CaO increases first, decreases slightly at 700℃, and then increases, while the adsorption amount of Fe2O3 increases first, and then decreases. However, the adsorption amount of MgO, Al2O3 and K2SO4 increases all the way. Compared with the calculated values of adsorption amounts of Ca/Fe mixed adsorbents in three proportions, the experimental values increase by 92% at least. The adsorption effect is the best when the ratio of CaO to Fe2O3 is 3:1. And the change of surface structure caused by sintering reaction after mixing is an important reason for the improvement of the adsorption effect.
Abstract: The reaction mechanism of thermal degradation of polystyrene has been studied theoretically using density functional theory B3LYP/6-311G(d) method. The main products of PS thermal degradation are styrene, followed by aromatic compounds such as toluene, α-methylstyrene, ethylbenzene and dimer. It is reported that the thermal degradation of PS mainly includes the homolytic reaction of carbon-carbon bond, β-cleavage reactions, hydrogen transfer reaction and free radical termination reaction. Base on the above reaction, the pathways was designed, and the theoretical calculation and analysis were carried out. Furthermore, the geometrical structure of all the reaction molecules was optimized for the reaction process and the reaction frequency was calculated, which were obtained the standard kinetic parameters and thermodynamic parameters of each thermal degradation path. The results of calculation show that the major formation mechanism of styrene is the chain-end β-cleavage reactions of free radicals, the producing of dimer mainly depends on the intermolecular 1, 3 hydrogen transfer reactions, α-methylstyrene is generated through intermolecular 1, 2 hydrogen transfer and β-cleavage reactions, the radicals of benzyl and phenethyl captured hydrogen atoms to form toluene and ethylbenzene, respectively. Kinetic analysis exhibit that the energy barrier for the formation of styrene was lower than that needed for the generating of other products, so styrene was the main thermal degradation product. This is consistent with the relevant experimental results.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
