Fe_2O_3／ZrO_2催化剂上一氧化碳加氢反应制低碳烯烃──I．催化剂反应性能及反应过程中铁物相的变化

用浸渍法制得一系列不同铁负载量的Ｆｅ２Ｏ３／ＺｒＯ２催化剂，应用催化反应评价结合穆斯堡尔谱对催化剂的ＣＯ加氢反应性能、催化剂活性相结构及催化剂铁物种在合成气反应过程中的物相变化进行了研究．结果表明，铁负载量的大小对于Ｆｅ２Ｏ３／ＺｒＯ２催化剂的Ｆ－Ｔ反应催化性能有很大影响，铁负载量适当时，Ｆｅ２Ｏ３／ＺｒＯ２催化剂铁锆间适当的强相互作用使得催化剂在保持较高催化活性的同时高选择性地生成低碳烯烃，产物分布偏离Ｓｃｈｕｌｚ－Ｆｌｏｒｙ分布规律．     

硅对铁基费-托合成催化剂的影响

用共沉淀法制备了一系列不同硅含量的铁基催化剂,采用N2吸附和原位X射线衍射对催化剂进行了表征,在固定床反应器中考察了催化剂的费-托合成反应活性、选择性和稳定性.结果表明,含硅的催化剂具有较大的比表面积和较小的平均孔径,在CO还原及费-托合成反应中生成的碳化铁物种的稳定性比不含硅的催化剂高.在费-托合成反应中,不含硅的催化剂具有较高的初始活性,但易失活;含硅的催化剂具有较低的初始活性,但稳定性较高.Fe7C3是活性最高的碳化铁物种.随着硅含量的增加,催化剂的费-托合成反应更易生成低碳数产物.     

Correlating Fe source with Fe-N-C active site construction:Guidance for rational design of high-performance ORR catalyst

Pyrolyzed Fe-N_X/C materials derived from Fe-doped ZIF-8 are recently emerged as promising alternatives to noble metal platinum-based catalysts towards oxygen reduction reaction(ORR) and elucidating the dependacne of Fe source on the active site structure and final ORR performance is highly desirbale for further development of these materials. Here, we designed and synthesized a series of Fe-N-C catalysts using ZIF-8 and various iron salts(Fe(acac)_3, FeCl_3, Fe(NO_3)_3) as precusors. We found that the iron precursors,mainly the molecular size, hydrolysis extent, do play a major role in determining the final morphology of Fe, namely forming the Fe-Nx coordination or Fe_3C nanoparticles, as well as the site density, therefore,significantly affecting the ORR activity. Among the three iron sources, Fe(acac)_3 is most advantageous to the preferential formation of single-atom Fe-Nx active sites and the derived catalyst demonstrated best ORR performance.     

Solid-liquid Metastable Equilibria in Quaternary System （NaCl＋Na2CO3＋Na2SO4＋H2O） at 273.15 K

The metastable phase equilibria of the quaternary system NaCl+Na2CO3+Na2SO4+H2O were studied at 273.15 K. The salts' solubilities, densities and pH values of the equilibrated solution in this system were determined. According to the experimental data, the metastable equilibrium phase diagram, the diagram of density vs. composition and pH vs. composition diagram were plotted. The phase diagram consists of five univariant curves, four crystallization fields and two invariant points. The four crystallization fields correspond to sodium carbonate decahydrate (Na2CO3·10H2O), sodium sulfate decahydrate(Na2SO4·10H2O), sodium chloride(NaCl) and burkeite(2Na2SO4· Na2CO3), respectively. The crystallization field of sodium sulfate decahydrate(Na2SO4·10H2O) is the largest, which indicates that sodium sulfate is easy to saturate and crystallize from solution at 273.15 K.     

Fe-Mn/Al2O3催化剂低温 NH3选择性催化还原 NO的性能

本文制备了一系列 Fe-Mn/Al2O3催化剂,并在固定床上考察了其 NH3低温选择性催化还原 NO的性能.首先考察了不同 Fe负载量制备的催化剂的脱硝性能,优选出最佳的 Fe负载量;在此基础上,研究了 Mn负载量对催化剂脱硝效率的影响;最后,对优选催化剂的抗 H2O和抗 SO2性能进行了实验研究;同时,对催化剂由于 SO2所造成的失活机制进行了考察.采用 N2吸附-脱附、X射线衍射、透射电镜、能量弥散 X射线谱、程序升温还原、程序升温脱附、X射线光电子能谱、热重和傅里叶变换红外光谱等方法对催化剂进行了表征.结果表明,最佳的 Fe和 Mn负载量均为8%,所制的8Fe-8Mn/Al2O3催化剂在150°C的脱硝效率可达近99%;同时,在整个低温测试区间(90–210°C)的脱硝效率均超过了92.6%. Fe在催化剂表面主要以 Fe3+形态存在,而 Mn主要包括 Mn4+和 Mn3+; Mn的添加提高了 Fe在催化剂表面的积累,促进了催化剂比表面积增大和活性物种分散,改善了催化剂氧化还原性能和对 NH3的吸附能力.催化剂的高活性主要是由于其具有较大的比表面积、高度分散的活性物种、增加的还原特性和表面酸性、较低的结合能、较高的 Mn4+/Mn3+和增强的表面吸附氧.此外,8Fe-8Mn/Al2O3的催化性能受 H2O和 SO2影响较小,抗 H2O和 SO2能力较强.同时,反应温度对催化剂的抗硫性有重要影响,在较低的反应温度下,催化剂抗硫性更好; SO2造成催化剂活性降低主要是由于催化剂表面硫酸盐物种的生成.一方面,表面硫酸铵盐的生成造成催化剂孔道堵塞和比表面积降低,减少了反应中的气固接触从而导致活性降低;另一方面,催化剂表面的活性物种被硫酸化,造成反应中的有效活性位减少,从而降低了催化剂活性.     

助剂钾对二氧化碳加氢反应活性及产物分布的影响

报导助剂Ｋ对Ａｌ２Ｏ３，ＴｉＯ２，ＺｒＯ２担载Ｆｅ催化剂，用于ＣＯ２加氢合成Ｃ２＋烃的催化活性及产物分布的影响。与不含Ｋ的催化剂相比，Ｋ的存在导致Ｆｅ／Ｋ－Ａｌ２Ｏ３的催化活性及Ｃ＾２＋烃选择性明显提高，但使Ｆｅ／Ｋ－ＴｉＯ２的催化活性及Ｃ２＋烃选择性显著下降，而对Ｆｅ／Ｋ－ＺｒＯ２，这种影响并不显著。Ｋ的明显有利于低碳烯烃的生存。     

用23Na和27Al固体核磁共振研究Na+在γ-Al2O3上的吸附状态

The adsorption of Na~+ on γ-alumina surface at four coverages of Na_2CO_3 (5%, 10%, 15%, and 20% wt/wt) was characterized by solid-state ~(23)Na and ~(27)Al NMR spectroscopy. The experimental results suggest that two distinct adsorbed species are present on alumina surface: surface species and surface salts. At lower coverages of Na_2CO_3 (5% and 10%), a surface species is predominant, in which the Na~+ cations are associated with the oxygen atoms of γ-alumina. With increasing the loading level to 15%, a second adsorbed species begins to appear which is attributed to the surface salt, Na_2CO_3, deposited on the solid surface. Further adsorption of Na_2CO_3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. ~1H-~(27)Al CP/MAS experiments give the evidence that some Na~+ cations in the form of surface species are coordinated with the Br~(‥)onsted acid sites of γ-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of Na_2CO_3/γ-Al_2O_3 catalyst.     

氯苯类化合物在盐水溶液中的活度系数

在25.00±0.01 ℃下用紫外、可见分光光度法分别测定了氯苯(CB)、m-二氯苯(mDCB)、p-二氯苯(pDCB)、1,2,4-三氯苯(TCB)在NaCl、KCl、Na_2CO_3、K_2SO_4、CaCl_2盐水溶液及氯苯在Et_4NBr水溶液中的话度系数, 得出盐效应常数. 除Et_4NBr对氯苯呈盐溶作用, 其余均为盐析作用. 盐析次序大致为K_2SO_4>Na_2CO_3>CaCl_2>NaCl>KCl. 计算了盐效应常数的各种理论值, 与实验值进行比较, 进一步证实了改进后的内压力理论值更接近实际. 同时也讨论了这些数据在环保中的应用.     

Thermodynamic Analysis and Experimental Investigation into Nonflame Combustion Technology（NFCT） with Thermal Cyclic Carrier

The utilization of fossil fuels causes serious negative impacts on the environment and human life. To mitigate greenhouse gases and other pollutants, a novel combustion process-the nonflame combustion technology with a thermal cyclic carrier of molten salt is introduced. In this technology, a whole combustion is divided into two steps, i.e. , the section of producing oxide and the section of combustion. In the first step, oxygen is separated from air, and pure N2 is simultaneously formed which is easily recovered. In the other step, the fuels react with lattice oxygen in the oxides formed in the first step, and at the same time, thermal energy, CO2 and H2O vapor are produced. It is noted that the CO2 is easily separated from water vapor and ultimately captured. Theoretically, there are no environmental-unfriendly gases such as CO2, NOx and SO2 discharged in the whole combustion process. Some metal oxides scattered into molten salts play the roles of oxygen carriers in the combustion system, and they can constantly charge and discharge oxygen element from air to fuels during the combustion process. A nonflame combustion system with Li2CO3 K2CO3 Na2SO4 as the molten salt system, CH4 as the fuel and CuO as the catalyst was experimentally investigated. The experimental resuits show that the combustion process proceeded as it was theoretically analyzed, and CO2 with a high volume fraction of 77.0M--95.0M and N2 with a high volume fraction of 91.9%-99.3% were obtained. The high concentration of CO2 is favorable for capturing and storing subsequently. Therefore, the potential of reducing CO2 emissions of this nonflame combustion technology is huge.     

钙钛矿型La1+X/2Sr1-x/2Co1-xCuxO3催化CO氧化活性与表征

The catalytic activity and the reactive properties of perovskite-type oxides catalysts La(1+x/2)Sr(1-x/2)Co1-xCuxO3 for CO oxidation reaction were investigated. Results showed that the catalytic activity for CO oxidation reached to a maximum when x＝0.4. The temperature for complete CO oxidation under atmospheric and experimental conditions was 168℃. According to the stoicheometry of catalyst, all catalysts were oxygen defect compounds. The active oxygen species on this catalyst was the adsorbed oxygen which was adsorbed on the surface lattice oxygen defect. It was also found that Co4+ existed in the catalysts and the sufrace active oxygen species was caused by the Co4+. It was concluded that CO oxidation reaction on this catalyst was carried out by the valence change between Co3+ and Co4+ which was adjusted by the adsorbed oxygen.