整装式铝泡沫负载Pd催化剂Pd/AlOOH/Al-foam及其催化甲烷燃烧性能

以三维网络结构的铝泡沫板作为骨架基体和铝源,利用水热氧化法制备整装式拟薄水铝石(Al OOH/Al-foam)纳米阵列,随后通过丙酮辅助-初湿浸渍法,制备出整装式铝泡沫负载Pd催化剂Pd/Al OOH/Al-foam,用于低浓度甲烷催化燃烧反应。在制备条件优化过程中,发现催化剂性能受到纳米阵列的形貌特征、物相组成以及焙烧温度等因素的影响。其中,表面富含羟基的拟薄水铝石可促进Pd颗粒的均匀分散,也增强载体和Pd之间的相互作用,进而提高甲烷燃烧的低温活性。稳定性测试初期活性下降较快,主要原因是表层Al_2O_3纳米阵列载体和Pd纳米颗粒自身的不稳定性导致的Pd颗粒烧结。     

甲烷在Cr改性Pd/Al2O3催化剂上的催化燃烧性能

研究了Cr改性Pd/Al2O3催化剂上低浓度甲烷的催化燃烧反应,考察了载体Cr Al的制备方法和活性组分Pd的负载方法对催化剂催化活性的影响以及添加Ce对催化剂高温稳定性的影响。采用X射线衍射、程序升温还原等表征手段分析了催化剂结构和氧化还原性。结果表明,与采用沉淀法制备的载体P-Cr Al相比,采用浸渍法制备的载体I-Cr Al具有较高的比表面积和反应活性;用Na BH3对Pd负载过程进行还原处理能明显提高催化剂活性,其原因是还原过程加强了催化剂上Pd与载体Cr Al之间的作用,通过H2-TPR证明了其还原能力得到了增加;添加Ce缓解了Al2O3高温条件下的烧结,增强了催化剂的高温稳定性。     

LiLaNiO_x/γ-Al_2O_3催化剂上甲烷加压部分氧化制合成气

考察LiLaNiO_x/γ—Al_2O_3催化剂对甲烷加压[(0.2～1.0)MPa]部分氧化制合成气反应的催化性能。结果表明,LiLaNiO_x/γ—Al_2O_3催化剂具有优良的甲烷部分氧化催化性能,在850℃和1.0 MPa条件下,甲烷转化率和CO选择性分别达76.2%和82.5%。在100 h连续实验中,反应活性及选择性保持不变,显示出较高的催化稳定性。采用XRD、XPS和TG—DTA方法对反应前后催化剂的晶体结构、表面性能以及抗积炭性能进行表征,结果表明,LiLaNiO_x/γ-Al_2O_3催化剂具有较高的结构稳定性和抗积炭性能。     

Low temperature oxidation of methane over Pd/SnO2 catalyst

Catalytic activities of supported Pd were investigated for low temperature oxidation of methane. Pd/SnO₂ catalysts demonstrated excellent activity for methane oxidation in spite of their low surface area. The catalytic activity of Pd/SnO₂ was strongly affected by the preparation procedure. Impregnation of Pd on SnO₂ using aqueous solution of Pd(CH₃COO)₂ was most effective in enhancing the catalytic activity. The catalytic activity was also improved when well-crystallized SnO₂ was employed as a support material. TEM observations revealed that catalytic activity is strongly influenced by the dispersion state of Pd. For the active catalysts, strong interaction between Pd and SnO₂ support was observed in the adsorption of oxygen.     

SO42−/ZrO2 supported on γ‐Al2O3 as a catalyst for CO2 desorption from CO2‐loaded monoethanolamine solutions

In this work, the composite catalysts, SO₄²/ZrO₂/γ‐Al₂O₃ (SZA), with different ZrO₂ and γ‐Al₂O₃ mass ratios were prepared and used for the first time for the carbon dioxide (CO₂)‐loaded monoethanolamine (MEA) solvent regeneration process to reduce the heat duty. The regeneration characteristics with five catalysts (three SZA catalysts and two parent catalysts) of a 5 M MEA solution with an initial CO₂ loading of 0.5 mol CO₂/mol amine at 98°C were investigated in terms of CO₂ desorption performance and compared with those of a blank test. All the catalysts were characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption–desorption experiment, ammonia temperature programmed desorption, and pyridine‐adsorption infrared spectroscopy. The results indicate that the SZA catalysts exhibited superior catalytic activity to the parent catalysts. A possible catalytic mechanism for the CO₂ desorption process over SZA catalyst was proposed. The results reveal that SZA1/1, which possesses the highest joint value of Brφnsted acid sites (BASs) and mesopore surface area (MSA), presented the highest catalytic performance, decreasing the heat duty by 36.9% as compared to the catalyst‐free run. The SZA1/1 catalyst shows the best catalytic performance as compared with the reported catalyst for this purpose. Moreover, the SZA catalyst has advantages of low cost, good cyclic stability, easy regeneration and has no effect on the CO₂ absorption performance of MEA. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3988–4001, 2018     

Pd/Al2O3催化剂上低浓度CO氧化的研究

采用共沉淀法和浸渍法制备了2%Pd-Al2O3催化剂,在固定反应器中评价不同制备方法(共沉淀和浸渍)、助剂(1%K和1%Mg)、预处理方法(快速氧化和缓慢还原)、空速(726h-1、1638h-1和5274h-1)情况下2%Pd-Al2O3催化剂对CO氧化的催化活性。结果表明,共沉淀法制备的2%Pd50%Zr-Al2O3催化剂有较高的反应活性,该催化剂经缓慢还原预处理活化,在温度为70℃时就可以使低浓度的CO完全氧化。     

精C_5饱和加氢Pd/Al_2O_3催化剂的制备

研究负载在Al2O3载体上的Pd催化剂对精C5饱和加氢反应的性能。以工厂精C5为原料,考察载体焙烧温度、Pd负载量和催化剂制备工艺对催化剂性能的影响。结果表明,载体最佳焙烧温度为700℃,Pd最佳负载质量分数为0.3%,Pd最佳负载时间为4 h,催化剂最佳焙烧温度为500℃,催化剂最佳焙烧时间为4 h,以此条件制备的催化剂进行C5饱和加氢评价,加氢效率不低于94%。     

Ni/CaO‐Al2O3 bifunctional catalysts for sorption‐enhanced steam methane reforming

Ni/CaO‐Al₂O₃ bifunctional catalysts with different CaO/Al₂O₃ mass ratios were prepared by a sol–gel method and applied to the sorption‐enhanced steam methane reforming (SESMR) process. The catalysts consisted mainly of Ni, CaO and Ca₅Al₆O₁₄. The catalyst structure depended strongly on the CaO/Al₂O₃ mass ratio, which in turn affected the CO₂ capture capacity and the catalytic performance. The catalyst with a CaO/Al₂O₃ mass ratio of 6 or 8 possessed the highest surface area, the smallest Ni particle size, and the most uniform distribution of Ni, CaO, and Ca₅Al₆O₁₄. During 50 consecutive SESMR cycles at a steam/methane molar ratio of 2, the thermodynamic equilibrium was achieved using the catalyst with a CaO/Al₂O₃ mass ratio of 6, and H₂ concentration profiles for all the 50 cycles almost overlapped, indicating excellent activity and stability of the catalyst. Moreover, a high CO₂ capture capacity of 0.44 was maintained after 50 carbonation–calcination cycles, being almost equal to its initial capacity (0.45 ). © 2014 American Institute of Chemical Engineers AIChE J, 60: 3547–3556, 2014     

NO + H2 reaction on Pd/Al2O3 under lean conditions: kinetic study

This paper deals with the kinetics of the NO + H₂ + O₂ reactions on Pd/γ-Al₂O₃. Steady state rate measurements have been discussed in the light of previous mechanism proposals involving a dissociation step of molecular NO adsorbed species on Pd. In the absence of oxygen, the dissociation of NO_ads species is assisted by chemisorbed H atoms. However, different kinetic features have been observed in the presence of oxygen. Practically, the light-off curve of NO shifts towards higher temperature in the presence of O₂. In addition the H₂ + O₂ reaction extensively occurs in the temperature range of this study. Such tendencies have been explained by changes in the adsorptive properties of noble metals and also in the nature of elementary steps for the dissociation of NO. In the presence of a large extent of O₂, hydrogen coverage would sharply drop and would not further assist the dissociation of NO as in the absence of O₂.     

络合还原法制备的Pd/C催化剂对甲酸氧化的电催化性能

分别以硼氢化钠和乙二醇为还原剂,经络合还原法制备了炭载钯（Pd/C）催化剂。透射电镜（TEM）和X射线粉末衍射谱（XRD）结果表明,以乙二醇为还原剂制备的Pd/C催化剂中Pd粒子具有较小的粒径、均匀的粒径分布和较大的相对结晶度,Pd粒子的平均粒径和相对结晶度分别为4.2±2 nm和1.88。电化学测试结果显示,以乙二醇为还原剂制备的Pd/C催化剂具有较大的电化学活性面积,对甲酸氧化表现出较高的电催化活性和稳定性。     

Pd/Al2O3催化剂上CH4选择性还原NO的研究

考察了Pd/Al₂O₃、In/Al₂O₃和Co/Al₂O₃对甲烷选择性还原NO的催化活性。结果表明，采用浸渍法制备的Pd/Al₂O₃、In/Al₂O₃和Co/Al₂O₃三种催化剂，在有氧气氛下，用CH₄作还原剂催化还原NO时，Pd/Al₂O₃催化剂的活性最佳，热稳定性好，在550 ℃，用CH₄选择还原NO，Pd/Al₂O₃催化剂表现出较强的催化能力，NO的转化率达到100%。在高空速实验中，该催化剂亦表现出较高的活性，其活性顺序为Pd/Al₂O₃>In/Al₂O₃>Co/Al₂O₃。实验研究了助催化剂、氧含量以及空速对Pd/Al₂O₃催化剂活性的影响。     

Enhanced electrochemical oxidation of dye wastewater with Fe2O3 supported catalyst

Electrochemical oxidation of Acid Red 3R was investigated in the presence of Fe₂O₃/γ-Al₂O₃ as Fenton-like catalyst in the reactor. The results showed that the catalyst had catalytic activity in the electrochemical process. Under the optimal conditions, the decolorization efficiency reached 77.2% in 100 min. UV–vis spectrum and LC–MS analysis revealed that the dye molecule was firstly decomposed to aromatic intermediates, further degraded to ring opening products and finally mineralized. The azo dye degradation might be attributed to strong oxidant OH that produced from the synergetic effect of between Fe₂O₃/γ-Al₂O₃ catalyst and electrochemical system.     

甲烷催化燃烧用LaMn/Al_2O_3催化剂研究

为获得具有优良低温活性的甲烷燃烧用催化剂,采用稀土La作为助剂制备了系列Mn基催化剂,借助X射线衍射(XRD)、X射线光电子能谱(XPS)和程序升温还原(TPR)技术对催化剂的结构进行了表征,并评价了其对甲烷燃烧的低温催化性能。结果表明,La助剂的添加显著促进了活性组分MnO2的分散,使其更易于还原,且使Mn4+和晶格氧富集于催化剂表面,因而显著提高了催化剂对甲烷催化燃烧的低温活性。当La质量分数为5%时,催化活性最高,甲烷50%转化率对应的温度较未加助剂时降低了70℃,且完全转化的温度低至480℃。     

Solvent effects in the hydrodechlorination of 2,4‐dichlorophenol over Pd/Al2O3

Solvent effects in the liquid phase (0.1 MPa; 303 K) hydrodechlorination (HDC) of 2,4‐dichlorophenol have been established over Pd/Al₂O₃. In the absence of secondary reactions, catalyst deactivation, and transport limitations, a stepwise HDC yields 2‐chlorophenol and phenol, where product selectivity was insensitive to the nature of the solvent. In contrast, the initial HDC rates exhibited a marked dependence on the reaction medium and increased in the order: benzene < THF < n‐hexane < cyclohexane < alcohols < water. Higher rates result from the concomitant effect of an increase in the dielectric constant (ε) and a decrease in the molar volume ( $\overline {\nu}$ ) of the solvent, where the major (ca. 80%) contribution is due to ε. We attribute this response to the increased solvent capacity to stabilize the arenium intermediate at higher/lower ε/$\overline {\nu}$ , an effect that extends to reaction in water + organic combinations. We provide, for the first time, a reliable quantification of solvent effects that can be potentially applied to other catalytic hydrogenolysis systems. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Nano‐engineered nickel catalysts supported on 4‐channel α‐Al2O3 hollow fibers for dry reforming of methane

A nickel (Ni) nanoparticle catalyst, supported on 4‐channel α‐Al₂O₃ hollow fibers, was synthesized by atomic layer deposition (ALD). Highly dispersed Ni nanoparticles were successfully deposited on the outside surfaces and the inside porous structures of hollow fibers. The catalyst was employed to catalyze the dry reforming of methane (DRM) reaction and showed a methane reforming rate of 2040 Lh^?1gNi^?1 at 800°C. NiAl₂O₄ spinel was formed when Ni nanoparticles were deposited on alpha‐alumina substrates by ALD, which enhanced the Ni‐support interaction. Different cycles (two, five, and ten) of Al₂O₃ ALD films were applied on the Ni/hollow fiber catalysts to further improve the interaction between the Ni nanoparticles and the hollow fiber support. Both the catalyst activity and stability were improved with the deposition of Al₂O₃ ALD films. Among the Al₂O₃ ALD coated catalysts, the catalyst with five cycles of Al₂O₃ ALD showed the best performance. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2625–2631, 2018     

Highly stable Fe/γ‐Al2O3 catalyst for catalytic wet peroxide oxidation

BACKGROUND: A highly stable Fe/γ‐Al₂O₃ catalyst for catalytic wet peroxide oxidation has been studied using phenol as target pollutant. The catalyst was prepared by incipient wetness impregnation of γ‐Al₂O₃ with an aqueous solution of Fe(NO₃)₃· 9H₂O. The influence of pH, temperature, catalyst and H₂O₂ doses, as well as the initial phenol concentration has been analyzed. RESULTS: The reaction temperature and initial pH significantly affect both phenol conversion and total organic carbon removal. Working at 50 °C, an initial pH of 3, 100 mg L^?1 of phenol, a dose of H₂O₂ corresponding to the stoichiometric amount and 1250 mg L^?1 of catalyst, complete phenol conversion and a total organic carbon removal efficiency close to 80% were achieved. When the initial phenol concentration was increased to 1500 mg L^?1, a decreased efficiency in total organic carbon removal was observed with increased leaching of iron that can be related to a higher concentration of oxalic acid, as by‐product from catalytic wet peroxide oxidation of phenol. CONCLUSION: A laboratory synthesized γ‐Al₂O₃ supported Fe has shown potential application in catalytic wet peroxide oxidation of phenolic wastewaters. The catalyst showed remarkable stability in long‐term continuous experiments with limited Fe leaching, < 3% of the initial loading. Copyright © 2010 Society of Chemical Industry