One-step synthesis of dimethyl ether from syngas on ordered mesoporous copper incorporated alumina

Ordered mesoporous copper incorporated Al_2O_3(Cu/Al_2O_3) with high Cu dispersion were prepared by a facile solution combustion synthesis method using aluminum nitrate and copper nitrate as oxidants and urea as fuel. It is a facile and green route to synthesize catalysts for dimethyl ether directly from syngas. Cu/Al_2O_3 catalysts were characterized by XRD, N_2 adsorption–desorption, SEM-EDS, and H_2-TPR.The results indicate that the catalysts obtain an ordered mesoporous structure and copper is homogenously dispersed. The mesoporous Cu/Al_2O_3 catalysts were utilized as bifunctional catalysts in syngas to dimethyl ether reaction(STD). The copper content affects the catalytic performance in STD reaction. The CO conversion and DME selectivity of Cu/Al_2O_3 with 15% copper molar ratio achieve 52.9% and 66.1%,respectively. Moreover, the mesoporous Cu/Al_2O_3 catalysts show excellent stability in STD reaction.     

Al_2O_3负载Cu,Fe或Ni掺杂氧化钼催化乙苯氧化脱氢(英文)

Molybdenum-based catalysts supported on Al_2O_3 doped with Ni, Cu, or Fe oxide were synthesized and used in ethylbenzene dehydrogenation to produce styrene. The molybdenum oxide was supported using an unconventional route that combined the polymeric precursor method(Pechini) and wet impregnation on commercial alumina. The samples were characterized by X-ray diffraction(XRD), N_2 adsorption-desorption isotherms, temperature-programmed reduction of H_2(H_2-TPR),and thermogravimetric(TG) analysis. XRD results showed that the added metals were well dispersed on the alumina support. The addition of the metal oxide(Ni, Cu, or Fe) of 2 wt% by wet impregnation did not affect the texture of the support. TPR results indicated a synergistic effect between the dopant and molybdenum oxide. The catalytic tests showed ethylbenzene conversion of 28%–53% and styrene selectivity of 94%–97%, indicating that the addition of the dopant improved the catalytic performance, which was related to the redox mechanism. Molybdenum oxides play a fundamental role in the oxidative dehydrogenation of ethylbenzene to styrene by its redox and acid–base properties. The sample containing Cu showed an atypical result with increasing conversion during the reaction, which was due to metal reduction. The Ni-containing solid exhibited the highest amount of carbon deposited, shown by TG analysis after the catalytic test, which explained its lower catalytic stability and selectivity.     

Catalytic activity and crystal structure modification of Pd/γ-Al_2O_3–TiO_2 catalysts with different Al_2O_3 contents

Pd/γ-Al_2O_3–TiO_2 catalysts containing various compositions of titania and alumina were prepared by sol–gel and wet-impregnation methods in attempt to study the particle size, nature of phases, morphology and structure of the composite samples. The ethanol oxidation experiments, N_2 adsorption–desorption,FTIR, XRD and XPS were conducted, and the effects of Al_2O_3 content on the surface area, phase transformation and structural properties of TiO_2 were investigated. The optimal value of ethanol conversion appeared on Pd/Al(0.05)–Ti and Pd/Al(0.90)–Ti catalysts irrespective of the ethanol oxidation temperature, and we call this as a double peaks phenomenon of catalytic activity. The XRD results reveal that the phase composition and crystallite size of the mixed oxides depend on Al_2O_3/TiO_2 ratio and calcination temperature. Al_2O_3 can effectively prevent the agglomeration of TiO_2 and this can be ascribed to the formation of Al–O–Ti chemical bonds in Al_2O_3–TiO_2 crystals. Binding energy and Pd surface concentration of the catalysts were modified apparently, which may also lead to catalyst activity changes.     

Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

The Ru/Al_2O_3 catalysts modified with metal oxide(K_2O and La_2O_3)were prepared via incipient wetness impregnation method from RuCl_3·nH_2O mixed with nitrate loading on Al_2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX)from the hydrogen-rich gas streams produced by reforming gas,and the performances of catalysts were investigated by XRD and TPR.The results showed that the activity temperature of the modified catalysts Ru-K_2O/Al_2O3 and Ru-La_2O_3/Al_2O_3 were lowered approximately 30℃compared with pure Ru/Al_2O_3,and the activity temperature range was widened.The conversion of CO on Ru-K_2O/Al_2O_3 and Ru-La_2O_3/Al_2O_3 was above 99% at 140-160℃,suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La_2O_3/Al_2O_3 was higher than that of Ru-K_2O/Al_2O_3 in the active temperature range. Slight methanation reaction was detected at 220℃and above.     

Modeling and optimization of methane dry reforming over Ni-Cu/Al_2O_3 catalyst using Box-Behnken design

In this work the effects of the contents of nickel(5,7.5,10 wt%)and copper(0,1,2 wt%)and reaction temperature(650,700,750°C)on the catalytic performance of Ni–Cu/Al_2O_3catalyst in methane dry reforming were evaluated using Box–Behnken design in order to optimize methane conversion,H_2/CO ratio and the catalyst deactivation.Different catalysts were prepared by co-impregnation method and characterized by XRD,BET,H_2-TPR,FESEM and TG/DTA analyses.The results revealed that copper addition improved the catalyst reducibility.Promoted catalyst with low amounts of Cu gave higher activity and stability with high resistance to coke deposition and agglomeration of active phase especially during the reaction.However catalysts with high amounts of Cu were less active and rather deactivated due to the active sites sintering as well as Ni covering by Cu-enriched phase.The optimal conditions were determined by desirability function approach as 10 wt%of Ni,0.83 wt%of Cu at 750°C.CH_4conversion of95.1%,H_2/CO ratio of 1 and deactivation of 1.4%were obtained experimentally under optimum conditions,which were in close agreement with the values predicted by the developed model.     

Carbon dioxide reforming of methane over mesoporous nickel aluminate/γ-alumina composites

A series of x NiAl_2O_4/γ-Al_2O_3 composites with various Ni contents have been prepared via one-step partial hydrolysis of metal nitrate salts in the absence of surfactants and used for carbon dioxide reforming of methane. The characterization results demonstrated that the Ni Al_2O_4/γ-Al_2O_3 materials possessed mesoporous structures of uniform pore sizes; and the Ni~(2+) ions were completely reacted with alumina to Ni Al_2O_4 spinel in the matrices using N2 sorption, XRD, TEM, and XPS. The Ni Al_2O_4/γ-Al_2O_3 materials exhibited excellent catalytic properties and superior long-term stability for carbon dioxide reforming of methane. The effects of Ni content on the intrinsic activities and the amounts of coke disposition of the x NiAl_2O_4/γ-Al_2O_3 catalysts were discussed in detail for the carbon dioxide reforming of methane. The results revealed that the Ni particle sizes did not affect the intrinsic activity of metallic Ni, but smaller Ni particles could reduce the rate of coke deposition.     

Complete Oxidation of Methane over Palladium Supported on Alumina Modified with Calcium,Lanthanum,and Cerium Ions

The activity and thermal stability of Pd/Al_2O_3 and Pd/(Al_2O_3 MO_x)(M=Ca,La,Ce) palladium catalysts in the reaction of complete oxidation of methane are presented in this study.The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide.Then they were impregnated with palladium nitrate solution.The catalysts with unmodified alumina had a high surface area.The activity and thermal stability of the alumina- supported catalyst was also very high.The introduction of calcium,lanthanum,or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method.These modifiers decreased the activity of palladium catalysts,and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al_2O_3.The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.     

Effects of ZrO2 on the Performance of CuO-ZnO-Al2O3/HZSM-5 Catalyst for Dimethyl Ether Synthesis from CO2 Hydrogenation

A series of composite catalysts were prepared by the wet mixing method,and the mass ratio of CuO-ZnO-Al_2O_3-ZrO_2 component to HZSM-5 zeolite(molar ratio of SiO_2 to Al_2O_3 being 25)was 2:1. The CuO-ZnO-Al_2O_3-ZrO_2(CuO/ZnO/Al_2O_3=3/6/1 by weight)component was prepared by a modified‘two-step’co-precipitation inethod.The effects of ZrO_2 on the performance of CuO-ZnO-Al_2O_3/HZSM-5 catalyst for dimethyl ether synthesis from CO_2 hydrogenation were investigated.It was found that ZrO_2 improved the properties of CuO-ZnO-Al_2O_3/HZSM-5 as a structural promoter.     

Ni-Co/Mg-Al catalyst derived from hydrotalcite-like compound prepared by plasma for dry reforming of methane

Ni-Co bimetallic catalysts with different Ni/Co content were derived from cold plasma jet decomposition and reduction of hydrotalcite-like compounds containing Ni,Co,Mg and Al,and their catalytic performance was investigated with dry reforming of methane.Experimental results showed that the hydrotalcite-like precursors could be completely decomposed and partly reduced by cold plasma jet,and the Nicontained catalysts exhibited much higher activity than the catalyst without Ni.Especially,the catalyst with Ni/Co ratio of 8/2 achieved not only the highest conversions of 80.3%and 69.3%for CH4 and CO2,respectively,but also the best stability in 100 h testing.The catalysts were characterized by XRD,XPS,TEM and N2 adsorption techniques,and the results showed that the better performance of the 8Ni2Co bimetallic catalyst was attributed to its higher metal dispersion,smaller metal particle size,as well as the interaction effect between Ni and Co,which were brought by the special catalyst preparation method.     

EFFECTS OF RARE EARTH OXIDES ON PERFORMANCES OF Ni/Al_2O_3 CATALYSTS FOR METHANE STEAM REFORMING REACTION

The Catalytic performances for methane steam reforming reaction ofNi/Al_2O_3(commercial), Ni/Al_2O_3 (developed surface )and Ni/Al_2O_3-R_xO_y (R israre earth oxide) Catalysts were investigated by means of X-ray diffraction,TG, SEM/ X-ray analysis, pulse gas chromatography,BET and Mercuryporsiniter techniques. The distribution of rear earth oxides on the supports,themetal-support (additives) interaction and the influence of rare earth oxideadditives on the dispersion of active components,catulytic activities,variationof nickel crystallites size,CO chemisorption,formation of NiAl_2O_4 as well asthe reducibility of the catalysts were examined.The presence of rare earthoxides in the Ni/Al_2O_3 (developed surface) results in great improvement ofstubility through suppressing the growth of Ni crystallites,the oxidation of themetallic Ni and the formation of NiAl_2O_4. The effect of heavy rare earth oxidesis more distinct than that of the light ones.Strong metal support interaction(SMSI) exists in Ni/Al_2O_3- R     

耐硫甲烷化中H2S浓度对MoO3/Al2O3和CoO-MoO3/Al2O3催化剂的影响

在0 到12 mL·L^-1 (体积分数φ=0.00%-1.20%) 范围内考察了不同H₂S 浓度对25% (质量分数, w)MoO₃/Al₂O₃和5% (w) CoO-25%MoO₃/Al₂O₃催化剂甲烷化性能的影响. 结果表明, 5%CoO-25%MoO₃/Al₂O₃的甲烷化活性随H₂S浓度的增加单调上升, 而25%MoO₃/Al₂O₃对H₂S浓度并不敏感. 对比这两种催化剂发现, 只有在H₂S浓度高于0.40% (φ) 时, 在25%MoO₃/Al₂O₃中添加Co助剂才会有促进作用; H₂S浓度低于0.40% (φ)时, Co助剂会抑制25%MoO₃/Al₂O₃催化剂的甲烷化活性. 分别对反应前后的催化剂表征发现, H₂S浓度的改变不会对两种催化剂的物理结构产生明显的影响, 而是通过影响催化剂表面的金属硫化物活性位来影响催化剂的甲烷化性能. 耐硫甲烷化反应体系中较高的硫含量下Co助剂才表现出对25%MoO₃/Al₂O₃催化剂的促进作用. 该研究明确了在MoO₃/Al₂O₃催化剂中添加Co助剂的硫化氢浓度范围, 为工业上选择合适的催化剂提供了依据.     

二甲基二硫醚对Ni/Al_2O_3催化剂加氢性能的影响

考察了二甲基二硫醚(CH3SSCH3)对Ni/Al2O3催化剂上苯、环己烯和苯乙烯加氢活性的影响,并采用BET、XRD、H2-TPR、XPS、SEM和EA等手段对催化剂进行表征。实验结果表明,在CH3SSCH3存在下,Ni/Al2O3催化剂对苯和环己烯加氢迅速失活,且环己烯加氢对CH3SSCH3的耐硫性要略强于苯加氢,而苯乙烯中共轭烯烃的加氢转化率则维持100%长时间不变。CH3SSCH3的影响顺序为芳环单烯烃共轭烯烃。此外,通过设计实验研究了CH3SSCH3对催化剂的毒化机理,发现CH3SSCH3分子首先吸附在催化剂的表面,并发生氢解生成甲烷随尾气逸出,故CH3SSCH3分子中碳对催化剂的失活影响较小,而留下的硫原子则与镍活性组分发生相互作用,毒化催化剂。     

气相色谱法研究配位化合物的热稳定性(Ⅶ)——Ni(Ⅱ)、Co(Ⅱ)草酸配合物的热分解及产物的催化性能

镍(Ⅱ)、钴(Ⅱ)草酸配合物在氢气中热分解时产生CO₂和CO,并发生加氢催化反应.CoC₃O₄和NiC₂O₄的分解产物CO₂加氢活性很快降低;K₂O等具有分散金属的作用。CoC₂O₄/Al₂O₃和K₂^{[Co(C₂O₄)₂]}/Al₂O₃体系具有Al₂(C₃O₄)₃的分解特征。C₂O₄^2-在Al₂O₃表面能形成表面配合物,在Al₂O₃表面Co(Ⅱ)的还原较为困难。     

Improving Catalytic Stability and Coke Resistance of Ni/Al2O3 Catalysts with Ce Promoter for Relatively Low Temperature Dry Reforming of Methane Reaction

Aseries of Ni catalysts supported on alumina with different Ce contents(1.0%-6.0%, mass fraction) was prepared by the impregnation method and used for dry reforming of methane(DRM) at a relatively low temperature of 650 ^oC. The promotion effect of Ce with different loading amounts on the physicochemical properties of the catalysts was systematically characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD), N₂ adsorption-desorption, thermo elemental IRIS Intrepid inductively coupled plasma atomic emission spectrometer (ICP-AES), UV-visible diffuse reflectance spectroscopy(UV-Vis DRS), Fourier transformation infrared(FTIR) spectra, H₂-temperature programmed reduction(H₂-TPR) analysis, H₂-temperature programmed desorption(H₂-TPD), and the X-ray photoelectron spectroscopy(XPS) techniques. The results indicate that all the catalysts mainly exist in the NiAl₂O₄ phase after being calcined at 750 ^oC with small Ni particle sizes due to the strong metal-support interaction derived from the reduction of the NiAl₂O₄ phase. The Ce-promoted catalysts show better catalytic performance as well as the resistance against sintering of Ni particles and deposition of carbon compared to the Ni/Al₂O₃ catalyst. The Ni-6Ce/Al₂O₃ exhibits the best catalytic stability and coke resistance among the four catalysts studied, which is due to its small Ni nanoparticles sizes, excellent reducibility as well as high amount of active oxygen species. In a 400 h stability test for DRM reaction at 650 ^oC, Ni-6Ce/Al₂O₃ exhibits less coke deposition and small growth of Ni nanoparticles. This work provides a simple way to preparing the Ni-Ce/Al₂O₃ catalyst with enhanced catalytic performance in DRM. The Ni-6Ce/Al₂O₃ catalyst has great potential for industrial application due to its anti-sintering ability and resistance to carbon deposition.     

Ni/MgO/Al2O3催化剂上以1-甲基萘为模型化合物高温焦炉煤气焦油的催化转化

采用共浸渍薄水铝石(AlOOH)方法制备了一系列Ni/MgO/Al₂O₃催化剂, 并采用N₂气吸附及Ｘ射线衍射等手段进行了表征. 选择1-甲基萘作为焦油模型化合物, 研究了该催化剂催化转化具有较低水蒸气/碳摩尔比(n_H2O/n_C) 的高温焦炉煤气(COG)中焦油催化反应性能. 考察了催化剂中MgO含量及反应条件等对催化剂性能的影响. 实验结果表明, 在775 ℃和n_H2O/n_C=0.7条件下, MgO改性的Ni/MgO/Al₂O₃催化剂对1-甲基萘催化转化为小分子气体反应具有较好的催化活性和稳定性; 热重分析表明, MgO的加入能显著提高催化剂的抗积炭能力. 在Ni/MgO/Al₂O₃催化剂上, 反应气中高浓度H₂S气体(0.25%, 体积分数)能够促进焦油催化转化为小分子气体, 这可能是由于H₂S在Ni表面的可逆吸附形成更适合于重整反应的活性位, 同时抑制了烷烃裂解吸附形成的碳在金属中的溶解、扩散并最终形成积炭过程.     

钼改性页硅酸镍催化剂催化顺酐加氢性能

通过蒸氨法合成了一系列钼改性的页硅酸镍催化剂, 考察了钼含量对催化剂结构及其催化顺酐液相加氢性能的影响. 采用氮气物理吸附-脱附、 X射线衍射(XRD)、 傅里叶变换红外光谱(FTIR)、 透射电子显微镜(TEM)、 氢气程序升温还原(H₂-TPR)、 氨气程序升温脱附(NH₃-TPD)、 吡啶吸附红外光谱(Py-IR)和原位X射线光子能谱(XPS)等手段对催化剂的结构和形貌等进行了表征. 结果表明, 助剂Mo的引入对催化剂结构形貌及其催化性能影响显著. Mo的引入提高了活性金属Ni的还原度, 增加了催化剂表面金属Ni⁰的数量, 金属Ni在还原过程产生氢溢流, 溢流氢将部分MoO₃还原为具有酸性的MoO_x物种, 由于金属Ni⁰与具有Lewis酸(L酸)特性的MoO_x及Ni^σ+的协同效应, 显著提高了催化剂对顺酐C≡C和C≡O的加氢活性. 当Mo含量(质量分数)为3%时, 其催化活性最高, 在160 ℃和5 MPa H₂气条件下, 反应3 h顺酐的转化率为100%, 产物γ-丁内酯的选择性为27%.     

碱土Sr对Co/Al2O3催化剂甲烷部分氧化反应的影响

以γ-Al₂O₃为载体,采用共浸渍法制备了Sr-Co/Al₂O₃系列催化剂,研究了助剂Sr对Co/Al₂O₃催化剂上甲烷部分氧化(POM)制合成气反应的影响,并利用N₂物理吸附、X射线衍射、H₂-程序升温还原和热重等技术对催化剂的理化性质进行了表征。结果表明,未添加助剂的Co/Al₂O₃和800℃焙烧的Sr-Co/Al₂O₃催化剂在POM反应初期催化活性很低,然而,当添加Sr的质量分数高于2%时,催化剂表现出很好的催化活性和稳定性。焙烧后的新鲜催化剂上主要存在两类Co物种,一类是与载体相互作用较弱、易被H₂还原为单质的Co₃O₄;另一类是与载体相互作用较强、难还原、无催化活性的CoAl₂O₄尖晶石。在焙烧过程中,Sr易形成Sr₄Al₁₄O₂₅,从而削弱Co与Al₂O₃之间的相互作用,能在一定程度上抑制CoAl₂O₄物种的形成,提高催化剂的稳定性和活性。未添加Sr的Co/Al₂O₃在反应时易发生物相改变生成尖晶石,导致催化剂迅速失活;但当焙烧温度达到800℃时,添加有限量的Sr还是无法阻止CoAl₂O₄的产生。     

Co/Fe/Al2O3/cordierite催化C3H6选择性还原NO的实验研究

采用溶胶凝胶法和浸渍法制备了负载于蜂窝陶瓷上的Co/Fe/Al₂O₃/cordierite催化剂,在陶瓷管流动反应器上对其催化C₃H₆选择性还原NO的性能进行了测试。结果表明,该催化剂表现出最优脱硝性能,在模拟烟气条件下,当反应温度为550 ℃时可实现97%的脱硝效率。Co的引入可显著增强Fe/Al₂O₃/cordierite催化剂抗SO₂和H₂O的能力。在模拟烟气中同时引入0.02% SO₂和3% H₂O后,1.5Co/Fe/Al₂O₃/cordierite的脱硝性能受影响甚微,当反应温度高于500 ℃时1.5Co/Fe/Al₂O₃/cordierite催化C₃H₆还原NO的效率均可达到90%以上;相比之下,未经Co修饰的催化剂Fe/Al₂O₃/cordierite脱硝性能受到了严重的抑制,在整个反应温度区间（200-700 ℃）内,其催化C₃H₆还原NO的效率最高不足50%。XRD和SEM表征结果表明,经过适量的Co修饰后的1.5Co/Fe/Al₂O₃/cordierite表面变得更疏松,且形成了以钴铁和钴铝双金属氧化物为主要成分的球状晶粒。H₂-TPR结果表明,相比于Fe/Al₂O₃/cordierite,1.5Co/Fe/Al₂O₃/cordierite有更好的低温还原性能。Py-FTIR结果表明,Co的引入可使催化剂表面的Lewis酸明显增加,且生成了Brønsted酸。N₂吸附-脱附表征结果表明,Co可增大催化剂的比表面积。     

铝源对Ni/Al2 O3催化剂结构及其CO2-CH4重整性能的影响

以三种不同铝源采用溶液燃烧法制备了系列Ni/Al_2O_3催化剂,通过XRD、H_2-TPR、NH_3-TPD、N_2吸附-脱附、TGDTG和TPH等分析方法对反应前后催化剂进行了表征,研究了铝源对Ni/Al_2O_3催化剂结构、表面性质及其CO_2-CH_4重整性能的影响。结果表明,以Al(NO_3)_3·9H_2O为铝源制备的NiNO-AlNO催化剂比表面积较大,达102 m~2/g;高温还原峰面积大,峰型更为弥散;且载体Al_2_O_3具有一定的结晶性。而以Al_2(SO_4)_3·18H_2O和AlCl_3·6H_2O为铝源制备的NiNO-AlSO和NiNO-AlCl催化剂,其载体以无定型Al_2O_3存在,活性组分Ni晶粒粒径大、分散性差,还原峰面积较小,与载体的相互作用较弱。其中,由于硫酸铝较为稳定,需要在更高温度下才能转化为Al_2O_3,且所制备NiNO-AlSO催化剂中残留有含硫物质,使得其表面酸性较强。评价结果显示,NiNO-AlNO催化剂活性较高,稳定性好,CH4转化率为31.21%,CO_2转化率为48.97%。积炭分析结果发现,NiNO-AlNO催化剂表面积炭量最少,沉积炭主要以无定型态存在,具有良好的抗积炭性能。     

Ru-Ni/Al2O3催化马来酸二甲酯加氢性能研究

以Al₂O₃为载体,RuCl₃·xH₂O及Ni（NO₃）₂·6H₂O为活性组分前驱体,采用吸附-沉淀法制备系列Ru-Ni/Al₂O₃催化剂,以马来酸二甲酯（DMS）催化加氢为探针反应,考察了活化条件和Ni的添加量对催化剂性能的影响。随Ni负载量的升高,Ru-Ni/Al₂O₃催化剂活性呈现先升高后降低的趋势,在Ni：Ru的原子比为6：1时（催化剂Ru₁Ni₆/Al）催化活性最高。催化剂Ru₁Ni₆/Al在氢气中200 ℃直接还原后的平均转化率与氢气中400 ℃还原后的平均转化率接近,达到了单组分Ru/Al催化剂的1.5倍以上。XPS、XRD、H₂-TPR数据表明,Ru与Ni之间发生了较强的相互作用,Ni的加入促进了金属Ru在载体上的分散,提高了催化活性。