前驱体干燥法对非晶态Ni-B/γ-Al_2O_3催化剂性能的影响

Amorphous Ni B/γ Al 2O 3 catalyst 1 is prepared with chemical reduction by KBH 4 solution after wetness impregnation and desiccation at 70 ℃ first and then at 110 ℃ for thorough water removal. Its higher catalytic activity than amorphous Ni B/γ Al 2O 3 catalyst 2, prepared by conventional one step desiccation procedure at 110 ℃, is identified in liquid phase benzene hydrogenation to cyclohexane. Both catalysts are characterized by XRD and SEM, Ni B/γ Al 2O 3 catalyst 1 has a higher active specific surface area and dispersion degree, which can be assigned to more effective distribution of nickel salt over the support during desiccation, thus resulting in its superior activity in benzene hydrogenation.

The nature of the deactivation of hydrothermally stable Ni/SiO2–Al2O3 catalyst in long-time aqueous phase hydrogenation of crude 1,4-butanediol

The deactivation of Ni/SiO2-Al2 O3 catalyst in hydrogenation of crude 1,4-butanediol was investigated.During the operation time of 2140 h,the catalyst showed slow activity decay.Characterization results,for four spent catalysts used at different time,indicated that the main reason of the catalyst deactivation was the deposition of carbonaceous species that covered the active Ni and blocked mesopores of the catalyst.The TPO and SEM measurements revealed that the carbonaceous species included both oligomeric and polymeric species with high C/H ratio and showed sheet.Such carbonaceous species might be eliminated through either direct H2 reduction or the combined oxidation-reduction methodologies.

Characterization and performance of Cu/ZnO/Al_2O_3 catalysts prepared via decomposition of M(Cu,Zn)-ammonia complexes under sub-atmospheric pressure for methanol synthesis from H_2 and CO_2

Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M（Cu,Zn）-ammonia complexes （DMAC） at various temperatures.The catalysts were characterized in detail,including X-ray diffraction,N2 adsorption-desorption,N2O chemisorption,temperature-programmed reduction and evolved gas analyses.The influences of DMAC temperature,reaction temperature and specific Cu surface area on catalytic performance are investigated.It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts.The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol （212 g/（Lcat·h）;T=513 K,p=3MPa,SV=12000 h-1）.

Carbon dioxide reforming of methane on monolithic Ni/Al_2O_3-based catalysts

Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal （Na, K） oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.

Bi-metallic catalysts of mesoporous Al_2O_3 supported on Fe, Ni and Mn for methane decomposition: Effect of activation temperature

Methane decomposition reaction has been studied at three different activation temperatures(500°C,800°C and950°C)over mesoporous alumina supported Ni–Fe and Mn–Fe based bimetallic catalysts.On co-impregnation of Ni on Fe/Al_2O_3the activity of the catalyst was retained even at the high activation temperature at 950°C and up to180 min.The Ni promotion enhanced the reducibility of Fe/Al_2O_3oxides showing higher catalytic activity with a hydrogen yield of 69%.The reactivity of bimetallic Mn and Fe over Al_2O_3catalyst decreased at 800°C and 950°C activation temperatures.Regeneration studies revealed that the catalyst could be effectively recycled up to 9times.The addition of O_2(1 ml,2 ml,4 ml)in the feed enhanced substantially CH_4conversion,the yield of hydrogen and the stability of the catalyst.

Syngas production by combined carbon dioxide reforming and partial oxidation of methane over Ni/α-Al_2O_3 catalysts

Ni/α-Al2O3 catalysts were found to be active in the temperature range 600 ～ 900℃ for both CO2 reforming and partial oxidation of methane.The effects of Ni loading,reaction temperature and feed gas ratio for the combination of CO2 reforming and partial oxidation of CH4 over Ni/α-Al2O3 were investigated.Catalysts of xwt%Ni/α-Al2O3（x=2.5,5,8 and 12） were prepared by wet impregnating the calcined support with a solution of nickel nitrate.XRD patterns and activity tests have verified that the 5wt%Ni/α-Al2O3 was the most active catalyst,as compared with the other prepared catalyst samples.An increase of the Ni loading to more than 5wt% led to a reduction in the Ni dispersion.In addition,by combining the endothermic carbon dioxide reforming reaction with the exothermic partial oxidation reaction,the loss of catalyst activity with time on stream was reduced with the amount of oxygen added to the feed.

Selective Hydrogenation of Butyne-1,4-diol to Butane-1,4-diol over Ni/Al_2O_3-SiO_2 Catalysts

Ni/Al_2O_3-SiO_2 catalysts were synthesized via one-step method employing SiO_2 as an additive for the selective hydrogenation of butyne-1,4-diol(B_3D) to butane-1,4-diol(B1D). The prepared catalysts were evaluated by a series of characterization techniques including BET, XRD, SEM, EDX-mapping, TEM, H_2-TPR, XPS, NH_3-TPD and Py-FTIR. Compared to Ni/Al_2O_3 catalyst, the SiO_2-doped samples exhibited better B_3D conversion. SiO_2 could help to form a strong interaction between NiO with the support, which inhibited Ni agglomeration at high temperature, improved the Ni dispersion, and enhanced the hydrogenation activity. B_1D selectivity was mainly influenced by the quantity of Lewis acid sites in addition to the Ni dispersion. The catalyst with a silica loading of 6.4% demonstrated an excellent selectivity of 75.18%(by 13% higher than the contrastive Ni/Al_2O_3 catalyst), which was attributed to the larger amount of Lewis acid sites and the moderate interaction between NiO with the support, which could facilitate the nickel dispersion on a preferable surface area of 176.3 m^2/g of support.

脉冲电沉积RE-Ni-W-B-PTFE-Al_2O_3复合镀层性能的研究

高性能复合镀层具有优良的耐磨、耐蚀性能,能满足工业生产对材料性能的要求。研究了脉冲电沉积RE Ni W B PTFE Al2O3 复合镀层的成分、形貌及性能。结果表明:脉冲电流及Al2O3 固体颗粒能明显提高RE Ni W B PTFE Al2O3 复合镀层中W和B的含量;与直流电沉积相比,脉冲电沉积RE Ni W B复合镀层的表面裂纹已明显减小,但裂纹仍存在,当Al2O3 耐磨颗粒及PTFE减摩微粒嵌入RE Ni W B复合镀层中以后,在SEM 400倍下观察,RE Ni W B PTFE Al2O3镀层已不存在裂纹, 而且镀液中Al2O3 颗粒含量越多,晶粒就越细;此外,研究表明,镀液中Al2O3 颗粒含量增加, RE Ni W B PTFE Al2O3 复合镀层镀态硬度增加,磨损率降低。

氮掺杂碳改性Ni/Al2O3催化剂的甲烷干重整反应性能研究

在甲烷干重整反应(DRM)中,常规浸渍法制备的Ni/Al2O3催化剂常因过多积炭导致催化剂失活,因此研究如何提高Ni/Al2O3催化剂的抗积炭能力具有重要意义。通过浸渍法和高温碳化法制备的氮掺杂碳表面修饰的Ni/Al2O3催化剂Ni/Al2O3@NC-3和Ni/Al2O3@NC-5(3和5分别代表多巴胺聚合时间为3 h和5 h)在DRM中表现出了较强的抗积炭性能。使用X射线衍射(XRD)、拉曼(Raman)光谱、X射线光电子能谱(XPS)、热重(TG)和扫描电镜(SEM)等表征手段对催化剂的结构和电性质进行了分析,并探讨了氮掺杂碳的引入对催化剂稳定性和抗积炭性能的影响。XPS结果表明,Ni/Al2O3@NC-3和Ni/Al2O3@NC-5催化剂中金属Ni与氮掺杂碳发生了电子相互作用,形成了催化惰性的Ni+物种,由此减缓了CH_(4)的裂解速率,进而有效地减少了积炭的产生。在经8 h活性测试后,Ni/Al2O3@NC-3催化剂的CH_(4)转化率和CO_(2)转化率分别维持在52.2%和62.3%,且反应后Ni/Al2O3@NC-3催化剂的积炭量仅为7%(质量分数,下同),远远低于Ni/Al2O3催化剂的积炭量(25%)。

EFFECT OF Ni CRYSTAL SIZE DISTRIBUTION ON THE ANTICOKING BEHAVIOR OF La-MODIFIED Ni/α-Al_2O_3 CATALYSTS

The crystal size distribution（CSD）was determined with small angle X-ray scattering technique.Theanticoking property of Ni-catalysts was investigated with the steam reforming of n-heptane in a TG-monitoredflow reactor.The results of this study show that the rate of coking on the supported Ni-catalysts depends main-ly on the percentage content of the large size fraction（25-70nm）of Ni-crystallites,and that the dispersion ofNi-crystallites and the anticoking property of the Ni/α-Al2O3 catalysts were promoted obviously by theLa2O3-modification method.The variation of the Ni-CSD and the anticoking property of the catalysts were fur-ther tested through different periods of hydrothermal treatment.It is found that the content of the largeNi-crystal size fraction and the coking rate pass correspondingly through a maximum.

Catalytic Hydrogenation Performance of Methyl Isobutyl Ketone over Ni/γ-Al_2O_3 Catalysts

Supported nickel-based catalysts were prepared by the incipient wetness impregnation method for the selective hydrogenation of methyl isobutyl ketone to methyl isobutyl carbinol in a fixed-bed reactor. The effects of the nickel source,Ni loading, calcination time, and calcination temperature on the hydrogenation performance were studied. The experimental results showed that the Ni/γ-Al_2O_3 catalyst demonstrated the highest catalytic performance under the preparation conditions by using nickel nitrate as the nickel source with a NiO loading of 20%, followed by calcination at 440°C for 5h. In addition,this catalyst showed the largest specific surface area, best crystal structure, highest active component content, smallest particle size, and uniform distribution of NiO on the surface of the carrier. The nickel-based catalyst prepared using the optimized conditions exhibited a 96.1% conversion of methyl isobutyl ketone, with a methyl isobutyl carbinol selectivity of 99.6%. The described procedure is very effective for the preparation of methyl isobutyl carbinol using methyl isobutyl ketone as the feedstock.

THE STUDY OF THE NON-STEADY KINETICS OF THE OXYDEHYDROGENATION OF ETHANE TO ETHYLENE OVER THE CATALYST OF Mo-V-Nb/Al_2O_3 BY THE TECHNIQUE OF TEMPERATURE PROGRAMMED TRANSIENT RESPONSE AND ELECTRIC CONDUCTIVITY

In this paper, instead of with the more expensive Fourier Transform Infrared Spectrometer(FTIR) a new technique of Temperature Programmed Transient Response(TP-TR) has been used with gas chromatography. Therefore, the TP-TR will be applied more widespreadly than ever before. With the technique of TP-TR and electric conductivity, the study is on the reaction mechanism and the adsorption behavior of the reactants and products to the present catalyst Mo-V-Nb/Al_2O_3 in the reaction from ethane through oxydehydrogenation to ethylene as the product. By Range-Kutta-Gill and Margarat methods, the kinetic parameters of the reaction elementary steps (i.e. rate constants, active energies and frequency factors) have been evaluated. The mathematical treatment coincides with the experimental results.

Methanation of syngas over coral reef-like Ni/Al_2O_3 catalysts

Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673Ni/Al2O3-573Ni/Al2O3- 473Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2（molar ratio）=1：3,593 K,atmospheric pressure and a GHSV of 2500 h-1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%.

Investigation of the characteristics and deactivation of catalytic active center of Cr-Al_2O_3 catalysts for isobutane dehydrogenation

Deactivation mechanism of Cr-Al2O3catalyst and the interaction of Cr-A1 in the dehydrogenation of isobutane, as well as the nature of the catalytic active center, were studied using XRD, SEM, XPS, H2-TPR, isobutane-TPR and TPO techniques. The results revealed that the deactivation of Cr-Al2O3 catalyst was mainly caused by carbon deposition on its surface. The Cr3＋ ion could not be reduced by hydrogen but could be reduced to Cr2＋ by hydrocarbons and monoxide carbon. The active center for isobutane dehydrogenation could be Cr2＋/Cr3＋ produced from Cr6＋ by the on line reduction of hydrocarbon and carbon monoxide. The binding energy of Al3＋ was strongly affected by the state of chromium cations in the catalysts.

Ethanol steam reforming over Ni-Cu/Al_2O_3-M_yO_z (M = Si, La, Mg,and Zn) catalysts

Ni-based catalysts doped with copper additives were studied on their role in ethanol steam reforming reaction. The effects of Cu content, support species involving Al2O3-SIO2, Al2O3-MgO, Al2O3-ZnO, and Al2O3-La2O3, on the catalytic performance were studied. Characterizations by TPR, XRD, NH3-TPD, XPS, and TGA indicated that catalysts 30Ni5Cu/Al2O3-MgO and 30Ni5Cu/Al2O3-ZnO have much higher H2 selectivity than 30Ni5Cu/Al2O3-SiO2, as well as good coke resistance. H2 selectivity for 30Ni5Cu/Al2O3-MgO catalyst was 73.3% at 450 ℃ and increased to 94.0% at 600℃, whereas for 30Ni5Cu/Al2O3-ZnO catalyst, the H2 selectivity was 63.6% at 450 ℃ and 95.2% at 600℃. TheseAl2O3-MgO and Al2O3-ZnO supported Ni-Cu bimetallic catalysts may have important applications in the production of hydrogen by ethanol steam reforming reactions.

Effect of Al_2O_3 Binder on the Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

A series of iron-based Fischer-Tropsch synthesis （FTS） catalysts incorporated with Al2O3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characterized by using N2 physical adsorption, temperature-programmed reduction/desorption （TPR/TPD） and MSssbauer effect spectroscopy （MES） methods. The characterization results indicated that the BET surface area increases with increasing Al2O3 content and passes through a maximum at the Al2O3/Fe ratio of 10/100 （weight basis）. After the point, it decreases with further increase in Al2O3 content. The incorporation of Al2O3 binder was found to weaken the surface basicity and suppress the reduction and carburization of iron-based catalysts probably due to the strong K-Al2O3 and Fe-Al2O3 interactions. Furthermore, the H2 adsorption ability of the catalysts is enhanced with increasing Al2O3 content. The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor （CSTR） under the reaction conditions of 260 ℃, 1.5 MPa, 1000 h^-1 and molar ratio of H2/CO 0.67 for 200 h. The results showed that the addition of small amounts of Al2O3 affects the activity of iron-based catalysts to a little extent. However, with further increase of Al2O3 content, the FTS activity and water gas shift reaction （WGS） activity are decreased severely. The addition of appropriate Al2O3 do not affect the product selectivity, but the catalysts incorporated with large amounts of Al2O3 have higher selectivity for light hydrocarbons and lower selectivity for heavy hydrocarbons.

Effects of Cerium Oxide on Ni/Al_2O_3 Catalysts for Decomposition of CH_4 and C_2H_4

Characteristics of carbon deposition of CH 4 and C 2H 4 decomposition over supported Ni and Ni Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal semiconductor interaction (MScI) in the Ni Ce catalyst, and the effect of MScI on the carbon deposition of CH 4 decomposition is opposite to that of C 2H 4. A novel model of carbon deposition of CH 4 or C 2H 4 decomposition was proposed.

Selective catalytic hydrogenation of naphthalene to tetralin over a NiMo/Al2O3 catalyst

The selective catalytic hydrogenation of naphthalene to high-value tetralin was systematically investigated.A series of Al2O3 catalysts containing different active metals(Co,Mo,Ni,W)were prepared by incipient wetness impregnation.The effects of different active metals forms(oxidation,reduction,sulfuration)and reaction conditions on naphthalene hydrogenation were investigated and the catalysts were characterized by XRD,XPS,BET,NH3-TPD and SEM.Especially,Ni-Mo/Al2O3 was first used in this reactive system.The results show that the oxidative4%Ni O-20%MoO3/Al2O3 is the best catalyst for the preparation of tetralin.The conversion of naphthalene and the selectivity of tetralin can reach 95.62%and 99.75%respectively at 200℃,8 h and 6 MPa.Compared with reduced and sulfureted 4%Ni O-20%MoO3/Al2O3 catalysts,oxidative 4%Ni O-20%MoO3/Al2O3 has a well dispersed and uniform monolayer of the active metals,larger pore volume and size,and larger total acidity.NiO-MoO3/Al2O3 has a synergistic effect between NiO activity and MoO3 selectivity.

Simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide over Al_2O_3-K/CAC catalyst at low temperature

In this work, a series of coal-based active carbon （CAC） catalysts loaded by A1203 were prepared by sol-gel method and used for the simulta- neous catalytic hydrolysis of carbonyl sulfide （COS） and carbon disulfide （CS2） at relatively low temperatures of 30-70 ℃. The influences of calcinations temperatures and operation conditions such as： reaction temperature, 02 concentration, gas hourly space velocity （GHSV） and relative humidity （RH） were also discussed respectively. The results showed that catalysts with 5.0 wt% A1203 calcined at 300 ℃ had supe- rior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 ℃, catalytic hydrolysis activity of COS could be enhanced but that of CS2 was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2 decrease. A small amount of 02 introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2.

Bonding mechanism of X10CrNi18-8 with Ni/Al_2O_3 composite ceramic by pressureless infiltration

An alloy steel/alumina composite was successfully fabricated by pressureless infiltration of X10CrNi18-8 steel melt on 30%(mass fraction) Ni-containing alumina based composite ceramic(Ni/Al2O3) at 1 600 ℃.The infiltration quality and interfacial bonding behavior were investigated by SEM,EDS,XRD and tensile tests.The results show that there is an obvious interfacial reaction layer between the alloying steel and the Ni/Al2O3 composite ceramic.The interfacial reactive products are(FexAly)3O4 intermetallic phase and(AlxCry)2O3 solid solution.The interfacial bonding strength is as high as about 67.5 MPa.The bonding mechanism of X10CrNi18-8 steel with the composite ceramic is that Ni inside the ceramic bodies dissolves into the alloy melt and transforms into liquid channels,consequently inducing the steel melt infiltrating and filling in the pores and the liquid channels.Moreover,the metallurgical bonding and interfacial reactive bonding also play a key role on the stability of the bonding interface.