姜 俊 李 鋼 孔令浩(大連理工大學(xué)化工學(xué)院,精細(xì)化工國(guó)家重點(diǎn)實(shí)驗(yàn)室,遼寧大連116024)

金屬有機(jī)骨架材料負(fù)載鎳納米顆粒催化硝基苯加氫

姜 俊 李 鋼*孔令浩
(大連理工大學(xué)化工學(xué)院,精細(xì)化工國(guó)家重點(diǎn)實(shí)驗(yàn)室,遼寧大連116024)

以MIL-53(Al)、MIL-96(Al)和MIL-120(Al)(MIL:Material Institute of Lavorisier)三種金屬有機(jī)骨架材料為載體,采用浸漬法制備了負(fù)載廉價(jià)金屬鎳納米顆粒的催化劑.將其用于催化硝基苯加氫合成苯胺反應(yīng),發(fā)現(xiàn)以MIL-53(Al)為載體制得的催化劑表現(xiàn)出優(yōu)異的催化性能.采用不同的鎳前驅(qū)體,如硝酸鎳、醋酸鎳、乙二胺合鎳,制備了一系列Ni/MIL-53(Al)催化劑.通過(guò)X射線衍射、傅里葉變換紅外光譜、電感耦合等離子體、N2物理吸附、H2程序升溫還原、透射電鏡等技術(shù)對(duì)其進(jìn)行了表征,研究了鎳前驅(qū)體對(duì)金屬-載體相互作用、鎳顆粒尺寸以及分散程度的影響.結(jié)果表明:以乙二胺合鎳為鎳前驅(qū)體制得的催化劑具有金屬-載體相互作用適中、鎳納米顆粒更小(4-5 nm)和分布更均勻的特點(diǎn),在硝基苯加氫反應(yīng)中表現(xiàn)出優(yōu)異的催化性能,硝基苯轉(zhuǎn)化率達(dá)到100%.回收重復(fù)使用5次后,此催化劑仍保持催化活性,硝基苯轉(zhuǎn)化率達(dá)92%.

金屬有機(jī)骨架材料;鎳;載體;前驅(qū)體;硝基苯加氫

?Editorial office ofActa Physico-Chimica Sinica

1 Introduction

In recent years,metal-organic frameworks(MOFs)have been explored as new hosts of various metal nanoparticles in the field of the catalysis.Compared with the traditional supports,MOFs can exhibit large specific surface areas,high porosities,adjustable pore size,chemical and structural diversity and act as hosts for variety of guest molecules.1,2Owing to their low thermal stabilities (200-500°C),MOFs were usually used as supports to incorporate noble metal nanoparticles as active sites such as Pd/MOFs,3,4Au/ MOFs,5,6Ru/MOFs,7and Pt/MOFs.8While,the area of catalysts Ni/MOFs,which using low-cost metal as active sites and MOFs as supports,is still in its infancy.9-12

The porous solids MIL-53(Al),MIL-96(Al),and MIL-120(Al) have the similar chemical compositions,which use aluminum as metal node and aromatic carboxylic acids as organic links.Aluminum is an attractive inorganic component for the construction of MOFs since its salts are non-toxic and commercially available at low-cost.Furthermore,most of the reportedAl-MOFs materials exhibit remarkable thermal and chemical stabilities,which are superior to chromium-,iron-,or zirconium-MOFs.13,14Since thermal and chemical stabilities are extremely important to most catalysis processes,these materials are especially adaptive to act as catalyst supports.

The catalytic properties of supported metal catalysts are influenced by the supports,but the nature of the metal precursors has also an important effect on the interaction between metal particles and supports,size of the nanoparticles,and distribution of metal particles.Hou et al.15reported that the Ni/SiO2catalysts using[Ni(en)3]2+(en:ethanediamine)and[Ni(EDTA)]2-(EDTA: ethylene diamine tetraacetic acid)as precursors possessed smaller sized nickel particles,which were more active and stable for methane reforming reaction with CO2and O2in a fluidized-bed reactor.Wang and Lu16had prepared Ni/γ-Al2O3catalysts with different nickel precursors and found that catalysts based on nickel nitrate exhibited higher catalytic activity than the other two catalysts derived from nickel chloride and nickel acetylacetonate. Meanwhile,they also found that organic precursor-derived catalysts possessed higher activity of preventing carbon deposition than the inorganic precursor-derived catalyst.However,the effect of using different nickel precursors on MOF supports,especially using organometallic complexes as precursors,has been rarely studied.

Hydrogenation of nitrobenzene is well known to be of significant importance in industrial process.17,18The product,aniline,is a basic chemical raw material and an important intermediate for the medicine,pesticides,dyes,and rubber process with a great demand.19Up to date,hydrogenation of nitrobenzene is usually catalyzed by Raney Ni20or noble metal catalysts such as Pt,21Pd,22and Rh.23Commercially the hydrogenation process is operated at the temperature of 150-250°C and pressure of 0.5-3.0 MPa. However,high cost,corrosion,and pollution are the problems that present commercial process has to face with.So exploring a highly effective and environmental friendly catalyst has attracted more attentions.

Herein,we report the loading of nickel nanoparticles using MIL-53(Al),MIL-96(Al),and MIL-120(Al)as supports.Aseries of Ni/MIL-53(Al)catalysts were prepared using three different nickel precursors(nickel nitrate,nickel acetate,and nickel ethanediamine).Their performance in the hydrogenation of nitrobenzene to aniline had been studied.The purpose of this study is to identify the support and precursor that lead to the more moderate metal-support interaction,smaller nanoparticles,higher nickel distribution,and more excellent catalytic activity.

2 Experimental

2.1 Catalyst preparation

The MIL-n(n=53,96,120)were synthesized and activated according to the literature.24-26Before impregnation,MIL-n(n=53, 96,120)were pretreated in a vacuum oven at 150°C for 12 h. Then,Ni/MIL-n(n=53,96,120)containing 4.0%(w)of nickel were prepared by a wetness impregnation method using nickel nitrate Ni(NO3)2·6H2O(98.0%,Tianjin Damao Chemical Co., Ltd.)as a nickel precursor.The samples were stirred at room temperature for 12 h,then dried,calcined,and reduced.The catalysts were denoted as Ni-n-NI(n=53,96,120),where NI indicates the precursor nickel nitrate.

The Ni/MIL-53(Al)catalysts were also prepared using nickel acetate Ni(CH3COO)2·4H2O(98.0%,Tianjin Damao Chemical Co.,Ltd.),and nickel ethanediamine[Ni(en)3]2+as nickel precursors.[Ni(en)3]2+was prepared in our laboratory.Ni(NO3)2·6H2O was dissolved in an aqueous solution,and subsequently ethanediamine(99.0%,Sinopharm Chemical Reagent Co.,Ltd.)was added into the solution with the molar ratio 1:3.Then,1 mol·L-1HNO3was added into the mixed solution to get a nickel ethanediamine solution with a pH value of 6.5.MIL-53(Al)was impregnated in the aqueous solution of each aforementioned nickel precursor.The catalysts prepared by using nickel acetate and nickel ethanediamine were denoted as Ni-53-AC and Ni-53-EN, respectively.

As-obtained samples using nickel nitrate and nickel ethanediamine as precursors were calcined at 300°C for 2 h.However, the sample using nickel acetate as precursor was calcined at 400°C for 2 h.The calcination process was as follows:the samples were calcined in air from room temperature to 150°C and held at 150°C for 1 h,then heated from 150 to 250°C and held at 250°C for 1 h,at last heated from 250 to 300°C(nickel nitrate and nickel ethanediamine)or 400°C(nickel acetate)and held at 300 or 400°C for 2 h.The temperature programing was always at a rate of 5°C· min-1.The five kinds of samples were reduced by pure hydrogen gas at a flow rate of 30 mL·min-1at 300°C(nickel nitrate and nickel ethanediamine)or 400°C(nickel acetate)for 2 h just before catalytic evaluation.

2.2 Catalyst characterization

Powder X-ray diffraction(XRD)patterns were recorded using Rigaku D/Max 2400 diffractometer employing Cu Kαradiation. Fourier transform infrared(FTIR)spectra of samples were re-corded on a Bruker EQUINOX55 infrared spectrometer,using the KBr pellet technique.The nickel contents of the samples were determined quantitatively by inductively coupled plasma(ICP)on Leeman Plasma-Spec-II instrument.N2physical adsorption-desorption isotherms were measured at-196°C using a Quantachrome autosorb physical adsorption apparatus.The samples were outgassed in vacuum at 150°C before measurement.The specific surface area and pore volume were calculated by the Brunauer-Emmett-Teller(BET)method based on the adsorption data and Dubinin-Raduskevitch(DR)adsorption model,respectively.H2-temperature-programmed reduction(H2-TPR)experiments were carried out in a quartz tube of the TPR apparatus.50 mg of samples were pretreated at 300°C for 2 h with a gas flow of N2at the rate of 30 mL·min-1.After cooling the samples to room temperature,the samples were heated from room temperature to 700°C at a heating rate of 10°C·min-1with a gas mixture of 10% (volume fraction)H2in N2at the rate of 30 mL·min-1.The amount of H2uptake during the reduction was detected by gas chromatograph-thermal conductivity detector(GC-TCD,Techcomp, GC-7890T).The Ni nanoparticle size and morphology of the catalysts were investigated by using a transmission electron microscope(TEM,FEI Company Tecnai G220 S-Twin)operated at 200 kV.The samples were first suspended in ethanol,dispersed ultrasonically and supported on lacey-Formvar carbon on a 200 mesh Cu grid before TEM images recorded.Mean nickel particle size(d)was calculated according to equation(1)

where nirepresents the number of particles with diameter di.

2.3 Catalytic reactions

Typically,the hydrogenation of nitrobenzene was carried out in a 100 mL stainless steel autoclave.0.5 mL of nitrobenzene was dissolved in 20 mLethanol(solvent),and 50 mg solid catalyst was added into the reactor.The autoclave was charged with 2.0 MPa hydrogen,stirred and heated to 110°C and kept on reacting for 4 h.Then,the reactor was cooled down to room temperature.The products were diluted with ethanol and transferred to a 50 mL volumetric flask totally.The sample was analyzed byAgilent GC-6890N(HP-5 capillary column,Flame Ionization Detector).The conversion was calculated on the basis of the initial and final amounts of nitrobenzene and the selectivity was determined as the ratio of the yield of aniline to the total yield of products.

3 Results and discussion

3.1 Characteristics and catalytic performance of Ni/MIL-n(n=53,96,120)

The XRD patterns of MIL-n(n=53,96,120)(Fig.1)are consistent with those in the literature,24-26and the sharp peaks clearly indicate that the materials are well crystalline.Although the crystallinity decreases,the framework of MIL-53(Al)is maintained after the loading of Ni.But it is obvious that the patterns of the supports in the catalysts Ni-96-NI and Ni-120-NI present the different diffraction peaks,indicating that the frameworks of MIL-96(Al)and MIL-120(Al)have been destroyed after loading of Ni. This phenomenon can be attributed to the poor thermal stability of MIL-96(Al)and MIL-120(Al)during the process of calcination and reduction.25,26The reflections corresponding to crystalline Ni phases are also detected in all three catalysts Ni-n-NI(n=53,96, 120),which indicates that nickel particles are successfully loaded. Noticeably,nickel peaks of Ni-53-NI are weak and broad compared to the other two catalysts,indicating smaller nickel particle size and higher nickel dispersion.The strong and sharp diffraction peaks of Ni phases on the support MIL-96(Al)and MIL-120(Al) could be attributed to the agglomeration of nickel particles on the supports with partial disruption.Fig.2 shows the TEM images of Ni/MIL-n(n=53,96,120)samples.The average Ni particle size of Ni-53-NI is about 6-7 nm,and that of Ni-120-NI increases to about 10-11 nm.While the agglomeration of nickel particles is observed when using MIL-96(Al)as support.The TEM results also show that Ni-53-NI possesses the highly dispersive Ni particles.

Fig.1 Powder XRD patterns of(a)MIL-53(Al),Ni-53-NI;(b)MIL-96(Al),Ni-96-NI;and(c)MIL-120(Al),Ni-120-NI

The textural properties of the three supports and the corresponding catalysts are given in Table 1.MIL-53(Al)presents the higher values of both internal surface area and pore volume compared to the other two samples,which could prevent nickel species from separating out from the channels or aggregate on the external surface.Furthermore,smallest nickel nanoparticle size and most uniform distribution could be obtained on MIL-53(Al) owing to its large external surface area.

Catalytic performance of Ni/MIL-n(n=53,96,120)was studied in the hydrogenation of nitrobenzene to aniline.Aniline is the main product and there are also a small amount of interme-diate product N-hydroxy aniline and other by-products.Table 2 summarizes the conversion of nitrobenzene and the selectivity to aniline.It can be observed that the catalytic performance is dependent on the support used.Ni-53-NI exhibits the best catalytic performance with 100%conversion of nitrobenzene and above 96%aniline selectivity,while Ni-96-NI and Ni-120-NI present only 75.5%and 66.5%conversion of nitrobenzene,respectively. The better catalytic performance of Ni-53-NI than the other two catalysts may be attributed to the smaller size and higher dispersion of Ni particles.Then MIL-53(Al)is selected as the optimal support to prepare the catalysts using different Ni precursors.

Fig.2 TEM images of Ni-53-NI(a),Ni-96-NI(b),and Ni-120-NI(c)

3.2 Characteristics of Ni/MIL-53 using different Ni precursors

The powder XRD patterns of MIL-53(Al)and Ni/MIL-53(Al) with three different precursors are showed in Fig.3.Different from MIL-96(Al)and MIL-120(Al),MIL-53(Al)belongs to the class of flexible networks,and the performance of large breathing can affect the XRD patterns distinctly.24In the case of the samples Ni-53-EN and Ni-53-AC,the main diffraction peaks of MIL-53(Al) markedly change.New peaks are observed at 9.1°,15.3°,and 26.6°(short dash line).The original peaks at 9.6°and 12.9°(solid line)are ascribed to the main diffraction peaks of large pore framework configurations of MIL-53(Al),while the new peaks at 9.1°,15.3°,and 26.6°are ascribed to the main diffraction peaks of narrow pore framework configurations.27The two versions of MIL-53(Al)structure have the same chemical composition and only differ in their pore size.28The average pore sizes of the three catalysts are shown in Table 1.We can observe that the decreases of the average pore size of the samples are in consistent with the XRD patterns.Similar changes in peak positions and relative intensities of MIL-53(Al)are also reported in other cases.29-32The Ni phase diffraction peaks of Ni-53-EN and Ni-53-NI are weak and broad,indicating that relatively small size and high dispersive nickel phases occurr on MIL-53(Al)support.On the other hand, the strong and sharp diffraction peaks of Ni-53-AC indicate larger nickel particles and lower nickel distribution.16Thus,the different nickel precursors markedly influence the sizes of Ni particles.

Table 2 Catalytic performance of Ni/MIL-n(n=53,96,120)

Fig.3 Powder XRD patterns of MIL-53(Al),Ni-53-NI, Ni-53-EN,and Ni-53-AC

The FTIR spectra(Fig.4)of MIL-53(Al)clearly show the bands at 1579 and 1503 cm-1corresponding to the asymmetric stretching of the―CO2group,whereas bands at 1445 and 1414 cm-1corresponding to the symmetric stretching of the―CO2group.The absence of an absorption band at around 1700 cm-1indicates that the free BDC acid molecules encapsulated within the pores areexpelled by a solvent extraction method.29The FTIR spectrum of MIL-53(Al)matches well with the literature.24No particular change has been observed between MIL-53(Al)and three kinds of the catalysts,assuming that the frameworks of MOF keep intact in the process of Ni loading.

Table 1 Textural properties of the three supports and the corresponding catalysts

Fig.4 FTIR spectra of MIL-53(Al),Ni-53-NI,Ni-53-EN, and Ni-53-AC

H2-TPR experiments are carried out to investigate the reducibility,nickel particle distribution,and metal-support interaction. As shown in Fig.5,no H2consumption peak appears under 600°C for MIL-53(Al),indicating that the support does not interfere with the H2consumption.Thus,we can have a full understanding about the reduction characteristics of all the three catalysts.For catalyst Ni-53-EN,there is just a single peak with its maximum center at about 500°C.Similar maximum is detected in catalyst Ni-53-NI, whereas there are two other shoulder peaks at about 400 and 550°C, which indicates the different interactions between nickel oxide particles and the support.Both Ni-53-EN and Ni-53-NI possessing the relatively low reduction temperature reveal that nickelsupport interactions are not strong.The H2-TPR profile of the catalyst Ni-53-AC shows a broad peak at about 550°C,with a small peak at 330°C,indicating that there are two kinds of nickel species existing on the surface of the catalyst.The small peak at low temperature coincides with the reduction of bulk NiO particles,33while the H2consumption peak at higher temperature originates from the reduction of small NiO particles that have a stronger interaction with the support.It is clear that the growth of Ni particle size is inevitable at above 500°C calcination and reduction temperature which uses other supports that have been reported.15,16However,lower reduction temperature can be adopted using MIL-53(Al)as the support,especially when using nickel nitrate and nickel ethanediamine as precursors.Thus the smaller nickel particles and more uniform distribution can be obtained on MIL-53(Al).

Fig.5 H2-TPR profiles of MIL-53(Al),Ni-53-EN, Ni-53-NI,and Ni-53-AC

Table 3 Textural properties of the samples

The textural properties of the samples are summarized in Table 3.It is observed that BET surface area and pore volume of the samples obviously decrease compared to the supports.This phenomenon is attributed to the blockage of pores by nickel particles and the partial disruption of the supports.Moreover,it is clear that in the catalysts prepared from different precursors, different particle sizes of Ni are obtained(calculated by the Sherrer-Warren equation from Ni(111)reflection of XRD patterns and determined by TEM images,as commented below)indicating that nickel particle size depends on the nickel precursors strongly.

Fig.6 shows the morphologies and sizes of Ni particles in Ni-53-NI,Ni-53-EN,and Ni-53-AC.Highly dispersive Ni particles with the particle size concentrated at 4-5 nm are detected in catalyst Ni-53-EN(Fig.6(a,b)),which indicates that Ni particles are mainly dispersed on external surface of MIL-53(Al)since the pore size of this MOF is only 0.8 nm.Similar particle sizes of 4-5 nm are detected in catalyst Ni-NI(Fig.6(c,d)).Whereas there are also some larger particles of 6-7 nm,indicating that catalyst Ni-53-NI possesses a broad metal particle size distribution.The broad distribution can be attributed to the different interactions between nickel species and support MIL-53(Al),which is demonstrated by H2-TPR profiles.Furthermore,catalyst Ni-53-AC has larger Ni particle size and broader distribution range compared with Ni-53-EN and Ni-53-NI.The detected nickel particle size is concentrated at 8-14 nm.This phenomenon can be attributed to the following two reasons.(i)The selected calcination and reduction temperatures are 400°C,which are higher than those of Ni-53-EN and Ni-53-NI,owing to the difficulty of decomposition of nickel acetate at low temperature.34,35Thus,nickel particles tend to grow large and aggregate at high temperature.(ii)Different interactionsbetween nickel species and the support result in a broad metal particle distribution.The bulk NiO with weak interaction with MIL-53(Al)transforms into the large nickel particles and the nickel species with strong interaction can form small nickel particles.While strong interaction results in high reduction temperature and the metal particles also easily aggregate.Thus,a moderate metal-support interaction is very important.Herein smaller nickel particles and higher distribution are detected for Ni-53-NI and Ni-53-EN.The order of nickel particle sizes of four samples is Ni-53-EN＜Ni-53-NI＜Ni-53-AC,and it is the same as the order obtained from XRD.

Fig.6 TEM images and corresponding Ni particle size distribution higtograms(insets)of Ni-53-EN(a,b), Ni-53-NI(c,d),and Ni-53-AC(e,f)

3.3 Catalytic performance of Ni/MIL-53 using different precursors

Table 4 summarizes the performance in the hydrogenation of nitrobenzene of the Ni/MIL-53(Al)catalysts using different precursors.It is found that the nickel precursors have a great effect on the catalytic performance of Ni/MIL-53(Al).Ni-53-EN and Ni-53-NI present much higher activity than Ni-53-AC.In order to get more information about the performance of the series of Ni/MIL-53(Al)catalysts,various process parameters were further studied. It can be observed that Ni-53-EN still shows high activity at lower hydrogen pressure and temperature.This is a successful example to prepare metal supported catalyst with uniform distribution of active components using chelating ligands such as en,citrate,and EDTA.The moderate metal-support interaction in Ni-53-EN facilitates the decrease of calcination and reduction temperature to obtain highly dispersive nickel nanoparticles.Due to the smaller nickel nanoparticle size and more uniformdistribution,Ni-53-EN possesses the best catalytic performance among these catalysts.

Table 4 Catalytic performance of Ni/MIL-53(Al) with different precursors

Fig.7 Recyclability of catalyst Ni-53-EN in hydrogenation of nitrobenzene to aniline

Fig.8 Powder XRD patterns of Ni-53-EN and recovered Ni-53-EN

3.4 Recycles of the Ni-53-EN

As well known,the recyclability is a very important character for practical solid catalyst.It is especially vital to MOFs supported catalysts for the medium coordinate bond strength and organic framework walls.In this work,the recyclability of Ni-53-EN in hydrogenation of nitrobenzene was examined.Fig.7 shows that the catalyst retains the catalytic activity even after five recycleswith the conversion of nitrobenzene at about 92.0%.The decrease of the conversion might be due to the decrease of the crystallinity of MIL-53(Al)and the leaching of Ni species during the recycling reactions and washing treatments.The nickel content of the recovered Ni-53-EN catalyst is 3.35%(w)detected by ICP,which is a little lower than that in the fresh catalyst.The XRD patterns of the fresh and recovered catalyst are shown in Fig.8.Even though the crystallinity of MIL-53(Al)in recovered catalyst decreases after five cycles,there are no signs of decomposition of MOF and the catalyst still maintains a high catalytic activity.

4 Conclusions

In summary,the catalysts of nickel nanoparticles supported on MOFs were prepared using three kinds of Al-MOFs as supports and different nickel precursors.It is demonstrated that the framework of MIL-53(Al)is maintained after the loading of Ni and the catalyst exhibits higher activity in the hydrogenation of nitrobenzene.Nickel precursors definitely have a great influence on the size of nickel particles and their distribution.Smaller Ni particles and higher distribution are obtained for the catalyst Ni-53-EN using nickel ethanediamine as nickel precursor.Ni-53-EN presents the excellent performance and outstanding recyclability in the hydrogenation of nitrobenzene to aniline,which can be attributed to the high stability of MIL-53(Al)support,small size of nickel nanoparticles,and high nickel distribution.This work highlights the influence of the supports and nickel precursors on Ni/MOF catalysts.It might bring new opportunities in the researches of low-cost metal supported catalysts.

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勘誤

李慶洲,李玉惠,李亞娟,劉又年.石墨烯/硫復(fù)合正極材料的一步水熱法制備與電化學(xué)性能.物理化學(xué)學(xué)報(bào),2014,30(8),1474-1480.文中引言部分最后一段中“Zhou等21指出在高溫高壓水熱環(huán)境下,臨界狀態(tài)的水中H+具有還原性能,氧化石墨烯被還原生成石墨烯,同時(shí),加強(qiáng)了新生態(tài)硫分子與石墨烯表面基團(tuán)的相互作用,起到固定硫的作用.”這句話改為:“Zhou等21指出在高溫高壓水熱環(huán)境下,過(guò)熱水可以促進(jìn)H+催化氧化石墨烯表面含氧官能團(tuán)的脫水反應(yīng),從而使氧化石墨烯轉(zhuǎn)化為石墨烯.在一步水熱法中,氧化石墨烯的還原和硫的生成反應(yīng)同時(shí)進(jìn)行.這有利于加強(qiáng)新生態(tài)硫分子與石墨烯表面基團(tuán)的相互作用.”.特此更正!

Corrigendum

LI Qing-Zhou,LI Yu-Hui,LI Ya-Juan,LIU You-Nian.One-Step Hydrothermal Preparation and Electrochemical Performance of Graphene/Sulfur Cathode Composites.Acta Phys.-Chim.Sin.2014,30(8),1474-1480.“Zhouet al.21pointed out under hydrothermal condition,H+acted as reductant in critical state water and graphene oxide was reduced to graphene,in the same time,the interaction between the new formed sulfur molecules and the functional groups on graphene surface was strengthened,playing a role of fixation of sulfur.”in the last paragraph of the introduction part should be“Zhouet al.21pointed out under hydrothermal condition,superheated water promoted the H+-catalyzed dehydration of oxygen functional groups on the surface of graphene oxide and graphene oxide was converted to graphene.In one-step hydrothermal method,graphene oxide was reduced,at the same time,the sulfur molecules were formed.As a result,the interaction between the new formed sulfur molecules and the functional groups on graphene surface was strengthened.”

Hydrogenation of Nitrobenzene Catalyzed by Metal-Organic Framework-Supported Ni Nanoparticles

JIANG Jun LI Gang*KONG Ling-Hao
(State Key Laboratory of Fine Chemicals,School of Chemical Engineering,Dalian University of Technology, Dalian 116024,Liaoning Province,P.R.China)

The metal-organic frameworks(MOFs),MIL-53(Al),MIL-96(Al),and MIL-120(Al)(MIL:Material Institute of Lavorisier)were synthesized and used as supports,to incorporate low-cost Ni nanoparticles(NPs) by wet impregnation.The samples were used as catalysts in the hydrogenation of nitrobenzene to aniline.The catalyst prepared with MIL-53(Al)as a support exhibited excellent catalytic performance.Ni/MIL-53(Al) heterogeneous catalysts were prepared using nickel nitrate,nickel acetate,and nickel ethanediamine as precursors.Characterization by powder X-ray diffraction,Fourier-transform infrared spectroscopy,inductively coupled plasma spectroscopy,N2sorption measurements,H2-temperature programmed reduction,and transmission electron microscopy showed that the Ni precursor affected the metal-support interaction,Ni particle size and particle distribution.The catalyst prepared using nickel ethanediamine possessed moderate metalsupport interactions,smaller Ni nanoparticles(4-5 nm),and a high Ni distribution.This resulted in its superior catalytic activity,with 100%conversion of nitrobenzene in the hydrogenation.The Ni/MIL-53(Al)catalyst retained its catalytic activity after five cycles,and exhibited a nitrobenzene conversion of～92%.

Metal-organic framework;Nickel;Support;Precursor;Nitrobenzene hydrogenation

O643

10.3866/PKU.WHXB201411171www.whxb.pku.edu.cn

Received:September 17,2014;Revised:November 14,2014;Published on Web:November 17,2014.

?Corresponding author.Email:liganghg@dlut.edu.cn;Tel/Fax:+86-411-8498-6113.

The project was supported by the National Key Basic Research Program of China(973)(2011CB201301).

國(guó)家重點(diǎn)基礎(chǔ)研究發(fā)展規(guī)劃項(xiàng)目(973)(2011CB201301)資助