摘要
负载型Pt基催化剂是一类重要的工业催化剂,在很多还原和氧化反应中都表现出很高的催化活性,但高昂的价格一直制约着Pt基催化剂的大规模应用.另外, Pt活性位点对有机化合物不同基团的区分性差,通常造成目的产物的选择性较低.以人们熟知的芳香硝基化合物加氢为例,当有其它易还原基团如C=C、C=O、–X等存在时,在硝基加氢的同时,这些基团也不同程度地被还原.在已报道的工作中,通过合理设计Pt活性中心结构、改善Pt周围环境以及在反应中添加无机盐或有机化合物等方法,芳香硝基化合物加氢的选择性获得大幅提升,但催化剂活性对Pt负载量的依赖性仍然很高,降低催化剂中的Pt活性位数量会显著降低催化剂活性.此外, Pt纳米粒子在反应过程中的聚集以及氧化物载体在强还原气氛下的性能变化等对催化剂的稳定性产生很大影响.本文工作中我们尝试发挥载体在反应中的作用,实现氢解离和反应物加氢活性中心在空间上分离,从而降低Pt的负载量.工作思路主要是基于氢溢流的基本原理,其难点在于高效氢解离活性中心的设计和载体的选择,后者需满足活泼氢物种的输运和硝基基团的有效吸附.为了实现上述目标,本文采用胶体法制备了3–4 nm的Pt粒子,该方法可以有效地控制Pt纳米粒子的尺寸以及在载体上的分散状态,从而形成大量的Pt0活性位,实现高效氢解离.在充分考虑载体的氧化还原性和表面碱性质(给电子能力)的基础上,我们筛选了多种氧化物作为载体.反应结果显示, Pt/α-Fe_2O_3在Pt负载量仅为0.2 wt%时即表现出很高的芳香硝基化合物加氢催化活性和选择性,并且该反应可在相当温和的条件(30°C, 5 barH_2)下进行.在经过多次循环反应后, Pt纳米粒子的尺寸、分散状态以及α-Fe_2O_3载体的物相等均未发生变化,催化剂表现出很高的稳定性.Pt纳米粒子的高效氢解离能力是催化剂实现高活性的重要因素之一,而α-Fe_2O_3的表面性质也同样发挥了重要作用,其表面一定数量的氧空位具有较强的给电子能力,可以与具有较强吸电子能力的硝基基团作用,实现反应物的高效吸附;载体表面适当的氧化还原性有利于活泼氢的输运,在与Pt纳米粒子的协同作用下实现了温和条件下芳香硝基化合物的选择性加氢.本工作显著降低了Pt的使用量,实现了非常温和条件下的稳定、高效加氢,可为低成本Pt基催化剂的设计提供借鉴.
An efficient and low-cost supported Pt catalyst for hydrogenation of niroarenes was prepared with colloid Pt precursors and α-Fe_2O_3 as a support. The catalyst with Pt content as low as 0.2 wt% exhibits high activities, chemoselectivities and stability in the hydrogenation of nitrobenzene and a variety of niroarenes. The conversion of nitrobenzene can reach 3170 mol_(conv) h~(–1) mol Pt~(–1) under mild conditions(30 °C, 5 bar), which is much higher than that of commercial Pt/C catalyst and many reported catalysts under similar reaction conditions. The spatial separation of the active sites for H_2 dissociation and hydrogenation should be responsible for the high chemoselectivity, which decreases the contact possibility between the reducible groups of nitroarenes and Pt nanoparticles. The unique surface properties of α-Fe_2O_3 play an important role in the reaction process. It provides active sites for hydrogen spillover and reactant adsorption, and ultimately completes the hydrogenation of the nitro group on the catalyst surface.
引文
[1]E.Schmidt,A.Vargas,T.Mallat,A.Baiker,J.Am.Chem.Soc.,2009,131,12358-12367.
[2]W.Y.Cui,D.Xue,N.D.Tan,B.Zheng,M.J.Jia,W.X.Zhang,Chin.J.Catal.,2018,39,1534-1542.
[3]J.J.Liu,S.H.Zou,J.C.Wu,H.Kobayashi,H.T.Zhao,J.Fan,Chin.J.Catal.,2018,39,1081-1089.
[4]B.Zheng,S.J.Wu,X.W.Yang,M.J.Jia,W.X.Zhang,G.Liu,ACS.Appl.Mater.Inter.,2016,8,26683-26689.
[5]P.P.Ye,A.J.Gellman,J.Am.Chem.Soc.,2008,130,8518-8526.
[6]G.C.da Silva,M.R.Fernandes,E.A.Ticianelli,ACS.Catal.,2018,8,2081-2092.
[7]Z.J.Chen,J.Y.Chen,Y.W.Li,Chin.J.Catal.,2017,38,1108-1126.
[8]S.Anantharaj,P.E.Karthik,B.Subramanian,S.Kundu,ACS.Catal.,2016,6,4660-4672.
[9]Y.L.Sui,S.B.Liu,T.F.Li,Q.X.Liu,T.Jiang,Y.F.Guo,J.L.Luo,J.Catal.,2017,353,250-255.
[10]L.L.Geng,M.Zhang,W.X.Zhang,M.J.Jia,W.F.Yan,G.Liu,Catal.Sci.Technol.,2015,5,3097-3102.
[11]R.V.Jagadeesh,A.E.Surkus,H.Junge,M-M.Pohl,J.Radnik,J.Rabeah,H.Huan,V.Schünemann,A.Brückner,M.Beller,Science,2013,342,1073-1076.
[12]Y.J.Shu,T.Chen,H.C.Chan,L.F.Xie,Q.S.Gao,Chem-Asian.J.,2018,13,3737-3744.
[13]Q.M.Hu,S.Wang,Z.Gao,Y.Q.Li,Q.Zhang,Q.Xiang,Y.Qin,Appl.Catal.B:Environ.,2017,218,591-599.
[14]M.W.Zhu,B.Huang,Q.Shao,Y.C.Pi,Y.Qian,X.Q.Huang,Chem Cat Chem.,2018,10,3214-3218.
[15]W.Shi,B.S.Zhang,Y.M.Lin,Q.Wang,Q.Zhang,D.S.Su,ACS.Catal.,2016,6,7844-7854.
[16]P.Lara,K.Philippot,Catal.Sci.Technol.,2014,4,2445-2465.
[17]G.Vilé,D.Albani,N.Almora-Barrios,N.López,J.Pérez-Ramírez,Chem Cat Chem.,2016,8,21-33.
[18]J.Wang,Y.J.Zhang,J.Y.Diao,J.Y.Zhang,H.Y.Liu,D.S.Su,Chin.J.Catal.,2018,39,79-87.
[19]K.M?bus,D.Wolf,H.Benischke,U.Dittmeier,K.Simon,U.Packruhn,R.Jantke,S.Weidlich,C.Weber,B.S.Chen,Top.Catal.,2010,53,1126-1131.
[20]M.Makosch,W-I.Lin,V.Bumbálek,J.Sá,J.W.Medlin,K.Hungerbühler,J.A.van Bokhoven,ACS.Catal.,2012,2,2079-2081.
[21]K-i.Shimizu,Y.Miyamoto,A.Satsuma,J.Catal.,2010,270,86-94.
[22]K-i.Shimizu,Y.Miyamoto,T.Kawasaki,T.Tanji,Y.Tai,A.Satsuma,J.Phys.Chem.C.,2009,113,17803-17810.
[23]T.Mitsudome,Y.Mikami,M.Matoba,T.Mizugaki,K.Jitsukawa,K.Kaneda,Angew.Chem.Int.Ed.,2012,51,136-139.
[24]H.S.Wei,X.Y.Liu,A.Q.Wang,L.L.Zhang,B.T.Qiao,X.F.Yang,Y.Q.Huang,S.Miao,J.Y.Liu,T.Zhang,Nat.Commun.,2014,5,5634-5641.
[25]A.Corma,P.Serna,P.Concepcion,J.J.Calvino,J.Am.Chem.Soc.,2008,130,8748-8753.
[26]S.Zhang,C.R.Chang,Z.Q.Huang,J.Li,Z.M.Wu,Y.Y.Ma,Z.Y.Zhang,Y.Wang,Y.Q.Qu,J.Am.Chem.Soc.,2016,138,2629-2637.
[27]L.Wang,E.J.Guan,J.Zhang,J.H.Yang,Y.H.Zhu,Y.Han,M.Yang,C.Cen,G.Fu,B.C.Gates,F.S.Xiao,Nat.Commun.,2018,9,1362-1369.
[28]H.S.Wei,Y.J.Ren,A.Q.Wang,X.Y.Liu,X.Liu,L.L.Zhang,S.Miao,L.Li,J.Y.Liu,J.H.Wang,G.F.Wang,D.S.Su,T.Zhang,Chem.Sci.,2017,8,5126-5131.
[29]B.Zhang,H.Asakura,J.Zhang,J.G.Zhang,S.De,N.Yan,Angew.Chem.Int.Ed.,2016,55,8319-8323.
[30]W.Karim,C.Spreafico,A.Kleibert,J.Gobrecht,J.VandeVondele,Y.Ekinci,J.A.van Bokhoven,Nature,2017,541,68-71.
[31]L.R.Merte,G.Peng,R.Bechstein,F.Rieboldt,C.A.Farberow,L.C.Grabow,W.Kudernatsch,S.Wendt,E.Laegsgaard,M.Mavrikakis,F.Besenbacher,Science,2012,336,889-893.
[32]R.Prins,Chem.Rev.,2012,112,2714-2738.
[33]B.Zheng,G.Liu,L.L.Geng,J.Y.Cui,S.J.Wu,P.Wu,M.J.Jia,W.F.Yan,W.X.Zhang,Catal.Sci.Technol.,2016,6,1546-1554.
[34]A.Corma,P.Serna,H.Garcia,J.Am.Chem.Soc.,2007,129,6358-6359.
[35]M.Boronat,P.Concepcion,A.Corma,S.Gonzalez,F.Illas,P.Serna,J.Am.Chem.Soc.,2007,129,16230-16237.
[36]J.L.Song,G.Y.Yu,X.Li,X.W.Yang,W.X.Zhang,W.F.Yan,G.Liu,Chin.J.Catal.,2018,39,309-318.
[37]L.Q.Liu,F.Zhou,L.G.Wang,X.J.Qi,F.Shi,Y.Q.Deng,J.Catal.,2010,274,1-10.
[38]Z.Z.Yang,N.Zhang,Y.Cao,M.C.Gong,M.Zhao,Y.Q.Chen,Catal.Sci.Technol.,2014,4,3032-3043.
[39]R.Ahmadi,M.K.Amini,J.C.Bennett,J.Catal.,2012,292,81-89.
[40]E.Ivanova,M.Mihaylov,F.Thibault-Starzyk,M.Daturi,K.Hadjiivanov,J.Mol.Catal.A,2007,274,179-184.
[41]S.Shen,X.L.Wang,Q.Ding,S.Q.Jin,Z.C.Feng,C.Li,Chin.J.Catal.,2014,35,1900-1906.
[42]G.Richner,J.A.van Bokhoven,Y.M.Neuhold,M.Makosch,K.Hungerbuhler,Phys.Chem.Chem.Phys.,2011,13,12463-12471.
[43]S.Meijers,V.Ponec,J.Catal.,1996,160,1-9.
[44]D.Flak,Q.Chen,B.S.Mun,Z.Liu,M.R?kas,A.Braun,Appl.Surf.Sci.,2018,455,1019-1028.
[45]S.Sultana,S.Mansingh,K.M.Parida,J.Mater.Chem.A.,2018,6,11377-11389.
[46]L.L.Geng,J.L.Song,B.Zheng,S.J.Wu,W.X.Zhang,M.J.Jia,G.Liu,Chin.J.Catal.,2016,37,1451-1460.