硅钨酸-SBA-15介孔固体酸的直接合成、表征及催化油酸甲酯化性能
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摘要
分别以硅酸乙酯为硅源、P123为模板剂,采用直接水热合成法将不同量的硅钨杂多酸(HSiW)直接固载于六方相介孔分子筛SBA-15中,利用XRD、N_2 adsorption-desorption、FT-IR、DR UV-Vis、TEM、Py-IR等手段对材料进行了表征,并且以油酸甲酯合成反应为探针反应,评价其催化性能.结果表明:所制备的HSiWSBA-15催化剂中HSiW呈高分散状态,并具有SBA-15的介孔结构和HSiW的Keggin型结构特征;同时,随着HSiW固载量的增加,所制催化剂中SBA-15的介孔长程有序性减弱;对油酸与甲醇酯化反应呈现出较好的催化性能,其中25%HSiW-SBA-15催化活性最佳,并显示出较好的循环使用性能.
A series of SBA-15 materials functionalized with 12-silicotungstic acid(HSiW-SBA-15) were onepot hydrothermally synthesized with Pluronic PI 23 as template and tetraethylorthosilicate as the silica source.The materials were characterized by various techniques,such as XRD.N_2 adsorption-desorption.FT-IR,DR UV-Vis.TEM and Py-TR.Their catalytic activities for the synthesis of biodiesel were investigated comparatively with the esterification of oleic acid with methanol as the probe reaction.The results showed that the HSiW was highly dispersed and resulting materials maintained the ordered mesoporous structure of SBA-15 and the Keggin structure of HSiW.On the other hand,the functionality of HSiW influenced the long range order of SBA-15 to some extent,which decreased with the increase of HSiW dosage.Furthermore,the HSiW-SBA-15 was efficient for oleic acid esterification and 25%HSiW-SBA-15 with excellent durability was found to be more active than the others.
A series of SBA-15 materials functionalized with 12-silicotungstic acid(HSiW-SBA-15) were onepot hydrothermally synthesized with Pluronic PI 23 as template and tetraethylorthosilicate as the silica source.The materials were characterized by various techniques,such as XRD.N_2 adsorption-desorption.FT-IR,DR UV-Vis.TEM and Py-TR.Their catalytic activities for the synthesis of biodiesel were investigated comparatively with the esterification of oleic acid with methanol as the probe reaction.The results showed that the HSiW was highly dispersed and resulting materials maintained the ordered mesoporous structure of SBA-15 and the Keggin structure of HSiW.On the other hand,the functionality of HSiW influenced the long range order of SBA-15 to some extent,which decreased with the increase of HSiW dosage.Furthermore,the HSiW-SBA-15 was efficient for oleic acid esterification and 25%HSiW-SBA-15 with excellent durability was found to be more active than the others.
引文
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[3]XU L L,WANG Y H,YANG X,et al.Preparation of mesoporous polyoxometalate-tantalum pentoxide composite catalyst and its application for biodiesel production by esterification and transesterification[J].Green Chemistry,2008,10(7):746-7oo.
[4]KAZEM1AN H,TUROWEC B,S1DD1QUEE M N,et al.Biodiesel production using cesium modified mesoporous ordered silica as heterogeneous base catalyst[J].Fuel,2013,103:719-724.
[5]FENG Y H,HE B Q,CAO Y H,et al.Biodiesel production using cation-exchange resin as heterogeneous catalyst[J].Bioresource Technology,2010,101(5):1518-1521.
[6]陈雅.M41S及SBA-15介孔分子筛固载硅钨酸催化剂的制备表征及催化性能研究[D].郑州:郑州大学,2015.CHEN Ya.Preparation,characterization and catalytic properties of phosphotungstic acid supported on M41S and SBA-lo mesoporous molecular sieves[D].Zhengzhou:Zhengzhou University,201o.
[7]CHEN Y,CAO Y,SUO Y,et al.Mesoporous solid acid catalysts of 12-tungstosilicic acid anchored to SBA-15:Characterization and catalytic properties for esterification of oleic acid with methanol[J].Journal of the Taiwan Institute of Chemical Engineers,201o,ol:186-192.
[8]WANG JC,LIU Q.Structural change and characterization in nitrogen-incorporated SBA-15 oxynitride mesoporous materials via different thermal historyCJ].Microporous and Mesoporous Materials,2005,83(1 2 3):225-232.
[9]AYDEM1R B,SEZG1 N A,DOGU T.Synthesis of TPA impregnated SBA-15 catalysts and their performance in polyethtlene degradation reaction[J].AlChE Journal,2012,58(8):2466-2472.
[10]V1NU A,SAT1SH KUMAR G,AR1GA K,et al.Preparation of highly ordered mesoporous A1SBA-15 and its application to isopropylation of m-cresol[J].Journal of Molecular Catalysis A-Chemical,2005,235(1 2):57-66.
[11]ZHANG J,OHN1SH1 R,KAM1YA Y,et al.Improved catalytic activity using water for isomerization of linear butane to isobutene over heteropolyacid catalysts[J].Journal of Catalysis,2008,254(2):263-271.
[12]KIM J K,CHOI J H,SONG J H,et al.Etherification of n-butanol to di-n-butyl ether over H_nXW_(12)O_(40)(X=Co~(2+),B~(3+),Si~(4+),and P~(5+))Keggin heteropolyacid catalysts[J].Catalysis Communications,2012,27:5-8.
[13]NOW1NSKA K,F'ORMANIAK R,KALETA W,et al.Heteropoly compounds incorporated into mesoporous material structured].Applied Catalysis A-General,2003,256(1/2):115-123.
[14]KOZHEVN1KOV I V,KLOETSTRA K R,S1NNEMA A,et al.Study of catalysts comprising heteropoly acid H_3PW_(12)O_(40)supported on MCM-41 molecular sieve and amorphous silica[J].Journal of Molecular Catalysis A-Chemical,1996,114(1 2 3):287-298.
[15]Tsigdinos G A.Heteropoly compounds of molybdenum and tungsten[J].Topics in Current Chemistry,1978,76:1-64.
[16]KHDER A S,HASSAN H,EL-SHALL M S.Acid catalyzed organic transformations by heteropoly tungstophosphoric acid supported on MCM-41[J].Applied Catalysis A-General,2012,411:77-86.