Co_(0.5)PW/MCM-41在酰化反应中的催化性能
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摘要
将金属阳离子改性的磷钨酸盐(Co0.5PW,Cs2.5PW)负载到MCM-41介孔分子筛上,制备了负载型磷钨酸(盐)催化剂(Co0.5PW/M,Cs2.5PW/M,PW/M),考察其在苯甲醚与乙酸酐的Friedel-Crafts酰化反应中的催化活性;同时对催化剂样品进行XRD、N2吸-脱附测试、TG-DSC、IR、NH3-TPD等表征分析,对比研究杂多酸(盐)与载体之间的相互作用对催化剂活性影响。结果表明:磷钨酸盐(Co0.5PW和Cs2.5PW)用于苯甲醚的Friedel-Crafts酰化反应时,催化活性低于纯PW;其中,Cs2.5PW的活性高于Co0.5PW。将磷钨酸(盐)负载到MCM-41介孔分子筛后,PW/M的催化活性低于纯PW;Co0.5PW/M与Co0.5PW相比,催化活性显著提高,且高于PW/M;这是由于Co0.5PW较好地分散到载体上,且其与载体间的相互作用增加了酸中心数目,有效提高了催化活性。而Cs2.5PW/M几乎没有催化活性;这是由于Cs2.5PW与载体发生相互作用使Keggin结构发生畸变,酸强度显著减弱、酸中心数目显著减少所致。
Phosphotungstate acid or metal cation-modified phosphotungstate supported by siliceous MCM-41 molecular sieve(Co0.5PW/M,Cs2.5PW/M,PW/M) were prepared and their catalytic activities in the anisole Friedel-Crafts acylation reaction were investigated. The prepared samples were characterized by XRD, N2adsorption-desorption, TG-DSC, IR and NH3-TPD in order to study the interaction between the active components and the supports and their effects on catalytic activities. The results show that, for Friedal-Crafts acylation, the catalytic activities of the cation-modified phosphotungstate are lower than that of bulk PW, while the catalytic activity of Cs2.5PW is higher than that of Co0.5PW. When supported on MCM-41,the catalytic activity of PW/M is lower than bulk PW, while the catalytic activity of Co0.5PW/M shows an obvious increase compared to that of Co0.5PW, which is attributed to the fine dispersion of Co0.5PW on the support, and also due to the increase of acidic sites on the surface of the catalyst by the interaction between Co0.5PW and the support. In the contrary, Cs2.5PW/M has little catalytic activity due to the decrease of acidic sites caused by the interaction between Cs2.5PW and the support.
Phosphotungstate acid or metal cation-modified phosphotungstate supported by siliceous MCM-41 molecular sieve(Co0.5PW/M,Cs2.5PW/M,PW/M) were prepared and their catalytic activities in the anisole Friedel-Crafts acylation reaction were investigated. The prepared samples were characterized by XRD, N2adsorption-desorption, TG-DSC, IR and NH3-TPD in order to study the interaction between the active components and the supports and their effects on catalytic activities. The results show that, for Friedal-Crafts acylation, the catalytic activities of the cation-modified phosphotungstate are lower than that of bulk PW, while the catalytic activity of Cs2.5PW is higher than that of Co0.5PW. When supported on MCM-41,the catalytic activity of PW/M is lower than bulk PW, while the catalytic activity of Co0.5PW/M shows an obvious increase compared to that of Co0.5PW, which is attributed to the fine dispersion of Co0.5PW on the support, and also due to the increase of acidic sites on the surface of the catalyst by the interaction between Co0.5PW and the support. In the contrary, Cs2.5PW/M has little catalytic activity due to the decrease of acidic sites caused by the interaction between Cs2.5PW and the support.
引文
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[3]Shimizu K-i,Niimi K,Satsuma A.Polyvalent-metal salts of heteropolyacid as catalyst for Friedel-Crafts alkylation reactions[J].Appl Catal A,2008,349(1-2):1-5.
[4]Shimizu K-i,Niimi K,Satsuma A.Polyvalent-metal salts of heteropolyacid as efficient heterogeneous catalysts for Friedel-Crafts acylation of arenes with carboxylic acids[J].Catal Commun,2008,9(6):980-983.
[5]Méndez L,Torviso R,Pizzio L,et al.2-Methoxynaphthalene acylation using aluminum or copper salts of tungstophosphoric and tungstosilicic acids as catalysts[J].Catal Today,2011,173(1):32-37.
[6]Ramesh K C,Rao K T V,Sai P P S,et al.Tin exchanged heteropoly tungstate:an efficient catalyst for benzylation of arenes with benzyl alcohol[J].J Mol Catal A:Chem,2011,337(1-2):17-24.
[7]SHI Jie-hua(施介华),LI Xiang(李祥),ZHOU Liang(周亮).Application of transition metal-modified phosphotungstate catalysts in Friedel-Crafts acetylation(过渡金属修饰的磷钨酸盐催化剂在Friedel-Crafts乙酰化反应中的应用)[J].Petrochemical Technology(石油化工),2010,39(12):1354-1359.
[8]SHI Jie-hua(施介华),HU Yu-hua(胡玉华),LI Xiang(李祥).Synthesis of p-methoxyacetophenone catalyzed by cesium phosphotungstate(磷钨酸铯催化合成对甲氧基苯乙酮)[J].Petrochemical Technology(石油化工),2009,38(2):158-163.
[9]Sawant D P,Vinu A,Lefebvre F,et al.Tungstophosphoric acid supported over zirconia in mesoporous channels of MCM-41 as catalyst in veratrole acetylation[J].J Mol Catal A:Chem,2007,262(1-2):98-108.
[10]Parida K M,Rana S,Mallick S,et al.Cesium salts of heteropoly acid immobilized mesoporous silica:an efficient catalyst for acylation of anisole[J].J Colloid Interface Sci,2010,350(1):132-139.
[11]JIN Bin(金滨),ZHANG Bo(张波),LI Xiu-juan(李秀娟),et al.Supported ZrOx/MCM-41 catalysts for MPV reductions of benzyl aldehyde(MCM-41分子筛催化α,β-不饱和醛的MPV还原反应的研究)[J].J Chem Eng of Chinese Univ(高校化学工程学报),2008,22(2):270-276.
[12]Juan J C,Zhang J,Yarmo M A.12-Tungstophosphoric acid supported on MCM-41 for esterification of fatty acid under solvent-free condition[J].J Mol Catal A:Chem,2007,267(1-2):265-271.
[13]Alsalme A M,Wiper P V,Khimyak Y Z,et al.Solid acid catalysts based on H3PW12O40 heteropolyacid:acid and catalytic properties at a gas-solid interface[J].J Catal,2010,276(1):181-189.