在交联聚苯乙烯微球表面实现苯基卟啉的同步合成与固载

以键合有对羟基苯甲醛(HBA)的交联聚苯乙烯(CPS)微球HBA-CPS、苯甲醛和吡咯为反应物, 采用Adler方法, 实现了苯基卟啉(PP)在CPS表面的同步合成与固载, 制得了固载有苯基卟啉的微球PP-CPS. 研究了卟啉同步合成与固载过程的影响因素, 同时进行了微球PP-CPS与钴盐的配合反应, 制备了固载有钴卟啉(CoP)的功能微球CoP-CPS, 初步考察了其对分子氧氧化乙苯的催化活性. 实验结果表明, 在苯基卟啉同步合成与固载的反应过程中, 催化剂的酸性与溶剂的极性是两个主要的影响因素, 使用强极性溶剂与pKa在2.8~3.4范围的酸, 微球PP-CPS表面的苯基卟啉固载量高. 微球CoP-CPS对分子氧氧化乙苯的反应具有明显的催化活性.     

在聚合物微球 GMA/MMA 表面同步合成与固载卟啉及固载化金属卟啉的催化氧化性能

 制备了甲基丙烯酸缩水甘油酯 (GMA) 与甲基丙烯酸甲酯 (MMA) 共聚微球 GMA/MMA, 并通过键合有对羟基苯甲醛 (HBA) 的改性微球 HBA-GMA/MMA 与苯甲醛 (或取代苯甲醛) 以及吡咯间的 Adler 反应, 实现了卟啉在共聚微球 GMA/MMA 表面的同步合成与固载, 制得了固载有苯基卟啉 (PP)、对氯苯基卟啉 (CPP)、对硝基苯基卟啉 (NPP) 的功能化微球 PP-GMA/MMA, CPP-GMA/MMA 和 NPP-GMA/MMA. 重点考察了影响卟啉同步合成与固载过程的因素. 制备了固载有钴卟啉的催化剂, 并以分子氧氧化乙苯为模型反应, 考察了催化剂的活性. 结果表明, 苯甲醛取代基的结构、催化剂的酸性和溶剂的极性对卟啉的同步合成与固载都有较大的影响; 钴卟啉催化剂对分子氧氧化乙苯反应具有较高的催化活性, 且当钴卟啉外环上含有强吸电子基团硝基时, 催化剂活性最高.     

固载MnP-PGMA/SiO2催化剂的制备及其对乙苯氧化反应的催化性能

在溶液聚合体系中,将聚甲基丙烯酸缩水甘油酯(PGMA)接枝在硅胶微粒表面,制备了接枝微粒PGMA/SiO2;通过环氧键的开环反应,实现了Meso-四(对羟基苯基)卟啉(THPP)在PGMA/SiO2上的键合,制备了键合有羟基苯基卟啉(HPP)的HPP-PGMA/SiO2;进一步使锰盐与HPP-PGMA/SiO2发生配位反应,制备了固载MnP(锰卟啉)-PGMA/SiO2催化剂.以分子氧为氧源,将MnP-PGMA/SiO2催化剂用于乙苯氧化反应,常压下实现了乙苯向苯乙酮的转化,并探索了乙苯氧化过程中的若干规律.结果表明,MnP-PGMA/SiO2催化剂能有效活化分子氧,显著催化乙苯氧化为苯乙酮的反应过程;于95℃常压下反应12 h,苯乙酮收率接近18%,产物α-甲基苄醇的含量则极少.在催化氧化体系中,作为仿生催化剂的MnP存在最适宜用量,过量的MnP反而会抑制催化剂活性.在PGMA/SiO2表面,MnP的固载密度越小,催化剂的活性越高.在循环使用中,催化剂的活性呈升高的趋势.     

P(4VP-co-St)/SiO2固载的取代钴卟啉对乙苯的催化氧化性能

通过轴向配位法将不同结构的钴卟啉(CoTXPP(X=H, Cl, NO2))分别固载到接枝微粒聚(4-乙烯基吡啶-co-苯乙烯)/SiO2(P(4VP-co-St)/SiO2)上, 室温下分别制备了P(4VP-co-St)/SiO2固载的金属卟啉催化剂CoTPP-P(4VP-co-St)/SiO2, CoTClPP-P(4VP-co-St)/SiO2和CoTNPP-P(4VP-co-St)/SiO2, 利用傅立叶变换红外(FTIR)光谱和电子吸收光谱对其结构及轴配过程进行了表征. 在无溶剂、无助催化剂和还原剂的体系中, 研究对比了其催化分子氧氧化乙苯为苯乙酮的性能, 考察了不同反应条件对苯乙酮产率的影响. 研究发现, 其催化活性随着环外取代基吸电子能力的增强而提高. CoTNPP-P(4VP-co-St)/SiO2的催化活性和选择性最好, 在120 ℃常压下其催化乙苯反应12 h, 苯乙酮收率达到25.53%, 产物α-甲基苄醇的含量则极少. 与普通的催化剂不同, 在催化氧化体系中, CoTNPP-P(4VP-co-St)/SiO2存在最适宜用量, 过量的CoTNPP-P(4VP-co-St)/SiO2反而会使其催化活性降低; P(4VP-co-St)/SiO2表面CoTXPP的固载密度存在一最佳值. 此外, 固载化以后, 催化剂具有较好的重复使用性. 结果表明, 接枝微粒P(4VP-co-St)/SiO2对金属卟啉不仅有明显的保护作用, 而且能提高其稳定性.     

在醛基化交联聚苯乙烯微球表面同步合成与固载卟啉及固载化金属卟啉的高效催化氧化性能

采用Kornblum氧化反应, 先将氯甲基交联聚苯乙烯(CMCPS)的氯甲基氧化为醛基, 制得醛基(AL)化改性微球ALCPS, 然后使改性微球ALCPS与溶液中的苯甲醛(或取代的苯甲醛)、吡咯之间发生固-液相之间的Adler反应, 成功地实现了卟啉在交联聚苯乙烯微球表面的同步合成与固载, 制得了固载有苯基卟啉(PP) 、对氯苯基卟啉(CPP)、对硝基苯基卟啉(NPP)的功能微球, 最后使功能微球与钴盐发生配合反应, 制备了固载有三种钴卟啉的固体催化剂. 研究重点有两方面: (1)考察主要因素对卟啉同步合成与固载过程的影响|(2)考察固载化钴卟啉在催化分子氧氧化环己烷羟基化过程中的催化特性. 实验结果表明, 以醛基化改性微球ALCPS与溶液中的吡咯及小分子苯甲醛(或取代的苯甲醛)为共反应物, 通过固-液之间的Adler反应, 可以顺利地实现卟啉在微球ALCPS表面的同步合成与固载, 这是制备固载化卟啉的新途径|苯甲醛的取代基结构、催化剂的酸性与溶剂的性质对卟啉的同步合成与固载都有较大的影响|所制备的固体催化剂对分子氧氧化环己烷羟基化的反应, 具有很高的催化活性(环己烷最高转化率约为40%)与选择性(环己醇的选择性在90%以上), 这是由固体催化剂特殊的化学结构所决定的.     

硅胶固载聚4-乙烯吡啶-Cu(Ⅱ)配合物催化分子氧氧化乙苯的性能研究

以固载于微米级硅胶表面的聚4-乙烯吡啶-铜(Ⅱ)配合物(P4VP-Cu(Ⅱ)/SiO2)为催化剂,以分子氧为氧化剂,在常压下实施了将乙苯氧化为苯乙酮的催化氧化反应;用红外光谱、紫外光谱及液相色谱对产物的化学结构进行了表征;重点研究了催化剂的催化性能,以及各种条件(温度、催化剂性质、催化剂用量等)对催化氧化反应的影响;并分析了催化氧化反应的机理.研究结果表明,固载于硅胶表面的聚4-乙烯吡啶-Cu(Ⅱ)配合物能有效地活化分子氧,显著地催化氧化乙苯为苯乙酮的反应过程;该催化剂具有优良的催化活性与选择性,于130℃常压下通氧气反应10h,可使约60%的乙苯转化为苯乙酮,另一氧化产物α-甲基苄醇的含量则极少.另外,该催化剂具有较好的重复使用稳定性.     

接枝微粒PGMA／SiO2固载的金属卟啉仿生催化剂的制备

采用"接枝"法将甲基丙烯酸缩水甘油酯(GMA)接枝聚合到硅胶微粒表面,通过环氧键与羟基的开环成醚反应,进而将小分子的对羟基苯基卟啉化学键合在接枝微粒PGMA/SiO2表面,再与金属锰配位,从而制得了PGMA/SiO2固载的金属卟啉仿生催化剂(MnP-PGMA/SiO2);并用红外光谱法和原子吸收光谱法进行了表征;重点研究了对羟基苯基卟啉在接枝微粒PGMA/SiO2表面键合反应的规律;初步考察了MnP-PGMA/SiO2对分子氧氧化乙苯为苯乙酮的催化作用。实验结果表明:在键合反应中以4.5mL三乙胺为催化剂,在70℃下反应8h,可制得卟啉键合量为69.36μmol/g的键合微粒HPP-PGMA/SiO2;HPP-PGMA/SiO2与锰配位时,在64℃下反应8h,得到锰有效配位程度为92.34%的固体催化剂MnP-PGMA/SiO2。在催化分子氧氧化乙苯为苯乙酮的过程中,固体催化剂MnP-PGMA/SiO2具有高的催化活性。     

在CPS微球表面实现N-羟基邻苯二甲酰亚胺的同步合成与固载及固体催化剂催化氧化性能初探

通过分子设计的构思,仅通过两步大分子反应,便实现了N-羟基邻苯二甲酰亚胺(NHPI)在交联聚苯乙烯(CPS)微球表面的同步合成与固载,并制得了非均相催化剂微球CPS-NHPI。以氯化偏苯三酸酐(TMAC)为试剂、Lewis酸为催化剂,通过Friedel-Crafts酰基化反应,先将邻苯二甲酸酐(PA)基团键合在CPS微球表面,得到改性微球CPS-PA;再与盐酸羟胺进行酰亚胺反应,制备出固载有NHPI基团的非均相催化剂微球CPS-NHPI。重点研究了CPS微球表面发生Friedel-Crafts酰基化反应的影响因素。采用红外光谱(FT-IR)及扫描电子显微镜(SEM)等对微球CPS-NHPI进行表征,将微球CPS-NHPI分别用于分子氧氧化乙苯及环己烷两种烃类物质的氧化过程,初步考察了该微球的催化活性。研究结果表明,对于微球CPS与TMAC之间的FriedelCrafts酰基化反应,适宜的溶剂为氯仿与N,N-二甲基乙酰胺(DMAC)混合溶剂(氯仿与DMAC的体积比为7∶3),适宜的Lewis酸催化剂为SnCl4。初步探索实验表明,催化剂微球CPS-NHPI与Co(OAc)2所构成的共催化体系,在分子氧氧化乙苯及环己烷的催化氧化过程中,都表现出了良好的催化活性,温和条件下,反应35h时乙苯氧化为苯乙酮的转化率可达37%,反应30h时环己烷氧化为环己酮的转化率可达21%。     

固载化N,N-双齿席夫碱型氧钒(Ⅳ) 配合物的制备 及其在分子氧氧化乙苯中的催化作用

以交联聚苯乙烯(CPS)微球为初始物质,通过大分子反应,制备了键合有苯甲醛(BA)的聚合物微球BA-CPS,又以3-氨基吡啶(AP)为试剂,使微球BA-CPS与之发生席夫碱反应,制得了键合有N,N-双齿席夫碱配基的微球BAAP-CPS;然后使微球BAAP-CPS与硫酸氧钒发生配位螯合反应,成功制备了固载有N,N-双齿席夫碱型氧钒(Ⅳ)配合物的微球CPS-[VO(BAAP)2].用红外光谱(FTIR)和固体紫外吸收光谱等手段对微球CPS-[VO(BAAP)2]的化学结构进行了表征.将微球CPS-[VO(BAAP)2]用于乙苯的分子氧催化氧化过程,考察了其催化活性及主要因素对乙苯催化氧化反应的影响,探索研究了催化反应机理.实验结果表明,在分子氧氧化乙苯的反应中,微球CPS-[VO(BAAP)2]具有很高的催化活性和优良的催化选择性,可将乙苯高效地(45%的转化率)转化为单一产物苯乙酮.氧化反应可能遵循自由基反应历程,乙苯侧烷基氢过氧化物可能是关键的中间物.适宜的反应温度为110℃,且体系中催化剂有一适宜用量.     

钴卟啉催化剂的前线轨道能级与其催化活性的相关性研究

设计并合成了12种钴卟啉催化剂,在温和反应条件(55℃, 2.0 MPa氧压)下考察其催化氧气液相氧化对硝基甲苯制取对硝基苯甲酸的催化活性,发现其对上述反应均有显著的催化活性.采用PM3半经验分子轨道法对所设计的钴卟啉化合物模型体系进行了计算,将计算结果与实验结果相结合,探讨了钴卟啉分子前线轨道能级与其催化活性之间的关系.经研究发现,四配位或五配位钴卟啉催化剂的催化活性与E_HOMO和ΔE_L-H均有一定的相关性,且ΔE_L-H对催化活性的影响大于E_HOMO对催化活性的影响;EHOMO值越低、ΔE_L-H越小,其催化活性越高.     

Preparation of heterogeneous cationic metalloporphyrin/heteropolyanion composite catalysts and their high catalytic activity in hydroxylation of cyclohexane with molecular oxygen

A new route to improve the metalloporphyrin catalysts is developed, and it is to constitute heterogeneous composite catalysts with immobilized cationic metalloporphyrins and heteropolyanions. By using the method of synchronously synthesizing and immobilizing porphyrins on cross-linked polystyrene microspheres (CPS microspheres), the immobilized porphyrin TAPP-CPS microspheres, on which ternary amine (TA) group-containing phenyl porphyrin (PP) was immobilized, were first prepared, and then the immobilized cationic porphyrin TMPP-CPS microspheres, in whose structure trimethylammoniophenyl porphyrin (TMPP) was contained, were obtained via quaternization reaction. Finally, three immobilized metalloporphyrins, CoTMPP-CPS (shorten as CoP-CPS), MnTMPP-CPS (MnP-CPS) and FeTMPP-CPS (FeP-CPS), were gained through coordination reactions. These immobilized metalloporphyrins were composited with heteropolyanions by right of the mutual electrostatic interaction with phosphotungstic (PW) acid and phosphomolybdic (PMo) acid as reagents, respectively, resulting in several heterogeneous metalloporphyrin/heteropolyanion composite catalysts such as CoPPW-CPS, CoPPMo-CPS and MnPPW-CPS. The composite catalysts were used in the catalytic hydroxylation reaction of cyclohexane with molecular oxygen as oxidant, and their catalytic performances were investigated. The experimental results show that the heterogeneous composite catalysts have extraordinarily high catalytic activity in the hydroxylation reaction of cyclohexane by molecular oxygen, and the cyclohexanol yield in 8 h can get up to 45.5 %. More importantly, the catalytic activity of the heterogeneous composite catalysts is obviously higher than that of the immobilized cationic metalloporphyrins, and the enhanced catalytic activity is originated from a protection of heteropolyanions against the deactivation of metalloporphyrins.     

Catalytic activity and stability of anionic and cationic water soluble cobalt(II) tetraarylporphyrin complexes in the oxidation of 2-mercaptoethanol by molecular oxygen

The catalytic activity and stability of anionic cobalt(II) porphyrin complexes: 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinatocobalt(II), 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5disulfonatophenyl)porphyrinatocobalt(II) and the cationic cobalt(II) porphyrin: 5,10,15,20-tetrakis[4-(diethylmethylammonio)phenyl]porphyrinatocobalt(II) tertraiodide have been investigated in the oxidation of 2-mercaptoethanol by dioxygen. All complexes were efficient catalysts for the auto-oxidation of 2-mercaptoethanol. The cationic cobalt(II) porphyrin has been found to be the most reactive catalyst. The rate of auto-oxidation of 2-mercaptoethanol catalysed by 5,10,15,20-tetrakis(2,4,6-trimethyl-3,5disulfonatophenyl)porphyrinatocobalt(II) has been found to increase with increasing the pH from 7 to 9 then decreased at higher pH. The rate constants of auto-oxidation reaction showed linear dependence on catalyst concentration and saturation kinetics in both 2-mercaptoethanol concentrations and dioxygen pressure. Anionic cobalt(II) porphyrin complexes showed higher stability than the cationic catalyst in repeat oxidation reactions. Immobilizing the anionic catalysts on ion exchange resin and supporting the cationic catalyst on clay mineral montmorillonite improved their stabilities towards oxidation.     

Synchronously synthesizing and immobilizing porphyrins on crosslinked polystyrene microspheres and preliminary study on catalytic activity of supported metalloporphyrins

A novel method for immobilizing porphyrins as well as metalloporphyrins (MPs) on polymeric supports was found, and it is the way to synchronously synthesize and immobilize porphyrins on polymeric microspheres. By using 4‐hydroxybenzaldehyde (HBA)‐bound crosslinked polystyrene (CPS) microspheres, pyrrole, and benzaldehyde in a solution as co‐reactants and through the Adler's reaction between solid–liquid phases, it was successfully realized to simultaneously synthesize and immobilize phenyl porphyrin (PP) on CPS microspheres, resulting in PP‐supported microspheres PP–CPS. With the same method, substituted PPs, 4‐chlorophenyl porphyrin (CPP) and 4‐nitrophenyl porphyrin (NPP), were also successfully immobilized on CPS microspheres by using substituted benzaldehydes, 4‐chlorobenzaldehyde and 4‐nitrobenzaldehyde, as one reactant in the solution, respectively, and other two porphyrin‐supported microspheres, CPP–CPS and NPP–CPS, were obtained. The effects of various factors on the process of synchronously synthesizing and immobilizing porphyrins on CPS microspheres were mainly studied. Further, the coordination reaction of cobalt salt with PP–CPS as well as CPP–CPS and NPP–CPS was conducted, forming three solid catalysts, CoPP–CPS, CoCPP–CPS, and CoNPP–CPS. The catalytic properties of these catalysts in the catalytic oxidation of ethylbenzene to acetophenone by dioxygen were preliminarily examined. The experimental results indicate that the Adler's reaction between solid–liquid phases, namely the reaction between HBA‐bound CPS microspheres and pyrrole as well as free benzaldehyde or analogs in the solution can favorably be carried out. For this process, the fitting protonic acid catalyst is p‐nitrobenzoic acid and appropriate solvent is dimethyl sulfoxide (DMSO). By comparison, the process of preparing CPP–CPS microspheres is easier to be carried out. The obtained three solid catalysts can effectively catalyze the oxidation of ethylbenzene to acetophenone by dioxygen. In comparison, the catalytic activity of CoNPP–CPS is the highest. Copyright © 2009 John Wiley & Sons, Ltd.     

Highly Active Catalysis of Cobalt Tetrakis(pentafluorophenyl)porphyrin Promoted by Chitosan for Cyclohexane Oxidation in Response-Surface-Methodology-Optimized Reaction Conditions

We aimed at elevating catalytic performances of cobalt tetrakis(pentafluorophenyl)porphyrin (Co TPFPP) through axial coordination, nanocavities, and covalently grafting action. The Co TPFPP was immobilized onto nanoporous and nonporous chitosan, forming Co TPFPP/np- and nonp-CTS catalysts, respectively. The catalysts were characterized by various spectroscopic techniques. The catalytic performances of these catalysts for cyclohexane oxidation under response-surface-methodology-optimized oxidation reaction conditions were estimated and compared. Co TPFPP/np-CTS was an excellent catalyst at aspect of catalytic activity, exhibiting the considerable potential reusability, 24.2 mol % yields (KA oil : cyclohexanone and cyclohexanol) in average, and total turnover frequencies (TOFs) of 3.25×10⁶ h⁻¹. This is attributed to the structural characteristics of the Co TPFPP/np-CTS catalyst: the cobalt porphyrin molecules could be highly scattered on CTS, forming the independent active sites, and were not leached. The axial coordination exerted the most important effect on the catalytic activity, and the covalent grafting action had a decisive effect on the increase of the total TOFs and on the reusability of the catalyst.     

Co4HP2Mo15V3O62的合成及其催化乙苯氧化反应性能

合成了一系列Dawson型磷钼钒钴杂多酸盐Co<,n> H<,9-2n>P<,2>Mo<,15>V<,3>O<,62>(n=1-4),用傅立叶变换红外光谱表征了磷钼钒钴的结构.以乙苯为原料、H<,2>O<,2>为氧化剂、磷钼钒钴杂多酸盐为催化剂催化氧化乙苯制备苯乙酮.考察了催化剂种类及用量、助剂用量、H<,2>O<,2...     

Crystal structure of meso‐substituted pyrazolyl porphyrin complexes and their highly active catalyst for oxidation of alkylbenzenes

During the past few years, a great deal of effort has been devoted to the anchoring of catalytic oxidation. In this work, three new catalysts CuPp, MnPp and ZnPp by solvothermal methods with 5, 10, 15, 20‐tetrakis(4‐N‐pyrazolyl)‐phenyl porphyrin (H₂Pp) and the corresponding metal salts have been synthesized and structurally characterized. The single crystal structures determined by X‐ray diffraction show the bond distances of M‐N in porphyrin cores determined the conformation of porphyrin rings. We explored the catalytic activity of CoPp, CuPp, MnPp and ZnPp for oxidation of alkylbenzenes. The experimental results display these products exhibit high catalytic activities and selectivities for oxidation of ethylbenzene to acetophenone, and can be reused by filtration without appreciable decrease in catalytic activity and selectivity.     

Hydroxylation of cyclohexane with molecular oxygen catalyzed by highly efficient heterogeneous Mn(III) porphyrin catalysts prepared by special synthesis and immobilization method

A novel method to synthesize and immobilize porphyrins as well as manganese porphyrins on crosslinked polystyrene (CPS) microspheres was designed. The chloromethyl groups of chloromethylated CPS microspheres (CMCPS microspheres) were first oxidized to aldehyde groups via Kornblum oxidation reaction, obtaining aldehyde group-functionalized microspheres, and then, the synchronous synthesis and immobilization of porphyrins on CPS microspheres were carried out via the Adler reaction between solid–liquid phases, obtaining three kinds of functional microspheres, on which phenyl porphyrin (PP), p-chlorophenyl porphyrin (CPP) and p-nitrophenyl porphyrin (NPP) were immobilized. Finally, three manganese porphyrin-immobilized microspheres, MnPP–CPS, MnCPP–CPS and MnNPP–CPS, were prepared, these solid catalysts were used in the catalytic hydroxylation reaction of cyclohexane with molecular oxygen as oxidant, and their catalytic performances were mainly investigated in this work. Some surprising experimental results were obtained. The prepared immobilized manganese porphyrin catalysts display amazing catalytic activity and selectivity, and cyclohexane conversion can get up to 45?% and cyclohexanol selectivity in the reaction product can be up to 90–100?%.     

Highly active and reusable catalyst for fries rearrangement of phenyl acetate

Silica-12-tungstophosphoric acid core-shell nanoparticles were prepared by sol-gel method followed by steaming. The catalytic activity of fresh and steamed catalysts was studied in Fries rearrangement of phenyl acetate. The reaction parameters, such as catalyst loading and reaction temperature, were optimized. The structural properties of the prepared catalysts were analyzed by X-ray diffraction and transmission electron microscopy techniques. The nature and strength of acid sites in the catalysts were analyzed by pyridine adsorption followed by infrared spectroscopy and differential scanning calorimetry measurements. The XRD and TEM analyses confirm the formation of silica-12-tungstophosphoric acid core-shell nanoparticles during steaming process. Acidity measurement indicates that both fresh and steamed catalyst samples carry weak acid sites and Brøsted acid sites. In addition, the steaming of heteropoly acid contained silica enhances the strength of Brøsted acid sites. The catalytic activity of fresh as well as steamed catalysts in liquid-phase Fries rearrangement showed that the steam treated sample exhibits higher conversion and selectivity to the desired product compared to the fresh catalyst sample. The higher activity of steam treated catalysts has been explained in terms of surface acidity of the catalysts. Reusability of the steamed catalyst shows that there is no appreciable change either in the conversion rate or product selectivity.     

Performance of a biomimetic oxidation catalyst immobilized on silicon wafers: comparison with its gold congener

With the aim of extending the usefulness of an existing biomimetic catalytic system, cobalt porphyrin catalytic units with thiol linkers were heterogenized via chemical grafting to silicon wafers and utilized for the catalytic oxidation of hydroquinone to p-benzoquinone. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and composition of the heterogeneous catalyst. The results of the catalytic oxidation of hydroquinone obtained with porphyrins grafted on silicon were compared with those obtained earlier with the same catalyst in homogeneous phase and immobilized on gold. It was found that the catalysis could run over 400 h, without showing any sign of deactivation. The measured catalytic activity is at least 10 times higher than that measured under homogeneous conditions, but also 10 times lower than that observed with the catalytic unit immobilized on gold. The reasons of this discrepancy are discussed in term of substrate influence and overlayer organization. The silicon-immobilized catalyst has potential as an advanced functional material with applications in oxidative heterogeneous catalysis of organic reactions, as it combines long-term relatively high activity with low cost.     

Selective oxidation of sulfide catalyzed by peroxotungstate immobilized on ionic liquid-modified silica with aqueous hydrogen peroxide

Two kinds of catalysts of peroxotungstates immobilized on ionic liquid-modified silica have been synthesized and characterized. By comparing with other heterogeneous catalysts, the most characteristic of these heterogeneous catalysts is the catalyst formed from the combination of catalytic active center peroxotungstate with an ionic liquid. Thereinto, ionic liquid-modified supported catalysts provide the hydrophobic environment for organic reactions. We presume that the heterogeneous catalyst would display excellent catalytic ability depending on the additive effect of an ionic liquid and peroxotungstate. Their catalytic properties in oxidation of sulfides to sulfoxides and sulfones were investigated with 30% aqueous hydrogen peroxide at room temperature. These recoverable catalysts both exhibit high catalytic activities in the oxidation reaction of sulfoxides and provide excellent chemselectivities towards sulfur groups with unsaturated double bonds when the aqueous hydrogen peroxide was greatly in excess. The yields of methyl phenyl sulfoxide were still satisfied when the catalyst was reused for a sixth time.