双亲性磁性纳米材料制备及应用研究

【作者】 崔新爱；

【导师】 胡道道；

【作者基本信息】 陕西师范大学 ， 化学工艺， 2008， 硕士

【摘要】 近年来,有关两相催化的研究受到了人们的极大关注,但涉及两相催化反应的应用领域特别广泛,且不同反应体系间存在一定的差异性,因此,有目的的研究具有重大应用价值的两相催化反应对于解决实际问题不仅具有重要意义,而且具有重要的理论价值。当今国内外研究都以深度脱硫满足严格的燃料油尾气新排放标准及燃料电池的无硫化为研究目的。目前两相催化过氧化氢氧化深度脱硫被公认为最具发展前景的方法之一,结合燃料油脱硫是一个典型的两相催化反应体系,根据两相催化过氧化氢氧化深度脱硫的基本原理,本研究提出,通过具有催化活性的磷钨酸(H₃PW₁₂O₄₀与负载于磁性纳米二氧化硅球表面的两种疏水性季铵盐发生离子交换作用,构筑两相催化微反应器。旨在有效提高过氧化氢氧化效率的同时,解决产品难于纯化、催化剂难于回收和再利用问题。更重要的是,通过本研究实施为建立具有普遍适应性的两相催化微反应器的构筑方法及其应用奠定基础。依据上述目的。本研究主要包括以下两个方面:（一）采用油包水型反相微乳液体系制备得到磁性纳米二氧化硅（MSN）。以MSN作为载体,利用嫁接法和离子交换作用制备多功能微反应器PWO/AEM/MSN和PWO/AcrH⁺/MSN。（1）反相微乳液法制备MSN在甲苯、水、十六烷基三甲基溴化铵三者组成的油包水型微乳液体系中,Fe²⁺和Fe³⁺在NH₃·H₂O存在的条件下,在水核内共沉淀生成Fe₃O₄。TEOS在过量氨水存在下,在油水界面水解缩合生成SiO₂。利用高分辨透射电镜、能谱仪、X射线衍射仪和振动样品磁强计等测定手段对其形貌和组成进行表征。结果表明:此磁性纳米二氧化硅是以赤铁矿Fe₃O₄为核,无定型二氧化硅为壳的核/壳型多功能材料,呈球形,粒径约为40nm。此材料具有分散性好,粒度均匀,比表面积大,超顺磁性等优点,是一种优良的催化剂载体。（2）利用后嫁接法和离子交换作用合成PWO/AEM/MSN和PWO/AcrH⁺/MSN两种微反应器以反相微乳液法制得的磁性纳米二氧化硅作为载体,利用后嫁接法将两种不同的疏水性季铵盐固定于二氧化硅表面,制得烷基季铵盐/磁性二氧化硅和吖啶季铵盐/磁性二氧化硅两种复合材料,再利用固载后的季铵盐基团与磷钨酸阴离子之间的离子交换作用,制得目标复合微球PWO/AEM/MSN和PWO/AcrH⁺/MSN。利用接触角测定仪、红外光谱仪、热重分析仪、扫描电子显微镜及能谱仪等多种手段对两种微反应器的表面形貌和组成进行了表征。研究结果表明:两种制备方法都已经成功地将磷钨酸负载于二氧化硅表面。而且可通过改变季铵盐的固载量,调节微反应器的表面亲水,疏水性（即在油水两相的分散情况）和磷钨酸的固载量,从而制得了不同性质的微反应器。（二）以二苯并噻吩（DBT）的十氢萘溶液为反应模型,以30%H₂O₂为氧化剂,乙腈和水的共沸物为萃取剂,研究了该系列催化剂对二苯并噻吩（DBT）的催化氧化性能。PWO/AEM/MSN作微反应器的脱硫研究中,根据微反应器AEM固载量的不同,分别采用乙醇引入和超声引入两种方式将双氧水引入至微反应器表面。结果表明:无论采用何种方式,此两相微反应器均表现出良好的催化氧化脱硫效率。微反应器PWO/AcrH⁺/MSN在DBT氧化的过程中也显示了一定的催化效果,实验条件有待于进一步讨论。这两种微反应器均可通过外磁场从体系中分离出来而不需要任何溶剂。以上研究结果表明该实验已初步达到了预设的研究目的。更多还原

【Abstract】 Recently,the study of biphasic catalysis has attracted wide interest.Although different biphasic catalyses have been widely studied,it is still important to construct universal method for biphasic catalysis in that the systems of biphasic catalysis reactions possess certain differences and extensive application.A new protocol was proposed to construct a structural microreactor used in ultra-deep desulfurization of fuel oil by H₂O₂ oxidation,which is based on:（1）ultra-deep desulfurization of fuel oil by H₂O₂ oxidation is a typical biphasic catalysis;（2）ultra-deep desulfurization was requested internationally extensively because of environmental protection purposes;（3）using H₂O₂ as oxidiant in ultra-deep desulfurization of fuel oil was widely focused on.The purpose of constructing of the structural microreactor is to overcome some defects in biphasic catalysis.The structural microreactor can overcome the difficulties in the process of separation and recovery of the catalysts of the emulsion-based biphasic catalysis.To achieve the goal,two novel composite microspheres were synthesized by ion exchange reaction between H₃PW₁₂O₄₀ and two hydrophobic quaternary ammonium groups loaded on the MSN.According to the objects above mentioned,the main contents of this research include two aspects are as follows:1.PWO/AEM/MSN and PWO/AcrH⁺/MSN composite microspheres were prepared using the magnetic silica nanoparticles（MSN） as the carrier.（1）Magnetic silica nanospheres were synthesized by a water-in-oil microemulsion technique（toluene/H₂O/CTAB）.Fe²⁺and Fe³⁺ with NH₃·H₂O co-precipitate inside the emulsion droplets gave magnetite precipitates.The TEOS was added slowly to the mixture,again under a nitrogen atmosphere.Follow that the catalyzed hydrolysis/condensation of the TEOS at the water/oil interface was happened because of the high pH.The morphology and composition of MSN were characterized by the HR-TEM,EDX,XRD and VSM,respectively.It was demonstrated that the magnetic silica nanoparticles possess a core-shell structure with the core of magnetite Fe₃O₄ phase and a shell of silica.The global Particles obtained had diameters about 40 nm.The synthesized iron oxide nanoparticles display strong magnetization,high specific surface area,and desirable superparamagnetic properties which are essential as the prime criterion as a magnetic carrier.（2）PWO/AEM/MSN and PWO/AcrH⁺/MSN composite microreactors were prepared by following method.Firstly,using post-synthetic grafting method to covalenfly link organosilane species with surface silanol groups,two different hydrophobic quaternary ammoniums were immobilized onto MSN surface.We obtained AEM/MSN and AcrH⁺/MSN.Secondly, PWO/AEM/MSN and PWO/AcrH⁺/MSN were constructed by ion-exchange between quaternary ammoniums loaded on the surface of MSN and H₃PW₁₂O₄₀.The morphologies and compositions of the two microreactors were characterized by Optical Contact Angle Measuring Device,Scanning Electron Microscopy（SEM）,EDX,Thermogravimetric Analysis（TGA）,Fouier Transform Infrared Spectroscopy（FT-IR）,respectively.The results indicate that phosphotungstic acid had been immobilized on MSN surface successfully through two prepared process.And we can tailor the surface hydrophobic/hydrophilic properties and PWO content of two composite microreactors via adjusting the density of the immobilized quaternary ammoniums.2.For a model reaction run,dibenzothiophene（DBT） was dissolved in decahydronaphthalene. 30%H₂O₂ as oxidant and PWO/AEM/MSN or PWO/AcrH⁺/MSN two composite microspheres as catalyst,the DBT was oxidated into the corresponding sulfone.Then the mixture was extracted by acetonitrile and water.In the system using PWO/AEM/MSN as microreactor,according to difference between dosages of AEM mobilized on composite material（PWO/AEM/MSN）,two methods were used to introduce H₂O₂ onto the surface of magnetic microreactors.The results indicate that the composite material used as microreactor has excellent performences in ultra-deep desulfurization,whatever method was used.In the system using PWO/AcrH⁺/MSN as microreactor,the results indicate that the microreactor is efficient on DBT oxidation.Meanwhile,the microreactors were recycled under a magnetic field but no organic solvent involved.From above results,the microreactors constructed meet the purpose proposed.更多还原