大比表面负载氧化铁的氧化硅层柱磷酸锆制备和 催化性能研究

提出了一种以氧化硅层柱磷酸锆(SiO~2-ZrP)的前驱体,氨丙基硅酸酯嵌入磷酸锆(APS-ZrP)为载体制备负载氧化铁的氧化硅层术磷酸锆的新方法。与传统方法相比,新方法制得的样品具有较大的比表面和孔容。X射线粉末衍射(XRD)和程序升温还原(TPR)的结果表明采用新方法有利于氧化铁在载体表面的高度分散,分散阈值为0.25gFe~2O~3/g(SiO~2-ZrP),远超过直接以SiO~2-ZrP为载体浸渍草酸铁铵的传统方法得到样品。同时,用新方法制得的氧化铁催化剂表现了较高的乙苯脱氢活性,是一类值得研究的催化材料。     

Zn助剂对铁基催化剂费托合成制低碳烯烃性能的影响

低碳烯烃(C2=–C4=)是十分重要的基础化工原料,目前主要采用热裂解或催化裂解石脑油、蜡油等工艺路线生产。近年来,针对全球范围的石油危机及我国富煤贫油这一基本的国情,以煤、天然气(页岩气)和生物质等丰厚的碳资源,经合成气制取低碳烯烃的工艺路线备受关注。其中,合成气经由甲醇或二甲醚间接制取烯烃技术(MTO/MTP)已经工业化;与之相比,费托合成直接生产低碳烯烃(FTO)工艺流程短、投资和操作费用低,具有良好的工业发展前景。目前,费托合成催化剂活性组分的研究主要集中于Fe, Co, Ni和Ru等元素,其中Fe基催化剂具有较高低碳烯烃选择性、较低甲烷选择性和制造廉价等优势,更适合于FTO反应。最近,人们大多聚焦于对负载型铁基催化剂的研究,但传统非负载型铁催化剂由于其制备简单、价格低廉,仍然具有巨大的开发前景。近来,我们组报道了采用微波水热法制备的Zr助剂改性Fe-Zr催化剂应用于CO加氢研究,提高了催化剂的活性,与传统Mn改性铁基催化剂相比, CO2选择性明显降低。目前,已有研究小组对Zn助剂提高铁基催化剂烯烃选择性进行报道,但反应过程中的严重积碳问题却少有研究。我们在Fe-Zr催化剂的基础上,进一步研究了Zn助剂在提高铁基催化剂低碳烯烃选择性、改善产物分布和降低反应过程积碳方面的作用。
　　我们分别采用微波水热法和浸渍法对铁基催化剂进行了Zn改性,并将其用于费托合成制取低碳烯烃反应。运用扫描电镜(SEM)、X射线衍射(XRD)、N2物理吸附(BET)、H2程序升温还原(H2-TPR)和X射线光电子能谱(XPS)技术手段对催化剂的物理和化学性质进行了表征。结果表明,两种方法改性后的铁基催化剂具有高低碳烯烃选择性和稳定性,重质烃(C5+)含量降低,且保持低CO2选择性。此外,采用两种方法Zn改性的铁基催化剂展现出了不同的特性。 XRD结果表明,反应前两种方法制备的样品α-Fe2O3物相晶粒大小均为15–18 nm,反应后浸渍法制备的样品对应物相(ZnFe2O4)晶粒大小约为25 nm、而微波水热法制备的样品约为20 nm,说明微波水热法改性的催化剂有效分散了Fe活性组分; H2-TPR结果显示,两种Zn助剂加入方法对催化剂Fe组分的还原行为有不同程度影响,体现了活性组分间不同的相互作用; XPS结果表明, Zn助剂改变了催化剂Fe活性位的化学性质,在微波水热法制得催化剂的表面Zn含量更低、分散度更高,而Zn助剂的加入对Zr组分没有明显影响。所有催化剂经200 h在线活性测试后,采用传统浸渍法制备的催化剂表面有大量积碳生成;而采用微波水热改性铁基催化剂积碳量明显减少,表现出更高的催化活性与稳定性。     

Zn助剂对铁基催化剂费托合成制低碳烯烃性能的影响（英文）

低碳烯烃(C_2~=–C_4~=)是十分重要的基础化工原料,目前主要采用热裂解或催化裂解石脑油、蜡油等工艺路线生产.近年来,针对全球范围的石油危机及我国富煤贫油这一基本的国情,以煤、天然气(页岩气)和生物质等丰厚的碳资源,经合成气制取低碳烯烃的工艺路线备受关注.其中,合成气经由甲醇或二甲醚间接制取烯烃技术(MTO/MTP)已经工业化;与之相比,费托合成直接生产低碳烯烃(FTO)工艺流程短、投资和操作费用低,具有良好的工业发展前景.目前,费托合成催化剂活性组分的研究主要集中于Fe,Co,Ni和Ru等元素,其中Fe基催化剂具有较高低碳烯烃选择性、较低甲烷选择性和制造廉价等优势,更适合于FTO反应.最近,人们大多聚焦于对负载型铁基催化剂的研究,但传统非负载型铁催化剂由于其制备简单、价格低廉,仍然具有巨大的开发前景.近来,我们组报道了采用微波水热法制备的Zr助剂改性Fe-Zr催化剂应用于CO加氢研究,提高了催化剂的活性,与传统Mn改性铁基催化剂相比,CO_2选择性明显降低.目前,已有研究小组对Zn助剂提高铁基催化剂烯烃选择性进行报道,但反应过程中的严重积碳问题却少有研究.我们在Fe-Zr催化剂的基础上,进一步研究了Zn助剂在提高铁基催化剂低碳烯烃选择性、改善产物分布和降低反应过程积碳方面的作用.我们分别采用微波水热法和浸渍法对铁基催化剂进行了Zn改性,并将其用于费托合成制取低碳烯烃反应.运用扫描电镜(SEM)、X射线衍射(XRD)、N_2物理吸附(BET)、H_2程序升温还原(H_2-TPR)和X射线光电子能谱(XPS)技术手段对催化剂的物理和化学性质进行了表征.结果表明,两种方法改性后的铁基催化剂具有高低碳烯烃选择性和稳定性,重质烃(C_5~+)含量降低,且保持低CO_2选择性.此外,采用两种方法 Zn改性的铁基催化剂展现出了不同的特性.XRD结果表明,反应前两种方法制备的样品α-Fe_2O_3物相晶粒大小均为15–18 nm,反应后浸渍法制备的样品对应物相(ZnFe_2O_4)晶粒大小约为25 nm、而微波水热法制备的样品约为20 nm,说明微波水热法改性的催化剂有效分散了Fe活性组分;H_2-TPR结果显示,两种Zn助剂加入方法对催化剂Fe组分的还原行为有不同程度影响,体现了活性组分间不同的相互作用;XPS结果表明,Zn助剂改变了催化剂Fe活性位的化学性质,在微波水热法制得催化剂的表面Zn含量更低、分散度更高,而Zn助剂的加入对Zr组分没有明显影响.所有催化剂经200 h在线活性测试后,采用传统浸渍法制备的催化剂表面有大量积碳生成;而采用微波水热改性铁基催化剂积碳量明显减少,表现出更高的催化活性与稳定性.     

一种改进的脱水方式对费托合成铁基催化剂结构性质与催化性能的影响

研究了一种改进的脱水方式对费托(F-T)合成铁基催化剂结构性质与催化性能的影响.在n(H2)/n(CO)=0.67,WHSV=1000 h-1,p=1.5 MPa和t=250 ℃的条件下对催化剂进行了浆态床F-T合成反应性能评价实验,并采用低温N2物理吸附、X射线衍射、原子发射光谱、X射线光电子能谱、氨程序升温脱附、穆斯堡尔谱和高分辨透射电镜等技术对催化剂进行了表征.结果表明,水处理和二次干燥得到的催化剂比表面积增加,颗粒减小,铁氧化物的分散程度增大,其表面的SiO2/Fe比例明显减小;该催化剂F-T合成反应活性有所增加;表面酸性有所增强,导致烃产物选择性向低碳数方向偏移.     

Fe/SiO_2纳米复合物上合成气制低碳烯烃催化性能研究

分别采用一步合成法和常规共沉淀法制备了Fe/SiO2催化剂,通过N2物理吸附、X射线衍射、透射电镜、傅里叶变换红外光谱和程序升温还原等方法对催化剂进行了表征,并在固定床反应器中对其费托合成制低碳烯烃的催化性能进行了评价。结果表明,与共沉淀铁基催化剂不同,采用一步合成法制备的纳米复合物主要由Fe3O4相构成,形貌呈规则球形,平均粒径为30 nm,尺寸分布窄,更容易还原。一步合成法制得的Fe/SiO2催化剂对费托合成反应具有较高的活性和低碳烯烃选择性、较低的甲烷选择性和良好的稳定性。     

液固相水热法制备氧化硅纳米线

利用液固相水热反应方法, 以硅溶胶为硅源, 在三价铁辅助下与乙二胺的水溶液在180 ℃反应4 d后生成具有P21212空间群结构的单晶氧化硅纳米线. 用扫描电子显微镜、透射电子显微镜和多晶X射线衍射对制备的样品进行了表征, 系统研究了有机胺、金属盐、反应时间及反应温度等条件对氧化硅纳米线生长的影响. 结果表明, 随着有机胺碳链的增长, 产物形貌逐渐由纳米线转变为纳米片; 金属阳离子的存在对纳米线形貌有较大的影响, 而阴离子的存在并不影响纳米线的生成; 过低的铁含量导致反应进行不完全, 而过多的铁盐加入则会导致反应中剩余铁氧化物吸附到氧化硅纳米线表面, 进而影响到产物纯度; 反应时间延长及反应温度的提高都有利于氧化硅纳米线的生长. 最佳反应条件为: 有机胺为乙二胺, 硝酸铁为铁源, 硅溶胶为硅源, 硅/铁摩尔比为1∶0.4, 乙二胺与水的体积比为8∶5, 温度为180 ℃.     

介孔氧化硅球负载钴基催化剂在费托合成中的应用

以介孔氧化硅空心球(HMSS)为载体, 采用双溶剂法浸渍硝酸钴溶液制备了高分散度的钴催化剂, 并表征了催化剂中Co3O4颗粒的负载情况和费托(F-T)反应性能. 结果表明: Co3O4颗粒在介孔硅球孔道内形成100～200 nm左右分散良好的簇团, 将催化剂压碎和刻蚀后的透射电子显微镜(TEM)证实, 这些簇团是由尺寸约为10～15 nm大小均匀的Co3O4单分散颗粒组成, 这些单分散颗粒锚定在介孔硅球孔道内, 彼此之间被相邻孔壁隔开; 催化剂中钴-硅作用很弱, 在600 K下即可被还原; F-T反应评价表明, 所得产物保持了良好的烃分布, 主要集中于C5～C18烃, 选择性在60%左右, C5＋选择性达到80%以上.     

碳纳米管担载CuCoCe催化剂催化合成气制低碳醇的性能

以碳纳米管为载体,采用等体积浸渍法制备了一系列Cu Co Ce催化剂,考察了碳纳米管长度及羧基官能团对该系列催化剂催化合成气制低碳醇反应性能的影响;采用X射线衍射(XRD)、氮气吸附-脱附、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等手段对催化剂进行了结构和性能表征.实验结果表明,以含有羧基官能团的、长度为0.5~2μm的碳纳米管为载体时,催化剂的低碳醇时空收率最高,达到783.72mg·gcat-1·h-1,醇产物中C2+醇选择性达到82.71%.研究结果表明,短纳米管有利于活性金属进入碳纳米管内部,并促使活性组分分散均匀,这对CO转化率和低碳醇时空收率的提高有显著作用;碳纳米管上羧基官能团的存在促进了金属与金属、金属与载体之间的相互作用,从而使醇产物中C2+醇选择性明显提高.     

费托合成:SiO_2和Al_2O_3负载的Co_2C催化剂的表征和评价

采用CO碳化SiO2和Al3O4负载的Co(NO3)2的方法制备了SiO2和Al3O4负载的Co2C催化剂,采用N2物理吸附、X射线衍射和H2-程序升温还原技术对催化剂进行了表征,并用于催化费托合成反应中.结果显示,需要较长碳化时间才可合成负载的Co2C催化剂;所制催化剂表现出CO加氢生成高碳醇的催化性能,其原因可能在于催化剂表面存在的金属Co物种使CO解离,表面Co物种有利于CO插入,从而导致醇的生成,但体相Co2C则不具有催化活性.     

硅对铁基费-托合成催化剂的影响

用共沉淀法制备了一系列不同硅含量的铁基催化剂,采用N2吸附和原位X射线衍射对催化剂进行了表征,在固定床反应器中考察了催化剂的费-托合成反应活性、选择性和稳定性.结果表明,含硅的催化剂具有较大的比表面积和较小的平均孔径,在CO还原及费-托合成反应中生成的碳化铁物种的稳定性比不含硅的催化剂高.在费-托合成反应中,不含硅的催化剂具有较高的初始活性,但易失活;含硅的催化剂具有较低的初始活性,但稳定性较高.Fe7C3是活性最高的碳化铁物种.随着硅含量的增加,催化剂的费-托合成反应更易生成低碳数产物.     

Pt/Fe双金属Fischer-Tropsch催化剂的设计、合成及表征

利用强静电吸附(SEA)理论,根据Fe2O3与SiO2表面不同的零电荷点(PZC),将铂盐溶液pH值调控后浸渍在Fe2O3/SiO2的载体上,制备出Pt/Fe双金属Fischer-Tropsch(F-T)催化剂,通过N2吸脱附技术、X射线衍射(XRD)、扫描投射电镜(STEM)和X射线能量散射谱(EDS)对催化剂的结构、形貌及组成进行表征.结果表明浸渍过程中PtCl62-离子定向选择性地吸附在Fe2O3表面,而非SiO2表面.与传统浸渍(IW)法制备的催化剂比较,Pt与Fe紧密结合在一起,还原后形成高度分散均一的纳米颗粒,粒径尺寸在2 nm左右.以F-T合成反应作为模型反应对催化活性进行表征,强静电吸附法合成的催化剂表现出优异的催化性能,反应进行150 h后CO转化率仍保持在51%以上.     

Synthesis of Fe3O4@SiO2-Au/Cu magnetic nanoparticles and its efficient catalytic performance for the Ullmann coupling reaction of bromamine acid

Over bimetallic Au/Cu catalyst supported on magnetic Fe₃O₄ nanoparticles, water-mediated bromamine acid could be selectively converted into 4,4'-diamino-1,1'-dianthraquinonyl-3,3'-disulfonic acid (DAS) with a yield of 88.67%. The magnetic catalyst could be readily separated and reused.     

A new strategy for fabrication Fe2O3/SiO2 composite coatings on the Ti substrate

We report here on the synthesis of homogenous, well-adherent composite film of Fe₂O₃/SiO₂, up to 7 μm thick, on the titanium substrate by anodic treatment optimized for an aqueous suspension of K₂O·SiO₂ and Fe₂O₃ powder under galvanostatic conditions. The end products were characterized by scanning electron microscopy, energy-dispersive X-ray, X-ray powder diffractometry, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy, concluding that the formation of composite coating at the SiO₂ to Fe₂O₃ ratio of approximately 1:1 proceeds just after formation of a thin TiO₂ layer with Fe₂O₃ particle inclusions without transformations via an electrophoresis deposition of negatively charged Fe₂O₃ species enveloped by silica ions.     

Magnetic methylene-based mesoporous organosilica composite-supported IL/Pd: a powerful and highly recoverable catalyst for oxidative coupling of phenols and naphthols

A novel magnetic methylene-based mesoporous organosilica composite-supported IL/Pd complex (Fe₃O₄@MePMO-IL/Pd) was synthesized and characterized, and its catalytic performance was investigated. The preparation of the Fe₃O₄@MePMO composite was achieved through coating of Fe₃O₄ nanoparticles with a mixture of tetramethoxysilane, bis(triethoxysilyl)methane, and (3-chloropropyl)-trimethoxysilane in the presence of cetyltrimethylammonium bromide surfactant. The Fe₃O₄@MePMO was then modified with alkyl imidazolium ionic liquid and palladium species to deliver the Fe₃O₄@MePMO-IL/Pd nanocatalyst. This catalyst was characterized using Fourier transform infrared, thermal gravimetric, wide-angle powder X-ray diffraction, low-angle powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer, energy-dispersive X-ray, and nitrogen adsorption–desorption analyses. The Fe₃O₄@MePMO-IL/Pd was effectively used as a highly recoverable and durable catalyst for the selective oxidative coupling of phenols and 2-naphthols under aerobic conditions.     

Generation of sulfate radicals by supported ruthenium catalyst for phenol oxidation in water

In this study we report the preparation of RuO₂/Fe₃O₄@nSiO₂@mSiO₂ core–shell powder mesoporous catalyst for heterogeneous oxidation of phenol by peroxymonosulfate (PMS) as oxidant. The properties of this supported catalyst were characterized by SEM–EDS (scanning electron microscopy–energy dispersive X-ray spectroscopy), XRD (powder X-ray diffraction), TEM (transmission electron microscopy), and nitrogen adsorption–desorption. It is found that using ruthenium oxide-based catalyst is highly effective in activating PMS for related sulfate radicals. The effects of catalyst loading, phenol concentration, PMS concentration, reaction temperature, and reusability of the as-prepared catalyst on phenol degradation were investigated. In RuO₂/Fe₃O₄@nSiO₂@mSiO₂ mesoporous catalyst, Oxone (PMS) was effectively activated and 100 % phenol degradation occurred in 40 min. The magnetic RuO₂/Fe₃O₄@nSiO₂@mSiO₂ catalyst was facility separated from the solution by an external magnetic field. To regenerate the deactivated catalyst and improve its catalytic properties, three different methods involving annealing in air, washing with water, and applying ultrasonics were used. The catalyst was recovered thoroughly by heat treatment.     

Surface Modification of a Magnetic SiO2 Support and Immobilization of a Nano-TiO2 Photocatalyst on It

This study presented an effective method to modify the surface chemical reactivity of a SiO₂/Fe₃O₄ support. The unmodified SiO₂/Fe₃O₄ support was prepared by the hydrolysis and condensation of tetraethoxysilane on the surface of hydrophilic Fe₃O₄ nanoparticles. These were then modified by a heat treatment in an ethanol/water solution under reflux. The resulting samples were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission/scanning electron microscopy. The immobilization of a TiO₂ nanocatalyst on both unmodified and modified supports was performed to investigate the effects of the modification of the magnetic silica support on the loading of a TiO₂ nanocatalyst and the photocatalytic activity. The loading of TiO₂ and the photocatalytic activity were both improved.     

Fabrication and characterization of Fe_3O_4@SiO_2@TiO_2@Ho nanostructures as a novel and highly efficient photocatalyst for degradation of organic pollution

In this work we synthesize a novel and highly efficient photocatalyst for degradation of methyl orange and rhodamine B. In addition, a new method for synthesis of Fe_3O_4@SiO_2@TiO_2@Ho magnetic core-shell nanoparticles with spherical morphology is proposed. The crystal structures, morphology and chemical properties of the as-synthesized nanoparticles were characterized using Fourier transform infrared spectroscopy(FT-IR), scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy dispersive X-ray(EDS), X-ray diffraction(XRD), UV–vis diffuse reflectance spectroscopy(DRS) and vibrating sample magnetometer(VSM) techniques. The photocatalytic activity of Fe_3O_4@SiO_2@TiO_2@Ho was investigated by degradation of methyl orange(MO) as cationic dye and rhodamine B(Rh B) as anionic dye in aqueous solution under UV/vis irradiation. The results indicate that about 92.1% of Rh B and78.4% of MO were degraded after 120 and 150 min, respectively. These degradation results show that Fe_3O_4@SiO_2@TiO_2@Ho nanoparticles are better photocatalyst than Fe3O4@Si O2@TiO 2@Ho for degradation of MO and Rh B. As well as, the catalyst shows high recovery and stability even after several separation cycles.     

Fe3O4@SiO2@Im‐bisethylFc [HC2O4] as a novel recyclable heterogeneous nanocatalyst for synthesis of bis‐coumarin derivatives

Nanomagnetic bisethylferrocene‐containing ionic liquid supported on silica‐coated iron oxide (Fe₃O₄@SiO₂@Im‐bisethylFc [HC₂O₄]) as a novel catalyst was designed and synthesized. The described catalyst was recycled and used without change in the time and efficiency of the condensation reaction. The Fourier transform‐infrared spectroscopy (FT‐IR), scanning electron microscopy images, X‐ray diffraction patterns, energy‐dispersive X‐ray spectroscopy, transmission electron microscope and vibrating‐sample magnetometer results confirmed the formation of Fe₃O₄@SiO₂@Im‐bisethylFc [HC₂O₄] magnetic nanoparticle. The novel bis‐coumarin derivatives were identified by ¹H‐NMR, ¹³C‐NMR, FT‐IR and CHNS analysis.     

Immobilized palladium on surface-modified Fe3O4/SiO2 nanoparticles: as a magnetically separable and stable recyclable high-performance catalyst for Suzuki and Heck cross-coupling reactions

A palladium-based catalyst (Fe₃O₄/SiO₂/HPG–OPPh₂–PNP) supported on chlorodiphenylphosphine-functionalized magnetic nanoparticles was successfully prepared from Fe₃O₄/SiO₂ with sequential attachment of glycerol and chlorodiphenylphosphine, followed by treatment of an ethanolic solution of palladium chloride with hydrazine. The as-prepared catalyst was characterized by ICP-AES, FTIR, XRD, SEM, and TEM. The Fe₃O₄/SiO₂/HPG–OPPh₂–PNP was found as a magnetically separable and highly active catalyst for Suzuki coupling reactions of aryl iodides, bromides, and chlorides as well as Heck reactions of aryl iodides and bromides. Under appropriate conditions, all reactions afforded the desired products in moderate to excellent yields. Moreover, this catalyst can be easily recovered by using a magnetic field and directly reused for at least six cycles without significant loss of its activity.     

A study on the reduction behavior of silica supported iron and platinum-iron catalysts

The reduction behavior of silica supported iron and platinum-iron catalysts were studied by combinedin situ temperature programmed reduction (TPR)-M?ssbauer Spectroscopy (MBS). The results indicated that the TPR profiles of the supported Fe catalysts were different from that of bulk α-Fe₂O₃. There existed an interaction between the Pt and Fe metals and the SiO₂ support for the Pt−Fe/SiO₂ catalyst. On the supported iron-containing catalysts, the Fe³⁺ species were highly dispersed on the SiO₂ supported before reduction. No Fe⁰ and Fe²⁺ in octahedral vacancy were found in the reduction of SiO₂ supported iron-containing catalysts. Addition of Pt to the Fe/SiO₂ catalyst could promote the reduction of the iron species.