Solid state synthesis and characterization of iron（Ⅱ） pyrophosphate Fe2P2O7

Offwhite pure Fe_2P_2O_7 was synthesized through solid phase reaction using Fe_2O_3 and NH_4H_2PO_4 in argon atmosphere.The reaction products of Fe_2O_3 and NH4_H_2PO_4 at a series of temperatures from 400 to 900℃were characterized by XRD.Comparison and analysis of XRD patterns of resultant products indicated well-crystallized Fe_2P_2O_7 could be obtained over 630℃and Fe_2P_2O_7 prepared at 700℃was triclinic in cell type.Comparison of the cell parameters proved that the as-prepared Fe_2P_2O_7 belonged toβ- Fe_2P_2O_7 in crystal phase and SEM showed its size distribution was 0.5-2μm.     

Fast synthesis of dopamine-coated Fe3O4 nanoparticles through ligand-exchange method

A fast approach was described for the synthesis of water-dispersible monodisperse dopamine-coated Fe₃O₄ nanoparticles（DA-Fe₃O₄） with uniform size and shape via ligand-exchange of oleic acid on Fe₃O₄ using only 2 min.The prepared DA-Fe₃O₄ nanoparticles were characterized by transmission electron microscopy,Fourier transform infrared spectrometry,and vibrating sample magnetometer.The results indicated that the resulting DA-Fe₃O₄ nanoparticles had an average diameter of about 19.2 nm. The magnetic saturation value of the prepared DA-Fe₃O₄ nanoparticles was determined to be 72.87 emu/g,which indicating a well-established superparamagnetic property.     

Particle size effects on the thermal behaviour of maghemite synthesised by flame pyrolysis

Thermal treatment of pure nanoscale maghemite (γ-Fe₂O₃) powders under argon yields different products depending on particle size. Particles with a mean diameter above 15 nm transform to hematite (-Fe₂O₃). Smaller particles, which were synthesised under identical conditions but from solutions with lower Fe³⁺ concentrations, transform into magnetite (Fe₃O₄) during thermal treatment. This phenomenon can be explained by adsorbed or incorporated reducing carboxylate groups. The origin of the reducing species and possible reaction mechanisms with the maghemite particles are discussed.     

Thermal solid–solid interactions and physicochemical properties of NiO/Fe2O3 system doped with K2O

The effects of calcination temperature and doping with K₂O on solid–solid interactions and physicochemical properties of NiO/Fe₂O₃ system were investigated using TG, DTA and XRD techniques. The amounts of potassium, expressed as mol% K₂O were 0.62, 1.23, 2.44 and 4.26. The pure and variously doped mixed solids were thermally treated at 300, 500, 750, 900 and 1000 °C. The catalytic activity was determined for each solid in H₂O₂ decomposition reaction at 30–50 °C. The results obtained showed that the doping process much affected the degree of crystallinity of both NiO and Fe₂O₃ phases detected for all solids calcined at 300 and 500 °C. Fe₂O₃ interacted readily with NiO at temperature starting from 700 °C producing crystalline NiFe₂O₄ phase. The degree of reaction propagation increased with increasing calcination temperature. The completion of this reaction required a prolonged heating at temperature >900 °C. K₂O-doping stimulates the ferrite formation to an extent proportional to its amount added. The stimulation effect of potassium was evidenced by following up the change in the peak height of certain diffraction lines characteristic NiO, Fe₂O₃, NiFe₂O₄ phases located at “d” spacing 2.08, 2.69 and 2.95 Å, respectively. The change of peak height of the diffraction lines at 2.95 Å as a function of firing temperature of pure and doped mixed solids enabled the calculation of the activation energy (ΔE) of the ferrite formation. The computed ΔE values were 120, 80, 49, 36 and 25 kJ mol⁻¹ for pure and variously doped solids, respectively. The decrease in ΔE value of NiFe₂O₄ formation as a function of dopant added was not only attributed to an effective increase in the mobility of reacting cations but also to the formation of potassium ferrite. The calcination temperature and doping with K₂O much affected the catalytic activity of the system under investigation.     

水蒸气和α-Fe_2O_3对铈改性半焦脱除单质汞的影响研究

采用浸渍法制备了铈改性半焦吸附剂(Ce/SC),在小型固定床反应器上考察了水蒸气和α-Fe_2O_3对Ce/SC脱除Hg~0性能的影响,并利用X射线衍射、H2程序升温还原、X射线光电子能谱等分析手段对其机理进行了探究。结果表明,水蒸气会明显抑制Ce/SC对单质汞的脱除效率,原因是H_2O分子在活性组分CeO_2表面发生解离,部分晶格氧转化成Ce-OH官能团,从而导致其氧化活性的降低;α-Fe_2O_3的加入对Ce/SC的脱汞性能无显著影响;当水蒸气和α-Fe_2O_3同时存在时,Ce/SC的脱汞效率虽然有所降低,但是其降低幅度明显低于水蒸气单独作用时的情况,这主要是因为水蒸气与α-Fe_2O_3作用增加了其表面化学吸附氧的含量,提高了α-Fe_2O_3的氧化活性,促进单质汞的氧化和脱除。     

α-Fe_2O_3 immobilized benzimidazolium tribromide as novel magnetically retrievable catalyst for one-pot synthesis of highly functionalized piperidines

Nanostructured α-Fe_2O_3 were prepared by precipitation followed by calcination method.Cetyltrimethylammonium bromide(CTAB) was used as surfactant.The nano α-Fe_2O_3 was then silanized with(3-chloropropyl)-triethoxysilane(CPTES) by room temperature mixing of α-Fe_2O_3 and CPTES to produce silane coated α-Fe_2O_3(ClPr-Si@Fe_2O_3).As-synthesized ClPr-Si@Fe_2O_3 was functionalized via covalent grafting of benzimidazole to produce 3-(l-benzimidazole)Pr-Si@Fe_2O_3.This was further reacted with bromine to afford α-Fe_2O_3 immobilized benzimidazolium tribromide(α-Fe_2O_3-BIM tribromide).This ionic liquid(IL)α-Fe_2O_3 BIM tribromide was characterized by FT-IR,XRD,TEM,SEM,TGA,VSM,EDX and BET analysis.The as-synthesized IL tribromide was used as catalyst for one-pot synthesis of highly substituted piperidines.The method is greener in terms of solvent selection,recovery of the catalyst and efficiency.     

Laser-induced breakdown spectroscopy of γ-Fe2O3 nanoparticles in a biocompatible alginate matrix

An intensive multi-disciplinary research effort is underway at Wayne State University to synthesize and characterize magnetic nanoparticles in a biocompatible matrix for biomedical applications. The particular system being studied consists of 3–10 nm γ-Fe₂O₃ nanoparticles in an alginate matrix, which is being studied for applications in targeted drug delivery, as a magnetic-resonance imaging (MRI) contrast agent, and for hyperthermic treatments of malignant tumors. In the present work we report on our efforts to determine if laser-induced breakdown spectroscopy (LIBS) can offer a more accurate and substantially faster determination of iron content in such nanoparticle-containing materials than competing technologies such as inductively-coupled plasma (ICP). Standardized samples of -Fe₂O₃ nanoparticles (5–25 nm diameter) and silver micropowder (2–3.5 μm diameter) were created with thirteen precisely known concentrations and pressed hydraulically to create solid “pellets” for LIBS analysis. The ratio of the intensity of an Fe(I) emission line at 371.994 nm to that of an Ag(I) line at 328.069 nm was used to create a calibration curve exhibiting an exponential dependence on Fe mass fraction. Using this curve, an “unknown” γ-Fe₂O₃/alginate/silver pellet was tested, leading to a measurement of the mass fraction of Fe in the nanoparticle/alginate matrix of 51 ± 3 wt.%, which is in very good agreement with expectations and previous determinations of its iron concentration.     

Fe2O3/Al2O3氧载体用于甲烷化学链燃烧：负载量与制备方法的影响

以不同方法制备了系列Fe₂O₃/Al₂O₃氧载体,采用XRD、H₂-TPR、CH₄-TPR、O₂-TPD和BET等分析技术对氧载体进行了表征。研究了不同Fe₂O₃负载量氧载体的甲烷化学链燃烧性能,考察了不同制备方法对Fe₂O₃/Al₂O₃氧载体结构、反应性和产物选择性的影响。结果表明,Fe₂O₃负载量对氧载体活性及产物中CO₂选择性的影响较大,负载量较低时氧载体活性较低且引起甲烷部分氧化产物CO含量增加。制备方法亦对氧载体与甲烷的反应活性有所影响,整体上共沉淀法制备的质量分数60％Fe₂O₃/Al₂O₃氧载体具有较高的氧化活性和化学链循环稳定性。其在反应温度850℃、反应时间15 min、30次循环后甲烷转化率及产物中CO₂选择性均未见明显降低。     

Solid–solid interactions between ferric and cobalt oxides as influenced by Al2O3-doping

The solid–solid interactions between pure and alumina-doped cobalt and ferric oxides have been investigated using DTA, IR and XRD techniques. Equimolar proportions of basic cobalt carbonate and ferric oxide and different amounts of aluminum nitrate were added as dopant substrate. The amounts of dopant were 0.75, 1.5, 3.0 and 4.5 mol% Al₂O₃.

The results obtained revealed that solid–solid interaction between Fe₂O₃ and Co₃O₄ takes place at temperatures starting from 700°C to produce cobalt ferrite. The degree of propagation of this reaction increases progressively as a function of precalcination temperature and Al₂O₃-doping of the reacting solids. However, the heating of pure mixed solids at 1000°C for 6 h. was not sufficient to effect the complete conversion of the reacting solids into CoFe₂O₄, while the addition of a small amount of Al₂O₃ (1.5 mol%) to ferric/cobalt mixed solids followed by precalcination at 1000°C for 6 h conducted the complete conversion of the reacting solids into cobalt ferrite. The heat treatment of pure and the 0.75 mol%-doped solids at 900 and 1000°C effected the disappearance of most of IR transmission bands of the free oxides with subsequent appearance of new bands characteristic for the CoFe₂O₄ structure. An increase in the amount of Al₂O₃ added from 1.5–4.5 mol% to the mixed solids precalcined at 1000°C led to the disappearance of all bands of free oxides and appearance of all bands of cobalt ferrite. The promotion effect of Al₂O₃ in cobalt ferrite formation was attributed to an effective increase in the mobility of the various reacting cations. The activation energy of formation (ΔE) of CoFe₂O₄ phase was determined for pure and doped solids. The computed values of ΔE were, respectively, 99.6, 87.8, 71.9, 64.7 and 48.7 kJ mol⁻¹ for the pure solid and those treated with 0.75, 1.5, 3 and 4.5 mol% Al₂O₃.     

Kinetics of thermite reaction in Al-Fe2O3 system

After non-isothermal differential scanning calorimetry (DSC) and X-ray diffraction experiments are carried out, the reaction kinetics of Al-Fe₂O₃ system is analyzed by a model-free Starink method. In our study, activation energy was determined as 145 kJ/mol for 8Al-3Fe₂O₃ thermite reaction, the value is comparable to the activation energy for diffusion of Al in FeAl₂O₄ and is less than the activation energy for diffusion of Al in Fe₃Al, suggesting that the diffusion of Al into FeAl₂O₄ controls the product of the thermite reaction.     

磷酸修饰对纳米Fe2O3热稳定性及光催化性能的影响

通过溶液浸渍蒸干过程实现了磷酸对Fe₂O₃纳米粒子的表面修饰, 研究了磷酸修饰对纳米Fe₂O₃的热稳定性及光催化活性的影响. 结果表明, 磷酸修饰显著提高了Fe₂O₃的热稳定性, 主要归因于磷酸修饰在样品表面抑制了粒子之间的团聚生长. 同时, 在光催化降解气相乙醛和液相苯酚的测试中, 磷酸修饰后热处理温度为600 ℃的样品表现出了最佳的可见光催化性能, 这主要归因于该样品具有高晶化度、 小粒子尺寸及大比表面积, 并且适量的修饰有利于其光催化性能的提高.     

SO_4~(2-)功能化处理对Fe_2O_3催化剂上氨选择性催化还原NO_x性能的促进机理研究

采用沉淀法制备了Fe(OH)_3和Fe_2O_3。通过硫酸化处理得到SO_4~(2-)/Fe(OH)_3和SO_4~(2-)/Fe_2O_3两种催化剂,并将其应用于氨选择性催化还原NO_x(NH_3-SCR)反应,研究了SO_4~(2-)功能化处理对Fe_2O_3催化剂上NH_3-SCR脱硝性能的促进机理。结果表明,与纯的Fe_2O_3相比,硫酸化处理得到的催化剂上SCR活性得到显著提升;其中,SO_4~(2-)/Fe(OH)_3表现出更加优异的催化性能,在250-450℃时NO_x转化率高于80%,且具有优异的稳定性和抗H_2O+SO_2性能。XRD、Raman、TG、FT-IR、H_2-TPR、NH_3-TPD和in situ DRIFTS等表征结果显示,硫酸功能化处理能抑制Fe_2O_3的晶粒生长,同时SO_4~(2-)与Fe~(3+)结合形成硫酸盐复合物,提高了催化剂表面酸性位点的数量和酸强度,抑制了Fe_2O_3上的氨氧化反应,从而提高了其脱硝催化性能。     

Pt/Au/Fe3O4的制备及其电化学性能

以制得的纳米Fe₃O₄颗粒作为载体,用还原法将还原出的Au与Pt分别负载到Fe₃O₄颗粒表面,制得纳米Pt/Au/Fe₃O₄复合材料。对Pt/Au/Fe₃O₄进行紫外可见光吸收光谱、透射电子显微镜、X射线衍射及光电子能谱等物理表征,结果表明,Au与Pt均匀地沉积到了Fe₃O₄纳米颗粒表面。对纳米Pt/Au/Fe₃O₄复合材料进行循环伏安扫描,当H₂PtCl₆的加入量达到8 mL时,Pt/Au/Fe₃O₄催化性能最佳;正扫电流峰i_p与扫描速率的平方根v^1/2线性相关,Pt/Au/Fe₃O₄催化氧化甲醇的过程受扩散控制;对催化剂进行201次循环伏安扫描,催化剂仍然能保持较好的催化性能且稳定性良好。因此,所合成催化剂Pt/Au/Fe₃O₄是一种具有良好化学稳定性的阳极催化剂材料。     

化学链制氢中Fe2O3/LaFeO3载氧体的性能研究

采用柠檬酸络合法制备Fe₂O₃/LaFeO₃复合氧化物,将该氧化物作为化学链制氢过程的载氧体,在反应温度为900 ℃、常压下,对Fe₂O₃/CH₄（剂烷比）、进水量、金属负载量进行了考察。结果表明,剂烷比为2：1、进水量为0.1 mL、质量分数15%Fe时载氧体性能最好,甲烷转化率达到60%,单次循环氢气产量为45 mL。将该评价结果与XRD和H₂-TPR表征结果进行关联发现,反应过程的活性位不是金属氧化物,而是吸附氧,而且吸附氧越容易还原,甲烷转化率和氢气产量越高。通过连续60次还原-氧化循环发现,该载氧体上甲烷转化率和氢气产量比较稳定,循环后仍然保持钙钛矿结构。     

Fe3O4@PI催化剂的制备及其费托合成性能

分别采用水热、水热-包覆、球磨法制备了Fe_3O_4、聚酰亚胺(PI)改性的Fe_3O_4@PI和Fe_3O_4-PI催化剂用于费托合成反应,对比研究了PI改性及其含量变化对Fe基催化剂催化CO加氢产物分布的影响规律。结合XRD、SEM、TEM、H_2-TPR、COTPD、FT-IR、XPS、TG和接触角实验等手段对催化剂样品进行了表征。结果表明,Fe_3O_4、Fe_3O_4@PI和Fe_3O_4-PI样品均为球形颗粒; PI改性促进了Fe_3O_4的还原,亲水性增强。Fe_3O_4@PI样品中,PI均匀包覆于Fe_3O_4表面,具有较好的热稳定性;与Fe_3O_4、Fe_3O_4-PI相比,Fe_3O_4@PI样品CO吸附增强。在CO加氢反应中,与Fe_3O_4相比,PI改性的Fe_3O_4@PI和Fe_3O_4-PI样品催化活性下降,二次加氢能力受到抑制,烯烃选择性提高; Fe_3O_4@PI样品烯烃选择性增加明显,烯烷比(O/P)由改性前的0.50提高至2.15;适宜含量的PI改性促进C5+烃生成。     

Fe3O4矿石球团焙烧化学的穆斯堡尔效应研究

应用穆斯堡尔效应实验对焙烧过程中球团的矿相变化及铁离子的赋存情况进行了研究,进一步了解了焙烧化学。     

Mo/Fe3O4(111)表面对燃煤烟气汞吸附的密度泛函研究

利用CASTEP软件包采用密度泛函理论计算研究了过渡金属Mo掺杂Fe_3O_4(111)Fe_(tet)表面对Hg~0、HgCl和HgCl_2的吸附特征,分析了Mo掺杂前后Fe_3O_4(111)Fe_(tet)表面上不同汞物种的吸附形态。结果表明,Mo掺杂Fe_3O_4(111)Fe_(tet)表面对HgCl和HgCl_2为化学吸附,而对Hg~0的吸附为物理吸附;与纯净表面相比,HgCl在Mo原子掺杂表面上的吸附能提高了40%-66%。HgCl_2在纯净Fe_3O_4(111)Fe_(tet)表面形成"M"形结构;而掺杂Mo原子后,由于Cl原子与Mo原子之间更强的相互作用,使得HgCl_2发生了完全解离,两个Cl原子分别与Mo原子和Fe原子成键吸附在表面,Hg脱附。相关研究结果可为脱除燃煤烟气中的汞提供一定的理论指导。     

Relationship between temperature-programmed reduction profile and activity of modified ferrite-based catalysts for WGS reaction

A series of modified ferrites were prepared by doping iron oxide with various transition/non-transition/inner-transition metal ions [M = Cr, Mn, Co, Ni, Cu, Zn and Ce] in situ during synthesis. All the modified ferrites thus obtained exhibit remarkably high surface areas, greater than that of pure iron oxide (Fe₂O₃) sample. The efficacy of the dopant ions in modifying the resultant specific surface area, could be directly related to variations in the rate of crystal growth. The nature and concentration of the foreign cations present in the system govern this variation. Interestingly all the modified ferrites, exhibit a narrow pore size distribution in the range of 4.9–25 nm. XRD analysis revealed the existence of hematite (Fe₂O₃) phase in all the as-prepared samples. The X-ray diffraction experiments performed on activated catalysts, confirmed the existence of magnetite (Fe₃O₄) phase with a nominal composition of Fe_2.73M_0.27O₄. These inverse or mixed spinels with general formula A_(1−δ)B_δ[A_δB_(2−δ)]O₄, possess highly facile Fe³⁺  Fe²⁺ redox couple, the degree of facileness depends on the extent of synergistic interaction between iron and the other substitutent metal ion. The rapid electron hopping between Fe³⁺  Fe²⁺ in the Fe₃O₄ lattice system is essential to catalyze WGS reaction. From TPR it was observed that, incorporation of metal cations into the hematite (-Fe₂O₃) crystal structure alters the reducibility of the hematite particles, which in turn depends on the nature of the incorporated metal cation. A plausible explanation for the WGS activity over various modified ferrites has been attempted with the help of TPR analysis.     

Aerosol-assisted submicronγ-Fe2O3/C spheres as a promising heterogeneous Fenton-like catalyst for soil and groundwater remediation:Transport,adsorption and catalytic ability

This research reports a novel heterogeneous Fenton-like catalyst which could freely move through the model sediments and easily seize the pollutants in addition to efficiently catalyze H2O2,well suitable for soil and groundwater remediation.Herein,submicron y-Fe2O3/C spheres were synthesized through a facile one-step aerosol-based process.In a series of column tests,these spheres exhibit better transport ability due to their optimal size,conforming to the prediction by the Tufenkji-Elimelech filtration theo ry.Meanwhile,y-Fe2O3/C spheres could act as a strong adsorbent for organic pollutants owing to the presence of carbon,thereby providing a driving force to gather contaminants into their vicinity and facilitating the reaction.In addition,immobilization of y-Fe2O3 nanoparticles into carbon spheres protects iron oxides from aggregation,and thus retains the number of active sites for catalytic decomposition of H2O2.Hence,the system containing the as-prepared y-Fe2O3/C spheres and H2O2 shows the high removal efficiency and degradation efficiency in the remediation of recalcitrant organic contaminants such as methylene blue and sulfamethoxazole.     

煤灰/K_2CO_3/Fe_2O_3对脱矿无烟煤燃点与燃烧速率的影响(英文)

考察了煤灰/K2CO3/Fe2O3及其之间的相互作用对酸洗无烟煤燃点和燃烧速率的影响。不同温度下制备的煤灰显示了不一样的性质(如化学组成、颜色和形貌)。脱矿无烟煤(负载和非负载催化剂)的燃烧反应性测试在热重分析仪(TGDTG)中完成,结果表明,煤灰本身对酸洗无烟煤的燃点几乎没有影响,而高温下制备的煤灰能够明显提高酸洗无烟煤的燃烧速率。当煤灰和K2CO3或者Fe2O3的混合物加入酸洗无烟煤中作为燃烧催化剂时,可以看出与单独使用K2CO3或Fe2O3相比,煤灰的加入明显导致酸洗煤的燃烧速率下降,而对其燃点影响不大。同样,K2CO3和Fe2O3之间的相互作用也能够对酸洗无烟煤的燃烧速率产生负面影响。