Pyrolysis of soybean oil with H-ZSM5 (Proton-exchange of Zeolite Socony Mobil #5) and MCM41 (Mobil Composition of Matter No. 41) catalysts in a fixed-bed reactor

Soybean oil was pyrolyzed with various catalysts in a fixed-bed reactor under nitrogen flow at 420 and 450 °C. The H-ZSM5 catalysts (molar ratio SiO₂/Al₂O₃ = 28, 40, and 180) and 2 wt% (Ga, Al or Cu) impregnated MCM41 catalysts were used in order to investigate the effect of catalysts during the pyrolysis process. The gas products in all experiments were mainly methane, ethane and propylene. The liquid products in the presence of H-ZSM5 catalysts were mainly aromatic components while those with metal/MCM41 catalysts were a mixture of alkanes, alkenes, alkadienes, aromatic and carboxylic acids. The highest coke yield of 4.4 wt% was obtained with Ga/MCM41 catalyst at the pyrolysis temperature of 420 °C. The effect of catalysts on product yield and composition was systematically investigated.     

芦苇对重金属Pb和Mn吸收和富集的研究

叙述了芦苇对重金属离子Pb2+,Mn2+的生物吸附特征以及其对水体中重金属离子的去除率受不同重金属初始浓度的影响和芦苇根、茎、叶对重金属离子的富集情况,指出,芦苇对Mn2+的吸附在35 min内达到平衡,对Pb2+的吸附在50 min内达到平衡,吸附动力学结果符合伪二级动力学方程,决定系数分别为0.984 6和0.971 3;Freundlich等温线可较好地拟合芦苇吸附Mn2+及Pb2+的过程,Mn2+及Pb2+的吸附量分别达到8.281 8 mg/g和6.025 3 mg/g。芦苇各器官对Mn2+富集强于对Pb2+的富集能力。不同器官对同种重金属离子的富集量差异显著,茎叶是富集Mn2+的主要器官,根是富集Pb2+的主要器官。     

Effect of functionalized MCM41 nanoparticles on syngas fermentation

MCM41 nanoparticles with or without mercaptopropyl functional groups were added to a synthesis gas fermentation reactor to investigate their influence on syngas fermentation. Carbon monoxide was fermented using Rhodospirillum rubrum (R. rubrum), resulting in an enhanced H₂ concentration in the product gas as a result of a biologically mediated water–gas shift (WGS) reaction. The results indicated that the H₂ yield was enhanced by ～200% when 0.6 wt% of the MCM41 nanoparticles functionalized with 5% molar ratio of mercaptopropyl group were added to the reactor. These results complement previous studies and suggest that the increased H₂ yield is due to enhanced CO–water mass transfer through the addition of the functionalized MCM41 nanoparticles.     

重金属处理技术研究进展

重金属是水环境中的主要污染物之一,随着社会的进步和工业的发展,含重金属离子废水的排放量在逐渐增多,主要来自电镀、采矿、冶金、化工等工业,具有潜在的危害性.近些年来,处理重金属废水的技术发展迅速,吸附法因为速度快、操作简单、吸附材料来源广等优点被人们广泛应用,尤其是金属离子印迹技术.目前为止,已经成功制备出了以Ni2＋、Cu2＋、Cd2＋、Zn2＋等多种金属离子为模板离子的金属离子印迹聚合物,并在环境分析和医药领域有着广泛的应用.     

In-situ activation of hydrogen evolution in pH-neutral electrolytes by additions of multivalent cations

Activation of the hydrogen evolution reaction (HER) in close to pH-neutral electrolytes can be achieved by addition of trivalent cations. This activation has been investigated using steady state polarization, electrochemical impedance spectroscopy (EIS) and chemical analysis of cathode films for yttrium. Several multivalent cations were included in this study, such as Al(III), Mg(II), Y(III), Sm(III), La(III) and Sc(III). In general the more acidic the metal ions the larger is the activation. Metal hydroxide films formed in the alkaline diffusion layer at the cathode surface can have a negative impact on the magnitude of this activation, and therefore complicate the interpretation of the results. The activation corresponds to a transport of metal ion complexes to the electrode surface and the reduction of bound ligand water to form hydrogen.     

Mechanism of fast hydrogen generation from pure water using Al–SnCl2 and bi-doped Al–SnCl2 composites

The mechanism of fast hydrogen generation from pure water using selectively activated Al–SnCl₂ composites was elucidated with the help of experimental data using combined XRD, SEM, EDX, DSC and calorimetric techniques. It is found that H₂ is produced from two different but simultaneous routes specific to the Al–SnCl₂ composite stoichiometry achieved after ball milling the precursor that readily yields, besides the excess of Al, Sn and AlCl₃. Hydrogen is simultaneously produced from the reaction of the so-formed Al–Sn alloy with water, and from the reaction of the in situ generated AlCl₃ with water, yielding HCl (protons) that further again react with Al, both reactions significantly increasing the hydrogen production rate. The effect of Bi on the hydrogen conversion yield on the Al–SnCl₂ composite was also investigated. The electrochemical activity of Al is further enhanced by doping Bi into Al–SnCl₂ composite. Meanwhile, DFT (density functional theory) calculations show that Bi micro domains present onto the Al (111) crystallite faces of the composite significantly reduce the adsorption energy of the OH groups while, Mg- or Cr-doped Al–SnCl₂ composites increase this adsorption energy. The Mulliken charge analysis indicates that Bi leads to less electron transport between Al and O atoms (weaker interaction) than pristine Al (111) surface. Bi therefore contributes to inhibit the formation of the hydroxyls on the Al metal surface, thereby allowing the clean metal to continuously react with water.     

Proton conductivity of ordered mesoporous materials containing aluminium

In order to check the influence of Brønsted acidic Al sites in the walls of mesoporous materials on their proton conductivity, we introduced aluminium into the mesoporous SiO₂ framework Si-MCM-41, which possesses hexagonally ordered channels, by using different Al sources, i.e. sodium aluminate, aluminium sulphate and aluminium isopropoxide. The successful synthesis of ordered mesoporous material with incorporated Al species was proven by X-ray diffraction, energy-dispersive X-ray spectroscopy, nitrogen adsorption, scanning electron microscopy and solid state ²⁷Al MAS NMR. By realizing Si/Al ratios of 8-40 it was found that the proton conductivity of the mesoporous aluminium silicates measured by impedance spectroscopy significantly increases with the Al content, reaching a conductivity of 3 × 10⁻³ S cm⁻¹ at 140 °C. The increase of the proton conductivities compared to Al-free Si-MCM-41 results from (i) an improved hydrophilicity enhancing the water storage capability, (ii) a decreased particle size from the micrometer to the nanometer scale (50-100 nm) and (iii) the existing Brønsted acidity in the mesoporous Al-MCM-41. The Al source NaAlO₂ gives clearly the best results because the entire Al incorporated within the framework is tetragonally coordinated, while for samples prepared with Al₂(SO₄)₃ or AIP also octahedral coordination of oxygen around the Al centers is observed by ²⁷Al MAS NMR.     

Effect of NaOH addition on the thermochemical heat storage capacity of nanoporous molecular sieves

The water vapor sorption capacity and corresponding generated heat amount are the most important properties for adsorbents in thermochemical heat storage systems. In order to understand the adsorption/desorption behavior of three nanoporous molecular sieves such as 5A, mordenite and natural clinoptilolite (with different structures, Si/Al ratios and balancing cations), the pure zeolites and their composites (obtained by depositing NaOH onto the molecular sieves) were characterized in their structural and surface properties by using appropriate techniques (N₂ adsorption isotherms at ?196 °C, XRD and (MAS) NMR). The adsorption of water was performed using a Setaram TG‐DSC 111 apparatus. Three successive cycles of hydration (at 20 °C)/dehydration (at 150 °C) were carried out to check the stability of the system in conditions close to those used in adsorption heat pumps. The measured heats of dehydration vary in the 183–614 kJ kg^?1_sample range for the various samples that present also different water vapor sorption capacities (from ≈ 0.08 to ≈ 0.14 kg_H2O kg^?1_sample). The water adsorption/desorption behavior of the zeolites was mainly related to the porous structure and to the Si/Al ratio, that drive the affinity of zeolite to water. The experimental results showed that the impregnation of the three kinds of nanoporous zeolites with different amounts of sodium hydroxide negatively affects the sorption characteristics of the composites. The blockage of zeolite pores (that limits the access to water molecules), the slight amorphization of the zeolite structure and the formation of carbonates are some of the phenomena identified to influence the water sorption onto NaOH‐containing composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrochemical evolution of hydrogen on composite La–Ni–Al/Ni–S alloy film in water electrolysis

The composite La–Ni–Al/Ni–S alloy film was obtained by molten salt electrolysis and aquatic electrodeposition in turn. The La–Ni–Al alloy film was prepared in Na₃AlF₆–La₂O₃–Al₂O₃ molten salt electrolyte by galvanostatic electrolysis at 100 mA cm^?2. The results showed that La³⁺ and Al³⁺ ions could be co-reduced on the nickel cathode and form La–Ni–Al film at c.a. ?0.5 V, which is much lower than that of the theoretical decomposition potential of lanthanum and aluminum. With high HER activity, the composite La–Ni–Al/Ni–S film (η₁₅₀ = 70 mV, 353 K) could absorb large amount of H atoms. Instead of the dissolution of the Ni–S film, the absorbed H atoms would be oxidized under intermittent electrolysis effectively and prolong the lifetime of the cathode.     

La-doped supported Ni catalysts for steam reforming of methane

Ni-La/α-Al₂O₃ catalysts at different Ni/La ratio of respectively 7/3, 8/2 and 9/1 to obtain a material with total loading of 10 wt% as used in industrial methane steam reforming field are prepared with incipient wetness impregnation method. Various techniques including TGA-DTA, XRF, XRD, particles size, H₂-RTP and BET are used to characterize materials and their catalytic performance is evaluated during the steam reforming reaction at different temperatures ranging from 500 to 800 °C. Only NiO and α-Al₂O₃ phases are evidenced by DRX indicating probably the presence of small lanthanum crystallites in high dispersion state. Addition of La may cause strong change at the surface of NiO sites. Substitute Ni by La leads to smaller and well dispersed NiO particles sizes with strong metal support interaction (SMSI). TPR analysis reveals the reduction of Ni species with high Ni-La-Al interactions particularly well observed with 3 wt%La catalyst. The small Ni particles sizes highly dispersed on the support enhance the dissociative adsorption of CH_x species. The highest H₂ yield is obtained with 7Ni-3La/Al catalyst reaching 94% at 800 °C.     

Perovskite La–St–Fe–O (St=Ca,Sr) supported nickel catalysts for steam reforming of ethanol: The effect of the A site substitution

The perovskite type oxides (PTO) supported Ni catalysts were prepared by one step citrate complexing method and were applied to steam reforming of ethanol (SRE). The catalysts were characterized by X-ray diffraction (XRD), oxygen temperature-programmed desorption (O₂-TPD), temperature programmed reduction (TPR), thermal analysis (TG), mass spectrometer (MS), physical adsorption for specific surface areas and hydrogen chemical adsorption for metal surface areas. The perovskite oxide without substitution is LaFe_1−yNi_yO₃. For the samples substituted by Sr or Ca, as indicated by the XRD results, the calcium and strontium were successfully introduced into the La site of the LaFe_1−yNi_yO₃. The Ca substitution in LaFe_yNi_1−yO₃ perovskite leads to the enrichment of oxygen vacancies, and some of released oxygen species is resulted from the reduction of the Fe⁴⁺ into Fe³⁺ in the perovskite. Although the enrichment of oxygen vacancies was also observed for the samples with Sr substitution, the insertion of Sr into the perovskite lowers the dispersion of metallic Ni, leading to a poor SRE activity. The correlation between the oxygen vacancies and the stability for SRE indicates that the surface oxygen vacancies and the promoted bulk oxygen species, as the results of the La site substitution, restrain the carbon formation and facilitate the carbon elimination. The surface oxygen vacancies as well as lattice oxygen vacancies are beneficial for the reaction between water and hydrocarbon species on the catalyst surface, reducing carbon containing intermediates and accelerating eliminating reaction of the deposited carbon. In sum, the A site doped perovskite La_1−xCa_xFe_1−yNi_yO₃ supported nickel catalysts exhibit very good stability for SRE, due to the surface and bulk oxygen vacancies.     

Preparation and adsorption denitrogenation from model fuel or diesel oil of heteroatoms mesoporous molecular sieve Co-MCM-41

The MCM-41 and Co-MCM-41 molecular sieves were confirmed by characterization with XRD, FTIR, nitrogen adsorption, and NH₃-TPD. Denitrogenation of model fuel containing about 1,737.35 μg (nitrogen)/g or diesel oil was studied over the samples. The molecular size of quinoline, calculated by using density functional theory, was 7.116 × 5.002 Å, implying that it easy access to mesoscale pores of molecular sieves. The adsorption denitrogenation capacity of Co-MCM-41 was clearly more effective than MCM-41 due to its strong acidity and chemisorption. The basic nitrogen removal of diesel oil on MCM-41 or Co-MCM-41 was 68.22 and 65.91%, respectively.     

Cation vacancies in perovskites doped with La and Gd

Abstract

Whereas doping CaTiO₃ or SrTiO₃ with ～0·05 formula units (f.u.) of trivalent rare earth ions substituted for Ca can yield majority positron annihilation lifetime τ₁ increases of up to 30% due to the presence of cation vacancies, similar doping of BaTiO₃ produces increases of only ～10%. The difference is attributed to hole trapping around cation vacancies in BaTiO₃. The absence of significant changes to τ₁ for La doped CaTiO₃ when oxidised samples are reduced by sintering in a hydrogenous atmosphere is attributed to the formation of oxygen vacancies that co-exist with the original cation vacancies. Solid state nuclear magnetic resonance showed that a significant fraction of the La ions in BaTiO₃ containing 0·04 f.u. of La were in cubic coordination, irrespective of the charge compensation scheme employed. Doping of sintered SrTiO₃ with La to produce up to 0·2 f.u. of Sr cation vacancies had no significant effect on Sr leaching in deionised water at 90°C.     

Kinetics study on the generation of hydrogen from an aluminum/water system using synthesized aluminum hydroxides

Kinetics study on the generation of hydrogen from an Al/water system is performed. The reaction is affected by three major factors such as the concentration of hydroxyl ions (pH values), catalysts, and temperature. However, these factors are interacted and sometimes difficult to separate. This study demonstrates how these factors affect the generation of hydrogen in an Al/water system. Aluminum hydroxide, Al(OH)₃ (bayerite phase), synthesized using a chemical solution method, is proved to be a very effective catalyst for the reaction of Al and water. Approximately 95% yield (1300 mL) of hydrogen is produced from 1 g Al in 10 mL water using 3 g Al(OH)₃ catalyst at room temperature within 1 minute. The generation rate of hydrogen is accelerated due to the catalyst Al(OH)₃ and the exothermic heat. In this report, a ball‐mixing process, the ratio of Al:Al(OH)₃:H₂O, and the reacting temperatures are investigated to clarify the effect of catalyst Al(OH)₃. The synthesized Al(OH)₃ catalyst is found to reduce the activation energy of Al/water reaction from 158 kJ/mol to 73.3~76.9 kJ/mol. The roles of hydroxyl ions (ie, pH values), temperature, and catalyst on this phenomenal reaction are explained using a kinetics study and the concept of Fick first law. The 3 factors all improve the flux of hydroxyl ions through the passive Al₂O₃ layer; therefore, the generation of hydrogen is enhanced.     

巯基功能化介孔硅的孔径调节及其吸附性能研究

叙述了以F127和CTMABr为模板剂,添加扩孔剂1,3,5三甲苯（TMB）经水热法合成不同孔径的巯基（-SH）修饰的新型介孔吸附剂。指出,以Cu＋2和Pb＋2为处理对象,根据不同孔径的介孔吸附剂对重金属离子的吸附性能,确定扩孔剂TMB投加量为TMB和表面活性剂摩尔比为1.5时,可得到重金属吸附的适用吸附剂的扩孔功能化硅基介孔材料,其BET孔径为6.554 nm,BET孔容为0.6134 cm3/g。     

Influence of zeolitic structure on photoreduction property and hydrogen evolution reaction

A new photocatalytic material developed by supporting TiO₂ in combination with transition metal ion like cobalt and heteropolyacid (HPA) on the surface is facilitating enhanced photoreduction of water and methyl orange. Zeolites being a solid acid play an important role in the electron transfer reaction, facilitated by the Lewis acid sites in the form of aluminium ions. In the present work, four different zeolite matrices namely, NaY zeolite, ultrastable zeolite Y, beta zeolite and titanium silicate-1 have been used for the synthesis of new photocatalytic materials. These materials have been evaluated for water splitting by an initial screening procedure using methyl orange photoreduction. The photocatalyst containing Na Y has emerged as a potential photocatalyst with hydrogen evolution rate of 2730 μmol/h/g of TiO₂. Hydrogen evolution was not observed for the composite photocatalysts synthesized using the other zeolite matrices. It has been observed that physico-chemical properties like Si/Al ratio, acidity and basicity of the zeolite support have a tremendous influence on the photoreduction property of these zeolite matrices.     

In-situ La doped Co3O4 as highly efficient photocatalyst for solar hydrogen generation

Photocatalytic hydrogen production via water splitting using metal oxide semiconductors has attract great interests because of the two electrons on the kinetics. Pristine Co₃O₄ was widely studied as efficient photocatalyst, but prefers to produce oxygen due to its lower band-edge positions with regard to water redox potentials. In this work, high efficient photocatalyst basing on non-noble La doped Co₃O₄ on graphene, i.e., La_xCo_3-xO₄/G, were first reported and prepared by the microwave hydrothermal synthesis. In this newly developed hybrids, La and Co ions were adsorbed on the surface of graphene (G) and subsequently reacted with ammonia to yield the La_xCo_3-xO₄/G nanohybrid by in-situ chemical deposition methods. The activity for hydrogen generation of the nanohybrid exhibits 2 times higher than undoped Co₃O₄/G under visible light irradiation. The H₂ evolution of nanohybrid reaches 6.543 mmol g^?1 h^?1 when the molar ratio of La/Co is 10% in the nanohybrid. Our experimental results indicate the incorporation of La doped in the Co₃O₄ crystal lattice not only forms the lattice defects, resulting in provision for capture trap and the separation of electrons and holes, but also changes the band structure to eventually improve the photocatalytic activity under visible light. Therefore, non-noble La is a promising substitute to prepare highly efficient hydrogen photocatalyst and can be extendedly applied to the other metal oxide semiconductors for solar hydrogen production.     

Precious metal oxides for electrochemical energy converters: Pseudocapacitance and pH dependence of redox processes

The mechanism of charge storage in hydrous platinum metal oxides is considered in more detail with respect to the pH dependence of redox capacitance for applications in double-layer capacitors, fuel cells, and pH sensors. An amorphous RuO₂ electrode is able to work like a pH glass electrode during the titration of hydrochloric acid with sodium hydroxide solution. It is shown that the proton exchange mechanism at a glass membrane can be reproduced by platinum metal oxide-hydrates bound in a polymer matrix. Hydrous RuO₂, obtained by alkaline precipitation or thermal decomposition from RuCl₃, as well as single crystal RuO₂, were characterized by TOF-SIMS, NMR spectroscopy, and electrochemical techniques. The proton conductivity of hydrous RuO₂ appears to be due to the dissociative adsorption of water and the formation of acidic OH groups in Ru(III,IV) cluster ions. Depending on the pH of the solution, the electrode potential is determined by the formal hydrogen oxidation or oxygen reduction in ruthenium cluster ions. During aging, the active Ru(III) surface sites are partially oxidized to Ru(IV).     

H2 adsorption on Cu(I)-ZSM-5: Exploration of Cu(I)-exchange in solution

A new Cu(I)-exchange method for zeolites in liquid media (acetonitrile) was developed with Cu/Al ratios surpassing 0.5 with ZSM-5 crystals containing pure Cu(I) cations without impurities such as Cl ions. The method resulted in a higher Cu/Al ratio (0.78) for mesoporous [B]-ZSM-5 when compared to microporous [Al]-ZSM-5 and [B]-ZSM-5 (0.55 and 0.66 respectively). H₂ storage capacities of these Cu(I)-exchanged zeolites were investigated at 323 K along with their differential heat of H₂ adsorption using adsorption calorimetry. H₂ storage capacities as high as 0.03 wt. % at 323 K and 40 kPa were achieved on [Al] and [B]-ZSM-5 and mesoporous [B]-ZSM-5 showed an outstanding H₂/Cu ratio of 1.03 at 323 K and below 100 kPa. Coverage-dependent differential adsorption heats were found to be ranging from 95 kJ/mol to 5 kJ/mol with observed values of 30–10 kJ/mol for H₂/Cu ratios between 0.05 and 0.15.     

Generation of hydrogen from aluminum and water - Effect of metal oxide nanocrystals and water quality

Metal Oxides nanocrystals such as TiO₂, Co₃O₄, Cr₂O₃, Fe₂O_3, Mn₂O₃, NiO, CuO and ZnO were used as modifiers on the metallic aluminum (Al) powders for the production of hydrogen in deionized water or tap water at room temperature. In particular, the influences of TiO₂ nanocrystals with various crystal sizes on the production of hydrogen from the reaction in tap water under ambient condition were investigated in details. It was found that hydrogen was barely generated from metal Al powders in tap water at 25-45 °C but significantly produced in deionized water above 35 °C without any modifiers. TiO₂, Co₃O₄, and Cr₂O₃ nanocrystals were very effective to promote hydrogen generation from the reaction of Al and deionized water at 25 °C. In addition, while other oxide nanocrystals were ineffective to promote hydrogen generation in tap water, TiO₂ nanocrystals (P90, ∼14 nm in diameter) were found to be highly effective in facilitating the production of hydrogen from the reaction of Al with tap water, comparable to the well-known γ-Al₂O₃. The production of hydrogen over time was found to be dependent on the passive layer of metal Al, where Al(OH)₃ plays an important role during reaction. Pitting is proposed as the major mechanism behind the production of hydrogen in the nanocrystals TiO₂ (P90)-modified Al/tap water system, which is thought to be originated from point defects, and differ considerably from the uniform corrosion model.