Heterogeneous oxidation of carbonyl sulfide on mineral oxides

Heterogeneous oxidation of carbonyl sulfide (OCS) on mineral oxides including SiO2,Fe2O3,CaO,MgO,ZnO and TiO2,which are the main components of atmospheric particles,were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS),ion chromatography (IC),temperature-programmed desorption (TPD),X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) methods. The main products and intermediates of the heterogeneous oxidation of OCS on these oxides were identified with in situ DRIFTS and IC. The reaction mechanism and kinetics were also discussed. It is found that the reaction mechanism on these mineral oxides is the same as that on Al2O3 for the same final products and the intermediates at room temperature. Namely,OCS can be catalytically oxidized to produce surface SO42- species and gaseous CO2 through the surface hydrogen thiocarbonate (HSCO2-) and HSO3- species. The activity series for heterogeneous oxidation of OCS follows: Al2O3 ≈ CaO > MgO > TiO2 ≈ ZnO > Fe2O3 > SiO2. The specific area,basic hydroxyl and surface basicity of these oxides have effect on the reactivity. This study suggests that heterogeneous reactions of OCS on mineral dust may be an unneglectable sink of OCS.     

Heteroseneous oxidation of carbonyl sulfide on mineral oxides

Heterogeneous oxidation of carbonyl sulfide （OCS） on mineral oxides including SiO2, Fe2O3, CaO, MgO, ZnO and TiO2, which are the main components of atmospheric particles, were investigated using in situ diffuse reflectance infrared Fourier transform spectroscopy （in situ DRIFTS）, ion chromatography （IC）, temperature-programmed desorption （TPD）, X-ray diffraction （XRD） and Brunauer-Emmett-Teller （BET） methods. The main products and intermediates of the heterogeneous oxidation of OCS on these oxides were identified with in situ DRIFTS and IC. The reaction mechanism and kinetics were also discussed. It is found that the reaction mechanism on these mineral oxides is the same as that on Al2O3 for the same final products and the intermediates at room temperature. Namely, OCS can be catalytically oxidized to produce surface SO4^2- species and gaseous CO2 through the surface hydrogen thiocarbonate （HSCO2-） and HSO; species. The activity series for heterogeneous oxidation of OCS follows： Al2O3 ≈ CaO 〉 MgO 〉 TiO2 ≈ ZnO 〉 Fe2O3 〉 SiO2. The specific area, basic hydroxyl and surface basicity of these oxides have effect on the reactivity. This study suggests that heterogeneous reactions of OCS on mineral dust may be an unneglectable sink of OCS.     

Selective catalytic reduction of NO x by hydrogen over modified Pd/TiO2-Al2O3 catalyst under lean-burn conditions

A series of Ni, Sn and Ca modified Pd/TiO2-Al2O3 catalysts were prepared by the incipient wetness impregnation method and their catalytic performance for the selective catalytic reduction of NOx by H2 was evaluated. The results showed that the NOx conversion and N2 selectivity were improved over Pd-Sn/TiO2-Al2O3 and Pd-Ni/TiO2- Al2O3 catalysts above 200 ℃. More importantly, the N2 selectivity and high-temperature activity of Pd-Sn/TiO2- Al2O3 catalyst was far superior to the single Pd/TiO2-Al2O3 catalyst. The optimal Sn loading was 2 wt.%. X-ray diffrac- tion （XRD） results showed that the interaction between Pd and Sn promotes the dispersion of Pd over TiO2-Al2O3. Temper- ature-programmed reduction （Ha-TPR） results demonstrated that the addition of Sn contributes to the formation of PdO and improving the redox property of Pd/TiOz-Al2O3. The addi- tives of Ni and Sn also facilitated the absorption of NOx and the oxidation of NO to NOa, which play important roles in the selective catalytic reduction of NOx by hydrogen.     

Low-temperature SCR activity and SO_2 deactivation mechanism of Ce-modified V_2O_5–WO_3/TiO_2 catalyst

The promotion effect of ceria modi fi cation on the low-temperature activity of V2O5-WO3/TiO2 catalyst was evaluated for the selective catalytic reduction of NO with NH3(NH3-SCR). The catalytic activity of 1 wt% V2O5-WO3/TiO2 was signi fi cantly enhanced by the addition of 8 wt%ceria, which exhibited a NO x conversion above 80% in a broad temperature range 190–450 1C. This performance was comparable with 3 wt%V2O5-WO3/TiO2, indicating that the addition of ceria contributed to reducing the usage of toxic vanadia in developing low-temperature SCR catalysts. Moreover, V1 Ce WTi exhibited approximately 10% decrease in NOx conversion in the presence of 60 ppm SO2. The characterization results indicated that active components of V, W and Ce were well dispersed on TiO2 support. The synergetic interaction between Ce and V species by forming V–O–Ce bridges enhanced the reducibility of VCe WTi catalyst and thus improved the low-temperature activity. The sulfur poisoning mechanism was also presented on a basis of the designed TPDC(temperature-programmed decomposition) and TPSR(temperatureprogrammed surface reaction) experiments. The deposition of(NH4)2SO4on V1 Ce WTi catalyst was much smaller compared with that on V1 Ti.On the other hand, the oxidation of SO2 to SO3was signi fi cantly promoted on the CeO2-modi fi ed catalyst, accompanied by the formation of cerium sulfates. Therefore, the deactivation of this catalyst was mainly attributed to the vanishing of the V–Ce interaction and the sulfation of active ceria.     

Synergistic effect between ceria and tungsten oxide on WO3–CeO2–TiO2 catalysts for NH3-SCR reaction

WO3–CeO2–TiO2 catalysts for NO (nitrogen monoxide) reduction by ammonia were prepared by a sol–gel method. The catalysts were characterized by BET, XRD, Raman, NH3/NO adsorption and H2-TPR to investigate the relationships among the catalyst composition, structure, redox property, acidity and deNOx activity. WO3–CeO2–TiO2 catalysts show a high activity in a broad temperature range of 200–480 1C. The low-temperature activity of catalysts is sensitive to the catalyst composition especially under low-O2-content atmospheres. It may be related to the synergistic effect between CeOx and WOx in the catalysts. On one hand, the interaction between ceria and tungsten oxide promotes the activation of gaseous oxygen to compensate the lattice oxygen consumed in NH3-SCR (selective catalytic reduction) reaction at low temperatures. Meanwhile, the Br?nsted acid sites mainly arise from tungsten oxides, Lewis acid sites mainly arise from ceria. Both of the Br?nsted and Lewis acid sites facilitate the adsorption of NH3 on catalysts and improve the stability of the adsorbed ammonia species, which are beneficial to the NH3-SCR reaction.     

Catalysis on Interface of Nano-oxide and Nano-zeolite

1 Results The catalysts which can efficiently hydro-reform higher n-paraffin to lower isoparaffins for environmentally-friendly gasoline were studied. The catalysts were examined by the conversion of n-hexadecane, n-C16H34 to i-C6H14—i-C10H22.The tri-modally nano-porous catalysts composed of (Ni-Mo)/[γ-Al2O3], nano-oxide, and nano-crystalline zeolite had some active and selective performance because of the interface between nano-oxide and nano-zeolite. The catalyst composed of nano-crystalline MFI or BEA zeolite can be more activated with nano-SiO2 than with Al2O3. The catalyst composed of USY (SiO2/Al2O3=12), dealuminated zeolite cannot be activated with nano-SiO2 but with nano-Al2O3. This activation depends on the SiO2/Al2O3 ratio of USY as shown in Fig.1.     

Speciation of the elements and compositions on the surfaces of dust storm particles： The evidence for the coupling of iron with sulfur in aerosol during the long-range transport

The speciation of the elements on the surface of the particles collected during dust storm and non-dust storm in Beijing and Inner Mongolia was studied by XPS. The major species of iron on the surface were oxides, sulfate, silicate,FeOOH and minor part sorbed on SiO2/Al2O3. Sulfate is the dominant species of sulfur on the surface. SiO2 and Al2O3 are the main components of Si and Al on the surface respectively.One of the most important findings was that the Fe(Ⅱ) (FeS and FeSO4) produced could account for up to 44.3% and 45.6% of the total Fe on the surface in the aerosol sample collected at that night and next day of the “peak” time of the dust storm occurring on March 20, 2002, while Fe2(SO4)3,one of the Fe(Ⅲ) species on the surface decreased from 67.1% to 49.5% and 48.0% respectively. Both S and Fe enriched on the surface of aerosol particles. Fe(Ⅱ) accounted for 1.3%-5.3% of total Fe in bulk aerosol samples during dust storm. These results provided strong evidence to support the hypothesis of the coupling between iron and sulfur in aerosols during the long-range transport, which would have important impact on the global biogeochemical cycle.     

High temperature oxidation behavior of aluminide on a Ni-based single crystal superalloy in different surface orientations

An investigation on oxidation behavior of coated Ni-based single crystal superalloy in different surface orientations has been carried out at1100 ℃. It has been found that the {100} surface shows a better oxidation resistance than the {110} one, which is attributed that the {110}surface had a slightly higher oxidation rate when compared to the {100} surface. The experimental results also indicated that the anisotropic oxidation behavior took place even with a very small difference in the oxidation rates that was found between the two surfaces. The differences of the topologically close packed phase amount and its penetration depth between the two surfaces, including the ratio of α-Al2O3 after 500 h oxidation, were responsible for the oxidation anisotropy.     

Etching mechanism of barium strontium titanate （BST） thin films in CHF_3/Ar plasma

Reactive ion etching was used to etch barium strontium titanate thin films in a CHF3/Ar plasma.BST surfaces before and after etching were analyzed by X-ray photoelectron spectroscopy to investigate the reaction ion etching mechanism,and chemical reactions had occurred between the F plasma and the Ba,Sr and Ti metal species.Fluorides of these metals were formed and remained on the surface during the etching process.Ti was almost completely removed because the TiF4 by-product is volatile.Minor quantities of Ti?F could still be detected by narrow scan X-ray photoelectron spectra,and Ti?F was thought to be present in the form of a metal-oxy-fluoride.These species were investigated from O1s spectra,and a fluoride-rich surface was formed during etching.BaF2 and SrF2 residues were difficult to remove because of their high boiling point.The etching rate was limited to 12.86 nm/min.C?F polymers were not found on the surface,indicating that the removal of BaF2 and SrF2 was important for further etching.A 1-min Ar/15 plasma physical sputtering was carried out for every 4 min of surface etching,which effectively removed remaining surface residue.Sequential chemical reaction and sputtered etching is an effective etching method for barium strontium titanate films.     

Effect of CuO addition on the sintering temperature and microwave dielectric properties of CaSiO3– Al2O3 ceramics

CuO-doped CaSiO3–1 wt% Al2O3 ceramics were synthesized via a traditional solid-state reaction method, and their sintering behavior,microstructure and microwave dielectric properties were investigated. The results showed that appropriate CuO addition could accelerate the sintering process and assist the densification of CaSiO3–1 wt% Al2O3 ceramics, which could effectively lower the densification temperature from1250 1C to 1050 1C. However, the addition of CuO undermined the microwave dielectric properties. The optimal amount of CuO addition was found to be 0.8 wt%, and the derived CaSiO3–Al2O3ceramic sintered at 1100 1C presented good microwave dielectric properties of εr?7.27,Q f?16,850 GHz and τf? 39.53 ppm/1C, which is much better than those of pure CaSiO3 ceramic sintered at 1340oC(Q f?13,109 GHz).The chemical compatibility of the above ceramic with 30 Pd/70 Ag during the cofiring process has also been investigated, and the result showed that there was no chemical reaction between palladium–silver alloys and ceramics.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

Fe3O4@C nanoparticles as high-performance Fenton-like catalyst for dye decoloration

Water pollution has become serious environmental problem nowadays. Advanced oxidation processes(AOP) have been widely applied in water treatment.However, traditional Fenton reaction based on Fe2﹢-H2O2 system has obvious drawbacks, which limit its applications In this study, magnetic Fe3O4core-C shell nanoparticles(Fe3O4@C NPs) were prepared for the decoloration of methylene blue(MB) via the co-precipitation followed by the hydrothermal dehydrogenation of glucose. Fe3O4@C NPs showed high catalytic activity of the decoloration of MB through the decomposition of H2O2 in Fenton-like reactions. Fe3O4@C NPs had much higher activity than bare Fe3O4 cores, suggesting the coating of carbon enhanced the catalytic activity. The performance of Fe3O4@C NPs was better at lower pH and higher temperature, but was significantly inhibited in the presence of radical scavenger tertiary butanol. Fe3O4@C NPs could be magnetic separated and regenerated, and maintained with very good catalytic activity. The implication for the applications of Fe3O4@C NP-catalyzed Fenton-like reactions in water treatment was discussed.     

等离子体氧化和阳极氧化处理的Ti6Al4V合金的蛋白吸附、细胞活力和腐蚀性能

The hardness, wettability, and electrochemical properties of Ti6Al4V alloy surfaces treated with anodic oxidation and plasma oxidation as well as the viabilities of the different cell lines on the obtained surfaces were investigated. The anodic oxidation was performed for 10 min under 100 V potential, and it resulted in a 0.95 μm thick nanoporous anatase-TiO₂ structure. On the other hand, plasma oxidation was carried out at 650°C for 1 h and resulted in a dense rutile-TiO₂ structure with a thickness of 1.2 μm. While a hardness of HV_0.025 823 and roughness of ~220 nm were obtained by plasma oxidation, those obtained by anodic oxidation were HV_0.025 512 and ~130 nm, respectively. The anodic oxidation process created a more hydrophilic surface with a contact angle of 87.2°. Both oxidation processes produced similar properties in terms of corrosion behavior and showed better resistance than the as-received state in a certain range of potential. Moreover, the surface treatments led to no significant change in the protein adsorption levels, which indicates that the difference in viability between the osteoblast and fibroblast cells was not due to the difference in surface protein adsorption. Given all the factors, the surfaces obtained by anodic oxidation treatment revealed higher cell viability than those obtained by plasma oxidation (p = 0.05).     

Novel approaches to produce Al2O3– TiC/TiCN– Fecomposite powders directly from ilmenite

Al2O3 –TiC/TiCN–Fe composite powders were successfully prepared directly from ilmenite at 1300–1400℃.The effects of Al/C ratio,sintering atmosphere,and reaction temperature and time on the reaction products were investigated.Results showed that the nitrogen atmosphere was bene cial to the reduction of ilmenite and the formation of Al2O3 –TiC/TiCN–Fe composite powders.When the reaction temperature was between 600 and 1100℃,the intermediate products,TiO2,Ti3O5 and Ti4O7 were found,which changed to TiC or TiCN at higher temperature.Al/C ratio was found to affect the reaction process and synthesis products.When Al addition was 0.5 mol,the Al2O3 phase did not appear.The content of carbon in TiCN rose when the reaction temperature was increased.     

Highly dispers ed iron species created on alkali-treated zeolite for ammonia SCR

Alkaline treatment using sodium hydroxide was introduced to obtain a hierarchical pore structure in H-ZSM-5 zeolite.Fe-exchanged zeolite catalysts were prepared by impregnation on the original and alkali-treated zeolites,and were evaluated for NOx reduction by NH3,NO oxidation,and NH3 oxidation reactions.The highly dispersed iron species as active sites can be obtained by controlling the pore structure and particle size of zeolite.Therefore,the Fe/ZSM-5 catalyst treated mildly by sodium hydroxide before iron exchange,which contains amounts of highly dispersed Fe species,obtains over80% NOx conversion at a wide temperature range of 250-500℃.     

The influence of molar ratios of Ce/Zr on the selective catalytic reduction of NOx with NH3 over Fe2O3-WO3/CexZrl-xO2 （0 〈 x 〈 1） monolith catalyst

A series of CexZrl_xO2 （0 ≤ x ≤ 1） with dif- ferent molar ratios of Ce/Zr were syhthesized via coprecip- itation method, and Fe2O3-WO3/CexZrl-xO2 monolithic catalysts were prepared, for selective catalytic reduction of nitrogen oxides by ammonia （NH3-SCR）. The structural properties and redox behavior of the catalysts were com- prehensively characterized by N2 physisorption, X-ray diffraction （XRD）, X-ray photoelectron spectra （XPS）, H2-temperature programmed reduction （H2-TPR） and activity measurement for NH3-SCR. The results showed that the NH3-SCR activities of the catalysts were gradually enhanced by increasing the molar ratios of Ce/Zr, especially the low- temperature catalytic activity and the reaction temperature window. Fe2O3-WO3/Ceo.68Zro.3202 monolithic catalyst presented the best NH3-SCR activity among the investigated catalysts, more than 90 % NOx could be removed in the temperature range of 247-454 ℃ on the catalyst under the gas hourly space velocities of 30,000 h- 1. And it always held more than 99 % N2 selectivity and less than 20 ppm （1 ppm =10-6 L/L ） N20 generation concentration between 200 and 500 ℃, the catalyst also displayed its strong resistance of H20 and SO2. Good textural and structural properties, more surface Fe, Ce and active oxygen were together contributed to the excellent NH3-SCR performance of Fe2O3-WO3/ Ce0.68Zr0.32O2 catalyst.     

Effect of B sites on the catalytic activities for perovskite oxides La_(.6)Sr_(.4)Co_xFe_(1-x)O_(3-δ) as metal-air batteries catalysts

The effect of B sites on the catalytic activities of oxygen evolution reaction(OER)for perovskite oxides La_(0.6)Sr_(0.4)Co_xFe_(1-x)O_(3-δ)(x=0,0.2,0.4,0.6,0.8,1,denoted as LSF,LSCF-28,LSCF-46,LSCF-64,LSCF-82 and LSC,respectively)prepared by a convenient and simple method of electrospinning technique is reported.The prepared La_(0.6)Sr_(0.4)Co_xFe_(1-x)O_(3-δ)catalysts possess almost same crystal structures,similar morphologies(except for the LSC catalyst)and slightly different BET surface areas.Upon the optimization of the Co/Fe atomic ratio,the optimal LSCF-82 catalyst exhibits the OER performance with a low onset potential of 1.541 V,a small Tafel slope of 80.56 mV dec~(-1),a high charge-transfer rate and a large electrochemical surface area in 0.1 M KOH solution.LSCF-82 catalyst exhibits the long-term stability under the catalytic operation condition for 12 h.Such catalytic activity may mainly cause by the synergy of higher catalytic activity Co and lower catalytic activity Fe.Thus,the reasonable optimization of the transition metal composition in B sites for the perovskite oxides is in favor of the improvement of OER performance.     

Alkylation of toluene with 1,3-pentadiene over silica supported aluminum chloride catalyst in an extracting-distilling reactor

The alkylation of toluene with 1,3-pentadiene to produce pentyltoluene is designed to obtain 2,6-dimethylnaphalene for the monomer production of 2,6-naphthalene dicarboxylic acid. The possibility of the reaction is examined by the thermodynamics of the alkylation reaction using Thinh’s group contributions method, and tested over silica supported aluminum chloride catalyst in a newly developed extracting?distilling reactor. The thermodynamics calculation results show that the alkylation reaction is exothermic and can proceed at 298?350 K under normal pressure with an equilibrium constant higher than 106. Based on the thermodynamic calculation and the properties of the reactants and product, the extracting-distilling reactor was designed to allow 1,3-pentadiene to react with toluene at much lower temperature than the boiling point of toluene at the catalyst site. The alkylation product, which has a higher boiling point than that of toluene, is transferred from the catalytic site into the toluene bath and collected. The experimental results show that the reactor functions as designed and promotes the selectivity of the alkylation reaction close to 100%. The effect of raw material ratio of toluene to 1,3-pentadiene and reaction time are discussed in this paper. The suitable catalytic reaction conditions are as follows: at reaction temperature of 338 K and ambient pressure, the reactant ratio of toluene to 1,3-pentadiene is 5:1 for a six-hour reaction.     

Protein adsorption,cell viability and corrosion properties of Ti6Al4V alloy treated by plasma oxidation and anodic oxidation

The hardness, wettability, and electrochemical properties of Ti6Al4V alloy surfaces treated with anodic oxidation and plasma oxidation as well as the viabilities of the different cell lines on the obtained surfaces were investigated. The anodic oxidation was performed for 10 min under 100 V potential, and it resulted in a 0.95 μm thick nanoporous anatase-TiO_2 structure. On the other hand, plasma oxidation was carried out at 650℃ for 1 h and resulted in a dense rutile-TiO_2 structure with a thickness of 1.2 μm. While a hardness of HV_(0.025) 823 and roughness of ～220 nm were obtained by plasma oxidation, those obtained by anodic oxidation were HV_(0.025) 512 and ～130 nm, respectively. The anodic oxidation process created a more hydrophilic surface with a contact angle of 87.2°. Both oxidation processes produced similar properties in terms of corrosion behavior and showed better resistance than the as-received state in a certain range of potential. Moreover, the surface treatments led to no significant change in the protein adsorption levels, which indicates that the difference in viability between the osteoblast and fibroblast cells was not due to the difference in surface protein adsorption. Given all the factors, the surfaces obtained by anodic oxidation treatment revealed higher cell viability than those obtained by plasma oxidation(p = 0.05).     

Effects of Ca on the distribution, structure and morphology of aluminum species in polyaluminum chloride

The flocculation efficiency of polyaluminum chloride (PAC) is closely related to the distribution and structure of its AI species, and Al13 is the optimal species in PAC for flocculation. A series of PAC containing Ca was prepared by adding Ca before and after the basifying reaction. The effects of Ca on the Al species were studied by ^27Al nuclear magnetic resonance (NMR) and atomic force microscope (AFM) techniques. The experimental results show that the introduction of Ca increases the content of Alm and Al13 in PAC and decreases their chemical shifts in NMR spectra due to the electric repulsion between the positive Ca species and AI species and the formation of AI-O-Ca complexes.With the rise of Ca/AI molar ratio, the AI species in PAC tend to scatter. It is observed that the formerly branch-aggregated clusters are tending to form granule-aggregated ones whose diameter gets smaller and smaller, and the floccule aggregates are formed at a higher Ca/Al molar ratio. The introduction of Ca to PAC, which increases the Al13 content, is certainly to enhance the flocculation efficiency of PAC in water treatment.     

Preparation and Catalytic Oxidation Activity on 2-mercaptoethanol of a Novel Catalytic Cellulose Fibres

Cobalt tetra(N-carbonylacylic) aminophthalocyanine was supported on cellulose fibres by graft reaction to obtain a novel polymer catalyst, catalytic cellulose fibres (CCF),and the optimal supporting conditions were pH = 6, 80℃,t = 120 min. The catalytic oxidation activity of CCF towards oxidation of 2-mereaptoethanol (MEA) in aqueous solution was investigated. The experimental results demonstrated that CCF had good catalytic oxidation activity on MEA at room temperature, causing no secondary pollution and remaining efficient for the repetitive tests with no obvious decrease of catalytic activity.