钾掺杂对铈锆固溶体催化性能的影响

为研究钾掺杂对铈锆固溶体催化性能的影响,以Ce0.7Zr0.3O2为基体制备了一系列钾掺杂的铈锆固溶体xK-Ce0.7Zr0.3O2(x=0.05、0.10、0.15、0.20、0.25、0.30)催化剂样品,通过程序升温氧化(TPO)过程进行活性评价,并通过XRD、BET、H2-TPR和O2-TPD进行分析表征。结果表明,采用溶胶凝胶法制备的催化剂的催化性能比络合燃烧法所制备的稍好;当钾的掺杂量为0.10≤x≤0.30时,xK-Ce0.7Zr0.3O2催化碳烟颗粒燃烧的活性得到提高,起燃温度和最大燃烧速率温度分别在315℃和375℃附近,明显优于Ce0.7Zr0.3O2;掺杂钾后的催化剂样品均能形成萤石结构,并且随钾掺杂量的增大比表面积减小。     

钙钛矿型La0.8Sr0.2MnO3催化剂的硫中毒机制及中毒催化剂的再生研究

采用共沉淀法制备钙钛矿型La0.8 Sr0.2 MnO3催化剂,以甲苯的催化燃烧为模型反应,考察了SO2对La0.8 Sr0.2 MnO3催化剂的毒性效应.通过X射线衍射(XRD)光谱、比表面积(BET)和X射线电子能谱(XPS)表征硫中毒前后催化剂的结构和理化性质.结果表明,SO2在La0.8 Sr0.2 MnO3表...     

Removing and recovering gas-phase elemental mercury by Cu(x)Co(3-x)O(4) (0.75< or = x < or =2.25) in the presence of sulphur compounds

The Hg(0) oxidation ability and reusability of Cu(x)Co(3-x)O(4) were investigated in an attempt to improve SO(2) anti-poisoning ability of metal oxide and produce more economic and effective sorbents for the control of Hg(0) emission from combustion processes. The influence of copper content on Cu(x)Co(3-x)O(4)'s (0.75< or = x < or =2.25) oxidation ability of Hg(0) in the presence of SO(2) was investigated. According to the X-ray diffraction, Brunauer-Emmett-Teller (BET) and mass balance analysis on mercury, we found that Cu(1.5)Co(1.5)O(4) showed the highest S(BET) and best Hg(0) oxidation ability. With continuous increase of x from 0.75 to 2.25, Cu(x)Co(3-x)O(4)'s SO(2) anti-poisoning ability increased. The analysis results of the X-ray photoelectron spectroscopy manifested that the adsorptive mercury species on spent Cu(1.5)Co(1.5)O(4) was HgO. The spent Cu(1.5)Co(1.5)O(4) could be regenerated by thermal decomposition at 673K and regenerated Cu(1.5)Co(1.5)O(4) showed higher Hg(0) oxidation ability due to Hg-doping. Regenerated enrichment Hg(0) was collected using activated carbon at an ambient temperature to eliminate the secondary pollution.     

Catalytic destruction of dichloromethane using perovskite-type oxide catalysts

Dichloromethane (DCM, also known as methylene chloride [CH2Cl2]) is often present in industrial waste gas and is a valuable chemical product in the chemical industry. This study addresses the oxidation of airstreams that contain CH2Cl2 by catalytic oxidation in a tubular fixed-bed reactor over perovskite-type oxide catalysts. This work also considers how the concentration of influent CH2Cl2 (Co = 500-1000 ppm), the space velocity (GHSV = 5000-48,000 1/hr), the relative humidity (RH = 10-70%) and the concentration of oxygen (O2 = 5-21%) influence the operational stability and capacity for the removal of CH2Cl2. The surface area of lanthanum (La)-cobalt (Co) composite catalyst was the greatest of the five perovskite-type catalysts prepared in various composites of La, strontium, and Co metal oxides. Approximately 99.5% CH2Cl2 reduction was achieved by the catalytic oxidation over LaCoO3-based perovskite catalyst at 600 degrees C. Furthermore, the effect of the initial concentration and reaction temperature on the removal of CH2Cl2 in the gaseous phase was also monitored. This study also provides information that a higher humidity corresponds to a lower conversion. Carbon dioxide and hydrogen chloride were the two main products of the oxidation process at a relative humidity of 70%.     

La1-x Cex Cuy Mn1-yO3／HZSM-5催化剂低温去除柴油机碳烟和NOx

为实现对柴油机碳烟和NOx的低温同步去除,采用柠檬酸络合法制备分子筛负载钙钛矿型金属复合氧化物催化剂,应用x衍射分析仪（XRD）和电镜扫描仪（SEM）对催化剂性能进行表征,并在微型固定床反应器中对催化剂低温去除碳烟和NOx进行活性评价。利用程序升温反应（TPR）技术,进行催化剂活性评价、柴油机负荷和排放等特性实验。结果表明,A位用适量Ce部分取代La,B位用适量cu部分取代Mn,可使碳颗粒燃烧温度降低,CO2选择性好,NOx转化率升高。La0.4 Ce0.6 Cu0.2 Mn0.8O3／HZSM-5催化剂的最大NOx转化率为81．0％,Ti、Tm和Tf分别为250、350和475℃,表明该催化剂具有较好的催化活性,能在低温条件下去除碳烟和NOx。     

The promoter effect and a rate expression of the catalytic incineration of (CH3)2S2 over an improved CuO-MoO3/gamma-Al2O3 catalyst

The CuO-MoO3/gamma-Al2O3 catalyst, confirmed previously as having good activity in the catalytic incineration of (CH3)2S2, was employed as the principal catalyst in this study. With the aim of improving catalyst activity and resistance to deactivation by sulfur compounds, a promoter was added either before adding the precursors of Cu and Mo or together with Cu and Mo onto the gamma-Al2O3. Promoters included transition metals and elements from groups IA-VIIA in the chemical periodic table. Experimental results reveal Cr2O3 as the most effective promoter, with an optimal composition of 5 wt.% Cu, 6 wt.% Mo and 4 wt.% Cr (designated as Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3). Knowing that higher acidity can improve activity, we further investigated the effect of acid treatment on the performance of the Cu(5)-Mo(6)-Cr(4)/gamma-Al2O3 catalyst. Experimental results indicate the H2SO4-treated catalyst (Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3) has a better activity and durability. A study for finding an appropriate rate expression for the catalytic incineration of (CH3)2S2 by Cu(5)-Mo(6)-Cr(4)/sulfated-gamma-Al2O3 was carried out in a differential reactor. The results show that the Mars-Van Krevelen model is applicable to this destructive oxidation reaction. Results additionally reveal that competitive adsorption of CH4 reduces conversion of (CH3)2S2.     

Incinerating volatile organic compounds with ferrospinel catalyst MnFe2O4: an example with isopropyl alcohol

This paper concerns the incineration of isopropyl alcohol (IPA) using the ferrospinel catalyst MnFe2O4. It covers the preparation of the ferrospinel catalyst, the screening of catalytic activity, catalytic incineration testing, and 72-hr decay testing of the catalyst. The experimental results of catalyst screening reveal that the Mn/Fe catalyst is the best of five prepared catalysts (chromium/iron [Cr/Fe], manganese/iron [Mn/Fe], zinc/iron [Zn/Fe], nickel/iron [Ni/Fe], and pure magnetite [Fe3O4]). In tests of the catalytic incineration system used to convert IPA, 98% conversion was obtained at a space velocity of 24,000 hr(-1), an oxygen (O2) content of 21%, 1700 ppm of IPA, and a reaction temperature of 200 degrees C.     

Superior pillared clay catalysts for selective catalytic reduction of nitrogen oxides for power plant emission control

Fe(3+)-, Cr(3+)-, Cu(2+)-, Mn(2+)-, Co(2+)-, and Ni(2+)-exchanged Al2O3-pillared interlayer clay (PILC) or TiO2-PILC catalysts are investigated for the selective catalytic reduction (SCR) of nitric oxide by ammonia in the presence of excess oxygen. Fe(3+)-exchanged pillared clay is found to be the most active. The catalytic activity of Fe-TiO2-PILC could be further improved by the addition of a small amount of cerium ions or cerium oxide. H2O and SO2 increase both the activity and the product selectivity to N2. The maximum activity on the Ce-Fe-TiO2-PILC is more than 3 times as active as that on a vanadium catalyst. Moreover, compared to the V2O5-WO3/TiO2 catalyst, the Fe-TiO2-PILC catalysts show higher N2/N2O product selectivities and substantially lower activities (by approximately 85%) for SO2 oxidation to SO3 under the same reaction conditions. A 100-hr run in the presence of H2O and SO2 for the CeO2/Fe-TiO2-PILC catalyst showed no decrease in activity.     

Catalytic wet-air oxidation of a chemical plant wastewater over platinum-based catalysts.

Catalytic wet-air oxidation (CWAO) of wastewater (chemical oxygen demand [COD] = 1800 mg O2/dm3) from a fine chemicals plant was investigated in a fixed-bed reactor at T = 393-473 K under total pressure of 5.0 or 8.0 MPa. Catalysts containing 0.3% wt. of platinum deposited on two supports, mixed silica-titania (SM1) and carbon black composites (CBC) were used. The CBC-supported catalyst appeared to be more active than the SM1-supported one. A slow decrease of activity of the platinum on SM1 (Pt-SM1) during the long-term operation is attributed to recrystallization of titania and leaching of a support component, while the Pt-CBC catalyst is deteriorated, owing to combustion of the support component. The power-law-kinetic equations were used to describe the rate of COD removal at CWAO over the catalysts. The kinetic parameters of COD reduction for the wastewater were determined and compared with the kinetic parameters describing phenol oxidation over the same catalysts. Rates of COD removal for the wastewater were found higher than those for phenol oxidation over the same catalysts and under identical operating conditions.     

各类VOCs在蜂窝陶瓷型La0.8Sr0.2MnO3催化剂上的催化燃烧性能

以涂有CeO2-ZrO2固溶体的堇青石蜂窝状陶瓷为载体,用浸渍法制备堇青石蜂窝陶瓷型整体La0.8Sr0.2MnO3催化剂,测试了该催化剂催化燃烧各类VOCs的特性。研究表明,VOCs催化燃烧的难易程度为：含氯烃〉烷烃〉酸〉芳烃〉酮〉酯〉醇〉醛。La0.8Sr0.2MnO3催化剂对含氧有机化合物具有较好的催化活性,完全燃烧温度均在280℃之内。通过关联VOCs的理化性质,发现VOCs在La0.8Sr0.2MnO3催化剂上的反应活性与VOCs分子中最弱C—H键键能和VOCs分子极性密切联系。     

Kinetic assessment of the potassium ferrate(VI) oxidation of antibacterial drug sulfamethoxazole

Sulfamethoxazole (SMX), a worldwide-applied antibacterial drug, was recently found in surface waters and in secondary wastewater effluents, which may result in ecotoxical effects in the environment. Herein, removal of SMX by environmentally-friendly oxidant, potassium ferrate(VI) (K(2)FeO(4)), is sought by studying the kinetics of the reaction between Fe(VI) and SMX as a function of pH (6.93-9.50) and temperature (15-45 degrees C). The rate law for the oxidation of SMX by Fe(VI) is first-order with respect to each reactant. The observed second-order rate constant decreased non-linearly from 1.33+/-0.08 x 10(3) M(-1)s(-1) to 1.33+/-0.10 x 10(0) M(-1)s(-1) with an increase of pH from 7.00 to 9.50. This is related to protonation of Fe(VI) (HFeO(4)(-) <==> H(+) + FeO(4)(2-); pK(a,HFeO(4)) = 7.23) and sulfamethoxazole (SH <==> H(+) + S(-); pK(a,SH)=5.7). The estimated rate constants were k(11)(HFeO(4)(-) + SH) = 3.0 x 10(4) M(-1)s(-1), k(12)(HFeO(4)(-) + S(-)) = 1.7 x 10(2) M(-1)s(-1), and k(13) (FeO(4)(2-) + SH) = 1.2 x 10(0) M(-1)s(-1). The energy of activation at pH 7.0 was found to be 1.86+/-0.04 kJ mol(-1). If excess potassium ferrate(VI) concentration (10 microM) is used than the SMX in water, the half-life of the reaction using a rate constant obtained in our study would be approximately 2 min at pH 7. The reaction rates are pH dependent; thus, so are the half-lives of the reactions. The results suggest that K(2)FeO(4) has the potential to serve as an oxidative treatment chemical for removing SMX in water.     

Catalytic degradation of Orange II by UV-Fenton with hydroxyl-Fe-pillared bentonite in water

Although homogeneous photo-Fenton system is a very efficient method for organic wastewater treatment, it suffers from costly pH adjustment as well as difficult separation of catalysts from aqueous in practical application. Through cation exchange reaction, hydroxyl-Fe-pillared bentonite (H-Fe-P-B) was successfully prepared as a solid catalyst for UV-Fenton to degrade non-biodegradable azo-dye Orange II. Compared with raw bentonite, the content of iron, interlamellar distance and external surface area of H-Fe-P-B increased remarkably. H-Fe-P-B had good photosensitivity and catalyst reactivity. And the catalytic activity of H-Fe-P-B for H(2)O(2) came from hydroxyl-Fe between sheets rather than Fe(3+) or Fe(2+) in tetrahedral or octahedral sheets of bentonite. In UVA-H(2)O(2) system, H(2)O(2) could destroy the azo bond of excited Orange II molecules but could not effectively mineralize it. After 120 min treatment, 83% discoloration was obtained while only 2% of TOC was removed. When H-Fe-P-B was used as catalyst, a significant degradation of Orange II was observed at the same condition as UVA-H(2)O(2) system. Almost 100% discoloration and more than 60% TOC removal of Orange II could be achieved after 120 min treatment. Because of the strong surface acidity and the electronegativity of H-Fe-P-B, the pH range of this catalyst in the Orange II discoloration could be extended up to 9.5. And this catalyst showed good stability during Orange II degradation in water in wide range of pH (3.0-9.5). These results indicated that the H-Fe-P-B was a promising catalyst for UV-Fenton system.     

Fe2O3-Cr2O3/TiO2系列催化剂的结构和脱硝性能

研究以纳米TiO2为载体,浸渍负载过渡金属氧化物,以CO为还原剂的脱硝催化剂的脱硝性能。实验中以计算量的Ni（NO3）2和Fe（NO3）3混合溶液浸渍纳米TiO2粉末,室温下搅拌30 min至混合均匀,放入旋转蒸发器中,70℃下至水分蒸干为止;所得粉末在550℃下、空气气氛中焙烧4 h即得所需催化剂。用以上方法分别制备2%Fe2O3-10%Cr2O3/TiO2、4%Fe2O3-8%Cr2O3/TiO2、6%Fe2O3-6%Cr2O3/TiO2、8%Fe2O3-4%Cr2O3/TiO2与10%Fe2O3-2%Cr2O3/TiO2等5种催化剂样品。实验结果表明,制备的催化剂具有较好的结构,分散较为均匀。对于CO＋NO反应,Fe2O3-Cr2O3/TiO2系列催化剂具有较好的催化活性,NO的转化率都达到了100%。其中,10%Fe2O3-2%Cr2O3/TiO2样品具有最好的低温活性,H2-TPR结果表明,这是由于10%Fe2O3-2%Cr2O3/TiO2催化剂更易于被CO预还原。     

Methane oxidation in compost-based landfill cover with vegetation during wet and dry conditions in the tropics

The effect of compost and vegetation on methane (CH4) oxidation was investigated during wet and dry conditions in a tropical region. A laboratory-scale experiment was conducted to examine the performance of nonvegetated and vegetated landfill cover systems in terms of CH4 oxidation efficiency. Two types of landfill cover materials (compost and sandy loam) and two species of tropical grasses (Sporobolus virginicus and Panicum repens) were studied for their effect on the CH4 oxidation reaction. It was found that the use of compost as cover material could maintain a high methane oxidation rate (MOR) of 12 mol CH4/m3 x day over a 250-day period. Leachate application showed a positive effect on promoting methanotrophic activity and increasing MOR. A high MOR of 12 mol CH4/m3 x day was achieved when using compost cover with P. repens during wet and dry seasons when leachate irrigation was practiced. In dry conditions, a lower MOR of 8 mol CH4/m3 x day was observed for 80 days.     

Direct N2O decomposition over La2NiO4-based perovskite-type oxides

Direct decomposition of N₂O by perovskite-structure catalysts including La₂NiO₄, LaSrNiO₄, and La_0.7Ce_0.3SrNiO₄ was investigated. The catalysts were prepared by the Pechini method and characterized by x-ray diffraction (XRD), BET, scanning electron microscopy (SEM), and O₂-TPD. Experimental results indicate that the properties of La₂NiO₄ are significantly improved by partially substituting La with Sr and Ce. N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ are 44 and 36%, respectively, at 400ºC. As the temperature was increased to 600ºC, N₂O decomposition efficiency achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ reached 100% at an inlet N₂O concentration of 1,000 ppm, while the space velocity was fixed at 8,000 hr^?1. In addition, effects of various parameters including oxygen, water vapor, and space velocity were also explored. The results indicate that N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ are not significantly affected as space velocity is increased from 8,000 to 20,000 hr^?1, while La_0.7Ce_0.3SrNiO₄ shows better tolerance for O₂ and H₂O_(g). On the other hand, N₂ yield with LaSrNiO₄ as catalyst can be significantly improved by doping Ce. At a gas hour space velocity of 8,000 hr^?1, and a temperature of 600ºC, high N₂O decomposition efficiency and N₂ yield were maintained throughout the durability test of 60 hr, indicating the long-term stability of La_0.7Ce_0.3SrNiO₄ for N₂O decomposition.

Implications:Nitrous oxide (N₂O) not only has a high global warming potential (GWP₁₀₀ = 310), but also potentially destroys ozone in the stratosphere. Pervoskite-type catalysts including La₂NiO₄, LaSrNiO₄, and La_0.7Ce_0.3SrNiO₄ are applied for direct N₂O decomposition. The results show that N₂O decomposition can be enhanced as Sr and Ce are doped into La₂NiO₄. At 600ºC, N₂O decomposition efficiencies achieved with LaSrNiO₄ and La_0.7Ce_0.3SrNiO₄ reach 100%, demonstrating high activity and good potential for direct N₂O decomposition. Effects of O₂ and H₂O_(g) contents on catalytic activities are also evaluated and discussed.     

Performance of the supported copper oxide catalysts for the catalytic incineration of aromatic hydrocarbons

A fixed bed reactor was used to assess the catalytic incineration of toluene by various transition-metal oxide species supported on gamma-Al(2)O(3). CuO/gamma-Al(2)O(3) was found to be the most active of seven catalysts investigated. The CuO species, with a Cu content of 5% (wt), was hence used with four different supports (CeO(2), gamma-Al(2)O(3), TiO(2) and V(2)O(5)) in order to define the optimal combination. Results of the catalytic incineration of toluene, X-ray diffraction (XRD) analysis, oxygen-temperature programmed desorption (O(2)-TPD), toluene-temperature programmed desorption (toluene-TPD) and hydrogen-temperature programmed reduction (H(2)-TPR) showed that CuO/CeO(2) was the most active catalyst, followed by CuO/gamma-Al(2)O(3). The activity of CuO/CeO(2) with respect to the VOC molecule was observed to follow this sequence: toluen>p-xylene>benzene. The addition of water vapor or CO(2) significantly inhibited the activity of the CuO/CeO(2) and CuO/gamma-Al(2)O(3) catalysts. The inhibiting effect of both was reversible for CuO/gamma-Al(2)O(3). For CuO/CeO(2), the inhibiting effect of CO(2) was reversible and even insignificant at a higher temperature (220 degrees C), but the effect of H(2)O vapor was somewhat irreversible at lower incineration temperatures (220 degrees C). For complete oxidation of toluene, the required reaction temperature increased with gas hourly space velocity (GHSV) and toluene inlet concentration.     

The kinetics of catalytic incineration of dimethyl sulfide and dimethyl disulfide over an MnO/Fe2O3 catalyst

The catalytic incineration of dimethyl sulfide and dimethyl disulfide [(CH3)2S and (CH3)2S2] over an MnO/Fe2O3 catalyst was carried out in a bench-scale catalytic incinerator. Three kinetic models (i.e., the power-rate law, the Mars and Van Krevelen model, and the Langmuir-Hinshelwood model) were used to analyze the results. A differential reactor design was used for best fit of kinetic models in this study. The results show that the Langmuir-Hinshelwood model may be feasible to describe the catalytic incineration of (CH3)2S and (CH3)2S2. This suggests that the chemical adsorption of O2 molecules is important in this incineration.     

Effects of acid treatments of activated carbon on its physiochemical structure as a support for copper oxide in DeSO(2) reaction catalysts

To enhance the dispersion of active sites, modification of the AC supports with different acid solution might result in various surface oxygen groups which act as anchoring sites for metallic precursor to stay and improve the reactivity between AC supports and copper precursor. In the present work, the AC support is tailored with HCl and HNO(3), respectively. The pore structure, surface oxygen groups of the AC support and catalysts as well as catalyst dispersion before and after acid treatments are systematically studied by BET, pH(slurry), TPD, and XRPD analyses. It is found that the order of activity in DeSO(2) reaction is as follows: Cu/AC-HCl>Cu/AC>Cu/AC-HNO(3). The same sequence is also observed for the pore structure of AC supports, the catalyst dispersion, but not for the amounts of CO(2) evolving during TPD experiments of supports. The key role of acid treatment on carbon surface chemistry and pore structure, which are closely related to catalyst dispersion and adsorption capacity, is examined to rationalize these findings. Furthermore, under the NO/NH(3)=1 the NO could be selective catalytic reduction with NH(3) in the presence of O(2), which catalyzed by fresh and spent AC-supported catalyst.     

Mn的氧化价态对Mn／γ-Al2O3催化剂催化臭氧氧化气相低浓度甲苯的影响

采用共沉淀法,以Al2O3为载体制备Mn／γ-Al2O3和Mn—Ce／Mn／γ-Al2O3催化剂,并分别在N2气氛和O2气氛下焙烧。采用固定床连续流动反应器,研究所制备催化剂在室温条件下催化臭氧氧化甲苯的性能。通过XRD、XPS和FTIR等手段对催化剂的结构和组成进行表征。结果表明,Mn／Mn／γ-Al2O3催化剂具有良好的催化臭氧氧化甲苯和催化臭氧自身分解的性能,共沉淀法制备催化剂的最佳Mn负载量为20％。O2气氛焙烧和Ce的加入,可以有效提高催化剂的活性和寿命。原因是O2气氛焙烧和Ce的加入可以提高Mn的氧化价态。催化剂失活的主要原因是有机副产物在催化剂表面吸附堆积,失活催化剂在550℃、空气气氛下焙烧可恢复催化性能。     

The catalytic incineration of styrene over an Mn2O3/Fe2O3 catalyst

In this study, styrene monomer (SM) was treated by a commercial catalyst, Mn2O3/Fe2O3, in a fixed-bed reactor. The study can be classified into two major parts. First, the effects of operating factors, such as temperature, SM concentration, space velocity, and O2 concentration, on the performance of the catalyst were investigated. Second, two catalyst life tests were carried out to characterize the deactivation effect of SM. The results show that the catalyst results in higher conversion of SM at a higher inlet temperature and higher O2 concentrations. The conversion of SM decreases with increasing SM concentration and space velocity. From the statistical analysis of the data, we find that temperature is the most important factor on the catalytic incineration. Oxygen concentration, SM concentration, and space velocity are significant parameters as well. This paper also provides information on the deactivation effect of SM. The catalysts were characterized by surface and pore-size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron spectroscopy for chemical analysis (ESCA) before and after the tests. The results show that the catalytic deactivation may be caused by carbon coating, and the pore size and surface area of the catalyst are smaller after deactivation.