Photocatalytic Degradation of Water-Soluble Dyes by LaCoO_3

Perovskite type oxides LaCoO 3 was prepared by citrate method in granula of 20～30 nm. Using a fluorescent Hg lamp or sunlight as irradiator, the degradation experiments of various water soluble dyes were carried out in the suspension system of LaCoO 3. The results show that the perovskite type oxide LaCoO 3 has good photocatalytic activity. With the study of X ray photoelectron spectroscopy and photoacoustic spectra, its photocatalytic activity is mainly related with the factors such as the d electron structure of ion Co 3+ , Co O binding energy and adsorbed oxygen on the surface etc.

Mechanisms of Enhancement of Photocatalytic Properties and Activity of Nd^(3+)-Doped TiO_2 for Methyl Orange Degradation

Nd^(3+)-doped TiO_2 powders were prepared by the sol-gel method. Their crystal pattern and parameter, the specific surface area, the surface chemical state of Ti and the ratio of O/Ti were characterized. The results show that Nd impurity hinders the crystal transformation, and decreases the relative intensity of (101) peak. The crystallite sizes of Nd^(3+)-doped TiO_2 powders decrease while their specific surface area increase owing to the Nd^(3+) doping. The XPS measurement shows that the content of Ti(Ⅲ) and ratio of O/Ti on their surfaces increase significantly with the increase of Nd^(3+) dosage. The adsorption and photodegradation experiments show that the optimum molar content of Nd^(3+) is 1.2%.

Characterization and CO Catalytic Oxidation of CuO/Ce-Zr-La-O Catalyst

The Ce-Zr-La-O solid solution was prepared by the sol-gel method. Thestructure and the redox behavior of Ce-Zr-La-O solid solution and CuO/Ce-Zr-La-O catalysts wereinvestigated by using XRD, Raman and TPR techniques. The result shows that the reduction capabilityof Ce_(0.7)Zr_(0.3-y)La_yO solid solution is related to content of La. Appropriate content of La canenhance the redox capability of the solid solution. The oxidation activity of the CuO (6 percent)/Ce_(0.7)Zr_(0.15)La_(0.15)O catalyst is the highest. CuO, which finely dispersed and interacted withthe support, is the site of oxidation activity.

Effects of Support on Catalytic Behavior of Combustion Catalyst La_(0.8)Sr_(0.2)CoO_3/γ-Al_2O_3

Combustion catalyst La_(0.8)Sr_(0.2)CoO_3 (LSC) is expected to possess relatively high activity for the oxidation of carbon monoxide and many hydrocarbons. If γ-Al_2O_3 is used as its support, cobalt ions can easily react with γ-Al_2O_3 at not very high temperature to form spinel CoAl_2O_4 or spinel-like, which decreases the activity of the combustion catalyst. In this paper, MgAl_2O_4 and CaAl_2O_4 were pre-coated on γ-Al_2O_3 by impregnation respectively, which formed compound support for LSC. It is shown that, when MgAl_2O_4 layer is covered on the surface of MgAl_2O_4 by impregnation, the entering of cobalt ions into γ-Al_2O_3 lattice is restrained, then LSC formed on the surface of MgAl_2O_4, which leads to a good catalytic activity of xylene complete oxidation. But the layer of MgAl_2O_4 should be thick enough to reach 30% (mass fraction) MgO in the support due to large size particle of MgAl_2O_4 crystalline. If polyvinyl alcohol (PVA) is added into the impregnation solution adequately, MgAl_2O_4 particles formed on the surface of γ-Al_2O_3 are getting smaller, and less amount of MgAl_2O_4 is needed to cover up the surface of γ-Al_2O_3. If CaAl_2O_4 layer substituted for MgAl_2O_4, more closed cover is obtained in virtue of fine particles of CaAl_2O_4. The activity examination shows that smaller particles of MgAl_2O_4 or CaAl_2O_4 can be more effective to hinder cobalt ions entering the lattice of γ-Al_2O_3, and better activities will be obtained.

Preparation and High-Temperature Water-Gas Shift Catalytic Features of La_(1-x)Ce_x FeO_3 Perovskite

Based on water-gas shift reaction mechanism and perovskite compounds characteristics, La_(1- x )Ce_ x FeO_3 (.K) perovskite were designed and prepared as shift catalysts. DTA and XRD results reveal that La_(1- x )Ce_ x FeO_3 can be formed at 730～760 ℃ by mechanic-mix thermal decomposition method. Activity and heat-resisting tests show that La_(1- x )Ce_ x FeO_3 ((.K)) possess high thermal stability if x is less than or equals to 0.5. But when x is greater than 0.5, La_(1- x )Ce_ x FeO_3 (.K) will be converted into ceria and magnetite partially or completely under shift reaction conditions. In the case of x =0.5, the conversion of CO is about 68% at 530 ℃. Potassium can greatly improve the low temperature activity, but slightly reduces the high temperature activity, and has little impact on the thermal stability. La_(0.5)Ce_(0.5)FeO_3 (.K) is a promising chromium-free high temperature shift catalyst.

Catalytic Reduction of SO_2 on CeO_2-La_2O_3 Rare Earth Mixed Compounds

Adding rare earth oxide CeO_2 with variable valences to La_2O_3 formed a mixture of rare earth oxides. By means of dipping CeO_2, La_2O_3 and their mixture, whose carriers were all γ-Al_2O_3, were used as the catalyst for the reduction of SO_2 by CO. The activation process of this catalyst and the impact of temperature and reactant concentration on the activation process were investigated. Using X-ray diffraction, the structure characteristics of catalyst before and after reaction were analyzed to reveal the change of phase structure. The result shows that the rare earth oxide mixtures composing of CeO_2 and La_2O_3, as the catalyst for the reduction of SO_2 by CO, diminish activation temperature 50～100 ℃ less and have higher activity than a single oxide CeO_2 or La_2O_3. The reason possibl is that La_2O_3 goes into in the lattice of CeO_2 to form solid phase complex CeO_2-La_2O_3 and increases the capability of CeO_2-La_2O_3/γ-Al_2O_3 catalyst to store oxygen, which supplies the redox of CeO_2 reaction with a better condition. At the same time, elemental sulfur formed in the redox reaction impels La_2O_3 to be transformed to activation phase La_2O_2S in a lower temperature, which can be explained with the synergism between redox reaction and COS intermediate mechanism reaction.

Preparation, Characterization of CuO/CeO_2 and Cu/CeO_2 Catalysts and Their Applications in Low-Temperature CO Oxidation

CeO2 was synthesized via sol-gel process and used as supporter to prepare CuO/CeO2, Cu/CeO2 catalysts by impregnation method. The catalytic properties and characterization of CeO2, CuO/CeO2 and Cu/CeO2 catalysts were examined by means of a microreactor-GC system, HRTEM, XRD, TPR and XPS techniques. The results show that CuO has not catalytic activity and the activity of CeO2 is quite low for CO oxidation. However, the catalytic activity of CuO/CeO2 and Cu/ CeO2 catalysts increases significantly. Furthermore, the activity of CuO/CeO2 is higher than that of Cu/CeO2 catalysts.

Temperature Programmed Reduction Studies on CeO_2-Containing Catalysts

Temperature programmed reduction (TPR) study was carried out for CeO 2/Al 2O 3 and CeO 2/ZrO 2 catalysts to evaluate oxygen storage property induced by a facile redox cycling of Ce ion. The CeO 2/ZrO 2 catalyst possesses excellent oxygen storage activity at 373 K after reduction above 1173 K although the oxygen storage of CeO 2/Al 2O 3 catalyst after reduction above 1173 K is poor because of the formation of CeAlO 3. Consequently, the oxygen storage on the CeO 2/ZrO 2 catalyst smoothly occurs from low temperatures when the catalyst is reduced even at high temperatures.

Effects of Cerium Oxide on Ni/Al_2O_3 Catalysts for Decomposition of CH_4 and C_2H_4

Characteristics of carbon deposition of CH 4 and C 2H 4 decomposition over supported Ni and Ni Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal semiconductor interaction (MScI) in the Ni Ce catalyst, and the effect of MScI on the carbon deposition of CH 4 decomposition is opposite to that of C 2H 4. A novel model of carbon deposition of CH 4 or C 2H 4 decomposition was proposed.

Effects of Cerium Dopant on Ni-B Amorphous Alloy Catalysts Used in 2-Ethylanthraquinone Hydrogenation

A series of Ce-doped Ni-B amorphous alloy catalysts were prepared by a KBH_4 reduction method, characterized by ICP, BET, XRD, H_2-chemisorption, H_2-TPD, etc., and tested in the hydrogenation of 2-ethylanthraquinone. The results of characterization show that with the addition of Ce the amount of H_2-chemisorption and H_2-TPD areas first increases markedly and then decreases with the maximum appears at the atomic ratio of Ce to Ni of 0.036. The hydrogenation activity also shows the same trend. The effects of Ce are attributed to its dispersion of Ni particles, resulting in the formation of more surface Ni centers. However, much higher Ce contents may result in the decrease of the surface Ni contents. After heat treatment at higher temperatures, the amorphous structure of Ni-B is destroyed.

Effects of Heavy Rare Earth Elements on Properties of Amorphous NiB Alloy Catalyst

Gas phase hydrogenation of benzene was selected as probe reaction to study the effects of heavy rare earth elements on the catalytic activity and sulfur resistance of amorphous NiB alloy. XRD, DSC, CO chemical adsorption, TP5 and TPD were used to characterize the bulk and the surface properties of the alloys, respectively. The results indicate that the addition of a small amount of heavy rare earth (HRE) elements obviously improves the activity, thermal stability and sulfur resistance of amorphous NiB alloy. The HRE can alter H 2 adsorption bond strength, increase the surface area of active nickel and the number of active centers over the surface of NiB alloy and it also can decrease the activation energy of NiB alloy for benzene hydrogenation. There are four kinds of adsorbing sites over the surface of NiB and NiBRE, only three kinds of them have concerned with the reaction.

Synthesis of PET and Its Copolymer with Rare Earth Catalysts

A new catalyst system was used in the synthesis of polyethylene terephthalate(PET) and its copolymers, which involved a Ln 3+ containing compound. The catalytic effects were studied, and it was found that the direct esterification reaction of terephthalate acid(TPA) with ethylene glycol(EG) can be accelerated by the addition of Ln 3+ containing compound, which acts as a promoter of the catalyst Sb 2O 3 in polycondensation of bis hydroxyethyl terephthalate(BHET).

Promoter of (Ce-Zr)O_2 Solid Solution Modified by Praseodymia in Three-Way Catalysts

The three way catalysts (TWCs) promoters (Ce Zr)O 2, (Pr Ce Zr)O 2 and (Pr Zr)O 2 were prepared by sol gel like method. They were characterized by XRD, EXAFS and BET surface area determination. The reduction features of the promoters were measured by temperature programmed reduction (TPR) of H 2 to access the potential for the promoters containing praseodymia as oxygen storage component in three way catalyst. The (Pr Zr)O 2 cubic solid solution is formed at high temperature up to 800 ℃, which makes it more reducible than the (Ce Zr)O 2 solid solution. For the (Pr Ce Zr)O 2 samples, the ternary solid solution plays an important role in the reduction process. The performance of the three way catalysts with fully formulated Pt, Pd and Rh is proceeded by using both light off temperature under a stoichiometric gas composition and the conversion of CO, C 3H 6 and NO under changing air/fuel ratio at a constant reaction temperature 400 ℃ . The results indicate that a small amount of praseodymia doping into (Ce Zr)O 2 favors the light off temperature of C 3H 6 and NO, and all the catalysts containing praseodymia obviously exhibits enhanced width of S value for NO conversion at lean region ( S ≥1.00).

Preparation and Characterization of Ce_x Th_(1-x)O_2 Solid Solutions Prepared by Sol-Gel Method

The Ce_xTh_(1-x)O_2 solid solutions were prepared by citrate sol-gel method,and their structure and reduction properties were studied. XRD shows that solid solution with cubicphase formed in all the solid solutions (x = 0.2, 0.5, 0.8) Ce_xTh_(1-x)O_2. Raman spectrum showsthat Ce-Th complex oxides can promote the formation of oxygen vacancies. Two reduction peaks appearin the TPR profiles of Ce_xTh_(1-x)O_2 solid solution. The a peak is attributed to the reduction ofCe^(4+) on the surface, and the β peak is attributed to the reduction of bulk CeO_2. Theincorporation of Th atom into CeO_2 improves the reduction of CeO_2. Ce_xTh_(1-x)O_2 mixed oxidesare promising materials for oxygen vacancies produced, as well as catalysts for many reactionsinvolved oxygen, such as the catalysts for three-way reactions for reducing the releasing pollutantsor combustion of VOCs.

Study on Modification of Sm_2O_3 by Ni/Sepiolite Catalyst

A series of Ni Sm/sepiolite catalysts were prepared by impregnation. The modification of Sm 2O 3 for Ni/sepiolite was investigated by TPR, XPS and poisoning of CS 2, respectively. The results indicate that the addition of Sm 2O 3 improves the activity of hydrogenation and anti poisoning ability of Ni/sepiolite catalyst, and it also increases the dispersion of nickel atoms over support and the amount of active nickel atoms in catalyst. Effect of Sm 2O 3 on Ni/sepiolite catalyst includes not only electronic effect but also steric effect, whereas electronic effect seems to be principal.

Effects of Ce^(3+),Nd^(3+),Gd^(3+), Tb^(3+) and Lu^(3+) ions on Formation of CaCO_3

The effects of lanthanides at various concentrations on CaCO 3 crystal growth were studied by X ray diffraction (XRD), infrared spectra (IR), X ray photoelectric energy spectra (XPS) and inductively coupled plasma mass spectrometry (ICP MS). It was found that the calcite, a stable form of CaCO 3 in thermodynamics, is the predominant species. The research indicates that lanthanide ions (Ln 3+ ) can partly substitute the Ca 2+ in the lattice of CaCO 3 crystals, and change the crystal characterization and direct the ordinal growth of CaCO 3 crystals.

Promotion Effect of Lantanum ions on Co/SiO_2 Catalysts Prepared via Solvated Metal Atom Impregnation Method

order to assess the promotional effects of La3+ on CO hydrogenation of Co/SiO2 catalyst, solvated metal atom impregnation (SMAI) method was used to prepare unpromoted 10% (mass fraction) Co/SiO2 and a series of La3+-promoted 10% (mass fraction) Co/SiO2 catalyst with different La/Co atomic ratios (0.1, 0.3, 0.5). X-ray diffraction (XRD), and CO chemisorption measurements show that the cobalt particle size decreases as the La/Co ratios increase. X-ray photoelectron spectrescopy indicates that cobalt is in zero-valent state for all the samples. Catalytic test shows that the catalytic activity of La3+-promoted Co/SiO2 in CO hydrogenation is higher than that of unpromoted Co/SiO2, and enhances with the La/Co ratios increase. La3+ promotion also causes the enhanced selectivity of Co/SiO2 catalyst for higher hydrocarbon products.