Effect of Oxygen Capacity and Oxygen Mobility of Pure Bismuth Molybdate and Multicomponent Bismuth Molybdate on their Catalytic Performance in the Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene

Pure bismuth molybdate (γ-Bi₂MoO₆) and multicomponent bismuth molybdate (Co₉Fe₃Bi₁Mo₁₂O₅₁) catalysts were prepared by a co-precipitation method, and were applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. The Co₉Fe₃Bi₁Mo₁₂O₅₁ catalyst showed a better catalytic performance than the γ-Bi₂MoO₆ catalyst in terms of conversion of n-butene and yield for 1,3-butadiene, indicating that the multicomponent bismuth molybdate was more efficient than the pure bismuth molybdate in the oxidative dehydrogenation of n-butene. It was revealed that the crucial factor determining the catalytic performance of Bi–Mo-based catalyst in the oxidative dehydrogenation of n-butene is not the amount of oxygen in the catalyst involved in the reaction (oxygen capacity) but the intrinsic mobility of oxygen in the catalyst involved in the reaction (oxygen mobility). The enhanced catalytic performance of Co₉Fe₃Bi₁Mo₁₂O₅₁ was due to its facile oxygen mobility.     

Catalytic performance of multicomponent bismuth molybdates (NiXFe3Bi1Mo12O42+X) in the oxidative dehydrogenation of C4 raffinate-3 to 1,3-butadiene: Effect of nickel content and acid property

Multicomponent bismuth molybdate (Ni_XFe₃Bi₁Mo₁₂O_42+X) catalysts were prepared by a co-precipitation method with a variation of nickel content, and were applied to the oxidative dehydrogenation of C₄ raffinate-3 to 1,3-butadiene. Conversion of n-butene and selectivity for 1,3-butadiene over Ni_XFe₃Bi₁Mo₁₂O_42+X catalysts showed volcano-shaped curves with respect to nickel content. As a consequence, yield for 1,3-butadiene also showed a volcano-shaped curve with respect to nickel content. Among the catalysts tested, Ni₉Fe₃Bi₁Mo₁₂O₅₁ showed the best catalytic performance. Acid properties of Ni_XFe₃Bi₁Mo₁₂O_42+X catalysts were measured by NH₃-TPD experiments, with the aim of correlating the catalytic performance with the acid property of the catalysts. It was observed that either total acidity or acid strength was not directly correlated with the catalytic performance of Ni_XFe₃Bi₁Mo₁₂O_42+X catalysts. However, the conversion of n-butene was increased with increasing surface acidity of the catalyst. The largest surface acidity of the Ni₉Fe₃Bi₁Mo₁₂O₅₁ catalyst was responsible for its enhanced catalytic performance in the oxidative dehydrogenation of C₄ raffinate-3. The facile oxygen mobility of the γ-Bi₂MoO₆ phase in the Ni₉Fe₃Bi₁Mo₁₂O₅₁ catalyst also played an important role in enhancing the catalytic performance of the Ni₉Fe₃Bi₁Mo₁₂O₅₁ catalyst.     

Oxidative Dehydrogenation of C4 Raffinate-3 to 1,3-Butadiene in a Dual-bed Reaction System Comprising ZnFe2O4 and Co9Fe3Bi1Mo12O51 Catalysts: A Synergistic Effect of ZnFe2O4 and Co9Fe3Bi1Mo12O51 Catalysts

Oxidative dehydrogenation of C₄ raffinate-3 to 1,3-butadiene was carried out in a dual-bed reaction system comprising ZnFe₂O₄ and Co₉Fe₃Bi₁Mo₁₂O₅₁ catalysts in order to investigate a synergistic effect of these two catalysts. Conversion of n-butene and yield for 1,3-butiadene obtained in a dual-bed reaction system comprising ZnFe₂O₄ (first-bed) and Co₉Fe₃Bi₁Mo₁₂O₅₁ (second-bed) were higher than those obtained in a single-bed reaction system using either ZnFe₂O₄ or Co₉Fe₃Bi₁Mo₁₂O₅₁. 1-Butene-TPD and 2-butene-TPD measurements revealed that ZnFe₂O₄ catalyst retained more selective oxygen species for the reaction with 2-butene than for the reaction with 1-butene, while Co₉Fe₃Bi₁Mo₁₂O₅₁ catalyst retained more selective oxygen species for the reaction with 1-butene than for the reaction with 2-butene. The synergistic effect of ZnFe₂O₄ (first-bed) and Co₉Fe₃Bi₁Mo₁₂O₅₁ (second-bed) catalysts in the oxidative dehydrogenation of C₄ raffinate-3 was attributed to the combination of high catalytic activity of ZnFe₂O₄ for 2-butene and high catalytic activity of Co₉Fe₃Bi₁Mo₁₂O₅₁ for 1-butene.     

Oxidative dehydrogenation of n-butene to 1,3-butadiene over multicomponent bismuth molybdate (M9Fe3Bi1Mo12O51) catalysts: Effect of divalent metal (M)

Multicomponent bismuth molybdate (M^II₉Fe₃Bi₁Mo₁₂O₅₁) catalysts with different divalent metal (M^II = Mg, Mn, Co, Ni, and Zn) were prepared by a co-precipitation method, and were applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. Effect of divalent metal (M^II) on the catalytic performance of M^II₉Fe₃Bi₁Mo₁₂O₅₁ catalysts was investigated. X-ray photoelectron spectroscopy (XPS) measurements were conducted to determine the oxygen mobility of M^II₉Fe₃Bi₁Mo₁₂O₅₁ catalysts. It was found that the catalytic performance of M^II₉Fe₃Bi₁Mo₁₂O₅₁ catalysts was closely related to the oxygen mobility of the catalysts. The yield for 1,3-butadiene was monotonically increased with increasing oxygen mobility of the catalysts. Among the catalysts tested, the Co₉Fe₃Bi₁Mo₁₂O₅₁ catalyst with the highest oxygen mobility showed the best catalytic performance in the oxidative dehydrogenation of n-butene.     

Influence of phosphorous addition on Bi<Subscript>3</Subscript>Mo<Subscript>2</Subscript>Fe<Subscript>1</Subscript> oxide catalysts for the oxidative dehydrogenation of 1-butene

Bi₃Mo₂Fe₁P _x oxide catalysts were prepared by a co-precipitation method and the influence of phosphorous content on the catalytic performance in the oxidative dehydrogenation of 1-butene was investigated. The addition of phosphorous up to 0.4mole ratio to Bi₃Mo₂Fe₁ oxide catalyst led to an increase in the catalytic performance; however, a higher phosphorous content (above P=0.4) led to a decrease of conversion. Of the tested catalysts, Bi₃Mo₂Fe₁P_0.4 oxide catalyst exhibited the highest catalytic performance. Characterization results showed that the catalytic performance was related to the quantity of a π-allylic intermediate, facile desorption behavior of adsorbed intermediates and ability for re-oxidation of catalysts.     

Aqueous-Phase Hydrogenolysis of Glycerol to 1,3-propanediol Over Pt-H<Subscript>4</Subscript>SiW<Subscript>12</Subscript>O<Subscript>40</Subscript>/SiO<Subscript>2</Subscript>

Abstract  

Hydrogenolysis of glycerol to 1,3-propanediol in aqueous-phase was investigated over Pt-H₄SiW₁₂O₄₀/SiO₂ bi-functional catalysts with different H₄SiW₁₂O₄₀ (HSiW) loading. Among them, Pt-15HSiW/SiO₂ showed superior performance due to the good dispersion of Pt and appropriate acidity. It is found that Br?nsted acid sites facilitate to produce 1,3-PDO selectively confirmed by Py-IR. The effects of weight hourly space velocity, reaction temperature and hydrogen pressure were also examined. The optimized Pt-HSiW/SiO₂ catalyst showed a 31.4% yield of 1,3-propanediol with glycerol conversion of 81.2% at 200 °C and 6 MPa.     

Oxidative Dehydrogenation of <Emphasis Type="Italic">n</Emphasis>-Butene to 1,3-Butadiene over Sulfated ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Catalyst

Oxidative dehydrogenation of n-butene to 1,3-butadiene over sulfated ZnFe₂O₄ catalyst was carried out in a continuous flow fixed-bed reactor. The effect of sulfation on the catalytic performance of ZnFe₂O₄ was investigated. Sulfated ZnFe₂O₄ catalyst showed a better catalytic performance than ZnFe₂O₄ catalyst in the oxidative dehydrogenation of n-butene. Acid–base property of sulfated ZnFe₂O₄ catalyst was measured by TPD experiment, with an aim of correlating the catalytic performance with the surface acid–base property of the catalyst. It was revealed that the catalytic performance of sulfated ZnFe₂O₄ catalyst was closely related to the surface weak-acid density of the catalyst. The enhanced acidity of sulfated ZnFe₂O₄ catalyst was responsible for its high catalytic performance in the oxidative dehydrogenation of n-butene. Thus, sulfation served as an efficient method for improving catalytic performance of ZnFe₂O₄ in the oxidative dehydrogenation of n-butene.     

The influence of the structural and electronic characteristics of palladium on the activity and selectivity of Pd/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Pd-Co/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for the hydrogenation of acetylene hydrocarbons

The influence of the structural and electronic characteristics of nonpromoted and cobalt-promoted Pd catalysts on their adsorption and catalytic properties is studied. It is shown that the conversion of vinylacetylene depends on the dispersion of palladium for both types of catalysts synthesized from acetate and acetylacetonate complexes. The palladium acetylacetonate catalysts have a higher palladium dispersion than the samples obtained from acetate complex solutions, thus leading to a higher conversion of vinylacetylene. It is established that the selectivity of vinylacetylene conversion into 1,3-butadiene on palladium acetate and acetylacetonate catalysts depends on the state of the 3d orbitals of surface Pd atoms. The palladium acetate catalysts are characterized by a higher electron density on the 3d orbital in comparison with the acetylacetonate samples, thus producing higher selectivities of vinylacetylene conversion into 1,3-butadiene. The introduction of cobalt into Pd/δ-Al₂O₃ catalyst synthesized from acetylacetonate complex leads to the formation of bimetallic Pd-Co particles, in which Pd atoms have higher electron density than those in the nonpromoted Pd/δ-Al₂O₃ catalyst, due probably to the donation of electron density from promoter atoms, with a resulting decline in the adsorption ability of bimetallic particles with regard to 1,3-butadiene and hydrogen. As a consequence, the selectivity of vinylacetylene conversion into 1,3-butadiene increases. Requirements for the size, dispersion, and electronic characteristics of the active component in the catalysts for the selective hydrogenation of vinylacetylene are formulated, and two techniques for their synthesis are proposed.     

Synthesis and Thermoelectric Properties of Ceramics Based on Bi<Subscript>2</Subscript>Ca<Subscript>2</Subscript>Co<Subscript>1.7</Subscript>O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> Oxide

Layered ceramics based on bismuth–calcium cobaltite with varied cobalt oxide contents is synthesized by the solid-phase method, the ceramics phase composition is determined, and the microstructure, thermal expansion, electroconductivity, and thermal electromotive force are investigated. The formation of just one compound, ternary oxide composed of Bi₂Ca₂Co_1.7O _y , is established within the quasi-binary Bi₂Ca₂O₅–CoO _z system. The effect of the cobalt oxide content on the Bi₂Ca₂Co _x O _y ceramics’ microstructure and physicochemical properties is analyzed. The single-phased ceramic sample Bi₂Ca₂Co_1.7O _y demonstrated the highest power factor value among all the investigated samples—26.0 μW/(m K²) at a temperature of 300 K. This sample showed the lowest value of the thermal linear expansion coefficient of 9.72 × 10^–6 K^–1.     

Effect of Divalent Metal Component (MeII) on the Catalytic Performance of MeIIFe2O4 Catalysts in the Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene

A series of metal ferrite (Me^IIFe₂O₄) catalysts were prepared by a co-precipitation method with a variation of divalent metal component (Me^II = Zn, Mg, Mn, Ni, Co, and Cu) for use in the oxidative dehydrogenation of n-butene to 1,3-butadiene. Successful formation of metal ferrite catalysts with a random spinel structure was confirmed by XRD, ICP-AES, and XPS analyses. The catalytic performance of metal ferrite catalysts in the oxidative dehydrogenation of n-butene strongly depended on the identity of divalent metal component. Acid properties of metal ferrite catalysts were measured by NH₃-TPD experiments, with an aim of correlating the catalytic performance with the acid property of the catalysts. It was revealed that the yield for 1,3-butadiene increased with increasing surface acidity of the catalyst. Among the catalysts tested, ZnFe₂O₄ catalyst with the largest surface acidity showed the best catalytic performance in the oxidative dehydrogenation of n-butene.     

PLS-based kinetics modeling and optimization of the oxidative coupling of methane over Na<Subscript>2</Subscript>WO<Subscript>4</Subscript>/Mn/SiO<Subscript>2</Subscript> catalyst

Reactor modeling for the oxidative coupling of methane over Na₂WO₄/Mn/SiO₂ catalyst was addressed in the present study. The catalyst loading part was designed to be thicker than the inlet and outlet parts to reduce the rates of side reactions in the gas phase, and the optimal aspect ratio (L to D ratio) for no pressure drop and minimum side reactions was determined in experimental studies. Experiments were also conducted under a variety of operating conditions such as gas hourly space velocity (GHSV), CH₄/O₂ ratio and reaction temperature, and partial least-squares model was applied to predict the performance of the reactor. The validity of the developed model was corroborated by the comparison with experimental data, and normalized parametric sensitivity analysis was carried out. Finally, the genetic algorithm (GA) was applied to determine the optimal conditions for maximum production of ethane and ethylene.     

Thermal behavior of layered perovskite-like compounds in the Bi<Subscript>4</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript>-BiFeO<Subscript>3</Subscript> system

The thermal properties of compounds of the general formula Bi _{m + 1} Fe _{m ? 3} Ti₃O_{3m + 3}, which are layered perovskite-like phases of the Aurivillius type, are investigated as a function of their composition. It is demonstrated that the temperature of decomposition of the Bi _{m + 1} Fe _{m ? 3} Ti₃O_{3m + 3} compounds decreases with an increase in the thickness of perovskite-like layers alternating in the structure and that the composition dependence of the temperature of the structural transition observed in these compounds exhibits a more complex behavior. The linear thermal expansion coefficients of all the compounds under investigation are found to be virtually independent of the composition.     

Research of mica/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> pearlescent pigment by co-precipitation

Experiments on preparation of mica/Fe₃O₄ pearlescent pigment were performed to discuss influences of several crucial parameters on final products. The samples were characterized by XRD, HRSEM, FTIR and color measurement, the content of Fe₃O₄ on the mica surface was also analyzed by XPS. It was found that the smoothness, compactness and colour deepness of the coating were influenced by different pH values and temperatures. The optimum preparation parameters of mica/Fe₃O₄ pearlescent pigment were obtained: the value of pH ≥ 9.2; the concentration of sodium hydroxide was 0.5 mol/l; the concentration ratio of Fe³⁺ to Fe²⁺ was 1.6 : 1; the velocity of magnetic stirring was 138 ≤ v ≤ 151 r/min; reaction temperature was 70–80°C; calcination temperature was 350°C and calcination time was 3 h.     

Heterogeneous Fenton degradation of Orange II by immobilization of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles onto Al-Fe pillared bentonite

A novel catalyst, Fe₃O₄ nanoparticle decorated Al-Fe pillared bentonite (Fe₃O₄/Al-Fe-P-B), was prepared by in situ precipitation oxidization method. The catalyst was characterized by SEM, XRD and Raman spectroscopy. The Fe₃O₄ nanoparticles mainly exist on the surface or enter into the pore of bentonite, with better dispersing and less coaggregation. The catalytic activity of Fe₃O₄/Al-Fe-P-B was investigated in the degradation of Orange II (OII) by heterogeneous Fenton-like process. The effects of initial concentration of hydrogen peroxide, catalyst loading, temperature and initial pH on the degradation of OII were investigated. The Fe₃O₄/Al-Fe-P-B showed higher degradation efficiency of OII than bare Fe₃O₄ or Al-Fe-P-B in the degradation experiment. The enhanced catalytic activity of Fe₃O₄/Al-Fe-P-B in heterogeneous Fenton system was due to the synergistic effect between Al-Fe-P-B and Fe₃O₄. The novel catalyst can achieve solid-liquid separation easily by sample magnetic separation and has a good reusability and stability.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript> xerogel support on hydrogen production by steam reforming of LNG over Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript> catalyst

An Al₂O₃-ZrO₂ xerogel (AZ-SG) was prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/AZ-SG catalyst was then prepared by an impregnation method, and was applied to hydrogen production by steam reforming of LNG. A nickel catalyst supported on commercial alumina (A-C) was also prepared (Ni/A-C) for comparison. The hydroxyl-rich surface of the AZ-SG support increased the dispersion of nickel species on the support during the calcination step. The formation of a surface nickel aluminate-like phase in the Ni/AZ-SG catalyst greatly enhanced the reducibility of the Ni/AZ-SG catalyst. The ZrO₂ in the AZ-SG support increased the adsorption of steam onto the support and the subsequent spillover of steam from the support to the active nickel sites in the Ni/AZ-SG catalyst. Both the high surface area and the well-developed mesoporosity of the Ni/AZ-SG catalyst improved the gasification of adsorbed surface hydrocarbons in the reaction. In the steam reforming of LNG, the Ni/AZ-SG catalyst showed a better catalytic performance than the Ni/A-C catalyst. Moreover, the Ni/AZ-SG catalyst showed strong resistance toward catalyst deactivation.     

The difference in hydrogenation performance between Ni-in-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Ni-on-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> for hydrotreating of crude 2-ethylhexanol

Two mesoporous material Ni/γ-Al₂O₃ catalysts were prepared and characterized by ICP-AES, XRD, and TPR. The differences in reaction activity between Ni-in-Al₂O₃ and Ni-on-Al₂O₃ were investigated for hydrotreating of crude 2-ethylhexanol. The results show that the Ni species (Ni-on-Al₂O₃) exhibit excellent hydrogenation activities at a wide range of H₂ pressure and space velocity, while the Ni species (Ni-in-Al₂O₃) exhibit similar activities with those of Ni-on-Al₂O₃ only at higher H₂ pressure and lower space velocity. Due to the presence of extensively exposed Ni species on the Ni-on-Al₂O₃ catalyst, its hydrogenation performance was increased significantly because of the low interphase mass transfer resistance.     

Combustion of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/TiO<Subscript>2</Subscript>/Al thermit mixtures in steel tubes

Explored was the combustion of Fe₂O₃/TiO₂/Al thermit mixtures in steel tubes upon variation in green composition and with special emphasis on the dependence of combustion temperature T _c and burning velocity U on reaction heat Q. Special attention was given to incompleteness of combustion for compositions with low Q.     

Effective Utilization of the Catalytically Active Phase: NH<Subscript>3</Subscript> Oxidation Over Unsupported and Supported Co<Subscript>3</Subscript>O<Subscript>4</Subscript>

Abstract  

The performance of pellets of unsupported and silica-supported Co₃O₄ in the ammonia oxidation was investigated as a function of the particle size to investigate the utilization of the catalytically active phase in these materials. The obtained activity in terms of ammonia conversion over the silica-supported Co₃O₄ is higher compared to the conversion over the unsupported Co₃O₄, despite a lower cobalt oxide loading and more severe diffusional limitations. The effectiveness factor for the silica-supported catalyst is slightly lower than the effectiveness factor for the unsupported catalyst in the form of pellets of similar size. However, the effective utilization of cobalt within the catalyst is higher for the silica-supported catalyst, mainly due to the higher dispersion of the catalytically active phase.     

Selective Synthesis of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanowires Via a Single Precursor: A General Method for Metal Oxide Nanowires

Hematite (α-Fe₂O₃) and magnetite (Fe₃O₄) nanowires with the diameter of about 100 nm and the length of tens of micrometers have been selectively synthesized by a microemulsion-based method in combination of the calcinations under different atmosphere. The effects of the precursors, annealing temperature, and atmosphere on the morphology and the structure of the products have been investigated. Moreover, Co₃O₄ nanowires have been fabricated to confirm the versatility of the method for metal oxide nanowires.     

Oxygen permeability and structural stability of La<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>Co<Subscript>0.2</Subscript>Fe<Subscript>0.8</Subscript>O<Subscript>3−<Emphasis Type="Italic">δ</Emphasis></Subscript> membrane

La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ oxides were synthesized by citrate method and hydrothermal method. The oxides prepared by citrate method are perovskite type structure, while the oxides by hydrothermal method have a small amount of secondary phase in the powder. Pyrex glass seal and Ag melting seal provided reliable gas-tight sealing of disk type dense membrane in the range of operation temperature, but commercial ceramic binder could not be removed from the support tube without damage to the tube or membrane. Though the degree of gas tightness increases in the order of glass>Ag>ceramic binder, in the case of glass seal, the undesired spreading of glass leads to an interfacial reaction between it and the membrane and reduction of effective permeation area. The oxygen flux of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ membrane increases with increasing temperature and decreasing thickness, and the oxygen permeation flux through 1.0 mm membrane exposed to flowing air (P _h =0.21 atm) and helium (P₁=0.037 atm) is ca. 0.33 ml/cm²·min at 950 °C. X-ray diffraction analysis for the membrane after permeation test over 160 h revealed that La₂O₃ and unknown compound were formed on the surface of membrane. The segregation compounds of surface elements formed on both surfaces of membrane irrespective of spreading of glass sealing material. This paper was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.