Synthesis, Characterization of Vanadia/titania-based Catalysts and their Performance in Ammonia R... more Synthesis, Characterization of Vanadia/titania-based Catalysts and their Performance in Ammonia Remediation Hao Chen1,3, Raquel Portela4,Wei Han1, Pedro Avila4,Miguel A. Bañares4, King Lun Yeung1,2* 1Department of Chemical and Biomolecular Engineering, 2Division of Environment, 3Nano Science and Technology Program, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China 4 Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049, Madrid Spain *Corresponding author: [email protected] Division: 20 Catalysis and Reaction Engineering Division Subdivision: 20037 Applied Environmental Catalysis Format: Oral Presentation Abstract: Ammonia is an important source of malodors that are becoming more prevalent in urban cities. Indeed, malodor is a rampant environmental pollution problem that is prominent in the places that transport, process and store organic and biological wastes (e.g., drainage and sewers, waste and recycling stations, wast...
ZnO presents favorable thermodynamics, equilibrium constant and stability for H 2 S chemisorption... more ZnO presents favorable thermodynamics, equilibrium constant and stability for H 2 S chemisorption and sepiolite has excellent sorptive and rheological properties to be employed as a support. Four conformed ZnO/sepiolite composites are prepared, two by impregnation in zinc nitrate solutionone using activated carbon as a dispersing and pore generating agentand two by dry mixing of the clay with dispersed or hierarchically assembled ZnO nanoparticles. The extrudates obtained with a mixture of sepiolite and nanodispersed ZnO particles are the most active for H 2 S chemisorption in temperatureprogrammed tests performed in an inert atmosphere, which can be correlated with the higher and homogeneous ZnO dispersion. ZnO sulfidation is reversible in the presence of O 2 . Thus, the activity can be regenerated, and these materials act as catalysts for H 2 S to SO 2 oxidation in air.
The main aspects of preparation technologies for the manufacture of environmental monolithic cata... more The main aspects of preparation technologies for the manufacture of environmental monolithic catalysts have been reviewed on the basis of the patent literature, the authors’ own experience in their laboratories, and the current open literature. The main topics covered in this review are the preparation of massive monoliths by extrusion, the coating of ceramic monoliths, and metallic monoliths. Extrusion, one of the most extensively used processes for the production of ceramic monoliths, should fulfill a number of conditions as adequate plasticity of the pastes to allow their extrusion and their immediate conformation into rigid structures under monolithic shape. This is no trivial matter, since in developing monoliths with new materials a great effort should be devoted to finding appropriate conditions. With respect to coated monoliths, the convenient characteristics of a good monolithic catalyst should be met by managing preparation procedures. Thus, preparation technologies are composed of both materials science and engineering aspects. One emerging technology is the growth of zeolites on monolithic walls. Zeolites are among the most studied materials for environmental applications. Among metallic monoliths, those based on ferritic steel containing alumina are the most important, but those made of aluminum coated by alumina produced by anodisation are excellent materials to prepare metallic monoliths. The melting point of aluminum (660 °C) limits its use to medium–low temperature processes, but the especial characteristics of the anodisation alumina offer exciting prospects.
ABSTRACT This work deals with the analysis of the behaviour of new materials as catalysts for the... more ABSTRACT This work deals with the analysis of the behaviour of new materials as catalysts for the selective reduction of nitrogen oxides in oxidising atmospheres. The catalysts were prepared using as the active phase oxides of copper and nickel, impregnated on different types of support whose principal component was sepiolite, a natural magnesium silicate. The catalysts were produced in the form of monoliths of 8 cells cm−2, to obtain solids with high thermal stability and excellent mechanical properties, with which NO conversions of greater than 75% were obtained when operating at an Area Velocity of 1.6 mh−1, with an O2 concentration of 8% by volume. Significant textural differences have been found between the solids which could affect to a certain extent the activity and selectivity of the catalysts in the studied reaction.
Filing Date: 2003-07-07.-- Priority Data: ES P200201702 (2002-07-19) The invention relates to a m... more Filing Date: 2003-07-07.-- Priority Data: ES P200201702 (2002-07-19) The invention relates to a method for the production of natural or synthetic zeolite monoliths, using other silicates as additives which provide rheological properties that enable extrusion moulding of honeycomb-type structures. The mechanical properties of the monoliths obtained are stabilised by means of hydrothermal treatment with sodium silicate solutions. The product thus obtained is a honeycomb-type monolith which retains the physical and chemical properties of the zeolite contained therein practically unaltered, such that it can be used as a catalyst, absorbent or ionic exchanger in industrial fluid purification processes. Moreover, the monoliths thus obtained overcome the shortcomings of other monoliths stabilised using thermal treatments which can significantly damage the properties of the zeolite, limiting the effectiveness thereof in fluid purification processes.
Wall-flow monolithic filters are commonly made of silicon carbide or cordierite and present high ... more Wall-flow monolithic filters are commonly made of silicon carbide or cordierite and present high poros-ity, but low surface area. Alternatively, wall-flow monoliths with high surface area can be employed as support for active phases that catalyze the elimination of the particles deposited in the pores. In this study, mesoporous monoliths with tailored macroporosity are obtained by extrusion using sepiolite clay and different pore generating agents. Cobalt, barium and potassium were incorporated as active phases during the kneading of the dough or by impregnation of the structured material to give the monoliths the capacity for catalytically burning soot under the conditions of diesel engine exhausts. The incorporated and impregnated catalytic monoliths were morphologically, mechanically and physical-chemically characterized at different preparation stages to study the influence of support porosity and the method of addition of active phases in the catalytic activity for diesel soot ...
A series of V2O5–ZrO2–SO42−–sepiolite mixtures were extruded, calcined and characterised. NH3-SCR... more A series of V2O5–ZrO2–SO42−–sepiolite mixtures were extruded, calcined and characterised. NH3-SCR activity was found to be related to the content of the active VOX–ZrO2–SO42− phase (VSZ). The distribution of sepiolite and VSZ at the surface of the mechanical mixtures was studied by the electrophoretic migration technique. The samples were further characterised by nitrogen adsorption, NH3-TPD, XRD and scanning electron micrography techniques. The electrophoretic migration results showed that the addition of sepiolite to VSZ, by kneading in water, had a dramatic effect on the quantity of VOX–ZrO2–SO42− present at the support's surface, both strongly decreasing the molar fraction of zirconia at the surface, and altering the electrophoretic properties of the mixtures.The SEM micrographs, XRD patterns and activity measurements of the water-kneaded samples supported the electrophoretic migration results. Furthermore, it was verified by electrophoretic migration experiments that up unt...
The influence of fluorine concentration on the synergism between Co/γ-Al2O3 and MoAy-Al2O3 stacke... more The influence of fluorine concentration on the synergism between Co/γ-Al2O3 and MoAy-Al2O3 stacked beds separated by 3-mm of γ-Al2O3Fx (x = 0 - 2.5%), in the hydrodesulphurization of refractory molecules contained in gasoil, under operating conditions similar to those of industry, was studied. The results shown, that the synergism increases with F content, reaching a maximum at 0.8% of fluorine, which it is related to changes in zero point of charge (ZPC) and acid strength, due to the incorporation of fluorine. The conversion of most refractory molecule reported is favoured by fluorine.
ABSTRACT Honeycomb monoliths based on natural heulandite-clinoptilolite were obtained using hydro... more ABSTRACT Honeycomb monoliths based on natural heulandite-clinoptilolite were obtained using hydrothermal treatments instead of ordinary procedure of high temperature ceramization, preserving the physical and chemical properties of the zeolite. The monoliths were used to remove Cr(III) cations from tannery waste waters and to reduce the bacteria contamination of drinking water
The influence of H3P04 on the catalytic activity of a vanadium-tungsten oxide-titania-based catal... more The influence of H3P04 on the catalytic activity of a vanadium-tungsten oxide-titania-based catalyst for the selective catalytic reduction (SCR) of nitrogen oxides with ammonia has been studied in a pseudoadiabatic fixed bed reactor. An activity decrease due to the presence of phosphorus has been observed as well as an increase in the crushing strength of the pellets. A chemical interaction between the active solid, the V,Os-based catalyst, and the extrusion binder, H,PO,, has been demonstrated by X-ray photoelectron spectroscopy and X-ray diffraction. This interaction substantially decreases the concentration of vanadium species at the surface leading to the observed decrease in activity at temperatures between 250 and 300" C. However, at higher temperatures an activity increase takes place as a result of higher process selectivity to the SCR reaction.
Synthesis, Characterization of Vanadia/titania-based Catalysts and their Performance in Ammonia R... more Synthesis, Characterization of Vanadia/titania-based Catalysts and their Performance in Ammonia Remediation Hao Chen1,3, Raquel Portela4,Wei Han1, Pedro Avila4,Miguel A. Bañares4, King Lun Yeung1,2* 1Department of Chemical and Biomolecular Engineering, 2Division of Environment, 3Nano Science and Technology Program, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China 4 Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049, Madrid Spain *Corresponding author: [email protected] Division: 20 Catalysis and Reaction Engineering Division Subdivision: 20037 Applied Environmental Catalysis Format: Oral Presentation Abstract: Ammonia is an important source of malodors that are becoming more prevalent in urban cities. Indeed, malodor is a rampant environmental pollution problem that is prominent in the places that transport, process and store organic and biological wastes (e.g., drainage and sewers, waste and recycling stations, wast...
ZnO presents favorable thermodynamics, equilibrium constant and stability for H 2 S chemisorption... more ZnO presents favorable thermodynamics, equilibrium constant and stability for H 2 S chemisorption and sepiolite has excellent sorptive and rheological properties to be employed as a support. Four conformed ZnO/sepiolite composites are prepared, two by impregnation in zinc nitrate solutionone using activated carbon as a dispersing and pore generating agentand two by dry mixing of the clay with dispersed or hierarchically assembled ZnO nanoparticles. The extrudates obtained with a mixture of sepiolite and nanodispersed ZnO particles are the most active for H 2 S chemisorption in temperatureprogrammed tests performed in an inert atmosphere, which can be correlated with the higher and homogeneous ZnO dispersion. ZnO sulfidation is reversible in the presence of O 2 . Thus, the activity can be regenerated, and these materials act as catalysts for H 2 S to SO 2 oxidation in air.
The main aspects of preparation technologies for the manufacture of environmental monolithic cata... more The main aspects of preparation technologies for the manufacture of environmental monolithic catalysts have been reviewed on the basis of the patent literature, the authors’ own experience in their laboratories, and the current open literature. The main topics covered in this review are the preparation of massive monoliths by extrusion, the coating of ceramic monoliths, and metallic monoliths. Extrusion, one of the most extensively used processes for the production of ceramic monoliths, should fulfill a number of conditions as adequate plasticity of the pastes to allow their extrusion and their immediate conformation into rigid structures under monolithic shape. This is no trivial matter, since in developing monoliths with new materials a great effort should be devoted to finding appropriate conditions. With respect to coated monoliths, the convenient characteristics of a good monolithic catalyst should be met by managing preparation procedures. Thus, preparation technologies are composed of both materials science and engineering aspects. One emerging technology is the growth of zeolites on monolithic walls. Zeolites are among the most studied materials for environmental applications. Among metallic monoliths, those based on ferritic steel containing alumina are the most important, but those made of aluminum coated by alumina produced by anodisation are excellent materials to prepare metallic monoliths. The melting point of aluminum (660 °C) limits its use to medium–low temperature processes, but the especial characteristics of the anodisation alumina offer exciting prospects.
ABSTRACT This work deals with the analysis of the behaviour of new materials as catalysts for the... more ABSTRACT This work deals with the analysis of the behaviour of new materials as catalysts for the selective reduction of nitrogen oxides in oxidising atmospheres. The catalysts were prepared using as the active phase oxides of copper and nickel, impregnated on different types of support whose principal component was sepiolite, a natural magnesium silicate. The catalysts were produced in the form of monoliths of 8 cells cm−2, to obtain solids with high thermal stability and excellent mechanical properties, with which NO conversions of greater than 75% were obtained when operating at an Area Velocity of 1.6 mh−1, with an O2 concentration of 8% by volume. Significant textural differences have been found between the solids which could affect to a certain extent the activity and selectivity of the catalysts in the studied reaction.
Filing Date: 2003-07-07.-- Priority Data: ES P200201702 (2002-07-19) The invention relates to a m... more Filing Date: 2003-07-07.-- Priority Data: ES P200201702 (2002-07-19) The invention relates to a method for the production of natural or synthetic zeolite monoliths, using other silicates as additives which provide rheological properties that enable extrusion moulding of honeycomb-type structures. The mechanical properties of the monoliths obtained are stabilised by means of hydrothermal treatment with sodium silicate solutions. The product thus obtained is a honeycomb-type monolith which retains the physical and chemical properties of the zeolite contained therein practically unaltered, such that it can be used as a catalyst, absorbent or ionic exchanger in industrial fluid purification processes. Moreover, the monoliths thus obtained overcome the shortcomings of other monoliths stabilised using thermal treatments which can significantly damage the properties of the zeolite, limiting the effectiveness thereof in fluid purification processes.
Wall-flow monolithic filters are commonly made of silicon carbide or cordierite and present high ... more Wall-flow monolithic filters are commonly made of silicon carbide or cordierite and present high poros-ity, but low surface area. Alternatively, wall-flow monoliths with high surface area can be employed as support for active phases that catalyze the elimination of the particles deposited in the pores. In this study, mesoporous monoliths with tailored macroporosity are obtained by extrusion using sepiolite clay and different pore generating agents. Cobalt, barium and potassium were incorporated as active phases during the kneading of the dough or by impregnation of the structured material to give the monoliths the capacity for catalytically burning soot under the conditions of diesel engine exhausts. The incorporated and impregnated catalytic monoliths were morphologically, mechanically and physical-chemically characterized at different preparation stages to study the influence of support porosity and the method of addition of active phases in the catalytic activity for diesel soot ...
A series of V2O5–ZrO2–SO42−–sepiolite mixtures were extruded, calcined and characterised. NH3-SCR... more A series of V2O5–ZrO2–SO42−–sepiolite mixtures were extruded, calcined and characterised. NH3-SCR activity was found to be related to the content of the active VOX–ZrO2–SO42− phase (VSZ). The distribution of sepiolite and VSZ at the surface of the mechanical mixtures was studied by the electrophoretic migration technique. The samples were further characterised by nitrogen adsorption, NH3-TPD, XRD and scanning electron micrography techniques. The electrophoretic migration results showed that the addition of sepiolite to VSZ, by kneading in water, had a dramatic effect on the quantity of VOX–ZrO2–SO42− present at the support's surface, both strongly decreasing the molar fraction of zirconia at the surface, and altering the electrophoretic properties of the mixtures.The SEM micrographs, XRD patterns and activity measurements of the water-kneaded samples supported the electrophoretic migration results. Furthermore, it was verified by electrophoretic migration experiments that up unt...
The influence of fluorine concentration on the synergism between Co/γ-Al2O3 and MoAy-Al2O3 stacke... more The influence of fluorine concentration on the synergism between Co/γ-Al2O3 and MoAy-Al2O3 stacked beds separated by 3-mm of γ-Al2O3Fx (x = 0 - 2.5%), in the hydrodesulphurization of refractory molecules contained in gasoil, under operating conditions similar to those of industry, was studied. The results shown, that the synergism increases with F content, reaching a maximum at 0.8% of fluorine, which it is related to changes in zero point of charge (ZPC) and acid strength, due to the incorporation of fluorine. The conversion of most refractory molecule reported is favoured by fluorine.
ABSTRACT Honeycomb monoliths based on natural heulandite-clinoptilolite were obtained using hydro... more ABSTRACT Honeycomb monoliths based on natural heulandite-clinoptilolite were obtained using hydrothermal treatments instead of ordinary procedure of high temperature ceramization, preserving the physical and chemical properties of the zeolite. The monoliths were used to remove Cr(III) cations from tannery waste waters and to reduce the bacteria contamination of drinking water
The influence of H3P04 on the catalytic activity of a vanadium-tungsten oxide-titania-based catal... more The influence of H3P04 on the catalytic activity of a vanadium-tungsten oxide-titania-based catalyst for the selective catalytic reduction (SCR) of nitrogen oxides with ammonia has been studied in a pseudoadiabatic fixed bed reactor. An activity decrease due to the presence of phosphorus has been observed as well as an increase in the crushing strength of the pellets. A chemical interaction between the active solid, the V,Os-based catalyst, and the extrusion binder, H,PO,, has been demonstrated by X-ray photoelectron spectroscopy and X-ray diffraction. This interaction substantially decreases the concentration of vanadium species at the surface leading to the observed decrease in activity at temperatures between 250 and 300" C. However, at higher temperatures an activity increase takes place as a result of higher process selectivity to the SCR reaction.
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