Comparison of the performance for oxidation of formaldehyde on nano-Co3O4, 2D-Co3O4, and 3D-Co3O4 catalysts
TL;DR: The 3D-Co 3 O 4 has the best performance of formaldehyde oxidation due to the three-dimensional porous channel structure, larger specific surface area, abundant active surface oxygen species and active Co 3+ cationic species on the exposed (2.2.0) crystal face as discussed by the authors.
Abstract: 2D-Co 3 O 4 and 3D-Co 3 O 4 catalysts were prepared by the hard template method, and nano-Co 3 O 4 was synthesized by precipitation method. The catalytic activity for the oxidation of formaldehyde over various types of catalysts was investigated. The 3D-Co 3 O 4 catalyst attained a 100% conversion rate of formaldehyde at 130 °C with a space velocity of 30,000 mL/(g h), while the 2D-Co 3 O 4 catalyst oxidized formaldehyde completely at 150 °C in the same space velocity conditions. The difference in activity is due to the clear channel structure of the mesoporous Co 3 O 4 prepared by the hard template method, which has large specific surface area and surface active species that allows the reactant to diffuse and undergo surface reactions. The 3D-Co 3 O 4 had the best performance of formaldehyde oxidation due to the three-dimensional porous channel structure, larger specific surface area, abundant active surface oxygen species and active Co 3+ cationic species on the exposed (2 2 0) crystal face. Complete conversion of formaldehyde had remained the same after 3D-Co 3 O 4 was observed for 160 h. Therefore, the 3D-Co 3 O 4 catalyst has the best catalytic activity and stability for formaldehyde, which might be a non-noble catalyst for catalytic removal of formaldehyde in practical application.
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TL;DR: This Review systematically documents the progresses and developments made in the understanding and design of heterogeneous catalysts for VOC oxidation over the past two decades and addresses in detail how catalytic performance is often drastically affected by the pollutant sources and reaction conditions.
Abstract: It is well known that urbanization and industrialization have resulted in the rapidly increasing emissions of volatile organic compounds (VOCs), which are a major contributor to the formation of secondary pollutants (e.g., tropospheric ozone, PAN (peroxyacetyl nitrate), and secondary organic aerosols) and photochemical smog. The emission of these pollutants has led to a large decline in air quality in numerous regions around the world, which has ultimately led to concerns regarding their impact on human health and general well-being. Catalytic oxidation is regarded as one of the most promising strategies for VOC removal from industrial waste streams. This Review systematically documents the progresses and developments made in the understanding and design of heterogeneous catalysts for VOC oxidation over the past two decades. It addresses in detail how catalytic performance is often drastically affected by the pollutant sources and reaction conditions. It also highlights the primary routes for catalyst deactivation and discusses protocols for their subsequent reactivation. Kinetic models and proposed oxidation mechanisms for representative VOCs are also provided. Typical catalytic reactors and oxidizers for industrial VOC destruction are further discussed. We believe that this Review will provide a great foundation and reference point for future design and development in this field.
1,074 citations
TL;DR: In this article, the development of efficient adsorbents and catalysts for VOCs with varied nature are discussed, and the perspectives on the potential future directions of the adsorptive removal and catalytic oxidation of VOC are given.
583 citations
TL;DR: In this article, a review of the development of supported noble metal and metal oxide catalysts for catalytic oxidation of VOCs is presented, and the specific mechanism that leads to superior catalytic activity towards low temperature VOC oxidation was discussed too.
574 citations
TL;DR: In this article, the catalytic performance of MnO2 catalysts with different crystal structures was investigated and it was shown that the tunnel structure and active lattice oxygen species are the main factors that contribute to the excellent performance of δ-MnO2.
431 citations
TL;DR: In this paper, a deNOx catalyst based on hollow porous MnxCo3-xO4 nanocages with a spinel structure thermally derived from nanocube-like metal-organic frameworks (Mn3[Co(CN)6]2·nH2O), which are synthesized via a self-assemble method, is presented.
Abstract: Herein, we have rationally designed and originally developed a high-performance deNOx catalyst based on hollow porous MnxCo3–xO4 nanocages with a spinel structure thermally derived from nanocube-like metal–organic frameworks (Mn3[Co(CN)6]2·nH2O), which are synthesized via a self-assemble method. The as-prepared catalysts have been characterized systematically to elucidate their morphological structure and surface properties. As compared with conventional MnxCo3–xO4 nanoparticles, MnxCo3–xO4 nanocages possess a much better catalytic activity at low-temperature regions, higher N2 selectivity, more extensive operating-temperature window, higher stability, and SO2 tolerance. The feature of hollow and porous structures provides a larger surface area and more active sites to adsorb and activate reaction gases, resulting in the high catalytic activity. Moreover, the uniform distribution and strong interaction of manganese and cobalt oxide species not only enhance the catalytic cycle but also inhibit the formatio...
422 citations
References
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TL;DR: Tricobalt tetraoxide nanorods not only catalyse CO oxidation at temperatures as low as –77 °C but also remain stable in a moist stream of normal feed gas, showing the importance of morphology control in the preparation of base transition-metal oxides as highly efficient oxidation catalysts.
Abstract: [Xie, Xiaowei; Li, Yong; Shen, Wenjie] Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China. [Liu, Zhi-Quan] Chinese Acad Sci, Inst Met Res, Shenyang Natl Lab Mat Sci, Shenyang 110016, Peoples R China. [Haruta, Masatake] Tokyo Metropolitan Univ, Grad Sch Urban Environm Sci, Dept Appl Chem, Tokyo 1920397, Japan. [Haruta, Masatake] Japan Sci & Technol Agcy, CREST, Kawaguchi, Saitama 3320012, Japan.;Shen, WJ (reprint author), Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Catalysis, Dalian 116023, Peoples R China;shen98@dicp.ac.cn
2,239 citations
TL;DR: Adverse health effects from exposure to formaldehyde in prefabricated houses, especially irritation of the eyes and upper airways, were first reported in the mid-1960s and a guideline value of 0.1 ppm was proposed in 1977 by the former German Federal Agency of Health to limit human exposure in dwellings.
Abstract: 1.1. History
Formaldehyde was described in the year 1855 by the Russian scientist Alexander Michailowitsch Butlerow. The technical synthesis by dehydration of methanol was achieved in 1867 by the German chemist August Wilhelm von Hofmann. The versatility that makes it suitable for use in various industrial applications was soon discovered, and the compound was one of the first to be indexed by Chemical Abstracts Service (CAS). In 1944, Walker published the first edition of his classic work Formaldehyde.(1) Between 1900 and 1930, formaldehyde-based resins became important adhesives for wood and wood composites. The first commercial particle board was produced during World War II in Bremen, Germany. Since 1950, particle board has become an attractive alternative to solid wood for the manufacturing of furniture. Particle board and other wood-based panels were subsequently also used for the construction of housing. Adverse health effects from exposure to formaldehyde in prefabricated houses, especially irritation of the eyes and upper airways, were first reported in the mid-1960s. Formaldehyde emissions from particle boards bonded with urea formaldehyde resin were soon identified as the cause of the complaints. As a consequence, a guideline value of 0.1 ppm was proposed in 1977 by the former German Federal Agency of Health to limit human exposure in dwellings. Criteria for the limitation and regulation of formaldehyde emissions from wood-based materials were established in 1981 in Germany and Denmark. The first regulations followed in the United States in 1985 or thereabouts. In Germany and the United States, large-scale test chambers were used for the evaluation of emissions. Although the chamber method is very reliable, it is also time-consuming and expensive. This meant there was a strong demand for simple laboratory test methods.(2)
1,253 citations
TL;DR: In this article, an ultralayered Co3O4 superstructures with high porosity have been synthesized by a facile homogeneous precipitation process under hydrothermal conditions.
Abstract: Ultralayered Co3O4 structures with high porosity have been synthesized by a facile homogeneous precipitation process under hydrothermal conditions. The superstructures consist of well-arranged micrometer length rectangular 2D flakes with high specific surface area, pore volume, and uniform pore size distribution. The electrochemical measurements demonstrate that charge storage occurs in ultralayered Co3O4 due to reversible redox reactions. The charge–discharge study shows that the material is capable of delivering very high specific capacitance of 548 F g–1 at a current density of 8 A g–1 and retains 66% of capacitance at 32 A g–1. The charge–discharge stability measurements show excellent specific capacitance retention capability, ca. 98.5% after 2000 continuous charge–discharge cycles at high current density of 16 A g–1. The exceptional cyclic, structural, and electrochemical stability at higher current rate with ∼100% Coulombic efficiency, and very low ESR value from impedance measurements promise good...
867 citations
TL;DR: The selective synthesis of transition metal oxides with uniform and different reactive crystal planes under nanoscale conditions is expected to bring up new opportunities for design, tuning, and control of chemical activity, specificity, and selectivity.
Abstract: We have succeeded in synthesizing Co(3)O(4) nanosheets, nanobelts, and nanocubes with a hydrothermal process of cobalt hydroxide precursor and subsequent direct thermal decomposition. The predominantly exposed planes are {112}, {011}, and {001}, respectively. The methane combustion catalytic activity order of crystal planes follows {112} > {011} >> {001}. The selective synthesis of transition metal oxides with uniform and different reactive crystal planes under nanoscale conditions is expected to bring up new opportunities for design, tuning, and control of chemical activity, specificity, and selectivity.
849 citations
TL;DR: The excellent catalytic performance of α-MnO(2) nanorods might be associated with the high oxygen adspecies concentration and good low-temperature reducibility and it is sure that one-dimensional well-defined morphological manganese oxides are promising materials for the catalytic elimination of air pollutants.
Abstract: Nanosized rod-like, wire-like, and tubular α-MnO(2) and flower-like spherical Mn(2)O(3) have been prepared via the hydrothermal method and the CCl(4) solution method, respectively. The physicochemical properties of the materials were characterized using numerous analytical techniques. The catalytic activities of the catalysts were evaluated for toluene oxidation. It is shown that α-MnO(2) nanorods, nanowires, and nanotubes with a surface area of 45-83 m(2)/g were tetragonal in crystal structure, whereas flower-like spherical Mn(2)O(3) with a surface area of 162 m(2)/g was of cubic crystal structure. There were the presence of surface Mn ions in multiple oxidation states (e.g., Mn(3+), Mn(4+), or even Mn(2+)) and the formation of surface oxygen vacancies. The oxygen adspecies concentration and low-temperature reducibility decreased in the order of rod-like α-MnO(2) > tube-like α-MnO(2) > flower-like Mn(2)O(3) > wire-like α-MnO(2), in good agreement with the sequence of the catalytic performance of these samples. The best-performing rod-like α-MnO(2) catalyst could effectively catalyze the total oxidation of toluene at lower temperatures (T(50%) = 210 °C and T(90%) = 225 °C at space velocity = 20,000 mL/(g h)). It is concluded that the excellent catalytic performance of α-MnO(2) nanorods might be associated with the high oxygen adspecies concentration and good low-temperature reducibility. We are sure that such one-dimensional well-defined morphological manganese oxides are promising materials for the catalytic elimination of air pollutants.
643 citations