In this work, the redox performance of vanadium-based catalysts was improved by doping copper species, and the phosphorus species was used to combine with CaO to produce Ca(PO3)2, which avoided ...poisoning and deactivation of the catalysts due to the combination of CaO and vanadium species. In addition, the NH3 and NO species could be effectively adsorbed and activated on the surface of the Ca-VWCu3P5Ti catalyst by E-R mechanism. In this way, the harm of CaO to the vanadium-based catalysts was effectively reduced.
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•CaO combined with the active sites of the catalyst, resulting in the catalyst poisoning in cement kilns.•Redox property and surface acidity of catalysts were protected by Cu and P doping from CaO.•The phosphorus was used to combine with CaO to form Ca(PO3)2, thus protecting the active sites of vanadium-based catalysts.•After doping with Cu and P, the SCR reaction pathway of the catalyst followed the E-R mechanism.
CaO was the inevitable cause of V2O5-WO3-TiO2 catalyst (VWTi) poisoning in cement kilns. The significant reduction in NO conversion was due to the combination of CaO and active species of the vanadium-based catalyst. In this work, the VWTi catalysts were modified with different contents of Cu and P to improve resistance to CaO, thereby extending the service life of catalysts in cement kilns. By doping Cu and P, the Ca-VWCu3P5Ti had better catalytic activity, reduced the poisoning effect of CaO to V5+, thus protecting the redox properties and increasing the surface acidic sites of the catalyst. Meanwhile, the in-situ DRIFTs results showed that the poisoning effect of CaO was weaker on the Ca-VWCu3P5Ti than that of the Ca-VWTi. In addition, the NH3 and NO species could be effectively adsorbed and activated on the surface of the Ca-VWCu3P5Ti by E-R mechanism. In this way, the harm of CaO to the vanadium-based catalysts was effectively reduced. This work provided a promising strategy to design vanadium-based catalysts with superior resistance to CaO in NH3-SCR reaction.
In this study, a novel in situ confined encapsulation strategy for construction of Co3O4@SiO2 catalyst by the vacuum self-assembly method was developed. The ordered mesoporous silica with different ...pore diameters was treated as templates to prepare order mesoporous Co-MOFs@SiO2, and the Co-MOF were anchored and embedded in ordered mesoporous channels of mesoporous SiO2 by the vacuum in-situ self-assembly process. After calcination, two types order mesoporous Co3O4@SiO2 catalysts with different pore diameters (OM-Co3O4@KIT-6 and OM-Co3O4@SBA-15) were obtained for catalytic combustion of toluene. It is discovered that the highly dispersed Co3O4 nanoparticles were limited in the pores of ordered mesoporous silica. The test results for the toluene oxidation reaction confirmed that OM-Co3O4@SBA-15 with 16 nm pore diameter has excellent toluene catalytic oxidation activity and good thermal stability, which are mainly attributed to the content and dispersion of Co3+ species, the effective anchoring of Co-MOF in the pores, more adsorbed oxygen species and strong acid sites.
In this study, ordered mesoporous silica with different pore diameters was used as a template, and Co-MOF was successfully fixed and embedded in the ordered mesoporous channel of SiO2 through vacuum in-situ self-assembly. It is found that the highly dispersed Co3O4 nanoparticles are effectively confined in the pores of ordered mesoporous silica. The test results for the toluene oxidation reaction show that OM-Co3O4@SBA-15 with a pore size of 16 nm has excellent toluene catalytic oxidation activity and good thermal stability. Display omitted
•A novel in situ confined encapsulation strategy for construction of Co3O4@SiO2 catalyst was developed.•Co-MOF is embedded in the ordered mesoporous channel of SiO2 by the vacuum self-assembly method.•The highly dispersed Co3O4 nanoparticles are confined to the ordered mesoporous wall of silica.•OM-Co3O4@SBA-15 exhibits an excellent activity due to the effective anchoring of Co3O4 in the pores.
In this paper, CeO2-WO3-TiO2 catalysts with TiO2 (001) facets were directly synthesized by EISA method and used for selective catalytic reduction of NO with NH3. The percentage of TiO2 (001) facets ...on CeO2-WO3-TiO2 catalysts was modified by the P123:Ti ratio. The catalytic activity and the percentage of TiO2 (001) facets presented linear relationship. The surface atomic ratio of Oβ/(Oα + Oβ) also was related with low-coordinated atoms on the TiO2 (001) facets. Besides, CeO2-WO3-TiO2 catalysts showed excellent resistance of H2O and SO2.
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•Design and control of TiO2 (001) facets were carried out through EISA method.•Percentage of TiO2 (001) facets played an indispensable role in SCR reaction.•Catalysts showed satisfactory water-resistance and certain SO2 tolerance.•The pumped of H2O and SO2 influenced low-coordinated atoms on TiO2 (001) facets.
CeO2-WO3-TiO2 catalysts were directly synthesized by evaporation-induced self-assembly (EISA) method and used for selective catalytic reduction of NO with NH3. The percentage of enriched TiO2 (001) facets on CeO2-WO3-TiO2 catalysts were modified by the P123:Ti ratio. While the P123:Ti ratio was 0.02, the percentage of enriched TiO2 (001) facets were the maximum on CeO2-WO3-TiO2 catalysts. At this condition, the catalytic activity and the percentage of TiO2 (001) facets presented linear relationship. With the increase of the percentage of TiO2 (001) facets, catalytic activity of catalysts presented a rising trend. Thus CeO2-WO3-TiO2-0.02 catalyst showed the best catalytic activity for selective catalytic reduction of NO with NH3. Besides, the modulation of P123:Ti ratio could also influence the reducing capacity and acid sites for catalysts, which would promote catalytic activity of catalysts. Based on those influence factors, CeO2-WO3-TiO2-0.02 catalyst showed the best catalytic activity. Simultaneously, CeO2-WO3-TiO2-0.02 catalyst showed excellent resistance of H2O and SO2. Various characterization results indicated that the surface atomic ratio of Oβ/(Oα + Oβ) had a certain decrease for poisoned catalyst, which would result in the decrease of low-coordinated atoms on TiO2 (001) facets. At the same time, when pumped of H2O and SO2, the ammonium sulfate salt deposition and competitive adsorption of SO2 and NO would occur so that result in the decrease of catalytic activity.
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•Ordered mesoporous CoFeOx@TiZrOx is prepared by calcining CoFe-ZIF67@TiZrOx.•CoFeOx are highly dispersed in ordered mesoporous due to the TiZrOx encapsulation.•Doping Fe in Co3O4 can ...improve the CoFeOx@TiZrOx redox property and acid site.
Anchoring MOFs in ordered mesoporous channels is a novel scheme to improve the stability and dispersion of metal oxide nanoparticles. In this paper, highly dispersed CoFeOx nanoparticles in ordered mesoporous TiZrOx channels were prepared by in situ self-assembly confinement method and applied to the catalytic combustion of o-dichlorobenzene (o-DCB). By analyzing the BET, SEM, TEM, XRD, and FTIR results, we found that the CoFeOx nanoparticles of CoFeOx@TiZrOx catalyst prepared by vacuum in situ self-assembly method were smaller and distributed in ordered mesoporous channels due to the confinement effect of TiZrOx compared with CoFeOx@TiZrOx-c catalyst. In addition, doping Fe in Co3O4 could improve the redox property, O mobility and acid site of the CoFeOx@TiZrOx catalyst, to improve the activity and stability of the catalyst. In short, the CoFeOx@TiZrOx catalyst not only had excellent catalytic performance for o-DCB destruction (T90 = 381 °C), but also had outstanding stability to resistant Cl poisoning deactivation, which mainly attributed to abundant Co3+, Fe2+, lattice oxygen species, and strong acid sites. The MvK reaction mechanism of the CoFeOx@TiZrOx catalyst based on surface lattice oxygen was proposed by characterization analysis.
In this paper, the morphology of 3D TiO2 support was regulated by modulating the hydrothermal time, and CeO2-WO3/TiO2 catalysts catalyst was synthesized by impregnation method and used for selective ...catalytic reduction of NOx with NH3. The whole formation process of flower-like TiO2 might be influenced by the changed of the hydrothermal time and also be made.
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•Flower-like TiO2 support was regulated by modulating hydrothermal time.•Flower-like structure influenced the surface atomic ration of Ce3+/(Ce3+ + Ce4+).•The surface atomic ration of Ce3+/(Ce3+ + Ce4+) influenced the SCR performance.•The catalysts showed satisfactory water-resistance and certain SO2 tolerance.
Morphology of 3D TiO2 support was regulated by modulating the hydrothermal time. Notably, the increase of hydrothermal time could greatly promote the transformation of rod-like TiO2 to flower-like TiO2, while the continuous increase of hydrothermal time damaged the integrity of flower-like TiO2 and led to the appearance of large TiO2 particles. After that, a series of CeO2-WO3/TiO2 catalysts were prepared by a typical impregnation method. The catalytic performance of these CeO2-WO3/TiO2 catalysts for the selective catalytic reduction of nitrogen oxides (NH3-SCR) verified that NOx conversion was greatly related to morphological integrity of flower-like TiO2. Prominently, activity of CeO2-WO3/TiO2-8 catalyst was still excellent after introducing H2O and SO2, and thus the combined CeO2-WO3/TiO2-8 catalyst showed high catalytic activity and good resistance to H2O and SO2. Various characterizations indicated that the integrity of flower-like structure could evidently alter the surface atomic ratio of Ce3+/(Ce3+ + Ce4+) as well as acid sites. With the increase of surface atomic ratio of Ce3+/(Ce3+ + Ce4+), the SCR performance of the catalysts was obviously improved. In short, the superior catalytic performance of CeO2-WO3/TiO2 for the SCR of NOx was related to the morphology of TiO2 support, the highly dispersed active species, the valence of Ce, acid sites and lots of surface adsorbed oxygen.
Ordered mesoporous TiO2–ZrO2 materials were prepared by evaporation-induced self-assembly (EISA). The CeSn/TizZr10-zOx catalysts were prepared by impregnation method, and its catalytic performance ...was evaluated for the removal of 1,2-dichlorobenzene (o-DCB). The structure and properties of CeSn/TizZr10-zOx were characterized by N2 adsorption-desorption, XRD, Raman, SEM, TEM, XPS and temperature programmed techniques. The results showed that Ce and Sn oxides were highly dispersed on TiO2–ZrO2 surface. Ti–Zr mixed oxides not only contributed to the formation of ordered mesopores, but also to the formation of strong acid sites. When the molar ratio of Ti/Zr was 6:4, the catalyst exhibited the excellent catalytic activity and outstanding stability and repeatability for the o-DCB elimination reaction because of its superior chlorine resistance. Furthermore, the reaction mechanism of o-DCB catalytic oxidation reduction was proposed based on surface lattice oxygen.
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•Ordered mesoporous TiO2–ZrO2 materials are synthesized by EISA method.•Ordered mesopores and strong acid sites are formed by Ti–Zr mixed oxides.•Surface lattice oxygen plays a significant role in catalytic elimination of o-DCB.•Zr has preferable chlorine-resistant ability in catalytic elimination reaction o-DCB.
A series of hollow In2O3 @ Pd-Co3O4 core/shell catalyst with an ultra-thin shell (20–30 nm) were prepared by coaxial electrospinning method. It is applied for the low-temperature CO oxidation ...reaction and showed excellent catalytic performance.
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•Hollow In2O3 @ Pd-Co3O4 with ultra-thin shell (20–30 nm) was synthesized.•The In2O3 @ Pd-Co3O4 owned higher dispersion and smaller size of Pd.•The In2O3 @ Pd-Co3O4 owned superior CO activity and stability.
In this paper, a series of hollow In2O3 @ Pd-Co3O4 core/shell nanofibers with ultra-thin shell about 20–30 nm have been successfully fabricated by coaxial electrospinning, which used in CO oxidation. Desirably, the In2O3 @ Pd-Co3O4 exhibited the higher CO activity with T90 = 56 °C and lower activation energy. Through some characterizations, it is verified that ultra-thin shell structures, stronger redox ability, structure defects, higher proportion of Pd2+ species and smaller proportion of Co3+ species and higher chemical adsorbed oxygen species of In2O3 @ Pd-Co3O4 were preponderant to the increase of CO activity. Therefore, the In2O3 @ Pd-Co3O4 catalyst could be considered a prospective candidate for the CO oxidation.
A series of CeO2-WO3-Pal/TiO2 catalysts were prepared by doping with different contents of palygorskite (Pal). More importantly, the CeO2-WO3–20%Pal/TiO2 catalyst prepared by impregnation method ...showed excellent performance for selective catalytic reduction (SCR) NOx with NH3. In more detail, the NO conversion could reach to 82% at 240 °C and keep above 92% in the range of 280–400 °C. According to the NH3-TPD tests, the surface acidity of the CeO2-WO3–20%Pal/TiO2 catalyst was increased obviously, which is beneficial to the NH3 adsorption in the SCR reaction. Besides, through XRD, XPS, Raman spectra and TEM characterizations, it suggested that the active species cerium and tungsten were uniformly dispersed on the surface of Pal, and it is very important for the improvement of SCR performance. In a word, the optimum Pal proportion was helpful to improve the catalyst catalytic performance, so it was more widely used in the SCR process.
A series of CeO2-WO3-Pal/TiO2 catalysts were prepared by impregnation method for NH3-SCR reaction. Active species cerium and tungsten were adsorbed on the Pal surface, and it had higher dispersion performance, so that promoted the adsorption and activation of reactants. Therefore, CeO2-WO3–20%Pal/TiO2 catalysts showed excellent SCR performance Display omitted
•The CeO2-WO3- TiO2 catalyst doped Pal was beneficial to the improvement of SCR activity.•The active species were better dispersed on the surface of the Pal.•The CeO2-WO3–20%Pal/TiO2 catalysts showed excellent SCR performance in the range of 280–400 °C.•Chemisorption oxygen had better fluidity within the CeO2-WO3–20%Pal/TiO2 catalyst.
The shortcomings of Co-based powder catalysts such as amorphous susceptibility to loss and high influence by pressure drop have become the key factors affecting their catalytic activity. In this ...paper, two methods were proposed to prepare novel monolithic Co3O4/SiO2 catalysts by 3D direct ink writing (DIW) technology: (1) one-step method of printing the active component with supports, (2) two-step method of printing the support first, and then loading the active components. The results showed that the monolithic catalyst prepared by the two-step method possessed more abundant Co3+ and lattice oxygen (Olatt) species than the one-step method, which jointly promoted the catalytic conversion of toluene. However, the catalyst printed by the one-step method had a stronger interaction between the active component and the support, showing better thermal stability and water resistance. In addition, the SiO2 support (the calcined product after SiO2 ink printing) enhances the activity, stability, compression resistance, while the N–SiO2 support (the calcined product after SiO2 precursor ink printing) can effectively prevent blockage of the pore structure by the binder and increase physical properties such as pore volume and specific surface area of Co3O4/SiO2 catalyst.
The monolithic Co3O4/SiO2 catalysts with ordered macropore-mesoporous structure were successfully constructed by 3D printing technology. We observed that this monolithic catalyst structure exhibited superior catalytic activity, excellent thermal stability, and water resistance. The catalytic combustion of toluene was achieved through the synergistic promotion of Co3+ species and lattice oxygen (Olatt). Display omitted
•The monothilic OM-Co3O4/SiO2 catalysts was constructed by 3D printing.•The Co3O4/SiO2-WI catalyst had excellent activity for the elimination of toluene.•The 3D-Co3O4/SiO2 catalyst exhibited superior thermal stability and water resistance.
