Tailoring the properties of BaTi0.8Cu0.2O3 catalyst selecting the synthesis method

Abstract

Highlights-BaTiO3 and BaTi0.8Cu0.2O3 perovskites were synthesized using sol-gel and hydrothermal methods.-The location of copper in the catalyst depends on the synthesis method.-Cu-BTOsg, with Cu incorporated into the structure, presents a high NOx storage capacity.-Cu-BBOH, with CuO highly dispersed on the surface, shows a high activity for NO to NO2 oxidation. This is a previous version of the article published in Applied Catalysis A: General. 2016General. , 519: 7-15. doi:10.1016General. /j.apcata.2016 2 AbstractThe effect of the synthesis method (hydrothermal and sol-gel) on the properties of BaTi0.8Cu0.2O3 perovskites as catalysts for NOx and soot removal has been analyzed. X-ray powder diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), ICP-AES, N2 adsorption at -196ºC, Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and temperature programmed reduction with hydrogen (H2-TPR) have been used for catalysts characterization.To test their catalytic activity, NOx storage and soot combustion temperature programmed reaction tests have been carried out.The results allow to conclude that the synthesis method determines the position of copper on the perovskite structure and, therefore, the catalytic applications. When the hydrothermal method is used the copper is highly dispersed on the perovskite surface, obtaining a catalyst with a high activity for the NO to NO2 oxidation reaction, which can be used as oxidation catalyst for soot removal. Nevertheless, using the sol-gel method, copper is incorporated into the perovskite structure and, consequently, the catalyst presents a high NOx storage capacity

BaTi0.8B0.2O3 (B = Mn, Fe, Co, Cu) LNT Catalysts: Effect of Partial Ti Substitution on NOx Storage Capacity

“…In previous studies [11,12], titanium was partially substituted by copper in the BaTiO 3 perovskite structure, showing the resulting BaTi 1−x Cu x O 3 perovskites a high activity for NOx storage, which was attributed to the presence of oxygen vacancies (created on the catalyst surface as a consequence of the copper incorporation into the structure) and to the segregation of some phases (mainly BaCO 3 and Ba 2 TiO 4 , but also CuO). It was also concluded that the BaTi 0.8 Cu 0.2 O 3 catalyst presents a NOx storage capacity (NSC) at 420 • C in the range of levels reported for noble metal-based catalysts (around 300 µmol/g) [13], and hence could be proposed as a potential component of high-temperature LNT systems for lean burn engines, such as gasoline direct injection engines.…”

“…In fact, an interesting challenge has been highlighted in a recent EU report, regarding the need to develop alternatives to the use of critical raw materials such as precious metals [9]. In this line, the potential of perovskite base catalysts is being largely illustrated in the literature for environmental applications [10][11][12].…”

“…Thus, the aim of this paper is to determine the effect of Ti partial substitution by Mn, Fe, and Co in the NSC of the BaTi 0.8 B 0.2 O 3 LNT catalyst. The results will be analyzed with respect to the performance of the previously studied BaTi 0.8 Cu 0.2 O 3 catalyst [11,12]. Table 1 presents the nomenclature and the basic characterization data of the catalysts: B metal content (measured by ICP-OES), BET surface area (obtained by applying the BET equation to N 2 adsorption data) and XPS.…”

“…Concerning the XRD results, Figure 1a shows the XRD patterns of the catalysts that reveal a perovskite like structure (the diffraction peaks observed at 2θ: 22 ; for (100), (110), (111), (200), (210), (211), (220), and (310) lattice planes, correspond to the standard JCPDS for tetragonal perovskite structure: 5-626 [17]) as the major crystalline phase for all the catalysts. Based on the splitting of peak around 51 • , it seems that the perovskite structure is tetragonal for BTO_ref and BTCuO_2, but it changes to cubic for the other catalysts [11,12]. The magnification of the main peak of the diffractograms (31.5 • ), included in Figure 1b, clearly shows a shift to a lower angle value, respect to the BTO reference which is more evident for BTMnO_2, BTCoO_2, and BTFeO_2 (suggesting a modification of the perovskite structure) [11,12] than for BTCuO_2 (as the tetragonal structure is preserved for this catalyst), even though a decrease in the peak intensity is featured.…”

“…Based on the splitting of peak around 51 • , it seems that the perovskite structure is tetragonal for BTO_ref and BTCuO_2, but it changes to cubic for the other catalysts [11,12]. The magnification of the main peak of the diffractograms (31.5 • ), included in Figure 1b, clearly shows a shift to a lower angle value, respect to the BTO reference which is more evident for BTMnO_2, BTCoO_2, and BTFeO_2 (suggesting a modification of the perovskite structure) [11,12] than for BTCuO_2 (as the tetragonal structure is preserved for this catalyst), even though a decrease in the peak intensity is featured. Additionally, other minority phases are also identified by XRD, that is, mainly Ba 2 TiO 4 and BaCO 3 (formed by the carbonation of segregated barium oxide during samples atmospheric exposure) but also CuO for BTCuO_2, and only BaCO 3 for BTMnO_2, BTFeO_2, and BTCoO_2 catalysts.…”