Perovskites derived catalysts

The use of oxide-type perovskites as dry reforming catalysts will be dealt with extensively in Volume II of this book. In this chapter, we report one example of such catalyst in order to highlight the potentiahty of the nanocasting preparation method as a way to control bulk and smface properties of perovskite-derived catalysts. 

This chapter is devoted to the Ha production by steam reforming of bioalcohols and a specific attention will be paid to the interest of using perovskite-derived catalysts for this reaction. 

Perovskites may be used as supports for depositing the metal active phase or as catalyst precursors when the active transition metal is included in the perov-sldte-type structure during the synthesis step. In the later case, a highly dispersed metallic phase is obtained at the oxide surface by segregation induced by a reducing treatment. The both kind of perovskite-derived catalysts were used for ethanol and glycerol steam reforming. 

Villoria JA, Alvarrez-Galvan MC, Al-Zahrani SM. Oxidative reforming of diesel fuel over LaCoOs perovskite derived catalysts influence of perovskite synthesis method on catalyst properties and performance. Appl Catal B Environ. 2011 105 276-88. 

Lanthanum titanium oxynitride is another oxynitride whose performance has recently been improved due to an increased crystallinity of the film and the use of Ir02 co-catalyst [105]. Due to its band gap in the range of 2.05-2.35 eV, the perovskite derived LaTiO cN3, is a potentially attractive water-splitting... 

FIGURE 2.10 Performance of Lao.7Ceo,2Fe03 perovskite-like catalyst at various concentrations of H2S (0-1100 ppm wet basis) in the simulated coal-derived syngas at 600 °C and 1 atm. (Taken... 

Roberts, D.G., and Edwards, JJl. (2011) Kinetics of the water-gas shift reaction over a Lao.yCeoaFeOs perovskite-like catalyst using simulated coal-derived syngas at high temperature. Int J. Hydrogen Energy, 36, 518-527. 

Wu, G., Li, S., Zhang, C, Wang, T., and Gong, J. (2014) Glycerol reforming over perovskite-derived nickel-based catalysts. Appl Catal B 144, 277-285. 

The area of catalysis has recently received renewed attention because of possible applications in solving environmental problems. Precious metals have been found useful for the oxidation of CO to CO2, but are not effective in the eduction of NO. The possibility of using perovskite type catalysts seems promising since it was reported that LaCoOj, LaMnOs and their substituted derivatives have interesting catalytic properties in regard to application in fuel cell electrodes (Meadowcroft, 1970) and in the oxidation reduction reactions involved in the control of automotive exhaust emissions (Libby, 1971 Voor-hoeve et al., 1972, 1973). 

The extensive variety of properties that these compounds show is derived from the fact that around 90% of the metallic natural elements of the periodic table are known to be stable in a perovskite-type oxide structure [74], Besides, the possibility of synthesizing multicomponent perovskites by partial substitution of cations in positions A and B gives rise to substituted compounds with a formula A, A B,. B 03 ft. The resulting materials can be catalysts, insulators, semiconductors, superconductors, or ionic conductors. 

Bonura et alf studied several supported Ni catalysts for methane decomposition and found that both filamentous and encapsulating carbon species were formed under isothermal conditions at 823 K, the latter being responsible for catalyst deactivation. They also confirmed the structure-sensitive character of methane decomposition. The efficient use of these catalysts implies a high dispersion of metal phases which can be achieved by controlled segregation of the active phase. Different Ni mixed oxides such as Ni-Al hydrotalcite, Ni-La perovskites and Ni-Al spinels as catalysts precursors allow a high degree of Ni dispersion, of which that derived from hydrotalcite mixed oxide showed the highest activity for Hg production by methane decomposition. ... 

Perovskite compounds have the general formula ABX3 for the purposes of this study, we are concerned with ATiOa derivatives. Perovskites may be ferroelectric, piezoelectric, etc., and due to their low cost, are currently being re-explored for a variety of purposes, such as in solar cells [124] and catalysts [125,126]. In many cases, the structure—property relationships in the ATi03 compound are unclear. The use of SSNMR for... 

This chapter will be focused on catalysts for ethanol and glycerol steam reforming and more specifically on the use of catalysts derived from perovskite-type precursors. 

The idea to test the substitution of a B cation by copper in a perovskite structure for the methanol synthesis was first developed 30 years ago by Broussard and Wade [6], then by Brown Bourzutschky et al. [7], with the substitution of Mn by copper in a LaMnOs+s perovskite. To date, few other structures have been tested. Besides LaMni CU t03+5 described by different authors [6-9] and used with CO + H2 mixture, the reactivity of LaTii. Cu Os [10,11], YBa2Cu307 t [12,13], and La2Cu04 [14] have been studied. Few works have been performed on noble metals Pt, Rh [7], probably due to the poor methanol selectivity obtained (50-60%). Only recently, studies with CO2 + H2 have been undertaken on LaCro.sCuo.sOs [15], La-M-Cu-ZnO (M=Y, Ce, Mg, or Zr) catalysts derived from perovskites [16], or LaMni. Cu Os [17]. 

Methanol synthesis from CO2 hydrogenation over La-M-Cu-Zn-O (M=Y, Ce, Mg, Zr) catalysts derived from perovskite-type precursors. /. Power Sources, 251,113-121. 

---