La-Doped Alumina, Lanthanum Aluminate, Lanthanum Hexaaluminate, and Related Compounds: A Review Covering Synthesis, Structure, and Practical Importance

Abstract

Advanced materials based on lanthanum–aluminum oxides are useful for many practical applications, not the least in catalysis, energy conversion and energy storage systems designed for a sustainable world economy. The three main La–Al–O (LAO) combinations of commercial interest are La-doped aluminas (LDA), lanthanum monoaluminate (LMA, a perovskite), and lanthanum hexaaluminate (LHA). Usually, the literature treats doped aluminas, perovskites, and hexaaluminates separately. The current review tries to identify common trends and features with respect to structure, synthesis, and applications of LAOs, which should lead to a more holistic understanding of their chemistry. This, in turn, should trigger innovative ideas with respect to new or improved applications. Apart from a variety of uses at low temperatures, the main advantages of LDA, LMA, LHA, and related compounds are their high-temperature stability and the extended applicability that comes with it.

Enhancing the Catalytic Performance of Platinum-Doped Lanthanum Hexaaluminate through Reduction Method Variation

“…The synthesis of LHA from a pellet by the wet impregnation method is simpler than the so-gel and coprecipitation methods [11]. Hence, the wet impregnation method was employed to develop LHA support.…”

“…The wet-impregnation method [11,21] was used to prepare a Pt-LHA catalyst (Figure 1). First, a 1/8 Al 2 O 3 pellet was crushed by using a blender to get different mesh sizes such as 12-14, 14-16, 16-20, 20-25, and 25-30, and it was separated by using the sieving method.…”

“…supports have been studied for high-temperature combustion reactions. Particularly, hexaaluminates have widely been used for high-temperature reaction conditions because their unique crystal structure grants them high thermal stability, with stable phase composition maintained even at temperatures up to 1600 • C [11]. Moreover, the impregnation method easily allows for the incorporation of Platinum or other active metals on the hexa-aluminate surface.…”

Research progress on the catalytic and thermal decomposition of ammonium dinitramide (ADN)

“…It was reported that they could maintain a high specic surface area of 20 m 2 g −1 even aer exposure at 1200 °C for 4 h. 123 As a result, these hexaaluminates are usually employed as carriers for active metals in catalyzing the decomposition and combustion of ADN. [124][125][126][127] Jo et al 128 loaded Pt on Sr 0.8 La 0.2 -MnAl 11 O 19 by the immersion method followed by calcination at 550 °C and 1200 °C to obtain Pt/hexaaluminate catalysts, respectively. According to the experimental results, the catalysts exhibited similar catalytic activity, and both could reduce the onset decomposition temperature of ADN-based monopropellant by 65 °C in a batch reactor.…”

Autothermal Oxidative Coupling of Methane over Pt/Al2O3 Catalysts Doped with Rare Earth Oxides

“…La 2 O 3 is known to stabilize Al 2 O 3 by either inhibiting a phase transition or by forming mixed oxides [44][45][46]. The high-temperature stability of 20La is most likely related to the ability to delay phase changes of metal oxide supports at high temperatures, which makes La a frequently used dopant for Al 2 O 3 [47][48][49]. This leads to a more stable catalytic system exhibiting a steadier performance without significant drops in activity and selectivity.…”