Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

Abstract

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 − xSrxFeyMn1 − yO3 − δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst with that of an industrial potassium promoted iron (Fe–K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ and the Fe–K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ perovskite oxide.

A green chemistry approach to styrene from ethylbenzene and air on MnxTi1−xO2catalyst

“…Nonetheless, the sustainable activity observed for 45 h demonstrates the importance of thermodynamically stable rutile phase as support with Mn 3 O 4 as the active catalyst. Compared to the systems reported in the literature, [8][9][10][11][12][13][14][15][16][17][18][19][20][21] Mn 3 O 4 supported over rutile TiO 2 is attractive, especially in terms of stability, and yield.…”

“…9 Sekine et al used pervoskite and reactions were conducted at 510 or 540 C at atmospheric pressure in the presence of steam; molar ratio of steam to EB was 2 or 12 with 22% ST yield for 30 min. 10 Venugopal et al has shown ceria containing hydrotalcite at 450 C at atmospheric pressure a marginally decreasing styrene yield from 47 to 45% over a period of 72 h. 11 Shin et al fed a balancing gas of water and EB in helium, over V 2 O 5 /CeO 2 -MgO and achieved EB conversion of 43% and ST selectivity of 91% at 600 C; prior to the activity measurement, the catalyst was activated in the steam ow of 50 mL min À1 by heating up to 650 C at the rate of 2.5 C min À1 . 12 Sivaranjani et al employed V-doped titania with molecular oxygen at 500 C and obtained about 50% ST yield initially; however it continuously decreases at higher time on stream.…”

“…Design of catalysts which are stable, gives high selectivity (>90%) with conversion >50% for EB to ST conversion at lower temperatures around 500 C or lower is one of the challenges in the eld of heterogeneous catalysis. [8][9][10][11][12][13][14][15][16][17][18] Constant efforts have been made to develop catalysts, operating via oxidative dehydrogenation (ODH) mechanism route which is also exothermic in nature 19 to lower operating temperature for EB to ST conversion. 20,21 Manganese is known for its superior catalytic properties for various redox processes in heterogeneous catalysis.…”

Binary Ce–Mn oxides confined in carbon nanotubes as efficient catalysts for ethylbenzene dehydrogenation in the presence of carbon dioxide

“…The relative area of oxygen from H 2 O decrease slightly from 24.9 to 23.8%, indicating that the adsorbed molecular water mostly keep adsorption/desorption equilibrium during the ODH reaction, simultaneously, a little be decomposed at sites of oxygen vacancy to form active oxygen (O*) and active hydrogen (H*). 72,73 It is found that the oxygen from surface hydroxyls decreases distinctly from 15.3 to 11.2%, suggesting that the hydroxyl groups mould supply the activated oxygen or partial OH groups combine with H* to form water. The carbonyl group and carboxyl group may exhibit few contributions to ODH with tender change before and aer reaction according to our previous work.…”

“…51,74 In the presence of lattice oxygen, along with the cyclic redox between the both redox couples of Ce 4+ /Ce 3+ and Mn 4+ /Mn 3+ , and the migration of Mn to the surface of catalyst, the oxygen vacancies, activated oxygen, and activated hydrogen can be generated. According to literatures, 9,72,73,[75][76][77] the following chain of reactions can be occurred:…”