Ex-situ catalytic microwave pyrolysis of alkali lignin facilitates the production of monophenols and monoaromatics under the application of LaFe1-xCuxO3 perovskites

Abstract

Two perovskites, LaFe1-xCuxO3 (x = 0, 0.20), were synthesized by co-precipitation approach, are applied for the ex-situ catalytic pyrolysis of alkali lignin (AL) under microwave-assisted. The results showed that the as-constructed LaFe1-xCuxO3 perovskites exhibited excellent activity towards the production of monophenols and monoaromatics compared with non-catalysis. Especially, after Cu doping exerted stronger deoxygenation effect in comparison to LaFeO3, which was more conducive to forming monocyclic aromatic hydrocarbons (MAHs) with a selectivity of 21.11 %. Interestingly, although the oxygen vacancy concentration in LaCu0.2Fe0.8O3 was higher than that in LaFeO3, the activity of the former towards monophenols (78.72 % selectivity) was basically the same as the latter (79.08 % selectivity), which was associated with their approximately equal surface area, manifesting that the surface area of LaFe1-xCuxO3 perovskites played a more dominant role in ex-situ catalytic pyrolysis of AL relative to oxygen vacancy. Furthermore, air-TG results declared the LaFe1-xCuxO3 catalysts possessed good anti-coking performance (coke amount ∼ 5 %). Notably, the presence of oxygen vacancy (Fe3+-□-Fe2+) in LaFeO3 while Cu doping resulted in forming Cu2+-□-Cu+, which were responsible for combining with oxygenated volatiles to yield the active sites FeOx and CuOx respectively, dominating the ex-situ catalytic pyrolysis of AL.