Contents lists available at ScienceDirect Molecular Catalysis journal homepage: www.elsevier.com/locate/mcat Crystalline LaCoO 3 perovskite as a novel catalyst for glycerol transesterifcation Deepshree Phadtare a , Sharda Kondawar b , Anjali Athawale a, ⁎ , Chandrashekhar Rode b, ⁎ a Department of Physical chemistry, Savitribai Phule Pune University, Ganesh Khind Road, Pune, 411007, India b Chemical Engineering and Process Development Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pashan, Pune, 411008, India ARTICLEINFO Keywords: Sol-gel method LaCoO 3 perovskite Glycerol carbonate Glycidol ABSTRACT LaCoO 3 perovskite was synthesized using sol-gel method by nitrate and acetate precursors of La and Co with varying molar ratios of La and Co (1:1, 1:2 and 2:1). This was found to be an unique strategy to obtain highly crystallineLaCoO 3 perovskitematerialwithoutusinganychelatingagent.Thevariationofprecursorswasfound to infuence their crystallinity however, variation in molar ratio in the range of 0.5–2, did not afect the for- mationofperovskiteframework.Theformationofpureperovskitephase(aroundor>80%)couldbeachieved by combination of acetate and nitrate precursors while, the combination of acetate- acetate or nitrate- nitrate precursors resulted in low phase purity for the perovskite due to the formation of secondary phases like La 2 O 3 and Co 3 O 4 . Very interestingly, such combination of perovskite and pure oxide phases contributed to enhance- ment of basic sites which catalyzed the glycerol transestrifaction with DMC (dimethyl carbonate) to GC (gly- cerolcarbonate)andGD(glycidol).Amongallthecatalystsstudied,NAP-2showedhighestefciencyintermsof 98% glycerol conversion and 77% GC and 22% GD selectivities. The highlight of this work is that frst step glycerol transesterifcation with DMC required basic sites of either metal oxide or perovskite but for cascade reaction involving decarboxylation required both metal oxide as well as LaCoO 3 perovskite phase. 1. Introduction Mixed metal oxides particularly, perovskite with a composition of ABO 3 where the A-site ion is usually an alkaline earth or rare earth element and the B site ions could be 3d, 4d or 5d transition metal element (Fig. 1) are commonly employed for various applications due to their unique physical and chemical properties [1]. For example, lanthanum cobaltite has wide spread applications such as black pig- mentationindyesduetostrongabsorptionoverthewholevisiblerange [2]while,LaMO 3 typeperovskitesarealsousefulasgassensors,mainly forsensingoffoulsmellinggaseslikeH 2 S,CH 3 S,(CH 3 ) 2 S and nitrogen containingcompoundsuptoappmlevel.Thisisduetotheirconductive properties as well as their porous nature and electronic transitions oc- curring in their valence states [3]. They are also employed as good interconnectmaterial(electrode)inSolidOxideFuelCells(SOFCs),due totheirimportantcharacteristics viz. electronicconductivity(σ),which is determined by B site ion; and ionic conductivity arising from the presence of oxygen vacancies [4]. It can be applicable as technical ceramic material due to its refractory nature, degree of distortion and mobility of oxygen in lattice structure. Most interestingly, the presence ofvarioustypesofoxygenspecieslike(O 2− ,O 2 -,O-),intheperovskite structure makes them attractive materials as catalysts in oxidation re- actions [5], e. g. strontium doped lanthanum cobaltite catalyzes the oxidation of CO and hydrocarbons (automotive exhaust gases) to CO 2 andreductionofNOtoN 2 [6,7].Alamietal.reportedthattheoxidation reaction over perovskite proceeds via two mechanisms, viz. suprafacial and interfacial in which lattice oxygen and adsorbed oxygen partici- pate, respectively [5]. On the other hand, it can also provide strong basic sites to facilitate the catalytic transesterifcation of glycerol with dimethyl carbonate (DMC) to form glycerol carbonate. Glycerol car- bonate can further undergo decarboxylation to more value added pro- duct, glycidol which requires strong basic sites of metal oxide for the adsorption of librated CO 2 over the surface of the catalyst. This un- dergoesreductiontoCOandactiveoxygenspeciesatoxygenvacancies generated in the perovskite material (Scheme 1)[8]. In the literature, various preparation methods reported for the synthesisofperovskiteoxidesinvolvesolid-statereaction,sol-gel,solid- state thermal decomposition, fame hydrolysis, electrochemical oxida- tion etc [9].Amongthese,sol-gelmethodofersseveraladvantageslike homogeneous mixing of the components at the atomic level; a good stoichiometric control and excellent particle size distribution throughout the bulk material. Typically, sol-gel process for the https://doi.org/10.1016/j.mcat.2019.110496 Received 5 April 2019; Received in revised form 28 June 2019; Accepted 29 June 2019 ⁎ Corresponding authors. E-mail addresses: dranjaliathawale@gmail.com (A. Athawale), cv.rode@ncl.res.in (C. Rode). Molecular Catalysis 475 (2019) 110496 2468-8231/ © 2019 Elsevier B.V. All rights reserved. T