SrSnO₃ perovskite vs. Nd₂Sn₂O₇ pyrochlores for oxidative coupling of methane: deciphering the reactive sites difference

Abstract

Herein, SrSnO₃ perovskite and Nd₂Sn₂O₇ pyrochlore with definite structures have been synthesized using a hydrothermal method, and the differences in their reactive sites for the oxidative coupling of methane (OCM) are investigated. The primary products of perovskite and pyrochlore are C₂ hydrocarbons and CO_x, respectively. The C₂ selectivity of perovskite is primarily affected by basic sites and chemisorbed oxygen species O₂^2-. For pyrochlore, the key factors affecting methane conversion and CO_x selectivity are the acidic sites and reactive oxygen species (chemisorbed oxygen species and weakly bonded lattice oxygen). The chemisorbed oxygen species of pyrochlore are directly generated through intrinsic oxygen vacancies, whereas those of perovskite are generated through oxygen vacancies created under high-temperature lattice distortions. The tightness of the stacking between [SnO₆] octahedra is the main factor affecting the acidic sites and oxygen vacancies of the two composite oxides. The stacking of [SnO₆] octahedra in pyrochlore is loose, resulting in a relatively weak Sn–O bond strength. During the OCM reaction, the Sn–O bond is prone to breakage, resulting in abundant acidic sites and oxygen vacancies. Additionally, the influence of basic sites on the amount of chemisorbed oxygen species is more important than that of oxygen vacancies, which is attributed to the fact that basic sites can stabilize chemisorbed oxygen species on the catalyst surface.

Keywords

Oxidative coupling of methane / definite compounds / perovskite / pyrochlore / comparison of reactive sites

References

[1] Doherty CJ.Circadian surprise - it’s not all about transcription.Science2012;338:338-40

[2] Hammond C,Hermans I.Oxidative methane upgrading.ChemSusChem2012;5:1668-86

[3] Qiu X,Tin K.Review low temperature catalysts for oxidative coupling of methane.J Chem Technol Biotechnol1996;65:303-8

[4] Thybaut J,Mirodatos C.A novel technology for natural gas conversion by means of integrated oxidative coupling and dry reforming of methane.Chem Ing Tech2014;86:1855-70

[5] Aljama H,Abild-pedersen F.Tuning methane activation chemistry on alkaline earth metal oxides by doping.J Phys Chem C2018;122:22544-8

[6] Zhou X,Liu Z.Active oxygen center in oxidative coupling of methane on La₂O₃ catalyst.J Energy Chem2021;60:649-59

[7] Si J,Zhao G.Support oxide tuning of MnO_x-Na₂WO₄ catalysts enables low-temperature light-off of OCM.Fuel2022;311:122539

[8] Hiyoshi N.Oxidative coupling of methane over alkali chloride–Mn–Na₂WO₄/SiO₂ catalysts: promoting effect of molten alkali chloride.Fuel Process Technol2015;133:29-34

[9] Lim S,Jin Suh D,Song KH.Low-temperature oxidative coupling of methane using alkaline earth metal oxide-supported perovskites.Catal Today2020;352:127-33

[10] Roger A,Kiennemann A.Effect of metallo-organic precursors on the synthesis of Sm–Sn pyrochlore catalysts: application to the oxidative coupling of methane.J Catal1997;167:447-59

[11] Murthy PR,Wu G,Shi C.Oxidative coupling of methane: perspective for high-value C₂ chemicals.Crystals2021;11:1011

[12] Mi J,Chen X,Li J.Recent status and developments of vacancies modulation in the ABO₃ perovskites for catalytic applications.Chemistry2023;29:e202202713

[13] Deng J,Xia S.Advances in oxidative coupling of methane.Atmosphere2023;14:1538

[14] Fisher JG,Moon K.High-temperature X-ray diffraction and Raman spectroscopy study of (K_0.5Na_0.5)NbO₃ ceramics sintered in oxidizing and reducing atmospheres.Mater Chem Phys2010;120:263-71

[15] Kapusta B.Molecular dynamics study of the perovskite MgSiO₃ at high temperature: structural, elastic and thermodynamical properties.Phys Earth Planet In1993;75:205-24

[16] Gao L,Liu Z,Zhang J.Structure dependence of dielectric properties in Ca-doped bismuth magnesium niobate pyrochlores.J Alloys Compd2022;922:165859

[17] Muñoz HJ,Gil A.Progress and recent strategies in the synthesis and catalytic applications of perovskites based on lanthanum and aluminum.Materials2022;15:3288 PMCID:PMC9100353

[18] Renju UA,Vaisakhan Thampi DS.Influence of phase transition from order to disorder and Philip’s ionicity on the thermal expansion coefficient of pyrochlore type compositions with a multivalent environment.New J Chem2017;41:245-55

[19] Behara S,Thomas T.Crystal structure classification in ABO₃ perovskites via machine learning.Comput Mater Sci2021;188:110191

[20] Liu H,Dong H.Screening stable and metastable ABO₃ perovskites using machine learning and the materials project.Comput Mater Sci2020;177:109614

[21] Jerez A,García-Martín S,Pico C.Defect pyrochlore structure A₂B₂X₆: a general approach to the coordination polyhedra around the metal ions.J Mater Sci1991;26:5163-6

[22] Jerpoth SS,Aboagye EA.Computer-aided synthesis of cost-effective perovskite crystals: an emerging alternative to silicon solar cells.Clean Technol Envir2020;22:1187-98

[23] Subramanian M,Subba Rao G.Oxide pyrochlores - A review.Prog Solid State Ch1983;15:55-143

[24] Shamblin J,Ewing RC.Structural response of titanate pyrochlores to swift heavy ion irradiation.Acta Mater2016;117:207-15

[25] Petit C,Roger A,Hilaire L.Preparation and characterization of ASnO₃ (A=Ca, Sr or Ba) tin compounds for methane oxidative coupling.Stud Surf Sci Catal1995;91:607-16

[26] Park S,Moon J.Catalytic combustion of methane over rare earth stannate pyrochlore.Catal Lett2003;87:219-23

[27] Yang W,Fu X.Oxidative coupling of methane over Sr−Ti, Sr−Sn perovskites and corresponding layered perovskites.React Kinet Catal Lett1995;54:21-7

[28] Cheng J,Hao Z.Catalytic combustion of methane over cobalt doped lanthanum stannate pyrochlore oxide.Catal Commun2008;9:690-5

[29] Lumpkin GR.Perspectives on pyrochlores, defect fluorites, and related compounds: building blocks for chemical diversity and functionality.Front Chem2021;9:778140 PMCID:PMC8632815

[30] Beyerlein R,Longo J,Jorgensen J.Neutron diffraction investigation of ordered oxygen vacancies in the defect pyrochlores, Pb₂Ru₂O_6.5 and PbT₁Nb₂O_6.5.J Solid State Chem1984;51:253-65

[31] Moncada J,Thakur R,Carrero CA.Developing a Raman spectrokinetic approach to gain insights into the structure–reactivity relationship of supported metal oxide catalysts.ACS Catal2018;8:8976-86

[32] Alammar T,Grasmik V,Mudring AV.Microwave-assisted synthesis of perovskite SrSnO₃ nanocrystals in ionic liquids for photocatalytic applications.Inorg Chem2017;56:6920-32

[33] Rajakumaran R,Chen SM.Facile synthesis of neodymium stannate nanoparticles an effective electrocatalyst for the selective detection of dimetridazole in biological samples.Anal Chim Acta2022;1190:339234

[34] Cortés-adasme E,Conejeros S,Llanos J.Behavior of Eu ions in SrSnO₃: optical properties, XPS experiments and DFT calculations.J Alloys Compd2019;771:162-8

[35] Wu T,Xiong J.Atomically dispersed SrO_x species on exposed {2 2 2} facets of pyrochlore La₂Zr₂O₇ nanocrystals for boosting low-temperature oxidative coupling of methane.Fuel2023;333:126479

[36] Kim I,Na HB,Jung JC.Selective oxygen species for the oxidative coupling of methane.Mol Catal2017;435:13-23

[37] Thum L,Schomäcker R.Oxygen activation in oxidative coupling of methane on calcium oxide.J Phys Chem C2019;123:8018-26

[38] Jiang S,Zhao K.Enhanced chemical looping oxidative coupling of methane by Na-doped LaMnO₃ redox catalysts.Fuel2021;299:120932

[39] Yan L,Gao X.Oxidative coupling of methane over Mo-Sn catalysts.Chem Commun2021;57:13297-300

[40] Zhao M,Wu H,Wan H.Flower-like Sr-La₂O₃ microspheres with hierarchically porous structures for oxidative coupling of methane.Ind Eng Chem Res2019;58:22847-56

[41] Papa F,Osiceanu P,Akane M.Acid–base properties of the active sites responsible for C₂⁺ and CO₂ formation over MO–Sm₂O₃ (M=Zn, Mg, Ca and Sr) mixed oxides in OCM reaction.J Mol Catal A Chem2011;346:46-54

[42] Gambo Y,Triwahyono S.Recent advances and future prospect in catalysts for oxidative coupling of methane to ethylene: a review.J Ind Eng Chem2018;59:218-29

[43] Gu S,Choi J.Effects of metal or metal oxide additives on oxidative coupling of methane using Na₂WO₄/SiO₂ catalysts: reducibility of metal additives to manipulate the catalytic activity.Appl Catal A Gen2018;562:114-9

[44] Yoon S,Choi JW,Song KH.Study on the unsteady state oxidative coupling of methane: effects of oxygen species from O₂, surface lattice oxygen, and CO₂ on the C₂₊ selectivity.RSC Adv2020;10:35889-97 PMCID:PMC9056964

[45] Zanina A,Lund H.The role of adsorbed and lattice oxygen species in product formation in the oxidative coupling of methane over M₂WO₄/SiO₂ (M = Na, K, Rb, Cs).ACS Catal2022;12:15361-72

[46] Tang L,Wong L,Chiang K.The promoting effect of ceria on Li/MgO catalysts for the oxidative coupling of methane.Catal Today2011;178:172-80

[47] Pang Y,Vovk EI.Understanding lanthanum oxide surface structure by DFT simulation of oxygen 1s calibrated binding energy in XPS after in situ treatment.Appl Surf Sci2021;548:149214

[48] Doornkamp C,Ponec V.The isotopic exchange reaction of oxygen on metal oxides.J Catal1999;182:390-9

[49] Martin D.Mobility of surface species on oxides. 1. Isotopic exchange of ¹⁸O₂ with ¹⁶O of SiO₂, Al₂O₃, ZrO₂, MgO, CeO₂, and CeO₂-Al₂O₃. Activation by noble metals. Correlation with oxide basicity.J Phys Chem1996;100:9429-38

[50] Chandra S,George G,Rajkumar PV.Influence of Fe and Fe+F doping on the properties of sprayed SnO₂ thin films.J Mater Sci Mater Electron2016;27:9558-64

[51] Lopes LB,Assaf JM.Effect of Mg substitution on LaTi_1-x Mg_xO_3+δ catalysts for improving the C2 selectivity of the oxidative coupling of methane.Catal Sci Technol2021;11:283-96

[52] Gao W,Wang Q.Controlled synthesis of MgO with diverse basic sites and its CO₂ capture mechanism under different adsorption conditions.Chem Eng J2018;336:710-20

[53] Davydov A,Budneva A.Basic sites on the oxide surfaces: their effect on the catalytic methane coupling.Catal Today1995;24:225-30

[54] Liu C,Li Y.First principle calculation of helium in La₂Zr₂O₇: effects on structural, electronic properties and radiation tolerance.J Nucl Mater2018;500:72-80

[55] Srivastava AM,Beers WW.Luminescence of Mn⁴⁺ in the orthorhombic perovskites, AZrO₃ (A=Ca, Sr).Opt Mater2021;114:110906

[56] Antonio J,Rosas-huerta J.Effects of the phase transition on the structural, mechanical, electronic and vibrational properties of the CaSnO₃ perovskite: study under hydrostatic pressure.J Phys Chem Solids2022;163:110594

[57] Wang H,Bashir K.Isolated Sn on mesoporous silica as a highly stable and selective catalyst for the propane dehydrogenation.Appl Catal A Gen2020;590:117291

[58] Salmones J,Galicia JA.H₂ reduction behaviors and catalytic performance of bimetallic tin-modified platinum catalysts for propane dehydrogenation.J Mol Catal A Chem2002;184:203-13

[59] Petit C,Kaddouri A,Poix P.Oxidative coupling of methane by pyrochlore oxide A₂B₂O₇ (A = rare earth, B = Ti, Zr, Sn). Relation between C₂ selectivity and B-O bond energy.Catal Today1992;13:409-16

[60] Zhang C,Jiang M,Zhang J.A review on identification, quantification, and transformation of active species in SCR by EPR spectroscopy.Environ Sci Pollut Res Int2023;30:28550-62

[61] Shi Y,Chen L.In situ DRIFT study on NH₃ selective catalytic reduction of NO_x over HBEA zeolite doped with CeO₂.Appl Surf Sci2020;506:144715

[62] Choudhary V.Acidity/basicity of rare-earth oxides and their catalytic activity in oxidative coupling of methane to C₂-hydrocarbons.J Catal1991;130:411-22

[63] Scott JF,Kumar A.New phase transitions in perovskite oxides: BiFeO₃, SrSnO₃, and Pb(Fe_2/3W_1/3)_1/2Ti_1/2O₃.J Am Ceram Soc2008;91:1762-8