Silica-Embedded Metal Oxide Nanoparticles as Epoxidation Catalysts: Batch and Continuous Flow Systems

resumo

Catalytic epoxidation of olefins gives epoxide chemicals for several end-user products. With the technological advancements of these processes (especially for light olefins), which have importantly contributed to the epoxides market expansion, challenges remain in developing adequate heterogeneous catalysts for converting bulkier olefins, using simple catalyst synthesis procedures, and, on the other hand, studying the catalytic performances under different operation modes. Hence, heterogeneous epoxidation catalysts are prepared via simple one-pot procedures, with the necessary versatility to tune the material properties for batch and continuous flow operation. Specifically, silica-embedded nanoparticles of molybdenum oxide (Si/Mo(x), x = Mo loading) and silica-embedded nanoparticles of binary transition metal oxides (Si/MoM, M = Ta, Nb or W) are synthesized, and promoted the epoxidation of cis-cyclooctene with tert-butylhydroperoxide as oxidant, at 70 degrees C. Epoxide yields in the range of 90%-100% are reached within 4 h, at 70 degrees C, under batch operation. Under continuous flow, steady state conditions (fixed bed reactor), catalyst Si/MoNb led to ca. 44% epoxide yield, at 70 degrees C. At 90 degrees C, Si/MoNb exhibited multifunctionality leading to 51% cyclooctanone yield. It represents the first fully inorganic heterogeneous Mo-catalyst for continuous flow olefin epoxidation and the first heterogeneous Mo-catalyst for integrated olefins-to-cycloalkanones with hydroperoxides.

palavras-chave

HETEROGENEOUS CATALYST; OLEFIN EPOXIDATION; MESOPOROUS SILICA; MOLYBDENUM; EFFICIENT; OXIDATION; TRANSFORMATION; STABILITY; MECHANISM; COMPLEX

categoria

Chemistry

autores

Gomes, DM; Yao, XY; Neves, P; Antunes, MM; Pinna, N; Russo, PA; Valente, AA

Grupos

G1 - Materiais Porosos e Nanossistemas
G4 - Materiais Renováveis e Economia Circular

Projectos

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

agradecimentos

This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020, & LA/P/0006/2020, and Project FCT- 2023.14213.PEX, financed by national funds through the FCT/MEC (PIDDAC). D.M.G. (grant ref. 2021.04756.BD; https://doi.org/10.54499/2021.04756.BD) acknowledges the FCT for PhD grant (State Budget, European Social Fund (ESF) within the framework of Portugal 2020, namely through the Cen- tro 2020 Regional Operational Program). X.Y. acknowledges the fellowship from the China Scholarship Council (CSC). The position held by M.M.A. was funded by national funds (OE), through FCT, I.P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of article 23 of the Decree- Law 57/2016 of 29 August, changed by Law 57/2017 of 19 July (https://doi.org/10.54499/DL57/2016/CP1482/CT0062). The authors are very grateful to Dr. M. Rosario Soares (CICECO-Aveiro Insti- tute of Materials) for the discussions and kind assistance with the PXRD studies. C. Erdmann is acknowledged for the TEM measurements.