Immobilization of gold nanoparticles on fused silica capillary surface for the development of catalytic microreactors

A new reaction setup using a gold-based catalytic microcapillary reactor was developed. In order to immobilize the gold nanoparticles onto the fused silica inner wall, two different linkers were used: (3-aminopropyl)triethoxysilane (APTES) and (3-mercaptopropyl)triethoxysilane (MPTES). Three different types of gold nanoparticles: (i) Turkevich gold nanoparticles (Citrate–Au), (ii) polyvinylpyrrolidone stabilized gold nanoparticles (PVP–Au) and (iii) polyvinylalcohol stabilized gold nanoparticles (PVA–Au) were synthesized to be anchored on the microcapillary internal surface. The catalytic efficiency of these new microsystems has been investigated for oxidation as a function of the nature of the linkers and/or the type of gold nanoparticles. The oxidation of benzyl alcohol in the presence of H2O2 was used to evaluate the catalytic performance of these microreactors. Under the reaction conditions (80 °C, resident time = 639 s), the Citrate–Au nanoparticles leaked out slightly from the capillary reactor, whereas high conversions (>90%) and high selectivity to benzoic acid were achieved with PVP–Au and PVA–Au nanoparticles. A catalytic microreactor based on MPTES/PVP–Au functionalization proved to be the most effective for this reaction.

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► A new reaction setup using a gold-based catalytic microcapillary reactor was developed.
► Three different gold nanoparticle solutions were immobilized.
► In total five new catalytic microcapillary reactors were prepared and evaluated.
► Catalytic performances were compared upon benzyl alcohol oxidation.
► MPTES/PVP–Au functionalization proved to be the most effective.