Selectivity engineering in catalysis by ruthenium nanoparticles supported on heteropolyacid-encapsulated MOF-5: one-pot
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ORIGINAL ARTICLE
Selectivity engineering in catalysis by ruthenium nanoparticles supported on heteropolyacid-encapsulated MOF-5: one-pot synthesis of allyl 4-cyclohexanebutyrate and kinetic modeling Dipti P. Wagh 1
&
Ganapati D. Yadav 1
Received: 20 September 2020 / Accepted: 4 November 2020 # Qatar University and Springer Nature Switzerland AG 2020
Abstract Functionalized metal-organic framework containing a heteropolyacid such as dodecatungstophosphoric (DTP)-encapsulated MOF5 was synthesized by an in situ method and then ruthenium was incorporated by incipient wetness impregnation. A multifunctional heterogeneous catalyst, 1% Ru-15%DTP@MOF-5 with active acid and the metal sites make it the most efficient catalyst. For acid sites, dodecatungstophosphoric acid (DTP) was encapsulated into MOF-5 and ruthenium was loaded as metal sites. Its activity was examined in the one-pot synthesis of allyl 4-cyclohexanebutyrate, a flavoring agent, by esterification of 4-phenylbutyric acid with allyl alcohol followed by aromatic ring hydrogenation using molecular hydrogen. Esterification of 4-phenylbutyric acid with allyl alcohol gives allyl 4-phenylbutyrate which is further hydrogenated to give allyl 4-cyclohexanebutyrate. The octahedral cubic morphology of MOF-5 was retained even after DTP encapsulation and loading of ruthenium. Catalyst screening for esterification step was carried out by varying loadings of DTP (10, 15, and 20%) on MOF-5. Among these, 15% DTP-loaded MOF-5 showed the best catalytic activity. For selective aromatic ring hydrogenation, different metals such as Pd, Re, Ru, and Rh were examined and it was found that the Ru-based catalyst resulted in the highest conversion of allyl 4-phenylbutyrate (89.63%) and selectivity for allyl 4cyclohexanebutyrate (96.52%). 1% Ru-15% DTP@MOF-5 catalyst was thermally stable and five times reusable. For both the steps, the kinetics was studied using the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism and the apparent activation energy for esterification was calculated as 13.34 kcal/mol and that for hydrogenation as 14.87 kcal/mol. Keywords One-pot synthesis . Esterification . Aromatic ring hydrogenation . Green chemistry . Metal-organic framework (MOF) . Ruthenium nanoparticles . Heteroployacid . Kinetics
1 Introduction Metal-organic frameworks (MOFs) have numerous applications in many fields such as electrochemical energy storage, sensing, gas storage and separation, catalysis, drug delivery and liquid separation, and purification due to their cage-like structure. MOFs are crystalline porous organic-inorganic hybrid materials with a large surface area due to the hollow structure [1–4]. Also, hybrid nanocomposites prepared from * Ganapati D. Yadav [email protected]; [email protected] Dipti P. Wagh [email protected] 1
Department of Chemical Engineering, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga, Mumbai 400 019, India
a Cu-based MOF (MOF-199) and grapheme (Gr) or fullerene (FI) are used as sorbents for the dispersive micro solid phase
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