Hydrogenation of Bisphenol A-Type Epoxy Resin (BE186) over Vulcan XC72-Supported Rh and Rh–Pt Catalysts in Ethyl Acetate-Containing Water

Abstract

This study demonstrates the hydrogenation of a bisphenol A-type epoxy resin (BE186) through solvent selection, development of a catalyst for aromatic ring hydrogenation, and control of epoxy loss. A functional greener solvent, water in ethyl acetate, was proposed based on solvatochromic parameters, high α and low β. RhO x present in Vulcan XC72supported monometallic Rh and bimetallic Rh−Pt catalysts prepared by the polyol method acted as a promoter for hydrogenation. The hydrogenation pathway to control epoxy loss was proposed through changes of the reactant to the catalyst ratio and temperature. Though Rh−Pt catalysts were superior to Rh for aromatic ring hydrogenation, they led to higher epoxy loss owing to excessive C−O bond cleavage. Using Rh 5 /Vulcan XC72-polyol, 3 wt % water in ethyl acetate, and a reactant to catalyst ratio of 100:1, complete hydrogenation of BE186 with 3.4% epoxy loss was achieved at a H 2 pressure of 1000 psi and 60 °C for 3.5 h.

Synthesis of Al-Modified SBA-15-Supported Ru Catalysts by Chemical Fluid Deposition for Hydrogenation of Dimethyl Terephthalate in Water

“…The aromatic rings of the reactants that are adsorbed on the active metal sites of the catalyst are polarized by the proton donated to them by water, thereby exposing them to undergo complete hydrogenation at the active sites via H 2 spillover. This leads to a considerable reduction in the activation energy for hydrogenation, and consequently, complete hydrogenation can be achieved at more benign reaction conditions with the help of functional solvent, water . The phenomenon of the on-water mechanism accelerating the rate of reaction in the use of water as the solvent was further validated when in the use of a common organic solvent, ethanol (Table , entry 14), the hydrogenation of DMT over the Ru 5 /Al 20 SBA-15 catalyst at 100 °C and 4.14 MPa H 2 pressure for 0.5 h gave only 70.2% conversion with 78.1% selectivity toward DMCD.…”

On-Water Hydrogenation of Polyethylene Terephthalate to Environmentally Friendly Polyester by the Catalyst Rh2.5Pt2.5/SBA-15

“…The most interesting aspect to be noted was that even though PET was completely insoluble in water, the hydrogenation of PET could proceed over the monometallic Rh 5 /SBA-15 and Pt 5 /SBA-15 catalysts under a vigorous stirring of 1000 rpm, thereby giving direct evidence of an advent of the on-water mechanism in the use of water as the solvent. , By choosing water as the solvent, a polarization in the aromatic rings in PET was induced via proton donation by water. This understanding was based on the high α value (solvatochromic parameter) of 1.17 of water, which represented its proton donation ability or its Brønsted acidity . By polarizing the aromatic rings in PET thereby making them more susceptible to hydrogenation by Rh and establishing a connection between the catalyst surface and aromatic rings of PET via H bonding at the aqueous interface of the catalyst and reactant, water acted as a functional solvent further catalyzing the hydrogenation of PET in its solid state.…”

“…The most interesting aspect to be noted was that even though PET was completely insoluble in water, the hydrogenation of PET could proceed over the monometallic Rh 5 / SBA-15 and Pt 5 /SBA-15 catalysts under a vigorous stirring of 1000 rpm, thereby giving direct evidence of an advent of the on-water mechanism in the use of water as the solvent. 19,22 By choosing water as the solvent, a polarization in the aromatic rings in PET was induced via proton donation by water. This understanding was based on the high α value (solvatochromic parameter) of 1.17 of water, which represented its proton donation ability or its Brønsted acidity.…”

“…This understanding was based on the high α value (solvatochromic parameter) of 1.17 of water, which represented its proton donation ability or its Brønsted acidity. 22 By polarizing the aromatic rings in PET thereby making them more susceptible to hydrogenation by Rh and establishing a connection between the catalyst surface and aromatic rings of PET via H bonding at the aqueous interface of the catalyst and reactant, water acted as a functional solvent further catalyzing the hydrogenation of PET in its solid state. By choosing SBA-15 as the support material, not only did the SBA-15 support introduce hydrophilicity but also the presence of surface −OH groups in SBA-15 assisted in the generation of the "on-water" mechanism via a H bonding at the aqueous interface of the catalyst and reactant.…”

“…Moreover, the presence of Si–OH groups on its surface was also expected to assist in the advent of a higher degree of on-water mechanism when water was used as the solvent through H-bonding at the catalyst–reactant interface . Rh–Pt synergy for the hydrogenation of not only PET but also other compounds containing aromatic rings such as DMT and bisphenol A-type epoxy resin, where Rh played the primary role of selectively hydrogenating the aromatic rings while Pt assisted in the orientation of the aromatic rings to the active sites of the catalyst in a bridge manner on Pt(111) for easier hydrogenation, has been well documented. ,,− Moreover, as reported by Greely and Mavrikakis, the binding energy (BE) for H 2 on the surface of Rh–Pt alloy NPs (2.57 eV) is lower than that on individual Rh (2.81 eV) or Pt (2.78 eV), leading to easier dissociation and spillover of H atoms on the Rh–Pt surface. Therefore, for the purpose of hydrogenating PET in water in this study, a Rh–Pt bimetallic catalyst supported on SBA-15 was considered.…”