Hydrogenation of dioctyl phthalate over a Rh-supported Al modified mesocellular foam catalyst

Abstract

The solvent free hydrogenation of DOP to DEHHP over an Al modified MCF supported Rh catalyst.

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

“…From the HR-TEM images of Rh 5 /SBA-15 and Rh 2.5 Pt 2.5 /SBA-15, as shown in Figure a,b, respectively, it could be seen clearly that almost all the NPs were located inside the cylindrical channels of SBA-15. The P 6 mm symmetry of the SBA-15 support was seen to be preserved clearly from the TEM images even after reduction with H 2 at 400 °C, which corroborated well with previous observations made using SBA-15-supported catalysts synthesized via CFD by our group. , On calculating the average Rh and Rh–Pt NP sizes using ImageJ, an average Rh size of 5.5 nm and a Rh–Pt NP size of 3.8 nm both were smaller than the pore diameter of SBA-15, showing that the growth of Rh and Rh–Pt NPs was controlled by the pore size of SBA-15. The smaller size of the Rh–Pt alloy NPs as compared to Rh NPs suggested a better catalytic activity possessed by the Rh–Pt alloy for the hydrogenation of PET, which was also observed in the hydrogenation of terephthalic acid .…”

“…Rh–Pt synergy, wherein Rh primarily performed the selective hydrogenation of aromatic rings while Pt assisted in the orientation of the aromatic rings in PET to the active sites of the catalyst in a bridge manner on Pt(111) at the aqueous catalyst–reactant interface thereby exposing the aromatic rings in PET to be attacked by the spillover H atoms and hydrogenation by Rh, was therefore the main cause for the enhanced hydrogenation activity of Rh 2.5 Pt 2.5 /SBA-15. , It has also been previously proven by Greely and Mavrikakis using the first-principles density functional theory calculations that H 2 possesses a weaker BE on the surface of Rh–Pt alloy NPs (2.57 eV) when compared to individual Rh (2.81 eV) or Pt (2.72 eV) NPs and therefore dissociates and spills over more easily by Rh 2.5 Pt 2.5 /SBA-15. The Rh–Pt synergy driving the good catalytic activity of Rh 2.5 Pt 2.5 /SBA-15 was therefore a combination of the above-mentioned reasons.…”

“…Although a reduction in the surface area was observed after the loading of the metal catalysts, it was not very significant and the reduction in the surface area was attributed to the deposition of the pores of SBA-15 with Rh and Rh–Pt alloy NPs. Moreover, the desorption pore diameter of SBA-15 (6.1 nm) versus Rh 5 /SBA-15 (5.9 nm) and Rh 2.5 Pt 2.5 /SBA-15 (5.1 nm) was not a big reduction, indicating that the NPs of Rh and Rh–Pt were well dispersed and deposited inside the pores of SBA-15 rather than being deposited near the pore mouths of the support due to agglomeration, which was one of the major advantages of catalyst synthesis using CFD over conventional techniques such as wet impregnation. , The negligible surface tension of scCO 2 as well as its gas-like viscosity assisted the good dispersion and deposition of metal NPs inside the pores of SBA-15 during synthesis by CFD. This was further augmented by the fact that the practical metal loadings of Rh and Pt in Rh 2.5 Pt 2.5 /SBA-15 as measured using ICP-OES were found to be 2.0 wt % or 80.0% and 2.2 wt % or 88.0% of the theoretical metal loadings, respectively, which was a very high practical loading when compared to the practical metal loadings obtained in conventional synthesis techniques such as wet impregnation .…”

“…SBA-15 was synthesized by the method previously reported by our group . In brief, for the typical synthesis of SBA-15, 26 g of DI water was mixed with 4 g of P123 template, and P123 was dissolved completely in water by stirring at 40 °C for 2 h. Next, 2 M HCl (116 g) was added and the acidic solution was further stirred at 40 °C for 2 h. TEOS as the Si source (8.50 g) was then introduced dropwise (0.05 mL/s) under stirring, and the resulting mixture was continuously stirred for 20 h at 40 °C, followed by aging in an autoclave for 24 h at 80 °C.…”

“…In CFD-based catalyst synthesis, advantages such as easy availability, tunability, and low toxicity of supercritical CO 2 used as the solvent plus the prevention of NP aggregation at the pore mouths of the support made the use of CFD highly desirable . Previously, silica-supported Rh and Rh–Pt catalysts synthesized using CFD were tested by our group to be superior to catalysts synthesized by conventional techniques such as wet impregnation for the hydrogenation of aromatic compounds. , SBA-15 was chosen as the support material for this study owing to not only its good hydrothermal stability and well-ordered structure but also its hydrophilic nature that ensured a good dispersion of the catalyst in water. 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 .…”