Effects of residual double bonds on the catalytic activity and stability of Pt/SDB hydrophobic catalysts

Abstract

Pt/SDB hydrophobic catalysts, platinum supported on a cross-linked styrene-divinyl benzene copolymer (SDB), were prepared by an impregnating method. The results indicated that the content of the residual double bonds was positively proportional to the amount of divinyl benzene (DVB) and negatively proportional to the amount of initiator. When the molar ratio of DVB to St was 1 : 1, the content of the residual double bonds reached a highest value of 1.248 mmol g À1 . The influences of the contents of residual double bonds on the loading amounts of Pt, as well as the catalytic activity and stability of Pt/SDB catalysts were investigated. Performance tests demonstrated that the loading amounts of Pt increased correspondingly, as the contents of residual double bonds increased. Moreover, Pt/SDB with a higher content of residual double bonds generally had a higher column efficiency and a better stability.Interestingly, the column efficiencies of Pt/SDB with a highest content of residual double bond were all above 90% under all experiment conditions.

One‐pot reduction‐hydrophobization of heterogenized platinum with 1,1,3,3‐tetramethyldisiloxane

“…Generally, the reduction is achieved by passing hydrogen current at high temperature (230°C) for a long (12 h) [ 20 ] or shorter time (3 h at 160°C) [ 7 ] or in the temperature range 20°C to 80°C and a hydrogen partial pressure between 0.025 and 0.5 MPa. [ 32 ] It was found that the reaction rate increased with the partial pressure of hydrogen, its diffusion through the lamellar liquid film at the gas–liquid interface being the determinant of the reaction rate. [ 36 ]…”

“…It has been previously demonstrated that the activity of the second vinyl group from DVB is reduced significantly when the first vinyl is involved in polymerization. [32,33] During gelation process, some double bonds are entrapped in the initial formed network and could not further be reacted due to the steric hindrance. [34] Therefore, residual unreacted double bonds always remain in the SDVB copolymers.…”

“…Generally, the reduction is achieved by passing hydrogen current at high temperature (230 C) for a long (12 h) [20] or shorter time (3 h at 160 C) [7] or in the temperature range 20 C to 80 C and a hydrogen partial pressure between 0.025 and 0.5 MPa. [32] It was found that the reaction rate increased with the partial pressure of hydrogen, its diffusion through the lamellar liquid film at the gas-liquid interface being the determinant of the reaction rate. [36] Starting from literature that indicates silanes in general [37] and TMDS in particular [38] as a scalable, safe, regio-, stereo-, chemo-selective, and economically viable reducing agent, in this study, we used this one as a reducing agent for platinum.…”

“…The formation of the desired copolymer is proven by the presence of characteristic bands in the IR spectrum (Figure S10) as follows: [31,32] the bands at 698 and 758 cm À1 attributed to the deformation vibration of the C H bond in the aromatic nucleus; the bands at 1450, 1493, and 1601 cm À1 attributed to the stretching vibration of the C═C bond in the aromatic nucleus; bands at 2853 and 2922 cm À1 assigned to the ethyl groups contained in the ethyl-styrene of the technical DVB; and the bands at 3024-3082 cm À1 attributed to the C H bond stretching vibration in the aromatic nucleus. Furthermore, the bands corresponding to the stretch vibration of the vinyl groups at 1630 and 989 cm À1 (see the FTIR spectrum-Figure S10) were assigned to the stretching vibration of C═C bond [32] and the deformation vibration of ═C H bond, respectively, indicating the presence of residual double bonds in SDVB copolymer. It has been previously demonstrated that the activity of the second vinyl group from DVB is reduced significantly when the first vinyl is involved in polymerization.…”