Enhanced stability for propene epoxidation with H2 and O2 over wormhole-like hierarchical TS-1 supported Au nanocatalyst

Abstract

Designing highly efficient Au/Ti-containing catalysts for propene epoxidation with H2 and O2 harbors tremendous scientific and industrial importance. In this work, novel hydrophobic hierarchical TS-1 (HTS-1) with wormhole-like mesopores (ca. 45 nm) and small crystal size (100 nm) is firstly synthesized by a two-step crystallization method using CTAB as template. Gratifyingly, the Au/HTS-1 catalyst shows simultaneously high PO formation rate of 150 gpoh -1 kgCat -1 without any promoter additive, PO selectivity of 90 % and impressive stability of 100 h, which are much better than traditional Au/TS-1 catalyst. Furthermore, the intrinsic reason for the enhanced performance is elucidated by multi-techniques such as N2 physisorption, HRTEM, TGA, FT-IR and 29 Si NMR.Interestingly, it is found that the coke in 0.10 wt% Au/HTS-1 catalyst partly reside in mesopores, alleviating the deactivation of micropore blocking. Moreover, the enhanced mass transfer ability and higher hydrophobicity of Au/HTS-1 catalyst also lead to reduced coke weight and absence of aromatic coke.

Biophenol-Mediated Solvent-Free Synthesis of Titanium Silicalite-1 to Improve the Acidity Character of Framework Ti toward Catalysis Application

“…However, the PO selectivity decreases slightly in both catalysts because of the partial isomerization of the rapidly generated PO adsorbed on the catalysts. Besides, as shown in Figure c,d, after being used at 300 °C for 48 h, the bio-TS-1-based catalyst shows a less coke weight of 2.62%, which is only 50% of the weight value for the TS-1 based catalyst, indicating a better coke-resistant ability of bio-TS-1. , …”

“…Both samples are in quasi sphere-like shape with an average particle size of around 500 nm. Moreover, compared with those hydrothermally prepared counterparts, − these solvent-free synthesized particles exhibit a unique aggregation morphology composed of small coffin-like crystals (seen in Figures b–d and S1). , Noticeably, followed by the solid-transform mechanism in this process, Ti and Si sources undergo homogeneous condensation reaction to generate small crystals, which subsequently aggregate to form the overall titanium silicalite-1 zeolite with the progress of crystallization .…”

“…For the sake of clarity, 29 Si MAS NMR was carried out to further measure the defect in bio-TS-1. As shown in Figure , after deconvolution of the spectra, the two samples show typical resonances at −116, −113, and −103 ppm, corresponding to the orthorhombic structure, Q 4 species [Si­(OSi) 4 ], and Q 3 silanol species [Si­(OSi) 3 OH], respectively. , However, compared with bio-TS-1, TS-1 shows the presence of Q 2 species [Si­(OSi) 2 (OH) 2 ] accompanied by a lower Q 4 / Q 3 ratio, suggesting more defects in zeolite with the absence of biophenol. , Based on related literature studies, , such a defective situation would be conspicuously alleviated when titanium is effectively inserted into the framework. Considering that bio-TS-1 manifests less defects, the mediating agent of biophenol used here exerts a positive effect on the titanium insertion into the zeolite framework.…”

Uncalcined TS‐2 immobilized Au nanoparticles as a bifunctional catalyst to boost direct propylene epoxidation with H2 and O2

“…This deduction would be supported by the analysis of the DTG profiles in Figure c,d. Clearly, the spent Au/TS‐2‐B catalyst exhibits one broad DTG peak centered at about 410°C, while the spent Au/TS‐1‐B catalyst with three obvious DTG peaks centered at about 390, 460 and 640°C, where the two high‐temperature peaks could be attributed to hard coke such as polyalkenes and refractory aromatic species . This could provide a rational interpretation for the higher stability of the Au/TS‐2‐B catalyst because of the suppressed formation of the hard cokes.…”

Advances in Designing Au Nanoparticles for Catalytic Epoxidation of Propylene with H2 and O2

“…Feng et al also proposed that Au dispersed in core-shell TS-1/silicalite-1 catalysts exhibited high catalytic stability and that the PO formation rate could reach up to 126 g·kgcat −1 ·h −1 , with high PO selectivity (>80%), for over 100 h of time-on-stream (Figure 5f,g) [52]. In another approach, Feng et al designed a novel hydrophobic hierarchical TS-1 support (HTS-1) that maintained a high PO formation rate (150 g·kgcat −1 ·h −1 ) for over 100 h of time-on-stream [53]. The boosting properties of mass transfer and the hydrophobicity of the Au/HTS-1 catalyst diminish coking, extending the high catalytic activity.…”