Propylene epoxidation with O2 and H2: a high-performance Au/TS-1 catalyst prepared via a deposition–precipitation method using urea

Metal-Free Phosphated Mesoporous SiO2 as Catalyst for the Low-Temperature Conversion of SO2 to H2S in Hydrogen

“…By comparison, the phosphorization processes in the solution of oleylamine and trioctylphosphine for the sample “m-SiO 2 ” (as-made mesoporous SiO 2 without calcination) and the “m-SiO 2 -cal sample” were run to achieve the “uf-P@m-SiO 2 ” sample (containing organic residual template to improve the P loading) and the sample “uf-P@m-SiO 2 -cal” (without organic residual template) ( Table 1 ). It has been reported that the active component can be highly dispersed by the assistance of the surfactant during the synthesis of a zeolite-supported catalyst [ 27 ]. We consider that the P-related phase (phosphates) dispersion was effectively influenced by the presence of surfactants, which may lead to the difference observed in the catalyst performance.…”

“…During the phosphorization step, when the temperature goes above 200 • C, the TOP slowly decomposes, and the P is slowly loaded onto the SiO 2 surface. Without the presence of the surfactant, the loading of P is similar to a conventional impregnation step, with no surface control of the P position and subsequent P aggregation, while with the assistance of the surfactant, the P site can be dispersed slowly and uniformly on the SiO 2 matrix to avoid any aggregation, thus leading to the high population of active sites [16,27]. For the long-term test, the residual CTAB gradually decomposed during the reaction process at high temperature, resulting in the change in the dispersion state of the active phosphates component on the surface, and the activity of uf-P@m-SiO 2 slowly decreases.…”

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

“…It can be clearly observed in Figure b,c that in the initial induction period, the Au/TS‐2‐B catalyst exhibits much lower selectivity to PO but much higher selectivity to CO 2 and ethanal than the Au/TS‐1‐B catalyst. This indicates the occurrence of CC bond cleavage, possibly resultant from the further cracking reactions of PO . After the induction period, the two catalysts give rise to relatively high selectivity to PO as well as the suppression of the CC bond cleavage, where the Au/TS‐2‐B catalyst shows higher selectivity to PO compared to the Au/TS‐1‐B catalyst.…”

“…Similarly, uncalcined titanium silicalite‐1 (TS‐1‐B) with the same Si/Ti molar ratio was also synthesized except using tetrapropylammonium hydroxide (TPAOH) to replace TBAOH as the template agent. The Au/TS‐2‐B catalyst and the referenced Au/TS‐1‐B catalyst with the same gold loading of ~0.09 wt% were prepared via the DPU method according to the procedure previously reported, where the gold loadings of the two catalysts were determined by inductive coupled plasma atomic emission spectrometry (ICP‐AES, IRIS 1000).…”

“…Deposition–precipitation (DP) method based on the isoelectric point principle is an effective way to selectively deposit Au nanoparticles nearby the active isolated Ti 4+ sites for preparing Au–Ti bifunctional catalysts . The precipitant agent using urea has shown much higher Au capture efficiency on the uncalcined titanium silicates (e.g., TS‐1‐B) than that using NaOH or Na 2 CO 3 (<3%) due to the formation of different gold species . In addition, the former method can also avoid introducing alkaline ions such as Na + , which have been reported to remarkably affect the reaction .…”