One-pot two-step process for direct propylene oxide production catalyzed by bi-functional Pd(Au)@TS-1 materials

Abstract

Different bi-functional materials (Pd(Au)@TS-1) based on metallic nanoparticles supported onto active nanocrystalline titanium silicalite (TS-1) zeolites were synthesized, characterized and used as recyclable heterogeneous catalysts for direct propylene oxide production from hydrogen, oxygen and propylene through one-pot two-step consecutive process. These catalysts allowed carrying out the combined reaction where metallic nanoparticles catalyzed the formation of in situ H 2 O 2 that was the necessary intermediate for propylene epoxidation catalyzed by active TS-1 nanocrystalline support. Several variables were considered such as use of supercritical CO 2 conditions, modifiable content of metallic species, and presence of additional co-solvents, surface acidity inhibitors and H 2 O 2 stabilizers. Reusability and stability of the bi-functional catalyst was showed through consecutive catalytic cycles.

The direct synthesis of hydrogen peroxide over Au and Pd nanoparticles: A DFT study

“…31 The suggested mechanisms for epoxidation here involve hydrogen peroxide or hydroperoxyl species that are generated and used in situ, with the nanoparticles supported on a material with epoxidation catalysing sites such as anatase TiO2, or porous titania containing materials like TS-1. 32,33 We have also shown that nanoparticles of AuPd alloys are active catalysts for the oxidation of methane to partial oxidation products, particularly methanol. Initially, using nanoparticles supported on titania, 34,35 it appeared that this reaction required the use of hydrogen peroxide as oxidant, and since the current market price of hydrogen peroxide is greater than methanol this imposes unacceptable costs on the process.…”

The Direct Synthesis of H2O2 Using TS‐1 Supported Catalysts

“…In particular the catalytic conversion of propylene to propylene oxide is a pertinent example of a major industrial process that utilises TS‐1, with over 1.2 Mt of propylene oxide produced annually, and the vast majority utilised in the production of polyurethane via the HPPO process. Furthermore, a growing interest has been placed on Au, and Au‐Pd, nanoparticles supported on TS‐1 for the in situ generation of H 2 O 2 for a variety of selective oxidation reactions. We have previously investigated the role of zeolites such as TS‐1, HZSM‐5 and zeolite‐Y as supports for precious metals in the direct synthesis of H 2 O 2 , as well as CO oxidation, with H 2 O 2 productivities for the zeolite supported catalysts much greater than the analogous catalysts supported on common oxide supports including TiO 2 , Al 2 O 3 and SiO 2 likley due to their strong acid characters.…”

Bimetallic Nanoparticles in Alternative Solvents for Catalytic Purposes

“…Despite the most straightforward production process for propylene oxide synthesis, which is the direct oxidation of propylene with O 2 , the major hurdles to obtain a highly pure monomer under safe and high yielding processes have precluded major industrial applications. Díaz, Corma et al reported an elegant one-pot two-step process for direct propylene oxide production from propylene, H 2 , and O 2 catalyzed by a bifunctional material (Pd(Au)@TS-1) based on metallic NPs supported on nanocrystalline titanium silicalite (TS-1) zeolites [122]. The resulting metallic nanoparticles encompassed the in situ formation of H 2 O 2 in a controlled fashion, which triggered propylene epoxidation catalyzed by the TS-1 nanocrystalline matrix support, working under safe supercritical CO 2 conditions.…”

“…The resulting metallic nanoparticles encompassed the in situ formation of H 2 O 2 in a controlled fashion, which triggered propylene epoxidation catalyzed by the TS-1 nanocrystalline matrix support, working under safe supercritical CO 2 conditions. These bifunctional catalysts showed high reusability and stability demonstrated through several catalytic cycles, yielding a more sustainable process for future industrial applications [122]. For a summary of BMNPs in supercritical fluids applied in catalysis, see Table 4 at the end of this section.…”