Highly Efficient Epoxidation of Propylene with In Situ-Generated H₂O₂ over a Hierarchical TS-1 Zeolite-Supported Non-Noble Nickel Catalyst

Abstract

Propylene epoxidation with H 2 and O 2 to propylene oxide (PO) is a very valuable reaction. Considering the precious gold catalysts commonly used in the current research, the design of highly active non-noble metal catalysts is a huge challenge. Herein, we report a non-noble Ni/TS-1 catalyst, supported Ni nanoparticles on a hierarchical titanium silicate-1 (TS-1) zeolite by the deposition precipitation method, which exhibits desirable catalytic performance in the gas-phase epoxidation of propylene due to the strong metal−support interaction between Ni NPs and TS-1. Significantly, the prepared 2%Ni/TS-1 exhibited high PO selectivity of 76.8%, PO formation rate of 151.9 g PO /(h•Kg cat ), and long-term stability at 200 °C. Notably, the catalytic performance of Ni/TS-1 is higher than that of the goldbased catalyst in the same condition. Furthermore, the reaction mechanism was investigated by various characterizations, including high-resolution transmission electron microscopy (HR-TEM), extended X-ray absorption fine structure (EXAFS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and in situ electron paramagnetic resonance (EPR), proving that metallic Ni was the dominant nickel species, and the presence of nickel species was found to catalyze the reaction between hydrogen and oxygen, which could induce the formation of active radicals ( • O 2 − , and • OOH) to achieve the in situ synthesis of H 2 O 2 and subsequently oxidize propylene to PO. In addition, density functional theory (DFT) calculations indicated that the passivation layer on the Ni surface facilitates the production of H 2 O 2 . This work provides a promising way for the highly efficient catalyst on the selective oxidation with non-noble metals.

An Overview of Metal Density Effects in Single-Atom Catalysts for Thermal Catalysis

“…Alkene epoxidation is a crucial chemical reaction that employs widespread applications in the synthesis of plasticizers, epoxy resins, perfumes, pharmaceuticals, and fine chemicals. ,,− To achieve more sustainable and friendly alkene epoxidation, O 2 as the green oxidant is highly desirable. However, realizing high selectivity for the desired product remains a challenge with traditional catalysts, accompanied by the formation of undesirable byproducts like aldehydes. , High-density SACs may be promising candidates to enhance the selectivity in alkene epoxidation due to their unique electronic and geometric structures.…”

Investigation on Titanium Silicalite-1 Zeolite Synthesis Employing ATPAOH as an Organic Structure Directing Agent

“…This function has recently been found and applied in the synthesis of aluminum-containing zeolites such as ZSM-5, H-MOR, MCM-22, etc. − The strong interaction between OSDAs and the inorganic host is studied, and it inspires efforts to tailor the framework Al by optimizing OSDAs . The distribution of Ti species within the matrix is also crucial for TS-1 zeolite, as its content, − coordination states, − as well as accessibility − determines the catalytic performance of TS-1 zeolite. Several strategies , have been developed to adjust the distribution of heteroatoms in the zeolite skeleton.…”

Electrochemical Epoxidation of Propylene to Propylene Oxide via Halogen-Mediated Systems

“…At present, chlorine-mediated electrochemical epoxidation of olefins such as ethylene and styrene is receiving extensive interest. , Compared with the chlorohydrin process in industry, the halogen-mediated electrochemical epoxidation method uses halogen as a medium to continuously circulate in the system to avoid large amounts of waste residue emissions and to improve economy . In addition, compared with the thermally mediated epoxidation using oxygen as the oxygen source with a reaction temperature of around 200 °C, the electrochemical epoxidation using H 2 O as the oxygen source at ambient conditions is more operable and safer and could achieve higher selectivity and yields. , However, among all halogen systems, the chlorine-mediated system has a relatively higher cell potential and energy loss due to the high standard potential of chlorine, which is also similar to that of the competitive oxygen evolution reaction (OER) …”

“…1 In addition, compared with the thermally mediated epoxidation using oxygen as the oxygen source with a reaction temperature of around 200 °C, the electrochemical epoxidation using H 2 O as the oxygen source at ambient conditions is more operable and safer and could achieve higher selectivity and yields. 13,14 However, among all halogen systems, the chlorine-mediated system has a relatively higher cell potential and energy loss due to the high standard potential of chlorine, which is also similar to that of the competitive oxygen evolution reaction (OER). 15 Herein, we explored the potential of different halogen systems to mediate the electrochemical epoxidation of propylene, using titanium-supported ruthenium dioxide (RuO 2 /Ti) as the anode, to obtain halogen-mediated systems with better propylene electrochemical epoxidation performance and efficiency.…”

“… 1 In addition, compared with the thermally mediated epoxidation using oxygen as the oxygen source with a reaction temperature of around 200 °C, the electrochemical epoxidation using H 2 O as the oxygen source at ambient conditions is more operable and safer and could achieve higher selectivity and yields. 13 , 14 However, among all halogen systems, the chlorine-mediated system has a relatively higher cell potential and energy loss due to the high standard potential of chlorine, which is also similar to that of the competitive oxygen evolution reaction (OER). 15 …”