Mixed complexes of acetylene-ethylene are studied using vacuum-ultraviolet (VUV) photoionization mass spectrometry and theoretical calculations. These complexes are produced and ionized at different distances from the exit of a continuous nozzle followed by reflectron time-of-flight mass spectrometry detection. Acetylene, with a higher ionization energy (11.4 eV) than ethylene (10.6 eV), allows for tuning the VUV energy and initializing reactions either from a C2H2(+) or a C2H4(+) cation. Pure acetylene and ethylene expansions are separately carried out to compare, contrast, and hence identify products from the mixed expansion: these are C3H3(+) (m/z = 39), C4H5(+) (m/z = 53), and C5H5(+) (m/z = 65). Intensity distributions of C2H2, C2H4, their dimers and reactions products are plotted as a function of ionization distance. These distributions suggest that association mechanisms play a crucial role in product formation closer to the nozzle. Photoionization efficiency (PIE) curves of the mixed complexes demonstrate rising edges closer to both ethylene and acetylene ionization energies. We use density functional theory (ωB97X-V/aug-cc-pVTZ) to study the structures of the neutral and ionized dimers, calculate their adiabatic and vertical ionization energies, as well as the energetics of different isomers on the potential energy surface (PES). Upon ionization, vibrationally excited clusters can use the extra energy to access different isomers on the PES. At farther ionization distances from the nozzle, where the number densities are lower, unimolecular decay is expected to be the dominant mechanism. We discuss the possible decay pathways from the different isomers on the PES and examine the ones that are energetically accessible.
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http://dx.doi.org/10.1021/acs.jpca.6b00107 | DOI Listing |
Phys Chem Chem Phys
January 2025
The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, 430081, China.
At present, the modification of palladium (Pd) catalysts is an important topic due to its potential to enhance catalytic performance and reduce catalyst costs. In this work, boron (B) and carbon (C) are interstitially doped into the subsurface of Pd to construct PdB and PdC catalysts. The adsorption properties of acetylene and ethylene, the mechanism of acetylene hydrogenation, and ethylene selectivity are studied based on density functional theory (DFT) calculations.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Institute of Catalysis, Zhejiang University, Hangzhou 310027, China.
Selective coupling of C platform molecules to C olefins is a cornerstone for establishing a sustainable chemical industry based on nonpetroleum sources. Vinyl chloride (CHCl), one of the top commodity petrochemicals, is commercially produced from coal- or oil-derived C hydrocarbon (acetylene and ethylene) feedstocks with a high carbon footprint. Here, we report a C-based route for vinyl chloride synthesis via the selective oxidative coupling of methyl chloride.
View Article and Find Full Text PDFInorg Chem
January 2025
School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China.
The ability to finely tune the nuclearity of active metal sites is critical for designing highly selective catalysts, especially for hydrogenation processes. In this work, we developed a novel PdCu catalyst with an ordered body-centered cubic (BCC) structure, enabling precise control over Pd nuclearity to optimize selectivity. Using a facile polyol synthesis method, we modulated the Pd coordination environment, reducing the Pd-Pd coordination number from 3 (disordered face-centered cubic, FCC) to 0 (ordered BCC), thereby achieving full isolation of Pd by the surrounding Cu atoms.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
State Key Laboratory of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, P. R. China.
One-step adsorptive purification of ethylene (CH) from ternary mixture comprising of acetylene (CH), ethylene (CH) and carbon dioxide (CO) is a great challenge in the chemical industry. Herein, a microporous metal-organic framework (FJI-H38) has been reported, which possesses high-density electronegative O/N binding sites and appropriate pore size. Notably, at 0.
View Article and Find Full Text PDFMater Horiz
January 2025
School of Materials Science and Engineering, National Institute for Advanced Materials, Nankai University, Tianjin, 300350, China.
The semi-hydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry, and palladium-based metallic catalysts are currently employed. Unfortunately, a fairly high cost and uncontrollable over-hydrogenation impeded the application of Pd-based catalysts on a large scale. Herein, a sandwich structure single atom Pd catalyst, Z@Pd@Z, was prepared impregnation exchange and epitaxial growth methods (Z stands for ZIF-8), in which Pd single atoms were stabilized by pyrrolic N in a zeolitic imidazolate framework (ZIF-8).
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