Methanol Synthesis From Co2 H2 Over Pd Promoted Cu Zno Al2o3 Catalysts

Author : Xiao Jiang
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (943 download)

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Download or read book Palladium-Copper Bimetallic Catalysts for Selective Carbon Dioxide Hydrogenation to Methanol written by Xiao Jiang and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic CO2 hydrogenation for synthesis of methanol has attracted significant attention recently as a way of recycling carbon dioxide as a resource. In the past decades, most prior works focused on Cu-based and supported Pd-based catalysts to hydrogenate CO2 to CH3OH. Cu and Pd were proposed to have different affinities towards the adsorption of CO2 and H2, respectively. However, little attention has been paid to the effect of Pd-Cu bimetallic catalysts on the methanol synthesis from CO2 hydrogenation. Thus, this work aims at studying the effect of combining Pd and Cu on the activity and selectivity of methanol synthesis via CO2 hydrogenation and developing a fundamental understanding on composition-structure-activity relationship. The Pd-Cu bimetallic catalysts with various compositions were prepared and examined in CO2 hydrogenation at relatively mild reaction conditions (523 K and 4.1 MPa).A strong synergistic effect was observed over Pd--Cu bimetallic catalysts supported on silica at specific compositions as evidenced from the superior methanol formation rate and selectivity in comparison to monometallic catalysts, and the optimal Pd/(Pd+Cu) atomic ratios lied in the range of 0.25-0.34. The methanol formation rate over Pd(8.7)-Cu(10)/SiO2 was almost three times higher than the simple sum of those over monometallic Cu and Pd catalysts. To investigate the composition-structure-activity relationship, the Pd-Cu bimetallic catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (STEM/EDS), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), and temperature-programmed desorption (H2-, CO2-, & CO-TPD). Detailed characterization results demonstrated the importance of two well-dispersed Pd--Cu alloy particles (PdCu3 and PdCu) for the observed methanol promotion over Pd--Cu bimetallic catalysts. DRIFTS spectra revealed that the incorporation of Pd and Cu greatly improved the formation of formate and CO species during the CO2 hydrogenation. CO-TPD profiles confirmed the existence of three forms of chemisorbed CO species, and the bonding strength increased in the following order: COL (linear)