Effect of Sodium on the Catalytic Properties of VO_x/CeO₂ Catalysts for Oxidative Dehydrogenation of Methanol

Abstract

A series of VO x /CeO 2 catalysts with various sodium loadings (Na/V ratio from 0 to 1) have been studied for oxidative dehydrogenation (ODH) of methanol. The effect of sodium on the surface structure, redox properties, and surface acidity/basicity of VO x /CeO 2 was investigated using hydrogen temperature-programmed reduction (H 2 -TPR), Raman spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The experimental results indicate that the effect of sodium on VO x /CeO 2 is highly dependent on the Na/V ratio. At a low Na/V ratio (Na/V < 0.25), sodium addition only slightly decreases the redox ability of VO x /CeO 2 and has little effect on its activity and selectivity to formaldehyde, even though the Bronsted acidity is almost completely eliminated at a Na/V ratio of 0.25. At a high Na/V ratio (Na/V > 0.25), sodium addition greatly alters the nature of the active sites by V−O−Ce bond cleavage and V−O−Na bond formation, leading to significantly reduced activity of the VO x / CeO 2 catalysts. At Na/V > 0.25, the selectivity to formaldehyde also decreases with increasing Na/V ratio due to (1) the suppressed reducibility of VO x and (2) increased basicity leading to increased CO 2 .

Effect of Oxygen Defects on the Catalytic Performance of VOx/CeO2 Catalysts for Oxidative Dehydrogenation of Methanol

“…The obtained white suspension was centrifuged and the precipitated CeO 2 paste was then thoroughly washed with DI water and ethanol for several times to remove sodium and other impurities. 15 The detailed hydrothermal preparation conditions and physical properties of CeO 2 nanocubes are listed in Table 1. The prepared CeO 2 nanocubes were denoted as CeO 2 -C-68, CeO 2 -C-34 and CeO 2 -C-25 respectively, where numbers represent the average size of corresponding CeO 2 nanocube supports based on TEM observation.…”

Elucidation of the roles of Re in steam reforming of glycerol over Pt–Re/C catalysts

“…Raman spectra of the catalyst samples were collected on a Horiba LabRAM HR Raman microscope system as previously reported [27].…”

“…Steam reforming of glycerol was performed with a fixed-bed reactor as described previously [27], which basically consists of a vaporizer, a quartz tube (i.d. = 8 mm), and a condenser to separate the gas-liquid mixture.…”

Investigation of the promoting effect of Mn on a Pt/C catalyst for the steam and aqueous phase reforming of glycerol

“…A lab-scale test unit with a fixed-bed reactor was used for the steam reforming reactions [32]. In a typical experiment, a certain amount of catalyst diluted with SiC (60-100 mesh, five times dilution in weight) was held in place by quartz wool in a quartz tube.…”