Enhancing Oxidative Dehydrogenation Selectivity of Ceria‐Based Catalysts with Phosphorus as Additive

Abstract

Surface‐ and bulk‐phosphated ceria catalysts were prepared and studied in propane oxidative dehydrogenation (ODH) at 823 and 873 K. The catalysts were characterized by N2 adsorption at 77 K, XRD, TEM, and diffuse reflectance IR Fourier transform (DRIFT), Raman, X‐ray photoelectron (XPS), and energy dispersive X‐ray (EDX) spectroscopies. Both series of catalysts presented an increase in the ODH selectivity with respect to pure ceria mainly at the expense of total oxidation selectivity. Thus, the selectivity to propene was approximately 74 % with surface‐phosphated catalysts and 62 % with bulk‐phosphated catalysts. For the surface‐phosphated samples, P is confined to the surface and subsurface regions of the ceria particles, whereas P is also dispersed in the bulk of the oxide in the bulk‐phosphated samples. Finally, all the characterization techniques led us to the conclusion that Ce4+ cations that interact with P are responsible for the observed increase in the ODH.

The effect of phosphorus on the catalytic performance of nickel oxide in ethane oxidative dehydrogenation

“…The ODHselective sites were Ce(IV) cations interacting with phosphorus and, therefore, having a lowered redox ability. 41,42 Finally, it should be noted that adding phosphorus to a high surface area zirconia-supported NiO catalyst increased both its catalytic activity and ethylene selectivity in ethane ODH. 30 The presence of phosphorus enabled the Ni species to remain in an oxidized state during the ODH reaction, i.e.…”

“…39 The increased catalytic performance of P-modified cobalt oxide catalysts was attributed to their smaller crystallite size and to the presence of highly dispersed phosphate acting as an agent for the isolation of active sites. Adding phosphorus to ceria resulted in a decrease in the alkane conversion and concomitant increase in the selectivity in both isobutane 40 and propane 41 ODH reactions. The ODHselective sites were Ce(IV) cations interacting with phosphorus and, therefore, having a lowered redox ability.…”

Correlating Oxygen Species with Product Selectivity for Dehydrogenation of Butane over Titanium Mixed Oxide Catalysts

“…Based on the XPS spectra, three types of oxygen species are present on the catalysts. Considering that different oxygen species have different binding energies and electron densities, the selectivities of butenes and butadiene may be affected through adsorption or surface reaction. , The contents of the three oxygen species are calculated from the individual peak areas in Figure , and the results are shown in Figure . Comparing the ratios of the different types of oxygen with the products selectivities, it is noteworthy that the higher percentage of O-1 resulted in a higher butadiene selectivity over butenes.…”

“…These bands are the characteristic vibrational modes of butane. 33,34 In this IR spectrum, the adsorption is characterized by the symmetric C− H stretching of the terminal methyl groups, ν s (CH 3 ), at 2876 and 2967 cm −1 ; the asymmetric methyl deformation, δ as (CH 3 ), at 1432 cm −1 ; and the asymmetric stretching of methylene, ν as (CH 2 ) et , at 2928 cm −1 . Apparently, several new peaks appeared in the spectrum with increasing the temperature.…”

Highly dispersed CoOx in layered double oxides for oxidative dehydrogenation of propane: guest–host interactions

“…6 A similar strategy of isolating the active sites was also achieved in cerium phosphate catalysts. 7 On the other hand, we noted that hydrotalcite-like layereddouble-hydroxides (LDHs) contain positively charged brucite-like layers and exchangeable anions in the interlayer, which are conducive to the preparation of highly dispersed catalysts. The general molecular formula of an LDH is [M 2+ 1Àx M 3+…”