Facet-Dependent selectivity of CeO2 nanoparticles in 2-Propanol conversion

Assessment of Lewis‐Acidic Surface Sites Using Tetrahydrofuran as a Suitable and Smart Probe Molecule

“…In addition, the most active sample during the dehydration reaction of IPA to propylene, that is, MoO 3 ‐10 %CdO, as will be presented in Figure 8, gained the highest population of acidic surface sites besides the highest surface area (Table 1 and Figure 4 ). Its highest catalytic activity is attributed to these acidic sites [18] . This supports our hypothesis that THF outperforms pyridine in screening the acidic surface sites of our low‐surface area samples.…”

“…Obviously, the deconvolution Gaussian line shape of this profile accurately classified these acidic sites as two peaks of weak sites, one peak of medium sites, and a single peak of strong acidic sites (see Figure 7 b), as well as that peak of the physisorbed probe molecules of THF. Many published articles applied NH 3 ‐TPD technique[ 4 , 5 , 15 ] to classify the strength of the acidic sites, while others measured the IR‐spectra of pyridine[ 1 , 3 , 18 , 20 ] for the same purpose. Nothing was stated about quantitatively estimating the acidic sites with pyridine or using pyridine‐recorded DSC‐TPD profiles.…”

“…At the corresponding reaction temperature, the reactivity of each sample slightly varied in comparison with other samples. This could be due to the different facets of both MoO 3 and CdMoO 4 hosted in MoO 3 and exposed to IPA molecules [18] during the dehydration reaction of IPA. Furthermore, the limited surface area of these samples is an important factor that reflects this discrepancy in their recorded reactivity.…”

“…On the other hand, were incompatible with the calculated number of acidic sites in total samples using TG‐TPD of pyridine. In a recently published paper, [18] based on their findings, the authors suggested that infrared (IR) spectroscopy of Pyr can be used to qualitatively identify the different types of acidic sites, but it was unable to accurately determine these sites quantitatively. Therefore, the majority of the published articles concerning the acidity measurements of catalysts used IR spectroscopy of pyridine and TG and/or DSC TPD of NH 3 to quantify total acidity [1,3,45,46] .…”

“…Scheme 1 gives general form of the adsorption modes of THF with Lewis and Bronsted sites. The dehydration reaction of isopropyl alcohol (IPA)[ 18 , 19 ] was carried out over these samples in a fixed‐bed reactor with a continuous flow system under atmospheric pressure as follows: 200 mg of each sample was used and stabilised in a stream of dry N 2 (in 1 cm i.d. pyrex glass reactor and 16.5 cm long) for 1 h at 400 °C before measurements.…”