Effect of Ca²⁺ Position in Zeolite Y on Selective Oxidation of Propane at Room Temperature

Abstract

The activity of CaNaY zeolites in selective oxidation of propane with increasing Ca 2+ content at room temperature was studied with infrared spectroscopy and ammonia temperature-programmed desorption. Increasing the Ca 2+ exchange level in CaNaY zeolites resulted in a variety of altered properties: the amount of Brönsted and Lewis acid sites increased, the adsorption of propane increased, the initial acetone formation rate increased, and the desorption of acetone retarded. Moreover, all of these properties showed a sudden change with Ca 2+ content above the 50% Na + exchange level, which can be fully attributed to the location of Ca 2+ in the Y-zeolite framework. It is convincingly shown that only Ca 2+ ions located in the supercage contribute to the formation of Brönsted and Lewis acidity as well as propane oxidation activity at room temperature.

Evidence for the catalytic properties of ultramarine pigment

“…tor 6-12 [25]. The enhancement by calcium on catalytic activity is also shown more recently by Xu et al [26].…”

Proteome modifications of the medicinal leech nervous system under bacterial challenge

“…2). In addition, peptide sequences obtained from spot 1759 (upregulated after 1 h of bacterial exposure) are specific to gliarin, a protein previously described in H. medicinalis glial cells [28]. These proteins are representatives of two of the three types of cytoskeletal filaments, microfilaments and intermediate filaments, respectively [28][29][30].…”

Cadmium Modified HZSM-5: A Highly Efficient Catalyst for Selective Transformation of Methanol to Aromatics

“…55 The activity of Y zeolite exchanged with Ca 2+ is significantly higher compared to that with Mg 2+ . 56 A later study concerning the conformation of alkane adsorbed on zeolites cations using "atom in molecules" by Pidko et al 55 reveals that, compared to the Ca 2+ cation, the Mg 2+ cation exchanged in faujasite is strongly shielded by the surrounding zeolitic oxygens due to its smaller radius and hence significant stabilization of the adsorbed complex comes from the weak hydrogen bonds between the H atoms of the alkane and O atom of the cation sites. The preferred conformation of the adsorbed alkane is to a significant extent controlled by the resulting steric constrains, which lead to a longer hydrocarbon− cation bond.…”