Adsorption and Tautomerization Reaction of Acetone on Acidic Zeolites: The Confinement Effect in Different Types of Zeolites

Abstract

The adsorption and tautomerization reaction of acetone in H-FER, H-ZSM-5, and H-MCM-22 zeolites has been studied using full quantum calculations at the M06-2X/6-311+G(2df,2p) level of theory. The combination of a large quantum cluster and this meta-hybrid density functional results in reasonably accurate adsorption energies of -26.9, -28.1, and -23.9 kcal/mol for acetone adsorption in H-FER, H-ZSM-5, and H-MCM-22, respectively. Due to the acidity of the zeolite and the framework confinement effect, the tautomerization of acetone proceeds through a much lower activation barrier than in the isolated gas phase or in the presence of water molecules alone. The activation energies are calculated to be 24.9, 20.5, and 16.6 kcal/mol in H-FER, H-ZSM-5 and H-MCM-22, respectively. The endothermic reaction energy decreases with increasing of the zeolite pore sizes and amounts to 22.7, 17.6, and 15.9 kcal/mol for the reaction in H-FER, H-ZSM-5 and H-MCM-22, respectively. In addition, the adsorbed acetone enol is found to be highly unstable in the zeolite framework and readily reverse-transforms to adsorbed acetone with a very small activation energy. The activity trend and relative stabilities of the adsorbed keto and enol forms are well correlated with the interactions within the Brønsted acid site.

Lewis and Brönsted acidic sites in M4+-doped zeolites (M=Ti, Zr, Ge, Sn, Pb) as well as interactions with probe molecules: A DFT study

“…It is applicable to acetone and water, wherein only the covalent structure exists (Table 5 and Fig. 7) [52,69,70]. For pyridine (Py) adsorption, stronger Brönsted acidic sites result in only ionic structures, and weaker Brönsted acidic sites cause co-existence of the ionic and covalent structures, see Ti, Ge and Zr in Fig.…”

The Effect of Nano Confinement on the C–H Activation and its Corresponding Structure-Activity Relationship

“…The confinement effects have been observed theoretically in many reaction processes, such as D + H 2 → HD + H in CNTs23, ethylene oligomerization in zeolitic mesopores24, propene metathesis reaction in zeolites25, syngas reaction in CNTs26, ethylene dimerization in zeolites27, O 2 dissociation between two Pt (111)28, H 2 dissociation in CNTs29, and acetone tautomerization in zeolite30. Why does confinement influence the reaction in channels?…”

Effect of Transition Metals on the Electrical Conductivity Response of dPPV/Zeolite Y Composites toward Ketone Vapors

“…14,24,[30][31][32] The characteristics of the tetrahedral unit are identified at 790, 1010, 1150 cm −1 . 14,24,[30][31][32][35][36][37][38][39][40][41][42] The new peak at 1210 cm −1 indicates the characteristic of C-O; this also suggests an interaction between acetone and dPPV, as shown in Fig. 14,24,30-32 During the acetone exposure, the new peaks at 3420, 1734, and 1210 cm −1 can be assigned to the interaction between the carbonyl group of acetone molecule with 80CuNaY and the cation in the zeolite framework, as shown in Fig.…”

“…14,24,[30][31][32] During the acetone exposure, the new peaks at 3449 and 1377 cm −1 appear as the characteristic of Si-O-C, suggesting an interaction between acetone and 80CuNaY. 14,24,[30][31][32][35][36][37][38][39][40][41][42] The new peak at 1210 cm −1 indicates the characteristic of C-O; this also suggests an interaction between acetone and dPPV, as shown in Fig. 7b.…”

“…7a (see later). 14,24,[30][31][32][35][36][37][38][39][40][41][42] After the acetone exposure, the IR spectrum peaks at 3420 and 1210 cm −1 evidently decrease; this confirms that the interaction between 80CuNaY and acetone vapor is not reversible. Figure 6 shows the FTIR spectrum of dPPV [90]80CuNaY.…”