Abstract
In the present study we propose a more promising catalyst for the deNOx process to eliminate harmful nitrogen oxides from the environment. The study was performed with a computer calculation using density functional theory (DFT) based on an ab initio method. Two zeolite catalysts, FAU and MFI, were selected with additional Cu–O–Zn bimetallic dimer adsorbed inside the pores of both zeolites. Based on the analysis of preliminary studies, the most probable way of co-adsorption of nitric oxide and ammonia was selected, which became the initial configuration for the reaction mechanism. Two types of mechanisms were proposed: with hydroxyl groups on a bridged position of the dimer or a hydroxyl group on one of the metal atoms of the dimer. Based on the results, it was determined that the FAU zeolite with a bimetallic dimer and an OH group on the zinc atom was the most efficient configuration with a relatively low energy barrier. The real advantage of the Cu–Zn system over FAU and MFI in hydrothermal conditions has been demonstrated in comparison to a conventional Cu–Cu catalyst.
Highlights
A current problem still related to industrialization is the excessive emission of nitrogen oxides (NOx) [1,2], which pose a serious threat to the environment as well as human health [3,4]
The MFI zeolite with an OH group on Cu showed the same adsorption mode; a partial Molecules 2021, 26, x FOR PEER REVIEdWecomposition of the ammonia molecule had already occurred in the first step, an4dofo1n1e of the hydrogen atoms detached from the ammonia and adsorbed onto the nitric oxide oxygen, which formed a bond with the copper in the dimer
A catalyst with a dimer deposited on the FAU zeolite was promising (Figure 6a) as the energy barrier of the transformation stage of the system was very low, so the deNOx process could proceed without additional expenditure related to the temperature increase
Summary
A current problem still related to industrialization is the excessive emission of nitrogen oxides (NOx) [1,2], which pose a serious threat to the environment as well as human health [3,4]. The MFI zeolite with an OH group on Cu showed the same adsorption mode; a partial Molecules 2021, 26, x FOR PEER REVIEdWecomposition of the ammonia molecule had already occurred in the first step, an4dofo1n1e of the hydrogen atoms detached from the ammonia and adsorbed onto the nitric oxide oxygen, which formed a bond with the copper in the dimer.
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