Theoretical and mechanistic studies of toxic gas removals over the nanomaterial catalysts

TitleTheoretical and mechanistic studies of toxic gas removals over the nanomaterial catalysts
Publication Typeวิทยานิพนธ์/Thesis
Year of Publication2020
AuthorsTanabat Mudchimo
DegreeDoctor of Philosophy -- Major in Chemistry
InstitutionFaculty of Science, Ubon Rachathani University
CityUbon Rachathani
Call NumberTD T161 2020
KeywordsAsphyxiating and poisonous, Carbon monoxide, Catalysts, CBNs, DFT, Gases, Hydrogen sulfide, Nanostructured materials, TM-ZSM-12, toxic gas removal

Among the major environmental issues most urgently requiring attention today are the emissions of toxic gases from the combustion of fuel from vehicles and other industrial processes. For this research, density functional theory (DFT) calculations were used to investigate catalytic nanomaterials for the removal of toxic gases. This research consisted of three approaches: (i) Removal of H2S to produce hydrogen in the presence of CO on transition metal-doped ZSM-12 (TM-ZSM-12) catalysts, (ii) the No removal and (iii) the CO removal by carbon-doped boron nitride (CxBNs) catalysts.
Hydrogen sulfide (H2S) leads to the corrosion and corruption of many catalysts. However, H2S is an inexhaustible potential source of the valuable chemical reagent hydrogen, which is also a very environmentally friendly energy product. In this first approach, we intensively focused on removal of H2S and producing hydrogen gas (H2) using catalysts, following equation: H2S(g)+CO(g)-->COS(g)+H2(g). Result calculations show that among other TM-ZSM-12 cluster, the Cu-ZSM-12 cluster has a potential application as a highly active catalyst for H2S removal together with hydrogen production. We found that COS desorption is the rate-determining step of this H2S removal process with a desorption energy of +1.18 eV. Moreover, incomplete combustion products such as nitrogen oxide (NO) and carbon monoxide (CO) are gases toxic to the environment and human health, due to their many devastating effects on the atmosphere and human health. In the second study, an NO reduction mechanism using carbon-doped boron nitride nanosheets (CxBNs) as a metal-free catalyst was applied. The results showed that the trans-(NO)2 structure of CNBNs is a potentially crucial intermediate and thermodynamically and kinetically favorable. The most energetically favorable pathway was +0.62 eV determined by calculation determined rates. Results suggest that CNBNs can be highly active metal-free materials for NO removal, which will transform NO into environmentally friendly gases. Additionally, in the third study, conversion of CO to carbon dioxide (CO2) using carbon-doped boron nitride nanosheets (CxBNs where X-1-3) as a metal-free catalyst were studied. The C3BBNs shows the highest efficiency for CO oxidation reaction with the lowest energy barrier at the determining a rate step of +0.28 eV. Additionally, the kinetic predictions on the reaction rate constant suggest that C3BBNs is the most effective for catalyzing CO into CO2 molecules with the fastest rate compared to other CxBNs surfaces.
Our intended outcome is that these results might enable to the aid future experiments to improve methods for creating the novel promising catalytic nanomaterials for toxic gas removal with desirable high efficiency in the near future.

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