关键词: 丙氨酸, 密度泛函理论, 高温热解, NOX前驱体

Abstract: Alanine was selected as a nitrogen-containing model to research the conversion mechanism of nitrogen-containing gas, the quantum chemical simulation calculation was carried out by using density functional theory (DFT) methods at B3LYP/6-31+G(d, p) level. Three initial reaction paths and one secondary reaction path were designed. Geometric optimization and frequency calculation were used in reactants, transition states, intermediates, and products in each reaction path. The standard kinetic parameters in each reaction pathway were calculated and the formation and evolution mechanism of main pyrolysis products were analyzed. The thermogravimetric and Fourier transformer technology (TG?FT-IR) technique was used to identify the released gas during the nitrogen-containing gas pyrolysis process, to verify the simulation results. The experimental and simulation results showed that the initial reaction was that two alanine molecules dehydrated by a condensation reaction to form a propylene?propylene dipeptide, and then the propylene?propylene dipeptide formed diketopiperazine (DKP) by condensation reaction. This path had the smallest enthalpy change value and the minimum activation energy required for its reaction as the main reaction, and the secondary reaction path of path 1 was the cleavage of DKP. During the pyrolysis of alanine, there were mainly three kinds of nitrogen-containing products HCN, NH3 and HNCO. The nitrogen-containing gas products detected in the experiment were consistent with the products obtained by the simulated route. The alanine pyrolysis interval range was 250~330℃. At 290℃, the yield of NH3 was higher than that of HCN, and the yield of HNCO was the lowest. At 400~450℃, the amount of HCN was increased. Nitrogen-containing products were mainly NH3 and HCN. The above analysis was consistent with previous experimental results and analysis.

Key words: alanine, density functional theory, high temperature pyrolysis, NOX precursor