In order to better understand the mechanism of NO_(x)and N_(2)Oprecursors(NH_(3)and HCN)from aspartic acid(Asp)pyrolysis,decomposition reaction networks resulting in the generation of NH_(3)and HCN were investigated by employing density function theory methods.After several pathways were analyzed in detail,two series of pyrolytic reactions containing three possible pathways were proposed.All the reactants,transition states,intermediates and products were optimized,also the electronic properties on these crucial points were discussed,which shows that Cαacts as the most active site to initiate the pyrolysis reaction,where the direct Cα-Cβbond breakage,due to the atomic charge population of repulsion,led to one key route for the generation of HCN,and the transfer of Hαfrom Cαto Cβresulting in another key route for the generation of HCN,while the transfer of Hαfrom Cαto N atom of Asp resulting in the key route for the generation of HN3.Further,the kinetic analysis based on speed control method in each key reaction pathway was conducted to further compare the generation of HCN and NH_(3)under various temperatures.The above results are in accordance with the related experimental results.
Kang PengQin WuFu ZongqiangWang TipengJu LiweiTan Zhongfu
Pretreatment mechanism ofβ-O-4 lignin(Lβ-O-4)during the phosphoric acid-acetone process involves a series of interactions between lignin and solvent molecule(H2O,CH3COCH3 and H3PO4)which lead to the adsorption,solubility and decomposition of lignin.Coniferyl alcohol guaiacyl glycerol(CAGG)with the predominant linkage(β-O-4 ether bond)was chosen as the modelβ-O-4 lignin(Lβ-O-4)for investigating the detailed pretreatment mechanism based on density functional theory calculations and molecular dynamic simulations.Interactions betweenβ-O-4 lignin and solvent molecules were firstly detected.Only physical interaction occurred betweenβ-O-4 lignin and the solvent molecule.The attractive van der Waals interaction favored CH3COCH3 molecules approaching to Lβ-O-4,showing a compatibility of Lβ-O-4 in CH3COCH3 solution.Furthermore,following the temperature effect on the dynamics processes,larger dynamics calculations and experiments were carried out to reveal the detailed dissolution and precipitation ofβ-O-4 lignin in various solutions.
