posted on 2024-04-23, 14:15authored byTong Hao, Lihong Wei, Jinyuan Jiang, Qian Zhou, Hui Liu
Biomass
reburning is an efficient and low-cost way to control nitric
oxide (NO), and the abundant potassium (K) element in biomass affects
the heterogeneous reaction between NO and biochar. Due to the incomplete
simulation of the NO heterogeneous reduction reaction pathway at the
molecular level and the unclear catalytic effect of K element in biochar,
further research is needed on the possible next reaction and the influencing
mechanism of the element. After the products of the existing reaction
pathways are referenced, two reasonably simplified biochar structural
models are selected as the basic reactants to study the microscopic
mechanism for further NO heterogeneous reduction on the biochar surface
before and after doping with the K atom based on density functional
theory. In studying the two further NO heterogeneous reduction reaction
pathways, we find that the carbon monoxide (CO) molecule fragment
protrudes from the surface of biochar models with the desorption of
N2 at the TS4 transition state, and the two edge types
of biochar product models obtained by simulation calculation are Klein
edge and ac56 edge observed in the experiment. In studying the catalytic
effect of potassium in biochar, we find that the presence of K increases
the heat release of adsorption of NO molecules, reduces the energy
barrier of the rate-determining step in the nitrogen (N2) generation and desorption process (by 50.88 and 69.97%), and hinders
the CO molecule from desorbing from the biochar model surface. Thermodynamic
and kinetic analyses also confirm its influence. The study proves
that the heterogeneous reduction reaction of four NO molecules on
the surface of biochar completes the whole reaction process and provides
a basic theoretical basis for the emission of nitrogen oxides (NOx) during biomass reburning.