The Catalytic Fast Pyrolysis Of Cellulose Intermediates On HZSM-5 Catalytic Pyrolysis Via Quantum Dynamics Study

The massive consumption of petroleum and the increasingly environment deterioration has led to an increased focus on and development of renewable energy.Biomass,as the only renewable carbon source on Earth,has emerged as a promising feedstock for the production of sustainable liquid fuels as a replacement for fossil energy sources.Catalytic pyrolysis,which can upgrade the quality of bio-oil,is considered an effective means of converting biomass.Zeolite molecular sieve catalysts have been widely utilized in catalytic conversion of biological oils due to their unique characteristics such as shape selectivity,acidity and thermal stability.However,the complete reaction mechanism of zeolite catalytic pyrolysis is still undefined,which limits the full potential of the zeolite catalyst in catalysis.This study employed a quantum dynamics method to investigate the aromatization reaction mechanism of furan and ethylene under the catalysis of HZSM-5 catalysts with multiple acidic sites,while taking into account the framework flexibility at 873 K.The simulation results show that the first step in the reaction between furan and ethylene in the HZSM-5 cavity is the Diels-Alder reaction,followed by the dehydrating reaction that leads to the formation of benzene.During the reaction,the two acidic sites of HZSM-5 catalyst were sequentially involved,and the acidic proton was observed to transfer between two adjacent acidic sites,with an average distance of 2.712 ?,which increased the probability of reaction.Secondly,the geometric and energy analysis was conducted on the reaction sy stem,revealing that the primary factor affecting the overall system fluctuation is the fluctuation of reactants.Although the HZSM-5 framework almost fluctuated at the equilibrium position,it exhibited highenergy vibration state at 873 K.Thus,the energy barrier of the aromatization reaction was low when the influence of framework fluctuation was eliminated.This is because the reactions in quantum dynamics take place when organic molecules are in a metastable state.which is more consistent with the actual dynamics that occur at high temperature environment.To investigate whether the transfer of acidic protons is affected by reactants,a model was developed by deleting acidic protons at adjacent acidic sites(average distance 2.712 ?)and at distant acidic sites(average distance 7.601 ?)based on the HZSM-5 model without reactants.The findings suggest that the transfer of acidic protons between adjacent acidic sites within the zeolite framework was not influenced by the presence of reactants,which can increase the likelihood of catalytic reactions and hold significant importance in enhancing the catalytic activity.Acidic sites within the system exhibit dynamic behavior due to the continual exchange of acidic protons.This work employed the neural network model to forecast the distribution of acid sites and predict energy by utilizing the atomic coordinates of diverse acid sites,and combined with the feature importance screening to identify the key factors affecting energy,overcoming the disadvantages of the long calculation time based on first-principles calculations.The findings demonstrate a high degree of concordance between the projections of the neural network model and the results of first-principles calculations.It is of great significance to rapidly and accurately predict the material properties of zeolite and other materials with complex and diverse active sites distributions in nature.