| The catalytic conversion of cellulose is currently among the most efficient methods of developing and utilizing this valuable resource.A novel approach to cellulose utilization that has garnered considerable attention is liquid membrane catalytic conversion.The process of liquid membrane catalytic conversion of cellulose involves a complex interplay of physical and chemical phenomena.A thorough understanding of the coupling mechanism among these processes is essential for achieving efficient utilization of liquid membrane catalysis of cellulose.Unfortunately,the synergistic mechanism of liquid membrane formation,phase interface mass transfer,and chemical reaction remains unclear,thereby hindering the efficient utilization of this system.Despite ongoing research efforts in catalyst development,reaction system screening,and reaction pathway optimization,systematic investigation of the coupling mechanism of multi-physicochemical processes and the mass transfer process through liquid membranes remains limited.Furthermore,direct microscopic observation of catalytic liquid membrane reactions is nearly impossible,and experimental research methods are constrained.In order to bridge this gap,numerical simulation techniques can serve as an efficacious complement to experimental research tools,offering further insight into the synergistic interplay between reaction and mass transfer during the catalytic conversion of cellulose liquid membranes.Addressing the aforementioned challenges,this paper examines the liquid membrane catalytic conversion reaction system of cellulose,and constructs a numerical model using the Lattice Boltzmann method(LBM)coupled with multiphysicochemical processes within the framework of the lattice Boltzmann algorithm.The study investigates the mechanism behind the formation of the liquid membrane on the surface of cellulose particles in multiphase reaction flows,and reveals the dynamic evolution of the liquid membrane during the reaction process.Through a numerical simulation study of the coupling effect between multi-physicochemical processes and multiphase multicomponent transport in the catalytic conversion of cellulose liquid membrane and its influence on the reaction system,the synergistic mechanism of mass transfer and reaction processes within the liquid membrane is elucidated.The main research content and conclusions are presented as follows:(1)To overcome the bottleneck that hinders the efficient utilization of cellulose in the liquid membrane catalytic transformation reaction system,it is necessary to explore in depth the mechanism of liquid membrane formation on the surface of cellulose particles,providing a theoretical basis for the establishment of cellulose liquid membrane catalytic conversion models and proposing new ideas for the efficient utilization of liquid membrane catalytic transformation reaction systems for cellulose.In this paper,a multiphase cellulose particle surface liquid membrane adsorption model was developed based on the Lattice Boltzmann Method(LBM)framework and the contact angle theory was introduced.The dynamic adsorption process of the liquid membrane on the surface of cellulose particles was reproduced,and the influence of the initial density,liquid to gas density ratio and wetting properties of the particle surface material on the morphology of the liquid membrane was discovered.This research clarified the multiple regulatory mechanisms of the hydrophilicity/hydrophobicity of the particle surface,initial density(ρc),and liquid to gas density ratio on the liquid membrane formation process and the initial liquid membrane thickness.The study showed that when the liquid to gas density ratio remained unchanged and the contact angle(θ)was in the range of(0°,110°),an increase in ρc resulted in an increase in the initial thickness of the liquid membrane and enhanced its stability.In this case,any pc within the density range of(0.260,0.766)can allow the formation of a liquid membrane on the surface of the particles.When θ is in the range of(110°,180°),the minimum initial density required for liquid membrane formation increases with an increase in θ,while the maximum initial density exhibits a trend of first increasing and then decreasing.(2)To delve deeper into the synergistic mechanisms of interfacial mass transfer and chemical reaction in the closed system of cellulose to 5-hydroxymethylfurfural(HMF)conversion via liquid membrane catalysis,this study developed a novel catalytic model for single particle liquid membrane in the organic phase,based on the dynamic adsorption model of cellulose particles’ liquid membrane established in the previous section.In order to address the interfacial mass transfer process in the closed system,the study employed a correction factor for interfacial concentration,allowing for the selective separation of products and overcoming the numerical instability inherent in complex interfacial flows.The study investigated the synergistic enhancement of liquid membrane mass transfer and chemical reaction in regulating the HMF yield,and revealed the underlying mechanism of the influence of initial liquid membrane thickness on the HMF yield.The sensitivity strength of the parameter Ωa,which characterizes the effect of initial liquid membrane thickness(ξ)on HMF yield,was defined and elucidated.The study found that when the glucose conversion rate is low,the HMF yield is positively correlated with ξ;when the glucose conversion rate is high,the HMF yield is negatively correlated with ξ.(3)To address the inadequacies of the single-particle model in the closed organicphase system that deviates from the actual reaction system by neglecting dynamic changes in the liquid membrane and inter-particle interactions,this paper presents a multi-particle cellulose model that builds upon the single-particle cellulose model catalyzed by the organic phase liquid membrane.Furthermore,the paper introduces the shrinking core theory to enable the real-time evolution of the dynamic liquid membrane during the reaction process.The synergistic mechanism of liquid membrane mass transfer and reaction process is explored,and the evolution mechanism of HMF yield as a function of reaction temperature is uncovered.The results showed that at lower temperatures,the HMF yield is more sensitive to temperature changes,while at higher reaction temperatures,the effect of temperature on HMF yield is relatively weakened.Prior to reaching the peak HMF yield,the HMF yield is positively correlated with the reaction temperature,whereas after reaching the peak,the HMF yield is negatively correlated with the reaction temperature.The study elucidates the influence of particle size on HMF yield,revealing that an increase in particle size will promote the average concentration of HMF but reduce the sensitivity of HMF yield to particle size at the same reaction time.Furthermore,an optimal particle size of 20 l.u is identified,which leads to the highest HMF yield and the peak sensitivity of HMF yield to particle size.(4)To tackle the problems arising from the widespread use of organic solvents in organic phase closed systems,which lead to environmental pollution and increased costs,and to offer theoretical guidance for the advancement of liquid membrane catalyzed cellulose reaction systems,this study develops a gas-liquid-solid multiphase liquid membrane catalyzed single particle cellulose model based on the liquid membrane adsorption model on the surface of cellulose particles.This model incorporates the interfacial concentration correction operator,the Carnahan-Starling(C-S)equation of state,the Volume of Pixel(VOP)method,and the phase transition boundary treatment strategy.Through a numerical simulation study of the coupling effect of multi-physicochemical processes and multiphase multicomponent transport in the open system of cellulose liquid membrane catalytic conversion and its impact on the reaction system,the study reveals the enhanced synergistic effect of liquid membrane mass transfer and catalytic conversion in the gas-liquid-solid system.Meanwhile,through exploration of the impacts of reaction temperature,cellulose particle size,initial liquid membrane thickness(δξ),and air flow rate on the reaction,an empirical equation for the equilibrium yield of HMF and initial liquid membrane thickness was established for the first time.Furthermore,a monotonic linear relationship between the equilibrium yield of HMF and initial liquid membrane thickness was elucidated. |
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