Drying kinetics for alcohol-soaked type-A zeolite(pore size 0.5 nm)was determined at 50°C for 12 small-molecule alcohols(from C1 to C10).The second-phase of drying of wet porous materials reports on the mass-tran...Drying kinetics for alcohol-soaked type-A zeolite(pore size 0.5 nm)was determined at 50°C for 12 small-molecule alcohols(from C1 to C10).The second-phase of drying of wet porous materials reports on the mass-transfer characteristics within the solid matrices.This stage follows pseudo first-order kinetics(k1),and the second-order rate constant k2=k1/(fluxional area)was found to correlate with the surface tension of the liquids imbibing the solid matrix(p<0.002).k2 values decrease along the homologous linear alcohols,and branched-chain alcohols diffuse faster than their linear analogues due to their lower surface tensions.No independent contribution was found from the molecular size of the alcohols in the experiment reported here.Characteristic velocity and enthalpy of vaporisation of the liquids were not found to be significant independent variables,either.The find agrees with the notion that liquid movement in pores is governed during the drying processes by the liquid chemical potential gradient between the pore space and gas phase above the porous particle surfaces,this gradient being a function of the molecular cohesion of the moving liquid front(surface tension,g).The results can be expressed by the linear Gibbs-energy relation log(k2/s^(-1)·m^(-2))=(2.5±0.5)-(1.6±0.2)×10^(2)(g/J·m^(-2)).展开更多
文摘Drying kinetics for alcohol-soaked type-A zeolite(pore size 0.5 nm)was determined at 50°C for 12 small-molecule alcohols(from C1 to C10).The second-phase of drying of wet porous materials reports on the mass-transfer characteristics within the solid matrices.This stage follows pseudo first-order kinetics(k1),and the second-order rate constant k2=k1/(fluxional area)was found to correlate with the surface tension of the liquids imbibing the solid matrix(p<0.002).k2 values decrease along the homologous linear alcohols,and branched-chain alcohols diffuse faster than their linear analogues due to their lower surface tensions.No independent contribution was found from the molecular size of the alcohols in the experiment reported here.Characteristic velocity and enthalpy of vaporisation of the liquids were not found to be significant independent variables,either.The find agrees with the notion that liquid movement in pores is governed during the drying processes by the liquid chemical potential gradient between the pore space and gas phase above the porous particle surfaces,this gradient being a function of the molecular cohesion of the moving liquid front(surface tension,g).The results can be expressed by the linear Gibbs-energy relation log(k2/s^(-1)·m^(-2))=(2.5±0.5)-(1.6±0.2)×10^(2)(g/J·m^(-2)).
