氮气吸脱附实验VIP免费

氮气等温吸脱附实验原理以及应用WenChao2011.9.29BET单位重量催化剂的表面积，以m2g-1表示①固体表面是均匀的②吸附分子间无相互作用力③当p=p0时吸附层厚度趋于无穷大④吸附平衡时，每一层的蒸发速度等于其凝聚速度•V是在压力为p时的平衡吸附量•Vm是单层覆盖时的吸附量•c>20，气体在固体表面的吸附热与冷凝热的差值较大，说明气体与固体表面相互作用强•c~1，气体在固体表面的吸附热与冷凝热的差值较小，说明气体与固体表面相互作用弱把边长为1cm的立方体逐渐分割成小立方体的情况：可见达到nm级的超细微粒具有巨大的比表面积，因而具有许多独特的表面效应，成为新材料和多相催化方面的研究热点。用BET法测定固体比表面，最常用的吸附质是氮化点77.2K附近。低温可以避免化学吸附的发生。将相对压力控制在0.05～0.25之间，是因为当相对压力低于0.05时，不易建立多层吸附平衡；高于0.25时，容易发生毛细管凝聚作用。毛细凝聚现象孔=毛细管；孔中的吸附=毛细凝聚Kelvin公式：ln(p/p0)=-(2Vcos)/rRT表面张力，V液体摩尔体积，r半径，接触角接触角,0-90o,浸润,凹月面状接触角,90-180o,不浸润,凸月面状吸附气体都能浸润吸附剂固体,发生毛细凝聚浸润,接触角0-90o,cos>0,ln(p/p0)<0，p50nm);中孔(2-50nm);微孔(<2nm)孔分布曲线：(吸附总量-孔径)微分量-半径(dV/dr-r)最可几孔径：比例最大的孔BJH模型（Barrett-Joiner-Halenda）假定吸附层厚度t只与相对压力有关而与孔半径无关滞后现象hysteresis:吸附曲线和脱附曲线不重合Two-DimensionalHexagonally-OrderedMesoporousCarbonNitrideswithTunablePoreDiameter,SurfaceAreaandNitrogenContentAdv.Funct.Mater.2008,18,816–827Adv.Funct.Mater.2008,18,816–827Adv.Funct.Mater.2008,18,816–827Circles:MCN-1-100,squares:MCN-1-130,andtriangles:MCN-1-150J.Phys.Chem.C,201，114,9353ProbingAdsorption,PoreCondensation,andHysteresisBehaviorofPureFluidsinThree-DimensionalCubicMesoporousKIT-6Silica(a)Nitrogensorptionisotherms(at77.4K)inselectedKIT-6samples(agedatvaryingtemperaturesfrom50to130°C).(b)NLDFTporesizedistributions(calculatedfromthedesorptionbranch)fromnitrogen(77.4K)andargon(87.3K)forselectedKIT-6samplesagedatvarioustemperatures.TheNLDFTporesizes(equilibrium)are5.5,7.3,8.4,and10.1nm,for50,80,100,and130°C,respectively.J.Phys.Chem.C,201，114,9353KIT-6-130J.Phys.Chem.C,201，114,9353risetotypeH2hysteresisduetoporeblocking/percolationindependentporemodeldelayedcondensationJ.Phys.Chem.C,201，114,9353J.Phys.Chem.C,201，114,9353Comparativeplotrepresentingthepressuresobservedforcapillaryporecondensation(ads.)andevaporation(des.)inthecasesofhexagonalmesoporoussilica(MCM-41,SBA-15)materialsandtherespective3-Dcubicmesoporoussilica(MCM-48,KIT-6)materials,asafunctionofmesoporesize.Thethreedifferenthysteresisregimeregionsareindicated.J.Phys.Chem.C,201，114,9353J.Phys.Chem.C,201，114,9353Simplifiedschemesrepresentingporecondensationandhysteresis(typeH1)behaviorinsingleporesystemsandorderedporenetworks:(a)trueindependentcylindricalporesystem(e.g.,MCM-41-type);(b)interconnectedcylindricalchannels,withbridgesoftoosmallsizestoinfluencehysteresisbehavior(standardSBA-15conditions,e.g.,agingtemperature<100°C,accordingtoref3);and©fullyinterconnected3-Dnetworkofchannels(MCM-48/KIT-6-typeand3-D-likeSBA-15).Thankyou!