20087表征-1.pptVIP

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Surface area Table, Specific surface areas of catalysts Catalyst Application Sg (m2/g) REHY沸石 裂化 1000 活性碳 载体 500-1000 SiO2-Al2O3 裂化 200-500 CoMo/Al2O3 加氢精制 200-300 Ni/Al2O3 加氢 250 Fe-Al2O3-K2O 氨合成 10 V2O5 部分氧化 1 铂金网 氨氧化 0.01 Pore-size distribution Mercury porosimetry Some liquids wet solid very poorly, an example is mercury, which exhibits wetting angles,θin 112o-142o for most of the solids. Such a liquid penetrates pores only when forced by a pressure. Where S is the surface tension and r the pore radius. For mercury S=474 dynes/cm, ?=130o Pore-size distribution Table, Pressure necessary to fill pores pressure (atm) Pore radius（nm） 1 6?103 3.5?102 17.5 103 6 4?103 1.5 Pore-size distribution Pore-size distribution Nitrogen adsorption Nitrogen adsorption isotherms, when extended to p/p0 values approaching unity, include the region where condensation happens in the pores Kelvin equation Where S is the surface tension of liquid nitrogen, V the mole volume, ? the contact angle, R the gas constant, T the temperature, r the pore radius for condensation at p/p0. for nitrogen at -196 oC, r in nm is Pore-size distribution Pore-size distribution Pore-size distribution Diffusivity Measurement of diffusivity Measured diffusivity is often doubtful, because exact conditions of pressure, temperature, and concentration profiles in the pellet are impossible to duplicate By comparing the calculated and measured diffusivities in simple mixtures, it is possible to estimate the tortuosity factor Where Dcalc is the calculated value from rate-particle size curves, Dmeas is the measured value Diffusivity * * * * * * * * * * * * * * * * * * * * * TPR and TPS Temperature Programmed Reduction (TPR) characterization of oxide catalysts and other reducible catalysts qualitative information on oxidation state quantitative kinetic data optimization of catalyst pretreatment Temperature Programmed Sulphiding (TPS) si