Other

Tsinghua University

Dezheng Wang

Fei Wang

Yao M Wang

Fei Wei

Jinfu Wang

An apparatus and method for measuring molecular diffusivity in porous powders or minerals, e.g., the microporous synthetic minerals used for gas separation and chemical catalysis, were invented that allows a varying pressure in the gas around the powder during the measurement. This obviates the need for the pressure to be constant and the attendant complicated component parts. A mass balance model equation of the sample cell with the diffusivity as an adjustable parameter is used to deduce the sample cell pressure change versus time (uptake curve) until the equilibration of gas diffusion into the powder. A numerical analysis method is used to solve the mathematical model to compute a simulated uptake curve. Curve fitting of the simulated and measured uptake curves is used to optimize the diffusivity parameter, which gives the measured diffusivity. The apparatus and method are simple, easy to use, and automation is also simple.

Method to measure a molecular diffusion coefficient in a porous powder

Apparatus and method to measure a molecular diffusion coefficient in a porous powder

An apparatus and method are disclosed for measuring the kinetic parameters of a catalyst powder, which include the reaction rate constants, active site concentration and intraparticle diffusivity. The measurement of the active site concentration selectively measures just the active sites and not the entire exposed atom concentration. The apparatus and method use surface concentrations less than 50% and larger than 1% the total active site concentration and a dynamic pulsed flow to avoid including weak adsorption sites not involved in the catalysis. The measurement is more accurate because (1) it uses a reactant gas and non-steady state adsorption at temperatures near to reaction temperatures, and (2) it uses the chemical kinetics expressions to extract the measured active site concentration to perform the measurement so as to count just those sites actually active for that reactant. This is better than the prior art methods that measure an entire surface atom concentration under non-dynamic conditions because the latter is not necessarily the same as the active site concentration in the chemical kinetics expression. The intraparticle diffusivity measured by the apparatus and method is the effective gas diffusivity in a porous powder, and this is useful as a characterization of the tortuosity of the porous powder.

Apparatus and method to measure the kinetics parameters of a porous powder catalyst

A method and apparatus for measuring the gas amounts adsorbed on a powder which directly measures pressure changes in a gas supply chamber with the use of differential pressure sensors between the gas supply chamber and a reference chamber which gas amount is maintained constant. Calculations of the gas amounts adsorbed are based on the pressure changes in a sample cell and the pressure changes in the gas supply chamber or a gas reference chamber. The method and apparatus of this invention measures the adsorption or desorption isotherm or gas uptake at constant pressure curve of a powder with, as compared with presently available measurement techniques, increased accuracy and resolution. The experimental data can be analyzed to obtain information on the surface area, pore size distribution, pore volume, pore structure and diffusion coefficient of the powder.

Growing community of inventors

Beijing, China

Dezheng Wang