A reference high-pressure CO₂ adsorption isotherm for ammonium ZSM-5 zeolite: results of an interlaboratory study.

ABSTRACT: This paper reports the results of an international interlaboratory study led by the National Institute of Standards and Technology (NIST) on the measurement of high-pressure surface excess carbon dioxide adsorption isotherms on NIST Reference Material RM 8852 (ammonium ZSM-5 zeolite), at 293.15 K (20 °C) from 1 kPa up to 4.5 MPa. Eleven laboratories participated in this exercise and, for the first time, high-pressure adsorption reference data are reported using a reference material. An empirical reference equation n e x = d ( 1 + exp [ - ln ( P ) + a / b ] ) c , [n _ex -surface excess uptake (mmol/g), P-equilibrium pressure (MPa), a?=?-6.22, b?=?1.97, c?=?4.73, and d?=?3.87] along with the 95% uncertainty interval (U _k?=?2?=?0.075 mmol/g) were determined for the reference isotherm using a Bayesian, Markov Chain Monte Carlo method. Together, this zeolitic reference material and the associated adsorption data provide a means for laboratories to test and validate high-pressure adsorption equipment and measurements. Recommendations are provided for measuring reliable high-pressure adsorption isotherms using this material, including activation procedures, data processing methods to determine surface excess uptake, and the appropriate equation of state to be used.

SUBMITTER: Nguyen HGT 

PROVIDER: S-EPMC6417222 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature