Direct measurements of volumetric gas storage capacity and some new insight into adsorbed natural gas storage

We present a unique bench scale apparatus for directly measuring volumetric gas storage capacities designed at UTRC. The apparatus construction avoids gas leakage, and the analysis of experimental data prevents leakage from i nflating capacity measurements. Deliverable methane storage capacities (V-d /V-s) of adsorbents are evaluated directly from experiments with this appar atus rather than calculated from gravimetric adsorption capacities. We sugg est that an adsorbent for methane storage should have an optimal pore volum e consisting of pores ranging from 8 to 15 Angstrom, rather than a monodisp ersed 8 Angstrom pore size distribution as calculated by recent computer si mulations. This interpretation is based on our modeling results and on the fact that physical activation usually produces an adsorbent with a polydisp erse distribution of pore size. In general, ultra-micropores (<7 Angstrom) should be avoided and super-micropores (7-20 Angstrom) should be developed during adsorbent preparation. Ultra-micropores collect "cushion gas," thus reducing deliverable storage capacity. Super-micropores offer high methane adsorption densities and fast adsorption/desorption kinetics.