Solubility study for the purification of hydrogen from high pressure hydrocracker off‐gas by an absorption‐stripping process

Abstract

Abstract Experiments were carried out to identify a solvent which has a high solubility and selectivity for methane relative to hydrogen at 295 K and pressures from 13.88 to 20.78 MPa. Binary solubilities with pure hydrogen and methane, and ternary solubilities with 73 mol% H 2 and 27 mol% CH 4 were measured at 295 K and for pressures from 6.99 to 20.78 MPa in various organic solvents. This gas mixture simulates hydrocracker and hydrotreater off‐gases which are candidates for purification with an absorption‐stripper. Of the solvents tested, 2,2,4‐trimethylpentane ( iso ‐octane), which showed very high methane solubility and a reasonable selectivity, and methylcyclohexane, which showed a very high selectivity and a reasonable solubility, are the best solvents for methane absorption. Correlations for hydrogen and methane as a function of pressure and solvent solubility parameter were developed with the experimental solubilities. Binary interaction parameters for Peng‐Robinson (Peng and Robinson, 1976) and Soave‐Redlich‐Kwong (Soave, 1972) equations of state were calculated with experimental solubility results. Prediction of gas solubility in a ternary system was compared with experimental and found to be satisfactory when experimental binary interaction parameters were used.