Adsorption separation for high purity propane from liquefied petroleum gas in a fixed bed by removal of alkanes

The process for high purity propane production via adsorption separation of propane from liquefied petroleum gas (LPG) was investigated at ambient temperature and atmospheric pressure under dynamic conditions in a fixed bed. Breakthrough curves for LPG adsorption on 4A, 5A, 13X and NaY zeolite pellets and granular activated carbon were measured. The length of unused bed (LUB) values for isobutane and butane adsorption in fixed beds with different adsorbent samples were determined by analyzing breakthrough curves. Effects of bed height (5–10 cm) and flow rate (60–100 mL/min) on adsorption characteristics of propane, isobutane and butane onto activated carbon were also examined. Among all these five adsorbent samples, activated carbon exhibited the highest adsorption capacity and the best separation performance, and the concentration of propane in the outlet gas could reach as high as 99.7% (volume fraction). Besides, the LUB value of activated carbon fixed bed was the smallest, which indicated that activated carbon fixed bed was more suitable for adsorption separation of propane from LPG. Adsorption dynamics also showed that relatively lower flow rate and relatively longer bed length were favorable for removal of isobutane and butane from LPG. The Yoon–Nelson model provided a good fit to the experimental data and there was a nice agreement between the numerical simulations and the corresponding data obtained from experiments. All the correlation coefficients in fitted equations exceeded 0.98, indicating a good confidence level for the fit.