Study On Deactivation Of Adsorbent For Separation And Purification Of Off-gas In Acetic Acid Production By Pressure Swing Adsorption

The tail gas from carbonylation of methanol to acetic acid process contains60%-85%carbon monoxide, which not only pollutes the environment, but also causes some waste of resources. Therefore, the recovery of CO with pressure swing adsorption method is significant. The deactivation phenomenon of5A molecular sieve adsorbent was studied on the BET adsorption apparatus with static method. The effects of methanol, water and acetic acid on the activity of adsorbent were examined, and the corresponding deactivation model was established. This provides a theoretical basis and guiding significance for the design and operation of process.The result showed that the maximum relative deviation of adsorption capacity measured by experimental apparatus was0.04%under the constant temperature of25℃and the adsorption pressure ranging from0to75kPa. The adsorption isotherms of5A molecular sieve for CO2could well meet the BET adsorption isotherm equation, and the saturation adsorption capacity respectively was3.681mol/kg and3.865mol/kg. Through studying the effect of the impurity on the activity of adsorbent, the following summarized the optimum conditions:the activation temperature of5A molecular sieves was350℃, regeneration times, temperature and time of adsorbent was respectively60min,300℃and4times. When the concentration of residual impurity ranged from0to2%, adsorption isotherms of adsorbent with impurity for CO2were also satisfied BET adsorption isotherm equation. The activity of adsorbent decreased linearly with the amount of residual, and the degree of influence on the activity of the adsorbent in descending order were water, acetic acid and methanol. Besides, the parameters a and b of adsorbent increased linearly with the amount of residual, and the parameter of adsorbent with water were greater than that of adsorbent with methanol.Under the system of residual methanol-water two components impurities, the maximum relative deviation between the adsorption data of5A molecular sieve for CO2and model value was0.86%, and the model was consistent well with experimental result.