Deactivation mechanism of sodium poisoning hydrodesulfurization catalyst
The hydrosulfurization catalyst deactivation by sodium poisoning was studied by element analysis,pore property and acid property characterization and it was confirmed that the significant reduction of acid content was responsible for the poisoning,rather than carbon deposition or impurities blocking the pore.XRD,H2-TPR and hydrodesulfurization activity characterization confirmed that sodium poisoning strengthened the aggregation of MoO3,increased the reduction temperature of active metal,and decreased the hydrodesulfurization activity.The catalyst deactivation mechanism was that the macro-molecular sulfides with substituent aromatic rings could not be removed by direct desulfurization,and must be saturated by hydrogenation of the aromatic rings before desulfurization.The reduction of acid content of sodium poisoning catalyst reduced the hydrogenation capacity,resulting in the deactivation of the catalyst.Meanwhile,SEM-EDS analysis confirmed that Na impurities were evenly distributed along the radial direction of the catalyst,and the catalyst had no obvious adsorption to Na impurities.Therefore,even a small amount of Na impurities could penetrate the entire catalyst bed,leading to a significant reduction in the operating run-time of the industrial unit.
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