Study On The Inhibition Of Co On COS Formation In Desulfurization Process By ZnO/SiO₂ Sorbent

The clean and efficient utilization of coal is the only way to promote the rational use of energy in China.Owing to the sulfur-containing characteristics of coal itself,industrial raw gas from coal gasification contains sulfides,of which more than 90%is H₂S,which corrodes equipment and pollutes the environment.Therefore,desulfurization of coal-based industrial gas is of great significance.At present,the desulfurization of syngas has received extensive attention.One of the key technologies is the desulfurization of metal oxides at medium temperature.ZnO sorbent has been extensively studied among fine desulfurizer.It was found that the COS present in outlet during the H₂S removal under complex atmosphere of the single metal zinc oxide sorbent.COS is more difficult to remove than H₂S,which will reduce the desulfurization performance of the sorbent.The modification by cobalt addition improves the desulfurization performance and the ability to remove COS of the zinc-based sorbent significantly,which made it necessary to probe the improvement mechanism due to Co addition and to optimize the performance of the composite metal oxides sorbent.In this paper,zinc-cobalt based sorbent was prepared by impregnation method with silica as the support,zinc nitrate and cobalt nitrate as the active component precursors.The effect of impregnation method,active component content and temperature on the desulfurization performance of sorbent was investigated.The influence mechanism of Co addition on the COS inhibition in the desulfurization process of the sorbent was investigated by H₂S-containing atmosphere modulation and transient experiment.Then the influence of atmospheric and active component morphology on removal of COS was investigated by modulating COS-containing atmosphere.To further explain the interaction mechanism between the active components of Zn and Co,the physicochemical properties of the sorbent characterized by XRD,BET,SEM and other characterization methods were correlated with the desulfurization performance.The main conclusions were listed as follows:1)Comparing the desulfurization performance of sorbent prepared by high-pressure impregnation,equal volume impregnation,equal volume ultrasonic impregnation and excessive ultrasonic impregnation,it was concluded that the excessive ultrasonic impregnation was the best impregnation method,which could increase the dispersibility of the active component.The breakthrough capacity and time of the sorbent were increased due to addition of Co,and the Zn-Co/SiO₂ sorbent had better desulfurization performance when Zn/Co ratio was 36:10.There existed synergistic effect between the two active components of Zn and Co.The addition of Co had inhibitory effect on the production of COS,which weakened the competitive adsorption of H₂S and COS on the active site of the ZnO sorbent,then it could promote the removal of H₂S,thus it could improve the desulfurization performance of the ZnO sorbent.2)The desulfurization performance of Zn36Co0 and Zn36Co10decreased as the reduced temperature.But Co could improve the desulfurization performance of ZnO sorbent at low temperature and inhibit the formation of COS.3)The addition of Co promoted the chemical adsorption,hydrolysis and hydrogenolysis of COS for ZnO sorbent,but the chemical adsorption ang the hydrolysis of COS for ZnO sorbent was not obvious.The sorbent Zn36Co0 mainly played a role in the hydrolysis reaction of COS,ZnS had a strong catalytic effect on COS hydrolysis.The sorbent Zn0Co10and Zn36Co10 mainly played a role in the hydrogenolysis reaction of COS,and Co₉S₈ had a strong catalytic effect on COS hydrogenolysis.The addition of Co changed the way to remove COS of zinc-based sorbent.