Mesoporous Mn-based Sorbents Prepared By Regulation Of Composite Oxides And Investigation On Desulfurization Mechanism

China is a country with more coal and less oil,and the way of the energy consumption of China will not be changed for a long time.However,the direct combustion of coal will release a large number of pollutants,which will pollute seriously the environment.Recently,severe haze occurs frequently in China.In this context,efficient and clean use of coal is an inevitable trend.So far,using coal to manufacture synthesis gas,methane gas and chemical products or using coal as fuel in combined cycle?IGCC?is effective means for the utilization of coal resource.Unfortunately,most sulfur is converted to H₂S during the coal gasification process.Since H₂S will damage downstream equipment and pollute the environment,H₂S contained in hot coal gas needed to be removed prior to its use.Pure metal oxides as sorbents are confronted with serious scientific problems,such as sintering,mechanical strength and low utilization ratio of active components during the hot coal gas desulphurization.In order to overcome the above shortcomings,the mesoporous silica with high specific surface area and cheap raw materials are selected as supports.A series of Mn-based sorbents with high sulfur capacity,high utilization and regeneration capacity are prepared and the desulfurization performance and mechanism of sulfidation-regeneration are studied in detail.The following results have been obtained in this dissertation:1.In order to reduce the cost of sorbent,mesoporous FSM-16 was used as a support,Fe-Mn-O was the active phase,MoO₃ was the doping phase and the high sulfur capacity Mn-Fe-Mo/FSM-16 sorbent was prepared.After multiple sulfidation-regeneration cycles,90%of the initial sulfur capacity was maintained.A large amount of elemental sulfur was produced instead of sulfur dioxide?SO₂?by a simple regeneration.Moreover,the mechanism of sulfidation-regeneration was confirmed in situ using highly sensitive time-of-flight mass-spectrometry?TOF-MS?for the first time.2.In coal gasification,the raw gas usually contained partial steam,which would affect the desulfurization performance of sorbent.In order to improve the water resistance of sorbent,a series of x MnyCa/MSU-H sorbents with various Mn/Ca molar ratio were first designed and synthesized with a sol-gel method.90Mn10Ca/MSU-H exhibited better desulfurization performance at 750 ^oC with a breakthrough sulfur capacity?BSC?of 18.69 g S/100 g sorbent and good regeneration ability.The introduction of Ca species effectively promoted the dispersion of active constituents and enhanced the sorption of H₂O,which improved the desulfurization activity and H₂O-resistance ability.3.A series of new La-Mn sorbents supported on ordered mesoporous Al₂O₃-CaO?OMA-2Ca?with various Mn/La molar ratio were first designed and synthesized for removal of H₂S at 700-850 ^oC.A large amount of elemental sulfur?S and S₈?was formed during desulfurization as a result of synergistic catalysis of?-Al₂O₃ and lanthanum oxysulfide at high temperature.After five sulfidation-regeneration cycles,high BSC?about 90%of the initial BSC?was maintained and the mesostructure of sorbent remained intact except that the amorphous wall was converted to?-Al₂O₃phase.The existence of high content steam in hot coal gas obviously reduced the sulfur capacity because of the formation of MnAl₂O₄.