Influences Of Acid And Metal Modification On Desulfurization Performance Of Y Zeolite For Thiophene In Coke Oven Gas

The coking industry is well developed in China,and the production of coke oven gas is high.The preparation of methane from coke oven gas is one of the most important ways for its effective utilization.However,the presence of ppmv thiophene could poison the catalyst used for methane production.Thus,it is necessary to deeply remove thiophene below 0.1 ppmv.At present,the hydrodesulfurization technology has been widely used to remove the thiophene from coke oven gas.However,when the thiophene concentration is low to ppm level,its deep removal is a big challenge.Among the various desulfurization methods,adsorption method has the advantages of high desulfurization accuracy for thiophene.The key for it is the preparation of sorbent.Researches have shown that the metal or acid modified Y zeolite has excellent desulfurization performance in liquid at mild temperature,but the desulfurization behaviors in coke oven gas with complex atmosphere at higher temperature still need to be further investigated.In this thesis,a series of Y zeolite based sorbents with different types and strengthes of acids,and different metal irons were prepared,and their desulfurization performences in simulated coke oven gas were studied,and the main conclusions are listed as follows:?1?NaY zeolite was modified by different concentrations of ammonium nitrate and citric acid solutions.The prepared sorbents were characterized by XRD,N₂ adsorption,Py-FTIR and ICP,and their desulfurization performences in simulated coke oven gas were studied in fixed-bed.The results showed that ammonium nitrate and citric acid solution with high concentration would lead to imperfection of crystal structure,resulting in the decrease of desulfurization performance.The increase of weak acid on sorbent is conducive to the adsorption of thiophene,the increase of medium-strong acid could cause the production of thiophene polymers,which could cover the acid sites and block the pore channel,resulting in the decrease of desulfurization efficiency.When desulfurization temperature was 100°C,the adsorption capacity of HY-0.1C₅₅₀sorbent was the highest,reaching 71.31 mg/g.?2?NaY was modified by liquid phase ion exchanging method to prepare CeY₅₅₀,NiY₅₅₀,AgY₅₅₀ and ZnY₅₅₀ sorbents.The desulfurization activities and mechanisms of sorbents were investigated.The results showed that when the desulfurization temperature was 100°C,the sequence of adsorption capacity of metal modification sorbents was as follows:AgY₅₅₀>ZnY₅₅₀>NiY₅₅₀>CeY₅₅₀.AgY₅₅₀ sorbent has the highest adsorption capacity for thiophene,reaching143.71 mg/g.The desulfurization performance was affected by the interaction mode between metal elements and thiophene,the presence of?-complexation could improve the adsorption capacity for thiophene.In the preparation process of metal modified sorbents,the upload content of metal ion of sorbents was consistent with its adsorption capacity for thiophene.When the desulfurization temperature increased from 100°C to 200°C,thiophene adsorbed by?-complextion interaction mode was easy to desorb,and thiophene adsorbed by S-M bone interaction mode would not be desorbed,resulting CeY₅₅₀ sorbent owning highest adsorption capacity.?3?CeY₅₅₀ sorbent was selected to investigate the influence of H₂ and CO on its desulfurization performance.The results showed that the presence of H₂ or CO in desulfurization atmosphere could decrease the adsorption capacity.In reductive atmosphere,Ce⁴⁺in sorbent could be reducted into cerium with lower valence state.Ce⁴⁺,with more empty orbitals,has stronger interaction with thiophene by S-Ce bond.