Study On Low Temperature Catalytic Hydrolysis Of COS And CS₂ With Metal Modified Activated Carbon Fiber Catalyst

In the yellow phosphorus tail gas,the content of COS is about 700-1000 mg/m³,and the content of CS₂is about 20-80 mg/m³.In order to make use of the CO in the yellow phosphorus tail gas,we must deal with the toxic impurity gases in the tail gas firstly.Among many COS and CS₂removal methods,the catalytic hydrolysis method is widely used for the removal of COS and CS₂because of its higher catalytic selectivity,lower operating temperature,and mild reaction conditions.At present,activated carbon desulfurization is widely used at home and abroad,but the sulfur capacity is generally low in the removal of COS and CS₂.Therefore,based on the research on the simultaneous removal of COS and CS₂by activated carbon,activated carbon fiber was selected as a carrier to load different types of metal active components and alkali,developed a series of activated carbon fiber catalysts for the simultaneous catalytic hydrolysis of COS and CS₂.Compared with activated carbon,activated carbon fiber has a higher specific surface area,larger pore volume and higher adsorption capacity,and the adsorption of carbon fiber has the characteristics of short equilibrium time,large equilibrium adsorption capacity,and has the excellent renewable performance.It can be recycled and has good characteristics as a catalyst support.Based on the characteristics of yellow phosphorus tail gas,metal and alkali modified activated carbon fiber catalysts were used to catalyze the hydrolysis of COS and CS₂at the same time.The characteristics of the catalytic hydrolysis activity were investigated by means of characterization,and the reaction mechanism of the catalytic hydrolysis was speculated.The main research contents include:A series of activated carbon fiber catalysts were prepared by the sol-gel method and the impregnation method for the simultaneous catalytic hydrolysis of COS and CS₂.The effects of catalyst preparation conditions?metal oxide species,metal oxide content,metal salt precursor,calcination temperature,alkali species and alkali content?on the activity of simultaneous catalytic hydrolysis of COS and CS₂were systematically studied.At the same time,the necessary characterization analysis of catalysts was performed by means of characterization methods such as BET,CO₂-TPD,TG/DTA and so on,and the speculate structure-activity relationship,reaction process and related reaction mechanism of catalytic hydrolysis were inferred.The effects of experimental process conditions?reaction temperature,relative humidity,gas hourly space velocity,inlet concentration of COS and CS₂?on the efficiency of simultaneous catalytic hydrolysis of COS and CS₂were systematically studied.The specific research conclusions are as follows:?1?Screening of activated carbon fiber?ACF?catalyst preparation conditions:From the experimental results,it can be known that the optimal preparation conditions were supported metal salt Co?NO₃?₂,Co metal oxide content was 5%,calcination temperature was 550?and KOH content was 5%,having the best removal efficiency of COS and CS₂.Among them,the metal activity of different types of metals affected the formation of sulfate on the catalyst surface,resulting in differences in desulfurization efficiency.Different amounts of Co metal would affect the micropore structure and specific surface area of the catalyst.The type and number of functional groups produced by different precursors of Co metal salts during the calcination process would cause differences in the number of active sites on the catalyst surface.Different calcination temperatures would affect the formation of catalyst micropores and the integrity of micropores.The type of base would affect the number of strong basic sites on the catalyst surface.Different KOH contents would affect the number of available-OH functional groups on the catalyst surface,and then the number and quality of active sites on the catalyst.?2?Optimization of process conditions:The experimental results of different reaction conditions showed that the best reaction conditions were:the reaction temperature was 60?,the relative humidity was 50%,the gas hourly space velocity was 7000 h^-1,the ratio of CS₂and COS inlet concentration was 1:40,in other words,the COS inlet concentration was 1072 mg/m³,and the CS₂inlet concentration was 34mg/m³.At the same time,the catalyst had the best conversion rate of COS and CS₂.The reaction temperature was too low,the active components of the catalyst were not active.Instead,the reaction temperature was too high,the sulfate produced by the catalytic oxidation was increased,and the catalyst was deactivated faster.Proper relative humidity can promote the catalytic hydrolysis reaction.Excessively high relative humidity would promote the formation of water films on the catalyst surface and inhibit the diffusion of COS and CS₂gas on the catalyst surface and micropores.Lower reaction space velocity would increase the contact time and the contact area between COS and CS₂molecules and the ACF catalyst.Excessively high reaction space velocity was not conducive to sufficient contact between pollutant molecules and catalysts,leading to desulfurization efficiency.With the increase of CS₂inlet concentration,COS and CS₂would compete for adsorption,and at the same time be affected by H₂S,the catalytic hydrolysis efficiency of COS and CS₂would show a downward trend.