Study On CO₂ Adsorption Of Mixed Metal Oxide Under Medium Temperature

With the development of new energy and utilization,coal gasification and clean utilization of hydrogen production process,as an efficient energy technology,has broad prospects in China.In the process of coal gasification clean utilization,the use of energy-saving and low-cost methods to separate CO2 can effectively reduce the cost of coal gasification process and increase the efficiency.Layered double hydroxide(LDH)can be used to make Layered double oxide(LDO)after calcined.LDO has good adsorption properties for CO2.It is of great theoretical and practical significance to study on its adsorption mechanism and a improve its adsorption performance.In this work,the effect of elemental composition on CO2 absorption and desorption of LDO was analyzed by controlling the composition of LDH.The relationship between the basic sites of LDO,the bonding of LDO surface with CO2 under different conditions,the surface morphology and the adsorption properties of CO2 were studied.The viewpoint that the medium and strong basic sites on the LDO surface are the key factors controlling the adsorption capacity of CO2 in medium temperature was proposed.The adsorption capacity of LDO can be adjusted by controlling the number of basic sites.Based on this method,The number of medium and strong basic sites on the surface was increased by the method of organic anion intercalation and methyl cellulose addition.The CO2 adsorption capacity of LDO was increased from 0.247 mmol/g to 0.850 mmol/g at 300℃,and the maximum adsorption rate was increased from 0.04 mmol/g min to 0.37 mmol/g min,which made the CO2 adsorption capacity of LDO improved significantly.In this work,citrate,stearate and benzoate anion intercalated LDH were prepared by direct synthesis.The organic anion was dehydrated between layers by anoxic calcination,and nano-sized amorphous carbon was formed in situ.an LDO/nanocarbon adsorbent was obtained.nanocarbon maintains the pore structure of LDO and increases the number of effective basic sites of LDO/nano-carbon.Besides,carbonyl and carboxyl functional groups on the nanocarbon surface serve as adsorption sites for CO2.The adsorption capacity of CO2 for LDO-CA-air at 300℃ increased from 0.37 mmol/g to 0.68 mmol/g for LDO-CA-N2,and the maximum adsorption rate increased from 0.16 mmol/g·min to 0.26 mmol/g·min,its adsorption capacity was improved effectively.Based on the literature and experiments,this work proposes the rule that the basic sites affect the CO2 adsorption capacity of LDO on medium temperature.This word enriches the gas adsorption theory of LDO and expands the preparation methods and application fields of LDO composite materials.