Selection Of Efficient Adsorbent Using For Separating Carbon Dioxide From Natural Gas

Under the major trends of energy saving and emission reduction,the demand of natural gas has a rapid growth because of its clean and high efficiency characteristics.In addition to the development of onshore natural gas resources,the offshore natural gas resources has become an important part.But due to the complex environment and limited space,the difficulty of decarbonization has increased greatly.Considering the different methods,adsorption method is chosen as the research method.13X zeolite is chosen as the basic material because of its good CO₂ adsorption ability.Simulation and experiment are used to modify 13X zeolite and characterize its microstructure characterization and investigate the separation effect of mixed gas.13X zeolite is modified by ion K⁺?Ca²⁺?Li⁺?Ag⁺?Pd²⁺with GCMC simulation method.Based on the analysis of simulation results,13X zeolite is modified with three different kinds of ions which include main Lⁱ⁺ions and a small amount of Ag⁺,Pd²⁺ions.The LiPdAgX molecular sieve has a higher adsorption capacity and a good ability to separate the mixture of CO₂.Therefore the LiPdAgX is used as the object of modified experiment,LiX and 13X molecular sieve are used as control group.On the basis of simulation,LiX and LiPdAgX molecular sieves are prepared by ion exchange method.It is found that the framework of molecular sieves is not destoried in the process of modifying.Only the different metal ions changed the internal electrostatic field of the molecular sieve,and the modifying increased the relative crystallinity of the molecular sieve.The specific surface area,pore volume and pore size distribution are also improved.Under 1.4MPa pressure,the CO₂ adsorption amount of 13X is 7.11mg/g,LiX is8.84mg/g and LiPdAgX improved to 9.82mg/g.Due to the similarity of N₂ and CH₄properties,considering the safety factors,N₂ is used instead of CH₄.In mixed gas adsorption experiments,the adsorption selectivity coefficient of 13X is 71.34,LiX is 102.56,LiPdAgX is128 at 1.4MPa.The breakthrough time of modified samples are extended LiPdAgX has the largest mixed gas separation coefficient in the three samples.The average value is 7.2,while the average of 13X is 3.96.And the modified molecular sieves have lower regeneration energy consumption.It can keep a high separation coeffcient when it is recycling used.Based on the above research results,considering the microstructure and adsorption experiments,LiPdAgX is more suitable for the removal of CO₂ from natural gas.