Research On The Preparation And Properties Of Small Diameter Molecular Sieve K/Cs-ZK-5 Based On Natural Gas Purification Decarburization

Natural gas is a kind of high quality,clean and low carbon energy which is mainly based on CH₄ gas.The existence of CO₂ will not only cause the corrosion of the pipeline by CH₄ during the pipeline transmission,but also reduce the calorific value of the combustion.Therefore,the removal of CO₂ will be beneficial to the transportation and utilization of energy gas.Adsorption separation technology has attracted wide attention because it is considered as one of the technologies with low energy consumption and simple operation in the field of gas separation.The researchers found that the capture of CO₂ from natural gas by adsorption separation could be a potential alternative to the conventional decarburization method by amine solutions.At present,carbon materials?activated carbon and carbon molecular sieves?,zeolite molecular sieves and the recently emerging metal organic framework?MOFs?materials are more widely used.The pore structure of carbon materials is not uniform,and the preparation condition is limited by the raw materials;MOFs materials are with poor stability.Compared with these materials,zeolite has uniform pore structure,good thermal stability,and adjustable specific surface area and pore volume.Therefore,lots of study and application of zeolite as adsorbent has been commissioned.This paper studies the small pore size zeolite ZK-5,and ZK-5 with Si/Al ratio between 3.2-3.6 has been prepared.Through the exchange of Cs and K ions,ZK-5 molecular sieves with molecular gate effect are obtained which only allows CO₂ gas to enter the pore and restricts the passing of CH₄,thus having excellent CO₂/CH₄ separation effect.The main contents and conclusions of this thesis include:?1?Four different ZK-5 molecular sieves in the small range of Si/Al ratio were synthesized by silica sol as silicon source and potassium aluminates as aluminum source.The ratio of silica to aluminum was 3.2,3.3,3.39,3.54 and the corresponding Cs-ZK-5?Cs/K = 9/1?molecular sieves were obtained by ion exchange.?2?The performance of four kinds of Cs-ZK-5 zeolites with different Si/Al ratios were characterized.The Cs-ZK-5 were characterized by XRD,SEM,TG and elemental analys is.It is showed that the Cs-ZK-5 exhibited good thermal stability and crystal structure and good crystal structure.CO₂,CH₄ and N₂ adsorption on four Cs-ZK-5 zeolites revealed that the introduction of more Cs+ would reduce pore volume.Although the adsorption capacity of CH₄ materials decreased,the adsorption capacity of CO₂ is low,resulting in the selectivity of CO₂/CH₄,CO₂/N₂ and CH₄/N₂ did not significantly improved compared to the K-KFI,but the adsorption ratio and adsorption selectivity of CO₂/CH₄ are better than those of conventional adsorbents.?3?The K-ZK-5?Cs/K = 1/9?molecular sieve with different Si/Al ratios were obtained by K ion exchange,and the gas adsorption performance test was carried out.It is showed that when s i/al ratio is relatively low,the introduction of more K+,with the effect of molecular gate,can enhance the CO₂/CH₄ adsorption selectivity.Among them,ZK-5-1-K has excellent adsorption selectivity of CO₂/CH₄,and the adsorption selectivity of CO₂/CH₄ is 283 at 298 K and 100 kPa.However,with the increasing of Si/Al ratio,the effect of molecular gate disappears,and the adsorption selectivit y of CO₂/CH₄ decreases.