| Energy and environment,as the foundation of the national economy and social development,have always been hot-spot issues that the international communities focus on.In recent years,as China's rapid economic development,the energy source shortage and environment pollution are getting more and more serious.To reform our energy system is the key to solve these problems.On the one hand,supply from new types of green energy need to be continuously developed and improved;on the other hand,to strengthen the implementation of the strategic deployment of energy conservation and emission reduction is necessary.Gas separation is one of the keys to industrial production.To develop novel technologies for gas separation is an effective way to deal with energy and environmental issues and achieve the emission reduction.Membrane technology for gas separation has been the most potential gas separation technology,due to its advantages of low energy consumption,easy to operation,nearly emissions-free and high selectivity.In this paper,a series of novel tubular ultra-thin membranes on alumina ceramic tubes were provide,that were successfully used for gas separation with excellent permeance and gas selectivies.Theoretically,the better the permeance and selectivity of a membrane,the higher its efficiency.One of the factors that affect the performance of the membrane is its thickness.Reducing the thickness of the membrane can shorten the gas mass transfer path,thereby effectively improving its gas permeance.For mixed matrix membranes,the interface between the filler and the matrix has remarkable effects on the permselectivity.Reducing the size of fillers or adjusting their morphologys can make it better compatible with the matrix and better dispersed in the matrix,thus improving the permselectivity.The porous organosilica materials are used as gas separation membrane materials,as the advantages of the adjustable network structure,modifiable functional groups,and excellent hydrothermal stability,and they are easily prepared via simple sol-gel method.The organosilica materials have strong substrates adaptability,and can be coated on various porous substrates,including the alumina tubes in this paper.In addition,the organosilica materials has higher permeability than the classical polymer matrix.On the other hand,the organic bridging group between two silicon atoms and the silicon hydroxyl groups in its structure can increase the compatibility between the porous organosilicon material and the substrates or fillers(such as MOFs nanocrystals).Therefore,the porous organosilica material is an ideal candidate matrix for preparing mixed matrix membranes.Based on the above,the main contents and fidings in this paper are given as following:(1)The morphology of ZIF-8 nanocrystals was regulated by using urea to prepare ZIF-8 spherical nanocrystals,which were well dispersed in organosilica sols.With ZIF-8 spherical nanocrystals as fillers,organosilica as the matrix,a ZIF-8/organosilica ultrathin tubular membrane was prepared via hot dip-coating method,and how different ZIF-8 loadings affect the permselectivity of the prepared membranes was studied.Results show that the membrane with equal mass of ZIF-8 and organosilica showed excellent H2 and CO2 permeances and selectivities,with H2 permeance of 1.25 x 10-6mol·m-2·s-1·Pa-1,ideal selectiveities as high as 165.5 for H2/CH4,43 for CO2/CH4.The selectiveities of H2/CH4 and CO2/CH4 are 107.4 and 26.9,respectively,in the two-component gas mixture test.Finally,the feasibility and universality of the method to prepared organosilica tubular membranes with urea regulating the morphology of ZIFs was verified by the ZIF-90/organosilica membrane.(2)GO/organosilica ultrathin tubular membrane was prepared using 2D graphene oxide as fillers and organosilica as the matrix,with thickness as low as 25 nm.The interaction of between GO and organosilica and the existential form of GO in the membranes were characterized by FT-IR,XRD and SEM.Results showed that GO nanosheets were reduced partially to r GO at high temperature during the polymerization to form membranes,and bonded with the Si-OH on organosilica to form more compact and continuous separation membranes.How different GO loadings affect the permselectivies performance of membranes were studied,and the optimal GO loadings was the GO/organosilica mass ratio of 1/1.At room temperature,the H2 permeance of the membrane was 2.5×10-7 mol·m-2·s-1·Pa-1,and its ideal selectivities of H2/CH4 and CO2/CH4 reached to 223.14 and 54.67 respectively.The membrane also showed excellent H2/CH4 and CO2/CH4 separation performance in the binary gas mixture gas test.Moreover,the prepared membrane also has excellent permselectivity under high temperature,indicating its high stability under high temperature.(3)On the basis of the previous work,the hot dip-coating method was applied to to prepare polymer-based ultrathin tubular membranes with nanoscale thickness,which has good H2/CO2 separation performance.With organosilica as the intermediate layer,the integration between the membrane and the substrate was enhanced,and the efficient separation channels for gases were constructed.How the MOFs loading affect the thermal stability,the glass transition temperature and the permselectivity of the prepared membranes were studied.Results showed that MOFs did improve the thermal stability and the glass transition temperature of the polymer-based membranes.In addition,the membrane with 20 wt%MOFs loading showed the greatest H2/CO2separation with 53.12,beyond the Robeson's upper bound,and its permeance was 1-2orders of magnitude higher than most reported polymer matrix membranes.Finally,the feasibility of such a method was verified by changing MOFs or polymers. |
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