Preparation And Gas Separation Performance Of Polyether Amide Mixed Matrix Membrane

Many by-products are produced during the metallurgical process in the traditional metal industry.Thereinto,the blast furnace gas is the main by-product.The combustible composition containing in the blast furnace gas is relatively low.Actually,the blast furnace gas is mainly composed of non-combustible gas such as CO₂,N₂,ext.Due to its low calorific value,the blast furnace gas is difficult to recycle.At the same time,both the highly recycling cost and profitability difficulty result in that a lot of metal enterprises discharged this by-product directly into the air.This could increase the atmosphere greenhouse effect.Moreover,it also can lead to increase the energy consumption of enterprises and achieve difficultly the consumption reduction goal of enterprises.In recent years,the recovery and utilization of CO₂ and N₂ from blast furnace gas is a hot issue to realize waste gas recycling,reduce air pollution and sustainable development.With the rapid development of economy and technology,there is a need to seek an efficient,economical and environmentally friendly separation technology.Along with this,the membrane separation technology has attracted researches attention,and it is gradually used in the field of gas separation.In order to solve the problem of difficult recovery of blast furnace gas,in this work,a mixed matrix membrane was prepared.In fact,graphene oxide,carboxylated graphene oxide and single-walled carbon nanotubes are used as dopants,and an organic polymer polyether amide with unique adsorption capacity of CO₂ as the matrix material.Gas separation experiments for single and mixed gases are perfumed on the self-conducted equipment in our laboratory.The results show that the mixed matrix membrane doped with graphene oxide,carboxylated graphene oxide and single-walled carbon nanotubes exhibits excellent gas separation performance and improves the recycling rate of blast furnace gas.In this dissertation,graphene oxide（GO） was prepared by improved Hummer method;carboxylated graphene oxide（COOH-GO） and purified single-walled carbon nanotubes（SWCNTs） were prepared by mixed acid method;GO/Pebax1657mixed,COOH-GO/Pebax1657mixedand GO/SWCNTs/Pebax1657 mixed base membranes were prepared by the method of solution cast film formation.The field emission scanning electron microscopy（FESEM）,transmission electron microscopy（TEM）,thermogravimetric analyzer（TGA）,X-ray diffractometer（XRD）,Fourier infrared spectrometer（FTIR）,atomic force microscopy（AFM） were used to characterize the material prepared.The results show that graphene oxide after ultrasonic dispersion possesses a single layer sheet-like structure and contains a large number of oxygen-containing groups;carboxylated graphene oxide also has a single layer sheet-like structure,however,it contains a large number of carboxyl groups,thus,the sheet spacing of carboxylated graphene oxide is larger than that of graphene oxide;in single-walled carbon nanotubes（SWCNTs） after mixed acid purification the impurities are reduced,closed port of carbon nanotubes is opened,thus,the agglomeration phenomenon of SWCNTs is reduced.The spatial synergies effect of Go and SWCNTs makes the dopant is more evenly distributed in the polymer matrix,this enhances the uniformity of the mixed matrix membrane.Dopant GO,SWCNTs and polymer substrate Pebax1657 after ultrasound,magnetic stirring,GO successfully attached to the Pebax1657,and SWCNTs were successfully embedded in the GO and Pebax1657 substrate.Ethanol was used as solvent of Pebax1657 and as dispersant of GO and SWCNTs.At 80℃,the method of solution cast film formation was adopted to prepare a lot of mixed matrix membrane by using a reflux device to dissolve Pebax1657 particles.Gas separation for single and mixed gases were perfumed on the self-conducted gas separation equipment in our laboratory by using the mixed matrix membranes.The experimental results show that with the increase of the experimental temperature,the permeability coefficient of single gas and mixed gas decreases.Moreover,with the increase of the initial intake pressure,the permeability coefficient of single gas and mixed gas increases.Co MPared with that of pure Pebax1657 membrane,gas separation performance of three different types of mixed matrix membranes is greatly improved.Different types of nano-dopants can lead to different gas separation performance.GO/SWCNTs/Pebax1657 mixed matrix membrane exhibits the most excellent gas separation performance due to the synergistic effect of GO and SWCNTs.When the intake pressure rose from 0.1 MPa to 0.2 MPa,the permeability coefficient of CO₂ has a significant upward trend,the permeability coefficient of N₂fluctuates in a small range,and the permeability of the mixed matrix membrane of CO₂ was significantly higher than that of N₂.The selectivity values of three mixed matrix membranes are as follows:α（CO₂/CO）>α（CO₂/N₂）>α（N₂/CO）.The experiment temperature is 298 K,in air pressure is 0.2 MPa,the GO/Pebax1657 mixed matrix membrane permeability coefficient single gas CO₂is 2965 Barrer,the permeability coefficient of N₂ is 1691 Barrer,CO₂,N₂and CO in the mixed gases permeability coefficient of 1916 Barrer,655 Barrer and 176 Barrer respectively.Selectivity are alpha of（CO₂/CO）=18,alpha（CO₂/N₂）=14.83,alpha（N₂/CO）=10.76.COOH-GO/Pebax1657 mixed matrix membrane permeability coefficient single gas CO₂is 2974 Barrer,the permeability coefficient of N₂ is 1700 Barrer,CO₂,N₂ and CO in the mixed gases permeability coefficient of 2255 Barrerr,764 Barrerr and 159 Barrerr respectively.Selectivity are alpha of mixed gases（CO₂/CO）=23.8,alpha（CO₂/N₂）=16.5,alpha（N₂/CO）=12.75.GO/SWCNTs/Pebax1657 mixed matrix membrane permeability coefficient single gas CO₂ is 3233 Barrer,the permeability coefficient of N₂ is 1153 Barrer,CO₂,N₂ and CO in the mixed gases permeability coefficient of 2439 Barrer,787 Barrer and 184Barrerrespectively.Selectivity are alpha of mixed gases（CO2/CO）=20.41,alpha （CO₂/N₂）=17.03,alpha （N₂/CO）=11.61.According to the gas separation experimentresults,GO/Pebax1657,COOH-GO/Pebax1657,and GO/SWCNTs/Pebax1657 mixed matrix membranes can be used to separate CO₂and N₂from blast furnace gas,but the best is GO/SWCNTs/Pebax1657 mixed matrix membrane.