Preparation And Porperties Of Graphene Oxide/chitosan Composite Aerogel And SiO₂ Aerogel Microspheres

Aerogels have become more and more concerned to many researchers due to their excellent performance.Since the successful preparation of the first aerogel in 1937,the aerogel material has been developed more than ever before,and the organic,inorganic and composite aerogel have been developed in a series,and the preparation method of various aerogels has been very mature.Now,the aerogel gradually begins to be used as a concept,and more and more researchers have started to apply the aerogel to various fields so that it can continue to play a different color.The research of aerogels has been focused on the functionalization and application of aerogels,so it is important to continue to explore the functionalization of aerogels so that its application in more fields is an important work of the future development of aerogels.This paper focuses on the development and functional application of organic natural bio-macromolecule chitosan aerogel and inorganic SiO2 aerogel.The improvement of structure and comprehensive properties of chitosan aerogel by graphene oxide and the application of inorganic SiO2 aerogel as gel breaker carrier in the field of petroleum exploitation have expanded the application of aerogel in more fields.Chitosan aerogels and graphene/chitosan composite aerogels were prepared by one-step dissolution and freeze-drying of acetic acid solution using chitosan as raw material and graphene oxide as additive.The effects of different chitosan concentration and graphene oxide content on the microstructure,mechanical properties and thermal stability of chitosan aerogels were analyzed by SEM,FTIR,XRD and XPS.The mechanism of the increase of crystallinity of chitosan aerogel with the content of graphene oxide was investigated.The results showed that the crosslinking degree and mechanical properties of chitosan aerogels were greatly improved with the increase of chitosan concentration from 1.2 wt.%to 4.8 wt.%,The porosity of chitosan aerogels increased from 83.7%to 87.6%,and the maximum fracture load increased from 0.94 MPa to 6.06 MPa.The effect of different amount of graphene oxide on the microstructure and comprehensive properties of chitosan composite aerogel was investigated with the ratio of 3.6 wt.%chitosan.The results showed that the porosity of graphene oxide/chitosan composite aerogel reached 90.1%and the maximum fracture load was 10.56 MPa.when the addition of graphene oxide was 15 wt.%.It was also found that the crystallinity of chitosan aerogels increased with the increase of graphene oxide content.The crystallinity of chitosan aerogels increased from 23.7%of pure chitosan to 81.1%when the addition of graphene oxide was 15 wt.%,The carboxyl group on graphene oxide reacts with the amino group in chitosan,which makes the molecular chain of chitosan more regular,indicating that graphene oxide not only improves the mechanical properties of chitosan aerogel by means of physical enhancement,but also improves the mechanical properties of chitosan aerogel.At the same time,the thermal stability of chitosan aerogel was improved by chemical crosslinking.In this work,we hope to change the crystallinity of chitosan by adding graphene oxide,so as to provide a new method to improve the heat resistance and mechanical properties of organic chitosan aerogels.In order to solve the problem of the traditional gel breaker releasing ahead of time in the middle and deep reservoirs with high temperature,the inorganic SiO2 aerogel was used as the insulating shell material and ammonium persulfate as the core material for the first time.The SiO2 aerogel supported ammonium persulfate gel breaker was prepared by sol-gel method and inverse emulsion polymerization.The microstructure and load release of the gel breaker microspheres were investigated by SEM,FTIR,EDS,pH method.The release rate and so on were characterized.The results show that the loading amount of ammonium persulfate in silica aerogel is about 53 wt.%.SiO2 as protective material and the gel breaker has obvious delayed release effect.The release is slow and the delay time is long at 30?,and with the increase of temperature,the release of ammonium persulfate in silica aerogel is slow and the delay time is long.The release amount increases and the release time increases,but the delayed release effect is still very obvious at the temperature of 70?,which can reach about 130 min and the release rate reaches 65%,which satisfies the use conditions of the middle and deep reservoirs.The application of SiO2 aerogel-loaded ammonium persulfate microspheres in middle-deep reservoirs is broadened.