Synthesis Of BN Nanomaterials And Application Of CO₂ Adsorption

With the consistent development of industrialization of human society,the concentration of CO₂ in the atmosphere continues to increase.The emissions of CO₂-the main greenhouse gas causes global temperature rise.Carbon dioxide capture and storage?CCS?technology is a main means to reduce CO₂ emissions,attracting large numbers of researches and explorations.CO₂ capture is the core of CCS technology,which includes chemical absorption method,membrane separation method,low temperature separation method,and adsorption separation method.Among them,the capture method of adsorption separation utilizing solid adsorption materials has the advantages of renewable cycle,easy recovery,material wih high stability,adjustable structure,etc.,and has become the most promising CO₂ capture technology.Hexagonal boron nitride?h-BN?is isostructural with graphite with good mechanical property,high thermal conductivity,stable chemical property,strong resistance to oxidation and reduction,etc..It has become a novel and promising solid adsorbent material.The surface groups,acidity and basicity,pore structure and other factors will affect the CO₂ adsorption capacity of BN material.In this paper,controlled synthesis of BN materials with different morphologies and carbon-doped BN materials were used for study the effect of their structures on CO₂ adsorption.The main work is divided into the following two aspects:1.The triangular and hexagonal BN nanoplates were prepared and their CO₂ adsorption properties were studied.BN triangular and hexagonal plates were prepared by using the different boron and nitrogen sources,then characterized by XRD,FTIR and XPS thechniques,and finally tested for CO₂ adsorption performance.The reaction temperature,reaction time and feed ratios affected on morphology and size of BN materials,and the formation mechanism of BN material was preliminarily analyzed.The edges of BN triangular plates end with unique N atom,while the edges of BN hexagonal plates end with B and N atom,and BN hexagonal plates are obtained at high synthesis temperature.There were more-NH₂ groups on the edges of BN triangular plates than ones on the edges of BN hexegonal plate because of the differences in the structure and synthesis environment of BN materials.The acidic CO₂molecules tend to adsorb on-NH₂ groups.Therefore,CO₂ adsorption performance of BN triangular plate is better than one of BN hexagonal plate.2.Carbon doped BN materials were prepared and their CO₂ adsorption properties were studied.BCN materials with the different structures were obtianed by pyrolysis of boric acid and melamine at the different temperatures.At 25 ^oC and 1 bar pressure,the BCN material calcined at 600 ^oC has the best CO₂ adsorption performance,reaching 3.44 mmol/g.Under the condition of simulated composition of flue gas with 15%CO₂ and 85%N₂,the CO₂/N₂selectivity of the material is 51.Reversible adsorption tests proved that BCN material can be completely regenerated and reused.Through FTIR,XPS,NMR and other characterizations,it is deduced that the microporous structure and electron properties of BCN materials are the main factors to improve CO₂ adsorption performance.