Controllable Synthesis Of Porous Boron Nitride Fiber And Their Adsorption Desulfurization Properties

In recent years,as the environmental pollution has become increasing serious,the low vulcanization and cleanliness of fuel oil is a general trend.As a green,low-cost,and easy-to-operate desulfurization technology,adsorption desulfurization has attracted extensive attentions and researches.Finding an effective desulfurization sorbent with high adsorption capacity,high selectivity and high regeneration ability has attracted great attention in the scientific community.Porous boron nitride?BN?micro/nano fibers with high specific surface areas,large pore volumes,excellent chemical stability and intrinsic local polarity could be a promising candidate for adsorptive desulfurization materials.In this dissertation,we report on the controllable synthesis and surface modification of porous BN micro/nanofibers.The adsorption desulfurization performances of the synthesized adsorbents were studied.The main research contents are as follows:1.The adsorbent precursors are prepared using boric acid and melamine as raw materials.After the high temperature pyrolysis treatment of the precursors,porous BN microfibers can be obtained.The effects of high temperature pyrolysis temperatures?900°C¹400°C?on the structure,specific surface area and pore distribution of the synthesized porous BN microfibers have been studied.Desulfurization adsorption experiments show that the as-prepared porous BN microfiber adsorbent displays excellent adsorptive desulfurization capacity.In particular,porous BN microfibers synthesized at1100°C dispaly high specific surface area?939.74 m²/g?and large micropore volumes.The product not only echibits very high adsorption capacity for dibenzothiophene?DBT?in a simulated oil(the measured value is of 41.59 mg S g^-1,the theoretical value is of 86.10 mg S g^-1),but also shows good regeneration cycle performance.After four regeneration cycles,the amount of desulfurization can reach 76.51%.The adsorption mechanism is mainly affected by the pore size selection mechanism of the adsorbent and similar to the‘S-M'adsorption mechanism.2.Porous BN nanofibers are synthesized by freeze-drying and high temperature pyrolysis of the precursor.The effects of pyrolysis temperature on the structure,specific surface area and pore distribution of nanofibers have been studied.With the increase of pyrolysis temperature,the crystallization degree of the as-synthesized porous BN nanofibers gradually increases.The porous BN nanofiber adsorbent prepared at 1200°C has the largest specific surface area?876.23 m²/g?and high DBT adsorption capacity(the measured value is of 35.73 mg S g^-1,the theoretical value is of 45.31 mg S g^-1).Moreover,the porous BN nanofibers show superior adsorption desulfurization performance in low sulfur concentration conditions??100 mg/L?as compared with porous BN microfiber.After three times of regeneration cycle,the amount of desulfurization can reach 86.12%of the initial adsorption amount.Therefore,the porous BN nanofiber adsorbent has great application prospects in the desulfurization industry,especially the low-sulfur desulfurization.3.CeO₂ coated porous BN microfiber adsorbents are synthesized by adsorbing of porous BN microfibers with Ce ions and then calcining at high temperature.Desulfurization adsorption experiments show that the as-prepared CeO₂/BN adsorbents show good desulfurization capacity in simulated oils.The 1.5 CeO₂/BN adsorbent shows higher DBT adsorption capacity,with a measured value of 14.27 mg S g^-1 and a theoretical value of 17.33 mg S g^-1.In addition,compared to pure porous BN microfibers,the CeO₂-coated BN microfiber adsorbent shows superior desulfurization performance at low sulfur concentrations??100 mg/L?.However,their regeneration cycle performance needs to be improved.