Study On The Preparation And Properties Of Polyimide Fiber Paper-Based Filters For High Temperature Fume

In recent years,most of our country has been attacked by the haze weather frequently.Haze has became a familiar term from“smog”first became the annual hot words in 2013 to premier li keqiang personally included“resolutely fighting blue sky battles”in the government work report in 2017.It is generally known that the haze is caused by the high concentration of fine particulate matter PMs in the air.PMs from industrial pollution,burning coal,biomass burning,transportation,and garbage incineration usually has a very high temperature.Therefore,the research and development of high-temperature fume filters with excellent filtration properties and the direct removal of PM from high temperature sources is a key measure to solve and effectively control PM pollution and reduce air pollution.The paper-based filter made by modern wet papermaking technology is an ideal method to prepare filter material because of its unique three-dimensional network structure.Therefore,in this paper,polyimide fiber with excellent high temperature resistance was selected as raw material and wet papermaking technology was used to explore the application potential of polyimide fiber paper-based composites in the field of high temperature fume filtration.The main research contents are as follows:First of all,the raw material ratio of paper-based filter and paper post-treament process are studied.The results show paper-based filter prepared by PI fiber and aramid fiber have the best filtration performance.As the proportion of precipitated fibers decreases,The filtration efficiency of paper-based decreased from 99.19%to 55.19%,pressure drop decreased from305 Pa to 44.5 Pa and the mass factor increased from 0.0158 Pa^-11 to 0.01804Pa^-1.Cold calendering and hot pressing shall not apply to prepare paper-based filter,because the filtering efficiency can obviously improve?above 98%?,but the filter pressure drop has increased sharply and even more than the instrument test range?1000 Pa?,leading to paper-based filter with low quality factor.Therefore,considering the mechanical properties and filtration properties of filter,the comprehensive properties of paper-based filter are optimal as the ratio of PI fiber to precipitated fiber is 7:3.At this point,the mass factor is 0.01712Pa^-1,the filtration efficiency is 58.95%,and the pressure drop is 52 Pa.The tensile strength is 2.325 MPa,and the elongation at break is 3.189%.Secondly,in order to obtain paper-based filter with better filtration performance,pre-synthesized metal framework compound MIL-101?Cr?was introduced to explore the relationship between the addition amount of MIL-101?Cr?and the filtration performance of paper-based filter.The results showed that MIL-101?Cr?was dark green powder and regular octahedral structure under SEM and with perfect crystal structure,large specific surface area up to 3024 m²/g and excellent thermal stability?Td=380 ^oC?.MIL-101?Cr?/PI fiber paper-based composite filter prepared by modern wet papermaking technology pretend excellent filtration performance for high temperature fume.At room temperature,when the addition amount of MIL-101?Cr?is 60%and 70%,the filtration efficiency is 99.03%and 99.49%,respectively,and the pressure drop was 70.5 Pa and 87.5 Pa respectively with little change compared with the pristine filter,and the highest quality factor was0.0657 Pa^-11 with an increase of 283.76%compared with the pristine paper.Under 260 ^oC,the quality factor of composite material increased obviously and the maximum is 0.1402 Pa^-11 increased by 558.22%relatived to the pristine filter.Finally,in order to improve the difficulty in dispersing and low retention of MIL-101?Cr?in paper-based filter,PI fiber was preimpregnated with dopamine and coated with 2?-CD/CTAB as self-assembly agent.NH₂-MIL-101?Cr?,a metal framework compound presynthesized by solvent thermal method,was assembled on the surface of dopamine-activated PI fiber through the layered self-assembly method to prepare MOF@PI@PDA fiber paper-based filter.The filtration results showed that the paper-based filter prepared by PI fiber modifiedbyNH₂-MIL-101?Cr?nanocrystalshadexcellentfiltration performance for high temperature flue gas.At room temperature,the filtration efficiency of PM0.3 by MOF@PI@PDA fiber paper-based filter reached97.77%?improved by 65.87%compared with the pristine paper-based filter?,the pressure drop was 73 Pa and the quality factor reached 0.0521 Pa^-1?improved by 204.68%compared than pristine filter?.At 260 ^oC,the filtration efficiency of MOF@PI@PDA fiber paper-based filter for PM0.3 was 93.05±1.27%with a low pressure drop of 57.5 Pa and a high mass factor of 0.0464 Pa^-1.Compared with the pristine paper-based filter,MOF@PI@PDA fiber paper-based filter showed a broader particle size capture efficiency for PMs,that is,a higher removal efficiency for PM10-0.3?over 95%?.