Preparation Of Novel Polyphenylene Sulfide Composite Filter Materials With Denitration Function And Their Properties Investigation

The industrial waste gas which includes solid particles and toxic gases will not only destroy the ecological environment, but also have a serious harm to human’s health. Bag filter is an effective device for controlling the emission of solid particles, and its main component is filter material. Polyphenylene sulfide (PPS) filter material has been widely used in harsh environments such as coal-fired boilers and waste incineration plants due to the excellent performances of high temperature resistance, acid-base resistance, excellent hydrolysis resistance and high flame retardant. The composite filter materials with denitration function prepared by supported denitration catalyst on the surface of filter materials will not only obtain the difunctional of dust removal and denitration, but also save the space and investments of tail gas treatment. But, the commercial catalysts are used in the high temperature range of 300-400℃, which is far beyond the operating temperature of PPS filter material (about 170℃). On the other hand, the inert surface of PPS filter material makes it difficult to combine with the catalyst particles. Therefore, investigation and development of the low-temperature catalyst with high efficiency and its composite technology with PPS filter material are the key point of this paper.Manganese oxides showed well activity for the low-temperature selectivity catalytic reduction of NO, and can be also supported on carrier materials to enhance their activity due to the higher specific surface area and better dispersion of active sites. Due to their special morphology, large special surface area and big long-radius ratio of carbon nanotubes (CNTs), there have been widely used in catalyst support as well as polymer composites. So, the acid-treated CNTs were first used to support manganese oxides by high-temperature calcination method and low-temperature liquid method. TG, XRD, TPR, and NH3-SCR techniques were used to investigate the structure and properties of these catalysts. And the results showed the calcination condition played an important role on the crystal structure of manganese oxides and hence on the NO conversions of MnOx/CNTs. The MnO2/CNTs prepared by the low-temperature liquid method could obtain high manganese valence and amorphous structure, and the NO conversions could reach 100% at 140℃ when the Mn/C moler ratio was 6%.On the basis of the above experiments, the 6% MnO2/CNTs catalyst was loaded on the PPS filter materials by three different methods. SEM, permeability test, bond strength test and catalytic activity test were used to investigate the properties of the composite filter materials. The composite filter material prepared by the surfactant dispersion method showed strong bond strength but low NO conversions, and the catalyst loading was limited by the hydroscopicity of the PPS filter material. The composite filter material prepared by the coating method showed high NO conversions but bad bond strength, and the permeability of the composite filter material was also bad. Finally, the composite filter material prepared by suction filtration method showed high NO conversions and strong bond strength, however, the permeability was the worst in these composite materials.The surface of PPS filter material was functionalized by HNO3 and dopamine, respectively. SEM, FTIR and tensile strength test found that PPS filter material treated by HNO3 showed serious damage on the structure. However, the filter material functionalized by dopamine was coated by a layer of polydopamine which could serve as a versatile platform for secondary reactions. After in situ reaction with KMnO4, the PPS filter material functionalized by dopamine was supported by a layer of MnO2 catalysts. The catalytic activity test showed this composite filter material could obtain 62% NO conversions at 180℃. Besides, the permeability, bond strength and catalytic stability of this kind of composite filter material were good.MnO2/Polypyrrole composites were coated on the surface of PPS filter materials by the interfacial polymerization technique, and it was found that the PPS fiber surface was covered by a layer of MnO2 nanorod which was produced at the same of forming PPy. Herein, the PPy was not only as dispersant, but also as binder. The catalytic activity test showed this composite filter material could obtain 80% NO conversions at 180℃. Besides, the permeability, bond strength and catalytic stability of this kind of composite filter material were very good.Amorphous MnO2 catalysts were directly supported on PPS filter material by ultrasonic method, and the composite filter material was then coated by mean of a surface sol-gel process. It was found that an improve was not only took place on the NO conversions, but also on the permeability, bond strength and catalytic stability of this composite filter material. The more acid sites provided by TiO2 gel film could be the main reason for the improvement of NO conversions on the composite, filter material.