Removal Of Trace Ethylene And Other Neutral Gases Form Closed Spaces With Carbon-based Materials

Neutral gases, such as ethylene, carbon monoxide, formaldehyde, etc., exist in closed spaces of ships and aircraft carriers, which directly or indirectly affect the lives and health of the crew within vessels. Ethylene is a typical neutral gas and relatively difficult to be removed, while carbon monoxide and formaldehyde are harmful neutral gases exist in closed spaces. Based on carbon materials, mesoporous carbon spheres (MCSs) were synthesized and used as ethylene adsorbent. MCSs loaded with cobalt oxide, noble metal-graphene aerogels and metal oxides were synthesized and used as ethylene removal catalysts, and the catalytic behaviors were investigated. These catalysts were also involved in carbon monoxide or formaldehyde removal to investigate the catalytic performances for neutral gases. The main conclusions are listed as follows:(1) Research on ethylene adsorption behavior with modified mesoporous carbon spheres. MCSs synthesized by the suspension polymerization and hard template method possess fine sphericity, well-distributed particle size and high strength. After activation, the ethylene adsorption amount raises from 10.5 mL/g to 18.5 mL/g, which is mainly contributed to the increase of specific surface area and pore volume of micropores. Complexation of π bond can be formed between ethylene and adsorbent when MCSs are modified with palladium, increasing the adsorption amount to 19.4 mL/g. This series of ethylene absorbents show remarkable adsorptive property to ethylene of high concentration, with a 24.5 mL/g adsorption amount of 5000 ppm ethylene on MCS/Pd-5 (MCSs loaded with 5% Pd). The adsorbents behave well in moist gases and also show high cyclic stability.(2) Removal of ethylene by cobalt loaded mesoporous carbon spheres. A series of catalysts has been developed based on cobalt oxide supported MCSs for the catalytic combustion of ethylene. Owing to the unique and well-developed 3D mesoporous structure, the cobalt oxide could be homogenously dispersed on the carbon framework at nanoscale dimensions. The MCSs support could facilitate the oxidation ability of CoO, involving more active oxygen species on the catalyst surface. The MCS/Co-30 (MCS loaded with 30% CoO) could convert 100 ppm ethylene at 185 ℃, much lower than those catalyst carried by coconut based activated carbon, silica gel and activated alumina. The reaction order and active energy for ethylene oxidation are determined to be 0.44 and 79.2 kJ/mol, respectively.(3) Removal of ethylene by noble metal-graphene aerogel catalysts. Flexible Pt/Pd/Au-promoted graphene aerogel with high strength and low density was synthesized from suspensions of graphene oxide by a solvothermal method. A complete noble metal-graphene aerogel with metal particles uniformly dispersed could be prepared at a pH of 7 for the initial solution. The density of Pt-GA (5%Pt-promoted graphene aerogel) is only about 4 mg/mL, with high strength and high elasticity. Aerogels possess high specific surface area and pore volume, which could disperse noble metal particles and facilitate rapid mass transfer. The catalysts could removal ethylene below 100 ℃, and Pt-GA behaves best and could remove all 100 ppm ethylene at room temperature (25 ℃), which has never been reported before. Pt-GA possesses highly catalytic performance in moist conditions, converting over 90% ethylene when the relative humidity is 70%. When the loading amount of Pt declines to 1%, the catalytic efficiency of ethylene still remained over 96%.(4) The removal of ethylene by polymer-assisted metal oxide catalysts. Co/Ce catalyst and Mn/Cu catalyst with 3D network structure were prepared via a polymer-assisted chemical solution route. Ce could facilitate the dispersion of Co3O4, resulting in the Co3O4 with smaller crystallite size, higher surface area and possessing more active sites. The Co/Ce-1 (Co/Ce=1:1) catalyst possesses an excellent catalytic stability, with 100% removal of 1000 ppm ethylene at 200 ℃. Mn/Cu catalysts are consisted of Mn2O3 and CuO. The crystal grain becomes smaller when Mn and Cu are mixed, resulting in the increase of surface area, which benefits the catalytic performances. Cu/Mn-0.5 (Cu/Mn=0.5) catalyst could achieve 100% conversion of ethylene at 235 ℃, which is the lowest among this series catalysts.(5) Research of carbon monoxide and formaldehyde catalysts. Flexible Ru-graphene aerogels (Ru-GA) with high strength were synthesized, with ruthenium particles of 5-10 nm uniformly dispersed in the graphene surface. It has been shown that mild air pretreatment could switch the surface chemistry of Ru nanocrystalline, inducing the formation of highly active oxygen-vacancy RuOx. These pretreated aerogels thus could deliver 100% CO conversion with long durability at room temperature. The Co/Ce-1 could completely catalytic oxidize CO (100 ppm) at 30 ℃. It has high cycling stability, showing a catalytic commonness to both ethylene and carbon monoxide. Pt-GA could completely catalytic remove carbon monoxide and formaldehyde at room temperature. The catalytic activity of Pt-GA is much higher than commercial carbon based platinum catalyst, showing an extreme high catalytic commonness to neutral gases, such as ethylene, carbon monoxide and formaldehyde, at room temperature.