The Greenhouse Gas CO₂ Capture And The Catalytic Performance Of Polyoxometalate On CO₂ Conversion

In order to reduce the main greenhouse gas CO2 emission, countries successively put forward a low-carbon economy, and actively develop new ways of energy saving and emission reduction. Transforming the stored CO2 into syngas, hydrocarbons, alcohols, carboxylic acid and other chemical substances, can reduce CO2 emission and slow down the greenhouse effect, and the carbon source CO2 can be stored as the high value chemical products, so as to achieve the purpose of energy conservation and emission reduction. At present, the CO2 capture storage (CCS) technology can capture CO2 and store it in the equipment at source. Unified and effective CO2 conversion after enrichment is the ultimate meaning of CCS. In this paper, the ionic liquids as the main body, were supported on the molecular sieve. The CO2 adsorption performance and renewability of supported ionic liquids were investigated. Four Keggin heteropolycompounds systems were prepared (supported heteropoly acid, LnL2 rare earth heteropoly acid salt, W and V replace heteropoly acid) and used to catalyze CO2 and C3H6 directly to synthesis methacrylic acid (MAA). By the comprehensive evaluation, the optimal catalytic was selected to optimize reaction conditions.Supported functional ionic liquids for CO2 capture were prepared. The adsorbent not only keeps the good stability of ionic liquid, CO2 solubility, and green pollution-free charactieristics, but also solves the problems of low adsorption rate, non-renewable, and ionic liquid inherent liquid, which are difficult for industrial applications. According to 20%(w/w) load amount, [NH3e-mim][BF4], [OHe-mim][BF4] and [HOEAm] were supported on the molecular sieve NaY, USY, SAPO-34 and MCM-41, preparing [NH3e-mim][BF4]/NaY, [NH3e-mim][BF4]/USY, [NH3e-mim][BF4]/SAPO-34, [NH3e-mim][BF4]/MCM-41, [OHe-mim][BF4]/NaY, [OHe-mim][BF4]/USY, [OHe-mim][BF4]/SAPO-34, [OHe-mim][BF4]/MCM-41, [HOEAm]/NaY, [HOEAm]/USY, [HOEAm]/SAPO-34 and [HOEAm]/MCM-41.By comparing CO2 adsorption performance, [NH3e-mim][BF4]/NaY was found to be the best one. Carrier NaY was also investigated and no adsorption for CO2was founded, demonstrating that ionic liquid played a leading role. [NH3e-mim][BF4]/NaY was used to study the influence of temperature and ionic liquid loading amount on CO2 adsorption. The result showed the optimal temperature 20℃ and ionic liquid loading amount 20%, with the adsorption capacity 0.108mmol CO2/g SIL. Under the optimal conditions, the [NH3e-mim][BF4]/NaY recyclability was investigated. CO2 adsorption capacity increases for the first five repetitive runs and gradually reduces with the following recyclings. The adsorption capacity reaches 0.45mmolCO2/g at the fifth run and reduces to 0.29mmolCO2/g at the tenth run. The results showed that [NH3e-mim][BF4]/NaY had a good recyclability.Five kinds of Keggin structure heteropoly acid salt replaced by metal atoms,Co1.5PW12O40, (NH4) 3PW12O40, K3PW12O4o, Mn1.5PW12O40, Cu1.5PW12O40 were synthesized by corresponding sulfate. Three kinds of Keggin structure heteropoly acid salt replaced by metal atoms, Mn1.5PW12040, Cu1.5PW12O40, Co1.5PW12O40, were synthesized by corresponding nitrate, and Co1.5PW12O40 was also synthesized by CoCO3(NO3- and CO32- were introduced). The catalytic performance of different heteropoly acid salts on synthesis of MAA from CO2 and C3H6 was investigated, finding that Cu1.5PW12O40prepared from CoSO4 had the best catalysis. The introduceing NO3- and CO32- can hinder the adsorption of CO2 and C3H6 on PW12O403-, and decrease the catalysis. The effect of different molar ratio of Co and H in Keggin heteropoly acid salt, CoxH3-2xPW12O40(X=0.3,0.5,1,1.5), was also studied, indicating that Co0.5H2PW12O40 played the best catalysis for CO2 and C3H6 reaction. The influences of reaction temperature, space, velocity, feed gas ratio, pressure were studied usingCo0.5H2PW12O40 as catalyst, finding the optimal conditions was 250℃,1200-1,1.2Mpa, and excessive C3H6 could help CO2 conversion. Under the optimal conditions, CO2 conversion could reach 39%, and the selectivity of MAA was above 60%. By GC-MS and MS analysis for the collecting product, it can be found that thby-products contain ethylene glycol, acetic acid and isopropyl alcohol. The catalyst completely lost efficacy after 200min, no carbon deposition occurred in the process. The deactivation reason is due to the loss of active component.H3PW12O40、H3PMo12O40、H4SiW12O40 was supported on the molecular sieve NaY, porous silica SiO2, Al2O3, preparing H3PW12O40/NaY, H3PMo12O40/NaY, H4SiWi204o/NaY, H3PW1204o/Al203, H3PM012O40/Al2O3, H4SiW12O40/Al2O3, H3PW12O40/SiO2, H3PMo12O40/SiO2, H4SiW12O40/SiO2 by impregnation method to investigate the performance on CO2 and C3H6 reaction. The results showed that had the best catalytic performance. Compared with made by mechanical grinding of H4SiW12O40 and NaY, impregnation is superior. The conditions, such as rection temperature, space velocity, reaction pressure, H4SiW12O40 loading amount, were studied, determining the optimal reaction conditions,220℃,1200-1, 1Mpa. Under the optimal conditions, CO2 conversion could reach 24.1%, and the selectivity of MAA achieved 94.8%. The study indicated the catalytic activity remained 50min, and selectivity of MAA was above 90%.LnL2 rare earth heteropoly acid salts, K10H5[Ln(PMo5W4V2O39)2] nH2O(Ln=La, Ce, Pr, Eu, Gd, Dy), were prepared. By investigating the catalytic performance on CO2 and C3H6, it was found that K10H5[La(PMo5W4V2O39)2]·nH2O was slightly better. By XRF, FT-IR and XRD analysis, the result showed that K10H5[La(PMo5W4V2039)2]·nH2O had stable Keggin structure. Under the experimental conditions, catalyst decomposition led to deactivation, but Keggin structure did not change, and no carbon deposition occurred in the experimental process. The effect of reaction temperature, space velocity, pressure was studied with K10H5[La(PMo5W4V2039)2]·nH2O as catalyst, determining the optimal condition 220℃,1200h-1,0.5Mpa. Under the optimal condition, the CO2 conversion reached 9.48%, and the selectivity of MAA achieved 94.3%. By investigating the influence of reaction time on CO2 conversation and the selectivity of MAA, it can be seen that catalytic activity remained 60min, and selectivity of MAA was above 80%.Six kinds of W and V replace heteropoly acid, H4PWMo11O40, H5PW2Mo10O40、H6PW3Mo9O40、H4PVMo11O40、H5PV2Mo10O40、H6PV3Mo9O40, were prepared. By investigating the catalytic performance on CO2 and C3H6, it was found that W replaced series was better than V replaced series. W replaced series as research object, the number of W atom replaced Mo was studied and it was found thatHsPW2Moio04o had the best catalytic activity. The effects of reaction temperature, space velocity, pressure were studied with H5PW2Mo10O40 as catalyst, determining the optimal condition as250℃,1200h-1,1Mpa. Under the optimal condition, the CO2 conversion reached 17.78%, and the selectivity of MAA achieved 92.4%. By investigating the influence of reaction time on CO2 conversation and the selectivity of MAA, it can be seen that catalytic activity remained 50-60min, and selectivity of MAA was above 90%.