Honghong Yi

Adsorption equilibrium and kinetics for SO2, NO, CO2 on zeolites FAU and LTA

In order to develop a single-step process for removing SO(2), NO, CO(2) in flue gas simultaneously by co-adsorption method. Pure component adsorption equilibrium and kinetics of SO(2), NO, and CO(2) on zeolite NaY, NaX, CaA were obtained respectively. Equilibrium data were analyzed by equilibrium model and Henrys law constant. The results suggest that Adsorption affinity follows the trend SO(2)>CO(2)>NO for the same adsorbent. Zeolite with stronger polar surface is a more promising adsorbent candidate. Kinetics behavior was investigated using the breakthrough curve method. The overall mass transfer coefficient and diffusivity factor were determined by a linear driving force model. The results are indicative of micropore diffusion controlling mechanism. NaY zeolite has the minimum resistance of mass transfer duo to the wide pore distribution and large pore amount. CaA zeolite exhibits the highest spatial hindered effect. Finally, co-adsorption effect of SO(2), NO, and CO(2) were investigated by multi-components breakthrough method. SO(2) and NO may form new adsorbed species, however, CO(2) presents a fast breakthrough. Chemical adsorption causes SO(2) transforms to SO(4)(2-), however, element N and C are not detected in adsorbed zeolites.

Effect of Preparation Conditions on the Property Cu/AC Adsorbents for Phosphine Adsorption

Copper-based activated carbon adsorbents (Cu/AC) were prepared and used to investigate the effects of various copper precursors, impregnation solution concentration, and calcination temperature on phosphine (PH3) adsorption removal from yellow phosphorus tail gas. N2 adsorption isotherm and X-ray Diffraction (XRD) were used for characterizing the Cu/AC adsorbents. It can be seen that the Cu(N)/AC adsorbent prepared from the Cu(NO3)2 precursor has higher PH3 breakthrough adsorption capacity than other three adsorbent because the surface copper status of it is mainly CuO. Fresh activated carbon requires an optimal impregnation solution concentration (0.05 mol/L) to reach this optimal PH3 breakthrough adsorption capacity (78.62 mg/g). The result shows that the surface chemical characteristics (Cu content) of activated carbon is more important than the physical ones (specific surface or pore volume) for the PH3 adsorption performance. When the calcination temperature is 350°C, the Cu(N)/AC adsorbent has the biggest PH3 breakthrough adsorbed amount of 112.38 mg/g. The present study confirmed that the Cu/AC adsorbents would be one of the candidates for PH3 adsorption removal from yellow phosphorus tail gas.

Preparation and Phosphine Adsorption of Activated Carbon Prepared from Walnut Shells by KOH Chemical Activation

Walnut-shell activated carbons (WSACs) with high surface area and predominant micropore development were prepared by KOH chemical activation. The effects of carbonization temperature, activation temperature, and ratio of KOH to chars on the pore development of WSACs and PH3 adsorption performance of the modified walnut-shell activated carbons (MWSACs) were studied. Criteria for determining the optimum preparation conditions were pore development of WSACs and PH3 breakthrough adsorption capacity of MWSAC adsorbents. The result shows that the optimum preparation conditions are a carbonization temperature of 700°C, an activation temperature of 700°C, and a mass ratio of 3. The BET surface area and the micropore volume of the optimal WASC are 1636m2/g and 0.641cm3/g, respectively. The micropore volume percentage of WSAC plays an important role in PH3 adsorption when there is a slight difference in BET surface areas. High-surface-area WSACs with predominant micropores are suitable for PH3 adsorption removal. The MWSAC adsorbent owns the biggest PH3 breakthrough adsorption capacity (284.12mg/g) due to the biggest specific surface area, total pore volume, and micropore volume percentage. The MWSAC adsorbent will be a potential adsorbent for PH3 adsorption removal from yellow phosphorus tail gas.

Preparation of Activated Carbons from Tobacco Stems by Potassium Hydroxide Activation and Phosphine Adsorption

Activated carbon preparation from tobacco stems by KOH activation at different activation temperatures and KOH/char mass ratios were investigated in this study. The effects of preparation parameters on activated carbon pore structure, morphometrics, microcrystallinities, and surface functional groups were characterized by N2 adsorption, SEM, XRD, and FTIR technologies, respectively. The optimum preparation condition of activated carbon was activation temperature of 850°C, and KOH/char mass ratio of 2. Under this condition, the BET surface area of 2215 m2/g, and the pore volume of 1.343 cm3/g can be obtained. Prepared activated carbon showed clearly honeycomb holes, and a predominated amorphous structure. With increase of activation temperature and KOH/char mass ratio, decrease of surface oxygen functional group, and aromatization of the carbon structure was found. The activated carbon was subject to PH3 purification, and the maximum PH3 adsorption capacity of 253 mg/g can be realized based on well prepared KOH-AC with modification of 2.5% Cu. It seems that the activated carbon produced from chemical activation of tobacco stem would be an effective and alternative adsorbent for PH3 adsorption because of its high surface area, adsorption capacity, and low cost.

Effect of Catalyst Composition on catalytic hydrolysis of COS

A series of catalysts with various Co/Ni and M 2+ /M 3+ mole ratios were prepared by decomposition of Co/Ni/Al hydrotalcite-like compounds(HTLcs) precursors at 350°C and used for hydrolysis of carbonyl sulfide(COS). The effect on the catalytic performance was investigated at 50°C and GHSV of 1000~3000 h -1 with relative humidity of 2.40%. The catalyst with Co/Ni at 0.25~0.5 and M 2+ /M 3+ at 2~3 had the best activity. The Co/Ni content barely affected the phase composition of the catalysts. The results may indicate that the Ni ion is the catalytic center, while the Co ion is the catalyst accelerator. From the SEM-EDAS analysis, the structures of catalysts with different M 2+ /M 3+ changed a lot and the various metal ions in samples were consistent with the raw material.

Catalytic Wet Air Oxidation of PH3 over CuO-CeO2 Catalysts

The influences of CeO2 and La2O3 on catalytic wet air oxidation of PH3 was investigated. CuO catalysts, CuO-CeO2 catalysts and CuO-La2O3 catalysts were prepared using the co-precipitation method. Results revealed that the purification efficiency of PH3 removed by the combination of Ce and Cu oxide was good. The catalystic activity of CuO-CeO2 catalysts influenced by the ratio of Cu to Ce was studied, the optimalizing ratio was 10:1. Main influence factors for reaction temperature, O2 content and gas flow rate were also studied, the purification efficiency of PH3 was enhanced with reaction temperature increasing, slow gas flow was good for removing PH3. O2 2% were best for the reaction. The results indicated that good conditions of the reaction were 80℃, gas flow rate of 200mL/min, O2 content of 3%.

Comparative Study on Low Temperature Selective Catalytic Oxidation of Ammonia over Transition Metals Supported on TiO2

Four different transition catalysts (V, Cr, Zn, Mo) supported on TiO2 were prepared by incipient impregnation and their performances of selective catalytic oxidation (SCO) of ammonia(NH3) were investigated in mixed gas in which 500ppm ammonia was included and the gas hourly space velocity(GHSV) was 35385h-1 . The results shown that 99% ammonia removal efficiency, 19% nitric oxide (NO) conversion and neglectable nitrogen dioxide (NO2) conversion were obtained at low temperature over Cr/TiO2. With increasing temperature, the lowest NO and NO2 conversion were found on Mo/TiO2. Then comparatively tested Cu/TiO2 and Cr/TiO2, much lower NO and NO2 conversion over Cr/TiO2 than Cu/TiO2 was obtained. Various oxygen contents ranging from 0.5% to 5% for the SCO of ammonia were as well as tested and it revealed that oxygen content affected the ammonia removal efficiency, but not as significantly as possible at low temperature, the NO and NO2 was either not affected by lean oxygen condition at low temperature.

Low Temperature Selective Catalytic Oxidation of Ammonia in Lean Oxygen over TiO2 Supported Catalyst

Selective catalytic oxidation (SCO) of ammonia to nitrogen is a promising approach for dealing with the main fixed nitrogen species. Corresponding nitrates of Fe, Cu, Ni, Co and Mn transition metals supported on TiO2 were prepared with incipient wetness impregnation and have been tested in the low temperature range from 50°C to 350°C. The catalysts were investigated under 500 ppm NH3, 2.5% O2, and gas hourly space velocity (GHSV) was 35, 000 h. The SCO of ammonia activity tests results indicated that Cu/TiO2 obtained the highest performance among catalysts, which achieved the 100% ammonia conversion at 200°C. Ni/TiO2 and Co/TiO2 have a little bit lower activity, with 100% ammonia conversion when the temperatures were 250°C and 300°C respectively. However, Mn/TiO2 and Fe/TiO2 had better selectivity into N2. The activity or selectivity of transition metals catalysts were more or less improved by introducing CeOx, especially, the activity of most catalysts were greatly increased at low

Adsorption of Phosphine in Yellow Phosphorus Tail Gas by Impregnated Activated Carbon

Phosphine (PH 3 ) is one of highly toxic air pollutants, commonly produced in phosphorous chemical industry. In order to utilize high concentration CO in yellow phosphorus tail gas, metals (Cu, Fe and Ce) loaded activated carbon adsorbents were prepared for the adsorption of PH 3 in this study. The operating conditions, such as oxygen content, adsorption temperature and space velocity, which influenced the PH 3 adsorption capacity were analyzed. The results showed that over 99% PH 3 adsorption efficiency was achieved on impregnated activated carbon. In addition, oxygen content, adsorption temperature and space velocity were important factors that influenced PH 3 adsorption removal onto impregnated activated carbon. The result showed that the maximum PH 3 adsorption capacity was 134 mg of PH 3 /g of adsorbent during the optimal operating conditions, which were 3% of oxygen content, 70°C of adsorption temperature, and 3000 h -1 of space velocity.

The Non-Thermal Plasma-Assisted Catalytic Conversion of NO under Low-Temperature

Mn-Fe catalyst was prepared by the coprecipitation method. The Mn and Fe molar ratio of this catalyst contained amorphous iron-manganese oxides was 1. The process of Non-thermal plasma-assisted catalytic oxidation of NO under low-temperature was studied. The effect of factors such as space velocity, reaction temperature and composition of mixed gas on NO removal were also investigated. The results showed that over this catalyst, NO oxidation efficiency reached 60% at 100°C and 80% at 150°C And the conversion could reach 78% with the Non-thermal plasma -assisting at 100°C. In addition, the content of nitric acid ion in distilled water was discussed.