Xueqian Wang

Adsorption of low concentration phosphine in yellow phosphorus off-gas by impregnated activated carbon

In order to utilize high concentration CO comprehensively, impregnated activated carbon sorbent and the catalytic oxidation reaction for PH(3) were investigated in this study. Carbon was impregnated with HCl, KNO(3), or hexanediol. The activated carbon modified by 7% (mass fraction) HCl could enhance the adsorption purification ability significantly. Raising the reaction temperature or increasing the oxygen content of the gas can improve the purification efficiency. The structure of the materials after modification was determined using nitrogen adsorption. The modification decreased the volume of pores smaller than 2 nm in diameter with the most noticeable change occurring in the micropores ranging from 0.3 nm to 1.5 nm in diameter. Decreases in micropore volume accounted for 87% of the total pore volume change. After the adsorption, the surface areas decreased 28%, 29% of which was due to decreased micropore surface. HCl significantly increased the performance of carbon as a PH(3) adsorbent when HCl impregnation was applied whereas the effects of other materials used in this study were much less pronounced. HCl present in the small pores probably acted as a catalyst for oxygen activation that caused PH(3) oxidation. As a result of this process, H(3)PO(4) and P(4)O(10) were formed, strongly adsorbed, and present in the small pores ranging from 0.3 nm to 1.5 nm. In conclusion, this study provides evidence that CO from industrial off-gas can be purified and used as the raw material for a broader range of products.

Adsorption/desorption of low concentration of carbonyl sulfide by impregnated activated carbon under micro-oxygen conditions

Activated carbon modified with different impregnants has been studied for COS removal efficiency under micro-oxygen conditions. Activated carbon modified with Cu(NO(3))(2)-CoPcS-KOH (denoted as Cu-Co-KW) is found to have markedly enhanced adsorption purification ability. In the adsorption purification process, the reaction temperature, oxygen concentration, and relative humidity of the gas are determined to be three crucial factors. A breakthrough of 43.34 mg COS/g adsorbent at 60°С and 30% relative humidity with 1.0% oxygen is shown in Cu-Co-KW for removing COS. The structures of the activated carbon samples are characterized using nitrogen adsorption, and their surface chemical structures are analyzed with X-ray photoelectron spectroscopy (XPS). Modification of Cu(NO(3))(2)-CoPcS-KOH appears to improve the COS removal capacity significantly, during which, SO(4)(2-) is presumably formed, strongly adsorbed, and present in the micropores ranging from 0.7 to 1.5 nm. TPD is used to identify the products containing sulfur species on the carbon surface, where SO(2) and COS are detected in the effluent gas generated from exhausted Cu-Co-KW (denoted Cu-Co-KWE). According to the current study results, the activated carbon impregnated with Cu(NO(3))(2)-CoPcS-KOH promises a good candidate for COS adsorbent, with the purified gas meeting requirements for desirable chemical feed stocks.

Removing carbonyl sulfide with metal-modified activated carbon

A Cu-Co-K/activated carbon (AC) adsorbent has been developed for the removal of carbonyl sulfide (COS). The effects of COS concentration, reaction temperature and relative humidity were closely examined. A breakthrough of 33.23 mg COS·g−1 adsorbent at 60°C, under 30% relative humidity and in presence of 1.0% oxygen was exhibited in the Cu-Co-K/AC adsorbent prepared. Competitive adsorption studies for COS in the presence of CS2, and H2S were also conducted. TPD analysis was used to identify sulfur-containing products on the carbon surface, and the results indicated that H2S, COS and SO2 were all evident in the effluent gas generated from the exhausted Cu-Co-K/AC. Structure of the activated carbon samples has been characterized using nitrogen adsorption, and their surface chemical structures were also determined with X-ray photoelectron spectroscopy (XPS). It turns out that the modification with Cu(OH)2CO3-CoPcS-KOH can significantly improve the COS removal capacity, forming SO42− species simultaneously. Regeneration of the spent activated carbon sorbents by thermal desorption has also been explored.

Metal loaded zeolite adsorbents for hydrogen cyanide removal

Metal (Cu, Co, or Zn) loaded ZSM-5 and Y zeolite adsorbents were prepared for the adsorption of hydrogen cyanide (HCN) toxic gas. The results showed that the HCN breakthrough capacity was enhanced significantly when zeolites were loaded with Cu. The physical and chemical properties of the adsorbents that influence the HCN adsorption capacity were analyzed. The maximal HCN breakthrough capacities were about the same for both zeolites at 2.2 mol of HCN/mol of Cu. The Cu2p XPS spectra showed that the possible species present were Cu2O and CuO. The N1s XPS data and FT-IR spectra indicated that CN(-) would be formed in the presence of Cu+/Cu2+ and oxygen gas, and the reaction product could be adsorbed onto Cu/ZSM-5 zeolite more easily than HCN.

Adsorption of carbonyl sulfide on modified activated carbon under low-oxygen content conditions

AbstractnActivated carbon sorbents impregnated with KOH, Fe(NO3)3, Cu(NO3)2, Zn(NO3)2 or Co(NO3)2 and their applications in catalytic oxidation reaction of COS were investigated. The results showed that the activated carbon modified with 10xa0% (mass percentage) KOH enhanced the adsorption ability significantly. And it was also found that the oxygen content and temperature were the two most important factors in the COS adsorption. Further investigation on the pore structures of the samples with X-ray photoelectron spectroscopy indicated that an adsorption/oxidation process happened in the KOH modified activated carbon in which the major existing forms of sulfur were SO42− and S species. The oxidation of COS suggested that KOH in the micropores may play a catalytic role during the adsorption. On the other hand, we found that the desorption activation energy from KOHW was higher than that from AC by the CO2-TPD spectra, which indicated the adsorption of CO2 on KOH impregnated activated carbon was stronger. The strong adsorption could be attributed to the basic groups on the activated carbon surface. In conclusion, the activated carbon impregnated with KOH promises a good candidate for COS adsorbent.

Efficient removal of HCN through catalytic hydrolysis and oxidation on Cu/CoSPc/Ce metal-modified activated carbon under low oxygen conditions

The hydrogen cyanide (HCN) removal efficiency of activated carbon modified with different metal was studied under low oxygen conditions. When activated carbon was modified with Cu(NO)3, cobalt sulfonated phthalocyanine (CoSPc) and Ce(NO3)3·6H2O, its catalytic efficiency in HCN removal was significantly enhanced with the optimal conditions of 400 °C as the calcination temperature, 10% relative humidity and 1% oxygen concentration. And the catalytic hydrolysis and oxidation efficiency of AC–Cu–CoSPc–Ce was more than 98% at 200–350 °C with the maximum selectivity to N2 of 52.6% at 300 °C. Although both AC–Cu and AC–Cu–CoSPc–Ce catalysts were reliable and stable, AC–Cu–CoSPc–Ce had a better catalytic activity at lower temperature. According to BET and X-ray photoelectron spectroscopy (XPS) results, Cu was mainly in the form of CuO and Cu2O, Co was present in the form of Co2+ and Co0, and Ce was mainly in the form of CeO2 and Ce2O3 on the catalyst surface. The reaction pathways were proposed.

Removal of mercury (II), elemental mercury and arsenic from simulated flue gas by ammonium sulphide

A tubular resistance furnace was used as a reactor to simulate mercury and arsenic in smelter flue gases by heating mercury and arsenic compounds. The flue gas containing Hg2+, Hg0 and As was treated with ammonium sulphide. The experiment was conducted to investigate the effects of varying the concentration of ammonium sulphide, the pH value of ammonium sulphide, the temperature of ammonium sulphide, the presence of SO2 and the presence of sulphite ion on removal efficiency. The prepared adsorption products were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The results showed that the optimal concentration of ammonium sulphide was 0.8u2005mol/L. The optimal pH value of ammonium sulphide was 10, and the optimal temperature of ammonium sulphide was 20°C.Under the optimum conditions, the removal efficiency of Hg2+, Hg0 and As could reach 99%, 88.8%, 98%, respectively. In addition, SO2 and sulphite ion could reduce the removal efficiency of mercury and arsenic from simulated flue gas.

Adsorption of carbon disulfide on activated carbon modified by Cu and cobalt sulfonated phthalocyanine

AbstractnA series of adsorbents were studied for removal efficiency of carbon disulfide (CS2) under micro-oxygen conditions. It was found that activated carbon modified by Cu and cobalt sulfonated phthalocyanine (CoSPc) denoted as ACCu–CoSPc showed significantly enhanced adsorption ability. Reaction temperature was found to be a key factor for adsorption, and 20xa0°C seems to be optimal for CS2 removal. Samples were analyzed by N2-BET, XRD, XPS, SEM–EDS and CO2-TPD. The characterization results demonstrated that large quantities of SO42− anions were formed and adsorbed in the reaction process. SO2, CS2 and COS were detected in the effluent gas generated from the temperature programmed desorption of ACCu–CoSPc–CS2. Therefore, it can be concluded that ACCu–CoSPc most likely acted as a catalyst in the adsorption/oxidation process on the surface of the impregnated sample. The generated sulfide and sulfur oxide can cover the active sites of adsorbents, resulting in pronounced reduction of adsorbent activity. Finally, the exhausted ACCu–CoSPc can be regenerated by thermal desorption.

Ambient temperature adsorption of carbonyl sulfide using modified γ- Al 2 O 3

γ-Al₂O₃ modified with different impregnants has been studied for COS removal efficiency under micro-oxygen conditions. γ-Al₂O3 modified with 5%KOH is found to have markedly enhanced its adsorption purification ability. In the adsorption purification process, the reaction temperature and oxygen concentration of the gas are determined to be two crucial factors. After heating regeneration, the adsorption efficiency of spent sorbent (K/γ-Al₂O₃-R1 and R2) were still effective and stable. And it will be of use after heating regeneration. According to the current study results, the γ-Al₂O₃ impregnated with 5%KOH promises a good candidate for COS adsorbent.