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2018 Volume 46 Issue 3
2018, 46(3): 257-264
Abstract:
Three additives (combustion coal ash, coal gasification ash and oxide mixture) with similar chemical composition were added into petcoke by dry mixing and wet mixing. Their gasification reactivities under CO2 atmosphere were investigated by a Thermo gravimetric Analyzer (TGA) at 1200-1400℃.The influence of mixing method, coal ash content and phase components on petcoke catalytic gasification was studied. The oxide mixture was used to simulate the catalytic effect of actual coal ash at high temperature. The results indicate that gasification reaction rate of petroleum coke is accelerated with increasing amount of coal ash. Dry mixing and gasification coal ash has less obvious effects on catalytic activity at 1200 and 1300℃. But the mixing method and mode of active metal has little influence on gasification reaction of petcoke at 1400℃. It is because the molten ash keeps good contact with petcoke, which makes reactive metals more freely and enhances mass transfer resistance. The catalytic index of the oxide mixtures has linear relationship with content of Fe2O3 and CaO during petcoke gasification at high temperature. This means coal ashes with high content of Fe and Ca could accelerate CO2 gasification reactivity of petcoke.
Three additives (combustion coal ash, coal gasification ash and oxide mixture) with similar chemical composition were added into petcoke by dry mixing and wet mixing. Their gasification reactivities under CO2 atmosphere were investigated by a Thermo gravimetric Analyzer (TGA) at 1200-1400℃.The influence of mixing method, coal ash content and phase components on petcoke catalytic gasification was studied. The oxide mixture was used to simulate the catalytic effect of actual coal ash at high temperature. The results indicate that gasification reaction rate of petroleum coke is accelerated with increasing amount of coal ash. Dry mixing and gasification coal ash has less obvious effects on catalytic activity at 1200 and 1300℃. But the mixing method and mode of active metal has little influence on gasification reaction of petcoke at 1400℃. It is because the molten ash keeps good contact with petcoke, which makes reactive metals more freely and enhances mass transfer resistance. The catalytic index of the oxide mixtures has linear relationship with content of Fe2O3 and CaO during petcoke gasification at high temperature. This means coal ashes with high content of Fe and Ca could accelerate CO2 gasification reactivity of petcoke.
2018, 46(3): 265-272
Abstract:
The steam gasification characteristics of Zhundong coal with additive CaO at medium temperature of 700-750℃ were investigated by Thermal Gravimetric Analyzer (TGA). The Brunauer-Emmett-Teller (BET) specific surface area of the coal char was tested by N2 adsorption, and the different occurrence modes of alkali metals in the coal were analyzed by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The results show that the soluble sodium could catalyze the gasification reaction effectively and the water-washed coal has the highest activity. The additive CaO and the inherent sodium have a synergistic effect during the gasification, and the optimal Ca/C molar ratio is 1.0. The kinetic parameters were calculated using the homogeneous model (HM), the shrinking core model (SCM) and the modified volumetric model (MVM), respectively. The results indicate that the MVM is better to represent the char steam gasification reaction, and its activation energy calculated by the MVM is 160.90 kJ/mol.
The steam gasification characteristics of Zhundong coal with additive CaO at medium temperature of 700-750℃ were investigated by Thermal Gravimetric Analyzer (TGA). The Brunauer-Emmett-Teller (BET) specific surface area of the coal char was tested by N2 adsorption, and the different occurrence modes of alkali metals in the coal were analyzed by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The results show that the soluble sodium could catalyze the gasification reaction effectively and the water-washed coal has the highest activity. The additive CaO and the inherent sodium have a synergistic effect during the gasification, and the optimal Ca/C molar ratio is 1.0. The kinetic parameters were calculated using the homogeneous model (HM), the shrinking core model (SCM) and the modified volumetric model (MVM), respectively. The results indicate that the MVM is better to represent the char steam gasification reaction, and its activation energy calculated by the MVM is 160.90 kJ/mol.
2018, 46(3): 273-282
Abstract:
Effects of temperature, atmosphere and residual carbon on melting behavior and mineral transition mechanism of fine ash from Chiping and Suqian circulating fluidized bed gasifier at high temperature was studied using fusion point analyzer, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that ash fusion temperature of two fine ash is the lowest under reducing atmosphere. The existence of mullite is the major reason for the higher ash fusion temperature of Suqian fine ash than that of Chiping. The ash fusion temperature increases with increasing mass fraction of residual carbon. When temperature is above 1300℃ and the mass fraction of residual carbon is more than 3%, moissanite is formed in slags of both fine ashes. Moissanite is mainly responsible for the worse fusibility of ash with higher content of residual carbon.
Effects of temperature, atmosphere and residual carbon on melting behavior and mineral transition mechanism of fine ash from Chiping and Suqian circulating fluidized bed gasifier at high temperature was studied using fusion point analyzer, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that ash fusion temperature of two fine ash is the lowest under reducing atmosphere. The existence of mullite is the major reason for the higher ash fusion temperature of Suqian fine ash than that of Chiping. The ash fusion temperature increases with increasing mass fraction of residual carbon. When temperature is above 1300℃ and the mass fraction of residual carbon is more than 3%, moissanite is formed in slags of both fine ashes. Moissanite is mainly responsible for the worse fusibility of ash with higher content of residual carbon.
2018, 46(3): 283-289
Abstract:
Synthetic char was used as the mineral carrier to study the characteristic of fine particulates formation during coal combustion. The silica oxide and aluminum oxide were added to synthetic char to study the interaction between sodium and common minerals in coal. The results show that the inorganic water-soluble sodium is more likely to form stable fine particles, while organic sodium is preferred to react with silica and aluminum compounds in the absence of chlorine. Chemical reactions and physical capture are two main ways for sodium capture by silica, aluminum compounds. The sodium captured through chemical reactions is 2.4 times that by physical way.
Synthetic char was used as the mineral carrier to study the characteristic of fine particulates formation during coal combustion. The silica oxide and aluminum oxide were added to synthetic char to study the interaction between sodium and common minerals in coal. The results show that the inorganic water-soluble sodium is more likely to form stable fine particles, while organic sodium is preferred to react with silica and aluminum compounds in the absence of chlorine. Chemical reactions and physical capture are two main ways for sodium capture by silica, aluminum compounds. The sodium captured through chemical reactions is 2.4 times that by physical way.
2018, 46(3): 290-297
Abstract:
Isothermal pyrolytic characteristics of PBG at 400℃ under different reaction atmospheres in a horizontal tubular quartz reactor were investigated and compared. Meanwhile, chemical structures of PBG and its pyrolysis solid products were also analyzed with the help of XPS and 13C NMR methods. The results indicate that tar yields derived from PBG pyrolysis are 50.71 and 37.45 mg/g under biomass air gasification (BAG) and N2 atmospheres, respectively, while 11.96 mg/g under BAG+2%O2 atmosphere, which indicates that the presence of oxygen can inhibit the production of tar. Furthermore, the dominant reaction is characterized as the polycondensed aromatization involving dehydrogenation and deoxygenation in PBG under BAG atmosphere, tending to the formation of heavy organic compounds such as tar. While, surface oxygen-containing organic functional groups can be generated via the oxidation reaction between some surface functional groups of PBG and O2 in PBG under BAG+2%O2 atmosphere, inhibiting the aromatization of aromatic clusters and the formation of heavy organic compounds such as tar to some extent. Thus, the introduction of a limited amount of oxygen may be helpful for solving the pipe blockage during hot gas filtration of the raw BAG gas.
Isothermal pyrolytic characteristics of PBG at 400℃ under different reaction atmospheres in a horizontal tubular quartz reactor were investigated and compared. Meanwhile, chemical structures of PBG and its pyrolysis solid products were also analyzed with the help of XPS and 13C NMR methods. The results indicate that tar yields derived from PBG pyrolysis are 50.71 and 37.45 mg/g under biomass air gasification (BAG) and N2 atmospheres, respectively, while 11.96 mg/g under BAG+2%O2 atmosphere, which indicates that the presence of oxygen can inhibit the production of tar. Furthermore, the dominant reaction is characterized as the polycondensed aromatization involving dehydrogenation and deoxygenation in PBG under BAG atmosphere, tending to the formation of heavy organic compounds such as tar. While, surface oxygen-containing organic functional groups can be generated via the oxidation reaction between some surface functional groups of PBG and O2 in PBG under BAG+2%O2 atmosphere, inhibiting the aromatization of aromatic clusters and the formation of heavy organic compounds such as tar to some extent. Thus, the introduction of a limited amount of oxygen may be helpful for solving the pipe blockage during hot gas filtration of the raw BAG gas.
2018, 46(3): 298-304
Abstract:
The allochroic silica gel was used for adsorptive denitrification from model diesel containing known amounts of quinoline, aniline or pyridine with a total nitrogen concentration 960.56 μg/g. The adsorptive removal of quinoline in model diesel with alumina, diatomite, silica gel and allochroic silica gel was investigated. The experiment results indicate that the adsorptive denitrification performance of allochroic silica gel is more superior to that of other three adsorbents, implying that the CoCl2 in allochroic silica gel can significantly improve the performance of denitrification. The silica gel and allochroic silica gel were characterized with X-ray diffraction (XRD), nitrogen adsorption and NH3-TPD. The XRD results indicate that the two samples are of an amorphous structure. Silica gel and allochroic silica gel have the average pore diameter of 18.46 and 1.80 nm, the Brunauer-Emmett-Teller (BET) surface area of 437.86 and 623.39 m2/g, and the pore volume of 0.9724 and 0.3442 m3/g, respectively. The results of NH3-TPD show that the acidity of allochroic silica gel is much stronger than that of silica gel which greatly enhances the adsorptive denitrification. Also, the influence of particle size, adsorption temperature, adsorption time, adsorbent to oil mass ratio and aromatic compounds on the adsorptive denitrification of allochroic silica gel was investigated. The adsorptive denitrification for different model diesels by allochroic silica gel is ordered as:aniline > pyridine > quinoline. Adsorption time has almost no influence on the removal of three nitrogen compounds. Adsorption temperature, particle size and aromatic compounds in the model diesel have little impact on the removal of aniline and pyridine, but have evident influences on the removal of quinoline. The adsorbent to oil ratio has a significant effect on the adsorptive denitrification, especially for quinoline. The experimental results suggest that the N-Co bond between Co in allochroic silica gel and N atom in the nitrogen compounds plays a significant role. Furthermore, the allochroic silica gel could be easily regenerated to recover its adsorptive denitrification for quinoline and pyridine by calcination once or several times, but except aniline.
The allochroic silica gel was used for adsorptive denitrification from model diesel containing known amounts of quinoline, aniline or pyridine with a total nitrogen concentration 960.56 μg/g. The adsorptive removal of quinoline in model diesel with alumina, diatomite, silica gel and allochroic silica gel was investigated. The experiment results indicate that the adsorptive denitrification performance of allochroic silica gel is more superior to that of other three adsorbents, implying that the CoCl2 in allochroic silica gel can significantly improve the performance of denitrification. The silica gel and allochroic silica gel were characterized with X-ray diffraction (XRD), nitrogen adsorption and NH3-TPD. The XRD results indicate that the two samples are of an amorphous structure. Silica gel and allochroic silica gel have the average pore diameter of 18.46 and 1.80 nm, the Brunauer-Emmett-Teller (BET) surface area of 437.86 and 623.39 m2/g, and the pore volume of 0.9724 and 0.3442 m3/g, respectively. The results of NH3-TPD show that the acidity of allochroic silica gel is much stronger than that of silica gel which greatly enhances the adsorptive denitrification. Also, the influence of particle size, adsorption temperature, adsorption time, adsorbent to oil mass ratio and aromatic compounds on the adsorptive denitrification of allochroic silica gel was investigated. The adsorptive denitrification for different model diesels by allochroic silica gel is ordered as:aniline > pyridine > quinoline. Adsorption time has almost no influence on the removal of three nitrogen compounds. Adsorption temperature, particle size and aromatic compounds in the model diesel have little impact on the removal of aniline and pyridine, but have evident influences on the removal of quinoline. The adsorbent to oil ratio has a significant effect on the adsorptive denitrification, especially for quinoline. The experimental results suggest that the N-Co bond between Co in allochroic silica gel and N atom in the nitrogen compounds plays a significant role. Furthermore, the allochroic silica gel could be easily regenerated to recover its adsorptive denitrification for quinoline and pyridine by calcination once or several times, but except aniline.
2018, 46(3): 305-310
Abstract:
An eutectic ionic liquid (EIL), choline chloride/oxalic acid, was synthesized and its structure was characterized with FT-IR spectroscopy and 1H-NMR. The denitrogenation performance of the EIL was investigated in detail using model oil and coker diesel oil as feedstock. Experimental results show that the removal efficiencies of quinoline and indole are almost 100% and 88.05%, respectively at 30℃ with the EIL to oil ratio of 1:7 (mass ratio), extraction time of 30 min and settling time of 2 h. It is also found that the choline chloride/oxalic acid presents a better denitrogenation performance for coker diesel oil, and the basic and total N-extraction efficiency can reach 96.61% and 71.5%, respectively. In addition, the basic N-removal efficiency can still reach 87.2% after four recycles of the EIL.
An eutectic ionic liquid (EIL), choline chloride/oxalic acid, was synthesized and its structure was characterized with FT-IR spectroscopy and 1H-NMR. The denitrogenation performance of the EIL was investigated in detail using model oil and coker diesel oil as feedstock. Experimental results show that the removal efficiencies of quinoline and indole are almost 100% and 88.05%, respectively at 30℃ with the EIL to oil ratio of 1:7 (mass ratio), extraction time of 30 min and settling time of 2 h. It is also found that the choline chloride/oxalic acid presents a better denitrogenation performance for coker diesel oil, and the basic and total N-extraction efficiency can reach 96.61% and 71.5%, respectively. In addition, the basic N-removal efficiency can still reach 87.2% after four recycles of the EIL.
2018, 46(3): 319-327
Abstract:
A series of honeycombed holmium-modified Fe-Mn/TiO2 catalysts were prepared by moulding method and their performance in the low temperature selective catalytic reduction (SCR) of NOx was investigated. The forming process was optimized as:the mass content of water in the forming additives is 40%, in which 10% structure strengthening agent (glass fiber), 5% binder (carboxymethyl cellulose), 10% squeezing agent (glycerin), 5% pore-forming agent (activated carbon) and a little lubricants (liquid paraffin) are added. The honeycombed Fe-Ho-Mn/TiO2 catalyst prepared under these conditions exhibits excellent performance in the low-temperature SCR of NOx; the conversion of NOx exceeds 90% at 120℃ and a good resistance to SO2 and H2O is observed when the content of SO2 in the stream is lower than 0.02%. The characterization results indicated that in comparison with the parent powder holmium-modified Fe-Ho-Mn/TiO2 catalyst, the honeycombed catalyst exhibits lower surface area, more particle aggregation, and less acid sites and Mn4+ species on the surface, which has a certain negative influence on the catalytic performance of Fe-Ho-Mn/TiO2.
A series of honeycombed holmium-modified Fe-Mn/TiO2 catalysts were prepared by moulding method and their performance in the low temperature selective catalytic reduction (SCR) of NOx was investigated. The forming process was optimized as:the mass content of water in the forming additives is 40%, in which 10% structure strengthening agent (glass fiber), 5% binder (carboxymethyl cellulose), 10% squeezing agent (glycerin), 5% pore-forming agent (activated carbon) and a little lubricants (liquid paraffin) are added. The honeycombed Fe-Ho-Mn/TiO2 catalyst prepared under these conditions exhibits excellent performance in the low-temperature SCR of NOx; the conversion of NOx exceeds 90% at 120℃ and a good resistance to SO2 and H2O is observed when the content of SO2 in the stream is lower than 0.02%. The characterization results indicated that in comparison with the parent powder holmium-modified Fe-Ho-Mn/TiO2 catalyst, the honeycombed catalyst exhibits lower surface area, more particle aggregation, and less acid sites and Mn4+ species on the surface, which has a certain negative influence on the catalytic performance of Fe-Ho-Mn/TiO2.
2018, 46(3): 328-336
Abstract:
A series of Cu/SAPO-34 catalysts for ammonia selective catalytic oxidation (NH3-SCO) were prepared by impregnation method. The results of activity test indicated that the NH3 conversion over 10%-Cu/SAPO-34 catalyst was nearly 100% at 300℃ and N2 selectivity was more than 90% in the range of test temperature. Meanwhile, the characterization results of XRD, BET, UV-vis, H2-TPR and XPS showed that the highly dispersed CuO species in Cu/SAPO-34 catalyst were the main active component. Furthermore, the aged 10%-Cu/SAPO-34 catalyst performed better NH3-SCO activity at low temperature, while the N2 selectivity dramatically decreased at 325℃, SAPO-34 zeolite crystallinity would deteriorate under hydrothermal treatment.
A series of Cu/SAPO-34 catalysts for ammonia selective catalytic oxidation (NH3-SCO) were prepared by impregnation method. The results of activity test indicated that the NH3 conversion over 10%-Cu/SAPO-34 catalyst was nearly 100% at 300℃ and N2 selectivity was more than 90% in the range of test temperature. Meanwhile, the characterization results of XRD, BET, UV-vis, H2-TPR and XPS showed that the highly dispersed CuO species in Cu/SAPO-34 catalyst were the main active component. Furthermore, the aged 10%-Cu/SAPO-34 catalyst performed better NH3-SCO activity at low temperature, while the N2 selectivity dramatically decreased at 325℃, SAPO-34 zeolite crystallinity would deteriorate under hydrothermal treatment.
2018, 46(3): 337-345
Abstract:
Bulk catalysts with different active metal atomic ratios were prepared. The effects of changing active metal tungsten, molybdenum and nickel contents on the physicochemical properties and activity of bulk catalysts were investigated using various characterization instruments, such as BET, XRD, SEM, TEM, determination of strength, packing density and laboratory scale hydrogenation apparatus. The results show that pore volume, specific surface area, pore size and the activity of ultra-deep hydrodesulfurization were all increased with the decrease of (W+Mo)/Ni ratio, while W/Mo atomic ratio remained constant. The reaction temperature reduced by 8℃ when sulfur content of refined oil is less than 10 μg/g. And the pore volume, specific surface area, pore size and ultra-deep hydrodesulfurization activity did not change obviously with increase of the W/Mo atomic ratio in the range of 0.28-1.85 while the (W+Mo)/Ni atomic ratio was kept unchanged.
Bulk catalysts with different active metal atomic ratios were prepared. The effects of changing active metal tungsten, molybdenum and nickel contents on the physicochemical properties and activity of bulk catalysts were investigated using various characterization instruments, such as BET, XRD, SEM, TEM, determination of strength, packing density and laboratory scale hydrogenation apparatus. The results show that pore volume, specific surface area, pore size and the activity of ultra-deep hydrodesulfurization were all increased with the decrease of (W+Mo)/Ni ratio, while W/Mo atomic ratio remained constant. The reaction temperature reduced by 8℃ when sulfur content of refined oil is less than 10 μg/g. And the pore volume, specific surface area, pore size and ultra-deep hydrodesulfurization activity did not change obviously with increase of the W/Mo atomic ratio in the range of 0.28-1.85 while the (W+Mo)/Ni atomic ratio was kept unchanged.
2018, 46(3): 346-354
Abstract:
(NH4)2S and Na2S were selected from several presulfiding agents. Industrial Co-Mo based sulfur-tolerant shift catalysts were ex-situ presulfided with different presulfurization technologies. The crystal structures, surface characteristics and micro appearance were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (HRTEM). (NH4)2S and Na2S as presulfiding agents did not show obvious effects on the crystal structures of the catalysts. Partial O-S exchange of the active components was observed when (NH4)2S was used for presulfirization. And when presulfided with Na2S, the active components still remained oxidation state. As the ex-situ presulfurization temperature increased, the extent of vulcanization was:S-Na2S > S-(NH4)2S > the general in situ pre-vulcanization. When presulfided with (NH4)2S or the general in situ pre-vulcanization, the stacking number of MoS2 layers was mainly two to three. And when presulfided with Na2S, the stacking number of MoS2 layers increased obviously, mostly three to five. The activity sequence of the catalysts was S-Na2S > S-(NH4)2S > the general in situ pre-vulcanization when the catalysts were tested in a micro-fixed reactor at temperatures of 285, 350 and 450℃ respectively.
(NH4)2S and Na2S were selected from several presulfiding agents. Industrial Co-Mo based sulfur-tolerant shift catalysts were ex-situ presulfided with different presulfurization technologies. The crystal structures, surface characteristics and micro appearance were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (HRTEM). (NH4)2S and Na2S as presulfiding agents did not show obvious effects on the crystal structures of the catalysts. Partial O-S exchange of the active components was observed when (NH4)2S was used for presulfirization. And when presulfided with Na2S, the active components still remained oxidation state. As the ex-situ presulfurization temperature increased, the extent of vulcanization was:S-Na2S > S-(NH4)2S > the general in situ pre-vulcanization. When presulfided with (NH4)2S or the general in situ pre-vulcanization, the stacking number of MoS2 layers was mainly two to three. And when presulfided with Na2S, the stacking number of MoS2 layers increased obviously, mostly three to five. The activity sequence of the catalysts was S-Na2S > S-(NH4)2S > the general in situ pre-vulcanization when the catalysts were tested in a micro-fixed reactor at temperatures of 285, 350 and 450℃ respectively.
2018, 46(3): 355-364
Abstract:
HZSM-5 zeolites were treated by different alkalis alone or different combining ways with two kind of alkalis to prepare micro-meso hierarchical pore HZSM-5 catalysts for thiophene alkylation reaction. The result show that mesopores are created in molecular sieves and the acidity of catalysts after treated is modulated by single alkali or different combining methods of double alkalis. Simultaneously, the structure of catalyst obtained by the separate treatment of Na2CO3 solution and TPAOH solution is most suitable for the thiophene alkylation reaction. Furthermore, the stability of the thiophene alkylation reaction over the catalyst with the best microstructure was investigated, and the reason of catalyst deactivation and the regeneration conditions were determined. The results show that the catalysts are basically inactivated after thiophene alkylation reaction for 1050 h. During the reaction, the macromolecular compounds such as olefin oligomerization formed by the cyclization, dehydrogenation and aromatics alkylation are deposited on the catalyst, blocking the pore and then covering the active site of the catalyst. From the viewpoint of the high energy consumption in regeneration at high temperature and the adverse effect of repeated high temperature regeneration on the acidity and skeleton structure of the catalyst, the catalyst should be regenerated at the temperature of 550℃.
HZSM-5 zeolites were treated by different alkalis alone or different combining ways with two kind of alkalis to prepare micro-meso hierarchical pore HZSM-5 catalysts for thiophene alkylation reaction. The result show that mesopores are created in molecular sieves and the acidity of catalysts after treated is modulated by single alkali or different combining methods of double alkalis. Simultaneously, the structure of catalyst obtained by the separate treatment of Na2CO3 solution and TPAOH solution is most suitable for the thiophene alkylation reaction. Furthermore, the stability of the thiophene alkylation reaction over the catalyst with the best microstructure was investigated, and the reason of catalyst deactivation and the regeneration conditions were determined. The results show that the catalysts are basically inactivated after thiophene alkylation reaction for 1050 h. During the reaction, the macromolecular compounds such as olefin oligomerization formed by the cyclization, dehydrogenation and aromatics alkylation are deposited on the catalyst, blocking the pore and then covering the active site of the catalyst. From the viewpoint of the high energy consumption in regeneration at high temperature and the adverse effect of repeated high temperature regeneration on the acidity and skeleton structure of the catalyst, the catalyst should be regenerated at the temperature of 550℃.
2018, 46(3): 375-384
Abstract:
A aseries of Co-doped BiFeO3 magnetic catalysts(BiFe1-xCoxO3, x=5%-20%) were synthesized by the tartaric acid sol-gel method, and the prepared catalysts were characterized using X-ray powder diffraction (XRD), Brunauer Emmett Teller (BET) technique, vibration sample magnetometer (VSM) and X ray photoelectron spectroscopy(XPS). The catalytic activity of Co doped BiFeO3 to activate Peroxymonosulfate (PMS) was evaluated at a self-designed bubbling reactor. The effects of Co ration in catalyst, dosage of the catalyst, PMS concentration, and solution pH and reaction temperature on the removal of elemental mercury were investigated systematically, and the optimum conditions were obtained. The result indicates that the average removal efficiency of elemental mercury reaches 89.36% within 100 min under the following condition:70℃, 10% doping Co, 3.9 mmol/L PMS concentration, 0.5 g/L catalyst dosage and pH 8. Moreover, it is testified that SO4·- and·OH are the active species when Hg0 is oxidized to Hg2+, where the tert-butyl alcohol and ethyl alcohol are used as quenchers. Finally, the mechanisms of mercury removal with PMS solution catalyzed by BiFe0.9Co0.1O3 are speculated on the basis of XPS results.
A aseries of Co-doped BiFeO3 magnetic catalysts(BiFe1-xCoxO3, x=5%-20%) were synthesized by the tartaric acid sol-gel method, and the prepared catalysts were characterized using X-ray powder diffraction (XRD), Brunauer Emmett Teller (BET) technique, vibration sample magnetometer (VSM) and X ray photoelectron spectroscopy(XPS). The catalytic activity of Co doped BiFeO3 to activate Peroxymonosulfate (PMS) was evaluated at a self-designed bubbling reactor. The effects of Co ration in catalyst, dosage of the catalyst, PMS concentration, and solution pH and reaction temperature on the removal of elemental mercury were investigated systematically, and the optimum conditions were obtained. The result indicates that the average removal efficiency of elemental mercury reaches 89.36% within 100 min under the following condition:70℃, 10% doping Co, 3.9 mmol/L PMS concentration, 0.5 g/L catalyst dosage and pH 8. Moreover, it is testified that SO4·- and·OH are the active species when Hg0 is oxidized to Hg2+, where the tert-butyl alcohol and ethyl alcohol are used as quenchers. Finally, the mechanisms of mercury removal with PMS solution catalyzed by BiFe0.9Co0.1O3 are speculated on the basis of XPS results.
2018, 46(3): 311-318
Abstract:
The cobalt nanoparticles over γ-Al2O3 support were prepared via chemical reduction of CoCl2·6H2O using NaBH4 with various values of pH in the range of 11.92-13.80. Synthesized catalysts were studied through X-ray diffraction (XRD), N2 adsorption/desorption (BET), H2-temperature programmed reduction (H2-TPR), H2-chemisorption, O2 pulse titration and temperature programmed oxidation (TPO) methods. Obtained results exhibited the synthesis solution pH showed a significant influence on the activity and selectivity in partial oxidation of methane reaction. The methane conversion, CO selectivity and H2 yield were enhanced by increasing of the synthesis solution pH. Compared to other catalysts, the catalyst that synthesized at pH of 13.80, showed a superior ability in syngas production with a H2/CO ratio of near 2 and also a proper stability against deactivation during the partial oxidation of methane.
The cobalt nanoparticles over γ-Al2O3 support were prepared via chemical reduction of CoCl2·6H2O using NaBH4 with various values of pH in the range of 11.92-13.80. Synthesized catalysts were studied through X-ray diffraction (XRD), N2 adsorption/desorption (BET), H2-temperature programmed reduction (H2-TPR), H2-chemisorption, O2 pulse titration and temperature programmed oxidation (TPO) methods. Obtained results exhibited the synthesis solution pH showed a significant influence on the activity and selectivity in partial oxidation of methane reaction. The methane conversion, CO selectivity and H2 yield were enhanced by increasing of the synthesis solution pH. Compared to other catalysts, the catalyst that synthesized at pH of 13.80, showed a superior ability in syngas production with a H2/CO ratio of near 2 and also a proper stability against deactivation during the partial oxidation of methane.
2018, 46(3): 365-374
Abstract:
A novel magnetic AgI-BiOI/CoFe2O4 hybrid composites were prepared via a solvothermal and subsequent coprecipitation method, and utilized to remove Hg0 from coal-fired flue gas under fluorescent light irradiation. The experimental parameters and main products presented in solution after reaction were investigated in detail. The experimental results showed that the AgI-BiOI/CoFe2O4 composites showing a poor thermal stability would transform into other compounds when the calcinated temperature was above 400℃. With the increases of photocatalyst dosage, reaction solution pH, temperature of reaction solution in reactor and O2 concentration, the Hg0 removal efficiencies were first increased and then unchanged or decreased. The presences of inorganic anions such as CO32- and SO42- in solution exhibited some inhibitory effects on Hg0 removal. Furthermore, the presence of SO2 had a dramatic inhibition on Hg0 removal, while the inhibitory effect of NO on Hg0 removal was relatively small. SO42-, NO3- and Hg2+ species were the final oxidation products of SO2, NO and Hg0 by reactive species.
A novel magnetic AgI-BiOI/CoFe2O4 hybrid composites were prepared via a solvothermal and subsequent coprecipitation method, and utilized to remove Hg0 from coal-fired flue gas under fluorescent light irradiation. The experimental parameters and main products presented in solution after reaction were investigated in detail. The experimental results showed that the AgI-BiOI/CoFe2O4 composites showing a poor thermal stability would transform into other compounds when the calcinated temperature was above 400℃. With the increases of photocatalyst dosage, reaction solution pH, temperature of reaction solution in reactor and O2 concentration, the Hg0 removal efficiencies were first increased and then unchanged or decreased. The presences of inorganic anions such as CO32- and SO42- in solution exhibited some inhibitory effects on Hg0 removal. Furthermore, the presence of SO2 had a dramatic inhibition on Hg0 removal, while the inhibitory effect of NO on Hg0 removal was relatively small. SO42-, NO3- and Hg2+ species were the final oxidation products of SO2, NO and Hg0 by reactive species.
