Login In
2014 Volume 42 Issue 6
2014, 42(6): 641-649
Abstract:
Fast pyrolysis of Huolinhe lignite was carried out under pressure in a tubular reactor, and the CH4 evolution at CO atmosphere was examined. CO dissociation state O(a) adsorbed on coal is an active center. The stronger electronegative O could induce the electron cloud of other atoms around O(a) atom to offset to it, which could weaken the strength of original chemical bonds and promote their breaking. These result in the cracks of the aromatic ring, side chain, ether linkages and aliphatic chain in the char, which could produce more free radicals. The free radicals could stabilize the fragments produced in the pyrolysis, and lead to more CH4 generated and involved. Therefore, the CH4 yield is higher under CO than it in N2. The CH4 yield increases by 12.5% under CO compared with N2 at 900 ℃ and 1.0 MPa. The CH4 yield increases with raise of temperature and pressure.
Fast pyrolysis of Huolinhe lignite was carried out under pressure in a tubular reactor, and the CH4 evolution at CO atmosphere was examined. CO dissociation state O(a) adsorbed on coal is an active center. The stronger electronegative O could induce the electron cloud of other atoms around O(a) atom to offset to it, which could weaken the strength of original chemical bonds and promote their breaking. These result in the cracks of the aromatic ring, side chain, ether linkages and aliphatic chain in the char, which could produce more free radicals. The free radicals could stabilize the fragments produced in the pyrolysis, and lead to more CH4 generated and involved. Therefore, the CH4 yield is higher under CO than it in N2. The CH4 yield increases by 12.5% under CO compared with N2 at 900 ℃ and 1.0 MPa. The CH4 yield increases with raise of temperature and pressure.
2014, 42(6): 650-655
Abstract:
3 low rank coals were dewatered and upgraded by hydrothermal process at 200, 250 and 300 ℃. Nitrogen adsorption measurements and FT-IR spectra of the parent and upgraded coals were performed to get the change of pore distribution and functional groups. After hydrothermal treatment, the average pore diameter and specific pore volume drop rapidly. The content of hydroxyl and carboxyl decreases and the cyclized degree increases. The monocyclic aromatics change into polycyclic aromatics and the organic matter in coal is gradually mature, which reflect the coal rank becomes higher. Then, rapid pyrolysis were carried out in a CDS5000 Pyroprobe accompanied by a GC/MS at 5 000 ℃/s, 1 000 ℃ to investigate the release characteristics of macromolecular volatile products of these coals. With the final reaction temperature increasing, the content of aliphatic hydrocarbon, acids and phenols decreases, that of aromatic hydrocarbon increases. The esters in coals have no obvious variation law.
3 low rank coals were dewatered and upgraded by hydrothermal process at 200, 250 and 300 ℃. Nitrogen adsorption measurements and FT-IR spectra of the parent and upgraded coals were performed to get the change of pore distribution and functional groups. After hydrothermal treatment, the average pore diameter and specific pore volume drop rapidly. The content of hydroxyl and carboxyl decreases and the cyclized degree increases. The monocyclic aromatics change into polycyclic aromatics and the organic matter in coal is gradually mature, which reflect the coal rank becomes higher. Then, rapid pyrolysis were carried out in a CDS5000 Pyroprobe accompanied by a GC/MS at 5 000 ℃/s, 1 000 ℃ to investigate the release characteristics of macromolecular volatile products of these coals. With the final reaction temperature increasing, the content of aliphatic hydrocarbon, acids and phenols decreases, that of aromatic hydrocarbon increases. The esters in coals have no obvious variation law.
2014, 42(6): 656-661
Abstract:
A series of asphaltenes were prepared by the direct liquefaction of Shengli lignite under different conditions in this paper. Their structures and compositions were characterized by elemental analysis, FT-IR spectroscopy, UV-vis spectroscopy and Fluorescent spectroscopy. The influences of initial pressure of H2 and liquefaction temperature on the structure of asphaltene were also discussed. The results indicate that Shengli lignite displays high conversion of liquefaction, and low yield of heavy intermediates such as asphaltene and preasphaltene. The aromatic systems mainly consist of 2~3 rings condensed nucleus and multi-phenyl compounds. To increase the initial pressure of H2 can promote the hydro-cracking of coal matrix and the removal of hydroxyl group by hydrogenation. High temperature and high pressure of H2 is favorable for the hydro-cracking of the substituent in AS. By contrast, the fluorescent spectroscopy is an effective technique to characterize the aromatic nucleus of asphaltne. The results characterized by the fluorescence spectra of asphaltene are relation with its H/C atomic ratio.
A series of asphaltenes were prepared by the direct liquefaction of Shengli lignite under different conditions in this paper. Their structures and compositions were characterized by elemental analysis, FT-IR spectroscopy, UV-vis spectroscopy and Fluorescent spectroscopy. The influences of initial pressure of H2 and liquefaction temperature on the structure of asphaltene were also discussed. The results indicate that Shengli lignite displays high conversion of liquefaction, and low yield of heavy intermediates such as asphaltene and preasphaltene. The aromatic systems mainly consist of 2~3 rings condensed nucleus and multi-phenyl compounds. To increase the initial pressure of H2 can promote the hydro-cracking of coal matrix and the removal of hydroxyl group by hydrogenation. High temperature and high pressure of H2 is favorable for the hydro-cracking of the substituent in AS. By contrast, the fluorescent spectroscopy is an effective technique to characterize the aromatic nucleus of asphaltne. The results characterized by the fluorescence spectra of asphaltene are relation with its H/C atomic ratio.
2014, 42(6): 662-670
Abstract:
The acid pickling and demineralization for vitrain samples of fat coal, coking coal, lean coal and meager coal from 8# coal seam of Taiyuan Xishan, China was accomplished. Meanwhile, both the trace elements testing and curve fitting of infrared spectra of the samples were carried out. It shows that correlation between some of organic group and trace elements in vitrain may be positive changes, or negative changes, or they suddenly be positive or negative with the deepening of coal metamorphism. Accordingly, organic structure-groups in coal can be divided into three types: affinity organic groups for trace elements, abhorred organic groups for trace elements and the neutral organic groups which neither affinity nor abhorred for trace elements. It is discovered that the mutual selection is very intense between organic groups and trace elements in vitrain. Whether typical affinity organic groups or typical abhorred one for trace elements, their change of affinity or abhorred are all abide by a common law, namely, the element periodic law. Even if neutral ones, its tendency of affinity or abhorred for lithophile element, chalcophile and siderophile elements are obviously different.
The acid pickling and demineralization for vitrain samples of fat coal, coking coal, lean coal and meager coal from 8# coal seam of Taiyuan Xishan, China was accomplished. Meanwhile, both the trace elements testing and curve fitting of infrared spectra of the samples were carried out. It shows that correlation between some of organic group and trace elements in vitrain may be positive changes, or negative changes, or they suddenly be positive or negative with the deepening of coal metamorphism. Accordingly, organic structure-groups in coal can be divided into three types: affinity organic groups for trace elements, abhorred organic groups for trace elements and the neutral organic groups which neither affinity nor abhorred for trace elements. It is discovered that the mutual selection is very intense between organic groups and trace elements in vitrain. Whether typical affinity organic groups or typical abhorred one for trace elements, their change of affinity or abhorred are all abide by a common law, namely, the element periodic law. Even if neutral ones, its tendency of affinity or abhorred for lithophile element, chalcophile and siderophile elements are obviously different.
2014, 42(6): 671-676
Abstract:
The modification of biomass fuel gas was studied in a fixed reactor with a certain amount of molten salts. The effects of temperature, static liquid height and superficial gas velocity on the outlet gas composition, the NaOH consumption, and the saturable absorption time of molten salts were investigated. The results show that the NaOH consumption increases from 59% to 83% and the biogas handling volume per unit molten salts is enhanced from 0.42 m3/kg to 0.48 m3/kg by elevating the temperature from 400 to 600 ℃. The CO conversion and the H2/CO volume ratio of outlet gas both increase with the increasing of temperature and static liquid height, and decrease with the increasing of superficial gas velocity.
The modification of biomass fuel gas was studied in a fixed reactor with a certain amount of molten salts. The effects of temperature, static liquid height and superficial gas velocity on the outlet gas composition, the NaOH consumption, and the saturable absorption time of molten salts were investigated. The results show that the NaOH consumption increases from 59% to 83% and the biogas handling volume per unit molten salts is enhanced from 0.42 m3/kg to 0.48 m3/kg by elevating the temperature from 400 to 600 ℃. The CO conversion and the H2/CO volume ratio of outlet gas both increase with the increasing of temperature and static liquid height, and decrease with the increasing of superficial gas velocity.
2014, 42(6): 677-682
Abstract:
Oxidative degradation of lignin for producing monophenolic compounds was carried out under microwave irradiation, with H2O2, CuO and Fe2(SO4)3 as the oxidants. The results indicated that the yield of monophenolic compounds and degradation rate of lignin feed reach 11.86% and 90.88%, respectively, under the relatively benign conditions of 180 ℃. Oxidative degradation of lignin with H2O2 as a single oxidant gives a high degradation rate but a lower yield of monophenolic compounds, due to the aromatic ring opening reaction; however, Cu2+ present in the oxidant system is able to promote the cleavage of side chain and ether bond, whereas Fe3+ to enhance the oxidation ability of H2O2, which are then conducive to improving the yield of monophenolic compounds. A moderate increase of degradation temperature and reaction time are favorable for improving the yield of monophenolic compounds. Owing to the coexistence of lignin degradation and recondensation of degraded fragments, the prevention of degraded lignin from recondensation turns to be a key issue to achieve a high yield of monophenolic compounds.
Oxidative degradation of lignin for producing monophenolic compounds was carried out under microwave irradiation, with H2O2, CuO and Fe2(SO4)3 as the oxidants. The results indicated that the yield of monophenolic compounds and degradation rate of lignin feed reach 11.86% and 90.88%, respectively, under the relatively benign conditions of 180 ℃. Oxidative degradation of lignin with H2O2 as a single oxidant gives a high degradation rate but a lower yield of monophenolic compounds, due to the aromatic ring opening reaction; however, Cu2+ present in the oxidant system is able to promote the cleavage of side chain and ether bond, whereas Fe3+ to enhance the oxidation ability of H2O2, which are then conducive to improving the yield of monophenolic compounds. A moderate increase of degradation temperature and reaction time are favorable for improving the yield of monophenolic compounds. Owing to the coexistence of lignin degradation and recondensation of degraded fragments, the prevention of degraded lignin from recondensation turns to be a key issue to achieve a high yield of monophenolic compounds.
2014, 42(6): 683-689
Abstract:
The solid base catalyst K2CO3/Al2O3 was prepared by impregnation method. The factors to influence the reaction activity of producing biodiesel from waste cooking oil including the loading of active component K2CO3 on the catalyst, the roasting temperature and the roasting time were investigated. The catalysts were characterized by FT-IR, XRD, TG-DTG, SEM and BET techniques. The results show that the catalyst exhibits an excellent catalytic activity for the transesterification of waste cooking oil to biodiesel. The solid base catalyst loaded with 50% K2CO3 and calcinated at 500 ℃ for 3 h exhibits a high catalytic activity for the transesterification, and the yield of biodiesel reaches 86.70%. The characterization reveals that the catalyst activity of K2CO3/Al2O3 is associated with the formation of new crystalline phase due to the interaction between K2CO3 and Al2O3 during calcination. After the catalyst is reused for 4 times, the yield of biodiesel is still above 75%. The main quality indexes of the product can reach the biodiesel B100 standard completely.
The solid base catalyst K2CO3/Al2O3 was prepared by impregnation method. The factors to influence the reaction activity of producing biodiesel from waste cooking oil including the loading of active component K2CO3 on the catalyst, the roasting temperature and the roasting time were investigated. The catalysts were characterized by FT-IR, XRD, TG-DTG, SEM and BET techniques. The results show that the catalyst exhibits an excellent catalytic activity for the transesterification of waste cooking oil to biodiesel. The solid base catalyst loaded with 50% K2CO3 and calcinated at 500 ℃ for 3 h exhibits a high catalytic activity for the transesterification, and the yield of biodiesel reaches 86.70%. The characterization reveals that the catalyst activity of K2CO3/Al2O3 is associated with the formation of new crystalline phase due to the interaction between K2CO3 and Al2O3 during calcination. After the catalyst is reused for 4 times, the yield of biodiesel is still above 75%. The main quality indexes of the product can reach the biodiesel B100 standard completely.
2014, 42(6): 690-696
Abstract:
Using the potassium fluoride as the active site and the carbide slag as the carrier, a calcium-based loaded catalyst for the transesterification was prepared through the impregnation method. The catalyst was characterized by X-ray fluorescence, thermogravimetric analysis, X-ray diffraction, nitrogen adsorption and desorption, scanning electron microscope and Hammett indicator. Also, the composition of peanut oil was analyzed by gas chromatograph. Then, the performance of prepared catalyst in the transesterification of peanut oil with methanol was examined with a batchwise experimental system. After being loaded with potassium fluoride, the new textural phases of KCaF3, CaF2 and KF emerge. Under the condition of the catalyst addition of 5%, the transesterification temperature of 62 ℃, the transesterification time of 2 h and the molar ratio of methanol to oil of 15, the glycerol yield of 91.58% can be achieved. Compared with calcium hydroxide and unloaded carbide slag, this loaded catalyst has a better performance.
Using the potassium fluoride as the active site and the carbide slag as the carrier, a calcium-based loaded catalyst for the transesterification was prepared through the impregnation method. The catalyst was characterized by X-ray fluorescence, thermogravimetric analysis, X-ray diffraction, nitrogen adsorption and desorption, scanning electron microscope and Hammett indicator. Also, the composition of peanut oil was analyzed by gas chromatograph. Then, the performance of prepared catalyst in the transesterification of peanut oil with methanol was examined with a batchwise experimental system. After being loaded with potassium fluoride, the new textural phases of KCaF3, CaF2 and KF emerge. Under the condition of the catalyst addition of 5%, the transesterification temperature of 62 ℃, the transesterification time of 2 h and the molar ratio of methanol to oil of 15, the glycerol yield of 91.58% can be achieved. Compared with calcium hydroxide and unloaded carbide slag, this loaded catalyst has a better performance.
2014, 42(6): 697-703
Abstract:
The thermal and catalytic cracking reactions of n-octane were carried out in a temperature range of 550~650 ℃ with low conversions (x<15%) in a pulse micro-reactor over quartz and ZRP zeolite. Reaction mechanism of methane formation was analyzed. The results showed that ethylene, propylene and n-butylene were primary products and four paths contributed to methane formation in thermal cracking of n-octane. At 600 ℃, dehydrogenation of terminal C-H bond in the chain attacked by methyl radical led to methane production. Due to higher activation energy of cleavage of terminal C-C bond in octyl radical formed via dehydrogenation of central C-C bond, only methane can form at higher temperature. Protolytic cracking was predominant with relatively remarkable yield of normal paraffin in catalytic cracking of n-octane over ZRP zeolite. Methane was produced by protolytic cracking route as well. By comparison of methane formation between thermal and protolytic cracking, it revealed that methane formed through protolytic cracking below 600 ℃ while thermal cracking dominated the selectivity of methane at higher reaction temperatures.
The thermal and catalytic cracking reactions of n-octane were carried out in a temperature range of 550~650 ℃ with low conversions (x<15%) in a pulse micro-reactor over quartz and ZRP zeolite. Reaction mechanism of methane formation was analyzed. The results showed that ethylene, propylene and n-butylene were primary products and four paths contributed to methane formation in thermal cracking of n-octane. At 600 ℃, dehydrogenation of terminal C-H bond in the chain attacked by methyl radical led to methane production. Due to higher activation energy of cleavage of terminal C-C bond in octyl radical formed via dehydrogenation of central C-C bond, only methane can form at higher temperature. Protolytic cracking was predominant with relatively remarkable yield of normal paraffin in catalytic cracking of n-octane over ZRP zeolite. Methane was produced by protolytic cracking route as well. By comparison of methane formation between thermal and protolytic cracking, it revealed that methane formed through protolytic cracking below 600 ℃ while thermal cracking dominated the selectivity of methane at higher reaction temperatures.
2014, 42(6): 704-709
Abstract:
A series of Cu-ZnO-based catalysts modified with Al, Zr, and Ce for the low-temperature methanol synthesis were prepared through co-precipitation and characterized by N2 sorption, H2-TPR, CO2-TPD, N2O titration, XRD, and high-resolution TEM; the effect of various modifiers and calcination temperature on their catalytic performance in methanol synthesis at 170 ℃ was investigated. The results showed that the Cu-ZnO-based catalyst modified with ZrO2, among the various modifiers, exhibits the highest activity. Meanwhile, a lower calcination temperature is propitious to get a higher Cu dispersion, a smaller Cu crystal size, and a higher low temperature activity for methanol synthesis; as a result, the uncalcined catalyst exhibits excellent catalytic performance, with a productivity of 106.02 g/(kg·h) and a selectivity of 87.04% to methanol.
A series of Cu-ZnO-based catalysts modified with Al, Zr, and Ce for the low-temperature methanol synthesis were prepared through co-precipitation and characterized by N2 sorption, H2-TPR, CO2-TPD, N2O titration, XRD, and high-resolution TEM; the effect of various modifiers and calcination temperature on their catalytic performance in methanol synthesis at 170 ℃ was investigated. The results showed that the Cu-ZnO-based catalyst modified with ZrO2, among the various modifiers, exhibits the highest activity. Meanwhile, a lower calcination temperature is propitious to get a higher Cu dispersion, a smaller Cu crystal size, and a higher low temperature activity for methanol synthesis; as a result, the uncalcined catalyst exhibits excellent catalytic performance, with a productivity of 106.02 g/(kg·h) and a selectivity of 87.04% to methanol.
2014, 42(6): 710-718
Abstract:
Co-Ni/Al2O3 catalyst was prepared by the fusion method and used in Fischer-Tropsch synthesis (FTS). The catalysts were characterized by means of nitrogen sorption and scanning electron microscopy. The effect of some reaction conditions such as temperature, pressure and H2/CO feed ratio on the catalytic performance of Co-Ni/Al2O3 in CO hydrogenation was investigated in a fixed-bed reactor. The results indicate that the optimum reaction conditions are 250 ℃, 0.3 MPa, H2/CO feed ratio of 2.0, and GHSV of 3 000 h-1. Kinetically, the reaction rate was correlated with the Langmuir-Hinshelwood-Hougen-Watson type models. The activation energy for the best fitted model is 88.41 kJ/mol, suggesting that the intra-particle mass transport is not significant.
Co-Ni/Al2O3 catalyst was prepared by the fusion method and used in Fischer-Tropsch synthesis (FTS). The catalysts were characterized by means of nitrogen sorption and scanning electron microscopy. The effect of some reaction conditions such as temperature, pressure and H2/CO feed ratio on the catalytic performance of Co-Ni/Al2O3 in CO hydrogenation was investigated in a fixed-bed reactor. The results indicate that the optimum reaction conditions are 250 ℃, 0.3 MPa, H2/CO feed ratio of 2.0, and GHSV of 3 000 h-1. Kinetically, the reaction rate was correlated with the Langmuir-Hinshelwood-Hougen-Watson type models. The activation energy for the best fitted model is 88.41 kJ/mol, suggesting that the intra-particle mass transport is not significant.
2014, 42(6): 719-726
Abstract:
Ni/SiC and Ni-Ybx/SiC (x=2%, 4%, 6%,10%) catalysts were prepared by the impregnation method, and the performances of catalysts in the carbon dioxide reforming of methane were studied in a fixed-bed reactor.The catalysts were characterized by BET, ICP-AES, XRD, H2-TPR, TG-DTA, XPS and TEM techniques.The experimental results indicate that the appropriate addition amount of Yb is 4% to 6%.Ni-Yb4/SiC and Ni-Yb6/SiC catalysts exhibit excellent catalytic activity and stability at 800 ℃, and the conversion of CH4 and CO2 can be maintained over 90% during the 100 h testing. Yb2O3 promotor can inhibit the growth of nickel nanoparticles and reduce the amount of carbon deposition,therefore Ni-Yb/SiC catalysts show stable activity in the continuous reforming reaction.
Ni/SiC and Ni-Ybx/SiC (x=2%, 4%, 6%,10%) catalysts were prepared by the impregnation method, and the performances of catalysts in the carbon dioxide reforming of methane were studied in a fixed-bed reactor.The catalysts were characterized by BET, ICP-AES, XRD, H2-TPR, TG-DTA, XPS and TEM techniques.The experimental results indicate that the appropriate addition amount of Yb is 4% to 6%.Ni-Yb4/SiC and Ni-Yb6/SiC catalysts exhibit excellent catalytic activity and stability at 800 ℃, and the conversion of CH4 and CO2 can be maintained over 90% during the 100 h testing. Yb2O3 promotor can inhibit the growth of nickel nanoparticles and reduce the amount of carbon deposition,therefore Ni-Yb/SiC catalysts show stable activity in the continuous reforming reaction.
2014, 42(6): 727-732
Abstract:
Selective synthesis of jet fuel-range hydrocarbons (C8~18) was investigated in a fixed-bed reactor over Ru modified cobalt-based catalysts, supported on mesoporous SiO2 and microporous HZSM-5. The effect of Ru adding amount (1%~4%) and the textual and structural properties of the catalysts on Fischer-Tropsch synthesis(FTS) performance were studied. The results showed that the tailor-made Ru-Co/SiO2/HZSM-5 catalysts maintained both meso-and micro-pores. Co dispersion and reducibility at 150~750 ℃ were enhanced with the increase of Ru amount, which resulted in the increase of CO conversion. In the same time, the yield of iso-paraffins was enhanced due to the existence of microporous structure of HZSM-5. Thus CO conversion of 62.8% and yield of jet fuel-range hydrocarbons (C8~18) of 37.7%, including 10.9% of iso-paraffins, were achieved over 1% Ru modified Co/SiO2/HZSM-5. The FTS product distribution shifted to low-carbon hydrocarbons when Ru amount was higher than 2% due to the increased CO hydrogenation rate and CH4 selectivity.
Selective synthesis of jet fuel-range hydrocarbons (C8~18) was investigated in a fixed-bed reactor over Ru modified cobalt-based catalysts, supported on mesoporous SiO2 and microporous HZSM-5. The effect of Ru adding amount (1%~4%) and the textual and structural properties of the catalysts on Fischer-Tropsch synthesis(FTS) performance were studied. The results showed that the tailor-made Ru-Co/SiO2/HZSM-5 catalysts maintained both meso-and micro-pores. Co dispersion and reducibility at 150~750 ℃ were enhanced with the increase of Ru amount, which resulted in the increase of CO conversion. In the same time, the yield of iso-paraffins was enhanced due to the existence of microporous structure of HZSM-5. Thus CO conversion of 62.8% and yield of jet fuel-range hydrocarbons (C8~18) of 37.7%, including 10.9% of iso-paraffins, were achieved over 1% Ru modified Co/SiO2/HZSM-5. The FTS product distribution shifted to low-carbon hydrocarbons when Ru amount was higher than 2% due to the increased CO hydrogenation rate and CH4 selectivity.
2014, 42(6): 733-737
Abstract:
The Ni2P/MCM-41 catalysts was prepared at low reduction temperature by temperature programmed reduction. The catalyst was characterized by H2-TPR, TG-DTG, XRD, BET, and XPS. The effects of reduction temperature on formation of the active Ni2P phase and HDS performance of the catalysts were studied. The results showed that a pure Ni2P phase can be obtained with samples reduced at low reduction temperature range of 210~390 ℃. The catalyst obtained at reduction temperature of 390 ℃ exhibited the highest HDS activity. At a reaction temperature of 340 ℃, pressure of 3.0 MPa, H2/oil volume ratio of 500, and weight hourly space velocity (WHSV) of 2.0 h-1, the DBT HDS conversion reached to 99.0%.
The Ni2P/MCM-41 catalysts was prepared at low reduction temperature by temperature programmed reduction. The catalyst was characterized by H2-TPR, TG-DTG, XRD, BET, and XPS. The effects of reduction temperature on formation of the active Ni2P phase and HDS performance of the catalysts were studied. The results showed that a pure Ni2P phase can be obtained with samples reduced at low reduction temperature range of 210~390 ℃. The catalyst obtained at reduction temperature of 390 ℃ exhibited the highest HDS activity. At a reaction temperature of 340 ℃, pressure of 3.0 MPa, H2/oil volume ratio of 500, and weight hourly space velocity (WHSV) of 2.0 h-1, the DBT HDS conversion reached to 99.0%.
Effect of the chelating agent on the hydrodesulfurization activity of extruded Co-Mo/Al2O3 catalysts
2014, 42(6): 738-742
Abstract:
γ-Al2O3 monolith support with high surface area and wide pore size distribution was obtained by extruding the mixture of pseudo boehmite and organic additives, as well as subsequent drying and calculation; a series of Co-Mo catalysts with ca. 8% molybdenum and 2% cobalt were prepared through co-impregnation of the support with solutions of ammonium heptamolybdate, cobalt nitrate and the chelating agent of citric acid (CA), oxalic acid (OA) and ethylenediamine tetraacetic acid (EDTA). The Co-Mo/Al2O3 catalysts were characterized by nitrogen sorption, XRD and H2-TPR; the effect of chelating agents on their textural properties and activity in hydrodesulphurisation (HDS) of a commercial crude benzol was investigated. The results indicated that the catalyst precursors were mostly deposited over the surface of the mesopores with a diameter between 3 and 10 nm; the addition of chelating agent results in a high dispersion of Co-Mo species on the alumina support. The H2-TPR results revealed that the addition of CA is able to improve the catalyst reducibility and shift the reduction temperature of Mo6+ to lower temperature. For the HDS reaction of the real-feedstock in a down-flow tubular reactor under 300 ℃, 3.0 MPa, a liquid hourly space velocity (LHSV) of 2 h-1, and a hydrogen/oil volume ratio of 600, the removal of thiophene sulfur reaches 99.9% over the CA-promoted Co-Mo/Al2O3 catalyst.
γ-Al2O3 monolith support with high surface area and wide pore size distribution was obtained by extruding the mixture of pseudo boehmite and organic additives, as well as subsequent drying and calculation; a series of Co-Mo catalysts with ca. 8% molybdenum and 2% cobalt were prepared through co-impregnation of the support with solutions of ammonium heptamolybdate, cobalt nitrate and the chelating agent of citric acid (CA), oxalic acid (OA) and ethylenediamine tetraacetic acid (EDTA). The Co-Mo/Al2O3 catalysts were characterized by nitrogen sorption, XRD and H2-TPR; the effect of chelating agents on their textural properties and activity in hydrodesulphurisation (HDS) of a commercial crude benzol was investigated. The results indicated that the catalyst precursors were mostly deposited over the surface of the mesopores with a diameter between 3 and 10 nm; the addition of chelating agent results in a high dispersion of Co-Mo species on the alumina support. The H2-TPR results revealed that the addition of CA is able to improve the catalyst reducibility and shift the reduction temperature of Mo6+ to lower temperature. For the HDS reaction of the real-feedstock in a down-flow tubular reactor under 300 ℃, 3.0 MPa, a liquid hourly space velocity (LHSV) of 2 h-1, and a hydrogen/oil volume ratio of 600, the removal of thiophene sulfur reaches 99.9% over the CA-promoted Co-Mo/Al2O3 catalyst.
2014, 42(6): 743-750
Abstract:
A series of Cu-SAPO-34 catalysts with various Cu contents were prepared by using different kinds of ammonium salts and adjusting Cu2+ ion exchange time; their catalytic performance and hydrothermal stability in selectively catalytic reduction of NOx with NH3 (NH3-SCR) were investigated. The results showed that Cu2+ ions are the predominant active sites in Cu-SAPO-34 for the NH3-SCR of NOx. With the increase of Cu content, the activity of Cu-SAPO-34 at low temperature is increased at first and then decreased. With a Cu content of 2.37%, the Cu-SAPO-34 catalyst exhibits the best low temperature activity; over it, the conversion of NOx is higher than 80.0% at 185 ℃ and may even reach 98.7%. ICP, H2-TPR, FT-IR and NH3-TPD results illustrated that the introduction of Cu into SAPO-34 leads to an addition of new adsorption sites for ammonia, an increase of Lewis acid sites and a decrease of the adsorption strength of NH3 on SAPO-34. However, a further increase of Cu loading (e.g. 2.90%) results in a decrease of Cu-SAPO-34 activity in SCR, which may be ascribed to the replacement of H in Si-OH-Al by Cu2+ that hinders the adsorption, storage and migration of NH3 in NH3-SCR. In addition, excessive loading of Cu is probably detrimental to the hydrothermal stability of the Cu-SAPO-34 catalyst.
A series of Cu-SAPO-34 catalysts with various Cu contents were prepared by using different kinds of ammonium salts and adjusting Cu2+ ion exchange time; their catalytic performance and hydrothermal stability in selectively catalytic reduction of NOx with NH3 (NH3-SCR) were investigated. The results showed that Cu2+ ions are the predominant active sites in Cu-SAPO-34 for the NH3-SCR of NOx. With the increase of Cu content, the activity of Cu-SAPO-34 at low temperature is increased at first and then decreased. With a Cu content of 2.37%, the Cu-SAPO-34 catalyst exhibits the best low temperature activity; over it, the conversion of NOx is higher than 80.0% at 185 ℃ and may even reach 98.7%. ICP, H2-TPR, FT-IR and NH3-TPD results illustrated that the introduction of Cu into SAPO-34 leads to an addition of new adsorption sites for ammonia, an increase of Lewis acid sites and a decrease of the adsorption strength of NH3 on SAPO-34. However, a further increase of Cu loading (e.g. 2.90%) results in a decrease of Cu-SAPO-34 activity in SCR, which may be ascribed to the replacement of H in Si-OH-Al by Cu2+ that hinders the adsorption, storage and migration of NH3 in NH3-SCR. In addition, excessive loading of Cu is probably detrimental to the hydrothermal stability of the Cu-SAPO-34 catalyst.
2014, 42(6): 751-757
Abstract:
Fe-V/TiO2 catalysts with different Fe/V molar ratio were prepared by impregnation method. The catalytic activity of selective catalytic reaction (SCR) were evaluated at the simulation of diesel exhaust environment. The samples were characterized by thermogravimetric analysis, X-ray diffraction, H2 temperature programmed reduction, NH3 temperature-programmed desorption and Raman spectra. It was found that the addition of Fe could obviously decrease the losing of V2O5 at high temperature, which greatly decreased the toxicity of the vanadium-based catalysts in mobile sources. Among the synthesized catalysts, the Fe1-V1/TiO2 showed the highest activity with the NOx conversion efficiency over 90% between 220 ℃ and 420 ℃ due to formation of FeVO4 active sites. Moreover, Fe1-V1/TiO2 exhibited excellent thermal stability at high temperature and sulfur resistance.
Fe-V/TiO2 catalysts with different Fe/V molar ratio were prepared by impregnation method. The catalytic activity of selective catalytic reaction (SCR) were evaluated at the simulation of diesel exhaust environment. The samples were characterized by thermogravimetric analysis, X-ray diffraction, H2 temperature programmed reduction, NH3 temperature-programmed desorption and Raman spectra. It was found that the addition of Fe could obviously decrease the losing of V2O5 at high temperature, which greatly decreased the toxicity of the vanadium-based catalysts in mobile sources. Among the synthesized catalysts, the Fe1-V1/TiO2 showed the highest activity with the NOx conversion efficiency over 90% between 220 ℃ and 420 ℃ due to formation of FeVO4 active sites. Moreover, Fe1-V1/TiO2 exhibited excellent thermal stability at high temperature and sulfur resistance.
2014, 42(6): 758-762
Abstract:
The reaction kinetics of ammoniade composition over La-CoMoNx/CNTs catalyst were studied. The effect of N2 concentration, H2 concentration, NH3 concentration and reaction temperature on the rate of ammonia decomposition were investigated. According to the experimental data, the correlative kinetic parameters were determined based on an exponential equation. The intrinsic kinetic equation was obtained. The activation energy of the reaction was 93.948 kJ/mol. The reaction mechanism was also discussed. The reaction rate of ammonia decomposition over La-CoMoNx/CNTs was controlled by the combination desorption of nitrogen on the surface of the catalyst.
The reaction kinetics of ammoniade composition over La-CoMoNx/CNTs catalyst were studied. The effect of N2 concentration, H2 concentration, NH3 concentration and reaction temperature on the rate of ammonia decomposition were investigated. According to the experimental data, the correlative kinetic parameters were determined based on an exponential equation. The intrinsic kinetic equation was obtained. The activation energy of the reaction was 93.948 kJ/mol. The reaction mechanism was also discussed. The reaction rate of ammonia decomposition over La-CoMoNx/CNTs was controlled by the combination desorption of nitrogen on the surface of the catalyst.
2014, 42(6): 763-768
Abstract:
Nano Pt-SnO2 anode catalyst (with a Pt/Sn atomic ratio of 3) supported on carbon fiber was synthesized via electrospinning technology. The catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM); its activity for ethanol oxidation as an anode in direct ethanol fuel cell was evaluated through cyclic voltammogram (CV). The results showed that nano Pt-SnO2 catalyst is uniformly scattered around the skeleton of vesicular carbon fiber. The carbon fiber exhibits higher density, better conductive performance with the increase of sintering temperature. The electrocatalytic test results indicated that at a sintering temperature of 800 ℃, the catalyst exhibits the best peak current density (0.11 A/cm2) and the strongest tolerance to CO. Single cell power performance test suggests that highest power generation efficiency can be achieved with an injection velocity of 1.0 mL/min with proper ethanol concentration.
Nano Pt-SnO2 anode catalyst (with a Pt/Sn atomic ratio of 3) supported on carbon fiber was synthesized via electrospinning technology. The catalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM); its activity for ethanol oxidation as an anode in direct ethanol fuel cell was evaluated through cyclic voltammogram (CV). The results showed that nano Pt-SnO2 catalyst is uniformly scattered around the skeleton of vesicular carbon fiber. The carbon fiber exhibits higher density, better conductive performance with the increase of sintering temperature. The electrocatalytic test results indicated that at a sintering temperature of 800 ℃, the catalyst exhibits the best peak current density (0.11 A/cm2) and the strongest tolerance to CO. Single cell power performance test suggests that highest power generation efficiency can be achieved with an injection velocity of 1.0 mL/min with proper ethanol concentration.
