The deactivation of Ni/SiO2-Al2 O3 catalyst in hydrogenation of crude 1,4-butanediol was investigated.During the operation time of 2140 h,the catalyst showed slow activity decay.Characterization results,for four spent...The deactivation of Ni/SiO2-Al2 O3 catalyst in hydrogenation of crude 1,4-butanediol was investigated.During the operation time of 2140 h,the catalyst showed slow activity decay.Characterization results,for four spent catalysts used at different time,indicated that the main reason of the catalyst deactivation was the deposition of carbonaceous species that covered the active Ni and blocked mesopores of the catalyst.The TPO and SEM measurements revealed that the carbonaceous species included both oligomeric and polymeric species with high C/H ratio and showed sheet.Such carbonaceous species might be eliminated through either direct H2 reduction or the combined oxidation-reduction methodologies.展开更多
The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed...The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.展开更多
Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS a...Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS analyses and they were tested in partial oxidation of methane(CPO). The catalytic reaction was carried out at atmospheric pressure in a temperature range of 400–800℃ with a feed gas mixture containing methane and oxygen in a molecular ratio CH4/O2=2. The Ni catalyst exhibited 60% methane conversion with 60% selectivity to CO already at 500℃. On the contrary, the Ni–Ce catalyst was inert to CPO up to 700℃. Moreover, the former catalyst reproduced its activity at the descending temperatures maintaining a good stability at 600℃, over a reaction time of 80 h, whereas the latter one completely deactivated. Test of CH4 temperature programmed surface reaction(CH4-TPSR) revealed a higher methane activation temperature(> 100℃) for the Ni–Ce catalyst as compared to the Ni one. Noticeable improvement of the ceria containing catalyst occurred when the reaction test started at a temperature higher than the methane decomposition temperature. In this case, the sample achieved the same catalytic behavior of the Ni catalyst. As confirmed by XPS analyses, the distinct electronic state of the supported nickel was responsible for the differences in catalytic behavior.展开更多
Ni/Al_2O_3-SiO_2 catalysts were synthesized via one-step method employing SiO_2 as an additive for the selective hydrogenation of butyne-1,4-diol(B_3D) to butane-1,4-diol(B1D). The prepared catalysts were evaluated by...Ni/Al_2O_3-SiO_2 catalysts were synthesized via one-step method employing SiO_2 as an additive for the selective hydrogenation of butyne-1,4-diol(B_3D) to butane-1,4-diol(B1D). The prepared catalysts were evaluated by a series of characterization techniques including BET, XRD, SEM, EDX-mapping, TEM, H_2-TPR, XPS, NH_3-TPD and Py-FTIR. Compared to Ni/Al_2O_3 catalyst, the SiO_2-doped samples exhibited better B_3D conversion. SiO_2 could help to form a strong interaction between NiO with the support, which inhibited Ni agglomeration at high temperature, improved the Ni dispersion, and enhanced the hydrogenation activity. B_1D selectivity was mainly influenced by the quantity of Lewis acid sites in addition to the Ni dispersion. The catalyst with a silica loading of 6.4% demonstrated an excellent selectivity of 75.18%(by 13% higher than the contrastive Ni/Al_2O_3 catalyst), which was attributed to the larger amount of Lewis acid sites and the moderate interaction between NiO with the support, which could facilitate the nickel dispersion on a preferable surface area of 176.3 m^2/g of support.展开更多
The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O...The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species （-CH2-）. Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity （GHSV）, and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.展开更多
Catalytic hydrogenation is an appropriate method for the improvement of C9 petroleum resin（C9PR） quality. In this study, the Ni2P/SiO2（containing 10% of Ni） catalyst prepared by the temperature-programmed reductio...Catalytic hydrogenation is an appropriate method for the improvement of C9 petroleum resin（C9PR） quality. In this study, the Ni2P/SiO2（containing 10% of Ni） catalyst prepared by the temperature-programmed reduction（TPR） method was used for hydrogenation of C9 petroleum resins. The effect of reaction conditions on catalytic performance was studied, and the results showed that the optimum reaction temperature, pressure and liquid hourly space velocity（LHSV） was 250 ℃, 6.0 MPa, and 1.0 h-1, respectively. The bromine numbers of hydrogenated products were maintained at low values（250 mg Br/100g） within 300h, showing the high activity and stability of Ni2P/SiO2 catalyst. The fresh and spent catalysts were characterized by X-ray diffraction（XRD）, BET surface area（BET） analysis, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, Fourier transform infrared（FTIR） pyridine adsorption, and X-ray photoelectron spectroscopy（XPS）. Compared with the traditional sulfurated-Ni W catalysts, Ni2P possessed globe-like structure instead of layered structure like the active phase of Ni WS, thereof exposing more active sites, which were responsible for the high activity of Ni2P/SiO2 catalyst. The stability of Ni2P/SiO2 catalyst was probably attributed to its high sulfur tolerance, antisintering, anti-coking and carbon-resistance ability. These properties might be further ascribed to the special Ni-P-S surface phase, high thermal stability of Ni2P nanoparticles and weak surface acidity for the Ni2P/SiO2 catalyst.展开更多
EHMO calculations and orbital analysis of fragments were performed for the Synthetic reactions of oxygenates in Fischer-Tropsch synthesis using a butterfly model for four different metals (Nim Ru, Rh, Pd)supported on ...EHMO calculations and orbital analysis of fragments were performed for the Synthetic reactions of oxygenates in Fischer-Tropsch synthesis using a butterfly model for four different metals (Nim Ru, Rh, Pd)supported on SiO2 as catalysts. Four processest CO dissociation, coupling of CO and H to produce CHO.insertion of CO to M-CH3; insertion of CH2 to M-CH3 have been calculated. We compared the degree of CO bond activation and the banters of the foregoing processes for these four catalysts, it can be shown that Ni/SiO2 is a methanation catalyst, Ru/SiO2 and Rh/SiO2 can produce C2-oxygenated compound (acetaldehyde), especially Rh/SiO2 is a good catalyst for producing it, and Pd/SiO2 is a methanol Synthesis catalyst.展开更多
This article reports the production of COx free hydrogen and carbon nanofibers by the catalytic decomposition of methane over Ni-Al2O3-SiO2 catalysts. The influence of reaction temperature, pretreatment temperature, a...This article reports the production of COx free hydrogen and carbon nanofibers by the catalytic decomposition of methane over Ni-Al2O3-SiO2 catalysts. The influence of reaction temperature, pretreatment temperature, and effect of reductive pretreatment on the decomposition of methane activity is investigated. The physico-chemical characteristics of fresh and deactivated samples were characterized using BET-SA, XRD, TPR, SEM/TEM, CHNS analyses and correlated with the methane decomposition results obtained. The Ni-Al-Si （4 ： 0.5 ： 1.5） catalyst reduced with hydrazine hydrate produced better H2 yields of ca. 1815 mol H2/mol Ni than the catalyst reduced with 5% H2/N2.展开更多
The Cu/SiO2 catalyst prepared by incipient wetness method exhibited very high activity and selectivity for the vapor-phase synthesis of N-butylaniline from aniline and 1-butanol. When Cu loading was 0.70 mmol/g-SiO2 a...The Cu/SiO2 catalyst prepared by incipient wetness method exhibited very high activity and selectivity for the vapor-phase synthesis of N-butylaniline from aniline and 1-butanol. When Cu loading was 0.70 mmol/g-SiO2 and the catalyst precursor was calcined at 500 ℃, 1-butanol conversion reached 99%, and the selectivity of N-butylaniline exceeded 97%.展开更多
基金Supported by the National Natural Science Foundation of China(21673132).
文摘The deactivation of Ni/SiO2-Al2 O3 catalyst in hydrogenation of crude 1,4-butanediol was investigated.During the operation time of 2140 h,the catalyst showed slow activity decay.Characterization results,for four spent catalysts used at different time,indicated that the main reason of the catalyst deactivation was the deposition of carbonaceous species that covered the active Ni and blocked mesopores of the catalyst.The TPO and SEM measurements revealed that the carbonaceous species included both oligomeric and polymeric species with high C/H ratio and showed sheet.Such carbonaceous species might be eliminated through either direct H2 reduction or the combined oxidation-reduction methodologies.
文摘The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.
基金The Executive Programme for Cooperation between Italy and India (Prot.No.MAE01054762017)。
文摘Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS analyses and they were tested in partial oxidation of methane(CPO). The catalytic reaction was carried out at atmospheric pressure in a temperature range of 400–800℃ with a feed gas mixture containing methane and oxygen in a molecular ratio CH4/O2=2. The Ni catalyst exhibited 60% methane conversion with 60% selectivity to CO already at 500℃. On the contrary, the Ni–Ce catalyst was inert to CPO up to 700℃. Moreover, the former catalyst reproduced its activity at the descending temperatures maintaining a good stability at 600℃, over a reaction time of 80 h, whereas the latter one completely deactivated. Test of CH4 temperature programmed surface reaction(CH4-TPSR) revealed a higher methane activation temperature(> 100℃) for the Ni–Ce catalyst as compared to the Ni one. Noticeable improvement of the ceria containing catalyst occurred when the reaction test started at a temperature higher than the methane decomposition temperature. In this case, the sample achieved the same catalytic behavior of the Ni catalyst. As confirmed by XPS analyses, the distinct electronic state of the supported nickel was responsible for the differences in catalytic behavior.
基金Financial support from the National Natural Science Foundation of China (21163019) is gratefully acknowledged
文摘Ni/Al_2O_3-SiO_2 catalysts were synthesized via one-step method employing SiO_2 as an additive for the selective hydrogenation of butyne-1,4-diol(B_3D) to butane-1,4-diol(B1D). The prepared catalysts were evaluated by a series of characterization techniques including BET, XRD, SEM, EDX-mapping, TEM, H_2-TPR, XPS, NH_3-TPD and Py-FTIR. Compared to Ni/Al_2O_3 catalyst, the SiO_2-doped samples exhibited better B_3D conversion. SiO_2 could help to form a strong interaction between NiO with the support, which inhibited Ni agglomeration at high temperature, improved the Ni dispersion, and enhanced the hydrogenation activity. B_1D selectivity was mainly influenced by the quantity of Lewis acid sites in addition to the Ni dispersion. The catalyst with a silica loading of 6.4% demonstrated an excellent selectivity of 75.18%(by 13% higher than the contrastive Ni/Al_2O_3 catalyst), which was attributed to the larger amount of Lewis acid sites and the moderate interaction between NiO with the support, which could facilitate the nickel dispersion on a preferable surface area of 176.3 m^2/g of support.
基金the National Key Project for Basic Research of China(973 Project)(No.2005CB221402)the China National Petroleum Corporation.
文摘The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species （-CH2-）. Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity （GHSV）, and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.
基金financially supported by the Scientific Research Fund of Zhejiang Provincial Education Department (Y201225114)the Natural Science Foundation of Zhejiang Province (LY13B030006)
文摘Catalytic hydrogenation is an appropriate method for the improvement of C9 petroleum resin（C9PR） quality. In this study, the Ni2P/SiO2（containing 10% of Ni） catalyst prepared by the temperature-programmed reduction（TPR） method was used for hydrogenation of C9 petroleum resins. The effect of reaction conditions on catalytic performance was studied, and the results showed that the optimum reaction temperature, pressure and liquid hourly space velocity（LHSV） was 250 ℃, 6.0 MPa, and 1.0 h-1, respectively. The bromine numbers of hydrogenated products were maintained at low values（250 mg Br/100g） within 300h, showing the high activity and stability of Ni2P/SiO2 catalyst. The fresh and spent catalysts were characterized by X-ray diffraction（XRD）, BET surface area（BET） analysis, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, Fourier transform infrared（FTIR） pyridine adsorption, and X-ray photoelectron spectroscopy（XPS）. Compared with the traditional sulfurated-Ni W catalysts, Ni2P possessed globe-like structure instead of layered structure like the active phase of Ni WS, thereof exposing more active sites, which were responsible for the high activity of Ni2P/SiO2 catalyst. The stability of Ni2P/SiO2 catalyst was probably attributed to its high sulfur tolerance, antisintering, anti-coking and carbon-resistance ability. These properties might be further ascribed to the special Ni-P-S surface phase, high thermal stability of Ni2P nanoparticles and weak surface acidity for the Ni2P/SiO2 catalyst.
文摘EHMO calculations and orbital analysis of fragments were performed for the Synthetic reactions of oxygenates in Fischer-Tropsch synthesis using a butterfly model for four different metals (Nim Ru, Rh, Pd)supported on SiO2 as catalysts. Four processest CO dissociation, coupling of CO and H to produce CHO.insertion of CO to M-CH3; insertion of CH2 to M-CH3 have been calculated. We compared the degree of CO bond activation and the banters of the foregoing processes for these four catalysts, it can be shown that Ni/SiO2 is a methanation catalyst, Ru/SiO2 and Rh/SiO2 can produce C2-oxygenated compound (acetaldehyde), especially Rh/SiO2 is a good catalyst for producing it, and Pd/SiO2 is a methanol Synthesis catalyst.
文摘This article reports the production of COx free hydrogen and carbon nanofibers by the catalytic decomposition of methane over Ni-Al2O3-SiO2 catalysts. The influence of reaction temperature, pretreatment temperature, and effect of reductive pretreatment on the decomposition of methane activity is investigated. The physico-chemical characteristics of fresh and deactivated samples were characterized using BET-SA, XRD, TPR, SEM/TEM, CHNS analyses and correlated with the methane decomposition results obtained. The Ni-Al-Si （4 ： 0.5 ： 1.5） catalyst reduced with hydrazine hydrate produced better H2 yields of ca. 1815 mol H2/mol Ni than the catalyst reduced with 5% H2/N2.
文摘The Cu/SiO2 catalyst prepared by incipient wetness method exhibited very high activity and selectivity for the vapor-phase synthesis of N-butylaniline from aniline and 1-butanol. When Cu loading was 0.70 mmol/g-SiO2 and the catalyst precursor was calcined at 500 ℃, 1-butanol conversion reached 99%, and the selectivity of N-butylaniline exceeded 97%.
