Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M(Cu,Zn)-ammonia complexes (DMAC) at various temperatures.The catalysts were characterized in d...Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M(Cu,Zn)-ammonia complexes (DMAC) at various temperatures.The catalysts were characterized in detail,including X-ray diffraction,N2 adsorption-desorption,N2O chemisorption,temperature-programmed reduction and evolved gas analyses.The influences of DMAC temperature,reaction temperature and specific Cu surface area on catalytic performance are investigated.It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts.The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol (212 g/(Lcat·h);T=513 K,p=3MPa,SV=12000 h-1).展开更多
Oscillations in temperatures of catalyst bed as well as concentrations of gas phase species at the exit of reactor were observed during the partial oxidation of methane to synthesis gas over Ru/Al2O3 in the temperatur...Oscillations in temperatures of catalyst bed as well as concentrations of gas phase species at the exit of reactor were observed during the partial oxidation of methane to synthesis gas over Ru/Al2O3 in the temperature range of 600 to 850℃. XRD, H2-TPR and in situ Raman techniques was used to characterize the catalyst. Two types of ruthenium species, i.e. the ruthenium species weakly interacted with Al2O3 and that strongly interacted with the support, were identified by H2-TPR experiment. These species are responsible for two types of oscillation profiles observed during the reaction. The oscillations were the result of these ruthenium species switching cyclically between the oxidized state and the reduced state under the reaction condition. These cyclic transformations, in turn, were the result of temperature variations caused by the varying levels of the strongly exothermic CH4 combustion and the highly endothermic CH4 reforming (with H2O and CO2) reactions (or the less exothermic direct partial oxidation of methane to CO and H2), which were favored by the oxidized and the metallic sites, respectively. The major pathway of synthesis gas formation over the catalyst was via the combustion-reforming mechanism.展开更多
Co-Ni/Al2O3catalyst 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 react...Co-Ni/Al2O3catalyst 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/Al2O3in 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.展开更多
Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried ...Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673Ni/Al2O3-573Ni/Al2O3- 473Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2(molar ratio)=1:3,593 K,atmospheric pressure and a GHSV of 2500 h-1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%.展开更多
A series of iron-based Fischer-Tropsch synthesis (FTS) catalysts incorporated with Al2O3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characteriz...A series of iron-based Fischer-Tropsch synthesis (FTS) catalysts incorporated with Al2O3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characterized by using N2 physical adsorption, temperature-programmed reduction/desorption (TPR/TPD) and MSssbauer effect spectroscopy (MES) methods. The characterization results indicated that the BET surface area increases with increasing Al2O3 content and passes through a maximum at the Al2O3/Fe ratio of 10/100 (weight basis). After the point, it decreases with further increase in Al2O3 content. The incorporation of Al2O3 binder was found to weaken the surface basicity and suppress the reduction and carburization of iron-based catalysts probably due to the strong K-Al2O3 and Fe-Al2O3 interactions. Furthermore, the H2 adsorption ability of the catalysts is enhanced with increasing Al2O3 content. The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR) under the reaction conditions of 260 ℃, 1.5 MPa, 1000 h^-1 and molar ratio of H2/CO 0.67 for 200 h. The results showed that the addition of small amounts of Al2O3 affects the activity of iron-based catalysts to a little extent. However, with further increase of Al2O3 content, the FTS activity and water gas shift reaction (WGS) activity are decreased severely. The addition of appropriate Al2O3 do not affect the product selectivity, but the catalysts incorporated with large amounts of Al2O3 have higher selectivity for light hydrocarbons and lower selectivity for heavy hydrocarbons.展开更多
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
Characteristics of carbon deposition of CH 4 and C 2H 4 decomposition over supported Ni and Ni Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It...Characteristics of carbon deposition of CH 4 and C 2H 4 decomposition over supported Ni and Ni Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal semiconductor interaction (MScI) in the Ni Ce catalyst, and the effect of MScI on the carbon deposition of CH 4 decomposition is opposite to that of C 2H 4. A novel model of carbon deposition of CH 4 or C 2H 4 decomposition was proposed.展开更多
Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the s...Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.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 application of Co(Ⅲ)/Al2O3 catalyst in Fischer-Tropsch synthesis(FTS)was studied in a wide range of synthesis gas conversions and compared with Fuzzy Simulation results.Present study applies fuzzy model to pr...The application of Co(Ⅲ)/Al2O3 catalyst in Fischer-Tropsch synthesis(FTS)was studied in a wide range of synthesis gas conversions and compared with Fuzzy Simulation results.Present study applies fuzzy model to predicting the product composition of CH4,CO2 and CO in Fischer-Tropsch process for natural gas synthesis,in which the input vector was 4-dimension including four variables(operating pressure, operating temperature,time and CO/H2 ratio)of 70 different experiments and the output product is a composition of CO2,CO and CH4. The Mamdani algorithm has been applied to the training of the fuzzy system and the test set was used to evaluate the performance of the system including R2,ARE,AARE and SD.The results demonstrated that the predicted values from the model were in good consistency with the experimental data.The work indicates how fuzzy inference system(FIS),as a promising predicting technique,would be effectively used in FTS.展开更多
In the current study, the hybrid effect of a corona discharge and γ-alumina supported Ni catalysts in CO2 reforming of methane is investigated. The study includes both purely catalytic operation in the temperature ra...In the current study, the hybrid effect of a corona discharge and γ-alumina supported Ni catalysts in CO2 reforming of methane is investigated. The study includes both purely catalytic operation in the temperature range of 923-1023 K, and hybrid catalytic-plasma operation of DC corona discharge reactor at room temperature and ambient pressure. The effect of feed flow rate, discharge power and Ni/γ-Al2O3 catalysts are studied. When CH4/CO2 ratio in the feed is 1/2, the syngas of low Ha/CO ratio at about 0.56 is obtained, which is a potential feedstock for synthesis of liquid hydrocarbons. Although Ni catalyst is only active above 573 K, presence of Ni catalysts in the cold corona plasma reactor (T≤523 K) shows promising increase in the conversions of methane and carbon dioxide. When Ni catalysts are used in the plasma reaction, H2/CO ratios in the products are slightly modified, selectivity to CO increases whereas fewer by-products such as hydrocarbons and oxygenates are formed.展开更多
The effects of MgO promoter on the physico-chemical properties and catalytic performance of Ni/Al_(2)O_(3) catalysts for the partial oxidation of methane to syngas were studied by means of BET,XRD,H2-TPR,TEM and perfo...The effects of MgO promoter on the physico-chemical properties and catalytic performance of Ni/Al_(2)O_(3) catalysts for the partial oxidation of methane to syngas were studied by means of BET,XRD,H2-TPR,TEM and perfor-mance evaluation.It was found that the MgO promoter bene-fited from the uniformity of nickel species in the catalysts,inhibited the formation of NiAl2O4 spinel and improved the interaction between nickel species and support.These results were related to the formation of NiO–MgO solid solution and MgAl_(2)O_(4) spinel.Moreover,for the catalysts with a proper amount of MgO promoter,the nickel dispersiveness was enhanced,therefore making their catalytic performance in methane partial oxidation improved.However,the excessive MgO promoter exerted a negative effect on the catalytic performance.Meanwhile,the basicity of MgO promoted the reversed water–gas shift reaction,which led to an increase in CO selectivity and a decrease in H2 selectivity.The suitable content of MgO promoter in Ni/Al_(2)O_(3) catalyst was∼7 wt-%.展开更多
Effects of carrier gas composition(N2/air) on NH3 production, energy efficiency regarding NH3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an...Effects of carrier gas composition(N2/air) on NH3 production, energy efficiency regarding NH3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an Al2 O3-packed dielectric barrier discharge(DBD) reactor at room temperature. Results show that the presence of O2 in the carrier gas accelerates the conversion of urea but leads to less generation of NH3. The final yield of NH3 in the gas phase decreased from 70.5%, 78.7%, 66.6% and 67.2% to 54.1%, 51.7%, 49.6% and 53.4% for applied voltages of 17, 19, 21 and 23 kV, respectively when air was used as the carrier gas instead of N2.From the viewpoint of energy savings, however, air carrier gas is better than N2 due to reduced energy consumption and increased energy efficiency for decomposition of a fixed amount of urea. Carrier gas composition has little influence on the major decomposition pathways of urea under the synergetic effects of plasma and Al2 O3 catalyst to give NH3 and CO2 as the main products. Compared to a small amount of N2 O formed with N2 as the carrier gas, however,more byproducts including N2O and NO2 in the gas phase and NH4 NO3 in solid deposits were produced with air as the carrier gas, probably due to the unproductive consumption of NH3, the possible intermediate HNCO and even urea by the abundant active oxygen species and nitrogen oxides generated in air-DBD plasma.展开更多
<div style="text-align:justify;"> The rate of Methanol synthesis over a Cu/ZnO/Al<sub><span style="font-family:Verdana;">2</span></sub><span style="font-family...<div style="text-align:justify;"> The rate of Methanol synthesis over a Cu/ZnO/Al<sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> (60:30:10) catalyst has been measured using CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> (10:90) and CO/CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> (10:10:80) streams at 433, 443, 453, 463 and 473 K. Using the CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream, it requires 12 × 10</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> s to achieve </span><span style="font-family:Verdana;">steady</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">state</span><span "=""><span style="font-family:Verdana;"> performance;this time reduces to 5.4 × 10</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> s on increasing the temperature to 463 K. Using the CO/CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream, steady State performance is not achieved even after 14.4 × 10</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> s at 433 K but is achieved after 9 × 10</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> s at 463 K. Significant deviations from </span><span style="font-family:Verdana;">steady state</span><span style="font-family:Verdana;"> behavior (~40% of </span><span style="font-family:Verdana;">steady state</span><span style="font-family:Verdana;">) are observed only at 453 K and only using the CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> feed when gas chromatography (GC) is the analysis system. When the reactor output is connected directly into a flame ionization detector (FID), </span><span style="font-family:Verdana;">oscillation</span> </span><span style="font-family:Verdana;">is</span><span "=""><span style="font-family:Verdana;"> observed at all temperatures studied using a CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream. Injection of CO into the CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream, which is synthesizing methanol at 473 K, produces a sharply spiked increase in the rate of methanol synthesis followed by an oscillatory relaxation to </span><span style="font-family:Verdana;">steady state</span><span style="font-family:Verdana;"> behavior. At 433 and 443</span><span style="font-family:Verdana;"> K</span></span><span style="font-family:Verdana;">,</span><span "=""> </span><span "=""><span style="font-family:Verdana;">the injection of CO into the CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream again </span><span style="font-family:Verdana;">produce</span></span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> the sharply spiked increase in the rater of methanol synthesis, which returns to the baseline value without oscillations.</span> </div>展开更多
基金supported by the National Basic Research Program of China (No. 2011CB201404)the financial support of the State Key Laboratory for Oxo Synthesis and Selective Oxidation (OSSO) of China
文摘Methanol synthesis from hydrogenation of CO2 is investigated over Cu/ZnO/Al2O3 catalysts prepared by decomposition of M(Cu,Zn)-ammonia complexes (DMAC) at various temperatures.The catalysts were characterized in detail,including X-ray diffraction,N2 adsorption-desorption,N2O chemisorption,temperature-programmed reduction and evolved gas analyses.The influences of DMAC temperature,reaction temperature and specific Cu surface area on catalytic performance are investigated.It is considered that the aurichalcite phase in the precursor plays a key role in improving the physiochemical properties and activities of the final catalysts.The catalyst from rich-aurichalcite precursor exhibits large specific Cu surface area and high space time yield of methanol (212 g/(Lcat·h);T=513 K,p=3MPa,SV=12000 h-1).
基金supported by the Ministry of Science and Technology of China (2005CB221401)the National Natural Science Foundation of China(20873111)the Key Science & Technology Specific Projects of Fujian Province (2009HZ10102)
文摘Oscillations in temperatures of catalyst bed as well as concentrations of gas phase species at the exit of reactor were observed during the partial oxidation of methane to synthesis gas over Ru/Al2O3 in the temperature range of 600 to 850℃. XRD, H2-TPR and in situ Raman techniques was used to characterize the catalyst. Two types of ruthenium species, i.e. the ruthenium species weakly interacted with Al2O3 and that strongly interacted with the support, were identified by H2-TPR experiment. These species are responsible for two types of oscillation profiles observed during the reaction. The oscillations were the result of these ruthenium species switching cyclically between the oxidized state and the reduced state under the reaction condition. These cyclic transformations, in turn, were the result of temperature variations caused by the varying levels of the strongly exothermic CH4 combustion and the highly endothermic CH4 reforming (with H2O and CO2) reactions (or the less exothermic direct partial oxidation of methane to CO and H2), which were favored by the oxidized and the metallic sites, respectively. The major pathway of synthesis gas formation over the catalyst was via the combustion-reforming mechanism.
文摘Co-Ni/Al2O3catalyst 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/Al2O3in 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.
基金financially supported by Independent Research Subject from Ministry of Science and Technology of China(No.2008BWZ005)
文摘Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673Ni/Al2O3-573Ni/Al2O3- 473Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2(molar ratio)=1:3,593 K,atmospheric pressure and a GHSV of 2500 h-1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%.
基金The financial support from the National Natural Science Foundation of China (20590361)the National Outstanding Young Scientists Foundation of China (20625620)
文摘A series of iron-based Fischer-Tropsch synthesis (FTS) catalysts incorporated with Al2O3 binder were prepared by the combination of co-precipitation and spray drying technology. The catalyst samples were characterized by using N2 physical adsorption, temperature-programmed reduction/desorption (TPR/TPD) and MSssbauer effect spectroscopy (MES) methods. The characterization results indicated that the BET surface area increases with increasing Al2O3 content and passes through a maximum at the Al2O3/Fe ratio of 10/100 (weight basis). After the point, it decreases with further increase in Al2O3 content. The incorporation of Al2O3 binder was found to weaken the surface basicity and suppress the reduction and carburization of iron-based catalysts probably due to the strong K-Al2O3 and Fe-Al2O3 interactions. Furthermore, the H2 adsorption ability of the catalysts is enhanced with increasing Al2O3 content. The FTS performances of the catalysts were tested in a slurry-phase continuously stirred tank reactor (CSTR) under the reaction conditions of 260 ℃, 1.5 MPa, 1000 h^-1 and molar ratio of H2/CO 0.67 for 200 h. The results showed that the addition of small amounts of Al2O3 affects the activity of iron-based catalysts to a little extent. However, with further increase of Al2O3 content, the FTS activity and water gas shift reaction (WGS) activity are decreased severely. The addition of appropriate Al2O3 do not affect the product selectivity, but the catalysts incorporated with large amounts of Al2O3 have higher selectivity for light hydrocarbons and lower selectivity for heavy hydrocarbons.
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Characteristics of carbon deposition of CH 4 and C 2H 4 decomposition over supported Ni and Ni Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal semiconductor interaction (MScI) in the Ni Ce catalyst, and the effect of MScI on the carbon deposition of CH 4 decomposition is opposite to that of C 2H 4. A novel model of carbon deposition of CH 4 or C 2H 4 decomposition was proposed.
文摘Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.
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.
文摘The application of Co(Ⅲ)/Al2O3 catalyst in Fischer-Tropsch synthesis(FTS)was studied in a wide range of synthesis gas conversions and compared with Fuzzy Simulation results.Present study applies fuzzy model to predicting the product composition of CH4,CO2 and CO in Fischer-Tropsch process for natural gas synthesis,in which the input vector was 4-dimension including four variables(operating pressure, operating temperature,time and CO/H2 ratio)of 70 different experiments and the output product is a composition of CO2,CO and CH4. The Mamdani algorithm has been applied to the training of the fuzzy system and the test set was used to evaluate the performance of the system including R2,ARE,AARE and SD.The results demonstrated that the predicted values from the model were in good consistency with the experimental data.The work indicates how fuzzy inference system(FIS),as a promising predicting technique,would be effectively used in FTS.
基金supported by the National Iranian Oil Company (N.I.O.C.)
文摘In the current study, the hybrid effect of a corona discharge and γ-alumina supported Ni catalysts in CO2 reforming of methane is investigated. The study includes both purely catalytic operation in the temperature range of 923-1023 K, and hybrid catalytic-plasma operation of DC corona discharge reactor at room temperature and ambient pressure. The effect of feed flow rate, discharge power and Ni/γ-Al2O3 catalysts are studied. When CH4/CO2 ratio in the feed is 1/2, the syngas of low Ha/CO ratio at about 0.56 is obtained, which is a potential feedstock for synthesis of liquid hydrocarbons. Although Ni catalyst is only active above 573 K, presence of Ni catalysts in the cold corona plasma reactor (T≤523 K) shows promising increase in the conversions of methane and carbon dioxide. When Ni catalysts are used in the plasma reaction, H2/CO ratios in the products are slightly modified, selectivity to CO increases whereas fewer by-products such as hydrocarbons and oxygenates are formed.
文摘The effects of MgO promoter on the physico-chemical properties and catalytic performance of Ni/Al_(2)O_(3) catalysts for the partial oxidation of methane to syngas were studied by means of BET,XRD,H2-TPR,TEM and perfor-mance evaluation.It was found that the MgO promoter bene-fited from the uniformity of nickel species in the catalysts,inhibited the formation of NiAl2O4 spinel and improved the interaction between nickel species and support.These results were related to the formation of NiO–MgO solid solution and MgAl_(2)O_(4) spinel.Moreover,for the catalysts with a proper amount of MgO promoter,the nickel dispersiveness was enhanced,therefore making their catalytic performance in methane partial oxidation improved.However,the excessive MgO promoter exerted a negative effect on the catalytic performance.Meanwhile,the basicity of MgO promoted the reversed water–gas shift reaction,which led to an increase in CO selectivity and a decrease in H2 selectivity.The suitable content of MgO promoter in Ni/Al_(2)O_(3) catalyst was∼7 wt-%.
基金supported by the National Natural Science Foundation of China (Nos. 21547004, 51638001)the Beijing Natural Science Foundation (No. 8152011)the Scientific Research Program of Beijing Municipal Education Commission (No. KM201510005009)
文摘Effects of carrier gas composition(N2/air) on NH3 production, energy efficiency regarding NH3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an Al2 O3-packed dielectric barrier discharge(DBD) reactor at room temperature. Results show that the presence of O2 in the carrier gas accelerates the conversion of urea but leads to less generation of NH3. The final yield of NH3 in the gas phase decreased from 70.5%, 78.7%, 66.6% and 67.2% to 54.1%, 51.7%, 49.6% and 53.4% for applied voltages of 17, 19, 21 and 23 kV, respectively when air was used as the carrier gas instead of N2.From the viewpoint of energy savings, however, air carrier gas is better than N2 due to reduced energy consumption and increased energy efficiency for decomposition of a fixed amount of urea. Carrier gas composition has little influence on the major decomposition pathways of urea under the synergetic effects of plasma and Al2 O3 catalyst to give NH3 and CO2 as the main products. Compared to a small amount of N2 O formed with N2 as the carrier gas, however,more byproducts including N2O and NO2 in the gas phase and NH4 NO3 in solid deposits were produced with air as the carrier gas, probably due to the unproductive consumption of NH3, the possible intermediate HNCO and even urea by the abundant active oxygen species and nitrogen oxides generated in air-DBD plasma.
文摘<div style="text-align:justify;"> The rate of Methanol synthesis over a Cu/ZnO/Al<sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> (60:30:10) catalyst has been measured using CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> (10:90) and CO/CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> (10:10:80) streams at 433, 443, 453, 463 and 473 K. Using the CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream, it requires 12 × 10</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> s to achieve </span><span style="font-family:Verdana;">steady</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">state</span><span "=""><span style="font-family:Verdana;"> performance;this time reduces to 5.4 × 10</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> s on increasing the temperature to 463 K. Using the CO/CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream, steady State performance is not achieved even after 14.4 × 10</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> s at 433 K but is achieved after 9 × 10</span><sup><span style="font-family:Verdana;">3</span></sup><span style="font-family:Verdana;"> s at 463 K. Significant deviations from </span><span style="font-family:Verdana;">steady state</span><span style="font-family:Verdana;"> behavior (~40% of </span><span style="font-family:Verdana;">steady state</span><span style="font-family:Verdana;">) are observed only at 453 K and only using the CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> feed when gas chromatography (GC) is the analysis system. When the reactor output is connected directly into a flame ionization detector (FID), </span><span style="font-family:Verdana;">oscillation</span> </span><span style="font-family:Verdana;">is</span><span "=""><span style="font-family:Verdana;"> observed at all temperatures studied using a CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream. Injection of CO into the CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream, which is synthesizing methanol at 473 K, produces a sharply spiked increase in the rate of methanol synthesis followed by an oscillatory relaxation to </span><span style="font-family:Verdana;">steady state</span><span style="font-family:Verdana;"> behavior. At 433 and 443</span><span style="font-family:Verdana;"> K</span></span><span style="font-family:Verdana;">,</span><span "=""> </span><span "=""><span style="font-family:Verdana;">the injection of CO into the CO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">/H</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> stream again </span><span style="font-family:Verdana;">produce</span></span><span style="font-family:Verdana;">s</span><span style="font-family:Verdana;"> the sharply spiked increase in the rater of methanol synthesis, which returns to the baseline value without oscillations.</span> </div>