Dingye Fang

Effects of the ratio of Fe to Co over Fe-Co/SiO2 bimetallic catalysts on their catalytic performance for Fischer-Tropsch synthesis

Abstract The Fe-Co/SiO 2 bimetallic catalysts with different ratios of Fe to Co were prepared by aqueous incipient wetness impregnation. The catalysts of 10%Fe:0%Co/SiO 2 , 10%Fe:6%Co/SiO 2 , 10%Fe:2%Co/SiO 2 , 10%Fe:10%Co/SiO 2 , 6%Fe:10%Co/SiO 2 , 2%Fe:10%Co/SiO 2 and 0%Fe: 10%Co/SiO 2 by mass were tested in a fixed reactor by the Fischer-Tropsch synthesis. Activity and hydrocarbon distribution were found to be determined by the ratio of iron to cobalt of the catalysts. Higher iron content inhibited the activity, whereas higher cobalt content enhanced the activity of the Fe-Co/SiO 2 catalysts. On the other hand, for the catalysts of 10%Fe:6%Co/SiO 2 , 10%Fe:10%Co/SiO 2 , 6%Fe:10%Co/SiO 2 , and 2%Fe:10%Co/SiO 2 , the total C 2 –C 4 fraction increased (from 10.65% to 26.78%) and C 5+ fraction decreased (from 75.75% to 57.63%) at 523 K. Temperature programmed reduction revealed that the addition of cobalt enhanced the reducibility of the Fe-Co/SiO 2 catalyst. Metal oxides were present in those catalysts as shown by XRD. The Fe-Co alloy phase was found in the 2%Fe:10%Co/SiO 2 , 6%Fe:10%Co/SiO 2 , 10%Fe:10%Co/SiO 2 , 10%Fe:6%Co/SiO 2 catalysts and their crystals were perfect.

Mathematical Simulation and Design of Three-Phase Bubble Column Reactor for Direct Synthesis of Dimethyl Ether from Syngas

Abstract A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether (DME) from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows: diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger (ϕ 38×2 mm), and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.

Effects of the Different Supports on the Activity and Selectivity of Iron-Cobalt Bimetallic Catalyst for Fischer-Tropsch Synthesis

Abstract Silica, alumina, and activated carbon supported iron-cobalt catalysts were prepared by incipient wetness impregnation. These catalysts have been characterized by BET, X-ray diffraction (XRD), and temperature-programmed reduction (TPR). Activity and selectivity of iron-cobalt supported on different carriers for CO hydrogenation were studied under the conditions of 1.5 MPa, 493 K, 630 h −1 , and H 2 /CO ratio of 1.6. The results indicate that the activity, C 4 olefin/(C 4 olefin+C 4 paraffin) ratio, and C 5 olefin/(C 5 olefin+C 5 paraffin) decrease in the order of Fe-Co/SiO 2 , Fe-Co/AC1, Fe-Co/A1 2 O 3 and Fe-Co/AC2. The activity of Fe-Co/SiO 2 reached a maximum. The results of TPR show that the Fe-Co/SiO 2 catalyst, is to some extent different. XRD patterns show that the Fe-Co/SiO 2 catalyst differs significantly from the others; it has two diffraction peaks. The active spinel phase is correlated with the supports.

Effects of promoters on catalytic performance of Fe-Co/SiO2 catalyst for Fischer-Tropsch synthesis

Abstract 2%Fe-10%Co/SiO2 catalysts with different potassium or zirconium loadings were prepared by aqueous incipient wetness impregnation and tested for Fischer-Tropsch synthesis in a flow reactor, using H2/CO = 1.6 (molar ratio) in the feed, under the condition of an overall pressure of 1 MPa, GHSV of 600 h−1 and temperature of 503 K. The zirconium and potassium promoters remarkably influenced hydrocarbon distribution of the products. CO conversion increased on the catalysts with the increase of zirconium loadings, which indicated that zirconium enhanced the activity of iron-cobalt catalysts. Low potassium loadings also enhanced the activity of the catalysts. However, high potassium loading made CO conversion on the catalysts decrease and weakened the secondary hydrogenations. The catalyst was characterized by BET, XRD and TPR. The catalyst characterization revealed that the Co3O4 phase was presented on the fresh catalyst, whereas the spinel phase of Fe-Co alloy and CoO existed on the used catalyst.

Effects of Impregnation Solvents on Catalytic Performance of Co-Ru-ZrO2/γ-Al2O3 Catalyst for Fischer-Tropsch Synthesis

Abstract Used ZrO2 modified γ-Al2O3 as support, Co-Ru catalysts were prepared by incipient impregnation method. The effects of impregnation solvents on the performances of catalysts were examined. The catalyst was prepared with ethanol solution and high Co dispersion was obtained, exhibiting highest activity of CO hydrogenation, very low methane selectivity, and high heavy hydrocarbon C5 + selectivity. The catalysts were prepared with aqueous solution and methanol solution, and the reaction behaviors were similar. The solvent isopropanol caused the lowest catalytic activity and highest methane selectivity. Increasing the reaction temperature enhanced the CO hydrogenation rate, and the CO conversion slightly increased the CO2 selectivity and favored the formation methane and light hydrocarbons, while the chain growth probability decreased. For the catalyst prepared with ethanol, the CO conversion, the CH4 selectivity, and the C5 + selectivity were 94.16%, 5.65%, and 88.2%, respectively, and the chain growth probability was 0.87 at 493 K, 1.5 MPa, 800 h−1, and n(H2):n(CO) = 2.0 in feed.

The Reaction Kinetics of a Fischer-Tropsch Synthesis Over a Commercial Eggshell Co/SiO2 Catalyst

Abstract The comprehensive kinetic model of Fischer-Tropsch synthesis over a commercial eggshell Co/SiO2 catalyst in a fixed-bed reactor was investigated experimentally. This model was expressed in the combination of kinetic rate of CO consumption and the equation of the growth probability factor α was obtained. Through parameter evaluation and optimization, both the rate of CO consumption was given and the equation of a was obtained. It was also proved that the proposed model could predict the kinetic rate of CO consumption and the product distributions well. The appropriate operating conditions for this catalyst were concluded by the model and they were in good agreement with the results in the industrial pilot-scale research.

Intrinsic kinetics of methane aromatization under non-oxidative conditions over modified Mo/HZSM-5 catalysts

The intrinsic reaction kinetics of methane aromatization under non-oxidative conditions over modified Mo/HZSM-5 catalysts was studied in the quartz pipe-reactor under ordinary pressure with the temperature ranging from 913.15 to 973.15 K and the space velocity from 700 to 2100 ml/(g·h). The Langmuir-Hinshelwood model was chosen to describe the intrinsic kinetics while Levenberg-Marquardt method was selected to determine the parameters in the kinetic model. Statistical test and residual error distribution diagrams showed that experimental data were in good agreement with calculated data, and Langmuir-Hinshelwood model was suitable for the description of the intrinsic kinetics of methane aromatization under the reaction conditions discussed in this article.

Pretreatment of Alumina and Its Influence on the Properties of Co/Alumina Catalysts for Fischer-Tropsch Synthesis

Abstract 16.6%Co/γ-Al2O3 catalysts prepared by incipient wetness impregnation method were used for Fischer-Tropsch synthesis. The support was pre-treated with different concentration of NH4NO3 aqueous solution. The effect of support pre-treatment on the properties of support and performance of supported-cobalt-based catalysts was investigated. To treat the support with NH4NO3 aqueous solution enlarged the pore of γAl2O3, decreased the impurity Na2O content, and weakened the surface acidity of γAl2O3. The change in the properties of the support decreased the interaction between cobalt species and support, enhanced the CO hydrogenation rate and the C5+ selectivity. For all catalysts, increasing the reaction temperature increased the CO hydrogenation rate or the CO conversion, slightly decreased the total hydrocarbon selectivity, and favored the formation of methane and light hydrocarbons, while the chain growth probability decreased. For 16.6%Co/γAl2O3 catalysts, prepared with the support treated with 100 g/L NH4NO3 aqueous solution, the CO conversion, the CH4 selectivity, and the C5+ selectivity were 83.13%, 6.86% and 82.75% respectively, and the chain growth probability was 0.83 under the condition of 493 K, 1.5 MPa, 500 h−1 and the molar ratio of H2 to CO being 2.0 in feed.

Co-Ru/γ-Al2O3 Catalyst Modified With ZrO2 for Fischer-Tropsch Synthesis

Abstract Using an incipient impregnation method, a Co-Ru bimetallic catalyst was prepared. The effects of the ZrO2 modification of support on heavy hydrocarbon synthesis were investigated in a fixed-bed reactor. The results indicated that the ZrO2 modification could block defects of γ-Al2O3 crystal lattice, weaken the interaction between support and Co, and hinder or prevent the formation of cobalt aluminate. Zr reacted with Co to form the Co-Zr species, which is easily reduced under lower temperature. It caused an increase in the amount of easily reducible Co species and a decrease in the amount of uneasily reducible Co species. Then the reduction extent of cobalt-based catalyst was raised under the typical reduction condition. Meanwhile, support of γ-Al2O3 was modified with ZrO2, and the interface of Co-ZrO2 formed. The Co-ZrO2 interface led to an increase of the intensity of the bridge-form CO adsorption, which CO facilitates to be dissociated. At H2/CO molar ratio in feed 2.0, 503 K, 1.5 MPa, and 800 hr−1, the catalyst exhibited better catalytic performance. The CO conversion was 93.27%, the C5 + selectivity was 82.56%, and the chain growth factor was 0.81.