Effect of the operation parameters on the Fischer-Tropsch synthesis in fluidized bed reactors

For the Fischer-Tropsch synthesis(FTS), this paper presents a numerical investigation in a 3 D fluidized bed reactor. The effect of the operation parameters such as bed temperature, superficial gas velocities, particle size and bed heights is discussed. A 3 D-CFD model coupled with FTS chemical kinetics was set up. The computational results are compared with experimental data in terms of the components production rates, etc. The analysis shows that the bed heights, the bed temperature, the superficial gas velocities and particle sizes affect the C_(5+) selectivity and the reaction rates. Product yields are dependent on the operating conditions especially the temperature.

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

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 H2/CO ratio of 1.6. The results indicate that the activity, C4 olefin/（C4 olefin＋C4 paraffin） ratio, and C5 olefin/（C5 olefin＋C5 paraffin） decrease in the order of Fe-Co/SiO2, Fe-Co/AC1, Fe-Co/Al2O3 and Fe- Co/AC2. The activity of Fe-Co/SiO2 reached a maximum. The results of TPR show that the Fe-Co/SiO2 catalyst is to some extent different. XRD patterns show that the Fe-Co/SiO2 catalyst differs significantly from the others; it has two diffraction peaks. The active spinel phase is correlated with the supports.

LDV measurements of particle velocity distribution in an annular stripper

Particle descent velocities in an annular stripper were measured by a laser Doppler velocimetry(LDV)system.In the radial direction,particle descent velocity was relatively constant in the mid-region of the stripper and increased towards the walls on both sides,exhibiting an anti-U-shaped distribution.Particle descent velocity in the radial mid-region increased with the increase of superficial gas velocity,and the maximum in the outer wall region increased significantly with the increase of solid mass flux.Superficial stripping gas velocity had stronger effect on particle velocity distributions near the stripper gas distributor,and such effect weakened with the increase of the distance from the distributor.Local particle velocity and its radial profiles could be adjusted by changing the superficial stripping gas velocity.Empirical formulas were established to describe the relationships between the local particle velocity and cross-sectional averaged velocity based on the effects of operating conditions and measuring positions.The result showed that the predicted data was in good agreement with the experimental value.

Effects of promoters on catalytic performance of Fe-Co/SiO_2 catalyst for Fischer-Tropsch synthesis

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.

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

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 supportedcobalt-based catalysts was investigated. To treat the support with NH4NO3 aqueous solution enlarged the pore of γ-Al2O3, decreased the impurity Na2O content, and weakened the surface acidity of γ-Al2O3. 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/γ-Al2O3 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.

Effects of the ratio of Fe to Co over Fe-Co/SiO_2 bimetallic catalysts on their catalytic performance for Fischer-Tropsch synthesis

The Fe-Co/SiO2 bimetallic catalysts with different ratios of Fe to Co were prepared by aqueous incipient wetness impregnation. The catalysts of 10%Fe：0%Co/SiO2, 10%Fe：6%Co/SiO2, 10%Fe：2%Co/SiO2, 10%Fe：10%Co/SiO2, 6%Fe：10%Co/SiO2, 2%Fe：10%Co/SiO2 and 0%Fe： 10%Co/SiO2 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/SiO2 catalysts. On the other hand, for the catalysts of 10%Fe：6%Co/SiO2, 10%Fe：10%Co/SiO2, 6%Fe：10%Co/SiO2, and 2%Fe：10%Co/SiO2, the total C2-C4 fraction increased （from 10.65% to 26.78%） and C5＋ 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/SiO2 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/SiO2, 6%Fe：10%Co/SiO2, 10%Fe： 10%Co/SiO2, 10%Fe：6%Co/SiO2 catalysts and their crystals were perfect.

Online measurement of solids motion in fluidized bed reactor with different distributor for Fischer–Tropsch synthesis

In this paper, the distributions of particle velocity in a gas–solid fluidized bed with branched pipe distributor or circle distributor were measured by using a laser Doppler velocimetry. Our results show that, within a certain range of superficial gas velocity, when using circle distributor, the particle velocity is large and the distribution of the particle velocity is even more compared with the branched pipe distributor. On the basis of the amplitude of tangential movement statistics, the amplitude of tangential movement statistics(AVATMS) decreases with increasing the axial height under the appropriate superficial gas velocity.

气固流化床中颗粒的夹带和扬析特性

在内径0.5 m、总高6 m的流化床中对玻璃珠和白刚玉颗粒的夹带和扬析现象进行了实验研究,两种颗粒通过筛分配比得到不同粒径分布的实验物料,以0.25~0.76 m/s的速度分批进行流态化试验,考察了表观气速、床层物料粒径分布以及颗粒粒径对颗粒夹带和扬析速率的影响,得到了颗粒的扬析速率常数(K_(i)^(*))。实验结果表明,夹带量和扬析速率常数随着表观气速呈指数增加;扬析速率常数随着颗粒粒径减小先增加,达到一个临界粒径(d_(crit))后,扬析速率常数会随着粒径减小趋于平缓或降低。提出了一组经验关联式,分别用于预测临界粒径两侧颗粒的扬析速率常数,关联式能很好地预测本工作实验条件下的数据,误差在30%以内,并且关联式能够对文献中的实验数据进行较好的预测,可以用于流化床装置的放大。

Numerical simulation of effect of gas distributor on Fischer-Tropsch synthesis in fluidized-bed reactor

Circular and branched pipe distributors were designed for Fischer-Tropsch synthesis in a fluidized-bed reactor. A numerical investigation of the effects of these distributors on product selectivity and production rate was performed. Under the same conditions, the circular distributor gave higher production rates for small diameter particles. For superficial gas velocities ranging from 5 to 15 times the minimum fluidization velocity, the production rates of methane and C5+(the sum of C10H22 and C22H46)were 18%, which was 2% higher than those using the branched pipe distributor, while the C5+ selectivity was 1% lower. For deeper beds, the circular distributor led to higher production rates and the selectivity for C5+ was 5% lower than that using the branched pipe distributor.

Improving in vivo Uranyl Removal Efficacy of a Nano-Metal Organic Framework by Interior Functionalization with 3-Hydroxy-2-pyridinone

The environmental contamination of uranium will occur in scenarios such as nuclear accidents and leakage from nuclear waste storage sites,which eventually leads to the internal uranium exposure of people,causing consequential injuries of renal failure,osteosarcoma,etc.The development of uranyl specific chelating agents that could sequester uranium in vivo is in urgent need and is important for the safe and efficient development of nuclear industry.Metal organic frameworks(MOFs)already serve as efficient uranium depletion materials in solutions of a wide range of pH and ionic strength for nuclear fuel recycling,uranium extraction from seawater,as well as environmental decontamination.Herein,a chromium-based nano-metal organic framework(nano-MOF)functionalized interiorly with 3,2-HOPO ligands,MIL-101-HOPO,is rationally synthesized.In vitro adsorption experiments show that MIL-101-HOPO exhibits high adsorption selectivity and fast adsorption kinetics for uranyl.The results of in vivo uranyl decorporation assays reveal that MIL-101-HOPO with the decoration of HOPO ligands on the interior wall exhibits significantly increased uranyl removal ratio in kidneys comparing to the pristine nMOFs,and is more effective than the clinically used ZnNa_(3)-DTPA.All those results corroborate the interior functionalization of MOFs as an efficient strategy to develop promising uranyl decorporation agents.