Optimization of the calcination process for precipitated iron based Fischer-Tropsch catalyst preparation
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摘要: 通过DOE实验设计对沉淀铁费托合成催化剂焙烧过程进行了优化，并给出了焙烧过程的分子模拟与粒子长大模型。结果表明，随着焙烧温度的升高和焙烧时间的延长，催化剂的孔容减小，堆比及骨架密度增加，耐磨性改善。BET表面与磨耗的变化趋势一致，即比表面积越小磨耗越小；磨耗与密度成线性反比关系，密度越高磨耗越小。通过焙烧工艺的优化，可调变Cu、Si通过O原子与Fe原子的键合作用及催化剂的粒子粒径，得到较高F-T活性且稳定性好的沉淀铁催化剂。在该实验中，优化的焙烧温度为560℃。Abstract: The calcination process of precipitated iron based Fisher-Tropsch synthesis catalysts was optimized by the design of experiment (DOE) tools.And the molecular simulation model and the particle growing model were proposed.The results showed that the catalyst pore volume decreased, the bulk and skeleton density of the catalyst increased, and the attrition resistance of the catalyst improved with the calcination temperature and time increasing.The smaller the BET surface of the catalyst, the smaller the attrition of the catalyst is.The attrition and density of the catalyst have a inverse linear relationship.The bonding strength of Cu, Si with Fe by O atom and the particle size can be adjusted by calcination optimization, thus got high F-T activity and good stability.In our experiments, the optimized calcination temperature is 560℃.
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Key words:
- Fisher-Tropsch synthesis catalyst /
- calcination /
- attrition /
- activity /
- stability
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图 3 DOE 实验样品的XRD谱图
Figure 3 XRD patterns of the samples calcined by DOE experiments
a: 20 ℃/min,600 ℃,6 h； b: 20 ℃/min,600 ℃,2 h； c: 11 ℃/min,500 ℃,4 h； d: 2 ℃/min,400 ℃,6 h； e: 20 ℃/min,400 ℃,2 h
图 4 不同焙烧条件下焙烧样品的H2-TPR谱图
Figure 4 H2-TPR profiles of the catalysts calcined under different conditions
a: 20 ℃/min,600 ℃,6 h； b: 11 ℃/min,500 ℃,4 h； c: 20 ℃/min,400 ℃,2 h
图 5 不同温度下焙烧样品的XRD谱图
Figure 5 XRD patterns of the samples calcined at different temperature
图 6 不同温度焙烧样品的孔径分布
Figure 6 Pore size distribution of the samples calcined at different temperatures
图 7 不同温度焙烧样品的SEM照片
Figure 7 SEM micrograph of the samples calcined at different temperatures
图 8 不同温度焙烧样品的H2-TPR谱图
Figure 8 H2-TPR of the samples calcined at different temperatures
图 9 不同温度焙烧样品的F-T反应活性与稳定性
Figure 9 F-T activity and stability of the samples calcined at different temperatures
图 10 沉淀铁催化剂的焙烧模型示意图
Figure 10 Sintering model of the coprecipitated iron-based F-T catalyst
表 1 DOE实验制备样品的磨耗、密度和BET
Table 1 Attrition,density and BET data of DOE experiments
Sample Pore volume
v/(cm3·g-1)Surface area
A/(m2·g-1)Real density
ρ/(g·cm-3)Attrition /% 2 ℃/min,600 ℃,2 h 0.673 167.04 4.43 4.68 20 ℃/min,600 ℃,6 h 0.664 170.57 4.29 4.47 11 ℃/min,500 ℃,4 h 0.738 216.87 4.13 8.47 2 ℃/min,400 ℃,6 h 0.714 218.51 4.08 7.21 20 ℃/min,400 ℃,2 h 0.701 258.57 3.86 12.2 
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表 2 焙烧温度对催化剂活性与选择性的影响
Table 2 Effects of calcination temperature on iron based FT catalyst activity and selectivity
500 ℃ 560 ℃ 600 ℃ Time on stream t/h 10 50 100 200 10 50 100 200 10 50 100 200 CO conversion x/% 70.0 69.2 62.7 61.5 58.1 60.7 62.4 62.3 57.8 60.7 60.8 61.3 CO2 selectivity s/% 32.2 32.0 31.6 30.9 30.8 30.9 31.6 31.6 30.5 30.9 31.0 30.9 Hydrocarbon selectivity s/% CH4 3.0 3.1 3.3 3.4 2.7 2.7 2.8 2.8 2.5 2.6 2.6 2.5 C2-4 12.0 12.3 13.0 16.4 10.4 10.4 10.9 10.4 9.7 10.0 9.7 9.7 C5+ 85.0 84.6 83.7 80.1 86.9 86.9 86.3 86.8 87.8 87.4 87.7 87.7 reaction conditions: 2.3 MPa,235 ℃,H2/CO(volume ratio)=1.5,GHSV=3 000 h-1
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