CH3OH Reforming for Hydrogen over CuO/ZnO/Al2O3 Modified Catalyst
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摘要: 采用Langmuir-Hinshelwood型双速率动力学模型方程对CH3OH水蒸气重整制氢反应本征动力学实验数据进行拟合,同时探讨了反应条件对CH3OH水蒸气重整制氢反应的影响。结果表明:反应器出口气体中CO和CO2摩尔流率的计算值与实验值较吻合,说明所采用的双速率动力学模型适用。考察CuO/ZnO/Al2O3改性催化剂在200 ℃和300 ℃下的失活现象,表征结果表明,催化剂失活的主要原因有热烧结、催化剂比表面积减小、介孔比例减少、活性组分CuO流失、CuO晶粒变大等,但高温反应产生的高含量CO对催化剂失活没有产生明显影响。
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关键词:
- 甲醇水蒸气重整 /
- 制氢 /
- CuO-ZnO-Al2O3催化剂 /
- 反应动力学 /
- 催化剂失活
Abstract: The effects of reaction conditions on hydrogen production from methanol steam reforming were discussed. The experimental results showed that the optimal temperature of the reaction was about 240 ℃. High temperature increased the selectivity of CO, and low temperature decreased the conversion rate of CH3OH. When the molar ratio of H2O to CH3OH increased, the conversion rate of CH3OH increased and the selectivity of CO decreased. If the molar ratio of H2O to CH3OH was too high, more energy would be consumed. To ensure the conversion rate of CH3OH, the liquid hourly space velocity of feed liquid was appropriately increased. The Langmuir-Hinshelwood two-rate dynamics model equation was used to fit the experimental data of intrinsic dynamics. The calculated values of molar flow rates of CO and CO2 in the gas products at the reactor outlet were in good agreement with the experimental values, and the two-rate model was applicable. The deactivation of CuO/ZnO/Al2O3 modified catalysts at 200 ℃ and 300 ℃ was also investigated. Using BET, XRF, XRD and CO-TPD, it was found that the main reasons for the deactivation of the catalysts were, in addition to hot sintering, the reduction of specific surface area and mesoporous ratio, the CuO loss, and the increase of CuO grain size. The high content of CO produced in the high temperature had no obvious effect on catalyst deactivation. -
表 1 甲醇水蒸气重整制氢的本征动力学实验数据
Table 1. Experimental data of the intrinsic kinetics of hydrogen production via methanol steam reforming
No. n(H2O)∶n(CH3OH) T/K LHSV/h−1 $F_{ {{\rm{CH}}_3}{\rm{OH}}}$/(mol·h−1) $F_{ {{\rm{CO}}_2} }$/(mol·h−1) FCO/(mol·h−1) 1 1.0 473.85 0.6 0.0205 0.0154 9.8448×10−5 2 1.0 494.25 3.0 0.1015 0.0671 4.9177×10−4 3 1.0 513.65 5.4 0.1696 0.1344 2.2848×10−3 4 1.0 534.25 7.8 0.2659 0.2527 1.3254×10−2 5 1.0 552.75 10.2 0.3780 0.3381 3.9876×10−2 6 1.2 473.75 3.0 0.0957 0.0362 9.6495×10−5 7 1.2 492.15 5.4 0.1723 0.1025 4.5281×10−4 8 1.2 512.25 7.8 0.2539 0.2052 1.8352×10−3 9 1.2 532.15 10.2 0.3296 0.3185 6.4057×10−3 10 1.2 552.25 0.6 0.0215 0.0180 3.5035×10−3 11 1.4 473.45 5.4 0.1623 0.0409 1.1377×10−4 12 1.4 493.85 7.8 0.2399 0.1033 4.2425×10−4 13 1.4 513.45 10.2 0.3129 0.2290 1.6716×10−3 14 1.4 532.35 0.6 0.0215 0.0191 2.4027×10−3 15 1.4 553.15 3.0 0.0957 0.0864 9.2942×10−3 16 1.6 473.65 7.8 0.2200 0.0515 1.2969×10−4 17 1.6 492.85 10.2 0.2881 0.1463 5.4197×10−4 18 1.6 513.45 0.6 0.0161 0.0154 7.1376×10−4 19 1.6 533.25 3.0 0.0836 0.0756 3.1437×10−3 20 1.6 552.75 5.4 0.1659 0.1546 1.1266×10−2 21 1.8 474.25 10.2 0.2760 0.0567 1.1231×10−4 22 1.8 494.15 0.6 0.0184 0.0181 3.3210×10−4 23 1.8 513.45 3.0 0.1025 0.1008 1.6955×10−3 24 1.8 532.75 5.4 0.1471 0.1436 3.4834×10−3 25 1.8 552.65 7.8 0.1883 0.1765 7.0671×10−3 表 2 运用ISTOpt软件得到的动力学模型参数
Table 2. Estimated parameters for the kinetic model by ISTOpt software
Parameter ${k}_{\rm SR}^{0}$ ${k}_{\rm RWGS}^{0}$ ${E}_{\rm SR}$/(kJ·mol−1) ${E}_{\rm RWGS}$/(kJ·mol−1) ${K}_{ {\rm CH}_{3}{\rm O}^{\left(1\right)} }^{0}$ ${K}_{ {\rm HCOO}^{\left(1\right)} }^{0}$ ${K}_{ {\rm OH}^{\left(1\right)} }^{0}$ ${K}_{ {\rm H}^{\left(1{\rm{a}}\right)} }^{0}$ Estimated value 8.7×109 3.2×108 100.3 79.5 −32.1 231.9 −54.6 −127.2 LL1) 6.8×109 2.5×108 80.7 67.6 −37.3 204.1 −61.8 −145.3 UL2) 10.6×109 3.9×108 119.9 91.4 −26.9 259.7 −47.4 −109.1 1)Lower limit of the 95% confidence interval; 2)Upper limit of the 95% confidence interval 表 3 催化剂的结构参数
Table 3. Structure parameters of catalysts
Catalyst SBET/(m2·g−1) Pore volume/(cm3·g−1) Pore size/nm Crystallite size/nm CuO Cu Sample 1# 101.08 0.19 7.17 5.8 – Sample 2# 57.38 0.23 10.89 8.5 16.3 Sample 3# 84.69 0.20 13.74 7.9 11.0 表 4 催化剂中主要元素质量分数
Table 4. Mass fraction of main elements in catalysts
Elements w/% Sample 1# Sample 2# Sample 3# Cu 42.32 41.15 40.23 O 28.91 20.71 21.44 Zn 14.44 13.62 13.85 C 9.07 7.57 8.09 Al 5.07 3.69 4.04 -
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