Catalytic performance of methanol decomposition on Cu/SiO2 catalyst with different silica sources prepared with ammonia evaporation method
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摘要: 采用蒸氨法制备Cu/SiO2催化剂，分别考察气相二氧化硅（SiO2-aer）、硅胶（SiO2-gel）和碱性硅溶胶（SiO2-sol）对Cu/SiO2催化剂催化甲醇裂解制氢性能的影响，并采用N2吸附-脱附、N2O化学吸附、电感耦合等离子体原子发射光谱法（ICP-AES）、X射线衍射（XRD）、H2程序升温还原（H2-TPR）、透射电子显微镜（TEM）和X射线光电子能谱（XPS）等方法对催化剂进行表征。结果表明，硅源对Cu/SiO2催化剂的活性具有较大影响。以碱性硅溶胶作为硅源制得的Cu/SiO2-sol催化剂比表面积较大，活性中心粒径较小且分散均匀，这些使得其制氢性能优于其他两种硅源为载体所制备的催化剂。在反应温度280 ℃，反应压力1 MPa，甲醇质量空速0.6 h-1的条件下，相较于Cu/SiO2-aer和Cu/SiO2-gel催化剂，Cu/SiO2-sol催化剂的甲醇转化率分别提高10%和7%，气相副产物CH4和CO2浓度也有所降低，该催化剂上的甲醇转化率和气体收率分别达到98.4%和96.7%。
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关键词:
- 甲醇裂解 /
- 蒸氨法 /
- Cu/SiO2催化剂
Abstract: Cu/SiO2 catalysts were prepared via ammonia evaporation method, using fumed silica (SiO2-aer), silica gel (SiO2-gel) and alkaline silica sol (SiO2-sol) as the silica sources and their catalytic performance in methanol decomposition were investigated. The catalysts were characterized by N2 adsorption-desorption, N2O chemisorption, inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy(XPS). The results indicate that silica source can affect the decomposition activity of Cu/SiO2 catalysts. The Cu/SiO2-sol catalyst prepared with alkaline silica sol exhibits larger surface area, smaller active site size and more uniform dispersion of Cu. Therefore, it gives Cu/SiO2-sol a better decomposition performance than other catalysts. Methanol conversion on Cu/SiO2-sol is 10% higher than that on Cu/SiO2-aer, and 7% higher than that on Cu/SiO2-gel. Additionally, byproducts concentration on Cu/SiO2-sol is considerably lower than other catalysts. Under the reaction conditions of 280 ℃, 1 MPa and 0.6 h-1 of WHSV, methanol conversion of 98.4% and gas yield of 96.7% can be achieved.-
Key words:
- methanol decomposition /
- ammonia evaporation method /
- Cu/SiO2 catalyst
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图 1 不同硅源制备Cu/SiO2催化剂的XRD谱图
Figure 1 XRD patterns of the Cu/SiO2 catalysts prepared with different silica sources
a: Cu/SiO2-aer; b: Cu/SiO2-gel; c: Cu/SiO2-sol
图 2 还原态Cu/SiO2催化剂的XRD谱图
Figure 2 XRD patterns of the reduced Cu/SiO2 catalysts prepared with different silica sources
a: Cu/SiO2-aer; b: Cu/SiO2-gel; c: Cu/SiO2-sol
图 3 Cu/SiO2催化剂的H2-TPR谱图
Figure 3 H2-TPR profiles of the Cu/SiO2 catalysts prepared with different silica sources
a: Cu/SiO2-aer; b: Cu/SiO2-gel; c: Cu/SiO2-sol
图 4 Cu/SiO2催化剂的透射电镜照片
Figure 4 EM images of the Cu/SiO2 catalysts prepared with different silica sources
(a): Cu/SiO2-aer; (b): Cu/SiO2-gel; (c): Cu/SiO2-sol
图 5 还原态Cu/SiO2催化剂的透射电镜照片
Figure 5 TEM images of the reduced Cu/SiO2 catalysts prepared with different silica sources
(a): Cu/SiO2-aer; (b): Cu/SiO2-gel; (c): Cu/SiO2-sol
图 6 Cu/SiO2催化剂的XPS谱图
Figure 6 XPS spectra of the Cu/SiO2 catalysts after calcinations
a: Cu/SiO2-aer; b: Cu/SiO2-gel; c: Cu/SiO2-sol
图 7 反应温度对催化性能的影响
Figure 7 Effect of reaction temperature on methanol decomposition over Cu/SiO2-sol catalyst
图 8 反应温度对气相副产物浓度的影响
Figure 8 Effect of reaction temperature on the byproducts concentration of methanol decomposition over Cu/SiO2-sol catalyst
图 9 质量空速对催化性能的影响
Figure 9 Effect of methanol weight hourly space velocity on methanol decomposition over Cu/SiO2-sol catalyst
图 10 质量空速对气相副产物浓度的影响
Figure 10 Effect of methanol weight hourly space velocity on the byproducts concentration of methanol decomposition over Cu/SiO2-sol catalyst
图 11 Cu/SiO2-sol上甲醇裂解制氢的稳定性
Figure 11 Stability test of methanol decomposition over Cu/SiO2-sol catalysts
图 12 Cu/SiO2-sol催化剂反应前后的透射电镜照片
Figure 12 TEM images of the reduced and used Cu/SiO2-sol catalyst
(a): Cu/SiO2-sol catalyst after reduction; (b): Cu/SiO2-sol catalyst after reaction 100h
表 1 不同硅源制备的Cu/SiO2催化剂的比表面积和孔结构性质
Table 1 Textural properties of the Cu/SiO2 catalysts prepared with different silica sources
Catalyst BET a
A/(m2·g-1)Pore volumea
v /(cm3·g-1)Average porea
diameter d /nmCu dispersionb
/%Content w/%c Cu Na SiO2-aer 359.2 0.83 11.11 - - - SiO2-gel 324.9 0.96 10.27 - - - SiO2-sol 192.8 0.2 4.12 - - - Cu/SiO2-aer 512.8 0.47 3.35 20.1 33.2 B.D. Cu/SiO2-gel 555.3 0.42 2.71 22.3 33.7 B.D. Cu/SiO2-sol 580.6 0.69 4.09 24.8 34.5 B.D. a：determined by N2 adsorption-desorption；b：detected by N2O chemisorption；c：determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES)，B.D.=below detection 
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表 2 不同硅源对Cu/SiO2催化剂催化甲醇裂解制氢的影响
Table 2 Catalytic performance of the Cu/SiO2 catalysts with different silica sources in methanol decomposition
Catalyst Methanol conversion x/% Gas yield w/% Concentration φ/% CH4 CO2 Cu/SiO2-aer 88.7 86.1 1.04 2.12 Cu/SiO2-gel 91.7 89.5 0.8 1.93 Cu/SiO2-sol 98.4 96.7 0.71 1.75
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