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摘要: 采用分步沉淀法制备出一系列不同铝含量的催化剂样品，通过X射线衍射（XRD）、热重-质谱（TG-MS）、荧光光谱仪（XRF）、N2物理吸附、氢气程序升温还原（H2-TPR）对样品进行表征，考察了不同铝添加量对铜基甲醇催化剂性能的影响。结果表明，铝元素的添加对前驱物中碱式碳酸盐组分产生作用，促进了焙烧后样品中高温碳酸盐的形成，进而影响到催化剂的性能。随着铝元素的添加，焙烧后催化剂的比表面积、催化剂活性和热稳定性均有增加。当Al3+/（Cu2++Zn2++Al3+）物质的量比增加至30%时，催化剂在230 ℃、4 MPa和合成气（13% CO、1.2% CO2、80% H2、5.8% Ar）的评价条件下，热处理前后的CO转化率分别为76%和67%，仍保持着较高的活性和热稳定性。Abstract: The objective of this work is to investigate the effect of Al contents on the performance of methanol-synthesis catalysts. A series of catalyst samples with various Al contents were prepared with fractional precipitation method, and characterized with methods including XRD, TG-MS, XRF, N2 physisorption and H2-TPR. Results show that Al addition affected the subcarbonate structure in precursors, which promoted the formation of high temperature carbonates, and thus has an effect on the catalyst performance. With Al addition, the BET surface area of the calcined catalysts, catalyst activity and thermostability increased to different degrees. When the molar ratio of Al3+ in catalyst increased to 30%, the CO conversions before and after heat treatment were 76% and 67%, respectively, at the conditions of 230 ℃, 4 MPa and syngas composition of 13%CO, 1.2%CO2, 80%H2 and 5.8%Ar. The catalyst sample with 0.3 of Al3+/(Cu2++Zn2++Al3+) molar ratio remains good catalyst performance.
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Key words:
- Al contents /
- high temperature carbonates /
- thermostability /
- malachite decomposition
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图 1 甲醇合成催化剂高通量评价装置示意图
Figure 1 Diagram of high throughput evaluation apparatus for methanol-synthesis catalysts
图 2 甲醇合成催化剂前驱物样品的XRD谱图
(■: hydrotalcte compounds；●: zinc malachite；▲ : aurichalcite)
Figure 2 XRD patterns of the precursor samples of methanol-synthesis catalysts
图 3 催化剂前驱物的热重质谱联用分析(10 ℃/min, 空气气氛)
Figure 3 DTG-MS results of the precursor samples (10 ℃/min, in air)
图 5 焙烧后不同铝含量催化剂样品的H2-TPR谱图(2 ℃/min，氢气气氛)
Figure 5 H2-TPR profiles of calcined catalyst samples with different Al contents (2 ℃/min, in H2 atmosphere)
图 6 甲醇合成催化剂样品的活性和热稳定性
Figure 6 Evaluation results for activity and thermostability of the methanol-synthesis catalyst samples
reaction conditions: 4 MPa, GHSV=8000 h-1,
reacting at 230 ℃ and heat treating at 320 ℃,
13%CO, 1.2%CO2, 80%H2, 5.8%Ar表 1 甲醇合成催化剂样品的设计元素组成
Table 1 Designed atomic ratio of the methanol synthesis catalyst samples
Catalyst ID Cu2+:Zn2+:Al3+ (molar ratio) 0Al 66.7:33.3:0 4Al 64.0:32.0:4.0 8Al 61.3:30.6:8.0 16Al 56.0:28.0:16.0 30Al 47.6:23.3:30.0 
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表 2 XRD分析矿物的特征衍射峰和PDF编号
Table 2 Primary peaks and PDF numbers of the species identified in the XRD spectra
Compound Characteristic peaks 2θ/(°) PDF number Copper oxide 32.496, 35.495, 38.730, 48.725 45-0937 Zinc malachite 14.637, 17.467, 24.075, 29.591 35-0502 Aurichalcite 13.028, 24.032, 27.857, 32.655 38-0152 Hydrotalcite-like compounds 11.750, 23.579, 34.617, 39.258 38-0487
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表 3 焙烧后样品的元素组成分析和比表面积
Table 3 Composition and BET results of the calcined samples
Catalyst ID Cu2+:Zn2+:Al3+ (molar ratio)a Ab/(m2·g-1) vc/(cm3·g-1) Dd/nm 0Al 70.48:29.49:0.02 53.0 0.2114 15.95 4Al 67.58:28.65:3.77 76.8 0.4113 21.42 8Al 63.27:28.71:8.02 89.6 0.4374 19.54 16Al 58.66:26.30:15.04 105.5 0.4702 17.83 30Al 47.57:22.36:30.08 187.9 0.5968 9.73 a: normalized results determined by XRF; b: specific surface area determined by N2 physisorption;
c: pore volume determined by N2 physisorption; d: pore diameter determined by N2 physisorption
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