以金觸媒催化甲醇重組反應製造氫氣

Reforming of Methanol for Hydrogen Production over Gold Catalysts

陳永杰(Yeong-Jey Chen)

指導教授 ： 葉君棣

國立清華大學/理學院/化學系/博士(2006年)

https://doi.org/10.6843/NTHU.2006.00447

摘要

本研究以沉澱沉積法將金顆粒分散在氧化鋅、氧化鋯、氧化鋁等支撐物上，製備出高分散度的金觸媒(dAu < 5 nm)，在固定床反應器中測試金觸媒對甲醇重組製氫反應的活性與選擇性，並比較金觸媒對四組不同重組程序：甲醇分解(MD)、甲醇蒸汽重組(SRM)、甲醇部分氧化(POM)與甲醇氧化性蒸汽重組(OSRM)反應的催化特性。
在POM反應中，自製的金觸媒在較低的溫度下(TR)比商業用銅觸媒(20 wt% Cu/ZnO-Al2O3)有更高的甲醇轉化活性(CMeOH)與很低的CO選擇性(SCO)。支撐物的種類對氫氣的選擇性有很大的影響，Au/ZnO在測試的金觸媒中，具有最高的甲醇轉化率、最高的氫氣選擇性和最少的CO含量。
在不同重組程序的測試中，相較於MD與SRM的高反應溫度需求(TR > 550 K)，POM與OSRM由於氧氣的加入，奈米金顆粒可以在低溫下(TR < 450 K)分解甲醇成為低CO含量的富氫氣體。
在OSRM反應測試中，O2與H2O氧化劑的加入量增加，都有助於提升反應活性，並減少CO的含量，在450 K、氧醇比0.25、水醇比1.5條件下，可以得到氫氣含量超過50 %、甲醇殘量小於1 %、CO含量小於0.2 %的乾燥富氫氣體，經過簡單的CO優先氧化處理，便可以提供作為質子交換膜燃料電池的氫氣來源。

關鍵字

金觸媒 ； 甲醇重組 ； 氫氣

並列摘要

Highly dispersed gold particles (dAu < 5 nm) were deposited on ZnO, ZrO2, and Al2O3 supports by deposition precipitation method. Catalytic activity of gold catalysts toward methanol reforming reactions was tested in the fix bed reactor. The catalytic activity and selectivity of four different methanol reforming processes: methanol decomposition (MD), steam reforming of methanol (SRM), partial oxidation of methanol (POM), and oxidative steam reforming of methanol (OSRM), over gold catalysts were discussed in this study.
In comparison with commercial copper catalysts (20 wt% Cu/ZnO-Al2O3), prepared gold catalysts can catalyze the POM reaction at lower temperature (TR) with higher methanol conversion (CMeOH) and lower CO selectivity (SCO). Support of gold catalysts significantly affected the selectivity to hydrogen. Among the tested catalysts, Au/ZnO exhibited the highest methanol conversion, the highest selectivity to hydrogen, and the least contamination of CO.
The Au/ZnO was not active to DM and SRM at TR < 623 K but exhibited good activity for POM and OSRM at TR < 423 K. Oxygen in the feed of POM and OSRM definitely promoted the methanol decomposition over Au crystallites at low temperatures.
Au/ZnO is an excellent catalyst for reforming methanol to hydrogen rich gas (HRG) through OSRM reaction. At stoichiometries of w (nH2O/nMeOH) = 1.5 and x (nO2/nMeOH) = 0.25 at TR ~ 450 K, a dried HRG product composed with high hydrogen ( > 50 %), low methanol (~ 1 %) and CO (~ 0.2 %) contamination. The composition of HRG is suitable to feed hydrogen fuel cell after a single stage CO removal by preferential oxidation.

並列關鍵字

gold catalyst ； methanol reforming ； hydrogen

參考文獻

3. Watkins, D. S., Fuel Cell System, Plenum Press, New York, p. 493 (1993).

4. Cheng, W. H., Acc. Chem. Res. 32, 685. (1999).

6. Takezawa, N., and Iwasa, N., Catal. Today 36, 45 (1997).

10. Lin, Y. M., and Rei, M. H., Int. J. Hydrogen Energy 25, 211 (2000).

19. Chang, F-W., Yu, H-Y., Roselin L. S., Yang, H-C., Appl. Catal. A 290, 138–147 (2005).