氧化釔溶膠洗漬操作對銅鋅觸媒催化甲醇蒸汽重組反應活性的影響

Effect of washcoating condition on the methanol steam reforming reaction over Cu-Zn-Al catalyst

楊鎮豪(Chen-Hao Yang)

指導教授 ： 葉君棣

共同指導教授 ： 林昇佃(Shawn D. Lin)

元智大學/工程學院/化學工程與材料科學學系/碩士(2009年)

摘要

本研究以連續沉澱法製作CuZnAl觸媒，用於固定床反應器中催化甲醇蒸汽重組(steam reforming of methanol, SRM)反應，並利用中性Y2O3 sol為黏著劑，將製出的觸媒做成漿料(slurry)，洗漬(washcoating)於不銹鋼板的微流道中，製作微反應器，探討固定床反應器與微反應器的差異。
觸媒的煅燒前處理時的升溫速率會影響CuO與ZnO顆粒大小及銅分散度(DCu)，煅燒升溫速率緩慢的觸媒可以得到較小的顆粒與高的銅分散度；在活性測試中，甲醇轉化率會隨著銅分散度而有較好的催化活性。以觸媒漿料粉體進行XRD、TPR分析，顯示銅分散度會隨著Y2O3 sol添加量的增加而提升，以及CuO與ZnO顆粒會隨著Y2O3 sol添加量增加而有變小的趨勢。以固定床反應器進行SRM反應測試，CuO與ZnO顆粒變小的程度越大，甲醇轉化率提升的趨勢越明顯。
不同Y2O3 sol含量的觸媒漿料洗漬於微流道反應器後，進行SRM反應測試，結果顯示固定床反應器的催化活性優於微反應器，並且甲醇轉化率會隨Y2O3 sol的增加而活性變差。SEM圖譜顯示，Y2O3 sol添加過多時，微流道中的觸媒漿料會聚集成塊狀，可能使反應氣體不容易進入觸媒床內部參與反應；並計算不同Y2O3添加量觸媒漿料的氣體分子擴散質傳係數，可見反應氣體的質傳係數會隨著Y2O3 sol的增加而下降，顯示在微反應器Y2O3 sol的添加可能造成較大的質傳阻抗。

關鍵字

甲醇蒸汽重組,洗漬,觸媒

並列摘要

In the study, CuZnAl catalysts were synthesized by sequential precipitation for the steam reforming of methanol (SRM) reaction in fixed bed reactor. The neutral Y2O3 sol is used as binder to prepare catalyst slurry for washcoating onto steel micro channel to assemble the micro reformer. Comparing the catalytic performance of fixed bed reactor with micro reformer is investigated in this thesis.
The particle size and copper dispersion (DCu) of CuZnAl catalysts were significantly affected by heating rate of calcination. The slower calcine rate was resulted in small particle size and high Cu dispersion. The activity measurements in fixed bed reactor, the methanol conversion in SRM reaction raises with Cu dispersion increasing. Besides, the amount of Y2O3 sol added in the slurry also influences the activity. By using XRD and TPR analysis, the spectra indicate the CuZnAl catalyst slurry with high Y2O3 sol input exhibits small particle size and high copper dispersion (DCu) that due to good catalytic activity.
Adjusting various Y2O3 sol ratios in slurry to washcoat onto micro channel reactor, the catalytic activities were tested by SRM reaction. The results show that catalytic activity is better in fixed bed reactor than micro-channel reactor. Otherwise, in micro-channel reactor, the methanol conversion decreased with Y2O3 sol addition. The SEM images show the aggregate of catalysts slurry in micro channel with excess of Y2O3 sol forms a chunk catalyst layer. It’s difficult for reactant gases to diffuse into the catalyst layer and active reaction. Calculating the diffusion coefficient of methanol gas in different catalyst slurries, the results display an inverse tendency of diffusion coefficient and an obverse tendency of mass resistance with increase of Y2O3 sol in micro channel reactor.

並列關鍵字

steam reforming of methanol,washcoating,catalyst

參考文獻

[7] Y. M. Lin, M. H. Rei, Int. J. Hydrogen Energy 25 (2000) 211

[8] S. Patel, K.K. Pant, J. Porous Mater 13 (2006) 373

[11] V. Agarwal, S. Patel, K. K. Pant, Appl. Catal. A, 279 (2005) 155

[14] R. O. Idem, N. N. Bakhshi, Chem. Eng. Sci. 51 (1996) 3697

[16] C. Agrafiotis, A. Tsetsekou, I. Leon, J. Am. Ceram. Soc. 83 (2000) 1033