利用HZSM-5沸石轉換含水乙醇製成汽油

Abstract

本研究利用觸媒HZSM-5（Si/Al = 45）將含水乙醇轉換成以液態產物為主之碳氫化合物。首先，探討進料含水率、重量時空速度（WHSV）、溫度與壓力對產物選擇性之影響，找出最適液態產物之反應條件，再於該條件下，進行不同方式之長時間反應－再生－反應試驗，探討觸媒之活性與使用效率。結果顯示：液態產物之選擇性隨含水率之增加而下降，含水率高於60%（w/w）則更顯著，即過高之含水率除不利於脫水反應外，亦不利於液態產物，故以28%（w/w）之含水率作為選擇最適反應條件之料源。WHSV越高，進料在反應器內駐留時間越短，低分子量之中間產物沒能來得及完成聚合反應，導致液態產物選擇性降低。提高壓力可增加反應速度，亦可提高產率，即提高反應壓力，有助於聚合反應之催化活性。提高壓力雖有助於液態產物，然在過高壓力下，高碳數產物縮合而成之高黏性結焦，一經吸附在觸媒表面即不易揮發移除，或於移除過程連帶破壞觸媒之活性部位，導致觸媒活性降低，甚至壽命終止。綜合來看，最適液態產物之反應條件為重量時空速度 = 4.30 h-1、溫度350˚C、壓力60 kg/cm2。在最適條件下，液態產物產率可達30.7%，為碳氫化合物理論產率之70%。 長時間反應－再生－反應試驗顯示，觸媒之活性雖可經再生程序予以回復，卻無法完全回復。於反應期間採定時及以液態產物選擇性低於10%作為啟動觸媒再生程序之指標者，相較於僅以液態產物選擇性低於10%作為指標者，雖無法改善觸媒之使用壽命，卻可提高觸媒之使用效率10%以上。 產物之品質，經由與中油公司市售之九五無鉛汽油比較，本研究所得之液態產物與市售九五無鉛汽油成份相近。

The purpose of this study is using catalyst HZSM-5 (Si/Al=45) to convert aqueous ethanol to liquid type hydrocarbon. Four parameters including moisture content, weight hourly space velocity (WHSV), temperature and pressure were studied for the selectivity of products. Then the optimal ones were applied in the operating of long term reaction-regeneration experiments to examine the activity and efficiency of catalyst. The results showed that, the selectivity of liquid products was affected by moisture content especially when the moisture content was over 60% (w/w). That is, in excess moisture content, it was not suitable for the dehydration of ethanol. Therefore, 72% (w/w) ethanol was selected for the optimal feeding in the study. Furthermore, the more the WHSV, the shorter the contacting time in the reactor and in the meantime the incomplete polymerization made the selectivity of liquid products decreased. The yield of liquid products increased with the rising pressure. The catalyst deactivated and damaged due to the coke with high carbon on the surface. In summary, the oil quality synthesized in this test was familiar with the commercial 95 unleaded gasoline from CPC. The optimal parameters were WHSV=4.30 h-1, 350˚C and 60 kg/cm2. The yield of liquid products and theoretical yield of hydrocarbon could be achieved 30.7% and 70% respectively. The long term reaction-regeneration experiments showed the catalyst activity could not be completely regenerated. It could provide over 10% the selectivity of liquid products by using both constant time and limited selectivity of liquid products as the indicators in comparing with that just using limited selectivity of liquid product as the indicator.