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標題: | 鉬基中孔觸媒於合成氣催化產製碳氫化合物之研究 Reforming of Syngas to Hydrocarbon Compounds via Catalytic Reaction with Modified Mo-based Mesoporous Catalysts |
作者: | Chih-Han Hsu 徐芷涵 |
指導教授: | 張慶源 |
關鍵字: | 合成氣,一氧化碳氫化,醇類及烷類合成,二氧化鉬,鉀觸媒表面改質, syngas,CO hydrogenation,synthesis of alcohols and alkanes,molybdenum dioxide,surface modification of potassium, |
出版年 : | 2014 |
學位: | 碩士 |
摘要: | 本研究利用鉬基(Mo-based)觸媒於高壓催化反應(high pressure catalytic packed bed system, HPCPB system),將合成氣(CO及H2)進行重組反應以產製液態燃料。研究中以中孔洞分子篩SBA-15作為觸媒之載體(SBA-15P),並製備成4 mm (D) × 4 mm (H)之圓柱狀顆粒載體SBA-15G,以降低高壓反應系統中之壓損及減少阻塞。SBA-15披覆MoO2成為鉬基(Mo-based)觸媒MoO2/SBA-15,並再以鹼金族-鉀(potassium, K)作為改質劑,將MoO2/SBA-15(P, G)觸媒表面改質,以 20 wt. % Mo及5 或 10 wt.% K為製備觸媒所用溶液之濃度,分別以觸媒20MoO2/SBA-15 (20 wt. % Mo)及5,10K-20MoO2/SBA-15 (5 或 10 wt. % K, 20 wt. % Mo)表示。研究中並進行BET比表面積、BJH孔洞分布、XRD、SEM/EDS及ICP/MS等物理特性分析。
研究探討HPCPB系統於壓力(P) = 400 psi、H2/CO = 2條件下,不同溫度(T =200、250及300oC)、氣體空間流速(gas hourly space velocity, GHSV= 1,684、2,526、3,368及5,052 h-1)及觸媒種類對合成氣轉化效能之影響,評估之參數包含一氧化碳轉化率(XCO)、烷類與醇類之比生產速率(specific production rates, SPRAlk及SPRAOH)、產率(yield, YAlk及YAOH)及選擇性(selectivity, SAlk及SAOH)。 結果顯示T = 300 oC為20MoO2/SBA-15G之最適反應溫度,其液體產物之產率(GHSV = 1,684 h-1時,YC5+Alk = 6.65 C%及YAOH = 0.03 C%)最佳。5K-20MoO2/SBA-15P之反應最適溫度則為250 oC,此溫度下之醇類的選擇性(SAOH = 2.35 C%優於20MoO2/SBA-15G之0.14 C%,ΔSAOH = 2.21 C%)及產率(YAOH = 0.36 C% 優於20MoO2/SBA-15G之0.02 C%,ΔYAOH = 0.34 C%)皆會增加。20MoO2/SBA-15G的最適醇類轉製反應之GHSV為3,368 h-1(YAOH+YC5+Alk = 6.68 C%),而對總液體產物(AOH與C5+Alk)而言,最適GHSV為1,684 h-1,不同GHSV下所轉製之目標產物亦不同,低GHSV下以高碳數烷類(C5+Alk)為主,醇類則於最適GHSV可有最佳產率。 對於粉末觸媒而言,添加K金屬進行20MoO2/SBA-15P表面改質並無增加反應中觸媒對醇類的選擇性(T = 300 oC及GHSV = 1,684 h-1時,SAOH僅由1.08 C% 增至 0.00 C%),而是以產製C5+Alk為主(SC5+Alk由3.54 C% 增至11.15 C%)。對於顆粒觸媒,5K-20MoO2/SBA-15G 觸媒確實有效提升合成氣催化反應中觸媒對醇類之產率(YAOH = 0.35 C% 優於20MoO2/SBA-15G 之0.03 C%,ΔYAOH = 0.32 C%)及選擇性(SAOH = 3.81 C% 優於20MoO2/SBA-15G之0.11 C%,ΔSAOH = 3.70 C%)。 This study using Mo-based catalyst in high pressure catalytic packed bed system (HPCPB system) to produce liquid fuel by syngas (CO and H2) reforming reaction. A mesoporous material SBA-15 was used as support (SBA-15P) and shaped into 4 mm diameter by 4mm length cylindrical pellet (SBA-15G) for reducing the pressure drop and avoiding pluging in packed bed. Molybdenum dioxide (MoO2) was taken as the catalyst of SBA-15 and potassium (K) was used as the promoter linked on the surface of MoO2/SBA-15. The 20MoO2/SBA-15 and 5,10K-20MoO2/SBA-15 were prepared employed solutions with 20 wt. % Mo and 5 or 10 wt. % K and 20 wt. % Mo, respectively. The physical characteristics of catalyst examined include BET surface area, BJH pore size distribution, XRD, SEM/EDS and ICP-MS. The effects of temperature (T =200, 250 and 300oC), gas hourly space velocity (GHSV= 1,684, 2,526, 3,368 and 5,052 h-1) and catalyst on the syngas transformation HPCPB system were investigated with pressure P = 400 psi and H2/CO molar ratio = 2. The conversion of CO (XCO), specific production rates of alcohol (SPRAOH) and alkane (SPRAlk), yield (YAlk and YAOH) and selectivity (SAlk and SAOH) were computed and used to access the appropriation of operation conditions. The result shows that T = 300 oC is the most proper temperature for 20MoO2/SBA-15G which has maximum yield of liquid product (at GHSV = 1,684 h-1, YC5+Alk = 6.65 C%, YAOH = 0.03 C%). For 5K-20MoO2/SBA-15P, T = 250oC is the most decent reaction temperatures which can increase the selectivity and yield of alcohols (SAOH =2.35 C% between than 0.14 C% of 20MoO2/SBA-15G, ΔSAOH = 2.21 C%; YAOH = 0.36 C% greater than 0.02 C% of 20MoO2/SBA-15G, ΔYAOH = 0.34 C%). Moreover, for 20MoO2/SBA-15G, the most appropriate GHSV for alcohol and total liquid product are 3,368 h-1 (at T = 300 oC, YAOH = 0.94C%) and 1,684 h-1 (YAOH+YC5+Alk = 6.68 C%), respectively. As for various GHSV, the main products are C5+Alk at lower GHSV. Effects of modification of MoO2/SBA-15 using K on AOHs and Alks from hydrogenation of CO were studied. For powder catalyst, the effectiveness of K modification of 20MoO2/SBA-15P was producing mainly C5+Alk (with slight increase of SAOH from 1.08 C% to 0.00 C%) (at T = 300 oC and GHSV = 1,684 h-1, SC5+Alk increasing from 3.54 C% to 11.15 C%) while minorly the alcohols. As for pellet catalyst, the yield and selectivity of alcohols during syngas catalytic reaction are greatly enhanced by using 5K-20MoO2/SBA-15G (YAOH = 0.35 C% higher than 0.03 C% of 20MoO2/SBA-15G, ΔYAOH = 0.32 C%; SAOH = 3.81 C% between than 0.11 C% of 20MoO2/SBA-15G, ΔSAOH = 3.70 C%). |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/4990 |
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