連續式觸媒催化合成產製燃料及化學品之研究

本研究以連續製程進行合成氣轉化產製燃料及化學品，並探討操作參數對CO之轉化率及產物之產率和選擇率之影響。此技術之開發可以協助解決國內有機或生質廢棄物所造成之環境問題，先將其氣化為合成氣再將合成氣轉化為能源物質，期能提供一部分國內分散式能源/電力供應的能源物質需求量。本研究之實驗使用連續式高壓觸媒填充床(high pressure catalytic packed bed, HPCPB)將合成氣(CO及H2)轉化成燃料及化學品。所探討之因子包括：溫度、H2/CO比例、水氣添加及觸媒種類。本實驗之一般條件為：(1) 進氣總壓力PST = 3.10 MPa（298 K之讀值），(2) 反應溫度T = 523 K，(3) 氣體流量QG = 300 mL min-1，(4) H2/CO = 2 (vol./vol.)，(5) CO之質量流率 mCO = 6.857 g h-1，(6) 觸媒量mS = 25 g。由實驗結果得知，使用MoS2/γ-Al2O3觸媒不僅可利於醇類產物之產出，亦可減少烷類的生成。當溫度升高由423, 473, 523至573 K時，CO之轉化率(XCO)及C1-C3 (CH4 – C3H8)烷類之生產速率(R)亦隨之增高。於T = 573 K時，XCO = 8.19%，CH4之R = 194.1 mg h-1，選擇率(S) = 34.57%。至於C2H5OH (EOH) 之生成，則以T = 523 K時之R (= 134.25 mg h-1)為最高，其相關之XCO = 8.10%，SEOH = 51.98%。若T增高至573 K，則EOH會分解成其他低碳之碳氫化合物(hydrocarbons, HCs)，例如C1-C3烷類。故若要產製較大量之醇類同時減少烷類之量，其溫度以523 K為最適宜。使用MoS2/γ-Al2O3觸媒於523 K溫度下，改變不同H2/CO配比，結果顯示H2/CO = 1時不利於醇類液化之反應，XCO、REOH及SEOH降低至7.55%、110.46 mg h-1及44.81%。使用Pt/γ-Al2O3觸媒時，CO之轉化率降低至6.79%，其反應產物中以CH3OH (MOH)為主要產物，但其生成速率及選擇率分別高達395.63 mg h-1和84.93%。然而由於Pt易受反應氣體CO之毒化，參與反應約5小時內即明顯失活，因此須適時再生俾便作為連續式反應系統使用之觸媒。本研究之對照實驗為使用γ-Al2O3且未添加水分，於反應溫度523 K時，其CH4、C2H6、CH3OH及C2H5OH之生成速率分別為0.34、0.04、0.029及0.368 mg h-1，其值甚低；其他碳氫化合物之C3H8、C4H10、CH3CHO、C3H7OH及C4H9OH則未生成。故添加MoS2/γ-Al2O3和Pt/γ-Al2O3觸媒有助於醇類之生成。其中MoS2/γ-Al2O3亦會有助於C1-C3烷類及CH3CHO之生成。水分之添加使醇類產物之產率(Y)較不提供水份之結果增加0.63% (=5.59% - 4.96%)，其它非醇類產物Y在水份添加之後減少1.00%。較不添加水份之結果烷類選擇率減少5.78% (= 26.96% - 20.91%)，醇類選擇率增加4.87% (= 70.7% - 65.83%)。

關鍵字

合成氣；合成氣轉化反應；醇；鉬；二硫化鉬

並列摘要

This study examined the feasibility and operation performance of reforming of synthesis gas (syngas, CO and H2) via high pressure catalytic packed bed (HPCPB) process. The effects of variation of temperature (T), change of H2/CO ratio, addition of MoS2/γ-Al2O3 and Pt/γ-Al2O3 catalysts and presence of H2O vapor on the conversion of CO (XCO) and the production rates (R), selectivities (S) and yields (Y) of alcohols and other hydrocarbons (HCs) were elucidated. The experimental conditions, in general, were as follow: (1) total pressure of inlet gas, PST = 3.10 MPa or 450 psi (reading at 298 K), (2) temperature, T = 523 K, (3) gas flow rate, QG = 300 mL min-1, (4) H2/CO = 2 (vol./vol.), (5) mass flow rate of CO, mCO = 6.857 g h-1and (6) mass of catalyst, mS = 25 g. The results indicate that XCO and production rates R of C1-C3 alkanes for the case using MoS2/γ-Al2O3 increase with increasing T from 423, 473, 523 to 573 K. At T = 573 K, XCO = 8.19%, R of CH4 (RCH4) = 194.1 mg h-1 and selectivity S of CH4 (SCH4) = 34.57%. As for the production of C2H5OH (EOH), the maximum REOH (= 134.25 mg h-1) takes place at T = 523 K with corresponding XCO = 8.10% and SEOH = 51.98%. At further high T = 573 K, the EOH is decomposed to other simple HCs, for examples C1-C3 alkanes. Thus, for the production of more alcohols with less alkanes, the temperature at 523 K is the optimal choice. At T = 523 K with H2/CO reduced to 1, the values of XCO, REOH and SEOH decrease to 7.55%, 110.46 mg h-1 and 44.81%, respectively. As Pt/γ-Al2O3 was used replacing MoS2/γ-Al2O3, at H2/CO = 2 the XCO decreases to 6.79%. The major product is MOH with RMOH and SMOH as high as 395.63 mg h-1 and 84.93%, respectively. However, due to the cause that Pt was poisoned by CO, Pt/γ-Al2O3 was deactivated after 5 h reaction, being not suitable for the long-time reaction requirememt. As for comparation, the use of γ-Al2O3 gives very low values of RC1, RC2, RC3, RMOH and REOH of 0.34, 0.04, 0.029 and 0.368 mg h-1 ,respsctively. No production of C3H8, C4H10, CH3COH, C3H7OH and C4H9OH were detected. It comes to the results that MoS2/γ-Al2O3 and Pt/γ-Al2O3 contribute to the formation of alcohols. However, the use of MoS2/γ-Al2O3 also yields C1-C3 and C3HCHO. Moreovre, the introduction of H2O vapor results in the increase of yield of alcohol of about 0.63% (=5.59% - 4.96%), and the reduction of that of non-alcohol products of 1.0% (= 3.14% - 2.14%), respectively. As for the selectivity, the presence of H2O vapor enhances the S of alcohol of 4.8% (= 70.7% - 65.83%) while decreases that of alkanes of 5.78% (= 26.96% - 20.91%).

並列關鍵字

Catalytic synthesis ； liquefaction ； MoS2/γ-Al2O3 ； Pt/γ-Al2O3 ； alcohol

參考文獻

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連續式觸媒催化合成產製燃料及化學品之研究

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