Abstract
低碳數的直鏈烷烴 ( C4 - C7 ) 的加氫異構化反應，被使用在石油煉製 的商業製程中，用來提高汽油的辛烷值，隨著環保意識的提高，含鉛汽油 的使用逐年降低，使此製程更顯得重要。本實驗是研究正庚烷的加氫轉化 反應，採用固定床反應器，以含鉑金屬的絲光沸石與 Beta 沸石和十一型 矽鋁分子篩 ( SAPO-11 )及非結晶型矽鋁氧化物為觸媒，反應壓力為 14.7 - 600 Psi ，反應溫度為 240 - 500℃ 範圍。分析在不同正庚烷轉 化率下反應的產物選擇率及產物的分佈情形；並利用氫氣化學吸附法，程 溫加溫脫附氨法及元素分析法來分析觸媒的金屬分散度情形及酸性中心強 度和含量。由實驗結果得知，正庚烷加氫反應的異構物產率及選擇率與反 應壓力，觸媒的孔洞性質及觸媒的製備方式有關。在雙功能觸媒催化下， 正庚烷的反應過程主要有平行反應 ( parallel reaction process ) 及 連續反應 ( successive reaction process ) 兩種，而進行此二種反應 路徑的比率會受反應的壓力及觸媒的酸性中心含量的影響。另 Beta 對C7 的中間產物的空間阻礙比 Mordenite 小,因此在 Pt/H-Beta 沸石上壓力 對反應的影響遠小於壓力對在 Pt/H-Mordenite 上反應的影響。我們並發 現正庚烷除單分子反應 ( monomolecular reaction ) 外也會進行雙分子 反應 ( dimerization cracking ) ，但以單分子反應為主，在常壓反應 時雙分子反應所佔的比率較高壓反應時大。 The reaction mechanism and scheme of hydroconversion of n- heptanecatalyzed by H-form mordenite and beta zeolites with the promotion of platinumof 0.5 wt% has been studied by measuring product distributionsvia conversion and reaction pressure in the range of 1 to 40.8 atm at temperature of 210~330℃. Isomerization and cracking products are formed either simultaneouslyor consecutively as a function of reaction pressure and pore structure as well as acid sites density of zeolites. With less hindered intraframework void space, Pt/BEA was found to be close to an ideal bifunctional catalyst for n- heptane transformation and isoheptane formation andthe effect of pressure is less pronounced. The isomerization selectivity on Pt/MORwas significantly improved by increasing reaction pressure and Si/Al ratio of HMOR. This pressure effect on isomerization selectivitymay be related to the activation of acid sites for the generation of C7carbenium ions and to the reduction of dehydrogenation of heptaneto heptene.