重质油催化工艺多产乙烯过程中污染铁对催化剂性能发挥的影响

采用N2吸附容量法、BET、热重原位NH₃-TPD、吡啶吸附红外光谱(Py-IR)法分析了污染铁对重油制取乙烯专用催化剂性能发挥的影响。结果表明,有机铁污染催化剂微孔部分的比表面积和孔体积都有明显损失,低于200℃的NH₃-TPD脱附峰代表的弱酸中心损失约为26%。L酸点和B酸点的混合酸对重油催化制乙烯中甲烷、氢气的产生起到关键的作用。环烷酸铁污染后的催化剂沸石晶内酸性大量损失,预示在重油催化制乙烯工艺中有机铁污染催化剂中毒部分主要位于沸石晶内,而非外表面或微晶的孔口处;且原油中Fe³⁺比Fe²⁺更具有金属活性,表现出的氧化脱氢性能更为明显。在重油催化制乙烯工艺中,铁污染催化剂会导致氢气、焦炭的急剧增加,丙烯产率也会明显减少,而干气和汽油产率基本不受影响。

Effect of Iron Poison on the Catalyst in Heavy Oil Catalytic Producing Ethylene Process

By using infrared spectroscopy, N₂ adsorption, BET, in-situ NH₃-TPDand TG pyridine adsorption (IR), the effect of iron contamination on the catalyst of heavy oil catalytic producing ethylene process was studied. The results indicated that after contaminated organic iron the microporous’ surface area and pore volume of catalyst were significantly decreased and about 26% of the peak area (<200℃ desorption peak in NH₃-TPD curve) representing weak acid center lost. The mixed acid of L acid and B acid seemed to be the key role in producing hydrogen and methane in heavy oil catalytic producing ethylene process. The massive loss of acids in zeolite after iron naphthenate pollution indicated that in heavy oil catalytic producing ethylene process, organic iron poison was mainly located in the inner part of zeolite, rather than the outer surface of zeolite or microcrystalline entrance. And Fe³⁺ in the crude oil was more active than Fe²⁺, because the oxidative dehydrogenation reactions were more obvious. In heavy oil catalytic producing ethylene process, iron contamination on catalyst would lead to sharp increase of hydrogen and coke, and significant reduction of propylene yield, while the dry gas and gasoline yields were basically not affected.