稀土基催化裂化钝镍剂的抗镍性能及其机理

利用催化裂化平衡催化剂ＣＨＺ ２ 考察了稀土元素ＲＥ的钝镍性能。实验结果表明，适量的ＲＥ钝镍剂能明显降低催化裂化反应的比氢气量和比积炭值，提高汽油收率，具有较明显的钝镍效果。程序升温还原实验和ＸＲＤ物相检测发现，在ＦＣＣ 再生温度（ 约７００ ℃） 下，ＲＥ和沉积在催化剂表面上的高价镍反应生成ＲＥＮｉＯ３ 晶相。ＲＥＮｉＯ３ 中的镍在ＦＣＣ 反应温度（ 约５００ ℃）下不易被氢气还原，这就有效地封闭了镍，抑制了镍的脱氢生焦活性。ＮＨ３ － 程序升温还原测定表明，当ＲＥ与镍的原子比大于０ ．４ 时，催化剂表面上的中强酸和强酸总量降低，导致烃类裂化活性下降，当ＲＥ与镍的原子比为０ ．３～０ ．４ 时，钝镍效果最佳

MECHANISM AND EFFECTS OF NICKEL PASSIVATION ON FCC CATALYSTS BY RARE EARTH ELEMENT

A nickel passivator taking rare earth (RE) element as an effective component has been found to be able to reduce the yields of hydrogen and coke. The mechanism of nickel passivation was investigated by XRD, TPR and NH-3|TPD methods. The experiment results show that under the condition of FCC regeneration, a stable compound RENiO-3 forms by chemical reaction of RE and depositing Ni {2 } and Ni {3 } on the surface of FCC catalyst. RENiO-3 is more difficult to be reduced by hydrogen than NiO under the condition of FCC reaction. Therefore, the dehydrogenation and coke formation activity of FCC catalyst is diminished. At the same time, the migration of nickel to the acid sites of FCC catalyst is inhibited. The gasoline yield as well as the number of acid sites of catalyst would decrease, if the atomic ratio of RE to nickel is more than 0.4. Therefore, the optimum atomic ratio of RE to nickel is from 0.3 to 0.4.