The Influence of Rare Earth Modification on SAPO-11 Molecular Sieve for Lube Oil Isodewaxing

The Influence of Rare Earth Modification on SAPO-11 Molecular Sieve for Lube Oil Isodewaxing
　　The paraffins in lube base oil weaken the low-temperature properties, which should be removed. The isomerized dewaxing technology has advantage in high yield, low cost and perfect base oil quality, which uses“metal-acid center”bifunctional catalyst, such as Pt/SAPO(Silicoaluminophosphate) -11. The resource of RE (rare earth) in China is abundance. Making use of RE has important significance. In this research, two stepwise experiments were carried out to accomplish the RE modification on SAPO-11.First of all, SAPO-11 molecular sieve was modified with La and Ce by impregnating and ion-exchanging methods. The modified samples were characterized by XRD, BET, PSD, FTIR and NH3-TPD, also evaluated by micro-reaction employed the dodecane as model compound. The Block Neodymium magnets results indicated that after RE modification, especially for the La-exchanged sample, the composition of molecular sieve was changed and the crystallinity decreased. Owing to the RE cations loaded on the surface of molecular sieve, which could be regarded as the Lewis acid, the amounts of Lewis acidic sites increased and further the B/L reduced. Meanwhile, the ability of RE cations to acquire electron is weaker than Al3+, so the bond strength of bridged hydroxyl after modification was decreased.
　　Furthermore, After RE modified, the selectivity decreased but the cracking activity increased, especially for the Ce samples.Afterward, base on the results of first stage, the SAPO-11 molecular sieve was modified by Ce in company with Zr using various methods. The modified samples were characterized by BET, H2-TPR, FTIR, and also investgated their performance in isomerization of n-paraffins by micro-reaction. Among all the catalysts in the second stage, the Ce/Ce, Zr impregnating samples’surface aera decreased slightly. The reductive temperature of PtO2 ascended. The Pt had lower metal dispersion and larger particle diameter when the surface area of http://www.999magnet.com/ carrier was smaller. The addition of Zr adjusted the acidity distribution, resulted in the B/L increase. The RE modified Pt/SAPO-11 had lower i-dodecane selectivity and yield. Moreover, the cracking activity enhanced and the optimal temperature debased after RE modified. The catalyst modified with CZ had relative higer B/L, but the selectivity of it was inferior to blank sample.To sum up, the RE modificaions made against the isodewaxing of lube base oil. 更多还原