ZSM-5/Y复合分子筛的酸性及其重油催化裂化性能

 ZSM-5/Y是本研究组合成的一种新型复合分子筛材料. 用“两次交换,两次焙烧”和磷 酸氢二铵浸渍方法对该复合分子筛材料进行了改性,采用红外光谱表征了复合分子筛的酸性,研究了磷改性对复合分子筛样品羟基区谱学性质的影响,并与相应的机械混合分子筛样品进 行了对比. 红外光谱数据表明,磷改性后复合分子筛的B酸(主要是中强酸)增加,而机械混合分子筛在各个酸强度区域的B酸量和L酸量都减少. 以新疆重油为原料考察了改性后复合分子 筛样品和机械混合分子筛样品的催化裂化性能. 与相应的机械混合分子筛催化剂相比,磷改 性复合分子筛催化剂具有较高的柴油选择性,其柴油产率增加了4.1个百分点,柴汽比增加了0.11,总轻油产率与机械混合分子筛相当. 用气体产物中的CMR(裂化机理比)和C3/C4比 值分析了复合分子筛的催化性能与其聚集体结构的关系.

Acidity and Catalytic Performance of ZSM-5/Y Composite Zeolite for Heavy Oil Cracking

Studies of composite molecular sieve catalysts are very active subject in petroleum refining processes and have received much attention in recent years. A novel procedure for the preparation of ZSM-5/Y composite zeolite has been developed by in situ two-step hydrothermal crystallization of Y synthesis gel in our laboratory. In this paper, the acid properties of the ZSM-5/Y composite zeolite were characterized by Fourier transform infrared spectroscopy. To meet the demand of catalytic cracking of heavy oil, the composite zeolite was modified by ion-exchange and calcination and then by phosphorus. The influence of phosphorus modification on the hydroxyl groups of the ZSM-5/Y composite zeolite was studied by comparing with the mechanical mixture of ZSM-5 and Y zeolites. The data of infrared spectroscopy showed that B acid sites of the composite zeolite was increased after phosphorus modification, especially for the acid sites with medium strength, while both B and L acid sites with various strength were decreased for the mechanical mixture. The catalytic cracking performance of the ZSM-5/Y composite zeolite was compared with that of the mechanical mixture by using a microactivity test reactor with Xinjiang heavy oil as feed. The results indicated that the composite zeolite with spheroid agglomerate morphology showed higher diesel yield and diesel to gasoline ratio than the mechanical mixture, and gave a light oil (gasoline+diesel) yield equivalent to the latter. CMR (cracking mechanism ratio) and C 3/C 4 ratio in the gas product were used to analyze the relations of the cracking performance with the spheroid agglomerate of the composite zeolite. The catalytic cracking performance was correlated with the structure and acid properties of the ZSM-5/Y composite zeolite.