用于催化热裂解的ZSM-5分子筛改性研究

【作者】 蔡涛；

【导师】 胡望明；

【作者基本信息】 浙江大学 ， 化学工程， 2005， 硕士

【摘要】 催化热裂解技术是以减压馏分油和渣油为原料,使用以ZSM-5分子筛为主要活性组元的固体酸催化剂,在催化裂化装置上,在一定的工艺条件下生产乙烯和丙烯为主的低碳烯烃的一项新工艺。本课题对催化热裂解催化剂的活性组分进行了小试及工业放大试验,并对其反应机理进行了初步研究。 使用Ca、Mg等碱土金属,Ag、Cu等Ib族金属以及Fe、Co、Ni等Ⅷ族金属的硝酸盐,采用浸渍和离子交换等方法,对ZSM-5分子筛进行改性处理。并采用X射线荧光光谱法、红外光谱法对分子筛改性前后的物化性质进行了表征。 采用纯烃脉冲微反实验装置评价了改性ZSM-5分子筛的催化热裂解性能。试验结果表明,随着反应温度的提高,碳二组分的产率均提高,而碳三组分的产率降低;随着改性分子筛上金属氧化物含量的增加,碳二组份和碳三组分的产率均有所增加,其中Ib族金属改性的分子筛产物具有较高的选择性。 在重油微反装置上进行了金属改性分子筛的催化热裂解试验,结果表明,Ib族金属改性的分子筛具有较好的乙烯产率,同时丙烯产率也较高;Ⅷ族金属改性的分子筛的脱氢能力很强,烯烃产率较低,积碳非常明显;碱土金属改性的分子筛乙烯产率和丙烯产率均较低。 在小试的基础上进行了工业放大试验,制成了催化热裂解催化剂并进行了工业应用试验,取得了良好的效果。更多还原

【Abstract】 Catalytic thermal cracking technology, making use of VGO and residue as feedstock and solid acid catalyst which consists of ZSM-5 zeolite as major activity components, is a new process of producing low-carbon olefines composed of ethylene and propylene mainly under certain condition in FCC plant. This paper concerns the small-scale test and industrial amplification test in activity components of catalytic thermal cracking catalyst respectively, as well as the initial research in reaction mechanism.Utilizing alkaline earth metals Ca, Mg, etc., Ib family metals Ag, Cu, etc., and the nitrate of VIII family metals Fe, Co, Ni, etc., and adopting dip-moulding and ion exchange method,ZSM-5 zeolite is modified, and its physical and chemical characteristics is indicated by XRD, SEM, MAS NMR and IR.Catalytic thermal cracking performance of modified ZSM-5 zeolite is evaluated through pure hydrocarbon impulsive micro-reaction pilot unit. The test results indicate that C2 components yield is improved, but the yield of C3 components decreased as the increase of reaction temperature. While the content of metal oxide in modified zeolite increases, the yield of both C2 and C3 components are enhanced, and zeolite of modified by Ib family metals has better selectivity.Catalytic thermal cracking tests of metal modified zeolite are carried out in heavy oil micro-reaction unit. Test results show that zeolite modified by Ib family metals has much higher ethylene yield, as well as the yield of propylene at the same time, and the second one modified by VIII family metals have very excellent dehydrogenation ability, lower olefine yield and obvious carbon accumulation, and the third one modified by alkaline earth results lower yield of both ethylene and propylene.On the basis of small-scale test, industrial amplification tests are executed, and the synthesized samples of catalytic thermal cracking catalyst are applied in commercial application test. The application effects are excellent.Upon test foundations, reaction mechanism of catalytic thermal cracking is explored. The distribution of acid site in zeolite determines ethylene yield of catalytic thermal cracking reaction. Ethylene yield improves with the increases of L-acid site amounts in zeolite. Therefore, not only can L-acid site catalyze the carbonium ion reaction, but also promote free radical reaction under different temperature condition and acid strength respectively. The types of metal loaded in zeolite and its electronegativity are the reasons that cause the transformation of L-acid sites. The more negativity of alkaline earth metal and VIII family metal corresponds to higher ethylene yield, while the case of Ib family metal is the reverse.更多还原