石油烃催化裂解／裂化过程提供了包括乙烯、丙烯在内的低碳烯烃、汽油和柴油等轻质油品以及其他重要的石油化工产品，在国民经济中具有重要的地位。虽然其在工业上已广泛的应用，但是由于研究手段的限制对于该过程规律的认识（包括油剂接触和反应规律等）并不深入。基于上述原因，本文力图用下行床反应器“近平推流“的特点研究石油烃裂解过程规律，考察产物的生成机理，寻找最优操作条件并建立基于反应机理的宏观反应动力学模型。由于短停留时间条件下油剂接触效果对产品分布有重要影响，本文因而采用了催化剂染色方法开发了一套切实可行的定量研究下行床反应器油剂接触效率的系统。该研究表明剂油比与油剂接触效率呈线性增长关系，且符合以下关系式；提高气液比会增加原料油的喷射动量，气液比与油剂接触效果的关系同时受剂油比的影响，下行气流对油剂接触效果影响较小；射流入射方向与催化剂运动方向的夹角越大越有利于提高油剂接触效果。＃建立了处理量在1.8Kg/h，内径为14mm的小型循环下行床反应器装置，分别进行了石油烃催化裂解／裂化实验。通过研究各种产物的生成规律，并结合对催化剂失活的研究成果，发现石油烃催化裂解/裂化过程中自由基反应和正碳离子反应竞争共存，其中干气的生成主要由自由基反应控制，反应为气相非催化反应，活化能高。而正碳离子反应影响了其他产物的生成，且催化剂失活程度对LPG和汽油中烷烃生成的影响要大于对烯烃的。根据对产物生成机理的分析，提出生产低碳烯烃（乙烯、丙烯和丁烯）时应当尽量采用大剂油比，较高的反应温度和相应的短停留时间，且停留时间分布较为均匀的操作原则。经过将DCP过程与下行床DCC、提升管DCC、HCC、CPP等过程相对比，证明了在下行床反应器中应用上述原则在提高三烯总量和生产富含芳烃的液相产品方面具有优势。通过上述分析，基于对反应机理和催化剂失活对产物生成的认识，将原料油和汽油按照族组成划分，建立了十二集总石油烃催化裂解/裂化宏观反应动力学模型。在忽略原料油和汽油组成的影响后，提出了六集总简化模型，回归出了催化裂解过程的模型参数，且实验数据与计算值相吻合。
Hydrocarbons cracking process supplies many important petrochemicals, e.g. light olefins (ethylene, propylene, and butylenes) and light oils (gasoline and diesel oil). Although it is widely used, the understandings of the different processes that occur during hydrocarbons cracking, such as the reaction mechanism and the nature of the liquid-solid contact, are not well understood. The aim of this thesis is to determine the reaction mechanism and kinetics of hydrocarbon catalytic cracking in a downer reactor. The downer has the useful features of less axial backmixing and good plug flow behaviour, and an ultra-short contact time.Contact between the liquid feed and the catalyst is a key factor that determines the interfacial area for mass transfer and reaction, and plays a very important role in product selectivity. This work developed a quantitative measurement system to measure liquid-solid contact efficiency in a downer reactor. Liquid-solid contact efficiency increases linearly with the catalyst-oil ratio. It has a more complicated relationship with the gas-liquid ratio because the contact efficiency of the liquid and solid is also affected by the catalyst-oil ratio at the same time. The gas velocity has little effect on liquid-solid contact. Sufficiently big angles of the nozzles with respect to gravity should be used for good liquid-solid contact efficiency.＃A downer reactor of 14 mm i.d. and 1.8 kg.oil/hour capacity was built to study the influences of temperature, residence time and the catalyst-oil ratio on deep catalytic cracking (DCC) and fluid catalytic cracking (FCC). The results showed that the reactions of carbocation and free radical intermediates are the key reactions. Dry gas is produced via a free radical mechanism in the gas phase and is not affected by catalyst deactivation. C3+ hydrocarbons are produced via a carbocation mechanism and are significantly affected by catalyst deactivation. Catalyst deactivation has different effects on the yields of olefins and paraffins whether in the LPG or in gasoline fraction. In order to enhance light olefins production, hydrocarbons cracking process should operate under higher catalyst-to-oil ratios, a relatively higher temperature and a shorter contact time. In comparison with DCC, CPP and HCC, DCP (Downer Catalytic Pyrolysis) is proved its advantages in production of light olefins and liquid product with higher value.A twelve lump kinetics model, which is based on the reaction mechanism and includes catalyst deactivation, was developed to describe the cracking reactions. Feed oil and gasoline were lumped according to cracking. A six lump kinetics model without the subdivision of feed oil and gasoline was developed to describe the DCC process. Kinetics parameters were obtained by fitting the reaction results in the temperature range from 610℃ to 640℃ using a new method. The results of the model of the cracking of gasoline and DAO agree well with experimental data.
