裂化催化剂失活动力学及平衡催化剂活性模型

基于催化剂全混流流动状态和呈指数形式的催化剂年龄概率密度函数,经催化剂失活动力学方程推导,确定了关联催化剂碳含量、金属沉积量、催化剂置换率、再生器温度和水蒸气分压的平衡催化剂活性或微反活性模型方程。对工业催化裂化装置操作数据进行模拟计算,确定了催化剂失活模型参数,建立了具有较高模拟计算精度的裂化催化剂失活动力学和平衡催化剂活性模型。比较模型参数大小可知,V沉积对催化剂活性的影响最大,其次是Ni和Fe,Na的影响最小。模型预测结果表明,随着平衡催化剂金属沉积量或碳含量减少,催化剂单耗增大,平衡催化剂活性或微反活性逐渐增大。适当降低再生器温度和催化剂藏量有利于提高平衡催化剂活性。     

Five-lump kinetic model with selective catalyst deactivation for the prediction of the product selectivity in the fluid catalytic cracking process

The effective simulation of the fluid catalytic cracking (FCC) operation requires a good understanding of many factors such as, reaction kinetics, fluid dynamics, and feed and catalyst effects. The different product slates that can be obtained are the consequence of a complex reaction scheme including cracking, isomerization, hydrogen transfer, oligomerization, etc. Furthermore, the catalyst deactivation may affect each one of the reactions in different ways, which creates an additional reason for different variation with time-on-stream of the yield to each product. On the basis of the experimental data of the FCC pilot plant operated in Chemical Process Engineering Research Institute (CPERI, Thessaloniki, Greece), a lumping model was developed for the prediction of the FCC product distribution. The lumped reaction network involved five general lumps (gas oil, gasoline, coke, liquefied product gas, and dry gas) to simulate the cracking reactions and to predict the gas oil conversion and the product distribution. The paths of catalyst deactivation were studied and a selective deactivation model was adopted that enhances the fundamentality and accuracy of the lumping scheme. The hypothesis of selective catalyst deactivation was found to improve the product slates prediction. Models with different assumptions were examined, regarding the behavior of the catalyst, as deactivated, and its effect on the reactions of the lumping scheme. A large database of experiments, performed in the FCC pilot plant of CPERI was used to verify the performance of the models in steady state unit operation. The simulation results depict the importance of incorporating selective catalyst deactivation functions in FCC lumping models.     

催化裂化催化剂抗重金属技术应用与进展

简述催化裂化原料油中镍、钒、铁、钙、钠等重金属对催化裂化催化剂选择性和活性的影响,介绍抗镍、抗钒、抗铁和其他重金属技术的应用和进展,为新型抗重金属催化裂化催化剂的研究和发展提供思路。     

催化裂化催化剂生产过程中分子筛粉碎技术的应用

在催化裂化催化剂生产过程中为了提高超稳分子筛的有效利用率,提升产品质量,使用了一系列超稳分子筛粉碎技术。对超稳分子筛聚集的原因及粉碎技术进行了对比分析,重点分析了介质超细研磨粉碎技术对催化剂质量指标的影响。造成超稳分子筛粒子聚集的主要原因是NaY分子筛合成过程中粒子间相互吸附,后续分子筛交换改性工序对分子筛粒度分布影响较小。介质超细研磨机和干磨粉碎技术对粉碎超稳分子筛效果明显,能够有效降低分子筛粒径,在催化裂化催化剂生产过程中介质超细研磨机的应用效果较好。经粉碎后的超稳分子筛能够明显降低催化裂化催化剂的磨损指数,提高微反活性。     

Modelling the kinetics of fast catalytic cracking reactions

Instantaneous kinetic constants and gasoline selectivities have been determined for catalytic cracking of n-hexadecane. The pulse technique was used in order to model the sequential build-up of coke which occurs on cracking catalyst within a riser transport-line reactor. The total amount of hydrocarbon injected per unit weight of catalyst was between 0 and 10. The mathematical model used to analyze the data was based on the unsteady state mass balance of the microcatalytic reactor with the assumption of plug flow. Results suggest a fast deactivation process during the run with fresh catalyst, while regenerated catalyst showed a slower deactivation. The catalyst regenerated three times evidenced a low apparent activation energy when temperature was increased from 500°C to 550°C.     

烯烃裂解增产丙烯催化剂再生性能

由于烯烃裂解技术反应自身的特点,催化剂容易积炭失活,需要进行多次再生,因此,催化剂的再生性能对烯烃裂解技术至关重要。在实验室对中国石化中原石油化工有限责任公司烯烃裂解工业装置的ZSM-5催化剂进行了多次反应和再生试验,考察其烯烃裂解反应性能,并运用TG、XRD、NH₃-TPD、氮气物理吸附以及SEM等对再生前后的催化剂样品进行表征。结果表明,开发的烯烃裂解催化剂经过13次的反应再生过程,新鲜催化剂与再生催化剂的比表面积和孔容基本相同,烯烃转化率、丙烯及乙烯收率无明显变化,烯烃转化率仍大于73%,丙烯和乙烯收率分别大于32%和10%。且催化剂骨架结构和酸中心稳定,在多次反应与再生过程中的酸量保持不变,具有良好的再生性能。     

重油催化裂化催化剂RCH的研究

RCH催化剂是继我国第一代超稳Y型催化裂化催化剂之后,开发研制的新型渣油裂化催化剂。该剂沸石含量低,而在裂化性能、产品收率、焦炭选择性等方面均与国内外同类型催化剂相当,可替代进口催化剂在重油催化裂化(RFCC)装置上使用;该剂更具有平衡活性和轻质油收率高、稳定性好、裂化重质油能力和抗重金属污染能力强等特点,同时制备工艺先进,流程简单,属国际先进水平。     

A new approach on catalytic cracking catalyst deactivation

The existence of acidic species other than those of vanadic acid is suggested to be responsible for the FCC catalyst deactivation. These species would come from SO _s adsorption on the catalytic surface which would react with the most acid sites of the zeolite, ultimately leading to loss of crystallinity.     

催化裂化催化剂磨损指数分析方法

对催化裂化催化剂磨损指数测定方法进行研究,通过实验优化测定催化剂磨损指数的预处理条件,考察焙烧温度和焙烧时间、催化剂用量、气体流速、纸筒对磨损指数的影响。结果表明,催化剂焙烧温度650 ℃,焙烧时间1 h,催化剂用量10 g,气体流速21 L·min^-1,选择纸筒时系统压力不超过30 kPa。催化剂磨损指数绝对偏差最大值0.16%,最小值0,准确度较高。催化剂磨损指数相对标准偏差低于5%,重复性较好。     

A molecular kinetic model incorporating catalyst acidity for hydrocarbon catalytic cracking

This work built a molecular-level kinetic model for hydrocarbon catalytic cracking, incorporating the catalyst acidity as the parameter to estimate reaction rates. The n-decane and 1-hexene co-conversion catalytic cracking process was chosen as the studying case. The molecular reaction network was automatically generated using a computer-aided algorithm. A modified linear free energy relationship was proposed to estimate the activation energy in a complex reaction system. The kinetic parameters were initially regressed from the experimental data under several reaction conditions. On this basis, the product composition was evaluated for three catalytic cracking catalysts with different Si/Al. The Bronsted acid and Lewis acid as the key catalyst properties were correlated with kinetic parameters. The built model can calculate the product distribution, gasoline composition, and molecular distribution at different reaction conditions for different catalysts. This sensitive study shows that it will facilitate the model-based optimization of catalysts and reaction conditions according to product demands.     

催化裂化结焦反应的研究进展

综述了近年来催化裂化结焦反应的研究进展情况,重点介绍了结焦反应的影响因素、焦炭对催化反应的影响、结焦机理以及焦炭的表征4个方面。研究认为,原料的性质、反应温度、催化剂的类型等因素均会对焦炭的生成产生影响。焦炭可以导致催化剂的失活,而位于孔道内部的焦炭对反应物或产物的扩散不利,进而影响产物的分布。研究表明,各种烃类组分形成焦炭的过程都必须经历芳香烃这一步。对于结焦催化剂可以采取多种表征手段,其中利用XPS以及GC-MS对焦炭进行表征的报道日益增多。尽管国内外对于催化裂化结焦反应的研究开展较早,然而探究焦炭的具体成分仍存在不小的困难,通过先进的表征手段鉴定焦炭中高缩合度芳烃组分以及如何减小催化裂化催化剂的结焦量将成为未来的研究方向。     

Catalyst decay in the presence of chain processes in catalytic cracking

The Chemical events involved in cracking and catalyst decay are examined in order to ascertain the possible course of catalyst decay. We find that, regardless of whether site activity is lost by “sudden death” or by gradual “inhibition”, the time course of catalyst decay under a wide variety of assumptions is described by the function ā(t) = (1 + Gt)–^N′. Under certain conditions, however, sites on their way to complete deactivation may undergo reactivation by the desorption of an inhibiting species. In such cases, our models predict the existence of a lower activity condition which can be time invariant or, after being established by an initial rapid decay, the intermediate less-active condition evolves to a final, inactive state. Furthermore, if some of the intermediate steps on the way to complete deactivation lead to site activities higher than those of the pristine sites, a sigmoidal curve of conversion versus time on stream can result.     

Challenges, catalyst technology and catalytic solutions in resid FCC

The concurrent evolution of resid fluid catalytic cracking (RFCC) processes and catalyst technology over the years is discussed. Resid FCC catalysts today are designed making use of the following features: (a) High activity, selectivity and metals resistant zeolites; (b) Highly accessible catalyst architecture for optimal site utilization, bottoms cracking, Conradson carbon residue (CCR) conversion and easy stripping; and (c) Specially designed metal-support interaction systems to reduce the detrimental effects of metal contaminants. The future will require even more robust RFCC catalyst systems. These catalyst systems should be very accessible and effective in cracking large hydrocarbon molecules and should have the capability to handle contaminants such as metal-, sulfur-, and nitrogen-compounds. Conversion of CCR to non-coke components will be crucial in order to reduce the delta coke and hence improve the processability of heavier resids. Processability here is meant not only in terms of coke and heat balance considerations, but also involves avoiding fouling of the unit hardware by unconverted heavy hydrocarbons and coke precursors. Last, but not the least, present and future catalyst technology must be formulated and adapted to the specific commercial process unit needs and constraints, thus leading to the most cost effective solution for the refiner.     

Deactivation of cracking catalyst in short contact time reactors: Alternative models

Several mathematical models have been used to describe the deactivation of cracking catalysts by coke. For the case of gas oil cracking under short contact times (less than 20 seconds) it was found, using data from two different experimental reactor units, that an exponential decay function or a power law function could equally represent the data. Both functions are forms of the general hyperbolic decay expression; however, the power law assumes the unrealistic limits of infinite catalyst activity at zero time-on-stream and requires two parameters to describe deactivation. This work shows that the simple first order decay function is an effective equation to be used in describing catalyst activity decay for short reaction times.     

Experimental investigation of the catalytic cracking of methane over a supported Ni catalyst

TGA experiments on the catalytic cracking of methane and methane diluted with hydrogen over a 5 wt% Ni/γ‐alumina catalyst at 500°C and 1 and 10 bar are described. Carbon deposition on the catalyst, as expressed in specific weight of carbon, varies with time. Eventually, the deposition stops because of deactivation. The specific weight at this point depends on the hydrogen partial pressure and there is also a weak dependence on the degree of contact between catalyst particles. A model based on assuming carbon deposition proceeds through whisker formation and growth, and deactivation occurs through encapsulation adequately describes the experimental observations up to 20 vol% hydrogen in the feed.     

催化裂化催化剂再生过程中的氮化学进展

从流化催化裂化待生催化剂中含氮化合物的主要类型和生成机制、再生过程中含氮化合物的转化途径以及降低再生过程中氮氧化物排放的相应控制措施等几个方面,综述了流化催化裂化催化剂再生过程中的氮化学研究进展。     

催化裂化催化剂铁污染研究进展

介绍近年关于FCC催化剂铁中毒现象的研究进展。平衡剂上铁存在新鲜催化剂自身铁、原油原有铁和过程铁3个来源,其中,高酸原油的过程铁含量已不容忽视。催化裂化过程中,原料油中以环烷酸铁为主的铁物种不断沉积在催化剂的表面,与催化剂中的钠、氧化硅形成低熔点共熔物,形成覆盖平衡剂表面的光滑结构,堵塞催化剂的孔道,导致汽油产率下降,严重影响装置稳定运行。根据铁中毒的机理研究,提出加强人员技术交流与培训、提高分析检测频次、应用抗铁污染催化剂、铁中毒解决方案等预防和应急措施,为加工高铁含量原料油催化裂化装置的长期稳定运行提供技术参考。     

The effect of pre‐coking on the activity and selectivity of the catalytic cracking of squalane

The pre‐coking of cracking catalysts has been reported to increase the yield of light cycle oil from fluid catalytic cracking. The present studies investigating an equilibrated catalyst show that this is not the case. The effect of pre‐treating equilibrated catalysts with coke and with ammonia shows that conversion was decreased in both cases and the product selectivity of the process changed. Both coke and ammonia were found to decrease site density, reducing the importance of hydrogen transfer reactions. Increased yields of light cycle oil as a result of pre‐coking can only be expected with fresh catalyst, where small amounts of coke deactivate the most acidic sites. Such sites have already been deactivated on equilibrated catalyst. Copyright © 2004 Society of Chemical Industry     

氧化物催化剂上石脑油催化裂解制乙烯的研究

使用固定流化床,考察了氧化物催化剂催化裂解石脑油制乙烯的反应。研究结果表明,温度、空速和水油比对裂解产物分布有直接影响。在反应温度700 ℃、空速0.75 h^－1和水油质量比3∶1条件下,得到最大的乙烯收率为32.93%。     

FCC催化剂的镍中毒

本文总结了关于流化催化裂化（FCC）催化剂上镍沉积方式、形态和镍沉积对催化裂化反应影响的研究成果。分析了镍中毒引起催化剂失活的原因,对当前FCC加工过程中防止镍中毒的方法进行了总结和比较,并对今后国内FCC催化剂镍中毒研究课题提出建议。