Effect of Feedstocks on High‐Severity Fluid Catalytic Cracking

A novel fluid catalytic cracking (FCC) process, that utilizes a downer reactor, has been developed to enhance the yield of light olefins under high‐severity reaction conditions. The effect of heavier feedstock on this high‐severity fluid catalytic cracking (HS‐FCC) process has been investigated using a small‐scale HS‐FCC pilot plant (0.1 b/d). Hydrotreated and virgin vacuum gas oils (VGO), hydrotreated and virgin atmospheric residues (AR) were used as test‐feeds in a previous study. The yield of desired products, such as gasoline and light olefins, produced from virgin VGO cracking was 79 wt.‐%, which is much higher than that obtained from a conventional FCC process. In the case of hydrotreated VGO, the yield of desired products decreased to 76%, however. On the other hand, AR feeds exhibited a performance similar to VGO with a slight increase in coke formation. In this study microactivity test (MAT) results are reported in which the activity and selectivity of the Y‐zeolite based catalyst is evaluated. Kinetic modeling was also done based on a four‐lump reaction model.     

催化裂化轻汽油在ZSM-5分子筛催化剂上裂化反应的研究

以ZSM-5分子筛为催化剂，在小型固定床反应器上，进行了催化裂化轻汽油的裂化反应。考察了反应温度和空速对催化裂化轻汽油裂化反应气液相收率和产品分布的影响。实验结果表明，ZSM-5分子筛催化剂具有较强的裂化活性和氢转移活性。在保证裂化转化率的条件下，提高反应温度和空速可以抑制催化剂上氢转移反应的发生。以ZSM-5分子筛为催化剂上的催化裂化反应中，温度、空速是影响转化率和选择性的重要因素，因此可以通过改变温度、空速来提高目的产物的选择性。但是，单纯依靠改善反应条件，不能使目的产物的收率和选择性达到理想的程度，还必须对催化剂进行改性。ZSM-5分子筛催化剂上催化裂化反应的研究为ZSM-5分子筛催化剂的进一步改性，及ZSM-5分子筛催化剂在轻汽油催化裂解和汽油改质方面的进一步应用提供了试验依据。     

我国FCC催化剂的发展近况

阐述了国内近几年FCC催化剂在重油催化裂化、汽油降烯烃、脱硫及多产低碳烯烃方面的进展.提高抗重金属污染能力、用中孔沸石代替 ZSM-5小孔沸石及大幅度提高催化剂基质的活性仍是今后研发 FCC催化剂的热点.     

Fluid catalytic cracking feed hydrotreatment and its severity impact on product yields and quality

This paper investigates the effect of fluid catalytic cracking (FCC) feed hydrotreatment and its severity increase on product yields and quality obtained in a commercial and a laboratory MAT FCC units. The hydrotreatment of Ural heavy vacuum gas oil reduces not only sulfur, nitrogen, Conradson carbon and metals content in the FCC feed but also increases the mononuclear aromatic hydrocarbons content by 8% absolute at almost no change in the total aromatics content. Regardless of this 8% increase of the mononuclear aromatics in the hydrotreated FCC feed the conversion increase in both commercial and laboratory MAT units was only 2%. The severity increase in the FCC feed hydrotreater leads to a higher conversion in the FCC, higher hydrogen transfer rate that results in higher isobutane/butylenes ratio, lower gasoline olefins content, and higher gasoline motor octane number. The hydrotreatment of the Ural heavy vacuum gas oil exhibited the same changes in FCC catalyst selectivities: lower coke and LCO selectivities and higher gasoline selectivity in both commercial riser FCC unit that has between 2 and 3 s time on stream, and the fixed bed reactor MAT unit, that has 30 s time on stream.     

A process for producing ultraclean gasoline by coupling efficient hydrodesulfurization and directional olefin conversion

To solve the contradiction between ultradeep hydrodesulfurization (HDS) and octane recovery in clean gasoline production, this article proposes a novel two‐stage fluid catalytic cracking (FCC) gasoline hydro‐upgrading process with the selective HDS catalyst in the first reactor and the complemental HDS and octane recovery catalyst in the second reactor. The process achieved the relayed removal of sulfur‐containing compounds with different natures, providing itself with excellent HDS performance, and the hydroisomerization and aromatization of olefins in the second stage endowed the process with superior octane recovery ability and high product yield while remarkably reducing the olefin content of FCC gasoline. The process was also featured by low hydrogen consumption due to the low first‐stage olefin saturation and the balanced second‐stage hydrogenation and dehydrogenation. The two‐stage process developed here sheds a light for efficiently producing ultralow sulfur gasoline from the poor‐quality FCC gasoline of high olefin and sulfur contents. © 2012 American Institute of Chemical Engineers AIChE J, 59: 571–581, 2013     

β分子筛的催化裂化性能考察

以重油（70%新疆蜡油掺和30%新疆渣油）为原料,在FFB和ACE装置上对3种不同硅铝质量比β分子筛和工业应用的ZSM-5分子筛制备的催化裂化助剂的反应性能进行对比评价。结果表明,β分子筛对重油组分的裂化能力强于ZSM-5,对汽油组分的选择裂化能力弱于ZSM-5,液化气增加量小于ZSM-5,提高汽油辛烷值能力与ZSM-5相当。同时,随着β分子筛硅铝质量比升高,其催化裂化产物中汽油和总液收增加,重油减少。因此,β分子筛助剂适用于以追求燃料汽油生产为主的炼油企业,满足液化气增加不多和提高汽油辛烷值的需要。     

Study of direct and indirect naphtha recycling to a resid FCC unit for maximum propylene production

To satisfy the increasing propylene demand, direct and indirect naphtha recycling schemes around an existing resid fluid catalytic cracking (FCC) unit were investigated. To this aim, light cracked naphtha (LCN), heavy cracked naphtha (HCN) and a PolyNaphtha (PN) oligomerisation product were cracked under a wide range of operating conditions over a commercial Y zeolite based equilibrium catalyst. Experimental data were acquired in three different units: a fixed bed bench scale unit, a fixed fluidised bed unit and an adiabatic circulating fluidised bed pilot plant. It was shown that FCC naphthas require high operating severities to crack, and that even then their conversion remains relatively moderate. Hence, direct recycling to the main riser does not seem a viable pathway to increase propylene product. Feeding FCC naphthas to a second reaction zone operating at high severity allows to increase the propylene yield in a significant manner. Increasing conversion, however, not only leads to higher LPG and propylene yields, but also results in very high dry gas yields. An alternative scheme was proposed, in which the olefinic C₄ and C₅ fractions are converted into a naphtha fraction through oligomerisation in a dedicated unit before being recracked in the secondary riser. As the highly olefinic oligomerised effluent mainly consist of dimerised and trimerised butenes and pentenes, this feed is more easily cracked and high conversions can be achieved. This indirect interconversion of butenes and pentenes into propylene therefore effectively allows to convert these butenes and pentenes into propylene, resulting in a significant increase in propylene yield. Each of the three main naphtha recycle options (directly to the main riser, directly to a secondary riser or indirectly via a light olefin oligomerisation unit) have been analysed and compared to a base case. In the evaluation of each of these schemes, all heat balance effects, both on the riser and the regenerator side, have been accounted for. The proposed process scheme with an indirect recycle via an oligomerisation unit enhances the already inherent flexibility of the FCC unit. The naphtha recycle can be turned on or off, the second reaction zone can be used to crack naphtha or to crack resid feed to maximise throughput, while the effluent of the oligomerisation unit can be recycled to the FCC unit for propylene production or hydrogenated and sent to gasoline and kerosene pool.     

Study on reformulation of fluid catalytic cracking gasoline and increasing production of light olefins

The effects of reaction temperature, mass ratio of catalyst to oil, space velocity, and mass ratio of water to oil on the product distribution, the yields of light olefins (light olefins including ethylene, propylene and butylene) and the composition of the fluid catalytic cracking (FCC) gasoline upgraded over the self-made catalyst GL in a confined fluidized bed reactor were investigated. The experimental results showed that FCC gasoline was obviously reformulated under appropriate reaction conditions. The olefins (olefins with C atom number above 4) content of FCC gasoline was markedly reduced, and the aromatics content and octane number were increased. The upgraded gasoline met the new standard of gasoline, and meanwhile, higher yields of light olefins were obtained. Furthermore, higher reaction temperature, higher mass ratio of catalyst to oil, higher mass ratio of water to oil, and lower space velocity were found to be beneficial to FCC gasoline reformulation and light olefins production.     

动植物油生产清洁燃料和低碳烯烃的替代加工工艺

Since the production cost of biodiesel is now the main hurdle limiting their applicability in some areas, catalytic cracking reactions represent an alternative route to utilization of vegetable oils and animal fats. Hence, catalytic transformation of oils and fats was carried out in a laboratory-scale two-stage riser fluid catalytic cracking （TSRFCC） unit in this work. The results show that oils and fats can be used as FCC feed singly or co-feeding with vacuum gas oil （VGO）, which can give high yield （by mass）of liquefied petroleum gas （LPG）, C2-C4 oletms, tor example 45% LPG, 47% C2-C4 olefins, and 77.6% total liquid yield produced with palm oil cracking. Co-feeding with VGO gives a high yield of LPG （39.1%） and propylene （18.1%）. And oxygen element content is very low （about 0.5%） in liquid products, hence, oxygen is removed in the form of H2O, CO and CO2. At the same time, high concentration of aromatics （C7-C9 aromatics predominantly） in the gasoline fraction is obtained after TSRFCC reaction of palm oil, as a result of large amount of hydrogen-transfer, cyclization and aromatization reactions, Additionally, most of properties of produced gasoline and diesel oil fuel meet the requirements of national standards, containing little sulfur. So TSRFCC technology is thought to be an alternative processing technology leading to production of clean fuels and light olefins.     

Study of cracking FCC naphtha in a secondary riser of the FCC unit for maximum propylene production

To satisfy the increasing propylene demand, reprocessing FCC naphtha in a secondary riser of the FCC unit was investigated. To this aim, a full range FCC naphtha was cracked over a mixture of two kinds of commercial equilibrium FCC catalysts, which contained 95 t.% Y zeolite-based catalyst and 5 wt.% ZSM-5 zeolite-based additive. The effects of operating parameters such as reaction temperature (temperature of the riser outlet), catalyst-to-oil ratio and residence time on FCC naphtha cracking were studied in a continuous pilot plant. This work demonstrates that FCC naphtha requires high operating severities to crack, and approximately 12–19 wt.% FCC naphtha can be transformed into propylene. The conversion and yield of propylene showed a rapid increase with increasing reaction temperature, and the increase of catalyst-to-oil ratio also enhanced FCC naphtha cracking, even at high reaction temperature. However, at high catalyst-to-oil reactions, hydrogen-transfer reactions constrain further increases in light olefin yields. At these high operating severities, shortening residence time is an appropriate way to obtain high yields of propylene combined with (i) lower yields of dry gas and (ii) a lower apparent hydrogen-transfer coefficient.     

A novel conceptional process for residue catalytic cracking and gasoline reformation dual-reactions mutual control

Based on the subsidiary riser FCC (SRFCC) process for gasoline reformation [Y.H. Bai, J.S. Gao, S.C. Li, C.M. Xu, Petrol. Process. Petrochem. (China) 35 (2004) 17–21, J.S. Gao, C.M. Xu, Y. Mao, et al., Petrol. Refin. Eng. (China) 35 (2005) 7–9], a novel conceptional process for residue catalytic cracking and gasoline reformation dual-reactions mutual control (DMC) was proposed and relevant experimental researches were carried out in a Technical Pilot Scale Riser (TPSR) FCC apparatus. The goals of DMC were to improve product quality and increase desirable product yield in residue catalytic cracking as well as in FCC gasoline upgrading. The experiments showed that the decrease of temperature difference between feedstock and regenerated catalysts in DMC by directly leading the cooled regenerated catalysts into riser reactor or feeding gasoline into riser reactor in vapor phase could decrease the amount of dry gas and coke and obtain a better quality of upgraded gasoline. Moreover, the spent catalysts still retaining high level of activity could be recycled to the base of the main riser reactor treating heavy oil and mixed with regenerated catalysts in DMC, it allows residue catalytic cracking to operate at high catalyst-to-oil ratio and the relatively low inlet catalysts temperature. The experimental results also showed that the mixed catalysts could improve the product selectivity in residue catalytic cracking, especially for light oil (gasoline and diesel). In addition, compared with the routine RFCC, the product distribution from the residue catalytic cracking in DMC contains more liquid products, less dry gas, and a better gasoline quality.     

二段多产丙烯试验轻汽油转化不充分的原因

在重油二段提升管催化裂解多产丙烯(TMP)技术中,回炼富含烯烃的轻汽油可进一步增产丙烯。实验室研究表明,回炼占新鲜原料19%的轻汽油,丙烯收率即可增加5%以上,而干气增加不到1%。而在工业试验中回炼占新鲜原料21.88%的轻汽油对丙烯和干气的贡献分别为1.51%和1.37%。其原因在于回炼的轻汽油高速喷入本身造成的催化剂稀相区和重油进料造成的催化剂稀相区,导致以分子形式分散的轻汽油与催化剂不能充分接触、吸附和发生催化转化,并因催化剂流化密度低而不能及时终止未能吸附的轻汽油分子发生热裂化反应,因而丙烯的贡献低而对干气的贡献高。     

流化催化裂化汽油改质和增产低碳烯烃的研究

采用GL型催化剂,在小型固定流化床实验装置上考察了反应温度、剂油比、空速和水油比等操作条件对流化催化裂化(FCC)汽油催化改质汽油的产品分布、低碳烯烃(丁烯、丙烯和乙烯)产率和族组成的影响。实验结果表明,在一定反应条件下,FCC汽油通过催化改质可以降低烯烃含量,提高芳烃含量和辛烷值,在满足新汽油标准的同时提高了低碳烯烃的产率。此外,较高的反应温度、剂油比和水油比以及较低的空速有利于FCC汽油催化改质和增产低碳烯烃。     

反应温度对催化裂化汽油芳构化的研究

以中国石油兰州炼油石化公司催化汽油为原料,采用小型固定流化床为芳构化反应装置,考察了反应温度对芳构化产物收率、转化率、马达法和研究法辛烷值、气体产品组成和液体产品组成的影响规律。实验结果表明,随着反应温度的升高,干气、液化气和焦炭收率呈上升趋势,而汽油和柴油收率呈下降趋势,FCC汽油的转化率都在94%左右,且随反应温度的升高先增大后减小;乙烯、丙烯、丁烯、乙烯和总低碳烯烃收率单调增加,而乙烯、丙烯、丁烯、乙烯和丙烯和总低碳烯烃收率的增加幅度各不相同;异构烷烃和烯烃收率随着反应温度的升高逐渐减少,而芳烃的收率和选择性随着反应温度的升高逐渐增加,正构烷烃和环烷烃的收率随着温度的增加先增加后减少。     

Effect of process conditions on the composition of products in the conventional and deep catalytic cracking of oil fractions

With the purpose of increasing the yield of light C₂-C₄ olefins in comparison with that in conventional catalytic cracking, we experimentally study the effect of temperature and catalyst-to-oil ratio on the distribution of the basic products of oil catalytic cracking on the bizeolite and industrial LUX catalysts. The bizeolite catalyst contains ZSM-5 and ultrastable Y zeolites in equivalent amounts, while the LUX catalyst contains 18 wt % of Y zeolite in the HRE form. As shown by the results of our tests, the yield of C₂-C₄ olefins and gasoline in the deep catalytic cracking of hydrotreated vacuum gasoil on the bizeolite catalyst within a range of catalyst-to-oil ratios of 5–7 and temperatures of 540–560°C reaches 32–36 and nearly 30 wt %, respectively. In cracking on the LUX catalyst under similar conditions, the yield of light olefins and gasoline is 12–16 and 37–45 wt %, respectively. The distribution of target products in the deep catalytic cracking of different hydrocarbon fractions (vacuum gasoil, gas condensate, its fraction distilled from the cut boiling below 216°C, and the hydrocracking heavy residue) on the bizeolite catalyst is studied. It is shown that the fractions of gas condensate and hydroc-racking residue can serve as an additional source of hydrocarbon raw materials in the production of olefins.     

高硅ZSM-5在辛烷值助剂中的应用

研究了不同硅铝比ZSM-5分子筛的催化裂化反应性能,结果表明,高硅铝比ZSM-5分子筛能实现提高汽油辛烷值的同时控制液化气产率增幅较小。考察不同硅铝比的高硅ZSM-5分子筛的反应性能,高硅ZSM-5助剂在ACE装置上的评价结果表明,助剂能使液化气和汽油辛烷值小幅增加,同时也能增加汽油中的芳烃含量。随着ZSM-5分子筛硅铝比的增加,助剂控制液化气的性能逐渐增强,但同时提高汽油辛烷值的性能逐渐减弱。在实际应用中,适宜的ZSM-5分子筛硅铝比应根据目标用户的实际情况和要求灵活选择。     

分子筛催化剂上催化裂化汽油掺混甲醇的改质研究

以实现甲醇制取低碳烯烃转化工艺和FCC汽油降烯烃工艺的有效组合为目的,在固定床微型反应装置上,使用SAPO-34、ZSM-5、DOCO以及分子筛组合催化剂,对FCC汽油掺混甲醇改质进行了研究。主要对反应温度、空速和混炼比等影响因素进行了考察。结果表明,SAPO-34分子筛上甲醇制取低碳烯烃效果较好,高烯烃含量汽油在SAPO-34分子筛上的氢转移和芳构化效果显著,ZSM-5分子筛上的芳构化反应效果和DOCO的异构化反应效果较显著,甲醇转化与汽油转化反应间的相互协同作用,既有利于甲醇转化成低碳烯烃又能提高汽油降烯烃转化深度。适宜的混炼条件:反应温度400℃,m(甲醇):m(汽油)=0.05,空速3h~(-1),组合催化剂上,产物汽油中烯烃含量较FCC粗汽油下降23%以上。     

从ACE评价数据看高液收低焦炭型FCC催化剂的设计

从大量ACE评价数据入手,研究了重油转化率、油浆收率和焦炭之间的相互关系,反应产物柴油、干气与焦炭的关系,热裂化与催化裂化比值、氢转移指数与焦炭的关系。结果表明,在低焦炭产率的同时要获得高的总液收(汽油+柴油+液化气),应结合装置特点合理控制重油转化率,并以碳氢比低的柴油作为催化裂化的主要目标产品,同时降低反应过程中的热裂化反应和氢转移反应。对这些规律进行了深入分析,并提出了具体的高液收低焦炭催化裂化催化剂的设计思路。     

高硫FCC汽油加氢脱硫降烯烃DSRA技术开发

在分析催化裂化汽油硫和烯烃分布不均匀的基础上,对催化裂化汽油进行轻、重组分分馏,开发了活性高和稳定性好的重馏分辛烷值恢复催化剂及FCC汽油加氢脱硫降烯烃DSRA技术。采用DSRA技术对高硫格尔木催化裂化汽油进行轻馏分脱硫醇、重馏分加氢脱硫和辛烷值恢复等改质处理,总脱硫率为94.1%,烯烃降至20%,辛烷值不损失,汽油收率97.83%,化学氢耗0.88%,可生产符合欧Ⅲ规范的清洁汽油。     

Study on reformulation of fluid catalytic cracking gasoline and increasing production of light olefins

The effects of reaction temperature, mass ratio of catalyst to oil, space velocity, and mass ratio of water to oil on the product distribution, the yields of light olefins (light olefins including ethylene, propylene and butylene) and the composition of the fluid catalytic cracking (FCC) gasoline upgraded over the self-made catalyst GL in a confined fluidized bed reactor were investigated. The experimental results showed that FCC gasoline was obviously reformulated under appropriate reaction conditions. The olefins (olefins with C atom number above 4) content of FCC gasoline was markedly reduced, and the aromatics content and octane number were increased. The upgraded gasoline met the new standard of gasoline, and meanwhile, higher yields of light olefins were obtained. Furthermore, higher reaction temperature, higher mass ratio of catalyst to oil, higher mass ratio of water to oil, and lower space velocity were found to be beneficial to FCC gasoline reformulation and light olefins production. __________ Translated from Chemical Reaction Engineering and Technology, 2006, 22(6): 532–538 [译自: 化学反应工程与工艺]