【作者】 于心玉；

【导师】 何鸣元； 杨建国；

【作者基本信息】 华东师范大学 ， 物理化学， 2007， 博士

【摘要】 在FCC过程中,原料油中的硫约有5～10%wt随积炭在再生器中转化成SOx进入再生烟气。随着FCC装置加工量的不断增加和原油的高硫化、重质化,FCC再生烟气中SOx对环境的污染也日趋严重。与其它控制FCC再生烟气中SOx排放的措施相比,采用硫转移剂技术降低再生烟气中SOx的含量,比较适合现有FCC装置。对硫转移剂的研究要解决以下几个技术问题:(1)提高其硫转移活性和耐磨性能,(2)降低其毒性和生产成本,(3)有效抑制FCC汽油中的硫含量。具体研究结果可总结为以下几个方面:1.MgAlZnFe-HTlc(5%,5%)的氧化吸硫速率随Fe203含量的增加而加快,饱和吸附硫容随镁铝摩尔比的增大而增大,在一定范围内,其性能几乎不受ZnO含量的影响。但是由于MgAlZnFe-HTlc(5%,5%)高温热稳定性能较差,不适合作为硫转移剂的活性组分前驱体。2.MgAlZnFe-HTlc(5%,5%)中引入CeO2以后制备的MgAlZnFeCe-HTlc不仅热稳定性显著提高,而且其氧化吸硫速率明显加快。所以MgAlZnFeCe-HTlc(CeO2=8%)是一种很好的硫转移剂活性组分前驱体。3.随着MgAlZnFeCe-HTlc(CeO2=8%)中Na2O含量增大,其还原脱硫速率明显减慢;与饱和浸渍法相比,共沉淀法引入CeO2制备的MgAlZnFeCe-HTlc(CeO2=8%)氧化吸硫性能较好;随着晶化时间延长和晶化温度升高,MgAlZnFeCe-HTlc(CeO2=8%)的结构更加完整,粒子形貌更加规整;由金属的硝酸盐和盐酸盐合成的MgAlZnFeCe-HTlc(CeO2=8%)物化性能和活性都没有差别。4.通过采用适合碱性活性组分的特殊成型基质和粘结剂,参照FCC催化剂生产工艺条件,在FCC催化剂中试喷雾干燥成型装置(2t/d)上制备了物化性能与裂化剂相兼容的硫转移剂。5.物化性能测试以及氧化吸硫与还原脱硫活性评价的结果表明,利用新方法制备的硫转移剂,无论物化性能,还是氧化吸硫与还原脱硫活性都优于现有专利文献所报道的硫转移剂。ACE、小型固定流化床(藏量为180 g)和中型提升管催化裂化装置(藏量为10 Kg)的评价结果一致表明,当硫转移剂添加量占催化剂藏量的2%wt时,干气中H2S的浓度增加10～20%,再生烟气中SOx脱除率达87%以上,同时NOx的浓度下降了32%,而且没有对平衡剂的活性、产品分布和FCC汽油性质产生不利影响。中型提升管催化裂化装置的硫平衡数据表明,与空白实验相比,添加含有ZnO的硫转移剂,能够有效抑制FCC汽油中的硫含量,但油品中总硫仍有上升的趋势。6.与高岭土、二氧化硅微球和FCC平衡剂载体相比,以拟薄水铝石作为载体和铝源,采用浸渍法负载活性组分,经焙烧原位法制备的MgAlZnFe-S硫转移剂氧化吸硫与还原脱硫活性较高,其饱和吸附硫容随活性组分负载量的增加而升高,经700℃焙烧6 h,可以在拟薄水铝石表面形成很好的尖晶石相,但尖晶石相不是氧化吸硫的唯一活性组分。7.以拟薄水铝石为载体和铝源,采用不同焙烧温度制备了MgAlZnFeCe-Pseud.硫转移剂。结果表明:引入稀土Ce以后,不仅能够阻止拟薄水铝石表面尖晶石相的形成,而且能够有效抑制硫转移剂粒子的烧结,同时硫转移剂的氧化吸硫速率明显增加。随着焙烧温度的升高,尽管拟薄水铝石表面的尖晶石相强度增加,但是当焙烧温度高于700℃时会发生比较严重的烧结现象,造成硫转移剂的比表面积和孔容下降,氧化吸硫活性降低,所以比较好的焙烧条件是700℃6 h。8.研究结果表明,制备的硫转移剂各活性组元在硫转移过程中发挥如下作用:MgO是吸收SOx的唯一活性组分,A1203起保持材料结构的作用;Fe2O3既是氧化SO2的促进剂又是还原MgSO4的促进剂;CeO2是一种很好的氧化SO2的促进剂,但对MgSO4的还原贡献不大;ZnO对氧化吸硫与还原脱硫都没有贡献,但能与A1203共同作用起到抑制FCC汽油中硫含量的作用。9.通过20 L反应釜(1.2～1.5 Kg MgAlZnFeCe-HTlc/釜)中试放大试验合成了MgAlZnFeCe-HTlc(CeO2=8%),无论中试样品的物化性能,还是氧化吸硫与还原脱硫活性都达到了实验室小试样品的水平。本论文创新点主要体现在以下六个方面:一.提出了共沉淀——热处理制备硫转移剂活性组分的方法,该方法适合工业化大规模生产,并且中试放大试验结果验证了其可行性。二.以廉价、无毒的过渡金属铁元素完全取代了价格较贵、毒性很大的金属钒元素。该方法不仅解决了硫转移剂生产过程中钒对操作工人和环境的严重污染问题,而且避免了由其引起的FCC催化剂“钒中毒”。三.通过类水滑石中铁与铈协同作用的研究,发现在保持硫转移剂活性的前提下,引入少量铁,可以大幅度降低硫转移剂中铈的含量,从而降低了硫转移剂的生产成本。四.提出了在硫转移剂活性组分中引入ZnO抑制FCC汽油中硫含量的方法,该方法能解决硫转移剂使用过程中FCC汽油中硫含量上升的问题。五.通过采用适合碱性活性组分的特殊成型基质和粘结剂,利用类似FCC催化剂的喷雾成型技术制备了硫转移剂,解决了硫转移剂耐磨性能差的难题。六.提出了利用拟薄水铝石作为载体和铝源原位法制备硫转移剂的新方法,该方法具有简单易行、制得的硫转移剂性能优异等特点。本论文工作将为硫转移剂的工业生产和应用奠定理论基础,并提供一套较完整的数据。更多还原

【Abstract】 About 5～10% of feed sulfur deposited on FCC catalysts in the coke is converted to SO_X in regenerator and then emitted in flue gas in fluid catalytic cracking （FCC） process. With the increase of throughput of FCC units and sulfur content in crude oil, harmfulness of SO_X from flue gas of FCC units is becoming serious. Compared with other measures for controlling SO_X emission from FCC unit, sulfur-transfer additive technology is more suitable for the present FCC units. Study on sulfur-transfer additive should aim at the following questions （1） to improve the activity and abrasion resistance ability of sulfur-transfer additive, （2） to reduce the toxicity and production costs of sulfur-transfer additive, （3） to control the increase of sulfur in FCC gasoline.The results of this thesis can be concluded as following:1. SO_X adsorption rate of MgAlZnFe-HTlc increased with the increase of Fe₂O₃ content, SO_X saturation capacity became large when the ratio of Mg to Al changed from 2 to 5, ZnO content of HTlc had no significant effect on SO_X adsorption-reduction performance of MgAlZnFe-HTlc. MgAlZnFe-HTlc was not the most efficiently active material precursor of sulfur-transfer additive owing to its thermal instability.2. SO_X adsorption rate of MgAlZnFeCe-HTlc increased rapidly and its thermal stability was also improved obviously when CeO2 was introduced into MgAlZnFe-HTlc（5%, 5%）. So MgAlZnFeCe-HTlc（CeO₂=8%） was an efficient active material precursor of sulfur-transfer additive.3. SO_X-reduction rate decreased quickly when Na₂O content of MgAlZnFeCe-HTlc （CeO₂=8%） increased, SO_X-adsorption profile of MgAlZnFeCe-HTlc（CeO₂=8%） prepared through coprecipitation was higher than that synthyzed with impregnation to introduce CeO₂, the structure and the particles size of MgAlZnFeCe-HTlc（CeO₂=8%） became perfectly and large with the increase of time and temperature of crystallization, MgAlZnFeCe-HTlc（CeO₂=8%） prepared from nitrate and hydrochloric salts had no difference on physicl-chemical properties and SO_X adsorption-reduction activity.4. Sulfur-transfer additive matching with FCC catalyst in physical-chemical properties was prepared using spray drying unit （ 2t/d ） used for FCC catalyst production through the special matrix material and binder suitable for alkaline active material.5. Both physical-chemical properties and SO_X adsorption-redution activity of sulfur-transfer additive were better than that of sulfur-transfer additive reported on literatures. Results of ACE, fixed fluid bed and vertical riser pilot reactor showed that H₂S content in dry gas increased 10～20%, SO_X and NO_X in flue gas decreased 87% and 32% respectively, and the conversion and selectivity of the valuable products did not be modified when sulfur-transfer additive was added to the catalyst inventory in an amount of 2%（wt） compared with that without it. Sulfur equilibrium data from vertical riser pilot reactor indicated that sulfur of FCC gasoline was controlled when the sulfur-transfer additive containing ZnO was used, but the whole sulfur of product oil still increased.6. MgAlZnFe-S prepared from pseudoboehmite as support and aluminium source in situ through impregnation and calcination exhibited high SO_X adsorption-reduction activity compared with kaolin, SiO₂ and equilibrium FCC catalyst supports, and its SO_X saturation capacity became large with the increase of active material content. Spinal phase could form on the surface of pseudoboehmite after calcination at 700 ℃ for 6 h, however, which is not the only active material for SO_X adsorption.7. MgAlZnFeCe-Pseud. was prepared under different calcination temperature using pseudoboehmite as support and aluminium source. Results indicated that SO_X adsorption rate of MgAlZnFeCe-Pseud. increased rapidly, CeO₂ could restrain spinal phase growing on the surface of pseudoboehmite and MgAlZnFeCe-Pseud. particles sintering. Spinal phase on the surface of pseudoboehmite became intense with calcination temperature increasing, however, surface area and pore volume of MgAlZnFeCe-Pseud. decreased quickly when calcination temperature was over 700 ℃, thus SO_X adsorption profile decreased. The optimal calcination conditions for preparation of MgAlZnFeCe-Pseud. in situ were: 700 ℃ 6 h.8. Results showed that MgO was the only active material for SO_X adsorption, Al₂O₃ contributed to the structure of sulfur-transfer additive, Fe₂O₃ played a dual role as an oxidizing and a reducing promoter, CeO₂ was an efficient promoter for oxidating SO₂ to SO₃, but had no significant contribute to the reduction of MgSO₄, ZnO and Al₂O₃ controlled sulfur content of FCC gasoline in synergic effect, but ZnO exhibited no activity for SO_X oxidation-adsorption.9. Physical-chemical properties and SO_X oxidation-adsorption performance of MgAlZnFeCe-HTlc（CeO₂=8%） prepared in 20 L bath （1.2～1.5 Kg MgAlZnFeCe-HTlc/bath） were as same as that of the sample prepared in 1 L bath.The innovation of this thesis can be concluded as following :1. A method of coprecipitation and heat treatment suitable for production of the active material of sulfur-transfer additive has been brought forward, which was testified to be feasible in pilot test.2. Expensive and toxic vanadium element was completely replaced by cheap and nontoxic iron element, which not only reduced pollution to workers and environments during the produce of sulfur-transfer additive, but also avoided vanadium poisoning of FCC catalyst which could make the structure of zeolite collapsed.3. Cerium content can be reduced after a small amount of iron was introduced into HTlc after the study on the synergic effect between iron and cerium in HTlc, which decreased the producing costs of sulfur-transfer additive.4. A method of adding ZnO into the active material of sulfer-transfer additive to control sulfur content of FCC gasoline was developed, which could control the increase of sulfur of FCC gasoline during the application of sulfer-transfer additive in FCC unit.5. The abrasion resistance ability of sulfur-transfer additive was improved through the spray drying method and the special matrix material and binder suitable for alkaline active material. 6. A novel method for preparation of sulfur-transfer additive in situ through pseudoboehmite as support and aluminium source had been brought forward, which was feasible and the performance of sulfur-transfer additive prepared was very good.This thesis will be the theory base for the production and application of sulfur-transfer additive in industry scale, and will provide complete data at the same time.更多还原