Fluid catalytic cracking technology: current status and recent discoveries on catalyst contamination

The fluid catalytic cracking (FCC) technology is one of the pillars of the modern petroleum industry which converts the crude oil fractions into many commodity fuels and platform chemicals, such as gasoline. Although the FCC field is quite mature, the research scope is still enormous due to changing FCC feedstock, gradual shifts in market demands and evolved unit operations. In this review, we have described the current status of FCC technology, such as variation in the present day feedstocks and catalysts, and particularly, great attention is paid to the effects of various contaminants of the FCC catalysts of which the latter part has not been sufficiently documented and analyzed in the literature yet. Deposition of various contaminants on cracking catalyst during FCC process, including metals, sulfur, nitrogen and coke originated from feedstocks or generated during FCC reaction constitutes a source of concern to the petroleum refiners from both economic and technological perspectives. It causes not only undesirable effects on the catalysts themselves, but also reduction in catalytic activity and changes in product distribution of the FCC reactions, translating into economic losses. The metal contaminants (vanadium (V), nickel (Ni), iron (Fe) and sodium (Na)) have the most adverse effects that can seriously influence the catalyst structure and performance. Although nitrogen and sulfur are considered less harmful compared to the metal contaminants, it is shown that pore blockage by the coking effect of sulfur and acid sites neutralization by nitrogen are serious problems too. Most recent studies on the deactivation of FCC catalysts at single particle level have provided an in-depth understanding of the deactivation mechanisms. This work will provide the readers with a comprehensive understanding of the current status, related problems and most recent progress made in the FCC technology, and also will deepen insights into the catalyst deactivation mechanisms caused by contaminants and the possible technical approaches to controlling catalyst deactivation problems.     

Characterization of tributyrin hydrolysis by immobilized lipase on woolen cloth using conventional batch and novel spinning cloth disc reactors

Optimal loading and operating conditions for a new, superior immobilization of amano lipase from Pseudomonas fluorescens on woolen cloth were determined. The optimal enzyme loading was 46.8 mg g dry cloth⁻¹ with activity of 200 U. A batch reactor was used to characterize process conditions important to industrial application of the wool immobilized lipase. The optimal pH for immobilized lipase in tributyrin hydrolysis was 7, slightly lower than that of free lipase (pH 8). The optimal temperature for both free and immobilized lipase was 45 °C. The immobilized lipase was more stable to reuse than some other lipase immobilizations, maintaining 85% of its activity after 6 long term runs and 75.8% of the original activity after storage of 40 weeks at 4 °C. The thermal stability of lipase was improved by 2.4 times after immobilization. The thermal deactivation rate of immobilized lipase followed the Arrhenius law with E_d = 199 kJ mol⁻¹. The Michaelis–Menten constant (K_m) of the lipase increased from 1.63 mM to 4.48 mM after immobilization. The immobilized lipase was also successfully applied for tributyrin hydrolysis in a novel enzyme process intensification technology – the spinning cloth disc reactor (SCDR): conversion increased by around 13% under similar conditions compared to a conventional batch stirred tank reactor. The SCDR is therefore key to exploiting the advantages of the wool immobilized lipase developed in this work.     

微波辐射下氯代苯胺基吡咯亚胺类化合物的合成及其晶体结构

将2-乙酰基吡咯作为前驱体与取代位置不同的芳香胺:邻氯苯胺、间氯苯胺、对氯苯胺在微波辐射下反应时发现,当氯原子(钝化基团)处于苯环的间位及对位时,芳香胺与2-乙酰基吡咯可成功发生希夫碱缩合反应得到吡咯亚胺化合物Ⅰa和Ⅰb;而当氯原子处于苯环邻位时,二者不发生反应。Ⅰa和Ⅰb的结构经X射线单晶衍射,1HNMR、IR、MS和元素分析表征证实为预期化合物。X射线单晶衍射测定结果表明,Ⅰa属单斜晶系,空间群C2/C,晶体参数a=2.372 2(15)×10-9m,b=5.720(4)×10-10m,c=1.686 8(11)×10-9m,β=98.404(10)°,V=2.264(3)×10-27m3,Z=8,D c=1.283 g/cm3,R1=0.041 9,ωR2=0.119 5。Ⅰb属单斜晶系,空间群P21/C,晶胞参数a=1.332 3(3)×10-9m,b=9.802(2)×10-10m,c=9.107(2)×10-10m,β=109.212(4)°,V=1.123 1(4)×10-27m3,Z=4,D c=1.293 g/cm3,R1=0.047 2,ωR2=0.118 9。对芳香胺上钝化基团的位置对希夫碱缩合反应的影响也进行了初步探讨。     

Study of operating variables in the transformation of aqueous ethanol into hydrocarbons on an HZSM‐5 zeolite

With the aim of determining the possibilities of directly upgrading the liquid obtained from carbohydrate fermentation, the effect of operating conditions (temperature, space time, water content in the feed) has been studied in the catalytic transformation of aqueous ethanol into hydrocarbons on an HZSM‐5 zeolite in an isothermal fixed bed reactor. Special attention has been paid to the effect of water content on the yield, product distribution and catalyst deactivation. Although deactivation by coke decreases as the water content is increased, this content must be limited at 450 °C and higher temperatures in order to avoid irreversible deactivation of the catalyst by dealumination. © 2002 Society of Chemical Industry     

制备条件对生物炭载铁催化剂催化破络Ni-EDTA性能及活性组分浸出的影响

为加强木质素高值化利用,以木质素和铁盐为原料,采用共热解法制备木质素生物炭载铁催化剂。考察铁源前体类型、铁负载量、升温速率和热解温度等制备条件对催化剂催化破络Ni-乙二胺四乙酸（EDTA）性能和铁活性组分浸出的影响,并结合不同热解温度下催化剂孔隙结构、表面元素及晶体结构等表征分析,系统阐述热解温度对催化剂性能的影响机制。结果表明,铁源前体类型直接决定催化剂表面元素组成、极性及Fe活性组分分布情况,以硝酸铁为铁源前体时催化剂性能最佳。负载铁活性物种有助于增加催化剂表面活性位点数量,升温速率可以改变生物炭孔隙结构,热解温度则决定生物炭碳质结构的形成及对Fe活性组分的固载能力。随着热解温度的升高,Fe活性组分逐渐向催化剂内部迁移,600℃时Fe浸出量始终低于1.0mg/L,催化氧化过程由均相Fenton反应为主向非均相反应转变;与此同时,催化剂表面O、N、S活性位点减少,其共同作用致使催化剂失活和Ni-EDTA破络效果降低。上述结果为以木质素生物炭为催化剂载体设计与制备提供了基础数据。     

活化液助溶剂对再生脱硝催化剂性能的影响

为了考察助溶剂对活化液的催化剂再生性能的影响,将某燃煤电厂失活退役的脱硝催化剂在相同清洗工艺下处理,随后分别浸入以草酸、乙醇胺作为助溶剂配制的活化液中,得到两个再生催化剂。采用XRF、氮气物理吸附法、原位吡啶吸附、NH₃-TPD、Raman、XPS、H₂-TPR以及固定床脱硝反应器等表征手段对新鲜样品、失活样品以及再生样品进行表面理化性质、脱硝性能测试评价。结果显示,脱硝催化剂失活的主要原因是飞灰中的碱金属K、Na造成催化剂的比表面积和孔容下降、表面Lewis酸性位数量减少、V⁵⁺比例下降、活性VO_x减少及氧化还原性能下降。同时发现,两个再生催化剂在等量活性组分钒条件下,脱硝性能却表现出较大差异,乙醇胺助溶活化液再生的样品Ethanol-cat性能恢复至新鲜催化剂的97%以上,而草酸助溶活化液再生的样品Oxalic-cat却几乎无再生效果,这是因为两种活化液中的活性组分钒状态不同,乙醇胺助溶活化液中钒离子可有效恢复失活催化剂的酸性位数量、V⁵⁺比例、活性物种VO_x     

游离静止细胞中腈水合酶的失活动力学

Nitrile hydratase (NHase) is an important industrial enzyme used for acrylamide production from acrylonitrile. The deactivation kinetics of NHases in free resting cells of Rhodococcus sp. was presented based on a bi-steady state assumption. Effects of hydration temperature, product concentration and substrate concentration on NHase deactivation were investigated experimentally and correlated with a first order deactivation kinetics. The results showed that the hydration temperature and product concentration were major factors governing the deactivation of NHases under substrate-feeding conditions. When acrylamide concentration was higher than 250 g•L－1, the deactivation of NHases became serious and the bi-steady state assumption was not applicable. When the hydration temperature was controlled at a relatively higher level such as 28°C, the total deactivation rate constant was about 2.8-fold of that at 20°C.     

Hydrodechlorination of 3-chloropyridine and chlorobenzene in methanol solution over alkali-modified zirconia-supported palladium catalysts

The liquid-phase hydrodechlorination of 3-chloropyridine and chlorobenzene has been studied over alkali-modified zirconia-supported palladium catalysts. The modification of the ZrO₂ with alkali metal carbonates improves the catalytic activity of the final palladium catalyst. Therefore, the larger the ionic radii (Li⁺ < Na⁺ < K⁺), the greater the catalytic activity (TOF) of the palladium catalyst. For 3-chloropyridine, hydrodechlorination proceeds without catalyst deactivation. This is explained as the result of the interaction of reaction products (pyridine and HCl) forming pyridinium chloride, thus avoiding the detrimental effect of HCl on the palladium particles. Catalytic hydrodechlorination of chlorobenzene over Pd catalysts exhibits an initial catalytic activity (TOF) much lower than that of 3-chloropyridine and the Pd catalysts deactivate as the reaction proceeds. Finally, chlorobenzene hydrodehalogenation has also been carried out in the presence of an equimolecular amount of pyridine resulting in a decrease in the initial reaction rate on the one hand, but also in an increase in final conversion on the other.