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.     

Hydrogen related degradation in pipeline steel: A review

To support our increasing energy demand, steel pipelines are deployed in transporting oil and natural gas resources for long distances. However, numerous steel structures experience catastrophic failures due to the evolution of hydrogen from their service environments initiated by corrosion reactions and/or cathodic protection. This process results in deleterious effect on the mechanical strength of these ferrous steel structures and their principal components. The major sources of hydrogen in offshore/subsea pipeline installations are moisture as well as molecular water reduction resulting from cathodic protection. Hydrogen induced cracking comes into effect as a synergy of hydrogen concentration and stress level on susceptible steel materials, leading to severe hydrogen embrittlement (HE) scenarios. This usually manifests in the form of induced-crack episodes, e.g., hydrogen induced cracking (HIC), stress-oriented hydrogen induced cracking (SOHIC) and sulfide stress corrosion cracking (SSCC). In this work, we have outlined sources of hydrogen attack as well as their induced failure mechanisms. Several past and recent studies supporting them have also been highlighted in line with understanding of the effect of hydrogen on pipeline steel failure. Different experimental techniques such as Devanathan–Stachurski method, thermal desorption spectrometry, hydrogen microprint technique, electrochemical impedance spectroscopy and electrochemical noise have proven to be useful in investigating hydrogen damage in pipeline steels. This has also necessitated our coverage of relatively comprehensive assessments of the effect of hydrogen on contemporary high-strength pipeline steel processed by thermomechanical controlled rolling. The effect of HE on cleavage planes and/or grain boundaries has prompted in depth crystallographic texture analysis within this work as a very important parameter influencing the corrosion behavior of pipeline steels. More information regarding microstructure and grain boundary interaction effects have been presented as well as the mechanisms of crack interaction with microstructure. Since hydrogen degradation is accompanied by other corrosion-related causes, this review also addresses key corrosion causes affecting offshore pipeline structures fabricated from steel. We have enlisted and extensively discussed several recent corrosion mitigation trials and performance tests in various media at different thermal and pressure conditions.     

Effect of Microstructure and Texture Evolution on the Electrochemical Corrosion Behavior of Warm-Rolled API 5L X70 Pipeline Steel

Metallurgical and Materials Transactions A - Thermomechanical treatments were used to improve the corrosion resistance of API 5L X70 pipeline steel materials. Successive warm rolling was performed...     

Humic Acid from Livestock Dung: Ecofriendly Corrosion Inhibitor for 3SR Aluminum Alloy in Alkaline Medium

Humic acids (HAs) extracted from cow, goat, and poultry dung were studied. Extraction was performed by treating the source materials with acid hydrolysis using hydrochloric acid (HCl) before alkaline extraction with sodium hydroxide (NaOH). Yields of 3.33, 2.67, and 1.28% dry weight were obtained from cow, goat, and poultry dung respectively. The extracted humic acids were characterized using Fourier transform-infrared (FT-IR) and ultraviolet-visible (UV-vis) spectroscopy techniques. The results obtained were in good agreement with commercial HA (Sigma-Aldrich). The humic acid extracted from cow dung was used to evaluate its corrosion inhibition potential for alkaline-induced corrosion of 3SR aluminum alloy using weight loss and electrochemical (potentiodynamic polarization) techniques at 30°–60°C. Results obtained show that the humic acid functions as an excellent corrosion inhibitor for aluminum alloy in 0.1 M NaOH solution. Corrosion inhibition efficiency increased with increase in humic acid concentration but decreased with rise in temperature. Results from potentiodynamic polarization measurements show that the HA behaved mostly as a mixed-type inhibitor. Adsorption of the humic acid was found to obey the Langmuir adsorption isotherm at all concentrations and temperatures studied. The mechanism of physical adsorption has been proposed based on the trend of inhibition efficiency with temperature. The proposed mechanism was also corroborated by kinetic and thermodynamic parameters obtained.     

Effect of Thermomechanical Processing and Crystallographic Orientation on the Corrosion Behavior of API 5L X70 Pipeline Steel

Metallurgical and Materials Transactions A - This work presents the electrochemical response of X70 pipeline steel substrates thermomechanically processed at different conditions. The WE sample was...     

基于氧传感器信号的用于研究空气/燃料比率变化的统计方法

给出了火花点火式发动机排气氧传感器(EGO)输出信号的实验结果.实验中采用V6、3.8 L、BUICK发动机且每个气缸中安装有一个氧传感器,以研究影响发动机消耗燃料的因素.应用LabView数据采集装置记录单个气缸废气以及主流尾气氧传感器的输出电压信号.对来自6个气缸变量的平均值采用统计的方法进行处理后,并与主流的EGO电压进行比较,确定了产生系统误差的因素.对左右两侧气缸信号平均值的差别进行比较发现,采用此种排气管结构的气缸中空气-燃料混合气平均值存在一些明显差别.根据数据和图表解释了统计的结果.研究表明,V字形排列的发动机两侧的气缸的空气和燃料混合气是不同的;在低速、高负荷和高辛烷燃料的情况下,右侧气缸具有比较稀的混合气;而在某些情况下两侧气缸具有相同的混合气.基于统计估计的方法,提出了一个可以用于估计V字形排列发动机左右两侧气缸中空气-燃料混合气的简单模型.此方法还可以应用于分析进气管和排气管的缺陷.