Red-oils in ethylene plants: formation mechanisms, structure and emulsifying properties

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• 作者：Fabrice Cuoq ; Jérôme Vachon ; Jan Jordens…
• 关键词：Caustic tower ; Red ; oil ; Quench water ; Gasoline ; TX ; cut ; Aldol condensation ; Fouling ; Emulsifier ; UPLC ; Q ; TOF
• 刊名：Applied Petrochemical Research
• 出版年：2016
• 出版时间：December 2016
• 年：2016
• 卷：6
• 期：4
• 页码：397-402
• 全文大小：1531KB
• 刊物主题：Catalysis; Industrial Chemistry/Chemical Engineering; Nanochemistry; Energy Technology; Nanotechnology and Microengineering;
• 出版者：Springer Berlin Heidelberg
• ISSN：2190-5533
• 卷排序：6

文摘

In most ethylene plants, the caustic sections suffer from red-oils formation which results from the polyaldol condensation of some oxygenate species in basic media. These red-oils lead to solid material deposition which is generically referred to as fouling and which can cause severe energy losses or operational issues. This specific red-oil fouling can be successfully mitigated by regularly washing the caustic scrubber with a hydrocarbon washing stream which acts as a solvent. However, such washing streams can be further rerouted to the quench water system, increasing the risk of emulsion formation due to its amphiphilic components, i.e., red-oils, compromising the safe operation of the whole plant. The complexity of red-oil structures renders its analysis and characterization challenging. Consequently, there has been no study showing the effect of the type of hydrocarbon wash on the red-oils structure and its potential emulsifying properties. This study describes an in-house developed analytical technique based on UPLC-High resolution QTOF which allows characterizing hydrocarbon streams with complex mixtures of oxygenated species. This method has been successfully applied to monitor red-oil structures during a plant trial where Pyrolysis Gasoline and Toluene-Xylene hydrocarbon washes were successively applied. The data revealed that reactive compounds from the Pyrolysis Gasoline react with the polyaldol species, likely through a Diels–Alder mechanism, thus increasing the diene adduct concentration in the red-oil. It was further found that toluene-xylene washes hindered the emulsifying properties of the red-oils more effectively than Pyrolysis Gasoline washes, in that they could best inhibit the formation of polyaldols adducts.