Process for Separation of Petroleum Acids from Crude Oil

Advances in Refining TechnologyProcess for Separation of Petroleum Acidsfrom Crude OilZhuang Lihong'; LiZhenbo; Tian Yanwen'; Zhai Yuchun'(1 College of Materials & Metallurgy, Northeastern University, Shenyang 110005;2 Liaoning University of Petroleum & Chemical Technology, Fushun 113001)Abstract: A new technique for separation of petroleum acids from crude oil was proposed. The method relatesto processes for treating acidic oils or fractions thereof to reduce or eliminate their acidity by addition ofeffective amounts of crosslinked polymeric amines such as polypropylene amine and anionic exchange resinshaving amino-groups. Petroleum acids contained in the mixture can be extracted by a complex solvent. Theresults indicate that more than 80 % of the petroleum acids are removed and the process does not causeenvironmental pollution because all the solvents are recovered and reused in the test.Key words: crude oil; petroleum acid; naphthenic acid; separation; polypropylene amine1 Introductionclude use of oil soluble reaction products of an alkynedioland a polyalkene polyamine, and treatment of a liquid hydro-Most crude oils contain organic acids such as carboxylic carbon with a dilute aqueous alkaline solution, specifically,acids that contribute to corrosion or fouling of refinery dilute aqueous NaOH or KOH. However the use of aqueousequipment. These organic acids generally fall within the cat-NaOH or KOH solutions that contain higher concentrationsegory of naphthenic and other organic acids. Naphthenic of the base can form emulsion with the oil, which necessi-acid is a generic term used to identify a mixture of organictates the use of only dilute aqueous base solutions[3] foracids that are present in petroleum stocks. These acids can treatment.cause corrosion at temperatures ranging from about 210C to420C. Naphthenic acids are distributed throughout a wide Since naphthenic acids are distributed throughout all cruderange of boiling points in acid containing crude oils and may fractions (many of which are not vaporizable) and since crudebe present either alone or in combination with other oils differ widely in naphthenic acid content, most methodsorganic acidsl!".does not provide an expectation that one would be able tosuccessfully treat a broad spectrum of crude oils with a vari-The analysis of naphthenic acids is of major importance for ety of boiling points or to use bases other than NaOH andhe studies on geochemical correlations, biodegradation KOH4.mechanisms and corrosion problems at refineriesl21. The fateof the acidic compounds throughout the refining process There is a continuing need to develop methods for reducingmust be known in order to develop appropriate source con-the acidity and corrosiveness of whole crude oil and the frac-trol measures and wastewater treatment methods that will tions thereof, particularly residua and other high boilingensure compliance with environmental permit requirements.fractions.Therefore, there is a continuing demand for improved meth-ods for the analysis of acids in petroleum- related samples.The present method provides a measure for decreasing theacidity of crude oils in the presence of an effective amount ofEfforts to minimize naphthenic acid corrosion have included a crosslinked polymeric amine that can extract the acid groupsa number of approaches. Examples of such technologies in- from the oil to produce a treated rride nil having a decreased中国煤化工YHCNMH G37.China Petroleum Processing and Petrochemical TechnologyNo.2, June 2005acid content coupled with a crosslinked polymeric amine withTable 1 Properties of crude oilthe acid groups attached. The selected amines, for instance,ItemSudanese PenglaiLiaohecan be: polypropylene amine and anionic exchange resins API gravity (15.6"C)21.9221.599.49containing amino-groups. The crosslinked polymeric amine Density(20"C), g/cm30.9180.92091.0007with acid molecules attached onto it, which is insoluble in the S content, m%1.67crude, can be separated or otherwise isolated from the crude, TAN, mgKOH/g6.092.2710.46e.g, by filtration or centrifugation, and can be regenerated Pour point, C2532through displacement of the related acids.2 Experimental14601290 942Great care must be taken to avoid all types of contaminationduring the analytical procedure. All solvents were distilled in708the glassware system before use. The vessels were cleaned2930by ultrasonic treatment in a detergent solution followed by4000 3333 2666 2000 1666 1333 1000 666 333rinsing with water and acetone.Wave number,cem'lThe reaction apparatus was a 250 mL flask, equipped withFigure 1 Infrared spectra of petroleum acids incrude oilstirrer and reflux condenser .The properties of test oils are listin Table 1.the acids recovered. Regeneration may be accomplished bydisplacing the acids via treatment with carbon dioxide in a2.1 Separation of petroleum acidssuitable dispersant such as an aromatic hydrocarbon or inthe presence of ammonia. The regenerated crosslinked60 g of crude oil with 100g petroleum ether were put into the polypropylene amine can be recovered and recycled. Andflask. 10 g of chemicals including the crosslinked polypropy- the acidic compounds separated from crude oil can be usedlene amine and anion-exchange resins containing amino-for further characterization by other spectroscopic techniques.groups were added. Then 3 g of water were added and the This procedure is more direct, with fewer steps than the pro-reactor contents were heated to 100C and kept in the flask cedure reported earlier by Seifert and Howellsls.for 10 hours. After cooling, the solid was separated bycntifgtion. Titration of the oils according to ASTMD- 3 Results and Discussion664 gave the total acid number again and examination byinfrared spectroscopy showed that a band intensity was found The concentration of acid in the crude oil is typically ex-at 1708 cm"!.pressed as an acid neutralization number or total acid number(TAN), which is the number of milligrams of KOH required to2.2 Regenerated polypropylene amineneutralize the acidity of one gram of oil. It may be determinedaccording to ASTM D-664. Typically, the decrease in acidAfter reaction with the acidic functional groups in the crude content may be determined by a decrease in the neutraliza-oil, the crosslinked polypropylene amine contained acids at-tion number or in the intensity of the carboxyl band in thetached to it, which is insoluble in the crude, and can be sepa- infrared spectrum at about 1708 cm'.rated or otherwise isolated from the crude, e.g., by filtrationor centrifugation. This is unlike the prior processing method, According to the literature it is well known that crude oilswhich applies the low molecular weight amines that are soluble with TAN of about 0.5 or less generally are considered to bein the crude and cannot be separated from the crude oil. Then non-corrosive in terms of naphthenic acid content, crude oilsthe crosslinked polypropylene amine can be regenerated with with TAN 1.5 and中国煤化工r moderately toYHCNMHG38.Advances in Refining TechnologyTable 2 Analytical results of crude oilI Treated crude oilTAN, mgKOH/g Carboxylic acid removal rate, % Peak intensity of infrared spectrum after separation, %Suda0.6789.08.| Penglai0.3186.33.Liaohe1.5315.5slightly corrosive, crude oils with TAN greater than 1.5 are lieved that polypropylene amine in a dilute water solution is aconsidered corrosive.particularly effective means for the recovery of acids fromcrude oil, especially heavy acidic components from crude oil.In this method the crude oils are commingled with suitable Investigation of acids, in particular the high molecular weightcompounds including polypropylene amine and anion-ex- carboxylic acids extracted from crude oil, poses various ana-change resins containing amino-groups to extract the acid lytical problems, which can be solved by choosing an appro-groups from the oil. Typically, these amines are solid at the priate technique. The procedure described hereby for thestarting reaction temperature. Crosslinking may be carried selective removal of the acids is rapid and can be applied toout as the known methods. Suitable polymeric amines may be any crude oil, even those oils with a low acid contentpurchased commercially or synthesized using the known (<0.1%).procedures.The results demonstrated that the total acid number and bondThe reaction duration depends on the temperature and na- intensity at 1708cm*' in the infrared spectrum of petroleumture of the crude oil and its acid content to be treated, but acid provides a simple and efficient method for identifyingtypically may proceed from less than 3 hours to about 15 issues related to naphthenic acid corrosion in crude oil.hours to produce a product with a reduced acid content.ReferencesSome crude oils contain a sufficient amount of water, but in [1]Dzidic I.. Somerille A.C.. RaiaJ.C. and Hart H.V. Determi-most cases, water addition can facilitate the reaction particu-nation of naphthenic acids in California crudes and refinerylarly if the crosslinked polymeric amine is dry. wastewaters by fluoride ion chemical ionization mass spec-Polypropylene amine is highly reactive to a number of func- trometry [J]. Anal. Chem. 1988, 60, 1318- +323.tional groups such as acids, aldehydes, ketones, and phe- [2] Yin Wei, Lin Renzi and Lin Shuangyun. Geochemical char-nolic hydroxides. Thus, it is reactive to many functional acteristics of crude oils from Zao-V oil measures in Shenjiapugroups found in crude oil molecules. Upon reaction of the Oifeld [I]. Chinese Jourmal of Geochemistry.2003, 22, 381-polypropylene amine with a functional group of an organic 386.material, some surface-active characteristics are imparted to [3] U.S. Pat. No. 4,647,366the original molecule.[4]U.S. Pat. No. 4,199,440[5] Seifert, W .K., Howells, W G. Method for recovery of acidic4 Conclusionscrude oils []. Anal. Chem.1969, 41,54- 56From the above-mentioned laboratory experiments, it is be-中国煤化工MHCNMH G39.