(537e) Extractive Isolation of Acetic Acid and Formic Acid from Green Liquor Condensates

                                                                                    Extraction, characterization and quantification of naphthenic acid from crude oils

Fenglou Zou, Simon Andersen, Huang Zeng, Huaping Li, Jose Zacharia

Schlumberger, DBR Technology Center, Edmonton, Canada, T6N 1M9

Carboxylic acids (RCOOH), also known as naphthenic acids in the oil industry, are natural surfactants in crude oils. It is assumed that the functional groups of naphthenic acid affects oil properties and behaviour, and further impacts emulsion stability and reservoir wettability. Carboxylic acids span the entire boiling point range from benzoic acid to asphaltenes, which makes acid separation and quantification challenging. Classical TAN (Total Acid Number) is not representative of the actual content of acids in crude oils because TAN determined using conventional KOH titration includes contributions from other compounds, such as hydrogen sulphide, thiols and alkylphenols. Naphthenates (salts of naphthenic acids) have industrial applications such as synthetic detergent, fuel and lubricating oil additives, wood preservatives and oil drying agents used in painting and wood surface treatment.

The present paper explores various methods applicable to acid determination including different extraction procedures and methods to calculate true acid content. Water extraction and IER (ionic exchange resin) extraction were found to have low repeatability, and contamination by non-acids was high. Acid extraction based on column chromatography using SAX (strong anionic exchange resin) as a stationary phase showed good repeatability and the repeatability was further improved by using instrumental solid phase extraction (SPE) based on commercial SAX stationary phase cartridges (Figure 1). 2D GC-TOFMS (two dimensional gas chromatography-time of flight mass spectrometry) was used for characterization and quantification of species within the detection range of the GC. The difference seen in distribution between IER and water extraction was clearly biased by the lack of solubility of certain acids in water.

Figure 1. Comparison of two individual acid extractions using SPE showing good repeatability for acid extraction.