Estudo do efeito da temperatura na precipitação de asfaltenos através de uma análise direta e indireta

Abstract

Asphaltenes are the heaviest and most polar compounds in crude oil, formally characterized by their solubility in aromatic solvents such as toluene and insolubility in light alkanes such as nheptane. Variations in pressure, temperature and composition during the production, transportation and refining phases of the crudes can induce the destabilization, aggregation and precipitation of asphaltenes, leading to fouling and flow blocking in pipelines and wellbore pores that generates great loss to petroleum industry. The present work aims to investigate the effect of temperature at asphaltene precipitation using n-heptane as the precipitant alkane. Three different Brazilian crude oils, here named BR1, BR2, and BR3, were studied at temperatures of 5 ºC, 25 ºC, and 50 ºC, using two different asphaltene yield and precipitation onset analysis, defined as direct and indirect methods. It was found that when temperature rises, there are a decrease on the asphaltenes precipitation yield, together with a slight increase on the precipitation onset, what could be related to the increase of the asphaltene solubility. The indirect method analysis showed that new fractions of heavy compounds aggregate and precipitate at a second precipitation stage under a n-heptane excess, suggesting the formation of new asphaltenes absent in the initial characterization of the crude oils.