WIT Press

The Study Of Asphaltene Precipitation In Dilute Solution By Calorimetry


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A. Miadonye, L. Evans & T. M. McKenna


Hydrocarbon solvents are often used in the transport of heavy petroleum. Because of the weak dispersion forces formed, it requires less energy for the molecules to change phases and to precipitate asphaltenes out of the solution, leading to problems in the pipeline transportation. In this study, the calorimetric method was used to study the energy change for various mixtures of non-polar solvents with heavy petroleum, and with heavy petroleum which contained a non-polar additive. The amount of asphaltene precipitation was measured for various petroleum-toluene solutions mixed with either hexane or naphtha. It was observed that the lower the concentration of toluene in petroleum, the greater the amount of precipitate. Comparing the enthalpy of mixing with the weight percent of asphaltene precipitation showed that the lower the weight percent asphaltene, the lower the enthalpy of mixing in hexane and naphtha. The presence of toluene lowers the enthalpy of mixing and reduced the precipitation of asphaltenes. Keywords: dispersion forces, asphaltene precipitation, enthalpy of mixing, hydrocarbon solvents, calorimetry, heavy petroleum, bitumen. 1 Introduction The widely acceptable method for reducing heavy oil viscosity, particularly for enhanced recovery, pipeline transportation and refinement is the addition of liquid hydrocarbon condensates, which frequently leads to complex phase transformations, and precipitation of asphaltenes in the resulting solution [1-3]. Asphaltenes are well known for their contribution to problems occurring in petroleum processing. Transportation and drilling processes are affected by the deposition of asphaltenes as they flocculate from petroleum and aggregate in areas such as reservoirs, storage vessels, pipelines and valves. Extensive


dispersion forces, asphaltene precipitation, enthalpy of mixing,hydrocarbon solvents, calorimetry, heavy petroleum, bitumen.