Separation from maltene fraction petroleum

Figure 1. Flow diagram for the separation of the sulfide and thiophene classes of compounds from the maltene fraction of petroleum. (Reproduced from Reference 34. Copyright 1989, American Chemical Society.)...

Fractionation by solubility is used to isolate asphaltenes from maltenes, and the standard method (ASTM-3279-97) has been used in this work. Crude petroleum is mixed with 40 volumes of heptane, heated, stirred, and left to cool. The asphaltenes form a precipitate that can be removed by filtration. Normal practice is to clean the asphaltene fraction by Soxhlet in heptane. The proportions of asphaltene in crude petroleums vary widely, from less than 0.1% in the best crudes to over 10% in the heavy crudes. In general, the heavy crudes such as Maya are of most interest. The solubility of petroleum asphaltene in NMP is of interest since the NMP-insoluble material has no fluorescence [61] and was initially assumed to be aliphatic. However, it has UV absorbance and must be aromatic [62]. The separation into NMP soluble and insoluble was achieved for several asphaltenes. A Kuwaiti asphaltene was separated into NMP-soluble and -insoluble fractions [63]. Seven crude oils were fractionated into heptane solubles and asphaltenes for comparison with an asphaltene from a heavy oil [64]. 

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