Research Group of Prof. Dr. Jan Andersson

Analysis of asphaltenic ketones in fossil material

Asphaltenes, defined as the fraction of petroleum that is insoluble in n-pentane or n-heptane but soluble in toluene or benzene, are a very complex mixture of polycyclic aromatic hydrocarbons (PAHs) variably substituted with alkyl groups, heteroatoms (N, S, and O), and metals (Ni and V).

Earlier studies have identified oxygen in carboxylic, phenolic, and ketonic structures. The oxygen in asphaltenes may be present as acidic hydroxyl groups. This was confirmed by the poor interaction of phenol solution with asphaltenes. Asphaltenes contain ester and ether bonds in which alcohols and carboxylic acids are bonded to the core by C-O and also C-C bonds.

Of the limited data available, there are indications that oxygen in asphaltenes can exist as nonhydrogen-bonded phenolic hydroxyl groups. Other information on the presence and nature of oxygen in asphaltenes has been derived from infrared spectroscopic examination of the products after interaction of the asphaltenes with acetic anhydride. This has produced evidence for the presence of ketones and/or quinones as well as indications that a considerable portion of the hydroxyl groups present in asphaltenes may exist as collections of two or more hydroxyl functions on the same aromatic ring, or on adjacent peripheral sites on a condensed ring system.

Via selective derivatization reactions the type of oxygen containing functional group within the asphaltenes can be identified

Analysis of non-thiophenic and thiophenic sulfur in petroleum cuts

Petroleum is the most complex matrix known and besides hydrocarbons also contains heteroatomic compounds. Especially the sulfur content of fossil materials is of a great concern for the petroleum industry. As legal requirements require drastically reduced sulfur contents in processed material, e.g. fuels, hydrodesulfurization is one of the most important processes in refining fossil materials. Because of immense costs and recalcitrant sulfur compounds new desulfurization techniques are highly desirable. To be able to optimize these processes, detailed characterization of the various sulfur compound classes is necessary.

In fossil materials sulfur can be present in several functionalities like aliphatic or aromatic sulfides, disulfides, mercaptans or sulfur containing heterocycles (thiophenic sulfur). All these substance classes show different behavior, e.g. recalcitrance to desulfurization. Therefore a method to distinguish between these different compound classes is needed.

Figure 2: thiophenic and non-thiophenic sulfur compounds

For this purpose different chromatographic separations of non-thiophenic and thiophenic sulfur in the liquid phase are performed on novel supporting materials. Ligand exchange chromatography was used as a starting point for the development of the stationary phases. To study the behavior of individual functional groups, we first separate model mixtures by normal phase chromatography followed by several petroleum cuts (up to 550 °C) from a diverse range of oil fields and of varying sulfur concentrations. The separated fractions are analyzed by ultrahigh resolution mass spectrometry.

Involved group members: Isabelle Möller