Generation of adamantanes and diamantanes by thermal cracking of polar components of crude oils of different genotypes

The origin and evolution of adamantanes and diamantanes in petroleum

“…Adamantanes and diamantanes in the pyrolysates of the high molecular-mass saturated fraction and the polar fraction of oils have been considered as previously formed diamondoids that are present in the crude oils (Giruts et al, 2006;Giruts and Gordadze, 2007). Our experimental results show that lower diamondoids in the oil have three different origins: (1) Free diamondoids that probably formed during the generation of the oil; this component in the Tarim oil, which can be determined in the original oil, comprises 359 lg/g of adamantanes and 79.8 lg/g of diamantanes.…”

“…Currently, the formation mechanisms of lower diamondoids are mainly attributed to: (1) Lewis acid-catalyzed rearrangements of polycyclic hydrocarbons (Petrov et al, 1974;Wingert, 1992;Lin and Wilk, 1995); and (2) high-temperature cracking of high molecular-mass fractions (Giruts et al, 2006;Giruts and Gordadze, 2007). Laboratory pyrolysis experiments have demonstrated that lower diamondoids can be generated from immature sedimentary rocks and peats (Wei et al, 2006b(Wei et al, , 2007b, kerogen (Gordadze, 2002), crude oils , and their different group components, such as saturated fractions (Giruts et al, 2006) and polar fractions (resin and asphaltene) (Giruts and Gordadze, 2007), as well as from compounds, such as C 16 , C 19 , C 22 , C 34 , and C 36 n-alkanes (Gordadze and Giruts, 2008) and b-ionone (Berwick et al, 2011); all possible isomers of adamantanes and diamantanes can be simultaneously detected in the pyrolysates of the above-mentioned components.…”

“…Laboratory pyrolysis experiments have demonstrated that lower diamondoids can be generated from immature sedimentary rocks and peats (Wei et al, 2006b(Wei et al, , 2007b, kerogen (Gordadze, 2002), crude oils , and their different group components, such as saturated fractions (Giruts et al, 2006) and polar fractions (resin and asphaltene) (Giruts and Gordadze, 2007), as well as from compounds, such as C 16 , C 19 , C 22 , C 34 , and C 36 n-alkanes (Gordadze and Giruts, 2008) and b-ionone (Berwick et al, 2011); all possible isomers of adamantanes and diamantanes can be simultaneously detected in the pyrolysates of the above-mentioned components. In addition, it has been found that lower diamondoids can be destroyed at temperatures higher than those encountered during generation (Wei et al, 2006a;Fang et al, 2012).…”

Variation in abundance and distribution of diamondoids during oil cracking

“…Diamondoids are produced during the pyrolysis of kerogen and modern sediments, and acidic clay minerals (e.g., aluminosilicates) promote the formation of diamondoids (Wei et al, 2006a,c). In addition, pyrolysis experiments also show that diamondoids can be derived from high molecular mass, saturated and polar fractions of crude oils (Giruts et al, 2006;Giruts and Gordadze, 2007). The characteristic abundance and distribution of diamondoids from the two different origins have not yet been quantitatively investigated.…”

“…The most frequently mentioned mechanism is the Lewis acid catalyzed rearrangement of potential precursors (Fort and Schleyer, 1964;Schneider et al, 1966;Petrov et al, 1974). Several organic components in sediments, kerogen and crude oils probably become precursors of diamondoids under thermal stress and in the presence of suitable catalysts (Wingert, 1992;Wei et al, 2006a,c;Giruts et al, 2006;Giruts and Gordadze, 2007;Gordadze and Giruts, 2008;Berwick et al, 2011). Diamondoids are produced during the pyrolysis of kerogen and modern sediments, and acidic clay minerals (e.g., aluminosilicates) promote the formation of diamondoids (Wei et al, 2006a,c).…”