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EEMS2015 organizing committee
Published in Yeping Wang, Jianhua Zhao, Advances in Energy, Environment and Materials Science, 2018
Pristane (2,6,10,14—tetramethyl pentadecane) and phytane (2,6,10,14—tetramethyl hexadecane) come from some special organisms. As a pioneer of pristine and phytane, chlorophyllous phytol widely exists in the nature—it derives from phy- tol side chain, it is relatively stable, its resistance to microbial attack is stronger than n-alkanes, so Pr/Ph ratio is widely used as a palaeoenvi- ronment index. Phytol is reduced under reduc- ing conditions, and converted to phytane after hydrogenation and dehydration. Under oxidizing conditions, phytol is oxidized, decarboxylated and converted to pristine (Volkman et al, 1986). Regarding Pr/Ph ratio at all sections of P7327, it is 3.017 at the top (12 cm), much larger than 1. It means that overlying deposits are in strongly oxidizing sedimentary environment; alkane molecular structure changes a lot, showing that organic matters in sediment core have evolved. As the depth increases, Pr/Ph ratio tends to reduce. In early sections (120121 cm, 182184 cm), Pr/Ph ratio reduces. It means that sediment core is under reducing conditions; phytane has appeared before pristine. As the depth increases, long-chain hydrocarbon converts to short-chain hydrocarbon. At 182184 cm sections, with the input of bacterial hydrocarbon, increase of bur- ied depth and enhancement of bacterial degra- dation, abundance of molecules with low carbon number tends to rise significantly.
Bio-oil production from oleaginous microorganisms using hydrothermal liquefaction: A biorefinery approach
Published in Critical Reviews in Environmental Science and Technology, 2022
Tanushree Paul, Arindam Sinharoy, Divya Baskaran, Kannan Pakshirajan, G. Pugazhenthi, Piet N. L. Lens
In addition, a high protein content in the microbial biomass produces amino acids and carboxylic acids during hydrolysis, the decomposition of amino acids can be done in two ways: through deamination or decarboxylation (Scott et al., 2007). Protein consists of several chains of peptides and can be converted to a nitrogen limited bio-oil (Du et al., 2012). Another category of important compounds of oleaginous microbes is carbohydrates, which show an unusual composition and yield of bio-crude oil (Colin et al., 2011). Carbohydrates may be converted to propionic acid, benzene, and 4-hydroxyphenynethyl alcohol at high temperature (above 350 °C). Moreover, glucose can decompose into ethanol, methanol, lactic acid, acrylic acid and furfural which, however, affect the bio-crude oil yield. Another abundant compound, particularly in phototrophic oleaginous microorganisms, is the pigment chlorophyll which generally decomposes into phytol which is then converted to phytane (Jinkerson et al., 2011).
Geochemical characteristics and sources of Chang 8 crude oil from Xiaoxian area, Southwest margin of the Ordos Basin, China
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
The value of pristine/phytane (Pr/Ph) can reflect the sedimentary environment in which crude oil was formed (Hanson, Zhang, and Moldowan 2000). Chang 8 crude oil with the value of Pr/Ph less than 0.80 formed in the strong reductive depositional environment; Pr/Ph between 0.80 and 3.00 formed in a weak reduction-weak oxidation depositional environment; Pr/Ph greater than 3.00 formed in oxidation sedimentary environment (Gao, Fan, and Gao 2010). The Chang 8 crude oil and basin central Chang 7 source rocks had similar sedimentary environments, with the ration of Pr/Ph between 0.78 and 1.10 (Table 2), suggesting both were formed in the weak reduction to weak oxidation sedimentary environment. The Pr/Ph value of Chang 7 source rocks in the study area, however, was relatively high, ranging from 1.10 to 1.34, and the sedimentary environment was relatively oxidized compared with crude oil. According to the intersection point diagram of Pr/nC17 and Ph/nC18 ratios in Figure 4, the maturity of Chang 7 source rocks in Xiaoxian is significantly lower. The distribution ranges of these two data points of Chang 8 crude oil indicate that the parent material is mixed, formed in the weak oxidization and weak reduction environment. Compared with the source rocks, their values are closer to those of Chang 7 source rock samples in the center of the basin, demonstrating that they are more similar to Chang 8 crude oil in terms of characteristics (Hanson, Zhang, and Moldowan 2000).
Biomarker characteristics and geological significance of middle and upper Permian source rocks in the southeastern Junggar Basin
Published in Petroleum Science and Technology, 2019
Yongqiang Qu, Huifei Tao, Dongzheng Ma, Tao Wu, Junli Qiu
The phytolside chain of chlorophyl produced by photosynthesis of plants or photoautotrophic bacteria become isoprenoid alkanes through diagenesis, and then was dehydrated into phytene in a reducing environment, which is at last hydrogenated to form Ph (phytane). In the case of an oxidizing environment, phytol is oxidized and changed into phytanic acid, and then the hydroxyl is removed to generate Pr (pristane) (Bendoraitis, Brown, and Hepner 1962; Powell and Mckirdy 1973). Therefore, the distribution of Pr and Ph can characterize the sedimentary environment. Generally speaking, Pr/Ph < 0.5 indicates a strong reduction environment; Pr/Ph = 0.5 ∼ 1.0 indicates a reduction environment; Pr/Ph = 1.0 ∼ 2.0 indicates a weak reduction-weak oxidation environment; Pr/Ph > 2.0 indicates a parital-oxidation environment (Haven et al. 1987). Moreover, Pr/Ph is dependent on the thermal evolution degree of rocks. In the early stage of thermal evolution, a position correlation is found between Pr/Ph and maturity degrees. As for rocks in the mature stage (Ro = 0.7 ∼ 11.%), Pr/Ph has a relatively constant value (Boudou, Durand, and Oudin 1984; Wang and Xia 1995; Koopmans et al. 1996). In the case of higher degrees of thermal evolution, it continues to grow. In addition, it is important to point out that archaebacteria and Vitamin E are another important source of Ph and Pr, (Fleck et al. 2002).