Thermal and structural characterization of bitumen by modulated differential scanning calorimetry
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Thermal and structural characterization of bitumen by modulated differential scanning calorimetry E. S. Okhotnikova1 · Yu. M. Ganeeva1 · I. N. Frolov2 · M. A. Ziganshin3 · A. A. Firsin2 · A. H. Timirgalieva1 · T. N. Yusupova1 Received: 30 August 2019 / Accepted: 30 April 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract This paper presents the results of investigation of model bitumens, prepared by mixing of individual fractions of bitumen (saturates, aromatics, waxes, resins and asphaltenes) in various ratios, using modulated differential scanning calorimetry and dynamic temperature sweep test. It was shown that, depending on the content of various fractions, bitumen has structural phases of different compositions. When there are no saturated hydrocarbons in bitumen, it has an amorphous structure. Low molecular weight saturated hydrocarbons form a weakly ordered phase in the bitumen at low temperatures (− 42 to − 14 °C), and high molecular weight saturated hydrocarbons—an ordered phase in the middle temperature range (− 10 to 70 °C). Asphaltenes form the amorphous phase at high temperatures (70–90 °C). The presence of these phases in bitumen is recorded on the heat flow curves in the form of glass transition effects, effects of cold crystallization and melting. At a high content of the ordered phase of high molecular weight hydrocarbons and the amorphous phase of asphaltenes, a gel structure is formed in the bitumen. Keywords Bitumen · Microstructure · Modulated differential scanning calorimetry
Introduction Oxidative bitumen is a product of oxidation of heavy straight run. From chemical point of view, bitumen is complex mixture of aliphatic, aromatic and naphthenic hydrocarbons. Also it includes some quantities of nonhydrocarbon molecules such as organic acids, bases and metallic or nonmetallic heterocyclic components [1, 2]. Composition of bitumen is generally identified by a limited number of fractions which can be separated according to the affinity in their chemical composition using so-called SARA method. According this * E. S. Okhotnikova [email protected] 1
Laboratory of Chemistry and Geochemistry of Oil, Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center of RAS, Arbuzov Str. 8, Kazan, Russian Federation 420088
2
Department of Chemical Technology of Petroleum and Gas, Kazan National Research Technological University, Karl Marx Str., 68, Kazan, Russian Federation 420015
3
Department of Physical Chemistry, Kazan Federal University, Kremlyovskaya Str., 18, Kazan, Russian Federation 420008
methodology, bitumen consists of asphaltene (As) and maltene which, in turn, is divided into saturates (S), aromatics (A) and resins (R) [3, 4]. Asphaltene is described as flat sheet of condensed aromatic system with 4–10 fused rings and pending aliphatic side chains of various lengths. Resin consists of the same condensed system as asphaltene, but it is limited to 2–4 fused rings. Aromatics are hybrid structures that contain naphthenic–aromatic polycy
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