Analysis of the isothermal structure development in waxy crude oils under quiescent conditions

abstract

lsothermal crystallization and structure development was studied for three different waxy crude oils. The transformation from sol to gel was followed by small-amplitude dynamic rheometry, which closely tracks the development of the three-dimensional network as the initially formed crystallites grow, aggregate, and interact with each other. The kinetics of the crystallization-induced gelation was analyzed with the phenomenological Avrami model. The analysis was performed for a temperature range of about 15 K and was limited to the early stages of transformation. Both the Avrami exponent n and the rate constant k are dependent on the crystallization temperature, meaning that the nucleation and crystal growth mechanisms and rates are dependent on the degree of supercooling. Higher Avrami constants and lower Avrami coefficients (higher rate of crystal growth) were observed under higher supercooling conditions. The results discussed allowed the predominant mechanisms for nucleation and crystal growth, occurring as a function of temperature (i.e., supercooling degree) and waxy crude oil composition, to be defined.

keywords

CRYSTALLIZATION KINETICS; PHYSICAL GELATION; POLYPROPYLENE CRYSTALLIZATION; DYNAMIC MODULI; BEHAVIOR; BLENDS; COPOLYMERS; DEPOSITION; MORPHOLOGY; MECHANISM

subject category

Energy & Fuels; Engineering

authors

Lopes-Da-Silva, JA; Coutinho, JAP

our authors

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