Garcia Barneto, Agustin , CARMONA CARMONA, JOSÉ ALBERTO, Franco Garrido, Maria Jose
Si
Thermochim. Acta
Article
Científica
2.236
0.674
20/03/2016
000374075400001
Monitoring asphaltenes is very important with a view to optimizing visbreaking units in oil refineries. Current analyses based on selective dissolution in different solvents are slow, so new, more expeditious methods for measuring asphaltenes are required to facilitate fuel-oil production. In this work, we studied the thermal degradation of asphaltenes as the potential basis for a thermogravimetric method for their monitoring in visbreaking streams. The thermal degradation of asphaltenes occurs largely from 400 to 500 degrees C; the process is quite smooth in an inert environment but involves several fast mass loss events in the air. Kinetic parameters for characterizing the process were determined by using two model-free methods and the modified Prout-Tompkins kinetic equation to examine asphaltene thermolysis. Both types of methods showed the activation energy to increase during pyrolysis but to remain almost constant during cracking in the presence of oxygen or even diminish during char oxidation. Deconvoluting the thermogravimetric profiles revealed that asphaltene thermolysis in the air cannot be accurately described in terms of an nth order kinetic model because it involves some acceleratory phases. Also, thermogravimetric analyses of visbreaking streams revealed that char production in them is proportional to their asphaltene content. This relationship enables the thermogravimetric measurement of asphaltenes. (C) 2016 Elsevier B.V. All rights reserved.
Asphaltenes; Visbreaking; Thermogravimetry; Autocatalysis