Interaction of Clay Additives with Mesophase Formed during Thermal Treatment of Solid-Free Athabasca Bitumen Fraction

Abstract

The coking propensity (mesophase appearance time and size) of a fraction of mineral-matterfree Athabasca bitumen vacuum bottoms was investigated using hot-stage (high-temperature and high-pressure) microscopy. The following variables were studied: (1) gas atmosphere (hydrogen and nitrogen); (2) different clay minerals and concentrations (kaolinite at 2 wt % and 5 wt %, illite at 5 wt %, and montmorillonite at 5 wt %). The results of repeated experiments indicated that the mesophase induction period was relatively insensitive to the gas atmosphere. However, the size of the mesophase measured over the same time period was larger and the growth was uninhibited under hydrogen compared with nitrogen. It was also observed that the use of different clays at different concentrations did not significantly affect the mesophase induction period. Kaolinite, at the same concentration, had a significant effect in reducing the size of the mesophase compared with illite and montmorillonite. The effect was more pronounced at higher concentrations of kaolinite. The formation of a small-size mesophase in the case of kaolinite can be explained in terms of the increasing apparent viscosity of the isotropic matrix. The possible mechanism of the clay-mesophase interaction is envisaged as follows: Clays stabilize the layer structure of mesophase, thus inhibiting the shear that is the characteristic form of mesophase deformation. The presence of kaolinite clay prevents the molecules in the pitch matrix from acting as lubricants and restricts the coalescence of the mesophase. Differences in the physical properties of the clays (shape, size, surface charge, and hydrophilicity) may explain the differences in the observed interactions between these clays and the mesophase. The present findings may have significant implications in delayed coking operations and in the prevention of foulant adhesion to the internal wall of furnaces and superheaters.

Phase Separation and Colloidal Stability Change of Karamay Residue Oil during Thermal Reaction

“…Wiehe , postulated that phase separation was an important step of the coking process. Any disturbing affecting asphaltene aggregation or phase separation may restrain the coke formation, such as the addition of fine solid particle to absorb or disperse asphaltenes and coke precursors. − …”

Liquid-Phase Behavior during the Cracking of Asphaltenes

“…Several studies have indicated the importance of fine solids in the liquid−liquid behavior of carbonaceous systems. For example, the addition of fine solids was found to interfere with the coalescence of mesophase in coal tar , and bitumen fractions . Tanabe and Gray suggested that fine solids might prevent coalescence of toluene-insoluble coke material at the early stages of reaction, as observed in mesophase formation at longer reaction times, thereby altering the coking kinetics.…”

“…For example, the addition of fine solids was found to interfere with the coalescence of mesophase in coal tar 7,8 and bitumen fractions. 9 Tanabe and Gray 10 suggested that fine solids might prevent coalescence of tolueneinsoluble coke material at the early stages of reaction, as observed in mesophase formation at longer reaction times, thereby altering the coking kinetics. They showed that fine solids inhibited the formation of tolueneinsoluble coke from Athabasca vacuum residue during reaction in a batch reactor at 430 °C.…”

Evaluation of Oil Sludge Ash as a Solid Heat Carrier in the Pyrolysis Process of Oil Sludge for Oil Production

“…The formation of coke is generally attributed to a condensation reaction that follows the cracking of the volatile fragment of the heavy fraction of the feedstock. − The conversion of the condensation reaction, which reflects the coke-forming tendency of the reaction process, is determined as follows: conversion (%) = (heavy gas oil and vacuum residue (343 °C) of oil product (wt%) + coke yield (wt%))/(heavy gas oil and vacuum residue (343 °C) of extracted oil (wt%)) × 100%.…”