Subsurface Upgrading of Heavy Oils via Solvent Deasphalting Using Asphaltene Precipitants. Preparative Separations and Mechanism of Asphaltene Precipitation Using Benzoyl Peroxide as Precipitant

Abstract

Subsurface upgrading of heavy oil via solvent deasphalting has been reported previously under laboratory and field conditions. However, these processes require a relatively high solvent-to-oil ratio (SvOR > 1:1 v/v) to induce subsurface asphaltene precipitation, increase oil production, and upgrade crude oil in situ. In our previous work, lab experiments demonstrated that asphaltene precipitants reduce the SvOR (∼30−50 vol %) for subsurface upgrading at initial reservoir conditions and when heat is also applied. In this work, the preparative separations were carried out using benzoyl peroxide (BP), Fe 2 O 3 , and NiO nanoparticles as asphaltene precipitants for Venezuelan and Canadian heavy crude oils. Initial experiments showed that BP is the most effective additive, producing an increase of ∼21 wt % in the asphaltene content for a 2500 mg/kg dosage. Preparative separations at 5:1 vol/wt ratio and 50 °C showed that the order of activity as asphaltene precipitants is BP > NiO > Fe 2 O 3 . In the presence of nickel-and iron-containing precipitants, most of these metals are found in the asphaltenes indicating that the nanoparticles are acting as nucleation sites. Spectroscopic and mechanistic studies using BP as precipitant suggest a free radical mechanism that involves the thermally initiated homolytic cleavage of BP, follow by abstraction of a hydrogen atom from the asphaltenes or maltenes to produce free radical species. In the termination steps, the latter species react with each other to generate new asphaltene species that are not present in the original crude oils.

Bench-Top Thermal and Steam Catalytic Cracking of Athabasca Residual Fractions: Attainable Upgrading Levels Correlated with Fraction Properties

“…A ratio of 13 (mL n C5/ g VR) was, thus, routinely selected for laboratory operation with 5 L flasks. Lower solvent/samples ratios like those described in the open literature (ratios around 5), , were not herein attempted because the filtering procedure required for asphaltenes isolation became very difficult at high viscosity. Routine standardized laboratory-scale deasphalting is carried out at a large solvent/sample ratio (around 30) for facilitating manual operation and improving the test repeatability.…”

Mechanisms of Asphaltene Aggregation: Puzzles and a New Hypothesis

“…There is circumstantial evidence that supports asphaltene molecules exhibiting pancake bonding. For example, Rogel et al found the addition of radical initiator (benzoyl peroxide) led to a ∼21 wt % increase in the precipitated asphaltene content . If pancake bonding promoted by radicals is a key contributor to asphaltene aggregation, we would expect that it would result in a shorter packing distance.…”

“…For example, Rogel et al found the addition of radical initiator (benzoyl peroxide) led to a ∼21 wt % increase in the precipitated asphaltene content. 134 If pancake bonding promoted by radicals is a key contributor to asphaltene aggregation, we would expect that it would result in a shorter packing distance. The packing distance in π−π stacking is bound by a vdW distance of 3.6 Å.…”

Elemental Analysis of Asphaltenes Using Simultaneous Laser-Induced Breakdown Spectroscopy (LIBS)–Laser Ablation Inductively Coupled Plasma Optical Emission Spectrometry (LA-ICP-OES)

“…A mixture of nitric acid (HNO 3 ) (67–70% w/w, 5 mL) and hydrogen peroxide (30% w/w, 2 mL) was used in a UltraWAVE microwave sample preparation system (Milestone Inc., USA). 51 For this procedure, 13 samples and two quality controls can be run simultaneously and the whole process (weighing, loading into MW device, MW program, final dilution with internal standard spiking) would take up to 160 min. The carbon, hydrogen, and nitrogen elemental analysis was carried out by flash combustion with a thermal conductivity sensor using Carlo Erba instrument model NT2500 (Hindley Green, UK).…”