Intensified Transformation of Low-Value Residual Fuel Oil to Light Fuels with TPABr:EG as Deep Eutectic Solvent with Dual Functionality at Moderate Temperatures

Abstract

The performance of two deep eutectic solvents (DESs) was comparatively inspected in upgrading of heavy residual fuel oil (Mazut) as a chemical additive at different processing temperatures and times of 300−350 °C and 105−420 min, respectively. DESs consisted of ethylene glycol possessing hydrogen-donating groups and tetrapropylammonium bromide (TPABr) or choline chloride (ChCl) possessing alkyl tails with different lengths. Characterization of upgraded liquids processed at 325 °C for 210 min showed that TPABr:EG was three times more effective than ChCl:EG in asphaltene conversion and produced a lighter fuel with higher maltene selectivity. Besides the asphaltene reduction (36%), it was more efficient in desulfurization, with a 12.8% reduction, than dry thermal upgrading, with 5.8% asphaltene and 1.9% sulfur reductions, respectively. Moreover, upgraded oil from the TPABr:EG-incorporated scenario revealed high stability toward regression, and viscosity was well preserved after 3 months. Aside from viscosity measurement, asphaltene determination, elemental CHNS, FTIR, and TGA analyses on upgraded oils, isolated asphaltenes from TPABr:EG-incorporated and dry thermal processes were further characterized by FTIR and NMR to pursue the upgrading events. It was realized that TPABr:EG boosted the structural changes in heavy asphaltenic islands by fragmentation and dealkylation of the heteromacromolecular rings. In fact, it intensified both side aliphatic chain shortening and aromatic core shrinkage appreciably compared to the dry thermal process. On the basis of all of the findings elucidating the dual radical generation and hydrogen donation functionality of TPABr:EG, a mechanism is proposed to shed light on the pathway of influence of this eutectic mixture in the intensification of upgrading heavy oil.

Deep Eutectic Solvents and Asphaltenes in Oil Operations: Current Status and Future Prospective toward Sustainable Processes

“…The attack on these clusters was carried out by free hydrogen and free radicals from the gradual thermal decomposition of DES constituents. 75 The DES ChCl:U followed by steam injection tested for heavy oil recovery achieved a significant viscosity reduction, increased API gravity, and substantial reduction in sulfur. This and DESs in oil operations DES ChCl:FAA (1:1) reduced the asphaltenes particle size by 41%, not being as efficient compared to octylphenol.…”

“…These studies addressed the use of DESs in different activities in the upstream oil industry, such as desulfurization, 65,68 EOR, 57,73,74,76 inhibition of asphaltene precipitation, 66,72,73,77 alteration of the wettability of rocks, 53 separation by microemulsion, 69 improvement of heavy residual fuel oil, 75 extraction of phenolic compounds 71 and even cleaning of contaminated areas. 64 These findings corroborate the literature, affirming the versatility and potential applicability of DESs in different technological processes.…”

“…According to the authors, these phenomena began with the attraction of polar-rich asphaltene regions with a partial surface negative charge toward the polar hydroxyl/bromide and cationic ammonium groups of the DES by polar or electrostatic interactions. The attack on these clusters was carried out by free hydrogen and free radicals from the gradual thermal decomposition of DES constituents …”

Priority Separation of Phenols with Deep Eutectic Solvents from an Acetonitrile-Extractable Portion of a Shale Oil: Experimental and Computational

“…Deep eutectic solvents (DESs) with nonvolatility, biodegradability, and nonflammability can be used to extract complex organic mixtures − compared with conventional volatile organic solvents. , DES extraction combined with rapid-purification column chromatography , can also obtain value-added chemicals with high purity (phenol and quinoline) from coal tar and its derivates. In addition, preparing DESs is simpler and more affordable than preparing ionic liquids, but DESs with a high melting point and/or viscosity could encounter neutral oil entrainment in actual oil, difficult phase separation operation, and even raise costs. − So DESs should be screened to isolate Ps from shale oil, coal tar, or fuel oil. − The mechanism of DESs used to extract the complex compositions should be paid attention, especially the interaction difference between DESs and solutes.…”

Optimization study on deep extractive oxidative desulfurization with tetrabutylammonium bromide/polyethylene glycol DES

“…Studies show that hydrogen bonding is the main driving force, and the removal of sulfur atoms is also affected by CH-p, p-p and metal coordination. [32][33][34] The advantages of PEG are good water solubility, low volatility, non-toxicity and varying molar mass. Especially, low molar mass PEGs have been widely employed in industry as environmentally friendly solvents.…”