Distillation Behavior of Various Parent and Chemically Dispersed Crude Oil: Comparison of Yields, Chemical Composition and Fuel Quality of Distillate Fractions

Abstract

Crude oil after preliminary treatments is subjected to refining so as to get marketable products like naphtha, gasoline, kerosene, diesel fuel, lubricating oil feed stock, furnace oil, etc. A large amount of asphalt/bitumen is left over as residue. Owing to its high viscosity, density and contamination by sediments as well as high asphaltene and resin contents, the residue cannot be directly used as a boiler fuel and instead used for non-fuel purposes. The global demand for energy continues and will increase over the next few decades as the world's energy consumption will increase phenomenally in the next few decades. Alternative energy sources like nuclear and renewable energy have attracted much attention in the recent years, however, the main role of these sources, will be to supplant, rather than to substitute the fossil fuels. Therefore, major breakthroughs in the oil industry's core science and engineering are needed so as to meet with the World's growing energy demand for petro-fuels. The high yields of residue/residuum is an ongoing challenge at a refinery and economic & strategic reasons demands the exploitation of residual streams. Accordingly, the selection of proper processes may play a key role so as to cope with the challenge. The objective of the present thesis was to employ atmospheric distillation process using three crude oils dispersed with chemical surfactants in order to get lighter fuel fractions in high yields in comparison with the plain crudes (control). The thesis summarizes the characterization of the crude oils with respect to their key physicochemical properties including density (kg/m3), viscosity (mPa·s), API gravity, total acid number (mg KOH/g), and asphaltene contents (wt %). Chemical dispersants i.e. sodium dodecyl sulfate (SDS); a anionic surfactant, hexa decyltrimethylammonium bromide as cationic surfactant, and Triton-X as neutral surfactant were used. The crude oils investigated included paraffinic (denoted as RCP-I), naphthenic (denoted as RCN-II) xii and aromatic (denoted as RCA-III) Pakistani crudes. Each crude oil was spiked with the varying dispersant –to-oil ratios (5:100, 10:100, 15:100, 20:100, 25:100 and 30:100) and then subjected to atmospheric distillation. The distillation of each surfactantdispersed crude oil was carried out in comparative experiments with the plain crude oil so as to investigate the effect of each dispersant on the yield, chemical composition and fuel properties of the derived distillate fractions (F1, F2 and F3). The Gas Chromatographic-Mass Spectrometric analysis (GC-MS) was carried out in order to ascertain compositional stability of the distillate fractions. The desired fuel properties of the light fractions were also determined as per ASTM standards and compared with the generic gasoline and diesel fuel samples. Looking at the results, we conclude that using chemically dispersed crudes enabled to obtain better yields of the light distillate fractions in comparison with the control without disturbing the key fuel properties. Among the three crudes used, the SDS-dispersed RCA-III, CTAB-dispersed RCN-II andTriton-X-100-dispersed RCN-II crudes were more effective which gave significant increase in the yields of light distillate fractions and reduced the residues without disturbing the fuel quality criteria.