Fathi Owaysi

Hydroprocessing of Heavy Residues: Relation Between Operating Temperature, Asphaltene Conversion and Coke FORMATION

Abstract The nature of changes that take place in asphaltenic and non-asphaltenic fractions of Kuwait vacuum residue with regard to removal of heteroatom such as S, N, V and Ni as well as conversion to lighter products were investigated during hydroprocessing in the temperature range 380–450°C. The average molecular weight and the molecular weight distributions of the asphaltenes in the feed and products were also determined by Gel Permeation Chromatography (GPC). The studies revealed that operating at high temperatures enhanced depolymerization and fragmentation of asphaltenes to low molecular weight materials. Sulphur and vanadium were removed from the asphaltenes relatively easily compared with nitrogen and nickel removal. Asphaltenes conversion and the amount of toluene insoluble sediments in the product increased appreciably at high temperatures (430°C). A portion of asphaltenes was found to resist further cracking even at high temperatures. This portion contained high concentration of nitrogen and nickel. The H/C ratio of the stable asphaltene fragments was relatively low. Coke like sediments were formed in the product at high temperatures (430°c). The stable asphaltene fragments with low H/C ratio could possibly be the origin of sediment or coke formation during the process.

Absorption of Aromatic Compounds From Solutions by Zeolite 13X

Measurements of the equilibrium extent, kinetic and dynamic of adsorption of individual aromatic hydrocarbons: n-dodecylbenzene, naphthalene, and dibenzothiophene from isooctane solutions by molecular sieves 13X were carried out at 343 K and at concentrations 30 kg/m 3 . The separation factor and numbers of adsorbate molecules occupied in the unit cell of the molecular sieves were calculated. The diffusion coefficients were determined using Barrer-Brook equation. The mass transfer zone has been determined using modified Shilov equation and dynamic system of adsorption.

Adsorption of aromatic compounds from solutions on molecular sieve 13X

Measurements of the equilibrium extent of adsorption of individual aromatic hydrocarbons: mono, di, trinuclear aromatic and heterocyclo compounds from iso-octane solutions by molecular sieves 13X were carried out at 303 and 343 K and at concentrations up to 5 wt.% The limiting values of adsorption were essentially determined by using modified Brunauer-Emmett-Teller equation (BET). The coverages and numbers of adsorbate molecules occupied in the unit cell of the molecular sieves were calculated at different temperatures. The isosteric heats of adsorption of aromatic hydrocarbons were also determined using Clausius-Clapeyron equation. It was found that the heats of adsorption of aromatic compounds varied from 4 to 60 kJ mol-1

Adsorption of aromatic mixtures from solutions by molecular sieve 13X

Adsorption isotherms of 3 extracts (concentrated aromatics) have been determined on molecular sieve 13X from solution in iso-octane at 303 and 343 K. The concentration of aromatic compounds before and after adsorption was determined using ultraviolet spectroscopic method of analysis. Values of the adsorption capacity and adsorption coefficient were determined from an equation for pore filling model. The three extract fractions showed a strong affinity for adsorption by molecular sieve. Heats of adsorption of the 3 extract fractions were calculated from adsorption and found to be in the range of 4-20 kJ mol-1.