Separation and Characterization of Paraffins and Naphthenes from FCC Feedstocks

Abstract

A separation technique was developed for the characterization and identification of the nonaromatic fraction of a light and a heavy FCC feedstock (gas−oil). The separation of the paraffins was based upon the selective reaction of n-paraffins with urea and branched paraffins with thiourea. One more method based on the molecular sieves adsorption was also applied for n-paraffin separation, but the urea method was found to be more satisfactory. The total recovery of the method was about 70%. All the fractions were characterized using a system of GC/MS under the specific conditions presented in this work. The hydrocarbons in the n-paraffinic and isoparaffinic fractions were identified satisfactorily, while for the naphthenic fraction this identification was more difficult. A quantitative analysis was attempted of all the paraffinic compounds in the FCC feedstock. Using a standard sample of n-paraffins, the relative wt % concentrations of the n-paraffinic and isoparaffinic compounds were determined. For the cycloparaffins, the method of ASTM D2786 was applied and the concentrations of naphthenes were approximately estimated according to the number of rings in these compounds.

Compound-Specific δ13C of n-Alkanes: Clean-Up Methods Appraisal and Application to Recent Sediments of a Highly Contaminated Bay

“…Initially, the tests followed the procedure suggested by Canuel (personal communication), 58 in which the crystal formation is carried out at low temperature to recover the low molecular weight (LMW) n-alkanes. 34 It was observed that all the compounds, especially the LMW n-alkanes, appeared in the non-adducted fraction, which means they were not completely adducted by the crystals. To verify if the -4 °C cooling was responsible for this low efficiency in in experiments A, B and D; < 60% for all compounds in experiments D and E; < 61% for all compounds in experiments C and G. Experiment F showed recovery > 80% from n-C 22 to n-C 40 .…”

“…The tested methods were 5A molecular sieves 31,32 and urea adduction [33][34][35][36] to remove cyclic and branched compounds; and silica impregnated with AgNO 3 column for n-alkenes removal. 37 To evaluate quantitatively the possible losses that could occur from the various steps of each procedure, several experiments were conducted with a standard mixture containing the n-alkanes C 12 -C 40 and the isoprenoids pristane (Pr) and phytane (Ph) (AccuStandard, 500 µg mL −1 ).…”

“…The average chain length (ACL) of the n-alkanes is a proxy calculated using the concentration of the compounds from n-C 14 to n-C 34 and is based on the fact that terrestrial sources produce longer chains, which allows its use in characterizing the contribution of allochthonous organic matter. 5,74 The average value of the ACL was 28.3 ± 1.3 and represents predominance of longer chain alkanes for most stations, which may be a result of the degradation of the lighter compounds and a preferred conservation of the heaviest.…”

Production of low aromatics and low sulfur diesel in a hydrodesulfurization (HDS) pilot plant unit

“…The solvents are completely removed by evaporation and the residues are weighed and calculated as the non-aromatics and aromatics fractions of the sample. Full details for this method are given in the literature (Lappas et al, 1997a, Lappas et al, 1997b.…”

Establishment and characterization of turbine oil-degrading bacterial consortia

“…The cyclic alkanes were fractionated from the TuO by the method of Lappas et al (1997) with slight modifications. Briefly, 50 ml of methanol and 30 g of urea were added to 10 g of TuO, and shaken at 160 rpm, for 30 min at 55 ºC, for 1.5 h at room temperature, and 8 for 30 min at 10 ºC.…”