Hydroprocessing of Oleic Acid for Production of Jet-Fuel Range Hydrocarbons over Cu and FeCu Catalysts

Abstract

In the present study, a series of monometallic Cu/SiO2-Al2O3 catalysts exhibited immense potential in the hydroprocessing of oleic acid to produce jet-fuel range hydrocarbons. The synergistic effect of Fe on the monometallic Cu/SiO2-Al2O3 catalysts of variable Cu loadings (5–15 wt%) was ascertained by varying Fe contents in the range of 1–5 wt% on the optimized 13% Cu/SiO2-Al2O3 catalyst. At 340 °C and 2.07 MPa H2 pressure, the jet-fuel range hydrocarbons yield and selectivities of 51.8% and 53.8%, respectively, were recorded for the Fe(3)-Cu(13)/SiO2-Al2O3 catalyst. To investigate the influence of acidity of support on the cracking of oleic acid, ZSM-5 (Zeolite Socony Mobil–5) and HZSM-5(Protonated Zeolite Socony Mobil–5)-supported 3% Fe-13% Cu were also evaluated at 300–340 °C and 2.07 MPa H2 pressure. Extensive techniques including N2 sorption analysis, pyridine- Fourier Transform Infrared Spectroscopy (Pyridine-FTIR), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and H2-Temperature Programmed Reduction (H2-TPR) analyses were used to characterize the materials. XPS analysis revealed the existence of Cu1+ phase in the Fe(3)-Cu(13)/SiO2-Al2O3 catalyst, while Cu metal was predominant in both the ZSM-5 and HZSM-5-supported FeCu catalysts. The lowest crystallite size of Fe(3)-Cu(13)/SiO2-Al2O3 was confirmed by XRD, indicating high metal dispersion and corroborated by the weakest metal–support interaction revealed from the TPR profile of this catalyst. CO chemisorption also confirmed high metal dispersion (8.4%) for the Fe(3)-Cu(13)/SiO2-Al2O3 catalyst. The lowest and mildest Brønsted/Lewis acid sites ratio was recorded from the pyridine–FTIR analysis for this catalyst. The highest jet-fuel range hydrocarbons yield of 59.5% and 73.6% selectivity were recorded for the Fe(3)-Cu(13)/SiO2-Al2O3 catalyst evaluated at 300 °C and 2.07 MPa H2 pressure, which can be attributed to its desirable textural properties, high oxophilic iron content, high metal dispersion and mild Brønsted acid sites present in this catalyst.

Hydroprocessing of oleic acid for production of jet fuel range hydrocarbons over Sn(1)‐Fe(3)‐Cu(13)/SiO2‐Al2O3 catalyst: Process parameters optimization, kinetics, and thermodynamic study

“…In order to complement the qualities of copper, metals of high oxophilicity are added to copper. The addition of high oxophilic iron as a promoter can improve the activity and selectivity of Cu‐based catalyst 8,13 . Iron is known for its low price, natural abundance, and rich redox chemistry.…”

“…The author reported high selectivity of liquid paraffins and attributed it to the strength of Fe–O bond in the reduced Fe‐based catalyst evaluated. The surface area and stability of copper catalysts can also be improved by tin 15 . Copper and iron loadings were optimized for oleic acid hydroprocessing for production of jet fuel range hydrocarbons in our previous work 13 .…”

“…The surface area and stability of copper catalysts can also be improved by tin 15 . Copper and iron loadings were optimized for oleic acid hydroprocessing for production of jet fuel range hydrocarbons in our previous work 13 . The role played by catalysts' active sites is complemented using support with optimized Bronsted acid sites in order to achieve a balance between production of hydrocarbons lower than C 8 and those that are higher than C 16 .…”

“…Supports of high surface area are also required for triglycerides feedstock because of its high molecular and kinetic diameters. SiO 2 ‐Al 2 O 3 support has been reported to have these required qualities 13 . It was reported to have moderate Bronsted acid sites and textural properties required for production of aviation turbine fuel range hydrocarbons 13 .…”

“…% Cu supported on silica‐alumina gives the most promising selectivity (77%) of jet fuel range hydrocarbons. The promising results are attributed to the crystallite size of its copper phase, high surface area, and weak metal support interaction 15 . Higher selectivity of jet fuel range hydrocarbons was achieved due to the promotional effects of Sn.…”