hydrotalcite supported CoMo catalysts. Edwin Oviedo1, Sylvette Brunet2, Carlos Linares1. 1 Department of Chemistry, University of Carabobo, Venezuela.
Hydrodesulfurization of thiophene using calcined Ni / Fe /Al hydrotalcite supported CoMo catalysts Edwin Oviedo1, Sylvette Brunet2, Carlos Linares1 1 Department 2
of Chemistry, University of Carabobo, Venezuela
Institut de Chimie des Millieux et Materiaux de Poitiers (IC2MP), UMR, 7285 CNRS-
Université de Poitiers, France.
ABSTRACT Ni2+, Fe3+, Al3+ tertiary hydrotalcite-type material was synthesized. Then, this synthesized hydrotalcite was calcined and impregnated with Mo (15.wt.% MoO3) and Co (3Mo: Co) and calcined again, to obtain the catalytic precursor: CoMo/NiFeAl. As-synthesized hydrotalcite and catalytic precursors were characterized by different physical-chemical techniques: surface area BET, elemental analysis, temperature programmed desorption of carbon dioxide (CO2-TPD), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). This calcined hydrotalcites supported CoMo was tested in reactions of thiophene hydrodesulfurization (HDS) and cyclohexene hydrogenation (HYD). Results indicated these catalysts presented high number of active site. The CoMo/calcined NiFeAl hydrotalcite exhibited 100% conversion for HDS of thiophene superior to the 43% exhibited by reference catalyst (CoMo/Al2O3). This catalyst presented a high stability.
Keywords:
Hydrotalcite,
Hydrogenation, Iron, basicity.
Thiophene,
Cyclohexene,
Hydrodesulfurization,
Introduction Automotive gasoline is a blend of products from different refinery processes. In general, the Largest contribution comes from the FCC process, which is responsible for 30-40% of the gasoline pool. As it is produced by the breakdown of large molecules originally present in sulfur-rich heavy petroleum fractions, FCC naphtha is responsible for 80-90% of the sulfur in the gasoline pool. Current concerns about environmental conservation are imposing increasingly stricter legislation on the quality of petroleum-derived fuels, all over the world. In the case of motor gasoline, the maximum sulfur specifications are now in the 10-50 ppm range in many countries
Catalytic activity measurements Catalytic activity measurements were carried out in a continuous flow reactor working at the atmospheric pressure and 325 °C with 200 mg of catalytic precursor. Before the test, the catalytic precursors samples were presulfided in situ at 400 °C using a vaporized stream of 10 mL.h-1 of a CS2 (10 vol.%)/n-heptane solution mixed with a H2 stream (100 mL.min-1) at atmospheric pressure for 2 h. The reaction of thiophene hydrodesulfurization was carried out using a thiophene (6 vol.%)/heptane solution, i.e. 33939 ppm S with a feed rate of 2.7x10-4 cm3.s-1 mixed with a H2 stream (0.25cm3.s-1) at 325 °C. For the hydrogenation reaction, cyclohexene was used as model feed composed by a cyclohexene (6 vol.%)/heptane solution, i.e. 7wt.% cyclohexene a feed rate of 2.7x10-4cm3.s-1 mixed with a H2 stream (0.25 cm3.s-1) at 325 °C. Reactions products and unreacted feed were analyzed with a Varian 3800 (AutoSystem XL) gas chromatograph equipped with a flame ionization detector and a capillary column (25m, 0.25µm i.d., CP-Sil 5 CB).
Reaction of thiophene HDS Table 01., Conversion of thiophene and cyclohexene using catalyst CoMo/NiFeAl sulfide Catalyst
Conversion de thiophene (%)
Conversion of cyclohexene (%)
CoMo/Al2O3
43
40
CoMo/NiFeAl(0,54)
100
39
The catalytic precursor (before sulfidation) CoMo/Al2O3 presented a surface area of 204 m2/g, whereas CoMo/NiFeAl presented a value of 42 m2/g. By the other hand, its value (CoMo/NiFeAl) of CO2-TPD was 2,9 µmol/g and for the CoMo/Al2O3 was of 4 µmol/g.
