Résumé
Bimetallic Pd
Pt (Pd/Pt mol ratio = 4/1) catalysts supported on a mesoporous aluminosilicate (Si/Al mol ratio = 20) were prepared by direct liquid crystal templating and using three different means of metals incorporation (direct incorporation in the synthesis gel, impregnation, and ion exchange). The method of incorporation affects the accessibility of the metal surface: with impregnation and ion exchange, intermetallic Pd
Pt particles of uniform size are formed, compared to the particles of segregated metal and alloy of different sizes obtained by direct incorporation. Catalysts are characterized by adsorption of nitrogen and hydrogen, and using X-ray photoelectron and extended X-ray absorption fine structure spectroscopies. The activity of the impregnated PdPt catalyst was investigated in naphthalene hydrogenation at atmospheric pressure and at 6.0 MPa in the temperature range from 260 to 340 °C. Using a real diesel feedstock in an industrial microplant, the activity of the PdPt catalyst is higher than that of a state-of-the-art reference, giving 90.0% of aromatics saturation and an 8 points cetane index increase at 280–300 °C. Nonselective cracking products are C
7–C
10 naphthenes, and, at 325 °C, represent less than 10% product volume. Sulfur poisoning restricts catalyst reactivity mainly to saturation of aromatic molecules, with only limited ring-opening activity, but the final product has a density of 0.840 g cm
−3 and a maximum distillation temperature (T95 max) of 354 °C and contains less than 3% of polyaromatics, in respect of future European legislation on road diesel.