Synthesis of spherical structured catalysts by dip‐coating: Application to n‐butane dehydrogenation

Abstract

This work analyzes the deposition conditions of thin layers of γ‐Al2O3 by dip‐coating on a spherical substrate of α‐Al2O3 spheres. Results showed that under controlled deposition conditions, a structured support of α‐Al2O3 spheres coated by a uniform γ‐Al2O3 layer (thickness ≈ 15 µm) of good adherence can be attained. Optimal preparation conditions for the coating, that involved pretreatment of the substrate, gel formation, deposition conditions, and thermal treatments, were obtained. Pt catalysts supported on this structured material can be used as promising dehydrogenation systems. In this sense, a monometallic structured catalyst showed both good metallic dispersion and catalytic performance in n‐butane dehydrogenation reaction compared to another conventional catalytic system.

Stability studies of PtSn structured catalysts supported on thin layers of MAl2O4 (M: Mg, or Zn) for paraffins dehydrogenation reactions

“…[47,48] Other studies developed structured supports by coating of γ-Al 2 O 3 in compact spheres and studied Pt, PtSn, and PtGe catalysts for the n-butane and n-decane dehydrogenation reactions. [49][50][51] On the other hand, there are works that study the coating with MgAl 2 O 4 on metallic foams, micromonoliths of FeCrAl alloys, and honeycomb cordierite ceramics, used in the synthesis of Ni, Ru-Ni, and Pt catalysts for steam reforming, CO 2 metanation, and hydrogen combustion. [12,[52][53][54] Also, there is vast bibliography on structured catalysts supported on foams and other monoliths coated with different materials such as La-Ni/Al 2 O 3 on cordierite monoliths, CeO 2 -NiO-Al 2 O 3 /Ni-foam, CeO 2 -ZrO 2 -modified NiO-Al 2 O 3 /Ni-foam, and MoVTeNbO supported on SiC foam applied to oxidative dehydrogenation of paraffins.…”

Hydrogenation of citral and carvone on Pt and PtSn supported metallic catalysts. A comparative study on the regioselectivity and chemoselectivity

“…Likewise, 2-propanol conversion tests (to evaluate the acidity of the supports) showed that γ-Al 2 O 3 has a higher acid character than MgAl 2 O 4 . 33,46 Nevertheless, the acidity of alumina is not enough to catalyze cyclization reactions in the citral hydrogenation. 33…”

“…Likewise, 2-propanol conversion tests (to evaluate the acidity of the supports) showed that γ-Al 2 O 3 has a higher acid character than MgAl 2 O 4 . 33,46 Nevertheless, the acidity of alumina is not enough to catalyze cyclization reactions in the citral hydrogenation. 33 The results of the test reactions are presented in Table 2: initial reaction rate (R 0 CH ) and activation energy (E a CH ) values for the cyclohexane dehydrogenation (CHD), the initial reaction rate (R 0 CP ) for the cyclopentane hydrogenolysis (CPH).…”

“…Since a good regioselectivity is difficult to achieve with this type of catalysts, the use of catalysts based on metallic complexes is more common. [42][43][44] Regarding the materials used as supports, it is known that alumina is an acidic support due to Lewis acid sites formed by dehydration during the preparation process, 45,46 and spinels are neutral or slightly acidic supports. 47 Besides, Al 2 O 3 and spinels are materials with industrial applications due to their properties, such as high melting point, high resistance to chemical attack, and good mechanical resistance.…”