Metallic monoliths of AISI 304 stainless steel, aluminum, FeCrAlloy® and brass, coated by Mo and W oxides for thiophene hydrodesulfurization

Abstract

Metal sheets of AISI 304 stainless steel (SS), aluminum (Al), FeCrAlloy® (FA) and brass (B) were employed in the manufacture of metallic monoliths to provide a support for catalysts based on Mo and W oxides. These materials were characterized by XRD, N2 physisorption (BET), adherence test and SEM-EDS. The catalytic performance of the uncoated and coated metallic monoliths was studied using thiophene hydrodesulfuration (HDS) at 400°C and P=1atm as model reaction. With the purpose of generating a high rugosity interface appropriate for anchoring the catalytic slurry, thermal treatments were applied under a stream of synthetic air to the sheet of SS, FA and B, while an anodizing process (chemical treatment) was used for Al. The XRD patterns showed oxidic phases of Cr3O8, Al2O3 type boehmite, α-Al2O3 and θ-Al2O3 and ZnO type wurtzite formed on the surfaces after thermal or anodizing treatments, as well as MoO3 or WO3 phases when coated. SEM of the SS, Al, FA and B sheets treated and coated with Mo or W allowed visualization of the homogeneously rough surface formed by whiskers for SS, FA and B, and the pores on the surface of Al. Incorporation of Mo and W in the structure is evidenced from the EDS analyses, detecting contents of 7–10wt% of these metals. The textural analysis by BET showed values between 5 and 16m2/g, while the adherence test reported mass loss below 5% where metal monoliths showed that the slurry of Mo has more grip than the slurry of W. Finally, the evaluations of the catalytic systems showed that the monoliths of Mo-FeCrAlloy® and Mo-brass were the most active in HDS with activities above 0.27mmol-C4H4S/g×min, showing that the monoliths coated with slurry of Mo presented higher catalytic activity than those coated with slurry of W.