Hydrogen Production by Steam Reforming of Ethanol on Rh-Pt Catalysts: Influence of CeO2, ZrO2, and La2O3 as Supports

Abstract

CeO2-, ZrO2-, and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE) for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51) at a gaseous space velocity of 70,600 h −1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2, which showed the best performance in the stability test, also produced the highest H2 yield above 600 °C, followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM, XPS, and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm) and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions, as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.

Response Surface Methodology and Aspen Plus Integration for the Simulation of the Catalytic Steam Reforming of Ethanol

“…Similarly, Kaila et al [34] (Figure 1d), which could explain the higher H 2 yield for this catalyst ( Figure 1b). As discussed in our previous work [32,37], evidence of Rh-Pt alloy formation was found on the RhPt/CeO 2 catalysts. Thus, Rh-Pt alloy formation on RhPt/CeO 2 catalysts promotes different product distributions depending on the Rh-Pt ratio.…”

“…Specifically, a greater amount of CH 4 formation was observed on Rh 0.2 Pt 0.6 /CeO 2 at high temperatures. In our previous work, Rh-Pt-Rh 2 O 3 particles were reported as possible active sites in SRE, which favor the catalyst's high stability [26,32]. However, shortcomings of this catalyst to reform CH 4 at high temperatures were detected.…”

“…However, monometallic catalysts (Rh/CeO 2 and Pt/CeO 2 ) showed lower production of ethylene compared to bimetallic catalysts. It is accepted that Rh favors C-C dissociation [43] and that bimetallic Rh-noble metal on basic supports contributes to the mitigation of carbon deposition [18,32]. In addition, the presence of higher amounts of CO 2 on the bimetallic catalysts could be an indication of ethylene reforming (Equation (10)) [52].…”

“…In our previous work, a bimetallic 0.6 wt % Rh-0.2 wt % Pt over CeO 2 catalyst appeared to have a high activity in SRE and WGSR with a low susceptibility to coke formation [32]. The main drawback of this catalyst is its high cost.…”

Influence of Catalytic Formulation and Operative Conditions on Coke Deposition over CeO2-SiO2 Based Catalysts for Ethanol Reforming

“…In particular, less-oxophilic metals (Pd and Pt) are known to activate α-C-H bonds, while more-oxophilic metals (Co, Ni, Rh, Ru) promote molecule activation via O-H [16]. Despite noble metals catalysts being more active and stable than base metal catalysts in ESR reaction, the high costs hinder their practical applications.…”