Comparison of Nanosized Gold-Based and Copper-Based Catalysts for the Low-Temperature Water−Gas Shift Reaction

Abstract

In this paper the catalytic performances for the low-temperature water-gas shift reaction of Au/TiO 2 type A (from World Gold Council), Au/CeO 2 (developed at UPV-CSIC), CuO/Al 2 O 3 (from BASF), and CuO/ZnO/ Al 2 O 3 (from REB Research & Consulting) have been compared. The catalysts were characterized by different techniques such as Raman spectroscopy, BET surface area measurements, temperature-programmed reduction, and high-resolution transmission electron microscopy, which gave additional information on the redox properties and textural and morphological structure of the investigated samples. The performances of these catalysts were evaluated in a wide range of operating conditions in a micro packed-bed reactor. It was observed that the presence of reaction products in the feed (CO 2 and H 2 ), as well as CO and H 2 O feed concentrations, have significant effects on the catalytic performances. With a typical reformate feed the Au/CeO 2 catalyst reveals the highest CO conversion at the lowest temperature investigated (150°C). However, while in the long tests performed the CuO/ZnO/Al 2 O 3 catalyst showed a good stability for the entire range of temperatures tested (150-300°C), the Au/CeO 2 sample clearly showed two distinct behaviors: a progressive deactivation at lower temperatures and a good stability at higher ones. The selection of the best catalytic system is therefore clearly dependent upon the range of temperatures used.

Effect of the preparation method on the catalytic activity and stability of Au/Fe2O3 catalysts in the low-temperature water–gas shift reaction

“…It is also known that oxide-supported noble metals (Pt, Au, etc.) are also able to catalyse the LT-WGS reaction [12][13][14][15][16][17][18], for which better catalysts are required.…”

“…Fe2O3, TiO2, ZnO, Zr2O, CeO2) have been described as supports for gold-based catalysts [14][15][16][17][18][23][24][25]. The increase in activity when gold is added to these oxides in LT-WGS was explained as a synergetic effect between gold and the metal oxide [24][25][26].…”

The water‐gas shift reaction: from conventional catalytic systems to Pd‐based membrane reactors—a review

“…Since then, many authors have been reporting studies over highly dispersed Au on different metal oxide supports, e.g. Al 2 O 3 , [54] ThO 2 , [57] ZrO 2 , [58] CeO 2 , [59 -61] TiO 2 , [50,59,62] mixed oxides of CeO 2 -TiO 2 , [63] Fe 2 O 3 -ZnO and Fe 2 O 3 -ZrO 2 , [64] as well as over supports of a different crystalline state. [64] Among the oxide supports, ceria has been the subject of increased attention due to their better apparent specific interaction with Au.…”

“…Along this line, Mendes et al . [59] studied the influence of Au content on the rate of deactivation decay. In spite of the initial higher activity of the Au (2.5 wt%)/CeO 2 catalyst, after almost 20 h of operation this sample presented a lower performance than another one with a smaller Au content (1.5 wt%).…”

“…Even though it is difficult to establish which of the above-mentioned deactivation mechanisms predominates at particular reaction conditions, it is possible to infer that the observed decay in the rate of CO conversion is strongly dependent on temperature. [59,75] However, it seems reasonable to assume that higher reaction temperatures promote carbonate and/or formate decomposition (decreasing the fouling deactivation); nevertheless, particle sintering effects are more favorable under these conditions.…”