Understanding the Chemistry of H₂ Production for 1-Propanol Reforming: Pathway and Support Modification Effects

Abstract

The liquid-phase reforming of 1-propanol over a platinumbased catalyst on a number of supports was investigated. Propanol is being used as a surrogate for biomass-derived glycerol as a source of hydrogen in the conversion of cellulose to transportation fuels. The test conditions were high temperature (230−260 °C) and pressure (69 bar) in the presence of liquid water. Under these conditions, Pt over alumina coated (via atomic layer deposition) with a layer of approximately 1 nm of Al 2 O 3 , TiO 2 , or Ce 2 O 3 (Pt−Al, Pt−Ti, Pt−Ce) is active for the reforming of 1-propanol. The Pt−Ti catalyst had the highest 1-propanol conversion rate per gram of catalyst followed by the Pt−Al and Pt−Ce catalysts, which had similar rates of reaction. Selectivity for each catalyst was primarily to ethane and CO 2 , with the ratio between the two products being close to unity regardless of temperature. The hydrogen yield was constantly higher than twice the ethane yield, indicating that H 2 formation occurs before ethane is formed. Decarbonylation of propanal did not appear to contribute significantly to the formation of ethane. The propionic acid, which can produce ethane and CO 2 through decarboxylation, is believed to form from the disproportionation of propanal. In contrast to the Canizzarro reaction, this reaction appears to be catalyzed by the supported Pt and not the support or in solution (through base catalysis). Our analyses also showed that well dispersed Pt sinters under the high temperature and high partial pressure of water in the reactor, and under reaction conditions that the surface of the Pt has high concentrations of CO (43% of the coverage of CO at room temperature) and water (96% of the coverage of water at 230 °C and 34 bar).

Reduced Vanadium and Molybdenum Oxides Catalyze the Equivalent Formation of Ethane and Acetaldehyde from Ethanol

“…Lobo et al. reported the formation of propane and propionaldehyde in the same quantity with H 2 as the main product in the reaction of 1‐propanol over Pt‐supported catalysts (Pt/Al 2 O 3 , Pt/Ce 2 O 3 , Pt/TiO 2 ) 8. They proposed the mechanism for the formation of propane from 1‐propanol to be through the hydrogenation of 1‐propanol.…”

Carboxylic acid formation by hydroxyl insertion into acyl moieties on late transition metals

“…This is consistent with the experimental findings regarding minor build-ups of propanoic acid while reforming 1-propanol on Pt catalysts. 19,23 In the same spirit, one may also recall that Nozawa et al witnessed the formation of large quantities of acetic acid while reforming ethanol with Pt and Ir catalysts. 27 Experiments showed Pd to be a catalyst for converting alcohols into acids via OH insertion.…”

“…23 A DFT study on methanol steam reforming on PdZn(111) also showed that inserting OH into formaldehyde is much easier than cleaving the C-H bond of formaldehyde, thus supporting DCX as the main pathway in this similar chemistry. 26 The observation of carboxylic acids as products from reactions of alcohols can also be a revealing sign of contributions from the DCX pathway.…”

“…It is difficult to determine experimentally how large a role DCX plays in the APR of alcohols on Pt, as the water gas shift reaction (WGS) easily catalyzes the interconversion of CO into CO 2 under the reaction conditions. 23 DFT results 20,21 indicate Pt(211) steps. Heyden and coworkers used microkinetic models to study the reforming of propanoic acid itself on Pd(111); they also concluded that DCX and DCN are highly competitive and found that the major pathway depends on the choice of the solvent.…”

Scalable Production of Nanostructured Particles using Atomic Layer Deposition

“…The importance of Pt as a catalytic material has driven efforts for deposition on strontium titanate, titania, zirconia and alumina high-surface-area supports in the temperature window of 150-300°C (Christensen et al, 2009;Enterkin et al, 2011;Lobo et al, 2012;Setthapun et al, 2010;Xie et al, 2012). Moreover, the technique has also been used for the doping of Co-based Fischer-Tropsch catalysts with small amounts of Pt (0.1 wt.%) that acts as a promoter (Cronauer et al, 2011).…”