Surface Structure Dependence of the Dry Dehydrogenation of Alcohols on Cu(111) and Cu(110)

Abstract

The non-oxidative dehydrogenation of alcohols is considered as an important method to produce aldehydes for the chemical industry and hydrogen gas. However, current industrial processes are oxidative, meaning that the aldehydes are formed along with water, which, in addition to being less energy efficient, poses separation problems. Herein the production of aldehydes from methanol and ethanol on clean and dry Cu(111) and Cu(110) surfaces was investigated in order to understand the catalytic anhydrous dehydrogenation of alcohols. Both ethanol and methanol preferentially react under ultrahigh vacuum conditions at surface defects to yield acetaldehyde and formaldehyde, respectively, in the absence of surface oxygen and water. The amount of alkoxide reaction intermediates measured by scanning tunneling microscopy, and aldehyde and hydrogen products detected by temperature programmed reaction, are increased by inducing more defects in the Cu substrates with Ar ion sputtering. This work also reveals that the Cu model surfaces are not poisoned by the reaction and exhibit 100% selectivity for alcohol dehydrogenation to aldehyde and hydrogen.

Multiscale Morphology of Nanoporous Copper Made from Intermetallic Phases

“…34−36 Wachs et al 35 found that C−H bond activation is the rate-determining step in ethanol dehydrogenation. In a recent study, Sykes and co-workers 38 used a combination of temperature-programmed experiments and scanning tunneling microscopy on Cu(111) and Cu(110) model surfaces to verify the two-step dehydrogenation of alcohols. Furthermore, they confirmed that dehydrogenation occurs at defect sites.…”

Ethanol-to-butadiene: the reaction and its catalysts

“…96,111,112 On metal oxides with acid-base pairs, the literature suggests that acetaldehyde is formed by a sequential mechanism that begins with the dissociation of ethanol into a surface ethoxy intermediate followed by the E2 or E1cb-elimination of a proton (Scheme 4(a)). 100,[113][114][115][116] According to Sykes et al, acetaldehyde formation occurs similarly on defective Cu, 117 suggesting that this mechanism is not limited to metal oxides. Surface ethoxy species were also detected on other transition metal oxide catalysts during IR-TPSR experiments with ethanol, leading to similar conclusions.…”

Tracing the reactivity of single atom alloys for ethanol dehydrogenation using ab initio simulations

“…In order to model the reactivity of SAAs, Sykes and coworkers have proposed a mechanistic pathway in which the O-H bond of ethanol is activated first on the SAA surface followed by the α-C-H bond, resulting into the formation of acetaldehyde. 23 The hypothesis is derived from the experiments on the model Cu (111) surface, 24,25 where the O-H bond is observed to activate at a significantly low (160 K) temperature. Our group has developed a comprehensive ab initio MKM to understand ethanol decomposition and dehydrogenation reactions on transition metal surfaces, including all possible mechanistic routes such as O-H, α-C-H, C-C, and C-O activation in ethanol.…”