Sodium compounds as catalysts for methanol dehydrogenation to water‐free formaldehyde

In this work, we examine the thermochemistry and kinetics of the partial oxidation of methanol to formaldehyde on silver surfaces. Periodic density functional theory calculations employing the BEEF‐vdW functional are used to identify the most stable phases of the silver surface under relevant reaction conditions and the reaction energetics are obtained on these surfaces. The calculated binding energies and transition state energies are used as input in a mean‐field microkinetic model providing the reaction kinetics on silver surfaces under different reaction conditions. Our results show that, under conditions pertaining to methanol partial oxidation, oxygen is present at low concentrations and it plays a critical role in the catalytic reaction. Surface oxygen promotes the reaction by activating the OH bond in methanol, thus forming a methoxy intermediate, which can react further to form formaldehyde. The dissociation of molecular oxygen is identified as the most critical step.

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“…Generally, formaldehyde can be produced from methanol via an oxidative or a non‐oxidative pathway [Eq. ]:

true 2 CH_{3} OH + normalO_{2} \to 2 CH_{2} normalO + 2 normalH_{2} normalO Δ_{f} H = - 159 kJ mol^{- 1} CH_{3} OH \to CH_{2} normalO + normalH_{2} Δ_{f} H = + 84 kJ mol^{- 1}

…”

Section: Introductionmentioning

confidence: 99%

Methanol Partial Oxidation on Ag(1 1 1) from First Principles

et al. 2016

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“…The volcano for CH 2 O production ( Fig. 4(d)) is similar to a lower right portion of the volcano for CH 3 O-H bond scission (Fig. 2(c)), indicating that the production of CH 2 O primarily proceeds through the CH 3 O-H path via a CH 3 O intermediate.…”

Section: Microkinetic Modelingmentioning

confidence: 74%

“…Ruf et al experimentally reported that without any catalyst, methanol could dehydrogenate to anhydrous CH 2 O at a very high temperature, 1173 K, with a CH 2 O yield being less than 20% and only 43% selective toward formaldehyde [7]. Anhydrous CH 2 O production from non-oxidative CH 3 OH dehydrogenation has been investigated on bulk and supported Ag, Zn, Cu, and Au catalysts [8][9][10][11][12][13][14][15][16], however, these catalysts were shown to deactivate a few hours. For instance, experimental work by Yamamoto et al reported that, a P-promoted CuO/SiO 2 catalyst with 50% CH 3 OH conversion and 80% CH 2 O selectivity, was partially deactivated over the course of 4 h, possibly due to sintering [9].…”

Section: Introductionmentioning

confidence: 98%

“…Recently, anhydrous CH 2 O has gained increased attention because of its important applications, such as the production of high polymeric polyoxymethylene, solid CH 2 O, polyacetal resin, agricultural chemicals, and medical intermediates [2]. Generally, CH 2 O can be obtained from oxidative or non-oxidative methanol dehydrogenation by the following processes [3]:…”

Section: Introductionmentioning

confidence: 99%

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Using microkinetic analysis to search for novel anhydrous formaldehyde production catalysts

Lausche

Peterson

et al. 2015

Surface Science

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a b s t r a c tDirect dehydrogenation of methanol to produce anhydrous formaldehyde is investigated using periodic density functional theory (DFT) and combining the microkinetic model to estimate rates and selectivities on stepped (211) surfaces under a desired reaction condition. Binding energies of reaction intermediates and transition state energies for each elementary reaction can be accurately scaled with CHO and OH binding energies as the only descriptors. Based on these two descriptors, a steady-state microkinetic model is constructed with a piecewise adsorbate-adsorbate interaction model that explicitly includes the effects of adsorbate coverage on the rates and selectivities as well as the volcano plots are obtained. Our results show that most of the stepped (211) puremetallic surfaces such as Au, Pt, Pd, Rh, Ru, Ni, Fe, and Co are located in a region of low activity and selectivity toward CH 2 O production due to higher rate for CH 2 O dehydrogenation than CH 2 O desorption. The selectivities toward CH 2 O production on Zn, Cu, and Ag surfaces are located on the boundary between the high and low selectivity regions. To find suitable catalysts for anhydrous CH 2 O production, a large number of A 3 B-type transition metal alloys are screened based on their predicted rates and selectivities, as well as their estimated stabilities and prices. We finally propose several promising candidates for the dehydrogenation of CH 3 OH.Published by Elsevier B.V.

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“…Many materials, including transition metal oxides, sodium carbonate, and zeolites, showed some activity in the title reaction. However, the results were not satisfactory due to their low conversion of methanol, low selectivity toward HCHO and/or the high reaction temperatures, about 800 or 900 • C [5][6][7][8][9][10][11]. Silver-based catalysts that are widely applied in the partial oxidation of methanol to HCHO [12][13][14][15] may be naturally a good choice for the process of the direct dehydrogenation of methanol, which our previous work has already proved to be possible [16,17].…”

Section: Introductionmentioning

confidence: 99%