Selective Methanol Carbonylation to Acetic Acid on Heterogeneous Atomically Dispersed ReO₄/SiO₂ Catalysts

Abstract

Methanol carbonylation to acetic acid (AA) is a large-scale commodity chemical production process that requires homogeneous liquid-phase organometallic catalysts with corrosive halide-based cocatalysts to achieve high selectivity and activity. Here, we demonstrate a heterogeneous catalyst based on atomically dispersed rhenium (ReO4) active sites on an inert support (SiO2) for the halide-free, gas phase carbonylation of methanol to AA. Atomically dispersed ReO4 species and nanometer sized ReO x clusters were deposited on a high surface area (700 m2/g) inert SiO2 using triethanolamine as a dispersion promoter and characterized using aberration corrected scanning transmission electron microscopy (AC-STEM), UV–vis spectroscopy, and X-ray absorption spectroscopy (XAS). Reactivity measurements at atmospheric pressure with 30 mbar of methanol and CO (1:1 molar ratio) showed that bulk Re2O7 and ReO x clusters on SiO2 (formed at >10 wt %) were selective for dimethyl ether formation, while atomically dispersed ReO4 on SiO2 (formed at <10 wt %) exhibited stable (for 60 h) > 93% selectivity to AA with single pass conversion >60%. Kinetic analysis, in situ FTIR, and in situ XAS measurements suggest that the AA formation mechanism involves methanol activation on ReO4, followed by CO insertion into the terminal methyl species. Further, the introduction of ∼0.2 wt % of atomically dispersed Rh to 10 wt % atomically dispersed ReO4 on SiO2 resulted in >96% selectivity toward AA production at volumetric reaction rates comparable to homogeneous processes. This work introduces a new class of promising heterogeneous catalysts based on atomically dispersed ReO4 on inert supports for alcohol carbonylation.

Co Single Atoms in ZrO2 with Inherent Oxygen Vacancies for Selective Hydrogenation of CO2 to CO

“…CO 2 recycling involves its hydrogenation to C1 compounds (CO, CH 3 OH, and CH 4 ) that are further converted to value-added chemicals. Among the C1 products, CO is a resource for the synthesis of alcohols, liquid hydrocarbons, and organic acids using the existing infrastructure for syngas conversion. − In the hydrogenation of CO 2 to CO (eq ), also known as reverse water gas shift reaction (RWGS), increasing CO selectivity is a challenge because methanol and methane are formed simultaneously. …”

Insights into the Mechanism of n-Hexane Reforming over a Single-Site Platinum Catalyst

“…The reduction of particle size to single-atom level always achieves the maximum utilization of expensive noble metals, along with enhancement of activity, stability or selectivity. [9][10] However, typically in most application of SSCs, the scientists always focused on some small molecule reactant due to the lack of an ensemble of active metal atoms adjacent to the noble metal single atom. [11][12] Hence, investigating the reaction mechanism of a large probe molecule on SSCs and designing a novel catalytic material are the goal of our studies to accelerate the development of next generation SSCs.…”

“…[11][12] Hence, investigating the reaction mechanism of a large probe molecule on SSCs and designing a novel catalytic material are the goal of our studies to accelerate the development of next generation SSCs. [4][5][6][7][8][9] Catalytic reforming of linear hydrocarbons is one of the petroleum refining processes for upgrading light hydrocarbon feedstocks, [13] involving dehydrocyclization, isomerization, and dehydrogenation. [14][15][16] The hydrocarbon stream needs to be heated due to difficulty for C-H activation in reforming reactions.…”

“…Recently, the discovery of single-site catalysts (SSCs), where single metal sites are anchored on a support via the interaction with neighboring atoms (e.g., N or O), has opened up a new research frontier in the catalysis field. − Many catalytic reactions have been explored, such as selective methane oxidation to methanol and acetic acid using Rh SSCs, CO oxidation and hydrogen generation from methanol using Pt SSCs, − etc. The reduction of the particle size to the single-atom level always achieves the maximum utilization of expensive noble metals, along with enhancement of activity, stability, or selectivity. , However, typically in most applications of SSCs, the scientists have focused on some small-molecule reactant because of the lack of an ensemble of active metal atoms adjacent to the noble metal single atom. , Hence, investigating the reaction mechanism of a large probe molecule on SSCs and designing a novel catalytic material are the goal of our studies to accelerate the development of next-generation SSCs. − …”

Atomic-Scale Pd on 2D Titania Sheets for Selective Oxidation of Methane to Methanol

“…Importantly, ASMs have a minimal number of choices of binding sites for reactants or intermediates . As a result, they have exhibited higher reactive selectivity than nanoparticle catalysts, which have multiple types of reactive sites. , Further, ASMs with a low coordination number could prohibit the successive dehydrogenation of CH 4 and stabilize the • CH 3 radical, a key intermediate for the activation of CH 4 to CH 3 OH …”