N,O‐Codoped Onion‐like Carbon Catalyzed Selective Oxidation of Methanol to Dimethoxymethane: Structure‐Activity Relationship

Abstract

One‐step synthesis of dimethoxymethane (DMM) via methanol oxidation under the catalysis of nanocarbon is a green and sustainable chemical industrial process. In this work, we successfully prepared nitrogen, oxygen codoped onion‐like carbon (NOLC) via a simple thermal treatment method, which was applied to one‐step synthesis of DMM. The physicochemical characterization results revealed that nitrogen and oxygen elements were successfully introduced into the onion‐like carbon (OLC) catalyst. The proposed NOLC catalysts exhibited DMM selectivity of 75% at relatively low reaction temperature (150 oC) and long stability over 10 h. In‐situ titration experiments revealed that the carboxylic acid groups on NOLC surface were the main acidic active sites. The Clemmensen reduction control experiment revealed that the carbonyl groups were the active sites for the formation of formaldehyde. The basic reaction kinetics and mechanism such as reaction orders, apparent activation energy and rate determining step etc. for one‐step synthesis of DMM via methanol were studied systematically. The present work has shown an important structure‐function relation for designing highly efficient nanocarbon catalyzed methanol conversion reaction system that the appropriate redox/acid intensity on catalyst surface through the modulation of N and O elements would effectively improve the selectivity of DMM.

Non‐Oxidative Conversion of Methanol to Dimethyl Ether, Methyl Formate and Dimethoxymethane over Cu/Hβ Catalyst: Tailoring Product Selectivity

“…[6,9,58] Very recently, Bai et al reported a metal-free N,O-codoped carbon catalyst for the oxidative dehydrogenation of methanol to DMM with high DMM selectivity of 75 % at low reaction temperature (150 °C) and assigned the acidic and dehydrogenative active sites to carboxylic acid and carbonyl groups of the catalyst, respectively. [59] However, despite the good catalytic performances and technological readiness of the oxidative routes, the loss of valuable H 2 as H 2 O causes low exergy efficiency and high carbon footprint, being the major disadvantage of the established routes. [53,55,60] Besides CO 2 reduction with H 2 to form DMM, which was recently published by Klankermayer and co-workers, [61] the continuous gas-phase nonoxidative dehydrogenation (NOD) of methanol to DMM, with the formation of H 2 instead of H 2 O, is a captivating route for technical implementation.…”