Direct Conversion of Syngas into Methyl Acetate, Ethanol, and Ethylene by Relay Catalysis via the Intermediate Dimethyl Ether

Abstract

Selective conversion of syngas (CO/H2) into C2+ oxygenates is a highly attractive but challenging target. Herein, we report the direct conversion of syngas into methyl acetate (MA) by relay catalysis. MA can be formed at a lower temperature (ca. 473 K) using Cu‐Zn‐Al oxide/H‐ZSM‐5 and zeolite mordenite (H‐MOR) catalysts separated by quartz wool (denoted as Cu‐Zn‐Al/H‐ZSM‐5|H‐MOR) and also at higher temperatures (603–643 K) without significant deactivation using spinel‐structured ZnAl2O4|H‐MOR. The selectivity of MA and acetic acid (AA) reaches 87 % at a CO conversion of 11 % at 643 K. Dimethyl ether (DME) is the key intermediate and the carbonylation of DME results in MA with high selectivity. We found that the relay catalysis using ZnAl2O4|H‐MOR|ZnAl2O4 gives ethanol as the major product, while ethylene is formed with a layer‐by‐layer ZnAl2O4|H‐MOR|ZnAl2O4|H‐MOR combination. Close proximity between ZnAl2O4 and H‐MOR increases ethylene selectivity to 65 %.

Defect-engineered zeolite porosity and accessibility

“…We will discuss in detail the structural descriptors that dictate the dissolution behavior of zeolite crystals leading to materials with a multi-model pore structure. The feasibility of this approach is exemplified by the treatment of the MOR-type zeolite [19], an essential active component in a number of catalytic reactions, such as carbonylation [20][21][22], conversion of methane into methanol [23], selective conversion of syngas [24], selective catalytic reduction of NOx [25], hydroisomerization [26] and others. Besides the 12-member ring (MR) channel running along the c axis, mordenite contains an 8-MR side pocket that could contribute substantially to its performance [27][28].…”

Unravelling Proximity-Driven Synergetic Effect within CIZO–SAPO Bifunctional Catalyst for CO2 Hydrogenation to DME

“…CO 2 hydrogenation to various products is one of the most extensively studied topics. − Among all the possible products via this route, the production of dimethyl ether (DME) stands out as a promising way for the utilization of CO 2 . Not only does DME serve as building block for the synthesis of methyl acetate (MA), acetic acid (AA), and even ethanol through carbonylation reactions, − it is also a possible substitute for propane in the liquefied petroleum gas (LPG) and clean fuel for diesel engines, ,, which could serve as an option for reducing the petroleum dependency. Therefore, the study of CO 2 hydrogenation to DME has been attracting more and more attention in recent years.…”

Synergistic Catalysis of Al and Zn Sites of Spinel ZnAl2O4 Catalyst for CO Hydrogenation to Methanol and Dimethyl Ether

“…Three likely mechanisms were proposed: (i) sequential hydrogenation mechanism via formyl and methoxy intermediates to methanol, − (ii) formate mechanism via formate and methoxy intermediates to methanol, − and (iii) side-on hydrogenation mechanism via formaldehyde and methoxy intermediates to methanol . Recently, combinations of metal oxide composites and zeolites have demonstrated great capacities in selectively catalyzing CO or CO 2 hydrogenation to a variety of valuable chemicals. − Spinel ZnAl 2 O 4 was used as a component of the catalysts for CO and CO 2 hydrogenations. ,, Saussery and Lavalley studied CO hydrogenation to methanol catalyzed by 15% Cu-ZnAl 2 O 4 at 1.0 MPa of 525 K and proposed that ZnAl 2 O 4 was responsible for the formation of bidentate formate and methoxy intermediates and copper promoted the formate reduction reaction, in which the rate-controlling step was the desorption of methoxide. Liu et al reported that ZnAl 2 O 4 itself could selectively catalyze syngas to dimethyl ether and methanol and proposed that the formate species formed by CO reaction with surface OH was the key intermediate for CO hydrogenation to methanol.…”