Influence of surface design on performance of MnO‐decorated nanocatalyst for olefin production from methanol: ZSM‐5@MnO core–shellversusMnO/ZSM‐5 dispersed nanocatalysts

Abstract

BACKGROUNDIn the assembly of nanoparticles (NPs) onto zeolites, the surface design of NPs has a great influence on various catalytic properties. Herein, ZSM‐5 was hydrothermally synthesized and its external surface was decorated by MnO NPs in two different surface designs: distributed MnO NPs and MnO shell.RESULTSThe synthesized MnO‐decorated samples, MnO/ZSM‐5 and ZSM‐5@MnO, were analyzed using various techniques. The results of these analyses reveal the formation of desired crystal phases without any impurities and confirm the perfect assembly of uniform MnO NPs on the surface of ZSM‐5. Also, it was found that the surface design of MnO NPs has a great impact on the physicochemical properties of the nanocatalyst. Basically, ZSM‐5 is highly selective toward propylene, but the shape selectivity of MnO NPs increases the selectivity of MnO‐decorated nanocatalysts toward ethylene. Moreover, this study delves deeply into differences in catalytic behaviors of the nanocatalysts during the methanol‐to‐olefin process and explains how they are attributed to the applied surface designs.CONCLUSIONSThe catalytic performance studies at optimum temperature show that the ZSM‐5@MnO nanocatalyst is more selective toward ethylene, and it has a nearly 20% higher methanol conversion rate compared to the MnO/ZSM‐5 nanostructured catalyst. Due to the surface acidity adjustment of MnO shell as well as high control of core–shell structure over the location of coke formation, the ZSM‐5@MnO nanocatalyst shows longer stability and its activity remains constant with time on stream. © 2020 Society of Chemical Industry

Ultrasound-assisted rapid hydrothermal design of efficient nanostructured MFI-Type aluminosilicate catalyst for methanol to propylene reaction

“…From the literature survey, the recorded peaks correspond to the MFI zeolite structure [29] , [43] . The observed peaks around 440 and 540 cm −1 are related to SiO 4 bending vibration and 5-membered rings, respectively [6] . Also, absorption bands at the range of 790 to 1520 cm −1 correspond to TO 4 tetrahedral and symmetric TOT modes [44] .…”

“…It is indicative that the physically adsorbed water trapped inside cavities is contributed by the IR band at wavenumber about 1710 cm −1 [13] , [43] . Moreover, the characteristic peak in the wavenumber of 3700 cm −1 is related to the vibration hydroxyl groups, as active sites, that present in the ZSM-5 cage accessible in the straight ten-ring channel that involved change by applying ultrasound-assisted hydrothermal methods [6] , [29] . A more detailed description of these acid sites can be found in the subsequent characterization results.…”

“…Light olefins especially consist of ethylene (C 2 H 6 ) and propylene (C 3 H 8 ) [4] . The C 2 H 6 /C 3 H 8 ratio of MTO products can vary considerably depending on the catalyst framework type and as well as reaction conditions [5] , [6] , [7] . In this case, methanol to propylene reaction (MTP) with high amount of propylene production seems to be a suitable strategy by increasing world demand for petrochemical plants [8] , [9] , [10] .…”