One-Step Synthesis of Aromatics from Syngas over K-Modified FeMnO/MoNi-ZSM-5

Abstract

Aromatics produced from syngas have been attracting much more attention in recent years. In this study, the K-modified FeMnO/​MoNi-ZSM-5 catalyst was used in the one-step conversion of syngas to aromatics. The effects of K loading contents on the catalytic activity and the stability of the FeMnO/​MoNi-ZSM-5 catalyst were investigated. In addition, the conversion of CO and the selectivity of the products were analyzed. XRD, EDS, TG, XPS, and BET were carried out to characterize the properties of the catalysts before and after reaction. It can be investigated that the loading of K promoted the CO adsorption performance and the carburization of iron oxide on the catalyst, which increased the stability of the catalyst and inhibited the formation of CH4 and CO2.

Influential Role of Elemental Migration in a Composite Iron–Zeolite Catalyst for the Synthesis of Aromatics from Syngas

“…Fe is a conventional F–T synthesis catalyst, in which C 2 –C 4 olefin selectivity increased from 19 to 27% and the CH 4 selectivity was suppressed from 26 to 17% with the appropriate addition of Mn (Figure S1). After integration with the HZSM-5 zeolite, light olefins were cyclized into aromatics with a remaining selectivity of less than 0.2% (Figure S1), which demonstrated that the olefins were intermediates of the aromatics’ synthesis reaction . However, the composition of the NFM catalyst could be essential for the aromatic selectivity.…”

“…The weight-increasing peak at 200–400 °C is ascribed to the oxidation of the active phase such as iron carbide, while the weight loss at 400–700 °C is identified as the oxidation of deposited carbon . For the NFM catalyst, the intensity of weight-increasing peaks increased with higher Na contents, further proving that the formation of the active phase increased with higher Na contents, while for the HZ zeolite, the sample integrated with the NFM catalyst having a higher Na content exhibited a lower carbon deposition peak. It can be inferred that a higher Na content resulted in a larger portion of light olefinic intermediates, restraining the generation of inactive carbonaceous compounds .…”

“…The comparative catalyst was prepared with the coprecipitation method by dropping nitrate and NaOH solutions together into water, keeping the pH at 9, and following the other conditions the same as those in the sol-precipitation method. The Fe/Mn mole ratio was maintained at 3:2, and the prepared catalyst was named as NFM-c catalyst.…”

“…Although the relatively higher conversion and aromatic selectivity are achievable by the Fe-based composite catalyst, the stability generally being less than 100 h remains a big challenge to overcome. , Oligomerization of olefinic intermediates may lead to carbon deposition on HZSM-5, blocking the pore channels and covering the surface acid sites of the zeolite, which may be an important reason for the diminishing performance of the composite catalyst. − It has been discovered that carbon deposition could be restrained through promoting the internal and external diffusion of reactants, ,, while mass transfer could be largely accelerated through the decrease of the zeolite crystal size, rendering nano-HZSM-5 to be a promising solution for prolonging the catalyst stability. Nevertheless, after removing the carbon deposition through calcination in air, a decrease in performance was still observed for the composite catalysts, revealing that there might be some other factors inducing the decline of zeolite activity except for carbon deposition.…”

Direct conversion of syngas to aromatics: A review of recent studies

“…It is worth noting that the aromatization of olefins did not follow the hydrogen transfer pathway during this process. Cheng et al [80] used a K-modified FeM-nO/MoNi-ZSM-5 catalyst in a one-step conversion of syngas to aromatics and obtained a BTX selectivity of 56.4% at 4 MPa, 370 °C, 1395 h −1 and a volume flow ratio of H2/CO = 2. The addition of K could promote the CO adsorption and carburization of iron oxide, consequently increasing the catalyst stability and inhibiting the formation of CH4 and CO2.…”