Promoter Effects on Iron–Silica Fischer–Tropsch Nanocatalysts: Conversion of Carbon Dioxide to Lower Olefins and Hydrocarbons at Atmospheric Pressure

Abstract

If CO2 hydrogenation is to become a viable process for the utilisation of CO2, improved catalysts are urgently needed. We report the promotional effects of Group 11 and 13 metals on the performance of iron–silica catalyst systems under atmospheric pressure. The addition of low loadings of gold resulted in a significant improvement in catalyst performance both in terms of conversion and selectivity to lower (C2–C4) olefins. Small loadings of indium proved highly effective for increasing CO2 conversion, whereas at higher loadings the selectivity to lower olefins could be dramatically increased. Catalysis tests involving palladium‐promoted systems also proved successful with large increases in selectivity towards C5+ hydrocarbons observed. The catalysts were characterised by X‐ray photoelectron spectroscopy, TEM and SEM, which confirmed the nanostructured nature of the catalytic species involved.

Kinetics of CO2 Hydrogenation to Hydrocarbons over Iron–Silica Catalysts

“…[19] Briefly,t he silica was suspended in the minimum amount of methanol. To this am ethanolic solution of Fe(NO 3 ) 3 ·9 H 2 Ow as added to give the a2 0wt% loading of iron in the final material.…”

“…[1,10] The authors have recently shown that while an iron-silica catalysth as relatively low activity with selectivityp rimarily to methane, the addition of promoters can shift selectivity towards lower (C 2 -C 4 )o lefins over 40 %. [19] While these results are promising, ad etailedu nderstanding of the kinetics and mass transfer limitations of this process is vital to both optimise catalyst performance and model or scale up the overall process. Due to the vast industrial interest shown in both the FT and WGS reactions ag reat deal of attention has been paid to both.…”

Shedding Light Onto the Nature of Iron Decorated Graphene and Graphite Oxide Nanohybrids for CO2 Conversion at Atmospheric Pressure

“…The resulting pre‐catalysts were followed by in situ generation of the iron active species through mild hydrogenations and then their testing as nano‐catalyst for the CO 2 activation following existing protocols. In our hands, a surprisingly short exposure time of only 40 minutes was found to give a comparable conversion rate with silica supported catalysts, and this intriguing result was assigned to the layered morphology and the accessible encapsulated iron nanoparticles within the graphene supports, vide infra …”

“…In our hands, a surprisingly short exposure time of only 40 minutes was found to give a comparable conversion rate with silica supported catalysts, and this intriguing result was assigned to the layered morphology and the accessible encapsulated iron nanoparticles within the graphene supports, vide infra. [10,36]…”

“…[12,[31][32][33][34][35] These works highlight the ability of graphene to act as a 2D catalyst support compared to previously investigated 3-dimensional structures such as nano-silica and zeolites and present comparable activities with that of similar systems based on multiwalled carbon nanotubes. [10,36]…”