A Modeling Study of Operating Conditions and Different Supports on Fe-Co-Ce Nanocatalyst and Optimizing of Light Olefins Selectivity in the Fischer-Tropsch Synthesis

This study demonstrates the effect of operating conditions (Red-GHSV, inlet H2/CO, Oprat-GHSV) and the effect of Fe-Co-Ce nanocatalyst support. A statistical model using the response surface methodology (RSM) was applied with the target of achieving higher olefins selectivity in Fischer-Tropsch synthesis, which indicates the interaction effects of factors. The conditions under which three objectives optimization for maximizing olefins and minimizing paraffins and methane were determined. Synthesized nanocatalysts with various supports were characterized by XRD, SEM and TPR techniques

Directed transforming of coke to active intermediates in methanol-to-olefins catalyst to boost light olefins selectivity

Methanol-to-olefins (MTO), the most important catalytic process producing ethylene and propylene from non-oil feedstocks (coal, natural gas, biomass, CO2, etc.), is hindered by rapid catalyst deactivation due to coke deposition. Common practice to recover catalyst activity, i.e. removing coke via air combustion or steam gasification, unavoidably eliminates the active hydrocarbon pool species (HCPs) favoring light olefins formation. Density functional theory calculations and structured illumination microscopy reveal that naphthalenic cations, active HCPs enhancing ethylene production, are highly stable within SAPO-34 zeolites at high temperature. Here, we demonstrate a strategy of directly transforming coke to naphthalenic species in SAPO-34 zeolites via steam cracking. Fluidized bed reactor-regenerator pilot experiments show that an unexpectedly high light olefins selectivity of 85% is achieved in MTO reaction with 88% valuable CO and H2 and negligible CO2 as byproducts from regeneration under industrial-alike continuous operations. This strategy significantly boosts the economics and sustainability of MTO process.

Comparative Synthesis and Characterization of Nanostructured SAPO-34 Using TEA and Morpholine: Effect of Mono vs. Dual Template on Catalytic Properties and Performance toward Methanol to Light Olefins

Aim and Objective: Production of light olefins from methanol was studied over SAPO-34 molecular sieves exploring the effect of mono and dual templates. Herein, the single templates of TEA, morpholine and mixed template of TEA/morpholine (equal molar ratio of TEA and morpholine) were used to synthesize SAPO-34 catalysts. Materials and Methods: The prepared samples were prepared via hydrothermal synthesis method and characterized with XRD, FESEM, PSD, EDX, BET and FTIR techniques. Results: It was found that the crystallinity decreased upon applying TEA as template and also it can be noted that the intensity of the SAPO-34 phase peaks increased by increasing the morpholine in template mixture. Production of much smoother particles for the catalyst synthesized with binary template mixture of TEA/morpholine can be depended on the crystallinity increase. Si incorporation value was decreased for the catalyst with a major phase of SAPO-5 (topological structure of AFI). It is indicative that the TEA application would facilitate the formation of AFI structure which is incapable of the incorporating higher amounts of Si in to the crystallite framework. Conclusion: The nature of the template determines the morphology of final product due to different rate of crystal growth obtained in accordance with XRD and FESEM results. Therefore, the catalyst synthesized with TEA/morpholine mixture shows the best performance among synthesized samples in terms of life time in the MTO process sustaining light olefins selectivity at higher values (about 90% after 630 min TOS).

Enhancement of Light Olefins Selectivity Over N-Doped Fischer-Tropsch Synthesis Catalyst Supported on Activated Carbon Pretreated with KMnO4

Ammonium iron citrate was used as an iron precursor in order to prepare N-doped catalysts supported on KMnO4 pretreated activated carbon (10MnK-AC). Iron nitride was synthesized in company with the formation of α-Fe2O3 on 10MnK-AC. The characterizations of the catalysts show that nitrogen atoms were doped into iron lattice rather than the networks of the carbon support. The performance of Fischer-Tropsch synthesis to light olefins (FTO) suggest an improvement in O/P ratio (olefins to paraffins molar ratio of C2–C4) over the iron catalysts supported on 10MnK-AC. The further promotion of light olefins selectivity (up to 44.7%) was obtained over FeN-10MnK-AC catalyst owing to the collaborative contribution of the electron donor effect of nitrogen and the suppression effect on the second hydrogenation over 10MnK-AC support.

Heteropolyacid Salt Catalysts for Methanol Conversion to Hydrocarbons and Dimethyl Ether: Effect of Reaction Temperature

Phosphotungstic and silicotungstic acid salt catalysts (CuPW, CuSiW, FePW, FeSiW) were synthesized by substitution of protons with ferric and copper ions through a simple replacement reaction. The structure and thermal stability were characterized by IR, XRD and TG, and the salts showed a keggin structure and a thermal tolerance near 450 °C. Temperature programmed reactions indicated that the four catalysts showed similar trends in the change of methanol conversion, DME selectivity, and light olefins selectivity at 100–400 °C. Copper salt catalysts showed a 100% DME selectivity at temperatures ranging from 100–250 °C, while FeSiW and FePW catalysts had a 100% DME selectivity near 250 °C. Moreover, the heteropolyacid salt catalysts also produced a certain number of light olefins at the temperature ranging from 250–350 °C, and the CuSiW catalyst exhibited the highest ethylene and propylene selectivity of 44%. In the stability test evaluated at 200 °C, the catalysts showed different tendencies during the induction period and the same trends during the reduction period for the methanol conversion to DME, due to the differences in the strengths of the strong acid sites. Finally, the silicotungstic acid salt catalysts showed the longest lifetime of 120 h, much longer than the heteropolyacids. This approach provides an effective way to synthesize hydrocarbons through methanol, especially DME, at different temperatures using one catalyst.