Syngas Conversion to Hydrocarbons on Zirconia-Supported Iron Catalysts

Recent advances in the routes and catalysts for ethanol synthesis from syngas

Ethanol, as one of the important bulk chemicals, is widely used in modern society. It can be produced by fermentation of sugar, petroleum refining, or conversion of syngas (CO/H₂). Among these approaches, conversion of syngas to ethanol (STE) is the most environmentally friendly and economical process. Although considerable progress has been made in STE conversion, control of CO activation and C-C growth remains a great challenge. This review highlights recent advances in the routes and catalysts employed in STE technology. The catalyst designs and pathway designs are summarized and analysed for the direct and indirect STE routes, respectively. In the direct STE routes (i.e., one-step synthesis of ethanol from syngas), modified catalysts of methanol synthesis, modified catalysts of Fischer-Tropsch synthesis, Mo-based catalysts, noble metal catalysts and multifunctional catalysts are systematically reviewed based on their catalyst designs. Further, in the indirect STE routes (i.e., multi-step processes for ethanol synthesis from syngas via methanol/dimethyl ether as intermediates), carbonylation of methanol/dimethyl ether followed by hydrogenation, and coupling of methanol with CO to form dimethyl oxalate followed by hydrogenation, are outlined according to their pathway designs. The goal of this review is to provide a comprehensive perspective on STE technology and inspire the invention of new catalysts and pathway designs in the near future.

Direct Conversion of Syngas to Light Olefins through Fischer-Tropsch Synthesis over Fe-Zr Catalysts Modified with Sodium

Fe-Zr-Na catalysts synthesized by coprecipitation and impregnation methods were implemented to investigate the promoting effects of Na and Zr on the iron-based catalyst for high-temperature Fischer-Tropsch synthesis (HTFT). The catalysts were characterized by Ar adsorption-desorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, CO temperature-programmed desorption, H2 temperature-programmed desorption, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy (MES). The results indicated that Na changed the active sites on the catalyst surface for the CO and hydrogen adsorption, owing to the electron migration from Na to Fe atoms, which resulted in an enhanced CO dissociative adsorption and a decrease in hydrogen adsorption on the metallic Fe surface. The decreased H/C ratio on the catalyst surface accounted for the increased chain propagation and weakened hydrogenation of light olefins. Besides, Na could also facilitate the carbonization of catalysts and protect the iron carbide against oxidation, which provides more active sites for HTFT reaction and is beneficial to the C-C coupling. Zr could decrease the hematite crystallite size and stabilize the active phase to improve the HTFT activity. At an optimal Na loading of 1.0 wt %, the Fe-Zr-1.0Na catalyst exhibited the highest light olefin selectivity of 35.8% in the hydrocarbon distribution at a CO conversion of 95.2%.

Promotional effect of Mn modification on DeNOx performance of Fe/nickel foam catalyst at low temperature

Manganese (Mn)-modified ferric oxide/nickel foam (Fe/Ni) catalysts were prepared using Ni as a carrier, Fe and Mn as active components to study NH₃-SCR of NO_x at low temperature. The effects of different Fe loads and Mn-modified Fe/Ni catalysts on the DeNO_x activity were investigated. Results show that when the amount of Fe is 10%, Fe/Ni catalyst has the highest NO_x conversion. For the Mn-modified Fe/Ni catalysts, the NO_x conversions firstly increase and then decrease with the Mn loading amount increasing. 3MnFe/Ni catalyst shows high NO_x conversions, which reach 98.4-100% at 120-240 °C. The characterization analyses reveal that Mn-modified Fe/Ni catalysts increase the FeO_x dispersion on Ni surface, improve significantly the valence ratio of the Fe³⁺/Fe²⁺, the content of lattice oxygen which promotes the catalyst storage and exchange oxygen capacity at low temperature, and the number of Brønsted active acid sites on the catalyst surface, and enhance the low-temperature redox capacity. These factors remarkably increase the NO_x conversions at low temperature. Especially, 3Mn10Fe/Ni catalyst not only has excellent DeNO_x activity but also has better water resistance. However, the anti-SO₂ poisoning performance needs to be improved. To further analyze the reason why different catalysts show different DeNO_x performance, the reaction kinetics was also explored.

Highly efficient Fischer–Tropsch synthesis over an alumina-supported ruthenium catalyst

A highly active catalyst for Fischer–Tropsch synthesis at 423 K was prepared, on which the adsorbed CO dissociated at 303 K.