Recent Trends in Catalysis for Syngas Production and Conversion

Synthesis gas (or syngas) is a mixture of CO and H₂ that can be produced from fossil fuels or biomass. Syngas is one of the crucial platform chemicals for the production of a variety of high-value compounds, such as synthetic hydrocarbons and oxygenated fuels. More syngas will be required to meet industrial demand. This Special Issue contains articles that contribute to syngas production, syngas conversion or application, and various methods of the catalyst synthesis. Whether it is strategies for synthesis/conversion of syngas or catalyst synthesis processes and reactions, these provide new ideas for syngas applications as well as in the field of catalysis.

This Special Issue contains ten articles, of which nine are research articles and one is a review article. In the review article [1], the thermodynamics, kinetics and reaction mechanism of the CO₂-CH₄ reforming reaction (CRM reaction) are reviewed. Since Ni-based catalysts exhibit high activity but have the problem of easy deactivation of carbon deposition, this paper further summarizes the research situation regarding carbon deposition on Ni-based catalysts, including the types of carbon deposition, the amount of carbon deposition, and the elimination of carbon deposition. As for how to improve the anti-carbon deposition ability of the Ni-based catalyst and how to eliminate carbon deposition, this paper focuses on two aspects: one is the resistance of carbon deposition from the perspective of catalyst optimization; the other is the elimination of carbon deposition from the perspective of process condition adjustment. The authors also present the perspectives on how to inhibit carbon deposition to improve the activity and stability of the CRM catalyst.

In [2], bimetallic layered double oxide (LDO) NiM (M = Cr, Fe) catalysts with nominal compositions of Ni/M = 2 or 3 were tailored from layered double hydroxides (LDH) using co-precipitation method to investigate the effects of trivalent metal (Cr or Fe) and the amount of Ni species on the structural, textural, reducibility and catalytic properties for CH₄/CO₂ reforming at low reaction temperatures (400–650 °C). The influences of the molar ratio and cationic composition in the preparation of the LDH precursors on the physicochemical properties of the target catalysts and on their performance for the dry reforming of methane were also evaluated.

Syngas to hydrocarbons via the Fischer–Tropsch (F-T) synthesis pathway is a valuable way to achieve syngas utilization. In [3], a series of cobalt carbide (Co₂C) catalysts were synthesized by exposure of Co/Al₂O₃ catalyst to CH₄ at different temperatures from 300 °C to 800 °C for F-T synthesis to hydrocarbons. The result shows that by increasing the carbidation temperature, the Co₂C content decreased, and the metallic cobalt content increased, which resulted in higher catalytic activity. For the catalysts prepared at higher temperatures, the presence of less Co₂C, which is transformed into hcp cobalt during the reduction with hydrogen, and the presence of less metallic fcc cobalt resulted in lower CO conversion and less heavy hydrocarbons.

In addition to the F-T synthesis mentioned above, the Special Issue also includes research using a new strategy for syngas to hydrocarbons. In [4], a dual-bed strategy was adopted to directly convert syngas to light paraffins, which includes an STD catalyst (CZA+Al₂O₃(C)) in the upper bed and methanol/DME conversion catalyst SAPO-34 in the lower bed. This dual-bed strategy allows the different catalysts to be operated at different temperatures in the reaction process, which can save energy, and the synthesis of methanol at low temperature is beneficial to extend the catalyst life and also provides a potential route for syngas conversion to valuable chemicals.

In [5], MCM-41 is selected as support to prepare xNi/MCM-41 catalysts with various Ni contents and the catalytic performance for CO methanation in a slurry-bed reactor is investigated under different reaction conditions. The reason for catalyst deactivation after reaction was analyzed. The aim is to clarify the relationship between the structures and the catalytic methanation performance.

The participation of CO in the oxidative carbonylation of methanol to dimethyl carbonate (DMC) is also a pathway for CO conversion. In [6], the reaction mechanisms governing oxidative carbonylation of methanol to DMC with Cu⁺, Cu²⁺, Cu₂O and CuO species in Y zeolites using density functional theory (DFT) were studied. The results are expected to guide the selection and preparation of CuY catalysts with the best catalytic activity for DMC synthesis.

Methanol and formaldehyde are important building blocks in the production from syngas, and the conversion of these products is worthy of attention. In [7], Ti-HMS supported vanadium oxide catalysts exhibited higher activities in the selective oxidation of methanol to dimethoxymethane, and the enhanced activity of the V-Ti-HMS catalyst is attributed to the improved dispersion and reducibility of vanadium oxides. In [8], a series of MnO₂ catalysts were obtained for formaldehyde oxidation using acid treatment, and the structure and properties of the acid-treated catalysts were investigated and the effect of acid treatment on the catalytic oxidation activity of formaldehyde was explained.

In [9], catalytic pyrolysis of LDPE was performed in a fixed-bed reactor using ZSM-5, HY and MCM-41 catalysts to obtain the three-phase products. The effect of pyrolysis temperature and catalyst type on product yield was explored. In [10], four MnO₂ with different crystalline structures were synthesized in the present study and the catalytic activity was evaluated in the oxidation of furfural to furoic acid and the factors affecting the catalytic performance over different MnO₂ are discussed.

In conclusion, the guest editors of the Special Issue “Recent Trends in Catalysis for Syngas Production and Conversion” would like to thank all the authors for their contributions, which demonstrate the importance of ongoing research in the field of syngas production and conversion. We also thank the reviewers for their hard work. In addition, we thank the journal Catalysts for the great opportunity to produce this Special Issue.