Minggui Lin

CuFe, CuCo and CuNi nanoparticles as catalysts for higher alcohol synthesis from syngas: a comparative study

Higher alcohol synthesis (HAS) from syngas has attracted much attention and Cu-modified Fischer–Tropsch (FT) catalysts exhibited promising catalytic performance for HAS. In this paper, three model modified FT catalysts, CuFe, CuCo and CuNi nanoparticles, were synthesized by co-reduction method for the comparison of their performance in HAS. XRD, TEM and EDS characterizations for spent samples indicate that severe phase separation of Cu and Fe took place for CuFe, and Cu@Co core–shell structure formed with co-existence of Cu–Co alloy nanoparticles for CuCo, but only Cu–Ni alloys were observed for CuNi. Such structural change led to different performance in higher alcohol synthesis. As a result, CuFe mainly kept the original FT property of Fe, CuCo showed different performance from Co, and CuNi performed as methanol catalyst.

Advances in bifunctional catalysis for higher alcohol synthesis from syngas

Abstract Bifunctional catalysis on dual sites plays an important role in higher alcohol synthesis from syngas. It makes use of two types of active sites of which one type dissociates CO and forms surface alkyl species and the other type catalyzes non-dissociative CO adsorption for CO insertion and alcohol formation. To improve catalytic activity for higher alcohol synthesis, it is necessary to design dual sites on the atomic scale to give them high stability. The recent advances in higher alcohol synthesis using bifunctional catalysts are reviewed. The design of the dual sites, the structure of the dual sites on several typical catalyst systems, and the structural evolution of the dual sites during reaction are discussed using our latest research results.

Higher alcohol synthesis over Cu-Fe composite oxides with high selectivity to C2+OH

Abstract Cu-Fe composite oxides were prepared by co-precipitation method and tested for higher alcohol synthesis from syngas. The selectivity to C 2+ OH and C 6+ OH in alcohol distribution was very high while the methane product fraction in hydrocarbon distribution was rather low, demonstrating a promising potential in higher alcohols synthesis from syngas. The distribution of alcohols and hydrocarbons approximately obeyed Anderson-Schulz-Flory distribution with similar chain growth probability, indicating alcohols and hydrocarbons derived from the same intermediates. The effects of Cu/Fe molar ratio, reaction temperature and gas hourly space velocity (GHSV) on catalytic performance were studied in detail. The sample with a Cu/Fe molar ratio of 10/1 exhibited the best catalytic performance. Higher reaction temperature accelerated water-gas-shift reaction and led to lower total alcohols selectivity. GHSV showed great effect on catalytic performance and higher GHSV increased the total alcohol selectivity, indicating there existed visible dehydration reaction of alcohol into hydrocarbon.

Preparation of nanostructured molybdenum carbides for CO hydrogenation

Novel Mo2C/C nano/microcomposites were prepared via a facile approach involving the hydrothermal carbonization of a solution of glucose as a carbon precursor in the presence of ammonium heptamolybdate tetrahydrate. The samples were subsequently characterized by X-ray diffraction, X-ray photoelectron spectroscopy, thermal gravimetric analysis, N2-physisorption, scanning electron microscopy and high-resolution transmission electron microscopy. The effect of the carbonization agents (Ar, CH4/H2 = 0.2, and H2) was investigated. In particular, the carbonization behaviours and the evolution of Mo species in the catalysts during the carbonization process and the effect on CO hydrogenation for higher alcohol synthesis were extensively studied. During the carbonization step, the catalyst structures experienced an extensive restructuring process, which in turn induced the different performances in the higher alcohol synthesis. Moreover, the nanostructured molybdenum carbides synthesized by this method exhibited great performances in CO hydrogenation for higher alcohol synthesis.

A novel Cu–Mn/Ca–Zr catalyst for the synthesis of methyl formate from syngas

A novel catalyst comprised of Cu–Mn mixed oxides and CaO–ZrO2 solid base has contributed to a high-performance methyl formate (MF) synthesis from syngas in a slurry reactor. Cu–Mn mixed oxides and mesoporous CaO–ZrO2 solid base were prepared by complexing method and alcohothermal route, respectively, and they were characterized by N2 isotherm adsorption–desorption, XRD, SEM, TEM, XPS and CO2-TPD techniques. Under the optimum reaction conditions of 160 °C, 3 MPa, 3 : 7 for the ratio of methanol to N,N-dimethylformamide, 40 g L−1 Cu–Mn sample, and 30 g L−1 CaO–ZrO2 sample, a low CO conversion of 22.4% was obtained over Cu–Mn/Ca–Zr, whereas the MF selectivity of 82.3% was higher than that of the traditional catalyst (e.g. Cu-catalyst and NaOCH3), which was due to the synergism between Cu–Mn and CaO–ZrO2 samples.

High selectivity for n-dodecane hydroisomerization over highly siliceous ZSM-22 with low Pt loading

Highly siliceous ZSM-22 was synthesized under hydrothermal conditions with ZSM-22 seeds. Characterization by FT-IR and 1H and 29Si NMR spectroscopy confirms that due to the existence of defective sites in the siliceous ZSM-22, acidic silanol groups including vicinal silanol and silanol nests are detected. Acidic silanol groups are considered as the acid sites of siliceous ZSM-22. As a result, siliceous ZSM-22 shows much lower acid site density and lower acid strength than silica–alumina ZSM-22 which contains hydroxyl groups bridging Si and Al as acid sites. In n-dodecane isomerization, Pt/siliceous ZSM-22 shows much higher isomer selectivity than Pt/silica–alumina ZSM-22. Furthermore, a lower loading amount of Pt on siliceous ZSM-22 (about 0.2 wt% Pt) can lead to high isomer selectivity. Owing to the acidic silanol groups and the low acid site density of siliceous ZSM-22, a good balance between metal and acid function in Pt/siliceous ZSM-22 is achieved, which results in a lower allowable Pt loading value and higher isomer selectivity.