Guilong Liu

Nanoparticles of Cu–Co alloy derived from layered double hydroxides and their catalytic performance for higher alcohol synthesis from syngas

A series of layered double hydroxides (LDHs) with different Cu/Co ratios were prepared according to the co-precipitation method and used as catalyst precursors for higher alcohol synthesis. The prepared samples were characterized by XRD, TPR, SEM, TEM and BET techniques. After calcination, the LDHs were transformed into a mixture of CuO, Co3O4, CuCo2O4 and alumina, and these oxides were mixed uniformly with sizes of several nanometers. For the sample with a ratio of Cu/Co = 1/2, the copper and cobalt species are mainly in the CuCo2O4 phase. In the reduction process, the superior mixed copper and cobalt species in nanoscale were reduced to Cu–Co alloy, which was confirmed by the XRD and TEM results. The prepared bimetallic catalysts showed high activity, good stability and very high selectivity to C2+ alcohols. With the best catalyst, CO conversion of 51.8%, selectivity to alcohols of 45.8% and 94.3 wt% of C2+OH in the total alcohols were obtained at 250 °C, 3 MPa and GHSV of 3900 mL (gcat h)−1.

Nanoparticles of Cu–Co alloy supported on high surface area LaFeO3—preparation and catalytic performance for higher alcohol synthesis from syngas

LaFeO3 supported Cu–Co bimetallic catalysts with high surface area and mesoporosity were prepared by impregnation combined with nanocasting method, and the resulting catalysts were used for higher alcohol synthesis (HAS) from syngas. These catalysts were characterized by using N2 adsorption and desorption, X-ray diffraction, temperature programmed reduction, transmission electron microscopy and energy dispersive spectrometry techniques. The results showed that the catalysts were highly active and selective to higher alcohols, and meanwhile stable for HAS. Characterization results indicated that Cu–Co was in the state of a solid solution alloy in the reduced catalysts, and the formation of Cu–Co alloy led to the high selectivity to higher alcohols. The elements in the catalysts were uniformly mixed and in interaction, thus sintering of the nanoparticles in the catalysts was restricted, resulting in a good stability. The high activity was mainly attributed to the high surface area and mesoporosity. Compared with Cu–Co/LaFeO3 prepared by conventional methods, Cu–Co/LaFeO3 with higher surface area and mesoporosity exhibited better activity and higher selectivity to higher alcohols. This design scheme may be applied to other bimetallic catalysts, and many transition metal ions can act as the lattice ions of perovskite-type oxides besides copper and cobalt.

Ni nanoparticles highly dispersed on ZrO2 and modified with La2O3 for CO methanation

To improve the anti-sintering and anti-carbon deposition ability of the supported metallic nano catalysts, a new scheme for designing and preparing catalysts for CO methanation is presented in this work. In the scheme, a series of xLaNiO3/ZrO2 (x = 15%, 20%, 25%) catalysts were prepared according to the citrate complexing method. The catalysts were characterized by using BET, XRD, H2-chemisorption, H2-TPR, and TEM technologies. After reduction, the LaNiO3/ZrO2 catalyst precursor preferred to form Ni nanoparticles highly dispersed on ZrO2 and modified with La2O3. Compared with the catalyst prepared by the traditional impregnation method, the Ni/La2O3–ZrO2 derived from LaNiO3/ZrO2 showed a higher dispersion of Ni on ZrO2 and exhibited higher CO conversion and CH4 selectivity. Meanwhile, the LaNiO3/ZrO2 catalyst showed excellent stability owing to the significant improvement in both anti-carbon deposition and anti-sintering. The catalyst prepared according to this scheme intensified the interaction between Ni and La2O3, thus favoring the synergistic effect of La2O3 and Ni, which led to the high dispersion of Ni nanoparticles as well as the very good anti-sintering and anti-carbon deposition ability.

Growing layered double hydroxides on CNTs and their catalytic performance for higher alcohol synthesis from syngas

Nanostructured CuCo-LDH/CNT composites were successfully synthesized according to the co-precipitation method and firstly used for higher alcohol synthesis. The structural characterization and morphological observation demonstrated that CuCo-LDHs were in situ grown on the CNTs surface, and the CNTs support favored the dispersion of LDHs; meanwhile, a mechanism for growing the LDHs on CNTs was proposed, and the reported methods could be expanded to prepare other LDHs/CNT composites. After reduction, due to the strong interaction between CuCo-LDHs and CNTs, Cu–Co alloy, nanoparticles with small and uniform size were obtained and highly dispersed on the Al2O3 matrix and CNTs surface. In particular, the high thermal conductivity of CNTs suppressed the formation of hot spots, thus effectively inhibited the generation of hydrocarbons and CO2. The resultant CuCo-LDHs/CNTs composite exhibited better catalytic performance and higher selectivity to C2+ alcohols than the pristine LDHs did, which turned out to be one of the best catalysts for HAS.Graphical Abstract