Cation distribution in Zn–Cr spinel structure and its effects on synthesis of isobutanol from syngas: Structure–activity relationship

The heating efficiency of magnetic nanoparticles under an alternating magnetic field

Hysteresis loss and relaxation loss are the two dominant heating mechanisms of magnetic nanoparticles (MNPs) in an alternating magnetic field (AMF). In magnetic induction hyperthermia, heating efficiency is one of the crucial factors. It is proposed that the MNPs with a dominant heating mechanism of relaxation loss will exhibit a higher heating efficiency. However, the relative experiments supporting the proposal is still absent due to the difficulty of obtaining the MNPs with the same components and similar morphology but different dominant heating mechanism. Here, the post-processing method of calcination is employed to change the cation distribution of the MNPs (Fe₃O₄ and Zn_0.54Co_0.46Cr_0.6Fe_1.4O₄), so as to obtain the MNPs with similar morphology but different dominant heating mechanism. The magnetic heating experiments were conducted to examine the heating efficiency. The results suggest that the MNPs with relaxation loss have a higher heating efficiency under the investigated AMF.

Electroplating sludge-derived metal and sulfur co-doping catalyst and its application in methanol production by CO2 catalytic hydrogenation

Electroplating sludge is a hazardous waste and its recycling is a hot topic. Electroplating sludge usually contains plenty of transition metals and multi-hetero atoms, which are potential resources. For the first time, this work synthesized spinel catalyst from Zn- and Cr-containing electroplating sludges by a simple calcination method, and applied the obtained catalysts in CH₃OH production by CO₂ catalytic hydrogenation. The spinel was doped by various heteroatoms, including Fe, Mn, Cu, and even S. According to detailed characterizations, the metal doping increased the low-temperature conversion efficiency of CO₂ but decreased the CH₃OH selectivity at the same time. After a further doping of S, although CO₂ conversion efficiency was slightly decreased, the selectivity of CH₃OH was significantly increased. After all, the optimized catalyst attained a conversion efficiency of 8.6% (CO₂) as well as a selectivity of 73.3% (CH₃OH) at 250 °C and 3 MPa. As a result, above results realized high-value-added utilization of hazardous waste and producing valuable product at the same time, which was in favor of circular development.

Role of Ga3+ promoter in the direct synthesis of iso-butanol via syngas over a K–ZnO/ZnCr2O4 catalyst

ZG, gallium cluster and ZnGa₂O₄ were formed by introducing Ga³⁺ to K–ZnO/ZnCr₂O₄ iso-butanol catalyst. Only a moderate amount of ZG promotes the space time yield (STY) and selectivity of alcohols for iso-butanol synthesis.

Enhanced propane dehydrogenation to propylene over zinc-promoted chromium catalysts

A small-size Zn–Cr spinel with defect sites formed by adding Zn to Cr₂O₃ is favorable for the PDH reaction.

Effect of Preparation Method on ZrO2-Based Catalysts Performance for Isobutanol Synthesis from Syngas

Two types of amorphous ZrO2 (am-ZrO2) catalysts were prepared by different co-precipitation/reflux digestion methods (with ethylenediamine and ammonia as the precipitant respectively). Then, copper and potassium were introduced for modifying ZrO2 via an impregnation method to enhance the catalytic performance. The obtained catalysts were further characterized by means of Brunauer-Emmett-Teller surface areas (BET), X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), and In situ diffuse reflectance infrared spectroscopy (in situ DRIFTS). CO hydrogenation experiments were performed in a fixed-bed reactor for isobutanol synthesis. Great differences were observed on the distribution of alcohols over the two types of ZrO2 catalysts, which were promoted with the same content of Cu and K. The selectivity of isobutanol on K-CuZrO2 (ammonia as precipitant, A-KCZ) was three times higher than that on K-CuZrO2 (ethylenediamine as precipitant, E-KCZ). The characterization results indicated that the A-KCZ catalyst supplied more active hydroxyls (isolated hydroxyls) for anchoring and dispersing Cu. More importantly, it was found that bicarbonate species were formed, which were ascribed as important C1 species for isobutanol formation on the A-KCZ catalyst surface. These C1 intermediates had relatively stronger adsorption strength than those adsorbed on the E-KCZ catalyst, indicating that the bicarbonate species on the A-KCZ catalyst had a longer residence time for further carbon chain growth. Therefore, the selectivity of isobutanol was greatly enhanced. These findings would extend the horizontal of direct alcohols synthesis from syngas.

Insight into the branched alcohol formation mechanism on K–ZnCr catalysts from syngas

The first C–C bond formation is from the reaction of CO and CHO (formyl) on the K–ZnCr catalysts.

Status and prospects in higher alcohols synthesis from syngas

Higher alcohols are important compounds with widespread applications in the chemical, pharmaceutical and energy sectors. Currently, they are mainly produced by sugar fermentation (ethanol and isobutanol) or hydration of petroleum-derived alkenes (heavier alcohols), but their direct synthesis from syngas (CO + H₂) would comprise a more environmentally-friendly, versatile and economical alternative. Research efforts in this reaction, initiated in the 1930s, have fluctuated along with the oil price and have considerably increased in the last decade due to the interest to exploit shale gas and renewable resources to obtain the gaseous feedstock. Nevertheless, no catalytic system reported to date has performed sufficiently well to justify an industrial implementation. Since the design of an efficient catalyst would strongly benefit from the establishment of synthesis-structure-function relationships and a deeper understanding of the reaction mechanism, this review comprehensively overviews syngas-based higher alcohols synthesis in three main sections, highlighting the advances recently made and the challenges that remain open and stimulate upcoming research activities. The first part critically summarises the formulations and methods applied in the preparation of the four main classes of materials, i.e., Rh-based, Mo-based, modified Fischer-Tropsch and modified methanol synthesis catalysts. The second overviews the molecular-level insights derived from microkinetic and theoretical studies, drawing links to the mechanisms of Fischer-Tropsch and methanol syntheses. Finally, concepts proposed to improve the efficiency of reactors and separation units as well as to utilise CO₂ and recycle side-products in the process are described in the third section.

Binary ZnO/Zn–Cr nanospinel catalysts prepared by a hydrothermal method for isobutanol synthesis from syngas

A series of binary ZnO/Zn–Cr nanospinel catalysts were prepared by a hydrothermal method and applied in direct synthesis of isobutanol from syngas, during which the effect of the hydrothermal time/temperature on their catalytic performance in the isobutanol synthesis has been investigated at 400 °C and 10 MPa.

The role of potassium promoter in isobutanol synthesis over Zn–Cr based catalysts

The potassium promoter would tailor the microstructure of the Zn–Cr spinel and stabilize the surface hydroxyl species which greatly facilitate the formate of isobutanol.

The real active sites over Zn–Cr catalysts for direct synthesis of isobutanol from syngas: structure-activity relationship

The isobutanol productivity is closely related to the cation disorder distribution.