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

Abstract

Cu-Mn mixed oxides and mesoporous CaO-ZrO 2 solid base were prepared by complexing method and alcohothermal route, respectively, and they were mixed together as combined Cu-Mn/Ca-Zr catalyst which was evaluated for the direct synthesis of methyl formate (MF) from syngas in a slurry reactor. Cu-Mn and CaO-ZrO 2 samples were characterized by N 2 isotherm adsorption-desorption, XRD, SEM, TEM, XPS and CO 2 -TPD techniques. Under the optimum reaction conditions of 160 o C, 3 MPa, 3:7 for the ratio of methanol to N, N dimethylformamide, 40 g L -1for Cu-Mn sample, and 30 g L -1 for CaO-ZrO 2 sample, a lower CO conversion of 22.4 % was obtained over Cu-Mn/Ca-Zr, whereas the MF selectivity of 82.3% was higher than that of traditional catalyst (e.g. Cu-catalyst and NaOCH 3 ), which was due to the synergism between Cu-Mn and CaO-ZrO 2 samples. µmol g -1 h -1 and 121 µmol g -1 h -1 , respectively, while the low yield and poor stability limit the application of this process. This has stimulated a desire for the development of an alternative process.Direct synthesis of MF from syngas in liquid-phase system is significantly concerned by researchers due to its atomic economy and short reaction process. [22][23][24][25][26] The direct process follows the stoichiometry: 2CO+2H 2 → HCOOCH 3 , △H 0 R = -157.2 kJ mol -1 (1). 27 In the direct synthesis process, MF formed as an intermediate of methanol synthesis from syngas on mixed catalyst comprised of alkali or alkali earth compounds and Cu-based catalysts, 22 which contains homogeneous carbonylation of methanol on alkali or alkali earth compounds and heterogeneous hydrogenation of MF on Cu-based catalysts. Palekar et al. 23 controlled the selectivity of methanol and MF by changing reaction temperature and the ratio of CO to H 2 . They found that high reaction temperature and low CO/H 2 were beneficial to methanol; on the contrary, low reaction temperature and high CO/H 2 condition favored MF formation, and the similar results were also reported by Chen et al. 28 However, a critical problem in this process is that homogeneous alkali or alkali earth compounds is susceptible to CO 2 or H 2 O in reaction system, which accelerate the fall of the catalytic activity. 29-31 Moreover, alkali or alkali earth compounds distributed on the surface of Cu-based catalyst caused the blockage of active sites. 32In this work, CaO-ZrO 2 solid base and Cu-Mn mixed oxides were prepared and characterized by N 2 isotherm adsorption-desorption, XRD, TEM, SEM, XPS and CO 2 -TPD measurements. More importantly, the combined Cu-Mn/Ca-Zr catalyst prepared by mechanical mixing above two as-prepared samples was applied to the direct synthesis of MF from syngas in a batch slurry reactor for the first time. In addition, the influences of reaction parameters such as temperature, pressure, the ratio ratio of Ca to Zr is 0.5. Preparation of Cu-Mn/Ca-Zr catalystCu-Mn/CaO-ZrO 2 combined catalyst, noted as Cu-Mn/Ca-Zr, was prepared by mechanical mixing Cu-Mn mixed oxides and CaO-ZrO 2 solid base. The mass ratio of Cu-Mn ...

Hierarchical Manganese–Nickel Sulfide Nanosheet Arrays as an Advanced Electrode for All-Solid-State Asymmetric Supercapacitors

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