Lei Niu

Hydrogenolysis of glycerol to propanediols over Cu-MgO/USY catalyst

Abstract A series of acid-base bifunctional catalysts composed of USY with different Cu and MgO loadings were prepared, characterized, and tested for the hydrogenolysis of glycerol. The USY support retained the Y zeolite structure, and the introduction of MgO enhanced the dispersion of Cu in the support. At 200 °C, 3.5 MPa H2, 10 h and with a 6% 0.2Cu-MgO/USY catalyst, 83.6% conversion of glycerol with 40% selectivity to 1,2-propanediol (1,2-PDO) and 19.4% selectivity to 1,3-propanediol (1,3-PDO) was achieved.

Atomic Layer Deposition of ZnO Thin Films on ZSM-5 Zeolite and Its Catalytic Performance in Chichibabin Reaction

A series of ZnO thin film modified ZSM-5 zeolites was prepared by atomic layer deposition (ALD) method with different ALD cycle numbers. These samples were characterized by nitrogen adsorption–desorption, ICP-AES, XPS, TEM and NH3-TPD techniques. The results of these characterizations showed that the thin film was ZnO, which was deposited on the surface of ZSM-5, especially the edge. The surface and pores of ZSM-5 was covered progressively by the increase of ALD cycles. By relating the Zn content of each cycle to the characters of ALD method, a deposition model of ZnO on ZSM-5 substrate was deduced. The surface acidity of the prepared samples can be tuned by adjusting the ALD cycle number as well. The catalytic properties of these samples were evaluated in Chichibabin reaction of acetaldehyde and ammonia. They could not only highly enhance the total yield of pyridine bases, but also could change the product distribution.Graphical Abstract

Selective hydrogenolysis of glycerol to 1,2-propanediol on the modified ultrastable Y-type zeolite dispersed copper catalyst

A series of dealumination ultrastable Y-type zeolite (DUSY) supported Cu catalysts with different Cu loadings were prepared, characterized and tested in the hydrogenolysis of glycerol. The results showed that DUSY retained the Y zeolite structure and generated abundant of secondary mesoporous, which not only facilitated the 1,2-propanediol (1,2-PDO) to diffuse out the catalyst, but also improved the dispersion of Cu. Cu/DUSY catalyst exhibited single weak acid sites and unique reduced structure of Y type zeolite and resulted in a more concentrated product distribution, primarily 1,2-PDO with few glycols.

Performance of Bulk and Silica Supported Vanadium–Chromium Catalysts in the Ammoxidation of 3-Picoline

Bulk and silica supported vanadium–chromium oxide (VCrO) catalysts with different VCrO loadings were prepared and their catalytic activity was evaluated in the ammoxidation of 3-picoline to nicotinonitrile. The silica supported catalysts had larger surface area and different active phases compared with the bulk catalyst. These differences varied the acidity and reducibility of the catalysts and finally resulted in distinction in catalytic properties. The high selectivity was confirmed to be related to the low surface density of acid sites, and the high activity coincided with the high surface area and reducibility.Graphical Abstract

Manganese(II) naphthenate as effective catalyst for the clean oxidation of 2-methylnaphthalene by hydrogen peroxide

Oxidation of 2-methylnaphthalene (2-MN) with aqueous hydrogen peroxide was conducted in acetic acid. The epoxidation pathway was investigated by increasing the CH3CO3H content and adding manganese(II) naphthenate (MnPc) as catalyst. 2-Methyl-1,4-naphthoquinone was obtained in 75.6% conversion and with 80.0% selectivity under the latter conditions. A probable mechanism in which MnPc catalyzes the oxidation of 2-MN by hydrogen peroxide in acetic acid is proposed.

Ammoxidation of 3-picoline to nicotinonitrile using silica-supported VCrO catalysts

A series of vanadium–chromium oxide (VCrO) catalysts supported on silica was prepared by wetness impregnation method with different Cr/V molar ratios from 0.2 to 1.0. These catalysts were characterized by XRD, TG, temperature-programmed desorption of ammonia (NH3-TPD), X-ray photoelectron spectra (XPS), and Raman spectroscopy, and their catalytic activity was evaluated in the ammoxidation of 3-picoline (3-PIC) to nicotinonitrile (NN). The results of XRD, TG, Raman, and XPS confirmed that the active components on the silica surface were mainly amorphous V2O5 and CrVO4. The results of NH3-TPD showed that acidity of the catalysts decreased with the increase of Cr/V ratio. Catalytic results revealed that acidity of the catalysts was closely related to the catalytic performance. Low acidity gave low conversion of 3-PIC and high NN selectivity. Furthermore, the conversion of 3-PIC increased with rise in reaction temperature, and the selectivity of NN was slightly influenced by the 3-PIC conversion. Therefore, among the catalysts (Cr/V ratio was 0.2, 0.4, 0.6) tested, Cr/V-0.6 catalyst retained the lowest acidity and exhibited the highest selectivity and yield of NN in the ammoxidation of 3-PIC.

Effect of supports on the structure and activity of vanadium-chromium oxide catalysts for ammoxidation of 3-picoline

Bulk and Nb2O5-, MgF2-, TiO2-, and SiO2-supported vanadium-chromium oxide catalysts were prepared by the incipient wetness impregnation method and investigated for the ammoxidation of 3-picoline to nicotinonitrile at 310–400 °C. The physical and chemical properties of the catalysts were assessed by X-ray diffraction, N2 adsorption-desorption, H2-temperature-programmed reduction, and NH3-temperature-programmed desorption. The surface area of the supports influenced the formation of the active components of the catalysts: high surface area encouraged the formation of monoclinic CrVO4 whereas low surface area favored the formation of orthorhombic CrVO4. The high reducibility of vanadium in the catalyst and the large number of surface active sites resulted in higher 3-picoline conversion efficiencies. The high selectivity was attributed to the low surface acidity of the catalysts. Reaction temperature showed a positive effect on the catalytic performance for it could increase 3-picoline conversion and maintain nicotinonitrile selectivity.

Vanadium-Chromium Oxide: Effective Catalysts for Ammoxidation of 3-Picoline

Bulk vanadium-chromium oxide (VCrO) catalyst was prepared and characterized by N2 adsorption, XRD, NH3-TPD, H2-TPR, and Raman spectroscopy. XRD and Raman results showed that the VCrO catalyst was a kind of VV-CrIII composite oxide mainly consisted of crystalline V2O5 and CrVO4-Ⅲ (orthorhombic). NH3-TPD and H2-TPR results revealed that this catalyst had negligible surface acidity, and was easily reduced due to the formation of CrVO4-Ⅲ. Their catalytic activity was evaluated in the ammoxidation of 3-picoline to nicotinonitrile. Catalytic results showed that the bulk VCrO catalyst was highly active and selective; the nicotinonitrile selectivity and yield was up to 96.1%, 88.2% respectively at atmospheric pressure and 360 °C. The high selectivity was related closely to the low surface acidity of the catalyst.