Commercial nickel-kieselguhr isopropanol dehydrogenation catalysts: Morphology and catalytic and electronic propertiesCatalysis in Industry

About

Authors
E. A. Guseinova, E. T. Zeinalov, K. Yu. Adzhamov
Year
2015
DOI
10.1134/S207005041503006X
Subject
Catalysis

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ISSN 20700504, Catalysis in Industry, 2015, Vol. 7, No. 3, pp. 227–233. © Pleiades Publishing, Ltd., 2015.

Original Russian Text © E.A. Guseinova, E.T. Zeinalov, K.Yu. Adzhamov, 2015, published in Kataliz v Promyshlennosti. 227

INTRODUCTION

Nickel is the 13th most abundant element in the

Earth’s crust; however, it is of no less significance in the modern world than iron, aluminum, chromium, and other important metals. Periodicals publish doz ens of papers on the chemistry of nickel every month; the content of the publications is fairly diverse, while major attention is devoted to three subjects: alloys, complex compounds, and catalysis [1–6].

Nickel has been used as a catalyst for a more than a century. It was a nickel catalyst discovered by Sabatier in 1897 that was used in the first commercial hydroge nation process [7]. Other known hydrogenation cata lysts were developed later: group VI–VIII metals (including platinum group metals), supported and constituting complex oxide systems, and skeletal metal catalysts. However, nickel still holds a leading position [8–12].

Oxides of transition metals (including nickel) deposited on the surfaces of such inorganic supports as γA12O3, SiO2, TiO2, and aluminosilicates, are effec tive catalysts for a variety of commercial processes: hydrotreating of petroleum fractions, hydrogenation of carbon oxides (methanation), lowtemperature oxidation of carbon monoxide, partial oxidation of methane, and so on. The nature of the metal, the ther mal stability and large specific surface area of the sup ports, and the specific interaction between the metal and the support contribute to the increased activity and stability of nickelbased catalysts and the effi ciency of the conducted processes. Along with devel opment of new nickelcontaining systems, however, much attention has been devoted to studying and improving known commercial catalysts [13–16].

There is no unified theory that explains all of the effects of nickel catalysts. The mechanism and effi ciency of the catalytic action of these catalysts are attributed to a set of such factors as composition, method of preparation, the structure of active sites formed during reaction, and process parameters (tem perature, pressure, composition of the reaction medium) [17, 18]. To understand the action of nickel containing catalysts, we must conduct a detailed anal ysis of the available experimental data.

We therefore studied the morphology and electronic and catalytic properties of commercial nickel–kiesel guhr catalyst in the isopropanol conversion in situ.

EXPERIMENTAL

Commercial nickel–kieselguhr catalyst samples (TU (Technical Specifications) 38.10139689E) man ufactured at the Novokuibyshevsk petrochemical plant were used in this work. The weight fraction of nickel in the samples was no more than 54%, the bulk density

Commercial Nickel–Kieselguhr Isopropanol Dehydrogenation

Catalysts: Morphology and Catalytic and Electronic Properties

E. A. Guseinovaa, E. T. Zeinalova, and K. Yu. Adzhamovb aAzerbaijan State Oil Academy, Research Institute of Geotechnological Problems of Oil, Gas, and Chemistry,

Baku, 1010 Azerbaijan bAzerbaijan State Oil Academy, Baku, 1010 Azerbaijan email: elvira_huseynova@mail.ru, zeto@box.az

Received October 16, 2014

Abstract—Isopropanol conversion over commercial nickel–kieselguhr catalyst is studied. It is found that using this catalyst allows the singlestep production of acetone (in contrast to familiar twostep technologies) with a catalyst not been previously used in this process in a range of moderate temperatures with a feedstock conversion of 97% and a target product yield of 82.4%. Changes that occur in the phase composition, surface structure, and electronic properties of the nickel catalyst under the action of the reaction medium are studied via scanning electron microscopy, thermal analysis, Xray diffraction, and conductometry. It is shown that the conversion of isopropanol into acetone through the dehydrogenation reaction is accompanied by a loosening of the initial homogeneous globular structure of the catalyst to form nickel nanoclusters. Active sites in the alcohol conversion reactions are nickel ions in different states of oxidation and cationic and anionic vacancies.

Keywords: nickel–kieselguhr catalyst, isopropanol dehydrogenation, surface morphology, electronic state, nickel clusters

DOI: 10.1134/S207005041503006X

DOMESTIC CATALYSTS 228

CATALYSIS IN INDUSTRY Vol. 7 No. 3 2015

GUSEINOVA et al. was 1.15 g/cm3, and the average size of the pellets was 4 × 4 mm.

The morphological features of the nickel catalyst samples were studied on a Philips 515 scanning elec tron microscope with a primary electron beam energy of 30 kV.

Our Xray diffraction studies were conducted on a

DRON3M diffractometer using CuK α radiation with a diffractedbeam graphite monochromator. The Ni and NiO contents were determined using a Shimadzu

XRD6000 Xray diffractometer.

Thermal analysis of the nickel–kieselguhr catalyst was conducted on a Derivatograph Q 1050 instrument; the sample was heated in air at a rate of 10 deg/min.

Our conductometric analysis was performed using an E613A teraohmmeter (range of resistance mea surement, 10–1014 Ω; basic error, no more than ±2.5%). The catalyst sample was placed in a measuring chamber that simultaneously acted as a flow catalytic reactor. The sample was compressed to form a rectan gular bar with a known crosssectional area. Platinum probes were inserted in the cross section of the bar. The sample was fixed in a clamp that had two probes attached to platinum probes on a sample’s surface.

The catalytic activity of the samples in the gas phase dehydrogenation of isopropanol (reagent grade,

TU (Technical Specifications) 24210225728579009) was determined using a laboratory flow setup in the temperature range of 150–350°C at an alcohol space velocity of 600 h–1.

The catalyst samples were preactivated in situ in a flow reactor at a temperature of 20–150°C in air at a heating rate of 10°C/min, and at a temperature of 150–300°C in an atmosphere of the reaction mixture.