Influence of rare earths on the properties and catalytic activity of the Y
The Y zeolites containing calcium and rare earth polivalent cations, RE,Ca/NaY (RE = La, Ce, Nd, Eu, Gd), were prepared by ion exchange, refluxing the NaY zeolite (Si/Al = 2,4) with calcium chloride and rare earth chloride solutions, followed by thermal treatment under nitrogen flow. The trivalent hydrated rare earth ions undergo hydrolysis, forming [RE.OH]2+ cation hydroxyls and protons H+, which react with oxygen in the lattice, generating strong acid sites. The rare earth elements influence the total acidity, strength and distribution of the active sites in the zeolite. The unit cell chemical compositions of the samples were determined by Inductively Coupled Plasma / Atomic Emission spectroscopy (ICP/AES). The crystallinity was confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray diffraction. The europium microsimetry in the Eu,Ca/NaY zeolite was investigated by emission electronic spectroscopy in the visible region, under ultra-violet excitation (396 nm). The acid properties of the RE,Ca/NaY samples were studied by Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC), using n-butilamine as molecular probe. From TG curves, the total acidity was calculated, whereas the relative acid strength was determinated by DSC curves, using the Borchardt-Daniels kinetic model. The nature of Brönsted and Lewis acid sites was investigated by FT-IR, in the 1700 - 1300 cm-1 region, using pyridine as molecular probe. The catalytic activity and selectivity of the samples were evaluated on the alkylation of benzene with 1-dodecene model reaction, to form linear alkylbenzenes, in liquid phase, at 80°C using a bath reactor. The reactant conversion, extent of isomerization and product distribution were monitored by Gas Chromatography and Mass Spectrometry techniques (GC-MS).
Advisor:Lea Barbieri Zinner; Eduardo Falabella Sousa Aguiar; Dilson Cardoso; Remolo Ciola; Martin Schmal; Lea Barbieri Zinner
School:Universidade de São Paulo
Source Type:Master's Thesis
Date of Publication:11/09/1992