**4. Results**

resistance in comparison with other existing commercial supports. They also combine dual hydrophilic/hydrophobic, inorganic/organic surface properties; this is the main property

The process of preparation of the composite supports is described in **Figure 2**. It comprises

**4.** Polymerization of the organic phase by means of the thermal activation of the polymeri-

In the preparation of the composite precursors the following polymeric phase precursors were used: bisphenol A glycerolate dimethacrylate (BGMA), triethylene glycol dimethacrylate (TEGDMA), and diurethane dimethacrylate (UDMA). The thermally activated polymerization starter used was benzoyl peroxide (BPO). **Figure 3** shows the chemical structure of the monomers and the polymerization starter used during the preparation of the UTAl and

Two different composites, that is, UTAl and BTAl used in this work were made by mixing γalumina powder, two monomers, and BPO. The main difference between composites supports was the type of monomers used; UDMA and TEGMA were used for composite called UTAl, and BGMA and triethylene glycol dimethacrylate(TEGMA) were used for composite called

UTAl and BTAl were prepared as describe by Badano et al. [31], monomers joined BPO were intimately mixed with 45 wt% γ-alumina. Then, mixture was desgassed and extruded into a cylinder of 2 mm diameter. Polymerization of the paste was carried on a stove at 393 K for 1

Gamma alumina (CK-300, Ketjen), activated carbon (NORIT RX3 Extra and CNR), and composite support, BTAl and UTAl were used as supports to prepared metal catalyst. Platinum was loaded with PtCl2 and H2PtCl6H2O by incipient wetness technique. After impregnation, catalysts were dried at 393 K in an oven for 24 h and were maintained in desiccator for further

**1.** Weighing of monomers, polimerization starters, and inorganic material.

**2.** Mixing of the monomers, polimerization starters, and inorganic material.

**5.** Making the support ready for use in the preparation of the metal catalyst.

BTAl. The alumina used was γ-alumina with a particle size of 0.074 mm.

h. The final composite were pellets of 2 mm diameter and 2–3 mm long.

use. The catalysts were reduced in a H2 flow at 503 K for 1 h after catalytic test.

**3.** Shaping of the support by means of extrusion, pelletizing, etc.

behind the preparation of egg-shell catalysts.

186 New Advances in Hydrogenation Processes - Fundamentals and Applications

the following steps:

zation starter.

BTAl supports.

**2.2. Catalysts preparation**

#### **4.1. Catalysts characterization**

Values of the axial and radial mechanical resistance of the pellets were obtained in an universal rehearsals equipment. A compression rate of 1 mm min–1 was used. The attrition resistance was assessed by means of the method depicted in the ASTM D 4058 norm.

The specific surface area (SBET) values were obtained from nitrogen physical adsorptiondesorption isotherms at 77 K. In order to get a surface free of water and adsorbed compounds, the samples were degassed overnight at 523 K in vacuum (<10–4 Pa) before adsorption.

The palladium and platinum content of the catalysts was obtained by digesting the sample and then analyzing the liquors in ICP equipment. Hydrogen chemisorption measurements were performed in a pulse apparatus at atmospheric pressure. Before the test the samples were reduced in a gas mixture containing 5% v/v H2/Ar for 1 h and degassed in an Ar flow at the same temperature of reduction for 3 h. After that, the samples were cooled in an argon flow, and the chemisorption test was done by injecting hydrogen pulses to the flowing stream until the samples became saturated.

X-ray photoelectron spectroscopy (XPS) was done over the reduced catalysts with a VG-MicrotechMultilab equipment.

Samples were analyzed using scanning electron microscopy (SEM) equipped with an energy dispersion system (EDAX) that enablesto analyze elementary chemical with an X-ray microbeam. This technique is known as electron probe microanalyzer (EPMA) and it was allowed to elucidate metal distribution and create elemental mappings. Before measure, catalyst pellets were coated with thin carbon film in order to avoid influence of charge effect during the SEM operation. The scanning speed was 0.02 mm min–1 and the acceleration voltage of electron beam was 20kV.

The thickness of the metal surface shell was also determined optically with the aid of micrographs of the cross section of the catalysts. Micrographs were obtained with a microscope equipped with a color video printer. To analyze the samples, this technique required to be encapsulated with a thermoplastic resin and then polished with sandpaper. Sanding encapsulated samples were done with finer paper (down 500 grit) until exposing the cross section of catalyst particles. The finest paper used was 2500 grit.

The XRD measurements were performed in a diffractometer with CuKα radiation filtered with Ni. Spectra were scanned at a rate of 0.25 min–1 in range between 25 and 80°. Catalyst required different preparation before analyzing. For alumina and carbon samples, material was grinded and reduced in hydrogen flow. In the case of composites, a slab of 1 cm2 of area was impregnated with Pt or Pd, then was grinded and reduced as previous samples thermo gravimetric analysis (TGA) traces were also obtained. These traces show the dependence of the thermal weight loss of a sample as a function of the temperature. In the experiments catalyst samples (about 10 mg) were heated in an air flow of 40 mL min–1 from room temperature up to 1173 K at a heating rate of 5 K min–1.

To measure the acidity of the supports, the reaction of dehydration of 1,4-butanediol to tetrahydrofurane (THF) was followed.
