**5.1. Catalyst characterizations**

**Table 1** shows the results of the tests of mechanical properties, i.e., resistance to diametrical compression (SD), resistance to longitudinal compression (SL), and attrition loss obtained for the composite supports UTAl, BTAl and for the commercial supports of alumina and carbon. It can be seen that the composite supports have better mechanical properties than the commercial supports. This is especially important when γ-alumina is taken as a reference.


**Table 1.** Supports mechanical properties.

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

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

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

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

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

To measure the acidity of the supports, the reaction of dehydration of 1,4-butanediol to

**Table 1** shows the results of the tests of mechanical properties, i.e., resistance to diametrical compression (SD), resistance to longitudinal compression (SL), and attrition loss obtained for

of catalyst particles. The finest paper used was 2500 grit.

188 New Advances in Hydrogenation Processes - Fundamentals and Applications

the samples became saturated.

MicrotechMultilab equipment.

at a heating rate of 5 K min–1.

**5.1. Catalyst characterizations**

**5. Results**

tetrahydrofurane (THF) was followed.

beam was 20kV.

**Table 2** contains the results of metal concentration, metal dispersion, specific surface area, binding energy of Pd3d5/2 and Pt 4d5/2 and Cl/metal atomic ratios obtained by XPS, and metal penetration depth, as determined by different techniques.


**Table 2.** Metal catalyst loadings, dispersion values, XPS results, and metal penetration to EMPA.

Regarding the Pd surface species, except for the 0.3PdCNR and 1PdRX catalysts, only two different species were detected. The PdUTAl catalysts had a peak with a binding energy (BE) of 335.0 eV, attributed to Pd0 , while the PdBTAl catalysts had peaks at 335.6 (0.3PdBTAl) and 335.2 eV (1PdBTAl), and attributed to Pdδ+ electrodeficient Pd species [33]. All catalysts had a second signal with BE values between 336.3 and 337.0 eV that would correspond to Pdη+ species with δ+ <η+ <2.This could possibly be related to the incomplete removal of chlorine ligands of the metal salt during the thermal treatment, leading to the presence of surface nonreduced Pd oxychloride species [34]. The same behavior can be seen for the Pt catalysts. In this case the 4d5/2 signals at 313.5 and 315.5 eV would be attributed to Ptη+, oxychlorided platinum species [34].

In **Figure 4** optical microscopies of the catalysts 0.3PdBTAl, 0.3PdUTAl, 1PdBTAl, and 1PdU-TAl are shown. In this figure it can be observed that the pellets images form before the catalytic tests. In the cross-sectional images of these catalysts it can be observed in the clearer region, the presence of support on the inside of the pellet, and on the outer surface, the darker region, the metal is located. Identical behavior can be seen in **Figure 5** where the microscopies for 1PtUTAl and 1PtBTAl catalysts were obtained.

**Figure 4.** Optical micrographs images for transversal section of catalysts: (a)–(c): 0.3PdBTAl; (d)–(f): 0.3PdUTAl; (g)–(i): 1PdBTAl; (j)–(m): 1PdUTAl.

**Figure 6** presents SEM images obtained for the catalysts 0.3PdBTAl, 0.3UTAl, 1PdBTAl, and 1PdUTAl. In the SEM images, **Figure 6(a)** and **(b)**, the topography of the surface catalysts 1PdBTAl and 1PdUTAl can be seen. Images from **Figure 6(c)**–**(h)** were obtained using the detector in backscattering mode in order to see the structural composition of the composite catalysts. From such images it is possible to see Pd particles as darker region on outer surface of the support. In the center of the pellet light color spots surrounded by a structure of gray colorcan be seen, which corresponds to γ-alumina particles gird for a continuous network of polymeric phase of the composite catalyst.

Regarding the Pd surface species, except for the 0.3PdCNR and 1PdRX catalysts, only two different species were detected. The PdUTAl catalysts had a peak with a binding energy (BE)

335.2 eV (1PdBTAl), and attributed to Pdδ+ electrodeficient Pd species [33]. All catalysts had a second signal with BE values between 336.3 and 337.0 eV that would correspond to Pdη+ species

the metal salt during the thermal treatment, leading to the presence of surface nonreduced Pd oxychloride species [34]. The same behavior can be seen for the Pt catalysts. In this case the 4d5/2 signals at 313.5 and 315.5 eV would be attributed to Ptη+, oxychlorided platinum species

In **Figure 4** optical microscopies of the catalysts 0.3PdBTAl, 0.3PdUTAl, 1PdBTAl, and 1PdU-TAl are shown. In this figure it can be observed that the pellets images form before the catalytic tests. In the cross-sectional images of these catalysts it can be observed in the clearer region, the presence of support on the inside of the pellet, and on the outer surface, the darker region, the metal is located. Identical behavior can be seen in **Figure 5** where the microscopies for 1PtUTAl

**Figure 4.** Optical micrographs images for transversal section of catalysts: (a)–(c): 0.3PdBTAl; (d)–(f): 0.3PdUTAl; (g)–(i):

**Figure 6** presents SEM images obtained for the catalysts 0.3PdBTAl, 0.3UTAl, 1PdBTAl, and 1PdUTAl. In the SEM images, **Figure 6(a)** and **(b)**, the topography of the surface catalysts 1PdBTAl and 1PdUTAl can be seen. Images from **Figure 6(c)**–**(h)** were obtained using the detector in backscattering mode in order to see the structural composition of the composite catalysts. From such images it is possible to see Pd particles as darker region on outer surface

<2.This could possibly be related to the incomplete removal of chlorine ligands of

, while the PdBTAl catalysts had peaks at 335.6 (0.3PdBTAl) and

of 335.0 eV, attributed to Pd0

190 New Advances in Hydrogenation Processes - Fundamentals and Applications

and 1PtBTAl catalysts were obtained.

1PdBTAl; (j)–(m): 1PdUTAl.

with δ+

[34].

<η+

The egg-shell profile of the catalysts was confirmed by EPMA obtained by the penetration of Pd on the support of 60 and 90μm for UTAl and BTAl supports, respectively.

**Figure 5.** Optical micrograph images of the cross section of the pelletized catalysts: 1PtBTAl (a and b); 1PtUTAl (c and d).

**Figure 6.** Catalysts transversal section SEM images. (a), (c), and (e) 1PdUTAl; (b), (d), and (f) 1PdBTAl; (g) 0.3PdUTAl, (f) 0.3BTAl. From Ref. [32].

**Figure 7** shows the X-ray diffractograms of the composite supports, γ-alumina, Pt/composite, and Pd/composite catalysts. Comparing the results of gamma alumina with those of the composite supports, a close similarity can be seen. This is due to the fact that the inorganic phase used for the preparation of the composite supports is also γ-alumina and that the polymeric phase is amorphous. For all catalysts a peak at 20–39.9° would correspond to the reflections of the (111) planes of Pd0 and Pt0 .

**Figure 7.** X-ray diffractograms of the composite BTAl (a) and UTAl (b) supports and the corresponding Pd and Pt catalysts.

**Figure 8** contains the TGA results of the UTAl and BTAl composites, and 1 wt% Pd and Pt composite catalysts.

**Figure 8.** TGA traces of the composite supports and the corresponding Pt and Pd catalysts using air as carrier gas.

Inspection of the TGA traces indicates that for both composites the presence of the metal enhances the rate of decomposition of the organic phase.This effect is more important in the case of Pt. This behavior correlates with the nature of these metals that act as combustion catalysts in the presence of oxygen.

In order to assess the acidity of the support the reaction test of dehydration of 1,4-butanodiol to THF was used. The results of the test are shown in **Figure 9**. As expected the catalyst with the highest activity is the Amberlyst 15 resin. γ-Al2O3 alumina has a catalytic activity lower than the resin but higher than other supports. The composite and the Norit RX3 carbon supports display alcohol conversion values much lower than those of the resin or the alumina. There are only slight differences in activity between the activated carbon and UTAl composite while BTAl displays the lowest values of conversion as a function of time. From these results it could be inferred that the acid resin Amberlyst 15 has the highest concentration of acid sites and the BTAl composite the lowest.

**Figure 9.** Acidity test. Dehydration of 1,4-butanediol to THF. Reaction conditions: 1,4-dioxane solvent, *C*0 1,4-butanediol = 1 M, 0.1 MPa, 473 K, *W*cat = 0.2 g.
