*2.1.2. Metals supported over inorganic materials*

**1.** Metal supported particles with controlled size and distribution can be synthesized.

**2.** Chemical performance advantages of the catalyst can be improved because of an intimate interaction between the metal particle and the different functional groups of the polymer. The used polymers can be either soluble or insoluble in the reaction medium. The focus here is on insoluble polymers, involving a bundle of physically and/or chemically cross-

Pd/composite catalysts with egg-shell structure can be easily obtained because the hydrophillic-hydrophobic action of the support regulates the penetration of the metal (active phase). The good mechanical properties of these materials give them an advantage over traditional

To evaluate the properties of the metal/composite egg-shell catalysts, the test reactions of selective hydrogenation of styrene to ethylbenzene, 1-heptyne to 1-heptene, 3-hexyne to 3 hexene, 2,3-butanodione to 3-hydroxy-2-butanone and ethyl piruvate to (R)-ethyl lactate are

A brief summary is presented about the preparation and use of different organic-inorganic supports and catalysts. The materials are divided into three classes and each one is studied

The different strategies of synthesis of these metal/polymer catalysts are shown in **Figure 1**.

For the preparation of these catalysts, the organic support is commonly prepared from acrylic or vinylic monomers. Polymerization cross-linking is adjusted by the use of additives, with a minimum value for preventing the dissolution in the solvents used in the subsequent reactions. Metals with catalytic properties are placed over these supports. Oxidized metal precursors are reduced to the metal state with the help of reducing chemical agents in solution or by the use of molecular hydrogen. For these kind of supports styrene and divinylbenzene N,N-dimethylacrylamide, 2-acrylamido-2-methylpropane sulfonic acid, methacrylic acid , 4-vinylpyridine, glycidyl methacrylate ethylene glycol dimethacrylate, etc. are the monomers of choice.

Particle size may range from a few nanometers to hundreds of nanometers.

linked polymer chains in which the metal nanoparticles are embedded.

supports where their use is intended for packed bed or basket reactors.

184 New Advances in Hydrogenation Processes - Fundamentals and Applications

**2. Preparation of composite supports and catalysts**

**C.** Metals supported over new inorganic-organic composite materials

**2.1. Preparation of composite supports**

**A.** Metals supported over functional polymers

**B.** Metals supported over inorganic materials

*2.1.1. Metals supported over functional polymers*

used.

separately:

Here a functionalized polymer is used. This is generally soluble or slightly soluble in organic or aqueous solvents. Organometallic compounds or metal particles are grafted over the polymer matrix. These compounds act as metal active sites. Once the metal is firmly supported on the polymer surface, particles of this polymer are deposited over inorganic supports.

### *2.1.3. Metals supported over new inorganic-organic composite materials*

Lately our research group developed new composite organic-inorganic supports in which the organic phase is made out of polymers of functionality 4. In these composites the polymeric phase has a high cross-linking degree and the inorganic phase is supplied by particulated metal oxides. The method of preparation of these composite supports is described in **Figure 2**.

**Figure 2.** Scheme of preparation of a composite support.

Structured materials in the form of rings, spheres, tablets, or pellets can be prepared with this preparation technique. Metals can be deposited on them, preferentially with an egg-shell structure of small thickness of the active phase. These materials have improved mechanical resistance in comparison with other existing commercial supports. They also combine dual hydrophilic/hydrophobic, inorganic/organic surface properties; this is the main property behind the preparation of egg-shell catalysts.

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


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 BTAl supports.

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

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