CHAPTER II – EXPERIMENTAL PART

II.1. Catalysts preparation

This chapter presents the main techniques used for i) the preparation of catalysts and ii) characterization of the prepared samples.

10 catalysts were synthesized, as given in Table 2, summarizing catalysts composition and the methods of preparation used in work. The designation of the catalysts contains:

• support – ZnO-Ga₂O₃ or ­­ZnO-La₂O₃,
• active metals – Co and Cu or Co, Cu and Rh atoms.

CoCuZnGa-2MW and CoCuZnLa-2MW were prepared by double microwave treatment.

Table 2: Catalysts compositions and the method of preparation.

Catalyst NAME	ZnO	Ga2O3	La2O3	Co	Cu	Rh	CM*	MW*
CoCuZnLa-CM	+	-	+	+	+	-	+	-
CoCuRhZnLa-CM	+	-	+	+	+	+	+	-
CoCuZnGa-CM	+	+	-	+	+	-	+	-
CoCuRhZnGa-CM	+	+	-	+	+	+	+	-
CoCuZnGa-MW	+	+	-	+	+	-	-	+
CoCuRhZnGa-MW	+	+	-	+	+	+	-	+
CoCuZnGa-2MW	+	+	-	+	+	-	-	+
CoCuZnLa-MW	+	-	+	+	+	-	-	+
CoCuRhZnLa-MW	+	-	+	+	+	+	-	+
CoCuZnLa-2MW	+	-	+	+	+	-	-	+

(*CM – Calcination aftertreatment , *MW - Microwave method)

Table 3: The promoters and their precursors ( in all cases, water was the solvent ).

Promoter	Compound
Ga2O3	gallium (III) nitrate hexahydrate ( 99.9% wt. Aldrich )
La2O3	lanthanum (III) nitrate hexahydrate ( 99.0% wt. Aldrich )
ZnO	zinc nitrate hexahydrate ( 98.0% wt. Aldrich )
CuO	copper (II) nitrate trihydrate ( 98.0% wt. Aldrich )
Co3O4	cobalt (II) nitrate hexahydrate ( 98.0% wt. Aldrich )
Rh2O3	rhodium (III) chloride trihydrate ( 99.8% wt. Aldrich )

Supports were prepared and synthesized by one of promoters listed in Table 4, thus forming ten different catalysts. The promoters were loaded by incipient wetness and supports were synthesized by urea method [6]. Table 3, presents all chosen promoters and their precursors in all cases solvent was water.

All catalysts were prepared in a similar way. Figure 2. shows all preparation steps used for synthesis. The fallowing was especially taken care of:

- keeping stable temperature and the same time of boiling,

• washing several times by distilled water during filtration,
• precisely crushing the lumps of the prepared materials before calcination and microwave treatment, as well as that obtained by impregnation and drying,
• impregnation with small amounts of the solution of metal precursors at definite intervals of time ( this is necessary for spreading the promoter over the whole volume of support ), and setting the proper microwave conditions.

Figure 2: Catalyst preparation steps

Figure 3 and 4 show calcination and microwave conditions and settings. Calcination was carried out at 350°C for 8 h in air.

For CoCuZnLa-2MW and CoCuZnGa-2MW catalysts microwave treatment was used two times using the same settings, as given in Figure 4.

Figure 3: Calcination conditions.

t [h]	E [W]	T1 [C]
0:03	600	100
0:03	600	100
0:04	600	250
0:10	600	250

Tabele 4: Microwave treatment settings.

( t – time of treatment, E – power of microwave radiation, T1 – temperature inside ractor )