tillation. Using this phase transfer technique Al 2 O 3 powder A phase transfer technique was employed to prepare nanosize with 10-nm particles was prepared (7). By the same method, Cu-ZnO/Al 2 O 3 catalyst particles. Due to adsorption of metal sur-nanosize Co 2 O 3 was prepared by Shi et al. (8). However, factants, sol particles are transferred from the aqueous phase to the surfactant DBS involves the sulfonic acid group, which the organic phase. Consequently, the agglomeration of particles is harmful for some materials and cannot be burned at lower can be reduced. Cu-ZnO/Al 2 O 3 catalyst of about 5-mm particle calcination temperatures. As anion surfactants are not suitsize was prepared by this technique. It was found that organic able for the preparation of multicomponent nanosize partisolvents with aliphatic chains were more effective than aromatic cles because of different precipitation conditions (9, 10), solvents. A solvent-to-salt ratio of about 2200 ml solvent per mole cation surfactants were studied; nanosize Cu-ZnO/Al 2 O 3
of salt appeared to be ideal. The preparation procedure comprises preparation of aqueous sol and metal surfactant solution in organic catalyst was prepared in our previous studies (9, 10). Howsolvent, mixing, stirring, and so on. The mol fraction of metal ever, the washing operation in the preparation process was surfactant versus total metal was approximately 0.3. The concendifficult because of the large HLB value (olcophylic and tration of salt and precipitant was 0.2-0.4 mol/L. ᭧ 1996 Academic hydrophilic balance value) of cation surfactants. As a result, Press, Inc. cation surfactants may be lost in the washing operation be-Key Words: nanosize; Cu-ZnO/Al 2 O 3 ; catalyst; preparation; cause of dissolution in water, which lowers the stability of phase transfer; metal surfactant. sol particles. The loss of surfactants can be avoided if washing is eliminated. For instance, when ammonia is used as precipitant for metal nitrates, the by-product is NH 4 NO 3 , EXPERIMENTAL was used to transfer Al(OH) 3 sol particles from the aqueous phase to the organic phase and water was removed by dis-Preparation