Promotion of the Ni/γ-Al2O3 catalyst for the hydrogenation of naphthalene by silica coating

The γ-Al2O3 was coated with silica through the chemical liquid deposition method with tetraethyl orthosilicate as a deposition agent. The effects of the silica coating on the reduction behaviors of nickel species, acidity and hydrogenation activities of the Ni/γ-Al2O3 catalysts were studied. The results show that the silica coating has a great promotion on the reduction behaviors of nickel species as the catalyst was activated under air atmosphere but little influence under H2. The acidity of the catalyst was improved by the silica coating. Therefore, the activities of Ni/γ-Al2O3 catalysts for the hydrogenation of naphthalene are promoted by the silica coating, but the promotion effects on the catalysts activated under air and H2 atmosphere are difference. The promotion on the catalyst activated under air is due to the enhancement of its reduction degree and acidity, but only acidity for the catalyst activated under H2. As a result, the activity is improved about 230% for the catalyst activated under air but only about 110% for the catalyst activated under H2.