Rutile TiO2 a desirable support for Ni catalyst in the synthesis of γ-valerolactone: Influence of titania crystal phase on the product distribution

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Rutile TiO2 was identified as a suitable support for nickel than the anatase form in the selective conversion of levulinic acid (LA) to γ-valerolactone (GVL) with a 20-fold rate enhancement. TEM-HAADF results revealed a high degree of Ni encapsulation by titania species on the anatase that resulted in lower LA conversion with a high selectivity of angelica lactones. While nickel plateaus with protruding particles partially covered by TiOx overlayers on a rutile surface was the reason for the higher rate of GVL. CO chemisorption results indicated a lower uptake on 10 wt%Ni/TiO2-anatase than on the 10 wt%Ni/TiO2-rutile catalyst and a high rate of hydrogen spillover was manifested by rutile TiO2 supported Ni catalyst than its counterpart anatase. Variations in the crystal phase of TiO2 and their interaction with nickel could substantially influence the GVL formation. High intrinsic activity of 10 wt%Ni/TiO2-800(R) was explained and discussed using surface and bulk characteristics of the catalysts.