An Integrated Process for D-Sorbitol Production over NiO/TiO₂ Supported Ru Nanocatalyst: A Greener Approach

The catalytic transformation of D-glucose towards D-sorbitol is a well-established process in the biorefinery industry. Normally, this batch-wise hydrogenation over metallic catalysts suffers from several troubles such as low yielding and facile catalyst deactivation. To address these challenges, we, hereby fabricated 5NiO/TiO₂-supported Ru nanocatalysts (Ru-5NiO/TiO₂, 1.0 and 5.0 wt% Ru) and examined their efficacy in the continuous-flow reduction of D-glucose aqueous solution (20 wt%) to produce D-sorbitol for the first time. In this study, D-glucose conversion and D-sorbitol yield were represented as a function of residence time, where the feeding rate of D-glucose was systematically controlled to maximize the outcome of D-sorbitol. Remarkably, D-glucose was fully converted to 99.0% selectivity of D-sorbitol under optimized reaction conditions (100 °C, 8 MPa H₂ with a flow rate of 100 L h⁻¹). The experimental results showed that the mean activity and specific rate of 1.0 wt% Ru-5NiO/TiO₂ were achieved as 731.3 mmol h^{− 1} g^{− 1} and 1030.7 mmol h⁻¹ g⁻¹, respectively, which surpassed those of monometallic Ru-based catalysts (1.0 wt% Ru/TiO₂, 1.0 wt% Ru/SiO_2, and 1.6 wt% Ru/C). Moreover, the stability of 1.0 wt% Ru-5NiO/TiO₂ nanocatalyst was sustained for long-term operation (> 360 h) and no leaching of ruthenium was highly acknowledged. Graphical Abstract: [Figure not available: see fulltext.]