Abstract
Developing a structured catalyst was performed successfully, and carbon-coated aluminum foam-supported ruthenium catalysts were prepared. Seven different characterization techniques such as scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, inductively coupled plasma-mass spectrometry, carbon monoxide chemisorption, and nitrogen physisorption were applied on the solid catalysts. The carbon-coated foams were checked for their mechanical stability, and the results indicated that the foam catalysts were mechanically stable. The Ru/C foam catalysts were used in a multiphase reactor setup, which had six tubular reactors working in parallel. Continuous hydrogenation of d-glucose, l-arabinose, and a mixture of l-arabinose and d-galactose was studied in the experimental setup. Through investigating different reaction parameters, the temperatures 100–110 °C and the liquid flow rates 0.5–1 mL/min were found to be suitable for catalyst screening and activity testing. The experiments were carried out at 20 bar hydrogen pressure. The continuous hydrogenation experiments were successful, the reproducibility was good, and the foam catalysts were stable. High selectivities of the desired products, sugar alcohols and sugar alcohol mixtures, were obtained.
Highlights
The research in biomass valorization has become important because of shifting from fossil-based industry to the use of renewable raw materials
Hemicelluloses appearing in biomass are rich sources of basic sugars; for example, arabinose and galactose can be obtained from the hemicellulose arabinogalactan, and galactose, glucose, and mannose are obtained by hydrolysis of galactoglucomannan and xylose from the hydrolysis of arabinoglucoronoxylan
To screen the reaction conditions, the temperature was varied between 90 and 120 °C while the hydrogen pressure was kept constant at 20 bar because a previous research has indicated a rather minor effect of hydrogen pressure on the hydrogenation rates of sugars.[2]
Summary
The research in biomass valorization has become important because of shifting from fossil-based industry to the use of renewable raw materials. Sugar alcohols can be prepared by reducing the carbonyl group in the sugar molecule This can be done by the aid of chemical agents or using a hydrogen molecule with heterogeneous and homogeneous catalysts.[2] Using the hydrogen molecule and a solid heterogeneous catalyst, no stoichiometric co-products are formed, and separation of the catalyst, which is needed in the use of homogeneous catalyst, is avoided.[2] In the hydrogenation of sugars to sugar alcohols in an industrial scale, the heterogeneously catalyzed process is preferred, and catalysts based on Ni, Pd, Pt, or Ru are used.[2−4] The application of heterogeneous catalysis and molecular hydrogen in the reduction of sugars follows completely the principle of green chemistry and green process technology
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