Sugar hydrogenation in continuous reactors: From catalyst particles towards structured catalysts

Solid Foam Ru/C Catalysts for Sugar Hydrogenation to Sugar Alcohols─Preparation, Characterization, Activity, and Selectivity

“…In general, the prepared catalyst exhibited good selectivity, activity, and stability similar 49 and even superior to other Ru/C catalysts described in the literature. 47 In that sense, Ru/C foam catalysts represent a promising technology to be applied on the continuous production of sugar alcohols due to their thin catalyst layer that suppresses the internal mass transfer resistance (≪100 μm), 26 as well as the disruptive and tortuous flow path provided by the foam structure that gives excellent mixing properties and lower pressure drop compared to the conventional slurry technology. 23 , 25 …”

“…Structured catalyst materials have features that make them very attractive to be used in chemical reactors, such as a high void fraction, lower pressure drop compared to conventional packed beds filled with pellets, and low flow resistance. , These properties have made structured catalysts extremely successful in some commercial applications, particularly in the case of honeycomb monolith catalysts, used in the cleaning of automotive exhaust gases and oxidation of volatile organic compounds . Thin catalyst layers (≪100 μm) suppress the internal mass transfer resistance in the catalyst pores, which guarantees high catalyst effectiveness factors and operation under conditions of intrinsic kinetics. The application of structured catalysts enables the shift from batch to continuous technology, which is not easy when catalyst slurries are used.…”

Continuous Hydrogenation of Maltose over Raney Ni in a Trickle-Bed Reactor

“…In parallel, liquid flow rate, apart from reaction temperature, tends to be the governing factor in continuous sugar hydrogenation, 11 there- with its impact on maltose evolution was assessed by altering the liquid flow rate from 1.5 to 10 mL/min. As displayed in Figure 4a, the reaction was apparently promoted by lower liquid flow rates, which allowed for more liquid residence time.…”

“…Besides, Najarnezhadmashhadi et al revealed the selective hydrogenation of glucose and binary sugar mixtures (comprising arabinose and galactose) in a continuous multiphase reactor. In another work, an excellent arabitol selectivity of 100% was attained in a tubular reactor for arabinose hydrogenation . Moreover, catalytic transfer hydrogenations of monomeric sugars (e.g., glucose, fructose, mannose, xylose, and arabinose) were developed in fixed-bed reactors, and a broad range of corresponding sugar alcohols were efficiently synthesized in reasonable yields (60–90%). , However, the majority of the aforementioned investigations have been conducted utilizing catalysts with small particle sizes to guarantee stable internal mass transfer and steady liquid flow. , In terms of practical applications, catalyst particles in the millimeter scale are typically favored to obviate heavy clogging tendency and excessive pressure drop. , In addition, continuous hydrogenation of both pentose and hexose has been extensively explored, leaving disaccharides (e.g., maltose and lactose) poorly understood, given their double molecular size of the former.…”

“…8−10 Typically, the supported and sponge metal catalysts (e.g., Ru/C and Raney Ni) have been employed to drive and promote maltose reduction in commercial processes. 11,12 As a representative of non-noble metal catalysts, Raney Ni is earthabundant and inexpensive with high catalytic performance, thereby becoming profitable and widely used on an industrial scale. 13,14 Sulman and co-workers 9 documented maltose hydrogenation into maltitol in perfect selectivity (96−98%) employing a Raney Ni catalyst.…”