Ru-Sn/AC for the Aqueous-Phase Reduction of Succinic Acid to 1,4-Butanediol under Continuous Process Conditions

Abstract

Succinic acid is a biomass-derived platform chemical that can be catalytically converted in the aqueous phase to 1,4-butanediol (BDO), a prevalent building block used in the polymer and chemical industries. Despite significant interest, limited work has been reported regarding sustained catalyst performance and stability under continuous aqueous-phase process conditions. As such, this work examines Ru-Sn on activated carbon (AC) for the aqueous-phase conversion of succinic acid to BDO under batch and flow reactor conditions. Initially, powder Ru-Sn catalysts were screened to determine the most effective bimetallic ratio and provide a comparison to other monometallic (Pd, Pt, Ru) and bimetallic (Pt-Sn, Pd-Re) catalysts. Batch reactor tests determined that a ∼1:1 metal weight ratio of Ru to Sn was effective for producing BDO in high yields, with complete conversion resulting in 82% molar yield. Characterization of the fresh Ru-Sn catalyst suggests that the sequential loading method results in Ru sites that are colocated and surface-enriched with Sn. Postbatch reaction characterization confirmed stable Ru-Sn material properties; however, upon a transition to continuous conditions, significant Ru-Sn/AC deactivation occurred due to stainless steel leaching of Ni that resulted in Ru-Sn metal crystallite restructuring to form discrete Ni-Sn sites. Computational modeling confirmed favorable energetics for Ru-Sn segregation and Ni-Sn formation at submonolayer Sn incorporation. To address stainless steel leaching, reactor walls were treated with an inert silica coating by chemical vapor deposition. With leaching reduced, stable Ru-Sn/AC performance was observed that resulted in a molar yield of 71% BDO and 15% tetrahydrofuran for 96 h of time on stream. Postreaction catalyst characterization confirmed low levels of Ni and Cr deposition, although early-stage islanding of Ni-Sn will likely be problematic for industrially relevant time scales (i.e., thousands of hours). Overall, these results (i) demonstrate the performance of Ru-Sn/AC for aqueous phase succinic acid reduction, (ii) provide insight into the Ru-Sn bimetallic structure and deactivation in the presence of leached Ni, and (iii) underscore the importance of compatible reactor metallurgy and durable catalysts.

Nanostructured Metal Catalysts for Selective Hydrogenation and Oxidation of Cellulosic Biomass to Chemicals

“…Vardon et al . found that Ru catalysts show outstanding performance with respect to both activity and product selectivity . Bimetallic RuRe catalysts supported on mesoporous carbon were prepared by a single‐step surfactant‐templating method followed by subsequent incipient wetness impregnation [Figure (d), (entry#8 in Table )] .…”

“…Sn plays a similar role in promoting catalytic selectivity towards 1,4‐BDO over Pd/C catalysts. Vardon and colleagues characterized PdRe and PdSn catalysts supported on activated carbon . XPS spectroscopy reveals that Sn 2+ may provide Lewis acidity through unsaturated Sn 4+ formation, while surface hydroxyl groups on Sn 4+ show strong Bronsted acidity.…”

Combining Reclaimed PET with Bio-based Monomers Enables Plastics Upcycling

“…The diols that can be implemented with no adverse effect on properties are not limited to ethylene glycol and could include renewably sourced diols, such as butanediol. The source of the diols, like butanediol, can be directly from fermentation or from the catalytic upgrading of diacids [92][93][94] and sugars. 95,96 Even though no stark differences were observed with butanediol as the glycolysis agent, more rigid diols such as isosorbide 97 may impart further property modifications.…”

Bio-Based Chemicals from Renewable Biomass for Integrated Biorefineries

“…Re nanocatalyst supported on Cu-containing mesoporous carbon (Re/XCu-MC) was tested for the hydrogenation of succinic acid to 1,4-butanediol [224]. Vardon et al [225] reported the use of Ruthenium-tin based catalysts supported on activated carbon for the reduction of succinic acid (aqueous-phase) to BDO. GBL is an important building block molecule for use in agrichemicals, petrochemicals, dyes, textile processing, and epoxides [226].…”