Homogeneous Catalytic Hydrogenation of Bio‐Oil and Related Model Aldehydes with RuCl₂(PPh₃)₃

Abstract

A homogeneous RuCl 2 (PPh 3 ) 3 catalyst was prepared for the hydrogenation of bio-oil to improve its stability and fuel quality. Experiments were first performed on three model aldehydes of acetaldehyde, furfural and vanillin selected to represent the linear aldehydes, oxygen heterocyclic aldehydes and aromatic aldehydes in bio-oil. The results demonstrated the high hydrogenation capability of this homogeneous catalyst under mild conditions (55-90°C, 1.3-3.3 MPa). The highest conversion of the three model aldehydes was over 90 %. Furfural and acetaldehyde were singly converted to furfuryl alcohol and ethanol after hydrogenation, while vanillin was mainly converted to vanillin alcohol, together with a small amount of 2-methoxy-4-methylphenol and 2-methoxyphenol. Further experiments were conducted on a bio-oil fraction extracted by ethyl acetate and on the whole bio-oil at 70°C and 3.3 MPa. Most of the aldehydes were transformed to the corresponding alcohols, and some ketones and compounds with C-C double bond were converted to more stable compounds.

Ruthenium-catalyzed solvent-free conversion of furfural to furfuryl alcohol

“…1). These results are in good agreement with the reported kinetics for the Ru/PPh 3 system, 23 or for reduction of LA. 27 It should be noted that full conversion was achieved under 25 bar of H 2 at 140 C for 50 min (Table 1, entry 11 and ESI Fig.…”

Aqueous-phase hydrogenation and hydroformylation reactions catalyzed by a new water-soluble [rhodium]–thioligand complex

“…Recently furfural has been hydrogenated to furfuryl alcohol in water, under very mild reaction conditions, by using polymer stabilized Ru(0) nanoparticles in the presence of cyclodextrins [39]. To our knowledge, only few examples of hydrogenation of FAL to FOL catalyzed by homogeneous metal complexes are reported in the literature [40][41][42][43] but none of them describes the use of rhodium compounds. First, FAL (V) was hydrogenated in sole water as reaction solvent but after 6 h at 60 • C and 2 MPa of H 2 by using a substrate/Rh molar ratio 500/1 conversion to furfuryl alcohol (VI) was only 38% (run 1, Table 3) (Scheme 2).…”

“…A comparison of Rh(DHTANa) activity with other catalytic systems is rather difficult as most of the homogeneous catalysts used in this reaction are based on ruthenium instead of rhodium and they all are active in organic solvent. For example, Ru(TMHD) 3 (TMHD = 2,2,6,6-tetramethyl-3,5-heptanedione) selectivity reduces FAL to FOL in THF at 80 • C and 2.8 MPa of H 2 but using a 100/1 substrate/Ru molar ratio [40], while RuCl 2 (PPh 3 ) 3 selectively produces FOL in 3 h at 70 • C and 3 MPa of H 2 in the presence of a relevant amount of catalyst (substrate/catalyst molar ratio = 39/1) [41]. Also ruthenium(II)-bis(diimine) complexes are very active and selective in the hydrogenation of FAL to FOL in EtOH at 90-130 • C and 1-5 MPa of hydrogen pressure with the catalyst ranging from 0.4 to 1 mol% [42].…”

Mass production of chemicals from biomass-derived oil by directly atmospheric distillation coupled with co-pyrolysis

“…To date, many techniques, such as catalytic steam reforming11, aqueous phase processing212, have been developed to convert bio-oil and/or its fractions into specific chemicals. Direct processing the raw bio-oil catalytically seemed to be unfavorable because severe coke deposition causes a rapid deactivation of catalysts at temperature over 353 K13. Several methods have been proposed to break the micro-emulsion of raw bio-oil, e.g., adding inorganic salts14 or a sufficient amount of water1516 at first, then the resulting two phases could be further treated to obtain respective target products.…”