Sibao Liu

One-pot selective conversion of furfural into 1,5-pentanediol over a Pd-added Ir–ReOx/SiO2 bifunctional catalyst

One-pot selective conversion of furfural into 1,5-pentanediol (1,5-PeD) was carried out over Pd-added Ir–ReOx/SiO2catalysts through two-step reaction temperatures. The Pd(0.66 wt%)–Ir–ReOx/SiO2catalyst showed the best performance in the production of 1,5-PeD from furfural. The maximum yield of 1,5-PeD was 71.4%. The furfural conversion and yield of 1,5-PeD was almost maintained during four repeated tests when the catalyst was calcined again. The characterization results from TPR, XRD, XANES, EXAFS and FT-IR of adsorbed CO indicated that Pd–Ir–ReOx/SiO2catalysts consisted of ReOx-modified Pd metal particles and ReOx-modified Ir metal particles. The lower-temperature reaction step was very crucial for the total hydrogenation of furfural into a tetrahydrofurfuryl alcohol intermediate, which was converted into 1,5-PeD by hydrogenolysis during the high temperature step over the ReOx-modified Ir metal particles.

Catalytic Total Hydrodeoxygenation of Biomass‐Derived Polyfunctionalized Substrates to Alkanes

The total hydrodeoxygenation of carbohydrate-derived molecules to alkanes, a key reaction in the production of biofuel, was reviewed from the aspect of catalysis. Noble metals (or Ni) and acid are the main components of the catalysts, and group 6 or 7 metals such as Re are sometimes added as modifiers of the noble metal. The main reaction route is acid-catalyzed dehydration plus metal-catalyzed hydrogenation, and in some systems metal-catalyzed direct CO dissociation is involved. The appropriate active metal, acid strength, and reaction conditions depend strongly on the reactivity of the substrate. Reactions that use Pt or Pd catalysts supported on Nb-based acids or relatively weak acids are suitable for furanic substrates. Carbohydrates themselves and sugar alcohols undergo CC dissociation easily. The systems that use metal-catalyzed direct CO dissociations can give a higher yield of the corresponding alkane from carbohydrates and sugar alcohols.

Performance and characterization of rhenium-modified Rh–Ir alloy catalyst for one-pot conversion of furfural into 1,5-pentanediol

One-pot selective conversion of highly concentrated furfural to 1,5-pentanediol (1,5-PeD) was carried out over Rh-added Ir–ReOx/SiO2 catalysts through two-step reaction temperatures. Over the optimized catalyst, Rh(0.66 wt%)–Ir–ReOx/SiO2, the maximum yield of 1,5-PeD was 71.1% from highly concentrated furfural (50 wt%) and 78.2% from diluted furfural (10 wt%). These values were higher than those obtained with Ir–ReOx/SiO2 or Pd–Ir–ReOx/SiO2 catalysts. Rh–Ir–ReOx/SiO2 showed much higher activity in the hydrogenation of furfural to tetrahydrofurfuryl alcohol intermediate in the low temperature step than Ir–ReOx/SiO2, although the hydrogenation activity was lower than that of Pd–Ir–ReOx/SiO2. A long reaction time in the low temperature step is necessary to obtain a good 1,5-PeD yield over Rh–Ir–ReOx/SiO2 in two-step reaction of furfural. The hydrogenolysis activity of Rh–Ir–ReOx/SiO2 for tetrahydrofurfuryl alcohol to 1,5-PeD in the high temperature step was higher than that of Pd–Ir–ReOx/SiO2 and was comparable to that of Ir–ReOx/SiO2. The characterization results of TPR, XRD, XANES, EXAFS, STEM-EDX and FT-IR of adsorbed CO indicated that Rh–Ir–ReOx/SiO2 catalysts showed the structure of Ir–Rh alloy particles partially covered with ReOx species. The hydrogenation activity of Rh–Ir–ReOx/SiO2 for the furan ring was higher than those of the mixture of Rh–Ir/SiO2 and Ir–ReOx/SiO2 or the mixture of Rh–ReOx/SiO2 and Ir–ReOx/SiO2. Both Ir–Rh alloy formation and ReOx modification of alloy particles are essential for the high hydrogenation activity.

Production of Renewable Hexanols from Mechanocatalytically Depolymerized Cellulose by Using Ir‐ReOx/SiO2 catalyst

Hexanols were produced in high yield by conversion of cellulose over Ir-ReOx /SiO2 (molar ratio Re/Ir=2) catalyst in biphasic reaction system (n-decane+H2 O). The cellulose was depolymerized by mechanocatalysis with the aid of H2 SO4 . The influence of solvent amount, reaction temperature and hydrogen pressure was systematically investigated and the highest yield of hexanols reached 60 % under the conditions of n-decane/water ∼2 (v/v), 413 K, 10 MPa H2 for 24 h. Mechanocatalytic depolymerization of cellulose with the aid of H2 SO4 or HCl and the use of sufficient n-decane were very crucial for the production of hexanols. H2 SO4 not only catalyzed cellulose to water-soluble oligosaccharides but also promoted the hydrogenolysis activity of Ir-ReOx /SiO2 catalyst. The role of n-decane was to extract hexanols and to suppress over-hydrogenolysis of hexanols to n-hexane.

Selective transformation of hemicellulose (xylan) into n-pentane, pentanols or xylitol over a rhenium-modified iridium catalyst combined with acids

n-Pentane, pentanols and xylitol can be separately produced from hemicellulose (xylan) over an Ir–ReOx/SiO2 catalyst combined with acids by simply adjusting the reaction conditions. n-Pentane can be produced by using Ir–ReOx/SiO2 combined with HZSM-5 + H2SO4 in a biphasic solvent system (4 ml n-dodecane + 9.5 ml H2O) with a reaction temperature of 463 K for 24 h. Pentanols can be produced by using Ir–ReOx/SiO2 combined with H2SO4 in a biphasic solvent system (20 ml n-dodecane + 9.5 ml H2O) with a reaction temperature of 413 K for 144 h. Xylitol can be produced by using Ir–ReOx/SiO2 combined with H2SO4 in the aqueous phase with a reaction temperature of 413 K for 12 h. The highest yields of n-pentane, pentanols and xylitol could reach 70%, 32% and 79%, respectively. The reuse of the catalyst was feasible when the catalyst was regenerated by calcination at 773 K for 3 h. The calcination step is for removing the humins which were formed at the hydrolysis + hydrogenation step during conversion of xylan. The humins covered the active site of Ir–ReOx/SiO2 and HZSM-5, and they deactivated Ir–ReOx/SiO2 in C–O hydrogenolysis performance in part. The mineral ions (such as Na+ and K+) in xylan decreased the hydrogenolysis activity of Ir–ReOx/SiO2 significantly since the mineral ions can make the number of hydroxorhenium sites (Re–OH) smaller, which is the active site of Ir–ReOx/SiO2 for C–O hydrogenolysis, by ion exchange. The appropriate amount of H2SO4 addition is very crucial for the production of target products in high yield. The addition of H2SO4 not only neutralized the residual alkali of xylan after being isolated from lignocellulose to make the reaction solution acidic, but also improved the C–O hydrogenolysis activity of Ir–ReOx/SiO2 through increasing the number of hydroxorhenium sites by competitive adsorption on the Re site with mineral ions.

One-pot catalytic selective synthesis of 1,4-butanediol from 1,4-anhydroerythritol and hydrogen

A physical mixture of ReOx–Au/CeO2 and carbon-supported rhenium catalysts effectively converted 1,4-anhydroerythritol to 1,4-butanediol with H2 as a reductant. The combination of these two catalysts in a one-pot reaction dramatically increased the selectivity of 1,4-butanediol as well as the conversion of 1,4-anhydroerythritol. The yield of 1,4-butanediol reached ∼90%, which is the highest yield from erythritol and 1,4-anhydroerythritol so far, furthermore, at a relatively low reaction temperature of 413 K. This reaction involves the ReOx–Au/CeO2-catalyzed deoxydehydration of 1,4-anhydroerythritol to 2,5-dihydrofuran and ReOx/C-catalyzed successive isomerization, hydration and reduction reactions of 2,5-dihydrofuran.