Ru/P-Containing Porous Biochar-Efficiently Catalyzed Cascade Conversion of Cellulose to Sorbitol in Water under Medium-Pressure H2 Atmosphere

Abstract

This paper discloses a simple and productive strategy for the preparation of biochar-based bifunctional catalysts. In this strategy, very cheap bamboo powder is thermally carbonized to yield P-containing porous biochars (PBCs) by the activation of concentrated phosphoric acid (H3PO4), and the latter can be transformed into the target catalysts via loading Ru nanometer particles (NPs) on them (marked as Ru/PBCs). A series of characterizations and measurements support that PBCs have stable and rich micro-meso pores and small strong acidic protons (0.10–0.28 mmol·g−1) attributable to the grafted and/or skeleton phosphorus groups, as well as a strong affinity to β-1,4-glycosidic bonds, thus exhibiting a good acid catalytic activity for the hydrolysis of cellulose to glucose. More importantly, they are excellent acidic supports for the loading of Ru NPs owing to high BET surface area, which can give the loaded Ru NPs uniform and narrow distribution (1–6 nm). The resulting bifunctional Ru/PBCs catalysts possess excellent hydrolytic hydrogenating activity for the one-pot cascade conversion of cellulose and the optimized conditions can achieve ca. 89% hexitol yield with 98% sorbitol selectivity under relatively mild conditions. This work provides a good example for the preparation of biomass-derived bifunctional catalysts and their applications in biorefinery.

One-Pot Hydrolytic Hydrogenation of Carbohydrates to Hexitols Catalyzed by Ru Loaded P And Si-Containing Hierarchical Porous Biochars with Excellent Catalytic Efficiency

“…On the other hand, the concomitant by-products (humans) during the one-pot conversion likely deposit on the acidic sites and Ru NPs, thus poisoning the bifunctional activities of catalyst, as supported by the reduction in the BET area and pore volume of the recovered catalyst after three successive runs (See the porosity laterdescribed). Notably, the reusability of 1%Ru/PSBC in the recycle runs for one-pot hydrolytic hydrogenation of cellulose is superior to our previously reported 5% Ru/PBC (F. Mao et al 2020), which should be mainly ascribed to the reduction in the humans deposited in the catalyst' pores, supported by a fact that the reduction extent (15.8%) of BET areas in the recovered 1%Ru/PSBC is much lower than that (35%) in the recovered 5%Ru/PBC. This further supports the positive effect of the meso-macropores of 1%Ru/PSBC on improving the mass transfer efficiency and lowering the by-reactions in the one pot conversion of cellulose macromolecules,…”

“…Then, SBP was impregnated with the speci ed amount of 85 wt% H 3 PO 4 (the mass ratio (X) of H 3 PO 4 with SBP was 1 to 3) at the stated temperature (Y, 30, 60 and 100 o C)) for 12 h, followed by that the impregnated sample was heated at rate of 10°C min -1 and carbonized at the stated temperature (Z, 300, 350, 400 and 450°C) for 5 h under N 2 atmosphere, Finally, the carbonized sample was repeatedly washed with plenty of hot water and dried at 100°C to obtain the P and Si-containing biochars (marked as PSBC-X-Y-Z). In addition, the optimized PBC-400 without inserting silica previously reported by us (F. Mao et al 2020), the direct carbonization material (SBC-400) of SBP and the silica activated with three-fold amount of H 3 PO 4 (PS-400) at 400 o C were used as three control samples. The P contents of these acidic supports measured by ICP method were listed in Table S1 (See Supporting Information (SI)).…”

“…1%Ru/PSBC was prepared using PSBC-3-60-400 (1 g) and RuCl 3 aqueous solution (0.07 M, 0.7 mL, corresponding to 1 wt% Ru theoretical loading) as the two main raw materials and the speci c operating procedure could be found in our recently published work (F. Mao et al 2020). The actual Ru loading amount of 1%Ru/PSBC measured by ICP method was ca.0.51 wt%.…”

“…Surface acid density of samples was measured by chemical titration and the speci c operating procedures could be found in our recent publication(F. Mao et al 2020). Phosphorus content of the samples was determined with an ICP-OES equipment (PerkinElmer 8300).…”

“…Fukuoka Cao et al 2018). And more recently, we found that the P-containing biochar (PBC) fabricated under optimial conditions(F. Mao et al 2020) has a much stronger a nity to β-1,4-glycosidic bonds and a higher catalytic activity for cellulose hydrolysis compared to our previously reported ionic liquids (ILs)-functionalized biochar sulfonic acids (BCSA-ILs) with mimicking cellulase functions , so that PBC is a more potential mimetic catalyst for cellulose hydrolysis. On the other hand, we found that the high porosity of PBC is conductive to fabricate an excellent Ru-based bifunctional catalyst for the hydrolytic hydrogenation of cellulose to sorbitol (87.1% yield, 4.0 TOF, see Table 1).…”