Direct Furfural Production from Deciduous Wood Pentosans Using Different Phosphorus-Containing Catalysts in the Context of Biorefining

This study seeks to improve the effectiveness of the pretreatment stage when direct furfural production is integrated into the concept of a lignocellulosic biomass biorefinery. First of all, the catalytic effects of different phosphorus-containing salts (AlPO4, Ca-3(PO4)(2), FePO4, H3PO4, NaH2PO4) were analysed in hydrolysis for their ability to convert birch wood C-5 carbohydrates into furfural. The hydrolysis process was performed with three different amounts of catalyst (2, 3 and 4 wt.%) at a constant temperature (175 degrees C) and treatment time (90 min). It was found that the highest amount of furfural (63-72%, calculated based on the theoretically possible yield (% t.p.y.)) was obtained when H3PO4 was used as a catalyst. The best furfural yield among the used phosphorus-containing salts was obtained with NaH2PO4: 40 +/- 2%. The greatest impact on cellulose degradation during the hydrolysis process was observed using H3PO4 at 12-20% of the initial amount, while the lowest degradation was observed using NaH2PO4 as a catalyst. The yield of furfural was 60.5-62.7% t.p.y. when H3PO4 and NaH2PO4 were combined (1:2, 1:1, or 2:1 at a catalyst amount of 3 wt.%); however, the amount of cellulose that was degraded did not exceed 5.2-0.3% of the starting amount. Enzymatic hydrolysis showed that such pretreated biomass could be directly used as a substrate to produce glucose. The highest conversion ratio of cellulose into glucose (83.1%) was obtained at an enzyme load of 1000 and treatment time of 48 h.

Automated summary

This study investigates the catalytic effects of different phosphorus-containing salts on the conversion of C-5 carbohydrates in lignocellulosic biomass into furfural. It is found that H3PO4 yields the highest furfural production, while NaH2PO4 exhibits the lowest cellulose degradation. The enzymatic hydrolysis shows that pretreated biomass can be directly used to produce glucose.