One-Pot Degradation of Cellulose into Furfural Compounds in Hot Compressed Steam with Dihydric Phosphates

Direct conversion of cellulose into furfural compounds (5-hydroxymethylfurfural and furfural) in hot compressed steam with the aid of phosphates was studied under temperatures of 250–330 °C and pressures of 0.5–3.5 MPa. The water in the steam could be adsorbed by cellulose to form water molecule layers, which could hydrolyze cellulose. Basic Na₂HPO₄ was found to be favorable for fragment product formation through hydrolysis of cellulose followed by retro-aldol condensation of saccharide, while the acidic dihydric phosphates (LiH₂PO₄, NaH₂PO₄, and Ca­(H₂PO₄)₂) were favorable for furfural compound formation through the hydrolysis–dehydration process. A total furfural compound yield of 34% was obtained under optimal conditions with the aid of NaH₂PO₄, accompanied by 16% solid residue formation. The solid residue containing dihydric phosphates could be used as phosphatic fertilizer

Hydrocarbon Distribution of Cellulose Hydrogenolysis over Ru–MoO_<i>x</i>/C Combined with HZSM‑5

In this paper, acidic HZSM-5 coupled with the hydrodeoxygenation catalyst Ru–MoOx/C was applied for cellulose conversion to chain-mediated small-molecule alkanes in a water-containing biphasic solvent. The physicochemical properties of the binary catalyst Ru–MoOx/C were studied by an array of characterization methods. Meanwhile, the factors (such as the HZSM-5/Ru/MoOx ratio, reaction temperature, H2 pressure, and volume ratio of the aqueous phase and organic phase) that influenced the yield of natural gas (CH4), liquefied petroleum gas (C2–C4 alkanes), and gasoline (C5–C6 alkanes) were thoroughly investigated, obtaining the highest CH4 yield of 56.1% and the highest C5–C6 alkane yield of 66.1% by adjusting the volume ratio of the aqueous phase and organic phase, respectively. Especially, a promising yield of C2–C4 alkanes (43.7%) was obtained via precisely tailoring C–C bond splitting. HZSM-5 in water was proved as the solid acid for hydrolyzing cellulose to glucose, followed by transferring to Ru–MoOx/C located at the water–oil interface for further hydrogenolysis to alkanes. The fact that small-molecule alkane distribution can be controlled by Lewis acid density over Ru–MoOx/C was clarified: the lower Lewis acid density proved C1–C4 alkane production, while a higher Lewis acid density favored C5–C6 alkane production

Tandem Conversion of Fructose to 2,5-Dimethylfuran with the Aid of Ionic Liquids

Biomass-derived 2,5-dimethylfuran (DMF) is an ideal, renewable gasoline additive, and its production with high productivity is highly desirable. A continuous production route was developed to yield DMF from fructose via a tandem strategy, where dehydration catalysts (HY zeolite and niobium phosphate) assisted by 1-butyl-3-methylimidazolium chloride ([BMim]­Cl) and hydrodeoxygenation (HDO) catalyst Cu–Ru/C were integrated into one reaction system with γ-butyrolactone (GBL) as the mobile phase. Optimum conditions, such as temperature, H2 pressure, weight hourly space velocity, and [BMim]­Cl concentration, were investigated systematically, with an initial HDO study by using 5-hydroxymethylfurfural (HMF) as substrate and subsequent tandem dehydration and HDO to produce DMF with fructose as substrate. Among the conditions, the highest yield of DMF at 55.2% was gained by niobium phosphate and Cu–Ru/C, with the aid of [BMim]­Cl in a fixed bed. Meanwhile, [BMim]Cl facilitated fructose dehydration to HMF and also mediated HDO of the resultant HMF by stabilization, which was clarified by 1H NMR and FTIR spectroscopy. Finally, the fact that carbon deposit led to catalyst deactivation was examined thoroughly via a series of characterization techniques. This work achieved continuous DMF production from fructose and laid a foundation for future possible amplification of DMF

Manganese-Promoted Fe₃O₄ Microsphere for Efficient Conversion of CO₂ to Light Olefins

In this work, manganese well-dispersed on Fe3O4 microsphere (Mn–Fe3O4) catalyst was synthesized. It exhibited excellent catalytic performance for the direct conversion of carbon dioxide (CO2) into light olefins. A CO2 conversion of 44.7% with high selectivity of light olefin (46.2%, yield of 18.7%), high O/P ratio (6.5), and low selectivity of CO (9.4%) was obtained over the 10Mn–Fe3O4 catalyst. The Mn–Fe3O4 catalyst was studied by XRD, SEM, (HR)­TEM, STEM–EDS, H2-TPR, and CO2-TPD. The result indicated that the manganese promoter could facilitate the adsorption of CO2 and the activation of CO bonds as well as inhibit the secondary hydrogenation. This work offered a novel Fe-based catalyst system to the utilization of CO2 and an understanding in promoting CO bond activation in the first step of CO2 hydrogenation to hydrocarbon reaction

Selective Cellulose Hydrogenolysis to 2,5-Hexanedione and 1‑Hydroxy-2-hexanone Using Ni@NC Combined with H₃PO₄

The production of ketones from cellulose is critical but challenging due to the easy hydrogenation of ketone groups. Herein, Ni particles encapsulated in N-doped carbon layers (Ni@NC) were synthesized and used as efficient catalysts for direct cellulose hydrogenolysis to 2,5-hexanedione (HD) and 1-hydroxy-2-hexanone (HHO) in H3PO4 aqueous solution. HD and the first reported HHO in this work could be simultaneously produced with the yields of 34.1% and 24.5%, respectively. It was found that the hydrolyzed glucose was the key intermediate in the formation of these two target products. HD originated from the hydrolysis of 2,5-dimethylfuran (2,5-DMF) that was produced via glucose (from cellulose hydrolysis catalyzed by H3PO4) isomerization to fructose, followed by fructose dehydration to 5-hydroxymethylfurfural (5-HMF) and 5-HMF hydrodeoxgenation. In parallel, HHO was obtained from the selective hydrodeoxygenation of hexoses. The N species of Ni@NC catalysts acted as the basic sites for promoting glucose isomerization to fructose. The production of ketones could be attributed to the tailored hydrogenation ability of Ni@NC, which facilitated the selective preservation of CO bonds. The synergy between H3PO4 (cellulose hydrolysis and C–O bond splitting by hydrogenolysis), base (aldehyde isomerization to ketone), and metallic Ni (hydrogenation) played an essential role in the formation of ketone-containing products with high yields