Shanhui Zhu

Production of bioadditives from glycerol esterification over zirconia supported heteropolyacids.

The synthesis of bioadditives for biofuels from glycerol esterification with acetic acid was performed over zirconia supported heteropolyacids catalysts using H(4)SiW(12)O(40) (HSiW), H(3)PW(12)O(40) (HPW) and H(3)PMo(12)O(40) (HPMo) as active compounds. The as-prepared catalysts were characterized by N(2)-physisorption, XRD, Raman spectroscopy, NH(3)-TPD, FTIR of pyridine adsorption and H(2)O-TPD. Among the catalysts tested, HSiW/ZrO(2) achieved the best catalytic performance owing to the better combination of surface Brønsted acid sites and hydrothermal stability. A 93.6% combined selectivity of glyceryl diacetate and glyceryl triacetate with complete glycerol conversion was obtained at 120°C and 4h of reaction time in the presence of HSiW/ZrO(2). This catalyst also presented consistent activity for four consecutive reaction cycles, while HPW/ZrO(2) and HPMo/ZrO(2) exhibited distinct deactivation after reusability tests. In addition, HSiW/ZrO(2) can be resistant to the impurities present in bulk glycerol.

One-step hydrogenolysis of glycerol to biopropanols over Pt–H4SiW12O40/ZrO2 catalysts

The one-step hydrogenolysis of biomass-derived glycerol to propanols (1-propanol + 2-propanol), which are known as biopropanols, was investigated over different supported Pt–H4SiW12O40 (HSiW) bi-functional catalysts in aqueous media. Among the catalysts/supports tested, Pt–HSiW supported over ZrO2 converted glycerol to biopropanols with high selectivity and high yield (94.1%), while exhibiting long-term stability (160 h). In addition, this catalyst can be resistant to the impurities present in crude glycerol. The reaction pathway to propanols from glycerol is proposed to proceed mainly through 1,2-propanediol. With the strategy toward one-step hydrogenolysis of glycerol to biopropanols sustainably, the biomass can be readily transformed to biodiesel and biopropanols via glycerol, which will bring about the benign development of the biodiesel industry.

A highly efficient and robust Cu/SiO2 catalyst prepared by the ammonia evaporation hydrothermal method for glycerol hydrogenolysis to 1,2-propanediol

A highly efficient and robust Cu/SiO2 catalyst from a pure-phase copper phyllosilicate precursor was successfully fabricated by the ammonia evaporation hydrothermal (AEH) method. The impregnation (IM) Cu/SiO2 catalyst was prepared for comparison. The structure, morphologies, thermal stability and surface chemical state of these catalysts were comprehensively characterized by ICP, BET, XRD (in situ XRD), N2O chemisorption, H2-TPR, IR and Raman spectroscopy, TEM and XPS. Compared to the IM sample, the AEH catalyst was exceedingly highly active and stable (300 h) for glycerol hydrogenolysis to 1,2-propanediol. The unprecedented catalytic performance was attributed to the strong interaction between Cu and SiO2 species derived from copper phyllosilicate, well-dispersed Cu nanoparticles and the cooperative effect of Cu0 and Cu+. Moreover, active Cu0 species were identified as the primary active sites for glycerol hydrogenolysis, as corroborated by the strong correlation between 1,2-propanediol yield and Cu surface area.

Graphene Oxide: An Efficient Acid Catalyst for Alcoholysis and Esterification Reactions

Evidence is presented for graphene oxide (GO), prepared by modified Hummers method, as a highly active, selective and reusable solid‐acid catalyst for the production of alkyl levulinates via alcoholysis or esterification. 95.5 % yield of ethyl levulinate was achieved by GO in furfuryl alcohol alcoholysis. Moreover, the surface SO3H groups were identified as the primary active sites, while the surface carboxyl groups worked synergistically to adsorb furfuryl alcohol.

Graphene-based catalysis for biomass conversion

Graphene and its derivatives (graphene oxide and reduced graphene oxide) have attracted a great deal of attention and have been widely applied in the field of catalysis science owing to their exceptional physical properties and chemical tunability. This review focuses on the advances of graphene-based materials in catalytic transformation of biomass and platform molecules to value-added chemicals and biofuels, with emphasis on the development of these materials directly as catalysts and promising supports to anchor Bronsted acid sites in addition to metal nanoparticles. The state-of-the-art and future challenges of graphene-based catalysts in biomass utilization are also discussed.

Tailored mesoporous copper/ceria catalysts for the selective hydrogenolysis of biomass-derived glycerol and sugar alcohols

The selective hydrogenolysis of sugar alcohols is a promising means to produce valuable products from renewable biomass resources. The previous Cu-based catalysts generally suffer from low activity and/or poor stability. We report the design and fabrication of a tailored mesoporous copper/ceria catalyst by a one-step solid-state grinding-assisted nanocasting method. This new catalyst truly replicated the morphology and mesoporous structure of the silica template such as SBA-15 and KIT-6. The characterization techniques strongly reflected that Cu2+ was successfully substituted into the CeO2 lattice and Cu nanoparticles were homogenously dispersed in the nanocomposite. This copper/ceria catalyst was highly active (TOF 4.8 h−1) and stable for 300 h in the hydrogenolysis of glycerol to 1,2-propanediol. The excellent catalytic performance is due to monodisperse Cu nanoparticles, strong interaction between Cu and CeO2 species, and tailored mesoporous structure.

Alcoholysis: A Promising Technology for Conversion of Lignocellulose and Platform Chemicals

In the catalytic conversion of lignocellulose to valuable products, the first entry point is to break down these biopolymers to sugar units or aromatic monomers, which is conventionally achieved by hydrolysis in water medium. Recent years have seen tremendous progress in the alcoholysis process, which has remarkable advantages, such as the avoidance of treating waste water, suppression of humins or chars, and enhancement of reaction rate and product yield. Advances have been focused on the alcoholysis of cellulose, hemicellulose, and lignin to alkyl glucosides, xylosides, and aromatic monomers, respectively. Alcoholysis of the platform molecule furfuryl alcohol (FAL) to alkyl levulinate (AL) and integrated alcoholysis of cellulose and furfural into AL are also summarized. This Minireview highlights the comparisons between alcoholysis and hydrolysis, the reaction mechanism of alcoholysis, and future challenges for industrial applications.

One-pot conversion of furfural to alkyl levulinate over bifunctional Au-H4SiW12O40/ZrO2 without external H2

Alkyl levulinate (AL) is an important biofuel additive and precursor for the synthesis of valuable γ-valerolactone. Conventionally, it is produced by furfural hydrogenation with pressured H2, followed by alcoholysis of the formed furfuryl alcohol (FAL). This work provides a novel strategy for the high-yield synthesis of AL via one-pot conversion of furfural with an alcohol over a metal-acid bi-functional catalyst without an external source of hydrogen. Furfural proceeded to transfer hydrogenation reaction using the alcohol as a H-donor over metal species, and then the formed FAL underwent acid-catalyzed alcoholysis to yield AL. The yield of AL reached 80.2% in the conversion of furfural with 2-propanol over Au-H4SiW12O40/ZrO2 under mild conditions. Additionally, the catalyst characterization, reaction pathway, and reusability were well presented.

Effect of tungsten surface density of WO3–ZrO2 on its catalytic performance in hydrogenolysis of cellulose to ethylene glycol

One-pot hydrogenolysis of cellulose to ethylene glycol (EG) was carried out on WO3-based catalysts combined with Ru/C. To probe the active catalytic site for breaking the C–C bond of cellulose, a series of WO3–ZrO2 (WZr) catalysts were synthesized and systematically characterized with XRD, Raman, UV-Vis, H2-TPR, DRIFS and XPS techniques and N2 physisorption experiment. It was found that the WO3 crystallites became more easily reduced to W5+–OH species with increasing crystallite size or tungsten surface density of the WZr catalyst owing to the decrease of their absorption edge energy (AEE) originating from weakening their interaction with ZrO2 support. This, as a result, gave higher EG yield at higher tungsten surface density. The structure–activity relationship of the WZr catalyst reveals that the active catalytic site for cleaving the C2–C3 bond of the glucose molecule is the W5+–OH species.

A Highly Stable Copper-Based Catalyst for Clarifying the Catalytic Roles of Cu0 and Cu+ Species in Methanol Dehydrogenation

Identification of the active copper species, and further illustration of the catalytic mechanism of Cu-based catalysts is still a challenge because of the mobility and evolution of Cu0 and Cu+ species in the reaction process. Thus, an unprecedentedly stable Cu-based catalyst was prepared by uniformly embedding Cu nanoparticles in a mesoporous silica shell allowing clarification of the catalytic roles of Cu0 and Cu+ in the dehydrogenation of methanol to methyl formate by combining isotope-labeling experiment, in situ spectroscopy, and DFT calculations. It is shown that Cu0 sites promote the cleavage of the O-H bond in methanol and of the C-H bond in the reaction intermediates CH3 O and H2 COOCH3 which is formed from CH3 O and HCHO, whereas Cu+ sites cause rapid decomposition of formaldehyde generated on the Cu0 sites into CO and H2 .