Xianhai Zeng

Catalytic transfer hydrogenation of biomass-derived 5-hydroxymethyl furfural to the building block 2,5-bishydroxymethyl furan

An efficient process for the catalytic transfer hydrogenation of biomass-derived 5-hydroxymethyl furfural (HMF) to 2,5-bishydroxymethyl furan (BHMF) is presented using ethanol as a hydrogen donor and solvent over low-cost ZrO(OH)2. A HMF conversion of 94.1% and a DHMF selectivity of 88.9% were achieved at 423 K in 2.5 h. The fresh, spent, and regenerated catalysts were characterized comprehensively, and the OH group of ZrO(OH)2 as sites for ligand exchange with ethanol was considered to be important for the activity.

In Situ Generated Catalyst System to Convert Biomass‐Derived Levulinic Acid to γ‐Valerolactone

This is the first report of HCl/ZrO(OH)2 catalysts prepared in situ by the autonomous decomposition of ZrOCl2⋅8 H2O in levulinic acid (LA)/2‐butanol solution, which catalyzed the esterification of LA in tandem with hydrocyclization to γ‐valerolactone (GVL) by Meerwein–Ponndorf–Verley (MPV) reduction without the use of external H2. A maximum GVL yield of 92.4 % from neat LA and a GVL formation rate of 1092.2 μmol g−1 min−1 were achieved in 2‐butanol at 240 °C in 2 h. The in situ generated ZrO(OH)2 was characterized comprehensively and its unexpected catalytic efficiency was attributed mainly to its extremely high surface area. A crude LA stream from the acid hydrolysis of cellulose was extracted into 2‐butanol and subjected to this catalyst system to give a GVL yield of 82.0 % even in the presence of humins.

Fed-batch strategy for enhancing cell growth and C-phycocyanin production of Arthrospira (Spirulina) platensis under phototrophic cultivation

The C-phycocyanin generated in blue-green algae Arthrospira platensis is gaining commercial interest due to its nutrition and healthcare value. In this study, the light intensity and initial biomass concentration were manipulated to improve cell growth and C-phycocyanin production of A.platensis in batch cultivation. The results show that low light intensity and high initial biomass concentration led to increased C-phycocyanin accumulation. The best C-phycocyanin productivity occurred when light intensity and initial biomass concentration were 300μmol/m(2)/s and 0.24g/L, respectively. The fed-batch cultivation proved to be an effective strategy to further enhance C-phycocyanin production of A.platensis. The results indicate that C-phycocyanin accumulation not only requires nitrogen-sufficient condition, but also needs other nutrients. The highest C-phycocyanin content (16.1%), production (1034mg/L) and productivity (94.8mg/L/d) were obtained when using fed-batch strategy with 5mM medium feeding.

In Situ Catalytic Hydrogenation of Biomass‐Derived Methyl Levulinate to γ‐Valerolactone in Methanol

In this work, the hydrocyclization of methyl levulinate (ML) to γ-valerolactone (GVL) was performed in MeOH over an in situ prepared nanocopper catalyst without external H2 . This nanocopper catalyst served as a dual-functional catalyst for both hydrogen production by MeOH reforming and hydrogenation of ML. Nearly quantitative ML conversion with a GVL selectivity of 87.6 % was achieved at 240 °C in 1 h in MeOH under a nitrogen atmosphere. ML in the methanolysis products of cellulose also could be hydrogenated effectively to GVL over this nanocopper catalyst even in the presence of humins to give an ML conversion of 94.1 % and a GVL selectivity of 73.2 % at 240 °C in 4 h. The absorption behavior of humins on the surface of the nanocopper catalyst was observed, which resulted in a pronounced increase in the acidic sites of the nanocopper catalyst that facilitate ring-opening and the hydrocarboxylation/alkoxycarbonylation of GVL to byproducts.

Green processing of lignocellulosic biomass and its derivatives in deep eutectic solvents

The scientific community has been seeking cost-competitive and green solvents with good dissolving capacity for the valorization of lignocellulosic biomass. At this point, deep eutectic solvents (DESs) are currently emerging as a new class of promising solvents that are generally liquid eutectic mixtures formed by self-association (or hydrogen-bonding interaction) of two or three components. DESs are attractive solvents for the fractionation (or pretreatment) of lignocellulose and the valorization of lignin, owing to the high solubility of lignin in DESs. DESs are also employed as effective media for the modification of cellulose to afford functionalized cellulosic materials, such as cellulose nanocrystals. More interestingly, biomassderived carbohydrates, such as fructose, can be used as one of the constituents of DESs and then dehydrated to 5-hydroxymethylfurfural in high yield. In this review, a comprehensive summary of recent contribution of DESs to the processing of lignocellulosic biomass and its derivatives is provided. Moreover, further discussion about the challenges of the application of DESs in biomass processing is presented.

Flotation: A promising microalgae harvesting and dewatering technology for biofuels production

Microalgal biomass as renewable energy source is believed to be of great potential for reliable and sustainable biofuels production. However, microalgal biomass production is pinned by harvesting and dewatering stage thus hindering the developing and growing microalgae biotechnology industries. Flotation technology applied in mineral industry could be potentially applied in microalgae harvesting and dewatering, however substantial knowledge on different flotation units is essential. This paper presents an overview on different flotation units as promising cost‐effective technologies for microalgae harvesting thus bestowing for further research in development and commercialization of microalgae based biofuels. Dispersed air flotation was found to be less energy consuming. Moreover, Jameson cell flotation and dispersed ozone flotation are believed to be energy efficient microalgae flotation approaches. Microalgae harvesting and dewatering by flotation is still at embryonic stage, therefore extended studies with the focus on life cycle assessment, sustainability of the flotation unit, optimization of the operating parameters using different algal species is imperative. Though there are a number of challenges in microalgae harvesting and dewatering, with well designed and developed cultivation, harvesting/dewatering, extraction and conversion technologies, progressively, microalgae technology will be of great potential for biological carbon sequestration, biofuels and biochemicals production.

Green catalytic conversion of bio-based sugars to 5-chloromethyl furfural in deep eutectic solvent, catalyzed by metal chlorides

Correction for ‘Green catalytic conversion of bio-based sugars to 5-chloromethyl furfural in deep eutectic solvent, catalyzed by metal chlorides’ by Miao Zuo et al., RSC Adv., 2016, 6, 27004–27007.

Development of a Two-Stage Microalgae Dewatering Process – A Life Cycle Assessment Approach

Even though microalgal biomass is leading the third generation biofuel research, significant effort is required to establish an economically viable commercial-scale microalgal biofuel production system. Whilst a significant amount of work has been reported on large-scale cultivation of microalgae using photo-bioreactors and pond systems, research focus on establishing high performance downstream dewatering operations for large-scale processing under optimal economy is limited. The enormous amount of energy and associated cost required for dewatering large-volume microalgal cultures has been the primary hindrance to the development of the needed biomass quantity for industrial-scale microalgal biofuels production. The extremely dilute nature of large-volume microalgal suspension and the small size of microalgae cells in suspension create a significant processing cost during dewatering and this has raised major concerns towards the economic success of commercial-scale microalgal biofuel production as an alternative to conventional petroleum fuels. This article reports an effective framework to assess the performance of different dewatering technologies as the basis to establish an effective two-stage dewatering system. Bioflocculation coupled with tangential flow filtration (TFF) emerged a promising technique with total energy input of 0.041 kWh, 0.05 kg CO2 emissions and a cost of

Light intensity and N/P nutrient affect the accumulation of lipid and unsaturated fatty acids by Chlorella sp.

0.0043 for producing 1 kg of microalgae biomass. A streamlined process for operational analysis of two-stage microalgae dewatering technique, encompassing energy input, carbon dioxide emission, and process cost, is presented.

Methyl 4-methoxypentanoate: a novel and potential downstream chemical of biomass derived gamma-valerolactone

In this study, different light intensities (80, 160, 240 and 320 μmol/m(2) s) and various mediums including control medium (CM), N/P rich medium (NPM), N rich medium (NM), and P rich medium (PM) were applied for cultivation of Chlorella sp. It was revealed that cultivation of Chlorella sp. in CM under the light intensity of 320 μmol/m(2) s led to a lipid content up to 30% enhancement, which was higher than the results of other cases. A rather high unsaturated fatty acid (UFA) content of 7.5% and unsaturated fatty acid/total fatty acid (UFA/TFA) ratio of 0.73 were obtained under 320 μmol/m(2) s in CM, indicating that the CM-320 system was applicable for the generation of UFA. Moreover, Chlorella sp. cultivated in PM under 320 μmol/m(2) s provided higher TFA content (7.3%), which was appropriate for biofuel production.