With the growing shortage of fossil energy and the increasing of concerns over global climate changes and environmental problems have driven the development of alternative energy sources. Recently, ...great interest has been oriented towards the development of sustainable resources, especially the utilization of lignocellulosic biomass, a renewable and the most abundant source of biomass originating from plant photosynthesis in nature. Catalytic conversion of renewable cellulosic biomass can produce a series of compounds such as 5-hydroxymethylfurfural (HMF) and 2,5-dimethylfuran (DMF) which are important platform compounds and ideal renewable alternative to fossil fuels. To obtain the renowned bio-based platform molecules, various catalysts and reaction systems have been used in the past decade years. To fully understand current biomass to HMF and DMF development, it is necessary to have an overview and comparison of different homogeneous and heterogeneous catalysts. The reaction systems also exhibit a remarkable impact on the yield and distribution of products with different catalysts. General trends and future research directions of using biomass for HMF, DMF production are also discussed systematically.
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•Shifting from fossil resources to sustainable biomass for chemicals production is important in both academic and our society.•A comprehensive review about the catalytic conversion of biomass into HMF and DMF have been presented.•Catalysts, and reaction systems for the production of HMF and DMF developed in the last few years are discussed.•The scale-up conversion of biomass and the process economy analysis of HMF and DMF production are also discussed.
Iron carbide catalysts encapsulated in graphene-like carbon were synthesized
via
a facile method by pyrolysis of an iron-glucose precursor. Different amounts of potassium (0-5 wt%) were
in situ
doped ...into the catalyst simultaneously. Glucose played a role both as the precursor to form a carbon support and a reducing agent that reduced iron oxides to -Fe
3
C during the catalyst preparation. -Fe
3
C underwent a phase transformation to χ-Fe
5
C
2
as the active phase in Fischer-Tropsch synthesis. Characterization of the structural and chemical properties of the prepared catalysts revealed a core-shell structure with iron carbides enwrapped by several graphene-like layers. The addition of a potassium promoter increased the amount of defects on graphene-like layers and facilitated the formation of iron carbides during the catalyst preparation. Fischer-Tropsch synthesis under typical reaction conditions (320 °C, 20 bar, H
2
/CO = 1, GHSV = 15 000 ml g
cat
−1
h
−1
) was carried out in a fixed bed reactor. A higher light olefin selectivity was obtained than that on common iron catalysts, probably because of the electron-rich surfaces of the prepared catalysts that made it hard for hydrogen to hydrogenate the unsaturated intermediates. A volcano-like evolution of light olefin selectivity was observed on the catalysts with different contents of K, and the highest olefin selectivity reached 41.9% on the 2K-Fe
3
C@C catalyst (
i.e.
, doped with 2 wt% of K). The induction period of the catalyst was shortened by K addition. No drastic changes in the catalyst morphology and performance during 100 h time on stream can be ascribed to the protection of graphene-like carbon layers that prevented the supported iron particles from migration and aggregation under harsh conditions in Fischer-Tropsch synthesis.
Enhanced FTO catalyst performance and catalyst stability are achieved over a graphene-like carbon encapsulated iron carbide catalyst, which is prepared by a facile pyrolysis method.
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•The co-pyrolysis of lignin and waste cooking oil yielded up to 82.6% mono-aromatics.•The highest synergistic extent for mono-aromatic production was 52.1%.•Lignin-derived model ...compounds were selected for co-pyrolysis to study the mechanism.•Guaiacol was more active to be converted to aromatics than o-cresol and phenol.•The mechanism of catalytic co-pyrolysis of lignin and waste cooking oil was proposed.
Lignin and waste cooking oil are wastes from paper and food industries, respectively. In this work, the catalytic fast co-pyrolysis of lignin and waste cooking oil for the production of aromatics in a pyroprobe was investigated with an aim to improve the utilization of lignin waste and waste cooking oil. Furthermore, lignin-derived monomers, including phenol, o-cresol, and guaiacol, were also used as model feedstock for the catalytic co-pyrolysis in order to study the mechanism underlying aromatic formation. The mechanistic study helped lay theoretical foundation for the industrial application of the co-pyrolysis process. The effects of catalyst and waste cooking oil addition on co-pyrolysis product fractional yield and selectivity were studied. High amount of waste cooking oil in the feedstock with appropriate catalyst-to-feedstock ratio (3:1) contributed to high peak-area yields of the total detected compounds and aromatics. The alkylation and demethoxylation of phenols were enhanced at high ratios of catalyst to feedstock and waste cooking oil to lignin. When the ratio of waste cooking oil to lignin was 1:1, the highest mono-aromatic selectivity (82.6%) and synergistic extent (52.1%) for mono-aromatic production were obtained. The catalytic co-pyrolysis of the lignin-derived monomers and waste cooking oil showed that guaiacol was the most active compound to be converted to aromatics, followed by o-cresol, and phenol. The reaction mechanism underlying the formation of aromatics from the synergistic conversion of aliphatics and phenolics was elaborated.
The high cost of large-scale cultivation of microalgae has limited their industrial application. This study investigated the potential use of mixed biogas slurry and municipal wastewater to cultivate ...microalgae. Pig biogas slurry as the sole nutrient supplement, was assessed for the cultivation of Chlorella zofingiensis in municipal wastewater. Batch culture of various ratios of pig biogas slurry and municipal wastewater were compared. The characteristics of algal growth and lipid production were analyzed, and the removal rates of nitrogen and phosphate were examined. Results indicate that 8% pig bio-gas slurry in municipal wastewater, had a significant effect on microalgal growth. C. zofingiensis, with 2.5 g L−1 biomass, 93% total nitrogen and 90% total phosphorus removal. Lipid content was improved by 8% compared to BG11 medium. These findings show that mixing pig biogas slurry and municipal wastewater, without additional nutrition sources, allows efficient cultivation of C. zofingiensis. This is of high research and industrial significance, allowing cultivation of C. zofingiensis in mixed waste culture solution without additional nutrition sources.
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 CO 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 CO bond activation in the first step of CO2 hydrogenation to hydrocarbon reaction.
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•Hydrolyzed lignin depolymerization was presented using mesoporous catalysts.•Mesoporous SBA-15 played a positive role in reducing the char formation.•The addition of Al and Ni could ...effectively promote the lignin depolymerization.•Reaction conditions showed a great effect on lignin depolymerization.•Ethanol was more effective in suppressing the repolymerization than other solvents.
In this work, the mesoporous SBA-15 and a series of modified catalysts based on it, such as Al-SBA-15 and Ni/Al-SBA-15, were synthesized and used for eliminating the char formation during the depolymerization of hydrolyzed lignin. The temperature, time and solvent effects on the lignin depolymerization were also investigated. Results showed that the repolymerization was effectively suppressed over SBA-15 due to its well-ordered pore structure and large pore size. The addition of Al and Ni elements in SBA-15 could improve the lignin depolymerization performance and saturate the instable intermediates. Ethanol was found to be more effective in suppressing repolymerization than other solvents. 81.4% liquefaction degree and 21.90wt% monomer yield was achieved, and no obvious char was observed after the depolymerization of hydrolyzed lignin in ethanol solvent at 300°C for 4h over Ni/Al-SBA-15(20) catalyst.
Since selective control in catalytic reductive aminations of aldehyde for the synthesis of functional amines was highly valued, we developed three kinds of COFs supported catalysts (Pt/COF, Pd/COF, ...and Rh/COF) for selectively catalytic reductive amination of benzaldehyde. Results indicated that Pd/COF and Pt/COF exhibited good selectivity towards secondary amines with a 1.2/1 M proportion of aldehyde and ammonia, while Rh/COF catalyst can selectively convert benzaldehyde to secondary imine with an excellent yield of 90%. Furthermore, an improved yield of primary amine could be obtained over Rh/COF catalyst with a 1.2/60 M proportion of aldehyde and ammonia.
•This work provides metals-based COFs for selective control in reductive amination of benzaldehyde towards amines.•The Pd and Pt-based COF exhibited relatively high selectivity towards secondary amines from benzaldehyde.•Rh-based COF shows high catalytic activity for converting benzaldehyde to secondary imine.
An efficient catalytic process for upgrading of bio-oil was proposed with pristine Ni/MgO catalyst and ethanol solvent. Esterification, hydrogenation, depolymerization and alkylation of aromatic ring ...took place simultaneously during the upgrading process, obtaining an upgraded bio-oil with higher HHV and weaker acidity. Display omitted
•Upgraded bio-oil with higher HHV and weaker acidity was obtained.•Acids and aldehydes were converted efficiently during the upgrading process.•Cleavage of aryl ether bond was facilitated by Ni/MgO catalyst.•Lignin-derived oligomers were further depolymerized during the upgrading process.•Alkylation of aromatic ring took place during the upgrading process.
To improve the quality of fast pyrolysis bio-oil, an efficient catalytic upgrading process is proposed with pristine Ni/MgO catalyst and ethanol. Esterification, hydrogenation, alkylation of aromatic ring and depolymerization of lignin-derived pyrolytic oligomers simultaneously occurred in the upgrading process. Esters, ketones and alkyl-substituted aromatic compounds were found to be the main components in the volatile fraction of the upgraded bio-oil. Under the optimal conditions, pH value and HHV (high heating value) of the upgraded bio-oil were 5.01 and 24.9MJkg−1, respectively. This result suggested that the properties of bio-oil could be effectively improved by the catalytic upgrading process. Moreover, carbon efficiency of this upgrading process was relatively high because that formation of coke is suppressed in the upgrading process.
•An efficient and economic process for lignin depolymerization was achieved.•THF advantaged excellent lignin dissolution ability and catalyst promotion effect.•13.2% yield of phenolic monomer was ...obtained under optimized condition.•This base-catalyzed process can inhibit char formation significantly.
The depolymerization of renewable lignin for phenolic monomer, a versatile biochemical and precursor for biofuel, has attracted increasing attention. Here, an efficient base-catalyzed depolymerization process for this natural aromatic polymer is presented with cheap industrial solid alkali MgO and biomass-derived solvent tetrahydrofuran (THF). Results showed that more than 13.2% of phenolic monomers were obtained under 250°C for 15min, because of the excellent lignin dissolution of THF and its promotion effect on the catalytic activity of MgO. Furthermore, comparison characterization on the raw material, products and residual solid using elemental analysis, FT-IR, TG–DSC, Py–GC–MS and chemo-physical absorption and desorption demonstrated that this base-catalyzed process can inhibit char formation significantly. Whereas, the fact that thermal repolymerization of oligomer on the pore and surface of catalyst resulting in the declination of the catalytic performance is responsible for the residue formation.
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•Phase transformation during reduction is following as α-Fe2O3→Fe3O4→FeO→α-Fe.•Carburization ability of reduced iron phases is following as α-Fe>FeO>Fe3O4.•Iron carbides are formed on ...the Fe(II) oxide species.•Hydrocarbons species are formed gradually on the surface of iron carbides.
Reduction and carburization behaviors of iron phases over a precipitated iron-based Fischer–Tropsch synthesis (FTS) catalyst were investigated by some techniques of Mössbauer effect spectroscopy (MES), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) as well as H2&CO temperature-programmed desorption (H2&CO-TPD). It was found that in H2 atmosphere phase transformation of iron phases involved α-Fe2O3→Fe3O4→FeO→α-Fe, both occurring in the bulk and on the surface layers. All of reduced iron species took place the carburization reaction, whereas carburizing ability was following the order α-Fe>FeO>Fe3O4. During FTS both iron carbides and Fe(II) oxide species reached a balance state without appearing the intermediate α-Fe. The conversion of reduced iron phases to iron carbides (especially for χ-Fe5C2) on the surface layers played a positive role in promoting the formation of hydrocarbons species.
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