•Two pretreatments affect differently the hydrochar properties and its pyrolysis behaviors.•Hydrochar by conventional hydrothermal pretreatment shows higher thermal stability.•Microwave hydrothermal ...pretreatment removes more acetyl.•Hydrochar by microwave hydrothermal pretreatment produces more glucopyranose and less acids.
Comparative study on microwave and conventional hydrothermal pretreatment of bamboo sawdust was carried out in this study. Microwave and conventional hydrothermal pretreatment both improved the hydrochar properties and its pyrolysis behaviors. Proximate and elemental analyses show that the properties of hydrochar from microwave hydrothermal pretreatment are better than conventional hydrothermal pretreatment in terms of calorific value and oxygen content except for 150°C. Microwave hydrothermal pretreatment removes more acetyl groups in hemicellulose compared to conventional hydrothermal pretreatment, which may be attributed to the hot spot effect of microwave irradiation. The peaks of thermogravimetric and derivative thermogravimetric curves of pretreated samples always shifted to higher temperature region. Also, the conventional hydrothermal pretreated samples are more thermally stable than those by microwave heating. In addition, the glucopyranose content in pyrolysis vapors of microwave hydrothermal pretreated bamboo sawdust (190°C) was 9.82% higher than that from conventional hydrothermal pretreated bamboo sawdust. However, the acids content from microwave hydrothermal pretreated bamboo sawdust (150°C) was 4.12% lower. In this regard, microwave hydrothermal pretreatment is more suitable for upgrading the pyrolysis oil quality than conventional hydrothermal pretreatment.
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•Iron nanoparticles-based biochar catalyst was used to produce phenols firstly.•High yields and selectivities of phenols were achieved in the process.•Deactivation mechanism of ...catalyst was illustrated in detail.
Selective production of phenols via ex-situ catalytic pyrolysis of lignocellulosic biomass is a promising route in biomass conversion. Therefore, developing a low-cost and effective catalyst for this process has emerged as an important topic. Here, the iron nanoparticles-based carbonaceous catalysts were prepared via combining hydrothermal carbonization and pyrolysis approach and first used in the catalytic microwave-assisted pyrolysis of torrefied corn cob for phenols production. The effects of catalyst types, catalytic temperature, and catalyst to feedstock ratio on the production of phenolic compounds were studied. The total selectivity of phenols can reach 91.07 area% with the total yield of 18706.6 µg/ml bio-oil using the FeHC@ hydrochar catalyst (prepared by hydrothermal carbonization in the Fe(NO3)3 solution and pyrolysis) at the catalytic temperature of 450 °C and catalyst to feedstock ratio of 5:10. After using seven times, partial loss of catalytic activity of FeHC@hydrochar was found. This study also presented unique insights into the deactivation of carbonaceous catalysts, showing that sintering, oxidation of α-Fe and Fe3C phases, active site coverage, and pore blockage were the causes of the reduction of catalytic performance. Regeneration experiments showed that it is impracticable to calcine deactivated catalyst at an inert atmosphere and more advanced techniques needed to be developed to solve this problem. Overall, this study can provide a reference for realistic scale-up production of renewable phenols.
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•Composite catalysts (ZSM-5/MCM-41) were synthesized and its optimum catalytic conditions were studied.•Microwave-assisted catalytic fast co-pyrolysis (co-MACFP) was adopted in this ...experiment.•The synergistic effect of lignin and catalyst promotes the formation of aromatic compounds.
Microwave-assisted catalytic fast co-pyrolysis (MACFP) of lignin and waste oil with SiC as microwave absorbent and hierarchical ZSM-5/MCM-41 as catalyst were implemented in a microwave-induced reactor. ZSM-5/MCM-41 is a kind of composite catalyst with MCM-41 as shell and ZSM as core. The effects of catalyst temperature, the ratio of feedstock-to-catalyst and the ratio of two reactants (lignin and waste oil) on product distribution and yield were studied. The study shows that catalytic co-pyrolysis is a complex reaction process, and many reaction conditions could affect the final reaction results. The optimum reaction conditions are as follows: catalytic temperature 400 °C, the feedstock-to-catalyst ratio of 10:1 and the ratio of lignin to waste oil of 2:1. Under this reaction condition, the conversion of feedstocks reached 76.00%, the proportion of aromatics was 50.31% and the selectivity of monocyclic aromatic hydrocarbons (MAHs) was 42.83%.
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•Effect of EGCG on macrophage polarization has been thoroughly confirmed.•The suppression of M1 polarization after EGCG treatment was observed.•The promotion of M2 macrophages after ...EGCG treatment has been confirmed.
The intervention of EGCG on M1/M2 macrophage polarization was still unclear and should be studied comprehensively. In this context, the intervention of EGCG on macrophage polarization has been investigated to reveal that EGCG promoted M2 polarization of RAW264.7 upon treating with EGCG. A significant inhibitory effect of EGCG on M1 polarization was observed upon stimulating with LPS and IFN-γ. The expression of macrophage phenotype related marker genes (iNOS, COX-2, IL-1β for M1; Arg-1, Ym-1, IL-10 for M2) demonstrated the suppression of M1 polarization and the promotion of M2 polarization in liver, colon, spleen, and brain. Further analysis against peritoneal macrophages verified the increased M2 phenotypes and decreased M1 macrophages, and the similar variation in liver were confirmed by immunohistochemistry (IHC). No significant variation of spleen macrophages was observed with the general macrophages in declined tendency. Bio-distribution of EGCG and its metabolites (EGC, GA) in different organs has been further determined.
To reduce thermal processing hazards (TPHs), microwave baking has been extensively used in food thermal processing. In this study, the influence of microwave power and microwave time on the formation ...of TPHs and their precursors was explored in microwave-baked biscuits. The results indicated that the content of acrylamide, 5-hydroxymethylfurfural, methylglyoxal, and 3-deoxyglucosone increased linearly with the extension of microwave time (2, 2.5, and 3 min) and microwave power (440, 480, and 520 W). There was a significant correlation between the four TPHs. 3-Deoxyglucosone may directly or indirectly participate in the formation of the other three TPHs. The relationship between TPH levels with some heat-induced sensory characteristics was analyzed. The correlation between the sensory characteristics and the content of TPHs is L
> a
> hardness > Water activity (AW). The correlation coefficients between L
value and the four TPHs are -0.950, -0.891, -0.803, and -0.985. Furthermore, the content of TPHs produced by traditional baking and microwave baking under the same texture level was compared. Compared with traditional baking (190°C, 7 min), microwave baking at 440 W for 3 min successfully decrease methylglyoxal, 3-Deoxyglucosone, acrylamide, and 5-hydroxymethylfurfural content by 60.75, 30.19, 30.87, and 61.28%, respectively. Traditionally baked biscuits, which had a more obvious color, as characterized by lower L
value, larger a
and b
values, are more susceptible to the formation of TPHs. Therefore, microwave baking can reduce the generation of TPHs.
Increasing fossil fuel consumption and global warming has been driving the worldwide revolution towards renewable energy. Biomass is abundant and low-cost resource whereas it requires environmentally ...friendly and cost-effective conversion technique. Pyrolysis of biomass into valuable bio-oil has attracted much attention in the past decades due to its feasibility and huge commercial outlook. However, the complex chemical compositions and high water content in bio-oil greatly hinder the large-scale application and commercialization. Therefore, catalytic pyrolysis of biomass for selective production of specific chemicals will stand out as a unique pathway. This review aims to improve the understanding for the process by illustrating the chemistry of non-catalytic and catalytic pyrolysis of biomass at the temperatures ranging from 400 to 650 °C. The focus is to introduce recent progress about producing value-added hydrocarbons, phenols, anhydrosugars, and nitrogen-containing compounds from catalytic pyrolysis of biomass over zeolites, metal oxides, etc. via different reaction pathways including cracking, Diels-Alder/aromatization, ketonization/aldol condensation, and ammoniation. The potential challenges and future directions for this technique are discussed in deep.
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•Properties of lignocellulosic biomass and its pyrolysis chemistry are extensively reviewed.•Catalytic pyrolysis of lignocellulosic biomass for selective production of valuable chemicals is outlined.•Different catalytic reforming pathways are summarized.•Future research directions and technological challenges are proposed.
Renewable fuels or chemicals from lignocellulosic biomass have the potential to be a substitute for fossil fuels, thereby reducing greenhouse gas emissions and diversifying energy supplies. ...Integrating torrefaction and pyrolysis is a feasible and promising technology that converts biomass into fuels or chemicals. Understanding of the relevant process designs and mechanisms is favorable to the cohesion and optimization of these two processes and the innovation of reactors for commercial-scale biorefineries. First, biomass properties and their corresponding pyrolysis behaviors have been discussed in consideration of the challenge presented by complex biomass structures that limit the in-depth research on torrefaction or pyrolysis. Second, torrefaction fundamentals are illustrated in detail, and many kinetic models with comprehensive mechanism schemes, such as pseudo-mechanistic model and one-, two-, or multi-step models, are summarized. The effect of torrefaction on biomass characteristics and subsequent pyrolysis is reviewed to further elucidate the integrated process. The novel integration of torrefaction and up-to-date pyrolysis techniques is also outlined to improve product quality. Finally, future directions and technological challenges associated with the integrated process are proposed and its economic potential is also evaluated.
•Different torrefaction kinetic models have been developed to guide the reactor design and optimize the parameters.•Torrefaction significantly affects characteristics of biomass feedstock and improves the pyrolysis behavior.•Integrating torrefaction and developing pyrolysis techniques is promising to utilize the biomass energy effectively.•Pyproduct reuse and r heat recovery can enhance the economic competitiveness of the integrated process.•The self-catalysis mechanism of light organic acid and economic evaluation need to be studied further.
Value-added bio-oil with high selectivities of aromatics is produced via catalytic fast pyrolysis of torrefied corn cob over Ni-modified hierarchical ZSM-5 catalyst.
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•NaOH solution ...treatment and Ni modification significantly change the properties of catalyst.•Ni/hierarchical ZSM-5 catalysts for upgrading of torrefied corn cob pyrolysis vapors.•Obtained bio-oil is enriched in aromatics especially mono-aromatics.•Kinetic analysis of catalytic pyrolysis process is conducted to understand thermal behaviors.
Catalytic fast pyrolysis (CFP) of torrefied corn cob using Ni-modified hierarchical ZSM-5 catalyst was conducted in this study. The prepared catalysts were characterized by N2 adsorption and desorption (N2-BET), X-ray diffraction (XRD), and temperature-programmed desorption of NH3 (NH3-TPD). NaOH solution treatment resulted in the lower peak intensities of hierarchical ZSM-5 catalyst in the XRD patterns while Ni modification improved the catalyst framework. In addition, NaOH solution treatment created some mesopores or macropores, but the incorporation of Ni reduced BET surface area and volume of micropores. Though the addition of Ni lowered the acidity of catalyst, Ni-modified hierarchical ZSM-5 catalyst led to higher yields and of aromatic hydrocarbons. What is more, hierarchical ZSM-5 catalysts significantly improved the selectivities of mono-aromatics. Kinetic analysis shows that CFP of torrefied corn cob was second-order reaction and the addition of Ni can obtain a lower activation energy compared with hierarchical ZSM-5 catalyst.
•This is the first time to integrate the in-situ and ex-situ catalysis into pyrolysis process.•The effects of catalyst and temperature on bio-oil and bio-char production were investigated.•The ...proportions of oxygenates and N-containing compounds were reduced significantly.•The BET surface area and removal efficiency of Cd2+ were enhanced by the addition of bentonite.
In this study, production of bio-oil and biochar from soapstock via microwave-assisted co-catalytic fast pyrolysis combining the advantages of in-situ and ex-situ catalysis was performed. The effects of catalyst and pyrolysis temperature on product fractional yields and bio-oil chemical compositions were investigated. From the perspective of bio-oil yield, the optimal pyrolysis temperature was 550°C. The use of catalysts reduced the water content, and the addition of bentonite increased the bio-oil yield. Up to 84.16wt.% selectivity of hydrocarbons in the bio-oil was obtained in the co-catalytic process. In addition, the co-catalytic process can reduce the proportion of oxygenates in the bio-oil to 15.84wt.% and eliminate the N-containing compounds completely. The addition of bentonite enhanced the BET surface area of bio-char. In addition, the bio-char removal efficiency of Cd2+ from soapstock pyrolysis in presence of bentonite was 27.4wt.% higher than without bentonite.
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