Synthesis of Bio-aromatics from Black Liquors Using Catalytic Pyrolysis

Catalytic Pyrolysis of Polypropylene to Benzene, Toluene, and Xylene (BTX) Using a Double-Fluidized-Bed Reactor

The current plastic value chain is highly linear, leading to large amounts of waste plastics that harm the environment and human health. Recycling is required, and among the options, catalytic pyrolysis is particularly suited to convert polyolefin-rich plastic waste into useful chemicals such as benzene, toluene, and xylene (BTX). In this paper, we demonstrate ex situ catalytic pyrolysis of polypropylene in a continuous double-fluidized-bed reactor to produce BTX. The optimal pyrolysis temperature in the first fluidized-bed reactor was 550 °C, giving a BTX yield of 22.3 wt % (based on PP input). Lowering the nitrogen flow rate and the use of smaller catalyst particle sizes favor BTX formation. Our novel reactor concept showed good operational stability at longer times on stream (TOS, 10 h). Catalyst activity was slightly reduced during TOS, as is evident from a small decrease in BTX yields. Detailed catalyst characterization studies showed that coke formation is the main reason for catalyst deactivation. In addition, chemoselectivity was also a function of TOS and the selectivity to benzene and toluene decreased, while higher amounts of xylenes were formed.

Low Molecular Weight Biobased Aromatics from Pyrolysis Liquids Using Zeolites: Yield Improvements by Using Pyrolysis Oil Fractions

Pyrolysis liquids from lignocellulosic biomass have the potential to be used as a feed for aromatics such as benzene, toluene, and xylenes (BTX) using catalytic upgrading with zeolites. We here report an experimental study on the conversion of various pyrolysis oil fractions to determine the most suitable one for BTX synthesis. For this purpose, the pyrolysis liquid was fractionated using several extraction/distillation steps to give four fractions with different chemical compositions. The fractions were analyzed in detail using nuclear magnetic resonance spectroscopy, elemental analysis, gas chromatography-mass spectroscopy, thermogravimetric analysis, Karl-Fischer titration, and gel permeation chromatography. Catalytic pyrolysis experiments were carried out using a tandem microreactor with H-ZSM-5 (23) as the catalyst. The highest BTX yield of 24% (on a carbon and dry basis) was obtained using the fractions enriched in phenolics, whereas all others gave far lower yields (4.4-9%, on a carbon and dry basis). Correlations were established between the chemical composition of the feed fraction and the BTX yield. These findings support the concept of a pyrolysis biorefinery, where the pyrolysis liquid is separated into well-defined fractions before further dedicated catalytic conversions to biobased chemicals and biofuels using tailored catalysts.

Pd Nanoparticles Immobilized on Pyridinic N-Rich Carbon Nanosheets for Promoting Suzuki Cross-Coupling Reactions

Palladium (Pd) catalysts play a crucial role in facilitating Suzuki cross-coupling reactions for the synthesis of valuable organic compounds. However, conventional heterogeneous Pd catalysts often encounter challenges such as leaching and deactivation during reactions, leading to reduced catalytic efficiency. In this study, we employed an innovative intercalation templating strategy to prepare two-dimensional carbon nanosheets with high nitrogen doping derived from petroleum asphalt, which were utilized as a versatile support for immobilizing Pd nanoparticles (Pd/N-CNS) in efficient Suzuki cross-coupling reactions. The results indicate that the anchoring effect of high-pyridinic N species on the two-dimensional carbon nanosheets enhances interactions between Pd and the support, effectively improving both the dispersibility and stability of the Pd nanoparticles. Notably, the Pd/N-CNS catalyst achieved an overall turnover frequency (TOF) of 2390 h-1 for the Suzuki cross-coupling reaction under mild conditions, representing approximately a nine-fold increase in activity compared to commercial Pd/C catalysts. Furthermore, this catalyst maintained an overall TOF of 2294 h-1 even after five reaction cycles, demonstrating excellent stability. Theoretical calculations corroborate these observed enhancements in catalytic performance by attributing them to improved electron transfer from Pd to the support facilitated by abundant pyridinic N species. This work provides valuable insights into feasible strategies for developing efficient catalysts aimed at sustainable production of biaromatic compounds.

Enhanced Bio-BTX Formation by Catalytic Pyrolysis of Glycerol with In Situ Produced Toluene as the Cofeed

The catalytic coconversion of glycerol and toluene (93/7 wt %) over a technical H-ZSM-5/Al2O3 (60-40 wt %) catalyst was studied, aiming for enhanced production of biobased benzene, toluene, and xylenes (bio-BTX). When using glycerol/toluene cofeed with a mass ratio of 93/7 wt %, a peak BTX carbon yield of 29.7 ± 1.1 C.% (at time on stream (TOS) of 1.5-2.5 h), and an overall BTX carbon yield of 28.7 C.% (during TOS of 8.5 h) were obtained, which are considerably higher than those (19.1 ± 0.4 C.% and 11.0 C.%) for glycerol alone. Synergetic effects when cofeeding toluene on the peak and overall BTX carbon yields were observed and quantified, showing a relative increase of 3.1% and 30.0% for the peak and overall BTX carbon yield (based on the feedstock). These findings indicate that the strategy of cofeeding in situ produced toluene for the conversion of glycerol to aromatics has potential to increase BTX yields. In addition, BTX production on the catalyst (based on the fresh catalyst during the first run for TOS of 8.5 h and without regeneration) is significantly improved to 0.547 ton ton-1catalyst (excluding the 76% of toluene product that is 0.595 ton ton-1catalyst for the recycle in the cofeed) for glycerol/toluene cofeed, which was 0.426 ton ton-1catalyst for glycerol alone. In particular, this self-sufficient toluene product recycling strategy is advantageous for the production and selectivity (relative increase of 84.4% and 43.5% during TOS of 8.5 h) of biobased xylenes.

New insights into the sustainable use of soluble straw humic substances for the remediation of multiple heavy metals in contaminated soil

This study addresses the research gap in understanding the differences in straw decomposition and variations in humic substances (HS) extracted from various treatment conditions. The aim is to explore the potential of soluble straw HS in remediating heavy metal pollution in soils. The study characterizes straw decomposition structures using scanning electron microscopy (SEM) and X-ray diffraction (XRD), while employing gel permeation chromatography (GPC) and fluorescence spectroscopy (EEM) to analyze the molecular weight and degree of humification of extracted straw HS. The removal efficiency of HS for heavy metals is assessed, with a focus on aerobic humic substances (AE-HS) showing the highest potential for heavy metal removal. Spectral analysis and mass spectrometry analysis reveal the role of phenolic compounds, carboxylic acids, and aromatic compounds in AE-HS, forming humates or complexes to remove heavy metals from contaminated soil. Notably, the optimized AE-HS achieved the highest removal efficiency of 96.18 %, 82.75 %, 60.43 %, and 41.66 % for cadmium, copper, zinc, and lead, respectively. This study provides new insights into the preparation of straw for use as a heavy metal remover and has implications for the use of straw humic substances in soil remediation.

Substituted anilides from chitin-based 3-acetamido-furfural

The synthesis of aromatic compounds from biomass-derived furans is a key strategy in the pursuit of a sustainable economy. Within this field, a Diels-Alder/aromatization cascade reaction with chitin-based furans is emerging as a powerful tool for the synthesis of nitrogen-containing aromatics. In this study we present the conversion of chitin-based 3-acetamido-furfural (3A5F) into an array of di- and tri-substituted anilides in good to high yields (62-90%) via a hydrazone mediated Diels-Alder/aromatization sequence. The addition of acetic anhydride expands the dienophile scope and improves yields. Moreover, replacing the typically used dimethyl hydrazone with its pyrrolidine analogue, shortens reaction times and further increases yields. The hydrazone auxiliary is readily converted into either an aldehyde or a nitrile group, thereby providing a plethora of functionalized anilides. The developed procedure was also applied to 3-acetamido-5-acetylfuran (3A5AF) to successfully prepare a phthalimide.

Influence of straw-derived humic acid-like substance on the availability of Cd/As in paddy soil and their accumulation in rice grain

Humic acid amendments have been widely advocated for the remediation of heavy metal-contaminated soil. However, the impacts of straw-derived humic acid-like substances on the remediation of cadmium (Cd) and arsenic (As) co-contaminated paddy soil remain unclear and the potential mechanism required clarification. In this study, we employed a pot experiment and chose a straw-derived humic acid-like substance (BFA) as the amendment with four doses to investigate how BFA affects the availability of Cd and As in soil and their accumulation in rice. The results showed that grain Cd decreased by 25.65-36.03%, while there was no significant change in total As (TAs) with the addition of BFA. The contents of DCB-Fe, DCB-As and DCB-Cd on the root surface decreased by 6.07-40.54% during the whole growth stage. The addition of BFA significantly decreased the pe + pH and enhanced the transformation of crystalline iron oxides (Fed) into amorphous forms (Feo) in the soil. The CaCl₂-extractable Cd decreased and the KH₂PO₄-extractable As increased with the decrease in pe + pH and Fed and the relative increase in Feo. The correlation analysis showed that the decrease in availability of Cd and translocation factor of Cd effectively decreased the grain Cd and the decrease in DCB-Cd may also contribute to decreasing the uptake of Cd by rice. However, the increase in As of roots and shoots might play key roles in restricting the transport of As to rice grains. Consequently, the addition of BFA could effectively reduce the Cd accumulation in rice under flooding conditions, while no risk of As accumulation in rice grain was observed. The present work provides a new perspective for the application of straw-derived humic acid-like substances as amendments on Cd-As co-contaminated soils, which should be advocated as an eco-friendly, economical and effective soil amendment in the future.

Catalytic Pyrolysis of Nonedible Oils for the Production of Renewable Aromatics Using Metal-Modified HZSM-5 Catalysts

Catalytic pyrolysis of triglycerides to aromatics over zeolites is an advanced technology for a high value-added utilization of renewable biomass resources. Therefore, in this research, the catalytic performance of M/HZSM-5 catalysts (M = Zn, Ga, In, Ni, and Mo) during the pyrolysis process of glycerol trioleate and the effect of the compositional difference of several woody oils and waste oils on aromatic formation were investigated. Results revealed that Zn/HZSM-5 with appropriate acidity and metal sites reached the maximum aromatics yield (56.13%) and significantly enhanced the catalytic stability. In addition, these renewable nonedible oils were effectively converted to aromatics over the Zn/HZSM-5 catalyst, the aromatic yield of jatropha oil reached up to 50.33%, and the unsaturation and double bond number of feedstocks were crucial for the production of aromatics. The utilization of biomass resources to produce high value-added aromatics can alleviate the problems caused by the shortage of fossil resources and achieve sustainable green development.

Recent advances in black liquor valorization

Lignocellulosic biomass is projected as a prospective renewable alternative to petroleum for the production of fuel and chemicals. Pretreatment is necessary to disrupt the lignocellulosic structure for extraction of cellulose. Biomass after pretreatment is segregated into cellulose rich solid fraction and black liquor (lignin and hemicelluloses) as a liquid stream. The plant polysaccharide-based industry primarily utilizes the cellulosic fraction as raw material, and carbon rich black liquor discarded as waste or burnt for energy recovery. This review highlights the recent advancements in the biological and chemical valorization of black liquor into fuels and chemicals. The recent research attempted for bioconversion of black liquor into Bioplastic, Biohydrogen, Biogas, and chemicals has been discussed. In addition, the efforts to replace the conventional energy recovery method with the advanced chemical process along with their modifications have been reviewed that will decide the sustainability of the lignocellulosic biomass-based industry.

Regeneration of pristine HZSM-5 extrudates during the production of deeply deoxygenated bio-oil from ex situ catalytic fast pyrolysis of biomass in a bench-scale fluidised-bed reactor

Deeply deoxygenated bio-oil with ∼1 wt% oxygen is produced in ex situ catalytic fast pyrolysis applying an unmodified HZSM-5 with good regeneration performance.

Catalytic Conversion of Free Fatty Acids to Bio-Based Aromatics: A Model Investigation Using Oleic Acid and an H-ZSM-5/Al2O3 Catalyst

The catalytic conversion of oleic acid to aromatics (benzene, toluene, and xylenes, BTX) over a granular H-ZSM-5/Al₂O₃ catalyst (ϕ 1.2-1.8 mm, 10 g loading) was investigated in a continuous bench-scale fixed-bed reactor (10 g oleic acid h^-1). A peak carbon yield of aromatics of 27.4% was obtained at a catalyst bed temperature of 550 °C and atmospheric pressure. BTX was the major aromatics formed (peak carbon yield was 22.7%), and a total BTX production of 1000 mg g^-1 catalyst was achieved within a catalyst lifetime of 6.5 h for the fresh catalyst. The catalyst was deactivated due to severe coke deposition (ca. 22.1 wt % on the catalyst). The used catalyst was reactivated by an ex situ oxidative regeneration at 680 °C in air for 12 h. The regenerated catalyst was subsequently recycled, and in total, 7 cycles of reaction-regeneration were performed. A gradual decrease in the peak carbon yield of BTX was observed with reaction-regeneration cycles (e.g., to 16.3% for the catalyst regenerated for 6 times). However, the catalyst lifetime was remarkably prolonged (e.g., >24 h), leading to a significantly enhanced total BTX production (e.g., 3000 mg g^-1 catalyst in 24 h). The fresh, used, and regenerated catalysts were characterized by N₂ and Ar physisorption, XRD, HR-TEM-EDX, ²⁷Al, and ²⁹Si MAS ssNMR, NH₃-TPD, TGA, and CHN elemental analysis. Negligible changes in textural properties, crystalline structure, and framework occurred after one reaction-regeneration cycle, except for a slight decrease in acidity. However, dealumination of the H-ZSM-5 framework was observed after 7 cycles of reaction-regeneration, leading to a decrease in microporosity, crystallinity, and acidity. Apparently, these changes are not detrimental for catalyst activity, and actually, the lifetime of the catalyst increases, rationalized by considering that coke formation rates are retarded when the acidity is reduced.

Product Distribution of Chemical Product Using Catalytic Depolymerization of Lignin

Lignin depolymerization is a very promising process which can generate value-added products from lignin raw materials. The main objective of lignin depolymerization is to convert the complex molecules of lignin into small molecules. Nevertheless, lignin is natural polymer which the molecules of lignin are extremely complicated due to their natural variability, and it will be a big challenge to depolymerize lignin, particularly high water yield. The various technology and methods are developed to depolymerize lignin into biofuels or bio chemical products including acid/base/metallic catalyzed lignin depolymerization, pyrolysis of lignin, hydroprocessing, and gasification. The distribution and yield of chemical products depend on the reaction operation condition, type of lignin and kind of catalyst. The reactor type, product distributions and specific chemicals (benzene, toluene, xylene, terephthalic acid) production of lignin depolymerization are intensive discussed in this review. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Molecular Composition of Size-Fractionated Fulvic Acid-Like Substances Extracted from Spent Cooking Liquor and Its Relationship with Biological Activity

The treatment of spent cooking liquor is critical for clean production of pulp and paper industry. There is a compelling need to develop a cost-effective and green technology for reuse of organic matter in spent cooking liquor to mitigate the negative impacts on the environment. The objective of this study is to examine the chemical structure of fulvic acid-like substances extracted from spent cooking liquor (PFA) and their relationship with bioactivity in plant growth. Compared with the benchmark Pahokee peat fulvic acid (PPFA), PFA has less aromatic structure, but higher content of lignin, carbohydrates, and amino acid. After fractionation, protein/amino proportion decreased with increasing molecular weight, but the aromaticity increased. Under salt stress, rice seedling growth was promoted by PFA with low molecular weight (<5 kDa), but inhibited by fraction with high molecular weight (>10 kDa). Principal component analysis suggested that promoted growth was more related with chemical structure (O- and N-alkyl moieties) than with molecular weight. This study provided the theoretical basis for development of an innovative green technology of sustainable reuse of spent cooking liquor in agriculture.

Catalytic pyrolysis of lignin in a cascade dual-catalyst system of modified red mud and HZSM-5 for aromatic hydrocarbon production

Catalytic pyrolysis of lignin over a dual-catalyst system of modified red mud and HZSM-5 was carried out in a bench-scale micro-reactor. Effects of pyrolysis temperature, modified red mud to HZSM-5 ratio, catalysts to lignin ratio on the yield of products and selectivity of aromatic hydrocarbons were investigated. Results indicated that 550 °C was the optimal pyrolysis temperature with the maximal yield of bio-oil (20.16 wt%). At a modified red mud to HZSM-5 ratio of 1:1, the content of monocyclic aromatic hydrocarbons (MAHs) increased to 41.27% whereas that of polycyclic aromatic hydrocarbons (PAHs) decreased to 22.65%. Likewise, at a catalysts to lignin ratio of 2:1, a higher content of MAHs was produced with a decreased content of PAHs. The cascade dual-catalyst system may serve as an efficient approach to disposing lignin and red mud wastes with significant environmental impact. Besides, this study provides a solution for the valorization of lignin-rich resources.