Abstract Developing novel, high-efficiency and low-cost catalysts poses a core challenge to the production of monocyclic aromatics (MAs) via catalytic fast pyrolysis (CFP) of biomass. Conventional synthesis of short-b-axis ZSM-5 nanosheets suffers from excessive feedstock expenses and severe environmental burdens. Herein, we develop a fluoride-free and low-cost route for the controllable synthesis of short-b-axis ZSM-5 nanosheets using low-cost TPABr as the main structure-directing agent and low-cost colloidal silica as the main silica source, with the co-assistance of Silicalite-1 nanoseeds and urea. By systematic optimization of synthesis parameters, uniform ZSM-5 nanosheets with tunable b-axis lengths ranging from 39 to 160 nm were successfully fabricated. Time-resolved characterizations of crystallization evolution confirm that this synthesis system proceeds through coupled classical and nonclassical crystallization pathways, encompassing epitaxial growth and aggregation of seed crystals, oriented attachment and crystal propagation, as well as monomer addition. CFP tests using cotton stalks demonstrate that stronger catalyst acidity facilitates the generation of BTEX (benzene, toluene, ethylbenzene, and xylene). For samples with identical Si/Al ratios, the b/a axis ratio, serving as a morphological descriptor, influences the yields of MAs and BTEX. Lower b/a ratios favor the formation of MAs and BTEX. The maximum yields of MAs (26.05%) and BTEX (18.94%) are achieved at a b/a value of 0.258. This work delivers a sustainable and economical protocol for catalyst fabrication toward high-value biomass valorization and provides mechanistic guidance for morphology-controllable synthesis of short-b-axis ZSM-5 in fluoride-free systems.
Abstract As next-generation high-frequency communication technologies advance rapidly, microelectronic components require higher processing temperatures and reduced signal loss. Consequently, poly(ester imides) (PEIs) are widely utilized in these fields. However, efficient recycling methodologies for PEIs remain to be established. In this work, we developed a PEI chemical recycling protocol via glycolysis. The proposed system was verified as generally applicable to depolymerizing various types of PEIs. Moreover, the depolymerization process enabled the isolation of aromatic diols: bis(2-hydroxyethyl) terephthalate (BHET) and 5-hydroxy-2-(4-hydroxyphenyl)isoindoline-1,3-dione (HPID). While the recovered BHET established a closed-loop polyester recycling pathway within the glycolysis system, the isolated HPID was converted into aromatic diamine to serve as a precursor for regenerating high-performance PEIs. Among the regenerated samples, a new PEI exhibits a combination of properties, including a 5% thermal decomposition temperature of 414 °C, a high glass transition temperature exceeding 300 °C, a low coefficient of thermal expansion of 18 ppm/°C, and an ultralow dielectric dissipation factor of 0.003 at 10 GHz, compatible with the high-frequency insulation applications of polyimides. Finally, the carbon emission factor was 31.2 kg-CO2/kg-product, comparable to or lower than that of the general monomer precursor for virgin PEIs, which represents an effective strategy to reduce the environmental burden of the PEI glycolysis system. Although glycolysis is primarily used for PEIs rather than the entire polyimide category, PEIs remain an irreplaceable material system for thermally durable and high-frequency insulation applications. In summary, this work establishes a sustainable glycolysis-based upcycling pathway for PEIs. Compared with hydrolysis-, methanolysis-, and aminolysis-based chemical recycling of polyimides, this approach uses ethylene glycol as a low-carbon-footprint, non-toxic solvent to produce valorized chemical products, including recovered BHET and regenerated advanced PEIs.
Abstract Water consumption and wastewater generation are crucial for sustainable lignocellulosic biorefineries. In this work, a closed-loop fermentation with a zero liquid discharge (ZLD) downstream approach has been developed for l-lactic acid (LA) production from acid-pretreated rice straw. Fermentation of rice straw sugars was conducted using in situ product removal (ISPR) with Lactobacillus casei and Indion-860S, a weakly basic anion-exchange resin. The process involves recycling the fermentation spent broth and the regenerated resin for successive fermentation cycles, resulting in gradual xylose enrichment. The study was conducted over 10 cycles and resulted in an average yield of 0.77 ± 0.09 g LA/g consumed glucose. The average glucose consumption was 81.7%. The inlet xylose concentration of the hydrolysate increased 3.2 times from 5.2 to 16.7 g/L by Cycle 10, without any additional unit operation. Furthermore, a ZLD downstream strategy was proposed to convert the eluted sodium lactate into purified free LA, with an integrated mass and energy balance for estimating the variable operating costs of the proposed scheme. Three variable operating cost (VOC) scenarios were evaluated. Scenario 1 (current study, USD 2.164/kg LA), Scenario 2 (ISPR with Amberlite IRA-67, USD 1.520/kg LA), and Scenario 3 (optimized ISPR with Indion-860S resin and spent-broth recycling, USD 1.260/kg LA). Scenario 3 projected the lowest estimated VOC of LA, demonstrating the potential of the recycling strategy for economic and environmental sustainability of lactic acid production from rice straw.
Abstract Polytetrafluoroethylene (PTFE) waste poses persistent environmental challenges due to its exceptional chemical stability. Meanwhile, the conversion of iron oxides, the major components of abundant natural iron ores, into advanced materials commonly involves multistep processing through refined iron precursors. Herein, we report a closed-loop mechanochemical strategy that integrates PTFE waste upcycling with direct iron oxide fluorination. Compared with conventional iron fluoride synthesis relying on hazardous HF-derived fluorochemicals and refined iron salts, this approach utilizes PTFE waste as a fluorine source and avoids fluoride-containing byproducts. During high-energy ball-milling, mechanochemical activation promotes stable C–F bond cleavage in PTFE and oxygen vacancy generation within the iron oxides. The released fluorine is captured by defect-rich iron oxides to form iron fluoride nanoparticles, while the residual PTFE framework evolves into electrochemically active fluorinated carbon containing reversible semi-ionic C–F bonds. The nanocomposite cathode delivers a capacity of 316.7 mAh g–1 with 70.5% retention after 1000 cycles at 0.25 A g–1, surpassing the one-electron theoretical capacity of FeF3 (237.0 mAh g–1). The enhanced electrochemical performance originates from the synergistic contributions of iron fluoride redox reactions and reversible Faradaic reactions of fluorinated carbon. This work establishes a sustainable manufacturing strategy that transforms persistent fluorochemical waste and abundant iron oxide feedstocks into value-added energy materials.
Abstract Microalgae are promising feedstocks for sustainable aviation fuel (SAF) because of their high oil productivity and nonedible nature. In particular, Fistulifera solaris (F. solaris) is an oleaginous marine diatom that has attracted considerable attention as a potential feedstock for SAF production. However, low CO2 solubility limits biomass production. In addition, conventional carbonate-enrichment methods are often species-specific and carbon-intensive. In this study, cultivation using crystalline calcium silicate hydrate (cCSH), a low-cost and environmentally friendly material derived from concrete scrap and waste, was experimentally investigated to improve CO2 enrichment and biomass production. The addition of cCSH increased the dissolved inorganic carbon (DIC) concentration in the medium, mainly through the accumulation of bicarbonate ions (HCO3–). In the presence of cCSH, the DIC concentration was approximately 1.5-fold higher, and the biomass production of F. solaris increased 1.4-fold. The impact on greenhouse gas (GHG) emissions was calculated for a life-cycle microalgae-based SAF production process to evaluate the environmental impact of cCSH. With the introduction of cCSH, GHG emissions were estimated at 67.1 g-CO2eq/MJ, corresponding to an approximately 24.6% reduction compared with the conventional jet fuel. These results indicate that cCSH is a promising carbonate-enrichment material that enhances inorganic carbon supply and biomass production for SAF feedstock production.
