Key Takeaways & Executive Findings
- •• • Ca2+ at 7% mass ratio increased biochar yield to 24.96% and H2 volume fraction to 32.49%, demonstrating its strong Lewis acidity for gas-phase enhancement and carbon retention. • • Ca2+ catalysis enriched furan compounds to 65.88% (and 65.89% at 600 °C), indicating high selectivity for deoxygenation and valuable chemical production. • • K+ at 600 °C promoted acid formation to 39.41%, while low K+ concentrations favored phenolics, showing concentration-dependent catalytic pathways for bio-oil composition control. • • Raising pyrolysis temperature from 400 to 600 °C decreased biochar yield and increased gas yield, with H2 and CH4 yields significantly enhanced, enabling process optimization for syngas production.
Abstract
Endogenous alkali and alkaline earth metals (AAEMs) in biomass ash and pyrolysis temperature significantly influence the properties of pyrolysis polygeneration products. This study selected potassium (K+) and calcium (Ca2+) as representative AAEMs, added them at mass ratios of 2%, 5%, and 7% to corn stover via impregnation, and conducted fixed-bed pyrolysis at 400, 500, and 600 °C to investigate the yields and compositions of gas, liquid, and solid products. Results showed that increasing metal ion concentration significantly increased biochar yield, with Ca2+ at 7% achieving 24.96% biochar yield, while bio-oil yield generally decreased. Ca2+ strongly promoted H2 formation due to its Lewis acidity, reaching 32.49% in gas at 7% concentration, and facilitated furan enrichment to 65.88%. K+ at low concentrations favored phenolic formation, while high concentrations promoted ketones and intensified bio-oil cracking. Increasing temperature from 400 to 600 °C decreased biochar yield and increased gas yield, with high temperatures enhancing secondary cracking and reforming, significantly raising H2 and CH4 yields while suppressing oxygenates. At 600 °C, K+ catalysis increased acids to 39.41%, while Ca2+ maintained furans at 65.89%. This study demonstrates that adjusting metal ion concentration and temperature enables directional regulation of high-value bio-oil components and high-energy gases, providing a theoretical basis for optimized biomass pyrolysis utilization.
1. Introduction
Biomass pyrolysis polygeneration offers a carbon-neutral route to produce biochar, bio-oil, and syngas, yet the inherent alkali and alkaline earth metals (AAEMs) in biomass ash often act as uncontrolled catalysts, leading to variable product distributions that hinder commercial scale-up. Prior attempts to mitigate ash effects via demineralization have been costly and energy-intensive, while direct catalytic pyrolysis with synthetic catalysts faces deactivation and economic barriers. The lack of systematic understanding of how endogenous K+ and Ca2+ concentrations and pyrolysis temperature jointly steer product selectivity remains a critical bottleneck for process design.
This study addresses this gap by precisely loading K+ and Ca2+ onto corn stover at controlled mass ratios (2%, 5%, 7%) and pyrolyzing at 400–600 °C in a fixed-bed reactor. By quantifying the yields and detailed compositions of gas, bio-oil, and biochar, the research delineates the distinct catalytic roles of K+ and Ca2+—Ca2+ enhancing H2 and furans, K+ modulating phenols and ketones—and their interaction with temperature. These findings provide actionable parameters for tailoring pyrolysis conditions to maximize high-value products, offering a cost-effective strategy for biomass utilization without external catalysts.
Loading authentic research manuscript (Pages 1–5)...
CAI Hanle, ZHU Liang, CAI Wei, LU Weimiao, ZHANG Yutao, MA Zhongqing (2026). Effects of Endogenous Potassium and Calcium Ions on the Yields and Characteristics of Products from Corn Stalk Pyrolysis. Journal of Fuel Chemistry and Technology. https://doi.org/10.3724/2097-213X.2025.JFCT.0025
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the optimal Ca2+ loading and temperature to maximize H2 yield, and what are the trade-offs with bio-oil composition?
At 7% Ca2+ and 600 °C, H2 volume fraction reached 32.49%, with furan content at 65.89%. However, bio-oil yield generally decreased with increasing metal loading, so maximizing H2 may sacrifice liquid yield. A balance can be struck at 5% Ca2+ and 500 °C, where H2 is still significant while bio-oil retains valuable compounds.
How does K+ concentration affect the selectivity towards phenols versus ketones, and what are the underlying mechanisms?
Low K+ concentrations (2%) favor phenolic formation, likely by promoting cleavage of lignin ether bonds. High K+ concentrations (7%) shift selectivity to ketones, possibly via enhanced secondary cracking of carbohydrates. At 600 °C, K+ also increases acid content to 39.41%, indicating a temperature-dependent shift towards acidic intermediates.
What is the impact of pyrolysis temperature on the synergistic effects with metal ions, and how can this be exploited for process design?
Higher temperatures (600 °C) amplify the catalytic effects of both K+ and Ca2+, increasing gas yields and H2/CH4 production while reducing biochar. For Ca2+, furan selectivity remains high (65.89%) at 600 °C, suggesting that high temperatures can be used to enhance gas quality without compromising valuable bio-oil components.
How do the observed biochar yields compare with those from demineralized biomass, and what are the implications for carbon sequestration?
Ca2+ at 7% increased biochar yield to 24.96%, which is higher than typical yields from demineralized biomass (often below 20%). This suggests that endogenous metals can enhance carbon retention, making the process more favorable for biochar production and carbon sequestration.
What are the scalability challenges of the impregnation method used in this study, and how can they be addressed industrially?
Impregnation is a simple and cost-effective method for laboratory studies, but industrial scale-up may face issues with uniform metal distribution and wastewater management. Alternative methods such as wet mixing or ion-exchange could be explored, but the concentration ranges tested (2-7%) provide a practical window for process optimization.
Related Chinese Research & Cross-Citations
Recent Advances in Carbon-Based Materials for CO2 Capture and Utilization
CO2 capture and utilization (CCU) technologies are critical for mitigating global warming and promoting resource circularity. Carbon-based materials, with tunable pore structures, abundant active sites, high specific surface area, and excellent chemical stability, show significant potential for CO2 capture and conversion. This review systematically analyzes the adsorption behaviors and performance variations of activated carbon, porous carbon, graphene, and carbon nanotubes in CO2 capture. For utilization, recent advances in catalytic applications for methanation, reverse water-gas shift (RWGS), dry reforming of methane (DRM), and alcohol synthesis are emphasized. The benefits and drawbacks of carbon materials regarding adsorption capacity, catalytic activity, and stability are evaluated, and their potential in integrated CCU technologies is discussed. Key strategies for enhancing performance through structural modulation and surface modification are elucidated. This review provides theoretical guidance for future development and large-scale implementation of carbon-based materials in CCU.
Fabrication and Microwave Absorption Performance of FexOy/TiO2/C Composites Derived from Red Mud
Red mud, an industrial solid waste from alumina production, poses severe environmental challenges. This study presents a resource-efficient strategy to convert red mud into high-performance microwave absorbing materials. FexOy/TiO2/C composites were synthesized via a sol-gel method using starch as carbon source, followed by carbothermal reduction. The phase composition and microstructure were optimized by adjusting calcination temperature and raw material ratio. The optimal sample, RmCT-5.4-700, exhibited a minimum reflection loss (RLmin) of -30.2 dB at 14.0 GHz with an effective absorption bandwidth (EAB) of 5.3 GHz at a coating thickness of 2.0 mm. The superior absorption performance is attributed to the synergistic effects of dielectric components (TiO2, graphitized carbon) and magnetic components (Fe3O4/Fe). Carbothermal reduction introduces defects that induce dipole polarization, while the conductive network formed by graphitized carbon and Fe3O4/Fe particles enhances conductive loss. Heterogeneous interfaces between Fe3O4, Fe, TiO2, and the red mud matrix promote interfacial polarization. The magnetic loss of Fe3O4/Fe improves impedance matching, facilitating electromagnetic wave penetration and absorption. This work not only provides a novel route for red mud valorization but also contributes to the high-value utilization of solid wastes.
Damage Mechanism of High Chromia Refractory in the Slag Tapping Hole of Commercial Entrained-Flow Gasifiers
The service life of refractory bricks in the slag tapping hole of entrained-flow gasifiers is a critical bottleneck for long-term stable operation. This study investigated the damage mechanism of high chromia refractories in four commercial coal-water slurry gasifiers by analyzing gasification coal samples and corroded refractory bricks. Slag characteristics, including crystallization and viscosity-temperature behavior, were evaluated. Results revealed that low-viscosity slag induces more severe refractory damage. To mitigate slag crystallization risk, a safe slag tapping temperature range is recommended as tICT−t2.5 when tICT exceeds t25. Interior morphology of corroded bricks exhibited cracks, primarily attributed to molten slag penetration and subsequent reactions with refractory material. SEM-EDS analysis of slag-aggregate and slag-matrix interfaces identified reduction in Cr2O3 content as the earliest damage characteristic. XRD detected no zirconium-containing spinel in cracks, indicating that thermal expansion mismatch between newly formed phases and the refractory matrix drives crack propagation. A damage mechanism is proposed: initial Cr2O3 depletion compromises both matrix and aggregate, facilitating slag ingress and new phase formation, ultimately leading to structural failure. Early detection or prevention of Cr2O3 reduction is essential to prolong refractory service life.
Research advances in the pyrolysis recycling of waste wind turbine blades
The global energy landscape is undergoing a profound transformation, with wind energy gaining increasing prominence due to its clean and renewable nature. However, as installed wind power capacity expands, disposal of waste wind turbine blades (WWTB) has emerged as a significant challenge. These blades are predominantly composed of epoxy resin (EP) polymers, carbon fibers (CFs), and glass fibers (GFs). Improper disposal exacerbates environmental concerns and leads to loss of valuable resources, particularly carbon-based materials. Pyrolysis technology, a versatile and environmentally sustainable method for resource recovery, has garnered considerable attention for WWTB disposal. This work presents a comprehensive review of pyrolytic recycling of WWTB, focusing on principles and classifications of pyrolysis technology, key factors influencing the pyrolysis process, as well as pyrolysis methods, equipment, products, and their applications. Through in-depth analysis of current research, this review identifies critical unresolved issues and provides a forward-looking perspective on emerging research trends. The review highlights that pyrolysis can effectively recover glass fibers and carbon fibers with mechanical property retention depending on process conditions, and that catalytic pyrolysis can enhance the quality of recovered products. Economic analysis indicates that collaborative disposal methods can improve cost-effectiveness. Future research should focus on optimizing process parameters for large-scale industrial application and developing more efficient catalysts to improve product selectivity and fiber quality.
Citric Acid-Modified HUSY Zeolite Catalyzes Alkylation of Phenol with Cyclohexanol for High-Density Aviation Fuel Precursors
Lignin-derived oxygenated aromatics, particularly phenols and aromatic ethers, are promising feedstocks for synthesizing high-density, high-heat-sink aviation fuels via alkylation-hydrogenation processes. This study systematically evaluates the catalytic performance of various zeolites (Hβ, HZSM-5, MCM-41, and HUSY) in the alkylation of phenol with cyclohexanol. Characterization demonstrates that HUSY zeolite exhibits superior catalytic activity due to its favorable pore architecture and well-balanced acid site distribution, which synergistically facilitate molecular diffusion and catalytic transformations. To further enhance catalytic properties, HUSY was modified with citric acid at various concentrations and compared with NaOH and oxalic acid treatments. Results reveal that citric acid treatment preserves crystallinity while modulating acidity and pore structure. All modified zeolites enhance phenol alkylation activity. Notably, HUSY-0.5M, exhibiting the highest medium-strong acid to total acid ratio, achieves superior performance: 80.4% phenol conversion and 99.6% selectivity for alkylation products. The catalyst also shows high activity for various lignin-derived compounds (p-cresol, anisole, guaiacol), demonstrating broad applicability. This work provides a new strategy for valorizing lignin-derived phenols into high-value fuel precursors through alkylation.
Hydrogen Production and Structure Evolution Mechanism during Thermochemical Conversion of Microalgae Pellet in Molten Hydroxide Salts
This study investigates the thermochemical conversion behavior of microalgae pellets in a molten hydroxide salt (80% NaOH-20% Na2CO3) system and its influence on hydrogen production. By comparing temperature evolution, gas release characteristics, and structural evolution of pellets with and without molten salt, and integrating char alkalization experiments, the regulatory mechanism of molten salt on reaction pathways and hydrogen production was systematically analyzed. Results indicate that molten salt significantly enhances internal heat transfer efficiency, achieving a central heating rate of 177 °C/s, effectively alleviating thermal hysteresis. Concurrently, molten salt promotes pore development through penetration, erosion, and catalytic effects, resulting in a porosity increase of 53.2%–104.3% after 10 s of reaction. Conversion efficiency is markedly improved, with the dominant reaction pathway shifting to char alkalization after only 70 s. Furthermore, when heating rate is increased above 600 °C, hydrogen yield from char alkalization improves more significantly, primarily attributed to the synergistic promotion of molten salt catalysis and rapid heating on volatiles reforming. This study provides a theoretical foundation for understanding efficient hydrogen production from biomass in molten hydroxide salts.