Showing papers by "Siming You published in 2021"

Concentrated solar thermochemical gasification of biomass: Principles, applications, and development

Abstract: Bioenergy production is one of the most reliable strategies for replacing fossil fuels and reducing CO2 emissions. Gasification-based bioenergy generation has been extensively studied; however, it is still facing the challenges of limited energy efficiencies, especially upon small-scale development. Concentrated solar thermochemical gasification of biomass (CSTGB) where the endothermic reactions of gasification are driven by concentrated solar thermal energy serves as a promising solution to improve the efficiency of gasification. This review summarized recent development in modeling concentrated solar thermochemical gasification of biomass, the method of concentrated solar thermal for gasification, and applications and development of concentrated solar thermal biomass gasification. The influences of operating parameters toward the performance of the technology were studied, which determine the optimum parameters for maximizing the energy conversion efficiency of the technology. CSTGB could improve the utilization of biomass feedstocks and the total energy efficiency by 30% and 40%, respectively by effectively storing solar energy in the producer gas as compared to conventional gasification.

Machine learning methods for modelling the gasification and pyrolysis of biomass and waste

Abstract: Over the past two decades, the use of machine learning (ML) methods to model biomass and waste gasification/pyrolysis has increased rapidly. Only 70 papers were published in the 2000s compared to a total of 549 publications in the 2010s. However, the approaches and findings have yet to be systematically reviewed. In this work, the machine learning methods most commonly employed for modelling gasification and pyrolysis processes are discussed with reference to their applications, merits, and limitations. Whilst coefficients of determination (R2) can be difficult to compare directly, due to some studies having greatly different approaches and aims, most studies consistently achieved a high prediction accuracy with R2 > 0.90. Artificial neural networks have been most widely used due to their potential to learn highly non-linear input-output relationships. However, a variety of methods (e.g. regression methods, tree-based methods, and support vector machines) are appropriate depending on the application, data availability, model speed, etc. It is concluded that ML has great potential for the development of models with greater accuracy. Some advantages of machine learning models over existing models are their ability to incorporate relevant non-numerical parameters and the power to generate a multitude of solutions for a wide range of input parameters. More emphasis should be placed on model interpretability in order to better understand the processes being studied.

One-step synthesized 3D-structured MOF foam for efficient and convenient catalytic reduction of nitrogen-containing aromatic compounds

Abstract: Metal Organic Frameworks (MOFs) receive increasing attention for 4-nitrophenol (4-NP) reduction; however the existing studies of using MOFs for 4-NP reduction all involve with noble metals. Moreover, the reported MOFs are very fine powders which are inconvenient for realistic implementation. Thus, the present study proposes to develop a MOF foam which exhibits macroscale features of foam and microscale functionalities of MOFs. Specifically, a Cu foam is selected as the macroporous substrate which serves as a porous support and the metal source for synthesizing Cu-based MOF, HKUST-1, via an one-step electrochemical method. The resulting HKUST-1 foam can act as a convenient catalyst for reduction of 4-NP to 4-AP in either batch-type or flow-thru-type reactions. The corresponding activation energy (Ea) of 4-NP reduction (43.3 kJ/mol) is also significantly lower than Ea values of reported catalysts, including noble metal catalysts, whereas the corresponding TOF (48.3 min−1) is higher than many other catalysts. HKUST-1 foam can also efficiently catalyze reduction of methylene blue (MB) to fully decolorize its color. In addition, HKUST-1 foam could be reused over multi-cycles and retain its activity for reduction of 4-NP and MB. These features validate that HKUST-1 foam is a practical, convenient, and reusable catalyst for reduction of 4-NP.

Covalent organic polymer derived carbon nanocapsule–supported cobalt as a catalyst for activating monopersulfate to degrade salicylic acid

Abstract: As salicylic acid (SAC) is an extensively used pharmaceutical, discharge of SAC into the environment has caused serious threats to ecology in view of its toxicity. Therefore, SO4•−-involved chemical oxidation methods have been employed for eliminating SAC. Since monopersulfate (MPS) has become a popular reagent for producing SO4•−, an alternative heterogeneous Co-based catalyst is proposed by using a Co-coordinated covalent organic polymers (Co-COP) as a precursor. Via carbonization, Co-COP is transferred by conversion of Co ions to Co/CoO nanoparticle and conversion of COP to N-doped carbon nanocapsules (CNC), respectively, to form a unique composite of Co NPs embedded into carbon nanocapsule (CoCNC). CoCNC exhibits a higher catalytic activity than Co3O4 nanoparticle for activating MPS to degrade SAC because of synergistic effects between Co NPs and the N-doped CNC which not only acts as the support but also provides active sites. Hence, CoCNC+MPS could afford a much lower Ea value (25.4 kJ/mol) of SAC degradation than the reported values. Moreover, CoCNC is still efficient for removing SAC even in the presence of high-concentration NaCl and SDS. CoCNC can be also recyclable over many cycles and maintain its catalytic activities, confirming that CoCNC is an advantageous catalyst for MPS activation.

Enhanced reduction of bromate in water by 2-dimensional porous Co3O4 via catalytic hydrogenation

Abstract: As catalytic hydrogenation is validated as one of the most useful approach to reduce a potential carcinogenic bromate in water, the usage of continuous purge H2 gas and precious metal catalysts are typically required, making it less feasible for practical implementation. Since sodium borohydride (NaBH4) represents a potential alternative source for releasing H2 and non-precious metal catalysts (cobalt (Co)) are usually required to accelerate the hydrolysis of NaBH4 for faster H2 production, the combination between Co-based catalysts and NaBH4 could be favorable for bromate hydrogenation. Especially, it is even more advantageous to fabricate a porous heterogeneous catalyst with high surface area. Thus, this study aims to construct such a novel porous heterogeneous catalyst for reducing bromate using sodium borohydride. Herein, a Co-coordinated framework with TMC ligand (CoTMC) is employed as precursor, which is then transformed into hexagonal porous Co3O4 (HPCO) via one-step calcination. The resultant HPCO possesses remarkable surficial oxygen vacancies as well as textural properties in comparison with Co3O4 NP. Importantly, HPCO could completely reduce bromate to bromide within 20 min. The calculated bromate removal capacity using HPCO and NaBH4 is achieved as 781.25 μmol/g, and the activation energy (Ea) is also calculated as 28.5 kJ/mol. Besides, HPCO also exhibits high catalytic activities for bromate reduction in the presence of various anions. Moreover, HPCO could be also reusable for reducing bromate to bromide over multiple-cycles without any remarkable change of catalytic activities. These features indicate that HPCO is a robust and effective heterogeneous catalyst for bromate reduction in water.

2-dimensional nanoleaf-like porous copper nitrate hydroxide as an effective heterogeneous catalyst for selective oxidation of hydroxymethylfurfural to diformylfuran

Abstract: Background 2,2,6,6-tetramethylpiperidin-oxyl (TEMPO) accompanied with Cu has been validated as a promising oxidative catalytic process for oxidizing 5-hydroxymethylfurfural (HMF) to value-added products. Since Cu-O cluster plays an important role in TEMPO-based HMF oxidation, and N-O moiety would facilitate the catalytic cycle of TEMPO regeneration, an interesting solid-phase material, copper nitrate hydroxide (CNH) (Cu2(OH)3NO3) is proposed for the first time for co-catalyzing TEMPO to oxidize HMF into a valuable product, 2,5-diformylfuran (DFF). Methods In particular, a CNH with a 2D elliptical and porous surface is fabricated to become the leaf-like porous CNH (LPCNH) to maximize surface contact via a relatively simple procedure, and LPCNH would be an advantageous catalyst with TEMPO for converting HMF into DFF. Significant findings While TEMPO or LPCNH was unable to oxidize HMF into DFF, the combination of LPCNH/TEMPO rapidly, and efficiently converted HMF to DFF with high selectivities. At 140 °C, a significantly high YDFF = 99.3% with SDFF = 100% can be obtained, and surpass almost all reported values, indicating that LPCNH+TEMPO is advantageous and selective to convert HMF into DFF. LPCNH could be also reusable for co-catalyzing with TEMPO for converting HMF to DFF. These findings validate that LPCNH is certainly a useful heterogeneous catalyst for valorizing HMF.

Petroleum waste biorefinery: A way towards circular economy

Abstract: The petroleum industry is one of the fastest-growing sectors in the world owing to their increasing energy needs. Petroleum refinery produces a large number of waste products like volatile organic compounds, oily sludge, wastewater, heavy metals, waste catalyst, etc. The major ecological challenge for this refinery process is to manage the enormous amount of waste considering the nature of the waste and the changing strict environmental regulations. Disposal and spillage of petroleum products in the underground storage sites have also posed significant risks to groundwater sources in many oil-contaminated areas. This chapter provides comprehensive information about recent developments, advancements, barriers associated, and major challenges associated with the process control of petroleum waste management. Circularizing the economy in the petroleum waste biorefinery model for the production of various products has been discussed. Finally, this chapter also highlights the challenges and perspectives in the area of a petroleum refinery to comply with resource recovery and waste management practices.

Enhanced Catalytic Soot Oxidation by Ce-Based MOF-Derived Ceria Nano-Bar with Promoted Oxygen Vacancy

Abstract: As CeO2 is a useful catalyst for soot elimination, it is important to develop CeO2 with higher contact areas, and reactivities for efficient soot oxidation and catalytic soot oxidation are basically controlled by structures and surface properties of catalysts. Herein, a Ce-Metal organic framework (MOFs) consisting of Ce and benzene-1,3,5-tricarboxylic acid (H3BTC) is employed as the precursor as CeBTC exhibits a unique bar-like high-aspect-ratio morphology, which is then transformed into CeO2 with a nanoscale bar-like configuration. More importantly, this CeO2 nanobar (CeONB) possesses porou, and even hollow structures, as well as more oxygen vacancies, enabling CeONB to become a promising catalyst for soot oxidation. Thus, CeONB shows a much higher catalytic activity than commercial CeO2 nanoparticle (comCeO) for soot oxidation with a significantly lower ignition temperature (Tig). Moreover, while soot oxidation by comCeO leads to production of CO together with CO2, CeONB can completely convert soot to CO2. The tight contact mode also enables CeONB to exhibit a very low Tig of 310 °C, whereas the existence of NO also enhances the soot oxidation by CeONB to reduce the Tig. The mechanism of NO-assisted soot oxidation is also examined, and validated by DRIFTS to identify the formation and transformation of nitrogen-containing intermediates. CeONB is also recyclable over many consecutive cycles and maintained its high catalytic activity for soot oxidation. These results demonstrate that CeONB is a promising and easily prepared high-aspect-ratio Ce-based catalyst for soot oxidation.

Development, economics and global warming potential of lignocellulose biorefinery

Abstract: Depletion of fossil fuel and climate change crisis are two of the greatest challenges we are facing and have sparked great interest in searching for renewable energy resources. Lignin has been considered as one of the best renewable energy sources to meet this growing energy demand while mitigating greenhouse gas emissions. This chapter will review the structural characteristics of lignin as well as three main types of lignin conversion processes, i.e. thermochemical conversion, catalytic chemical depolymerization, and biological depolymerization. The economics and global warming potential of lignin-related biorefinery processes and systems will also be discussed.