Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Deanship of Scientific Research and Graduate Studies at King Khalid University[RGP2/121/1445]
No full textRelation between structural feature and non-ionic surfactant improving enzymatic hydrolysis of lignocellulose
No full textBlocking the unproductive adsorption of cellulase to lignin has been popularly thought to be the chief mechanism of non-ionic surfactant improving enzymatic hydrolysis of lignocellulose. This study, however, proposes a different viewpoint. Laccase and hemicellulase-xylanase (HXase) which respectively modify lignin and degrade hemicellulose were used to treat raw and ball-milled sugarcane bagasse (SCB). The treated SCB maintained similar relative lignin and hemicellulose contents as the untreated SCB. Laccase treatment resulted in wrinkles on the SCB micro-surface, while HXase treatment led to the formation of many pores in SCB. It found that Tween20, a kind of non-ionic surfactant, could obviously facilitate the adsorption of cellulase to untreated and treated SCB. It was completely opposite to the abovementioned popular mechanism. The enzymatic hydrolysis efficiencies of raw SCB treated by laccase and HXase, ball-milled SCB treated by laccase for 72 h and HXase for 24 h or 72 h, and ball-milled SCB treated by HXase for 24 h with Tween20 addition were 26.10%, 61.65%, 61.42%, and 70.86%, respectively, which had significant differences against those without Tween20 addition. Combined with surface structure observations, it hints that the enhancing effect of a non-ionic surfactant on the enzymatic hydrolysis of lignocellulose tends to depend on the lignocellulosic structural feature rather than lignin presence
The Study of Experimental Method on the Characterization of Acidic Properties of Zeolites by in Situ FTIR-Pyridine Adsorption
No full textZeolites are a class of solid acid catalysts with a wide range of applications in the current catalytic field due to their regular pore structure, large specific surface area, and efficient acidic properties. The catalytic reactivity of zeolites is closely related to their acidity. Accurately characterizing the acidic properties of zeolites is of great significance for establishing the structure-activity relationship between zeolite structure, acidity, and catalytic reaction performance. One of the most effective methods to characterize the type of acid centers and acid strength of zeolites is in situ infrared spectroscopy using pyridine as a probe molecule. First, this paper describes the experimental principles of in situ FTIR-pyridine adsorption method for characterizing the acidic properties of solid acid catalysts. Then, using ZSM-5 as a model, the in situ FTIR-pyridine adsorption was used to optimize the testing conditions for identifying the surface acidity of the zeolite and the effects of experimental conditions such as activation temperature, activation time, adsorption time of pyridine, desorption temperature and desorption time on the relevant FTIR characteristic peaks were investigated. The results showed that the optimal experimental conditions for the interaction between pyridine and acidic sites on zeolites were: activation temperature of 400 degree celsius, activation time of 60 min, adsorption time of 10 min at room temperature, desorption temperature of 150 degree celsius, and desorption time of 30 min. Under these experimental conditions, the pyridine was efficiently adsorbed with the acidic sites on the zeolites, and the intensities of the FTIR characteristic peaks corresponding to Bronsted and Lewis acids were saturated. Simultaneously, the interference of physical adsorption, hydrogen-bonded adsorption, and contaminants adhered to the sample surface on the adsorbed pyridine was effectively eliminated, and the optimal FTIR spectra were obtained with high repeatability. Finally, three modified zeolites, including Fe-ZSM-5, HZSM-5, and Na-HZSM-5, were characterized by optimized experimental methods, all of which obtained FTIR spectra with excellent quality, and the acid amount ratios of Bronsted acid to Lewis acid in agreement with the reports. The method improves the test efficiency and success rate. It excludes the relevant interference so that the measured information on the zeolites' acidity category, strength, and relative content is more accurate and reliable. Meanwhile, the optimized experimental method provides a reference for characterizing the acidic properties of other solid acid catalysts, which is of great significance in guiding the preparation and mechanism research of solid acid catalysts
Test Procedures and Mechanical Properties of Three-Dimensional Printable Concrete Enclosing Different Mix Proportions: A Review and Bibliometric Analysis
No full textThree-dimensional printable concrete (3DPC) has become increasingly popular in the building and architecture industries due to its low cost and fast design. Currently, there is great interest in the mix design methods and mechanical properties of 3DPC, particularly in relation to yield stress analysis. The ability to extrude and build 3D-printed objects can be significantly affected by factors such as the rate of extrusion, nozzle size, and type of pumps used. It has been observed that a yield stress lower than 1.5 to 2.5 kPa is not sufficient to maintain the shape stability of concrete, while a yield stress above this range can limit the material's extrudability. Furthermore, the strength properties of 3DPC are influenced by factors such as changes in yield stress and superplasticiser dosages. To meet the high mechanical strength and durability requirements of 3DPC in the construction industry, it is essential to analyse the material's early-age mechanical properties. However, the development of standardised test methods for 3DPC is still deficient. To address this issue, a bibliometric analysis was conducted to comprehensively review the diverse test methods and mechanical characteristics of 3DPC with different mix proportions. To produce high-performance concrete from various additives and waste materials, it is critical to have a basic understanding of the hydration processes of 3DPC. Moreover, a detailed analysis of the environmental impact and energy efficiency of 3DPC is necessary for its widespread implementation. This review article will highlight the recent trends, upcoming challenges, and benefits of using 3DPC. It serves as a taxonomy to navigate the field of 3DPC towards sustainable development
Fast co-pyrolysis characteristics of polyethylene terephthalate and epoxy resin from waste wind turbine blades
No full textThe present study systematically investigated the fast co-pyrolysis characteristics of epoxy resin and polyethylene terephthalate (PET) derived from waste wind turbine blades, with the aim of uncovering the possible synergistic effect in co-pyrolysis. The co-pyrolysis of epoxy resin and PET was beneficial to the formation of pyrolytic char, while the generation of small molecule gaseous products was restrained to a certain degree. The kinetic results revealed that the presence of epoxy resin dramatically reduced the energy barrier for PET decomposition into terephthalic acid (TPA) and vinyl benzoate via a cyclic transition state, finally resulting in an obvious reduction in the activation energy of the pyrolysis reaction. Remarkably, the activation energy for co-pyrolysis sharply decreased to around 150 kJ/mol at a low conversion rate. The co-pyrolysis presented a significant impact on the further transformation of primary pyrolysis products via decarboxylation, deoxygenation, decarbonylation, isomerization, and so on, thus contributing to the selective production of specified chemicals. Furthermore, the plausible reaction pathways and synergistic mechanisms between co-pyrolysis of epoxy resin and PET were discussed thoroughly
Experimental and process simulation on solid fuel chemical looping cascade utilization conversion technology aiming hydrogen generation
No full textIn this work, a novel chemical looping process towards hydrogen generation based on the cascade utilization of components in solid fuels (like biomass and coal) with different reactivity (pyrolysis gas and char) was proposed, aiming for energy conversion from carbon-intensive fuels to carbon-free renewable hydrogen via the material migration of iron oxides. Biomass, represented by sawdust, is an important part among various renewable energy sources and a typical solid fuel with great potential. Therefore, in the most concerned reduction stage, experiments were conducted mainly using sawdust to investigate the effects of various parameters (temperature, oxygen/fuel ratio, residence time) on the carbon conversion involved in char in the primary reduction stage, gas/ solid spatiotemporal distribution in the deep reduction stage and subsequent H-2 generation performance, and kinetic parameters were fitted for different reduction stages. Process simulation was further conducted based on the actual experimental results. The proposed process demonstrated satisfactory applicability to solid fuels with different characteristics, and biomass was more suitable for hydrogen production. Compared with chemical looping combustion process, a significant improvement of sawdust-fueled energy conversion efficiency from 33.26 % to 51.76 % and a decrease of OCs theoretical circulation rate (27.77 %) were achieved under the chemical looping process aiming hydrogen generation
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