Elucidating The Thermal Decomposition Mechanism and Pyrolysis Characteristics of Biorefinery-Derived Humins From Sugarcane Bagasse And Rice Husk

Biomass-derived humins produced in the biorefining of biomass represent an attractive feedstock for thermochemical processes and other carbon-derived platform chemicals. However, in most works, humins are merely a by-product that is not further analyzed. This work presents the purification and characterization of humins derived from sugarcane bagasse and rice husks (H-SCB and H-RH respectively), followed by the kinetic and thermodynamic analysis of its pyrolysis. Pyrolysis was examined via thermogravimetric analysis (TGA), and a global reaction model was adopted to address pyrolysis kinetics. To understand the pyrolysis process of humins and boost the quality of fit between the kinetic model and thermoanalytical data, the analyses were based on the Vyazovkin isoconversional method. The activation energy of H-SCB increased from 166.09 to 329.76 kJ mol-1. In contrast, the activation energy of H-RH decreased from 163.31 to 84.99 kJ mol-1. According to the results of the generalized master plot approach, the governing reaction mechanism shifted among order-based models, nucleation, and diffusion-controlled particle mechanisms. Derived thermodynamic properties showed that the heat absorbed helps the humins to achieve a more ordered state close to a conversion of 0.50. As far as we know, these findings are the first reported data on the forecast kinetic curves and pyrolysis mechanism of biorefinery-derived humins from sugarcane bagasse and rice husk, and these results will enable process design for the thermochemical conversion of these emerging materials to produce energy and other products.

Enhanced decomposition of laminated ammonium perchlorate composite

In order to improve the thermal decomposition performances of ammonium perchlorate (AP), the laminated AP composite was prepared by ice-template induced self-assembly method. In this study, Iron-Konjac glucomannan (Fe3+-KGM) hydrosol rich in AP was selected as the freezing precursor. Through directional freezing of precursor and recrystallization of AP molecules, the laminated AP composite was obtained. The results showed that the thickness of the lamellar composite structure is about 10 to 30 μm, and the recrystallized AP particles are uniformly dispersed in the gel system. The oxygen bomb test results show that the micro-/nano-layered structure can significantly improve the sample’s combustion heat value. Thermal analyses indicated that with the increasing Fe3+ content, the peak exothermic temperature of lamellar AP composite at different heating rates both showed a decreasing trend. With 10 wt% Fe(NO3)3·9H2O added, the decomposition peak temperature decreased from 433.0 to 336.2 °C at a heating rate of 5 °C/min, and the apparent activation energy (Ea) decreased dramatically from 334.1 kJ/mol to 255.4 kJ/mol. A possible catalytic thermal decomposition mechanism of lamellar AP composite catalyzed by Fe3+ was proposed. This work is beneficial to the structural design of other energetic materials.

Five Dinuclear Lanthanide Complexes Based on 2,4-dimethylbenzoic Acid and 5,5′-dimethy-2,2′-bipyridine: Crystal Structures, Thermal Behaviour and Luminescent Property

A series of new complexes, [Ln (2,4-DMBA)3(5,5′-DM-2,2′-bipy)]2 (Ln = Sm(1), Eu (2)), [Pr (2,4-DMBA)3 (5,5′-DM-2,2′-bipy)]2·0.5(C2H5OH) (3), [Ln (2,4-DMBA)3 (5,5′-DM-2,2′-bipy)]2·0.5(2,4-DMBAH)·0.25(5,5′-DM-2,2′-bipy) (Ln = Tb (4), Dy (5)) (2,4-DMBA = 2,4-dimethylbenzoate, 5,5′-DM-2,2′-bipy = 5,5′-dimethy-2,2′-bipyridine) were synthesized via hydrothermal reaction conditions. The complexes were characterized through elemental analysis, Infrared spectra (IR), Raman (R) spectra, UV-Vis spectra, single X-ray diffraction. Single crystal data show that complexes 1–5 are binuclear complexes, but they can be divided into three different crystal structures. The thermal decomposition mechanism of complexes 1–5 were investigated by the technology of simultaneous TG/DSC-FTIR. What’s more, the luminescent properties of complexes 1–2 and 4 were discussed, and the luminescence lifetime (τ) of complexes 2 and 4 were calculated.

Decomposition of Waste Shells Using Multi-Complex Microorganisms

Objectives : Korea is a global aquatic product producer/consumer country, and shellfish including oysters are no exception. Oysters occupy the largest proportion as a single variety in the domestic aquaculture industry. The production volume reaches an average of more than 300,000 tons per year. The oyster shells left after harvesting oyster is reaching over 280,000 tons/yr. About 70 % of these are recycled, but the remaining shells which are over 60,000 tons, causing serious environmental problems such as odor and water pollution. In order to solve this problem, some local governments investigated the possibility of applying microorganisms, but it was effective only to remove odors and it was not possible to decompose the oyster shell itself. In this study, an attempt was made to solve the problem of waste shell decomposition by using multi-complex microorganisms rather than microorganisms composed of a few species.Methods : As a waste food extinction facility in Korea, the first certified Q mark equipment was used. After mixing oyster shells and food wastes in a 1:1 ratio, they were subjected to decomposition and extinction treatment at a high temperature of 80 ℃ using multi-complex microorganisms. Multi-complex microorganisms are composed of various soil microorganisms, including aerobic and anaerobic microorganisms. They are in an activated ecosystem by forming a symbiotic relationship to obtain a strong decomposition synergistic effect.Results and Discussion : The composition of complex microorganisms was mainly Firmicutes at the beginning, but Proteobacteria accounted for a half after 29 hours from the start of the experiment, and after 77 hours, it was shifted to Firmicutes A. All-organic components were decomposed within 72 hours, and the shell was changed to a powder form, and the total weight was reduced to less than 10% of the input total weight. It was found that treatment for at least 48 hours was required to decompose organic components from food waste, and after the organic components were decomposed, oyster shells were transformed into fine particles. The main components of the particles were calcium carbonate, which was identified as Aragonite and Calcite.Conclusions : Considering that the main component of the shell is calcium carbonate, and the temperature at which calcium carbonate is decomposed into quicklime and carbon dioxide is around 800 ℃, the result of weight loss of the shell is difficult to explain with the existing thermal decomposition mechanism. It is necessary to explore further a new possible mechanism of shell decomposition by complex microorganisms.

Molecular dynamics simulation of initial thermal decomposition mechanism of DNTF

In order to understand the thermal decomposition characteristics of 3,4-Bis(3-nitrofurazan-4-yl)furoxan (DNTF), the thermal decomposition reaction of DNTF at 300-4000K temperature programmed and constant temperature of 2000K, 2500K, 3000K, 3500K and 4000K was simulated by ab initio computational molecular dynamics method. The thermal decomposition mechanism of DNTF at different temperatures was analyzed from the aspects of product evolution, cluster, potential energy curve and reaction path. The analysis of products, show that the initial small molecular products are NO, NO2, CO, CO2 and N2, and the final small molecular products are CO2 and N2. In the early stage, the ring-opening reaction of furoxan in DNTF structure is the main trigger reaction, and the C-C bond is broken at the initial stage of reaction. The carbon chain structure produced by decomposition forms various cluster structures in the form of C-N bond. In addition, it was found that temperature significantly affects the decomposition rate of DNTF, but does not change its initial decomposition path.