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Letter to the Editor

Response to comments for thermal explosion and runaway reaction simulation of lauroyl peroxide by DSC tests

Journal of Thermal Analysis and Calorimetry
Authors: M.-L. You and C.-M. Shu
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Five giant embryo mutants, described as MH-gel, MH-ge2, MH-ge3, MH-ge4 and MH-ge5 , which were derived from the same indica rice cv . ‘Minghui 86’ and characterized by 2.0, 1.88, 2.08, 1.93 and 1.88 times enlarged embryo than that of wild type, were selected for the current study. The mutated giant embryos were controlled by a single recessive gene, and except mutated locus with MH-ge1 other four loci were allelic to each other and the previous reported locus ge in japonica rice cv . ‘Kinmaze’. No obvious differences in physicochemical properties such as apparent amylose content (AAC), alkali spreading value (ASV), gel consistency (GC), and starch paste viscosity were observed between giant embryo mutants and wild type. Significant increases in the contents of crude lipid (LC), crude protein (PC), Vitamin B1 (V B1 ), Vitamin B2 (V B2 ), Vitamin E (V E ), essential amino acids such as Arginine (Arg), Aspartic acid (Asp), Glutamic acid (Glu), Lysine (Lys), Methionine (Met), and mineral elements such as calcium (Ca), iron (Fe), potassium (K), phosphorus (P) and zinc (Zn) were detected in brown rice (BR) of giant embryo mutants. The amounts of gamma aminobutyric acid (GABA), an inhibitory neurotransmitter, were similar in the BR of giant embryo mutants and wild type, and more GABA content was observed in germinated brown rice (GBR) than BR. Significant enrichments were detected in the GBR of giant embryo mutants, basically corresponding to the enlarged embryo.

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Abstract  

Due to the experimental errors, the chemical effect of minor reactions, and some physical effects of heat and mass transfer, there usually exists much noise in the mass loss data resulted from thermal decomposition experiments, and thus high quality smoothing algorithm plays an important role in obtaining reliable derivative thermogravimetric (DTG) curves required for differential kinetic analysis. In this paper three smoothing methods, i.e. Moving Average smoothing, Gaussian smoothing, and Vondrak smoothing, are investigated in detail for pre-treatment of biomass decomposition data to obtain the DTG curves, and the smoothing results are compared. It is concluded that by choosing reasonable smoothing parameters based on the spectrum analysis of the data, the Gaussian smoothing and Vondrak smoothing can be reliably used to obtain DTG curves. The kinetic parameters calculated from the original TG curves and smoothed DTG curves have excellent agreement, and thus the Gaussian and Vondrak smoothing algorithms can be used directly and accurately in kinetic analysis.

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Abstract  

Hydrogen peroxide (H2O2) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition reaction of H2O2 mixed with sulfuric acid (H2SO4) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic onset temperature (T 0), heat of decomposition (ΔH d), pressure rise rate (dP/dt), and self-heating rate (dT/dt), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations of H2SO4, the experimental data of T 0, ΔH, dP/dt, and dT/dt were obtained. Comparisons of the reactivity for H2O2 and H2O2 mixed with H2SO4 (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems.

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Abstract

Di-tert-butyl peroxide (DTBP) is an organic peroxide (OP) which has widespread use in the various chemical industries. In the past, thermal runaway reactions of OPs have been caused by their general thermal instability or by reactive incompatibility in storage or operation, which can create potential for thermal decomposition reaction. In this study, differential scanning calorimetry was applied to measure the heat of decomposition reactions, which can contribute to understand the reaction characteristics of DTBP. Vent sizing package 2 was also employed to evaluate rates of increase for temperature and pressure in decomposition reactions, and then the thermokinetic parameters of DTBP were estimated. Finally, hazard characteristics of the gassy system containing DTBP, specifically with respect to thermal criticality, were clearly identified.

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Summary

Supercritical fluid extraction (SFE) was used to extract shionone from Aster tataricus L. f. The effect of various parameters, i.e., temperature, pressure and sample particle size on yield was investigated with an analytical-scale SFE system to find the optimal conditions. The process was then scaled up by 50 times with a preparative SFE system under the optimized conditions of temperature 40 °C, pressure 30 MPa, and a sample particle size of 40–60 mesh. Then preparative high-speed counter-current chromatography was successfully used for isolation and purification of shionone from the SFE extract with a two-phase solvent system composed of n-hexane-methanol (2:1, volume ratio). The separation produced a total of 75 mg of shionone from 500 mg of the crude extract in one step separation with the purity of 98.7%, respectively, as determined by high-performance liquid chromatography (HPLC) and 92% recovery. The structure of shionone was identified by electrospray ionization-mass spectrometry (ESI-MS), hydrogen-1 nuclear magnetic resonance (1H-NMR), and carbon-13 nuclear magnetic resonance (13C-NMR).

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Abstract  

In industrial processes, information on the safety property of chemicals is essentially crucial for safe handling during unit operations. Ensuring the safe use of combustible or flammable substances in processes is unlikely without detailed investigations of their flammability characteristics and related hazards. We studied 3-methyl pyridine (3-picoline), e.g., flammability limits (LFL/UFL), maximum explosion pressure (P max), maximum explosion pressure rise (dP/dt)max, minimum oxygen concentration (MOC), vapor deflagration index (K g), and characterized the influence of inert steam (H2O) on critical parameters for 3-picoline/water mixtures at 270C, 1 atm, various oxygen concentrations, and vapor mixing ratios (100/0, 30/70, 10/90 and 5/95 vol.%) with a 20-L-Apparatus in simulated conditions, respectively. The results showed that the flammability characteristics of 3-picoline(aq) all increased with the oxygen concentration. However, as the composition of inert steam increased, the flammability parameters and the degree of fire and explosion hazards were significantly reduced, instead. This study elucidated the flammability properties of 3-picoline mixed with inert steam. The conclusions could be applied to proactively prevent the relevant processes from incurring fire and explosion accidents.

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The present study was to evaluate the survival rate of free and encapsulated Bifidobacterium bifidum BB28 under simulated gastrointestinal conditions and its stability during storage. Results showed that non-microencapsulated Bifidobacterium bifidum BB28 was more susceptible to simulated gastrointestinal conditions than microencapsulated bacteria. Microencapsulated Bifidobacterium BB28 exhibited a lower population reduction than free cells during exposure to simulated gastrointestinal conditions, the viable count of monolayer microcapsules, double layer microcapsules, and triple layer microcapsules decreased by nine magnitudes, four magnitudes, and one magnitude after 2 h, respectively. The enteric test showed that the microorganism cells were released from the monolayer, double layer, and triple layer microcapsules completely in 40 min. Moreover, the optimum storage times of free Bifidobacterium BB28, monolayer microcapsules, double layer microcapsules, and triple layer microcapsules were 21 days, 21 days, 28 days, and more than 35 days in orange juice, pure milk, and nutrition Express (a commercially available milk based drink), and the viable counts were maintained at 1×106 CFU g−1 or more, which means that the double layer and triple layer of microcapsules of B. bifidum BB28 have great potential in food application.

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