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Abstract  

Aqueous leaching of tritium from silica gel, loaded by absorption of water vapor, makes part of reactor de-commissioning. It is found to follow the formulation of steady-state diffusion.

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Abstract  

Repeated irradiation enhances the precision and sensitivity of INAA based on short-live radionuclides, but entail systematic losses due to dead time. The relative standard deviation in the net peak area decreases with the square root of the number of cycles while the systematic bias increases with it. The limits of decision, detection and determination decrease in a somewhat more complicated way with the number of cycles. The derived formulation is applied to the determination of selenium in hair by the 161.9 keV photopeak of77mSe,T 1/2=17.8 s.

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Abstract  

Information about the kinetics and thermal decomposition of dicumyl peroxide (DCPO) is required for safety concerns, due to its wide applications and accident cases. To understand the inherent hazards during DCPO manufacturing, we selected various concentrations in different stages and analyzed them by differential scanning calorimetry (DSC). We evaluated thermokinetic parameters to set up a simple, but comprehensive kinetic model, with various tests conducted at heating rates of 2, 4, 6 and 10C min-1 . Subsequently, we established a more efficient, resource-effective, and cost-effective model of safety evaluation for DCPO with different concentrations, according to thermokinetic parameters, such as activation energy E a is 125.35 kJ mol-1 , frequency factor k 0 is 3.12410 12 s-1 , reaction order n is 0.9 and heat of decomposition ΔH is 750.52 J g-1 for DCPO 99 mass%.

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Abstract  

YBaCo4O7 compound is capable to intake and release a large amount of oxygen in the temperature range of 200–400°C. In the present study, the effect of Zn, Ga and Fe substitution for Co on the oxygen adsorption/desorption properties of YBaCo4O7 were investigated by thermogravimetry (TG) method. Due to fixed oxidation state of Zn2+ ions, the substitution of Zn2+ for Co2+ suppresses the oxygen adsorption of YBaCo4−xZnxO7. The substitution of Ga3+ for Co3+ also decreases the oxygen absorption capacity of YBaCo4−xGaxO7. This can be explained by the strong affinity of Ga3+ ions towards the GaO4 tetrahedron. Compared with Zn- and Ga-substituted samples, the drop of oxygen adsorption capacity is smallest for Fe-substituted samples because of the similar changeability of oxidation states of Co and Fe ions.

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Abstract  

In petrochemistry, dicumyl peroxide (DCPO) is used in various resins for improving physical properties, which was produced by cumene hydroperoxide (CHP) with oxidization reaction, redox reaction, and dehydration reaction. The reactant, CHP, is a typical organic hydroperoxide and has been intrinsically unstable and reactive due to its bivalent -O-O- structure which can be broken readily with bond-dissociation energy. This sequence on sensitive study aimed at the thermal hazard evaluation for the reactive and incompatible characteristics of CHP mixed with various inorganic alkaline solutions. Differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2) were used to analyze the thermal hazards and runaway reaction of redox system, such as decomposition of CHP in cumene solution and CHP react with inorganic alkaline solutions, exothermic onset temperature, peak power, heat of decomposition of dynamic scanning tests, adiabatic self-heating rate, pressure rise rate, maximum temperature, maximum pressure of reaction system, etc. The results of the tests have proven helpful in establishing safe handling, storage, transportation, and disposal guidelines.

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Abstract  

Cumene hydroperoxide (CHP) is classified as a flammable hazard in NFPA 43B. Fires or explosions induced by thermal hazards ascribed to the unstable hydroperoxyl or peroxyl groups are often reported. This sequence studies is aimed at the decomposition phenomena associated with the reactive and incompatible characteristics of CHP mixed with alkaline solutions. Various alkalines were used for comparing the relative impact of bases and effects on concentrations. Exothermic onset temperatures and heats of decomposition of these incompatible mixtures were performed by differential scanning calorimetry (DSC). Comparisons of exothermic onset temperature, peak power, heat of decomposition, etc., were assessed to verify the severity of incompatible hazards in these systems. When mixed with a small amount of the hydroxides (in the production or storage of CHP), CHP will be more labile or unstable because of lower exothermic temperature. In addition, to elucidate the final products and propose mechanisms of the reaction of CHP mixed with alkaline solution, the analytical results were carried out by GC/MS and IR. The exhibited reactivity was complicated and significantly affected by the alkaline solutions. The reaction schemes have been proposed in this study. These results are especially important in process safety design for producing CHP and its related compounds, such as phenol, α-cumyl alcohol (CA), acetophenone (AP), and dicumyl peroxide (DCPO).

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Abstract  

A differential scanning calorimetry (DSC) and thermal activity monitor (TAM) were used to study the thermo-kinetic parameters for dicumyl peroxide (DCPO) at various concentrations. The potential thermal hazards of intermediates and end products whose concentrations were at approximately 50, 70, 94 and 99.3 mass%, respectively, in the process of operating DCPO were investigated. Thermoanalytical curves indicate that the average heat of decomposition of various DCPO samples in a manufacturing process was 762 to 1200 J g -1 which made it an inherently hazardous material. In the incompatibilities study, significant thermal hazards appeared in the presence of H2SO4. From the TAM experiments, the synthetic process of DCPO could result in an unexpected reaction in the condition of batch addition with reactants and H2SO4.

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Abstract  

Soybean oil based polyols (5-OH polyol, 10-OH polyol and 15-OH polyol) were synthetised from epoxidized soybean oil. The melting peak of polyols and the relationship between melting peak and the number-average functionality of hydroxyl in polyols were investigated by differential scanning calorimetry (DSC). The thermal decomposition of polyols and some of their thermal properties by thermogravimetry (TG) and derivative thermogravimetry (DTG) were also studied. The thermal stability of polyols in a nitrogen atmosphere was very close hence they had a same baseplate of triglyceride for polyols. The extrapolated onset temperature of polyols in their thermal mass loss, first step had a decreasing order: 5-OH polyol>10-OH polyol>15-OH polyol due to the difficulty in forming multiple elements ring of them had the same order. The thermal behavior of polyols under non-isothermal conditions using Friedman’s differential isoconversional method with different heating rates indicated that the 5-OH polyol had the lowest activation energy in thermal decomposition amongst these polyols according to the same fractional mass loss because of the weakest intramolecular oligomerization. The 15-OH polyol was prior to reach the mass loss region because the six-member ring is more stable than the three-member ring from 10-OH polyol and more easily formed.

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Abstract  

Organic peroxides (OPs) are very susceptible to thermal sources, chemical pollutants or even mechanical shock. Over the years, they have caused many serious explosions. Cumene hydroperoxide (CHP) is widely employed to produce phenol and dicumyl peroxide (DCPO) in the manufacturing process. Differential scanning calorimetry (DSC) and thermal activity monitor (TAM) were employed to determine the potential thermal hazards and thermokinetic parameters (such as exothermic onset temperature (T 0), maximum temperature (T max), and enthalpy (ΔH)) of CHP mixed with sodium hydroxide (NaOH) and sulfuric acid (H2SO4). High performance liquid chromatography (HPLC) was used to analyze the concentration vs. time of CHP.When CHP is mixed with NaOH, the T 0 is induced earlier and reactions become more intricate than the pure CHP solution. CHP added to NaOH or H2SO4 is more dangerous than pure CHP alone. Depending on the operating conditions, NaOH and H2SO4 are the incompatible chemicals for CHP.

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Abstract  

The exothermic decomposition of cumene hydroperoxide (CHP) in cumene liquid was characterized by isothermal microcalorimetry, involving the thermal activity monitor (TAM). Unlike the exothermic behaviors previously determined from an adiabatic calorimeter, such as the vent sizing package 2 (VSP2), or differential scanning calorimetry (DSC), thermal curves revealed that CHP undergoes an autocatalytic decomposition detectable between 75 and 90°C. Previous studies have shown that the CHP in a temperature range higher than 100°C conformed to an n th order reaction rate model. CHP heat of decomposition and autocatalytic kinetics behavior were measured and compared with previous reports, and the methodology and the advantages of using the TAM to obtain an autocatalytic model by curve fitting are reported. With various autocatalytic models, such as the Prout-Tompkins equation and the Avrami-Erofeev rate law, the best curve fit among models was also investigated and proposed.

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