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B0561 - New probes for an accurate calorimetric determination of the acidity of zeolites
A. Auroux, Innovation in Zeolite Material Science, 385-391
B0559 - Acidic ferrierite type zeolite - II Steamed and acid leached treatment
Ferrierite type zeolite was thermally treated under steam at temperatures ranging from 870 to 970 K followed by acid leaching with hydrochloric acid solution at 360 K. It was observed that framework aluminium was extracted from the lattice but remained within the pores and channels. A decrease in the number but not the strength of acidic sites followed with a subsequent decrease of catalytic activity and of lifetime on stream. The changes in sorptive properties (diffusivity, capacity) were rather minor for n-hexane and 3-methylpentane adsorbates but very important for toluene. The steamed materials appeared to present no additional interest as acid type catalysts but to be more selective for aromatics diffusion, i.e. as separating columns or adsorbants.
Y.S. Jin, A. Auroux and J.C. Vedrine, Applied Catalysis 37 (1988) 21-33
B0558 - Acidic ferrierite type zeolite - I Physicochemical and catalytic properties
Ferrierite samples with two aluminium contents (silicon:aluminium = 15.4 and 7.8) were synthesized and acidified through NH+4 exchange. One sample was pure ferrierite whereas the second was a mixed ferrierite+mordenite phase. Because of its small pore channel structure the ferrierite exhibits striking shape selectivity properties for n-hexane cracking and methanol conversion reactions. Acidic properties, as evidenced by infrared and microcalorimetry techniques, of ammonia adsorption correspond to strong acidity. The intimate presence of mordenite in one sample results in severe limitation of the adsorption and diffusion properties and subsequently to higher shape selectivity and also to fast deactivation versus time-on-stream. This is interpreted in terms of intergrowths of ferrierite and mordenite phases.
Y.S. Jin, A. Auroux and J.C. Vedrine, Applied Catalysis 37 (1988) 1-19
B0557 - Calorimetric investigation of the effect of dealumination on the acidity of zeolites
Calorimetric investigation of NH3 adsorbed on a variety of dealuminated Y and mordenite zeolites showed a drastic change of the initial values and coverage dependance of differential heats of adsorption. These changes were interpreted in terms of the presence within the zeolite porous matrix of an alumina type phase which is behaving as an additional acidic component.
A. Auroux and Y. Ben Taarit, Thermochimica Acta 122 (1987) 63-70
B0556 - Direct calorimetry on free swimming goldfish at different oxygen levels
Heat production and oxygen consumption of groups of fasting, dark acclimated free swimming goldfish were measured at 20 ~ during normoxia and anoxia. For this purpose a special 1 liter flow through microcalorimeter was constructed. It appeared that the normoxic values could be established at any time 2 days after introduction of the fish into the calorimeter, 700 j/h/MW and 1.6 mmoles/h/MW respectively. The normoxic oxycalorific value of 20 kJ/l 02 indicates the use of a mixed substrate for oxidation. During anoxia, heat production was reduced to 30% of the normoxic level; 200 J/h/MW.
J. van Waversveld, A.D.F. Addink, G. van den Thillart, H. Smit, Journal of Thermal Analysis 33 (1988) 1019-1026
B0555 - Flow adsorption calorimetry with supercritical fluids on silica gel
Although the thermal curves given by a Calvet calorimeter can be considered representative of the thermogenesis of slow phenomena, this is not the case for the brief thermal effects of dissolution, for example, which need typically no more than twenty minutes. At high temperatures, a numerical method of deconvolution of the recorded signal was applied in order to obtain the proper thermogenesis of the phenomenon. The time constants of the calorimeter were determined from thermal effects due to the dropping into the bath of small quantities of silver and platinum. The method was applied to the dissolution of s-alumina and industrial aluminas in cryolithic baths at 1290 K. The different kinds of alumina could be classified according to their time of dissolution. The dependence of the alumina concentration of the bath on the dissolution rate was also investigated.
E.M. Arnett, B. Chawla, E.A. Dwyer, C.H. Lochmüller, Journal of the American Chemical Society 107 (1985) 2552-2553
B0554 - New experimental vessels for the C 80 calorimeter
L. Benoist, Thermochimica Acta 119 (1987) 223-224
B0552 - A study of thermal behaviour of sodium and zinc diphosphates
Phase transitions in Na4P2O7, Zn2P2O7 and Na2ZnP2O7 in the temperature range 20-800°C have been studied by X-ray diffraction, high-temperature microscopy, electrical conductivity, differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Na4P2O7 has five reversible polymorphic transformations at 402.7, 512.0, 518.3, 542.7 and 554.4°C, respectively. Zn2P2O7 undergoes one reversible polymorphic transformation at 128.2°C. In the studied temperature range Na2ZnP2O7 does not exhibit polymorphism and melts congruently at 779.0°C. The enthalpies of phase transitions have been determined by DSC method.
V.B. Lazarev, I.D. Sokolova, G.A. Sharpataya, I.S. Shaplygin and I.B. Markina, Thermochimica Acta 86 (1985) 243-249
B0551 - Effect of heating rate and sample size on heat transfer through the sample in DSC
As it is very often the first step of the process, heat transfer plays an important role, especially for systems heated in scanning mode. The problem is studied in the simple case when no reaction occurs. In the present case, heat is transferred through the cross-section of a cylinder heated on faces with a constant heating rate. The gradients of temperature through the sample when they are established are proportional to the heating rate on faces and to the square of the diameter of the cylinder. The shape of the gradients of temperature are obtained at different times when these gradients are not established and when they are constant. The heat flux emitted through the face-calorimeter interface are also determined. The value of heat flux is certainly the best parameter for testing the validity of the model.
J.Y. Armand, R. Gonnet, R. Jones, J. Bouzon, M. Touchard and J.M. Vergnaud, Thermochimica Acta 103 (1986) 341-351
B0550 - Enhanced study of differential scanning calorimetry with determination of heat flux-time curves, profiles of temperature and state of cure
Differential scanning calorimetry is studied by considering the case of cure of an epoxide resin with a high enthalpy. In order to enhance this method, the heat flux due to heating of the cure reaction, and that evolving through the holder-calorimeter interface are calculated as a function of time. Simultaneously, the profiles of temperature and state of cure are determined, as they are developed through the sample during the heating. These calculations have been possible by applying our previous model taking into account heat transfer and the kinetics of heat evolved by the cure reaction. The effect of two parameters is especially considered: the heating rate, and the quality of contact between holder and the calorimeter. The higher the heating rate, the higher the gradients of temperature through the sample. Fortunately, the other, new parameter only affects the sensitivity of heat flux-time curves, it does not modify their shape, and so does not alter the following kinetic treatment.
M. Chater, G. Chataing and J.M. Vergnaud, Thermochimica Acta 90 (1985) 135-147
B0549 - Thermal analytical investigations on (AgNa)-A zeolites
During the thermal treatment of silver-exchanged forms of zeolite A, five desorption effects are observed which are assigned to different adsorption forms of water. Dehydration (of water) is accompanied by autoreduction of some of the silver ions. The water adsorption capacity of the (AgNa)-A zeolites depends upon the degree of autoreduction and reduction in hydrogen, respectively. It is possible to suppress the autoreduction by heating in oxygen. With increasing content of silver ions the thermal stability of the samples is decreased. The same was observed after successive reduction in hydrogen.
B. Wolf, H. Siegel, R. Schollner and A. Dyer, Thermochimica Acta 87 (1985) 117-127
B0548 - Review of some metallurgical problems suitable for quantitative calorimetric treatment
A review is given of various metallurgical problems treated in the author's laboratory, for which quantitative calorimetry gave very valuable information. Measurements of thermodynamic data for phase diagram calculations, vacancies in ordered alloys, annealing of steels, and the recovery and crystallization of amorphous alloys are successively examined.
J. Hertz, Journal of Thermal Analysis 30 (1985) 1227-1240
B0547 - Adsorption at the liquid/solid interface : the part of microcalorimetry in the fields of enhanced oil recovery, lubrication and water purification
After listing the problems of adsorption which are more specifically related to each of these three fields, typical results obtained by liquid/solid adsorption microcalorimetry are reported and commented on. Batch adsorption microcalorimetry is shown to be especially interesting as a sensitive detector to follow the kinetics of adsorption whereas liquid-flow adsorption microcalorimetry -although less universal- is a more convenient tool for a preliminary screening of the systems and also to study desorption.
J. Rouquerol, Thermochimica Acta 95 (1985) 337-350
B0546 - Experimental study on baseline drifts of a Tian-Calvet type calorimeter
The stability of a Tian-Calvet type calorimeter used in enthalpy of solution determinations has been analysed. The mechanical action necessary for starting the solution process causes a permanent drift on the baseline. The influence on the total energy involved in a solution process has been quantitatively determined by a series of blank experiments (without real solution process). As a result of this experimental study a baseline correction method is proposed.
A. Sanahuja, Thermochimica Acta 90 (1985) 9-14
B0545 - Enthalpy of solution of aqueous sodium chloride at 303.15, 308.15, and 313.15 K
The enthalpies of solution of NaCl in water at 303.15, 308.15, and 313.15 K have been measured as a function of molality in a heat-flux calorimeter. The covered range is 0.005 to 0.12 mol.kg-1. Values for the apparent relative molar enthalpies have been used to analyse the experimental results. The enthalpies of solution at infinite dilution at 303.15, 308.15, and 313.15 K obtained are 3.32, 2.78, and 2.25 kJ.mol-1, respectively
A. Sanahuja and E. Cesari, J. Chem Thermodynamics 17 (1985) 823-827
B0544 - Excess enthalpies of some n-alkanals with benzene, tetrachloromethane and n-chloroalkanes
A Tian-Calvet-type calorimeter has been used to-determine molar excess enthalpies at 298.15 K as a function of concentration for the following binary mixtures: ethanal, propanal, butanal or pentanal + 1-ehloropropane, 1-chlorobutane, 1-chloropentane and l-chlorohexane. These data are examined on the basis of a quasi-chemical theory using group-surface interactions.
B. Marongiu, Journal of Thermal Analysis 30 (1985) 1387-1392
B0543 - Conformational transition of kappa-carrageenan
The calorimetry of kappa carrageenan using differential scanning calorimetry and calorimetry at constant temperature is presented. Both sets of experimental results confirmed the formation of a helical dimer in the absence of gel formation. When gel is formed, the formation of a helical dimer is the major effect, the contribution of gelation represents only 20% of the enthalpy recorded.
C. Rochas, Journal of Thermal Analysis 30 (1985) 1375-1380
B0542 - Thermodynamics of binary mixtures containing aldehydes. Excess enthalpies of n-alkanals + benzene and + tetrachloromethane mixtures
Molar excess enthalpies HE have been measured as a function of mole fraction at atmospheric pressure and 298.15 K for the binary liquid mixtures of ethanal, propanal, butanal and pentanal + benzene or + tetrachloromethane. The results show that the excess enthalpies decrease with increasing the n-alkanal chain length, with negative values for n-pentanal.
B. Marongiu, Thermochimica Acta 95 (1985) 105-110
B0541 - Excess enthalpies of (n-alkanol + ethyl ethanoate or ethyl propanoate) at 298.15 K
The excess molar enthalpies HmE of various binary liquid mixtures of (an n-alkanol + an ester) have been determined at atmospheric pressure and 298.15 K using a Calvet microcalorimeter. A variable-degree polynomial has been fitted to the results, which have been interpreted in terms of a "free-volume" model.
J.M. Navarro, M. Baloira, R. Bravo, M.I. Paz Andrade and M. Pintos, J. Chem. Thermodynamics 17 (1985) 447-451
B0540 - Study of the combustion of a fire retardant coating by thermal analysis and different complementary techniques
An intumescent fire retardant coating can effectively control fire spread and damage. Its dual purpose is to confine the surface spread of flame to the boundaries of an already established fire, and to retard the penetration of heat and flame to and through the coated surface. Our composition expanded and provided an insulation layer between the flame source and the combustion substrate, and liberated a quantity of primarily non-flammable decomposition products which tended to extinguish the flame. The main ingredients of the coating were cellulose acetate butyrate and HMDI (Desmodur N) for polyurethane, and Chlorowax-70 (chlorinated paraffins) as fire retardant component. This fire retardant coating was applied to wood panels, and tested in a 2-foot tunnel, its flame spread rating being measured. The effects of three parameters of interest were investigated: the type of wood used, the percentage of Chlorowax, and the coating thickness. It was found of interest to study the oxidation of the coating using different techniques, e.g. flash pyrolysis under oxygen and GC/MS for analysis of the decomposed products. Combustion studies of the coating were also conducted using DSC and thermogravimetry, either with the scanning mode or under isothermal conditions. Comparisons were made between the results obtained from pyrolysis and combustion.
V.M. Bhatnagar, J.C. David, J.M. Vergnaud, O. Riveros-Ravelo and H. Dieu, Journal of Thermal Analysis 30 (1985) 467-478
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