Temperature of synthesis

Figure 3.2 Cooling Failure Scenario After a cooling failure, the temperature rises from process temperature to the maximum temperature of synthesis reaction. At this temperature, a secondary decomposition reaction may be triggered. The left-hand part of the scheme is devoted to the desired...

Maximum temperature of synthesis reaction (MTSR) this temperature depends essentially on the degree of accumulation of unconverted reactants and so is strongly dependant on process design. 

Moreover, reactor safety also requires fulfilling a more ambitious objective, that is, to design a reactor that will remain stable in case of mal-operation. The result will be a robust process towards deviations from normal operating conditions. This goal can be reached if the accumulation of non-converted reactants is controlled and maintained at a safe level during the course of reaction. The concept of maximum temperature of synthesis reaction (MTSR) was introduced for this purpose. This point will be described in the second section. In the... 

The maximum temperature of synthesis reaction was calculated for the substitution reaction example as a function of the process temperature and with different feed rates corresponding to a feed time of 2, 4, 6, and 8 hours. The straight line (diagonal in Figure 7.11) represents the value for no accumulation, that is, for a fast reaction. This clearly shows that the reactor has to be operated at a sufficiently high temperature to avoid the accumulation of reactant B. But a too high temperature will also result in a runaway due to the high initial level, even if the accumulation is low. In this example, the characteristics of the decomposition reaction... 

Figure 7.11 Maximum temperature of synthesis reaction occurring at stoichiometric point as a function of the process temperature TP, with different feed rates, = 2, 4, 6, 8 hours.

The descriptor was a product of the correlation weights, CW(Ik), calculated by the Monte Carlo method for each kth element of a special SMILES-like notation introduced by the authors. The notation codes the following characteristics the atom composition, the type of substance (bulk or not, ceramic or not), and the temperature of synthesis. The QSAR model constructed in this way was validated with the use of many different splits into training (n 21) and validation (n=8) sets. Individual sub-models are characterized by high goodness-of-fit (0.972 applicability domain of the model, it is not known if all the compounds (metal oxides, nitrides, mullite, and silicon carbide) can be truly modeled together. 

Fig. 9. Composition changes of catalyst D3001 with days of synthesis with IH2 + ICO gas at 7.8 atmosphere in test X218. Part A presents atom ratios of nitrogen, total carbon, elemental carbon, and oxygen to iron. Part B shows the distribution of iron as carbonitride and magnetite. Part C presents the temperatures of synthesis. Reprinted by permission of the American Chemical Society.

No. of experiment Chlorine-derivatives of hydrocarbons Taken, g/moles Mole ratio Period of synthesis, in minutes Temperature of synthesis, °C Output % AIH3 Type of AJH3 crystals Composition of product ... 

No. of test Haloid-derivatives of hydrocarbons Amount of tetrahydrofuran solution.... Concentration of solution M(A1H >2, g/1 Mole ratio Period of synthesis in minutes. Temperature of synthesis, °C Solution analysis Atomic ratio Al H ... 

Shortcomings of the method are the formation of large amounts of organic wastes and high temperatures of synthesis. The application of mechanical activation of solids allows to avoid liquid wastes during the synthesis and to decrease the temperature. 

The further researches have shown, that the temperature of synthesis and the nature of solid matrix render the appreciable influence on composition and structure of the oxide layer forming in the ML process. In Figure 9 the data on changes of titanium contents on silica and alumina surfaces in the ML process at the temperature of synthesis at the 200-600°C are shown. As results from the submitted dependencies, escalating... 

Increasing the temperature of synthesis results in enhanced crystallinity as would be anticipated because of improved reaction kinetics. However, this observation is also consistent with a crystallization mechanism involving solubility. Furthermore, as the temperature increases so does the equilibrium concentration of lead in solution thus with all else held constant, increased temperature of reaction results in a smaller lattice parameter for the product lead ruthenate pyrochlore. 

The Williamson synthesis in a two-phase system (water-alkaline medium, 70 °C, in the presence of various polyethylene glycols and their dibutyl or diethyl ethers as catalysts), has been described [81]. Also discussed was the effect of different catalysts, their amount, temperature of synthesis and ratio of reagents on the final product yield. 

Taking into account the fact that hydrothermal formation of carbon takes place at relatively low temperatures (200-800°C) and pressures (<100 MPa), this method seems to be very attractive. It has obvious advantages over the HPHT synthesis due to less extreme temperature-pressure conditions and the possibility of much larger pressure vessels, which would make the hydrothermal method attractive for industrial use. However, the temperature of synthesis should be decreased preferably to 200-250°C to make commercialization and up-scaling easier. 

In the work [1], the dependences of PHE synthesis main characteristics, namely, reduced viscosity tired and conversion degree Q, on synthesis temperature T were studied. It was found out, that T rising up to the definite limits influences favorably on the indicated process a reaction rate rises, ti and Q increase. This effect can be observed in the narrow enough range of T=333-348 K. At T lower than 333 K PHE formation process decelerates sharply, that is due to insufficient activity of epoxy groups at low temperatures. At T > 353 K cross-linking processes proceed, which are due to the activity enhancement of secondary hydroxyls in polymer chain [1]. It is also supposed [1], that at the indicated temperatures of synthesis PHE branched chains formation is possible. 

CaP synthesis methods and their technological parameters can significantly impact stoichiometry of the synthesis product, its grade of crystallization, particle size, bioceramic phase composition, thermal stability, microstructure and mechanical properties. The important technologic parameters that impact properties of calcium phosphate synthesis product and then also of bioceramic, are temperature of synthesis, pH of synthesis environment, reagent type and concentration, as well as selection of raw materials, their purity and quality. All of the above mentioned also brings a significant impact on the tissue response of these bioceramic implants. 

Parameters like water/surfactant molar ratio, the specific permittivity of the oil phase and temperature of synthesis were examined vis-a-vis their effect on the particle size. 

Table 19.2 shows the effect of temperature of synthesis of BN on various properties, namely, surface area, crystallinity, coefficient of friction, and oxygen content [40]. It may be noted that vhth increase in synthesis temperature, the coefficient of friction decreases. Typical properties of (h)BN relevant to its use as a filler are summarized in Table 19.1. 

The increase of the time of activation allows to reduce the temperature of sintering. Thus, the lowest temperature of synthesis was achieved in the case of LaCoOj (550 , activation of the starting mixtm for 30 min in El). 

Natural clays of TOT (2 1) or TO (1 1) structure are constituted of layers of Si04 tetrahedra (T) and NiOe octahedra (O) [15]. Synthetic clays corresponding to Si4Ni30io (OH)2(Ni talc, TOT phyllosilicate) and Si2Ni305(0H)4 (Ni serpentine referred to as nepouite, TO phyllosilicate) respectively, were hydrothermally synthesized in the 25-250 C range acconling to a procedure already described [16, 17]. These samples are referred to as Ta-x and Ne-x where Ta, Ne and x stand for talc, nepouite and the temperature of synthesis respectively. 

By contrast, the FT for the ill-ciystallized samples synthesized at 25°C are very similar (not shown here). Table 1 reports the simulation parameters for the next nearest backscatterers as a function of the temperature of synthesis. The results show a decrease of the number of Ni and Si backscatterers when the degree of crystallinity decreases. The difference between the number... 

As can be seen from Tables 2 and 4, there are several guest molecules which serve as SDA for different porosil structure types. The most sensitive synthesis parameter for the template efficacy is the temperature of synthesis. The space re-... 

The concentration of SDA in the synthesis solution has not been discussed so far. In most porosil syntheses, the synthesis solution is saturated with Si02 at the temperature of synthesis. The SDA concentration is important first for the nucleation process and, secondly, it is needed to maintain crystal growth. Whereas the nucleation of the porosil depends on the presence of an SDA, crystal growth of a stable crystallite might continue with only a fraction of cages occupied by SDA or help guest species. In this way, DOH membranes have been synthesized for the separation of hydrogen gas in gas mixtures [59]. 

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