Fine chemicals lifetime

The scale of production of a fine chemical can range from a few t/a up to tens of kt/a. Two of the final intermediates in the synthesis of the world s top selling drug, the anticholesterol Lipitor , or atorvastin, are only produced on a scale of 500 t/a each. The consequence of the smaller scale and more specialist nature of these industries, is that the processes are far more likely to be batch or discontinuous. Thus process units will be flexible to produce more than one product and the product s lifetime in the market may be comparatively short, either for economic or performance reasons. However, product added value is high. 

Research and development in the field of fine chemicals differs considerably from bulk chemicals. Requirements for industrial success of a new process are different from bulk chemicals where the most important feature is cost performances. Although this feature is of course important for development of fine chemicals, two other main parameters should be considered. First of all, time to market One must be ready to manufacture the product at the right time and for a limited period of time. The lifetime of most fine chemicals is much shorter than for bulk chemicals where 20 to 50 years is standard. Second, possible R D expenses are much lower than for bulk chemicals (Figure 1). 

Most of the new developments in fine chemicals will come from small turnover products with short lifetimes and so short R D development times and low investment possibilities (Figure 2). 

Figure 2 Compared lifetimes and sales turnovers of fine chemicals versus bulk chemicals 1.2 Scientific Considerations...

Catalyst lifetimes are long in the absence of misoperation and are limited primarily by losses to fines, which are removed by periodic sieving. Excessive operating temperatures can cause degradation of the support and loss of surface area. Accumulation of refractory dusts and chemical poisons, such as compounds of lead and mercury, can result in catalyst deactivation. Usually, much of such contaminants are removed during sieving. The vanadium in these catalysts may be extracted and recycled when economic conditions permit. 

All nuclear multiplet structures due to coupling of nonequivalent nuclei are, as noted earlier, subject to effects on line shapes by chemical or positional exchange. For those multiplet structures arising from coupling of nuclei, one of which has a nonzero nuclear quadrupole moment, effects of quadrupole relaxation must be considered. For example, if a proton or fluorine atom is bonded to a nitrogen nucleus (I = 1), a triplet resonance will be expected in the proton or fluorine spectrum. For observation of this fine structure it is necessary that the lifetimes of the nuclear spin states of nitrogen (m = 1, 0, —1) be greater than the inverse frequency separation between multiplet components, i.e., t > l/ANx (106). The lifetimes of N14 spin states can become comparable to or less than 1 /A as a result of quadrupole relaxation. When the N14 spin-state lifetimes are comparable... 

Coalescenceis especially typical in concentrated emulsions. In such systems coalescence mainly determines the lifetime of emulsions prior to phase separation. In finely dispersed emulsions, both dilute and concentrated, the average size of drops may noticeably increase due to Ostwald ripening. At the same level of dispersion Ostwald ripening of emulsion droplets is a slower process than mass transfer of bubbles in foams [60]. This is due to a rather low interfacial energy, and consequently, low difference in chemical potentials of substance in droplets of different size, as well as due to a lower mutual solubility of liquids as compared to the solubility of gases in liquids. 

The lifetime of the emulsion (and the retention time in the full-scale separator) depends on the kind of stability mechanisms involved. There exist several possibilities of finding stabilizing agents (or solid fines) in either the crude oil itself or in added production chemicals. Among the indigenous stabilizers, asphaltenes/resins/ porphyrins are mentioned as possible candidates for the stabilization of... 

The mechanochemical treatment by ball milling is a very complex process, wherein a number of phenomena (such as plastic deformation, fracture and coalescence of particles, local heating, phase transformation, and chemical reaction) arise simultaneously influencing each other. The mechanochemical treatment is a non-equilibrium solid-state process whereby, the final product retains a very fine, typically nanocrystalline or amorphous structure. At the moment of ball impact, dissipation of mechanical energy is almost instant. Highly excited state of the short lifetime decays rapidly, hence a frozen disordered, metastable strucmre remains. Quantitative description of the mechanochemical processes is extremely difficult, herewith a mechanochemical reaction still lacks clear interpretations and adequate paradigm. 

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