Reactants environmentally friendly

Benson and Ponton propose, based on this analysis, the concept of distributed manufacturing [139, 145], which will be referred to in detail in Volume 2 of this book series. Basically, they refer to small, transportable plants which are fed with reactants over the fence , hence using only non-hazardous, generally available materials by normal piping or standard transport. If an aggressive chemical is needed, it has to be made from environmentally friendly base materials as an intermediate on-site. Needless to say, effluents have to be completely harmless, plant operation has to be intrinsically safe, and the plant should be clean and quiet. 

In summary, water appears as an extremely unsuitable solvent for coordination of hard Lewis acids to hard Lewis bases, as it strongly solvates both species and hinders their interaction. Hence, catalysis of Diels-Alder reactions in water is expected to be difficult due to the relative inefficiency of the interactions between the Diels-Alder reactants and the Lewis acid catalyst. On the other hand, the high stereoselectivities and yields observed in biosyntheses, with water as the solvent, indicate that these rationalizations cannot entirely be true. As a matter of fact, we will demonstrate in the following that Lewis acid catalysis in water is not only possible, but also allows for effective as well as environmentally friendly reaction conditions. 

Some most important solvent-free routes for selective oxidations of hydrocarbons and aromatics [9], hydrogenations [10], and for a one step production of e-caprolactam from cyclohexanone with a mixture of air and ammonia using porous heterogeneous catalysts have been reported, in which the active sites have been atomically engineered [11]. There are also reactions in which at least one reactant is liquid under the conditions employed, which means the solvent normally used can simply be left out. To begin with, two industrially important examples are discussed, which confirm that a reaction process that is more environmentally friendly can also be economically very acceptable. This is followed by some recent examples of solvent-free reactions covering a remarkably broad range of reaction types in which the term solvent-free refers solely to the reaction itself. On the other hand, workup processes, except for a few examples, invariably involve the use of solvent. The... 

In order to increase the sustainability of chemical processes, environmentally friendly solvents such as supercritical fluids (SCFs) are widely investigated. Han and coworkers studied the ethenolysis of ethyl oleate in SC C02 in relation with the phase behavior of the reaction mixture [62]. They carried out the ethenolysis reaction at 35°C in the absence of C02 and in the presence of C02 at three different pressures (50, 82, and 120 bar). The reaction in the absence of C02 reached equilibrium in 1 h at 80% conversion. The reaction rate in the presence of 50 bar of C02 was higher than without C02 and, at 82 bar, again increased with respect to 50 bar. However, when the pressure was increased to 120 bar, the reaction rate decreased. This effect was explained according to the variations on the phase behavior with the pressure an increase in the C02 pressure carried an increase of solubility of reactants, products, and C02, which produced a decrease of the viscosity of the reaction mixture. This positive effect was enhanced at 82 bar and was accompanied by an increase of selective solubility of the products in the vapor phase that further increased both reaction rate and conversion. The decrease of efficiency at 120 bar was related to an increase of the solubility of the reactants in the C02 phase. 

The hydroacylation of olefins with aldehydes is one of the most promising transformations using a transition metal-catalyzed C-H bond activation process [1-4]. It is, furthermore, a potentially environmentally-friendly reaction because the resulting ketones are made from the whole atoms of reactants (aldehydes and olefins), i.e. it is atom-economic [5]. A key intermediate in hydroacylation is a acyl metal hydride generated from the oxidative addition of a transition metal into the C-H bond of the aldehyde. This intermediate can undergo the hydrometalation ofthe olefin followed by reductive elimination to give a ketone or the undesired decarbonyla-tion, driven by the stability of a metal carbonyl complex as outlined in Scheme 1. 

All these aspects were thoroughly discussed by lecturers and participants during the round table organized during the Poitiers School on The Future Trends in Zeolite Applications . Special emphasis was placed on the role played by the sites at the external surface (pockets, etc.) or at the pore mouth, by mesopores, extraframework aluminum species, as well as by the polarity of reactant and product molecules. Other important topics dealt with the remarkable catalytic properties of BEA zeolites for fine chemical synthesis, the potential of mesoporous molecular sieves, zeolitic membranes and the role of combinatorial catalysis in the development of zeolite catalysts. It is our hope that the fruits of these discussions will appear in the literature or even better as new and environmentally friendly products or processes. 

Most processes involve a recycle stream. The reason is that all the reactants do not react, and businesses cannot afford to throw the rest away. Furthermore, any leftovers have to be disposed of in an environmentally friendly manner, which costs money. Thus, engineers take the unreacted reactants and put them back in the start of the process and try again. This makes the mass balances a little more complicated, and it leads to iterative methods of solution, which are described in this chapter. The hrst part of this chapter uses Excel to solve mass balances with recycle streams. Situations in which the energy balances affect the mass balance are treated in Chapters 6 and 7, because these are best done using a process simulator such as Aspen Plus . 

The unique selling proposition of the tandem-assembly process is its contribution to the field of green chemistry in obtaining closed-shell colloidal structures through an environmentally friendly route, as the entire synthesis is carried out in water, at near neutral pH, and at room temperature. Further, the size of the colloidal template can be controlled by the charge ratios of reactants, which results in structures with sizes ranging from 100nm to 2p,m [32-35,80,81]. 

Higher concentration and higher temperature can accelerate the formation of the polymer wall, but the reaction rate is also controlled by the reactants diffusion. Some organic solvents like chloroform and toluene were employed to improve the diffusion. But for industry practice, Norpar, vegetable oil, etc., are more environmental friendly and cost effective. Each oil droplet dispersed in the water phase can be treated as a tiny reactor since the interfacial polymerization only happens at the interface between the water and oil. Therefore, the smaller oil droplet size means higher reaction rate. ... 

The chemical equilibria of many industrially important organic reactions in aqueous solutions are often displaced in the direction of the reactants, leading to very low conversions. Therefore, there is a need for an environmentally friendly strategy that will shift the equilibria toward the products, resulting in enhanced conversions. A particularly effective technique is to add a second phase, appropriately termed biphasing. 

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