Process intensification advantages

Integration of the separation and reaction step has several advantages, but an inherent downside of such a process intensification step is the loss of degrees of freedom for process design and process control (Figure 10.9). 

As previously reported, membrane contactors present interesting advantages with respect to traditional units. Moreover, they well respond to the main targets of the process intensification, such as to develop systems of production with lower equipment-size/production-capacity ratio, lower energy consumption, lower waste production, higher efficiency. In order to better identify the potentialities of membrane contactors in this logic, they have been recently compared to traditional devices for the sparkling-water production in terms of new defined indexes [24]. In particular, the comparison has been made at parity of plant capacity and quality of final product. The metrics used for the comparison between membranes and traditional units are ... 

Emerging Greener Technologies and Alternative Energy Sources What are the advantages of microwave-assisted synthesis (57) How can electrochemical methods be applied to synthesis (52) How can sonochemistry be applied to synthesis How can reactions incorporate photochemical methods as an alternative energy source (55) What is process intensification ... 

There are several reasons for carrying out the reactions at supercritical conditions. Naturally, some of the reasons are coupled. Nevertheless, they, in general, relate to favorable transport properties, unique solvency characteristics, favorable kinetic considerations, and their sensitivity to operating conditions (manipulated variables). These unique properties lead to opportunities in process synthesis, process intensification, and controllability. These advantages, coupled with the environmentally friendly nature of these processes, make reactions in supercritical fluids attractive. The effect of these properties on opportunities for these favorable reaction environments is summarized in Table 1. 

Other industrial processes that have taken advantage of the process intensification deriving from the introduction of reactive (catalytic) distillation are (i) production of high purity isobutene, for aromatic alkylation (ii) production of isopropyl alcohol by hydration of propylene (iii) selective production of ethylene glycol, which involves a great number of competitive reactions and (iv) selective desulfurization of fluid catalytic cracker gasoline fractions as well as various selective hydrogenations. Extraction distillation is also used for the production of anhydrous ethanol. 

An approach to overcoming these problems, and which is directly linked to process intensification issues, is to combine microstructured reactor technology to photochemistry and photocatalysis [124,130]. Microstructured reactors have several possible advantages for photochemical processes [131] ... 

In the early days of microchannel development, the key selling point involved non-reactive applications, in particular heat transfer [1-12]. Work in this area quickly demonstrated that microchannel components could provide rapid heat transfer while maintaining low pressure drop, despite the use of very narrow process channels [1, 2], From there, microchannel research expanded to a range of non-reactive- and reactive-applications, where the major advantages of this technology not only included rapid heat and mass transfer but also the precise control of process conditions, low inventory of hazardous reactants, use of surface phenomena to significant advantage, and overall process intensification [13],... 

In many cases where mass transfer occurs between a liquid and a vapor, micro technology offers the advantage of process intensification through control of the liquid phase thickness. This intensification often occurs because the diffusivity is typically orders of magnitude lower in the liquid phase than in the gas phase hence, control of the liquid thickness decreases the primary impedance to mass transfer. This control benefits operations such as absorption and desorption, and processes based on these phenomena. 

There are distinct advantages of these solvent-free procedures in instances in which catalytic amounts of reagents or supported agents are used, because they enable reduction or elimination of solvents, thus preventing pollution at source . Although not delineated completely, reaction rate enhancements achieved by use of these methods may be ascribed to nonthermal effects. Rationalization of micro-wave effects and mechanistic considerations are discussed in detail elsewhere in this book [25, 244], There has been an increase in the number of publications [23c, 244, 245] and patents [246-256], and increasing interest in the pharmaceutical industry [257-259], with special emphasis on combinatorial chemistry and even polymerization reactions [260-263], and environmental chemistry [264]. The development of newer microwave systems for solid-state reaction [265], and introduction of the concepts of process intensification [266], may help realization of the full potential of microwave-enhanced chemical syntheses under solvent-free conditions. 

Fine chemicals are generally produced in large-scale batch reactors. However, in the past few years, a trend toward process intensification can be observed and more and more continuous production processes appear. Besides the advantage of a better reaction selectivity, these types of manufacturing processes also offer a lot of opportunities and challenges for engineers to combine continuous synthesis with a continuous purification method. 

Fractionation of liquid mixtures with supercritical carbon dioxide in counter-cur-rent columns can be operated continuously, because liquids can be easily pumped into and out of a column. This represents a big advantage over extrachon from solid materials, as it allows real process intensification - large quantities of feed can be processed with only a small volume under high pressure at any given time. Frac-tionahon, mostly of natural products or extracts, has been extensively studied at the laboratory and pilot-plant scale. The design principles of this type of column have been established, and scale-up procedures devised [1,6]. They can be operated with reflux, as in distillation, and frachonahon can therefore become an extremely se-lechve process. Difficult separahons can be effechvely carried out. 

The main aim of this chapter is to show the main applications of membrane technology in the petrochemical indns-try and the related current research trends, focusing on the impact that membrane technology can have on the process. In addition, a case study is provided to illustrate the analysis of a membrane process in terms of process intensification, showing the advantages that this type of design philosophy can transfer to an important indnstrial application. 

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