Sustainable distillation process

Route A requires an equation of state and sophisticated mixing rules for calculating the fugacity coefficient for both the vapor and the liquid phase. The advantage of using equations of state is that other information (e.g. molar heat capacities, densities, enthalpies, heats of vaporization), which is necessary for designing and optimizing a sustainable distillation process, is also obtained at the same time. 

During the last decade many industrial processes shifted towards using solid acid catalysts (6). In contrast to liquid acids that possess well-defined acid properties, solid acids contain a variety of acid sites (7). Sohd acids are easily separated from the biodiesel product they need less equipment maintenance and form no polluting by-products. Therefore, to solve the problems associated with liquid catalysts, we propose their replacement with solid acids and develop a sustainable esterification process based on catalytic reactive distillation (8). The alternative of using solid acid catalysts in a reactive distillation process reduces the energy consumption and manufacturing pollution (i.e., less separation steps, no waste/salt streams). 

The benefits of using biodiesel as renewable fuel and the difficulties associated with its manufacturing are outlined. The synthesis via fatty acid esterification using solid acid catalysts is investigated. The major challenge is finding a suitable catalyst that is active, selective, water-tolerant and stable under the process conditions. The most promising candidates are sulfated metal oxides that can be used to develop a sustainable esterification process based on continuous catalytic reactive distillation. 

Biodiesel can be produced by a sustainable continuous process based on catalytic reactive distillation. The integrated design ensures the removal of water byproduct that shifts the chemical equilibrium to completion and preserves the catalyst activity. The novel alternative proposed here replaces the liquid catalysts with solid acids, thus dramatically improving the economics of current biodiesel synthesis and reducing the number of downstream steps. The key benefits of this approach are ... 

For distillation processes the pressure dependence can usually be neglected whereas the temperature dependence has to be taken into account to develop and optimize sustainable and resource-saving processes. 

Dejanovic, I., Matijasevic, LJ. and Olujic, i. (2010) Dividing wall column—A breakthrough towards sustainable distilling. Chemical Engineering and Processing, 49,559-580. 

As seen from the above discussion, PI has a very wide scope and several books have been published on the subject. They include Re-engineering the chemical process plant - process intensification by Stankiewicz and Moulijn [1], Modeling of process intensification by Kiel et al. [11], Process intensification for green chemisty engineering solutions for sustainable chemical processing by Boodhoo and Harvey [12], Reactive distillation by Simdm-acher and Kienle [13], Micro-reactors by Ehrfeld et al. [14], etc. The discussion in this chapter is limited to selected topics on multifunctional operations, novel devices and alternate PI configurations, which are dealt with more details in the next three sections. 

The philosophy of process intensification has been traditionally characterized by four words smaller, cheaper, safer, slicker. And indeed, equipment size, land use costs, and process safety are among the most important PI incentives. But process intensification can (and should) also be placed in a broader context—the context of sustainable technological development. Several years ago DSM published a picture symbolizing its own vision of process intensification (32), in which skyscraping distillation towers of the naphtha-cracking unit are replaced by a compact, clean, and tidy indoor plant (see Figure 3). The importance of PI for sustainable development and its role in the company s responsible business has been further stressed in a recent publication by the company s CEO, Peter Elverding (33). Here,... 

Although some kinds of optically active compounds can be prepared by an asymmetric synthesis using a chiral catalyst, this method is not applicable for preparation of all kinds of compounds. Furthermore, optical yields of the product are not always very high. On the contrary, optical resolution method by inclusion complexation with a chiral host is applicable to various kinds of guest compounds as described in this chapter. When optically pure product cannot be obtained by one resolution procedure, perfect resolution can be accomplished by repeating the process, although asymmetric synthetic process cannot be repeated. Especially, optical resolutions by inclusion complexation with a chiral host in a water suspension medium and by fractional distillation in the presence of a chiral host are valuable as green and sustainable processes. 

Membrane operations have the potential to replace conventional energy-intensive separation techniques, such as distillation and evaporation, to accomplish the selective and efficient transport of specific components, to improve the performance of reactive processes and, ultimately, to provide reliable options for a sustainable industrial growth. 

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