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Woda: użyteczne i nieszkodliwe dla środowiska naturalnego medium reakcyjne

Burczyk B.

Przemysł Chemiczny

2007

T. 86, nr 3

184-194

Zielona chemia : zadania, cele, przykłady osiągnięć

Burczyk B.

Wiadomości Chemiczne

2002

[Z] 56, 9-10

709-770

Green chemistry is the design, development, and implementation of chemical processes or products to reduce or eliminate the use and generation of substances hazardous to human health and the environment : Its aim is to combine technological and economic progress with the safeguarding of the environment, which is one of the challenges of the new millennium. To help to achieve this goal, a set of twelve principles of green chemistry was formulated by Anastas and Warner. These principles apply to a whole chemical process and to its main stages, which are: starting materials (or feedstock), reaction types and reagents, solvents and reaction conditions, and chemical products . This review only covers some of the important efforts and achievements of green chemistry. In Section 3.1 some saccharide- based syntheses are presented. Both simple sugars (glucose, lactose), and polymeric saccharides, as well as biomass have been successfully transformed into valuable chemicals. In Section 3.2, new reaction types fulfilling the atom economy principle formulated by Trost re described. The focus is on new oxidation reactions of olefins using clean oxidants: hydrogen peroxide and non-toxic, water-soluble iron catalysts, and oxygen. New possibilities of replacing toxic hydrogen cyanide and phosgene with safer reagents (e.g., dimethyl carbonate) were another topic of this Section. Section 3.3 deals with new reaction media. Water emerged as a non-toxic, environmentally benign and cheap solvent for many organic reactions, as it has several advantages: water soluble substrates (e.g., carbohydrates) can be used directly, the aqueous catalyst solution can be recycled easily, and no inert gas atmosphere is needed. The discovery of water soluble transition metal complexes made it possible to use aqueous/organic biphasic systems which have benefits in catalyst separation and recycling. Such a system has been used, for instance, in the industrial propylene hydroformylation process. Many other reactions performed in biphasic systems were reported. Water soluble rare earth trifluoromethane sulfonates have been shown to be strong Lewis acids . Supercritical fluids have been used as new reaction media; they posses a unique combination of gas- and liquid- like properties. Supercritical carbon dioxide (scCO2) and supercritical water (scH2O) were mostly exploited. New polymerization processes in scCO2 were proposed and new surfactants for scCO2 were discovered . Promising possibilities of performing oxidation reactions in scH2O were reported, as many organic compounds and oxygen are soluble in scH2O . Ionic liquids, which are characterized by a lack of measurable vapour pressure, constitute another group of neoteric solvents. They can serve both as powerful solvents (e.g., in extraction processes) and as reaction media with catalytic properties. The last Section (3.4) deals with chemical products safe for humans and for the environment. The focus is on polymers, pesticides and surfactants that are produced in a large volume. New "metallocene polyolefins" and water soluble, biodegradable polymers seem to fulfil this requirement. Selective pesticides, non-toxic to mammals, birds, and beneficial insects have been implemented, among them biopesticides. Biodegradable "sugar surfactants" and chemodegradable, acetal-type surfactants have been synthesized and some of them are already industrially produced. The review ends with some remarks on the perspectives of green chemistry in the near future (Section 4). In this context, the need for far-reaching educational initiative to promote the scientific principles of green chemistry, which were developed and implemented to the benefit of society, is stressed .