Cleaner process initiatives

Several national and international bodies have recognised the contribution which cleaner processes can make to environmental protection and launched initiatives to foster their development and introduction. 

The United Nations Environmental Programme (UNEP), which has done much to legitimise the term cleaner production, launched a number of industry sector working groups in the early 1990s. These include the following which involve chemical processes  

The working groups publish newsletters and reports and provide a network for those working in these industries across the world. UNEP and UNIDO (United Nations Industrial Development Organisation) are also setting up about 20 centres for cleaner production in less developed countries. These centres will be independent and industry driven, involved in education, technology transfer and consultation regarding cleaner production. 

Within Europe, CEFIC, which represents the European Chemical Industry, has launched an initiative, under the name of SUSTECH, which is intended to promote collaboration within the chemical and related processing industries on the theme of cleaner manufacturing. At the time of writing, this is at an early stage, but it is an interesting move as the chemical industry has traditionally been less inclined to collaborate on technical developments than the oil and some other industries. 

Summary Report Attitudes, Beliefs and Images, CM A, October 1993. 

---

In the field of fine chemical synthesis there is an urgent need to substitute the cleaner technologies for the old polluting ones. It is hoped that the large economic and environmental benefits brought by the recently developed catalysis processes—acetylation of anisole and of veratrole, Beckmann rearrangement, and so forth—will initiate great strides in this field. 

Even though ChL is designed to offer advantages to the involved parties, until now ChL is no self-running process. An initiator and some catalysts" are necessary to start the reaction". Possible initiators are international organisations like UNIDO with a worldwide network of National Cleaner Production Centers but also companies which already successfully apply ChL might be a driving force for this business model. 

Cleanliness is critical in modem supcrullnys because of Ihe role of inclusions in initiating fatigue cracks and fracture. Several refining processes to produce cleaner superaltoys have been introduced, including... 

Soliroc A process for solidifying aqueous wastes, converting them to a solid form suitable for landfill. The waste is initially acidic. Sodium silicate, cement, and lime are added, converting the liquid to a gel that hardens in several days. Developed by the Dutch company Esdex and used on a large scale in several countries. Soliroc Metal is the name of a Canadian manufacturer of vacuum cleaners. 

There is a variety of processes that act to remove a trace gas from either the troposphere or the stratosphere. For oxygenated VOCs the main tropospheric loss occurs via gas phase oxidation reactions involving OH, O3, NO and Cl radicals, and photolysis. However, the hydroxyl radical is the most important oxidizing species in the global troposphere [16-19]. As a result of its role in initiating the majority of oxidation reaction chains, the OH radical is the primary cleansing agent for the lower atmosphere and has been called the "tropospheric vacuum cleaner" [20]. The dominant production cycle for tropospheric OH involves the reaction of 0( D), produced from the photolysis of O3, with H2O ... 

The use of cleaner high-performance rubbers (e.g. fluorocarbons and halobutyls) is also expected to continue to grow at the expense of the diene type mbbers. The pressure to ensure ever higher margins of food safety is one reason and the demand for owners of food processing plants for increased time between failures is another. Although there are initial cost implications. 

As can be seen from the few examples cited above SET processes are now fairly common in organic photochemistry. One of the areas where considerable study has taken place is the process referred to as a photo-NOCAS. Within this framework Albini and coworkers have shown that the products formed from the reaction of 2,3-dimethylbut-2-ene with 1,4-dicyanobenzene are compounds (22)- 25). The reaction was brought about using phenanthrene as the initial light absorber. This technique leads to cleaner reactions than those where the 1,4-dicyanobenzene is irradiated directly. The solvent system used is methanol/ acetonitrile and products (24) and (25) are the result of solvent incorporation. A further example of photo-NOCAS chemistry has been reported by Arnold and coworkers.Typical of the examples studied is the reaction illustrated in Scheme 2. The cyclization of the dienes (26) was also examined. This specific example deals with the generation of radical cations from (/ )-(+)-a-terpineol and (/ )-(+)-limonene with 1,4-dicyanobenzene as the electron accepting sensitizer. In another detailed study on reactions of this type the factors that control the regiochemistry in photo-NOCAS processes have been assessed. ... 

Several groups have demonstrated that desilylation of dialkyl l-(trimethylsilyl)methylphosphonates initiated by means of fluoride ion (CsF, KF, or TBAF) is an effective process for the transfer of carbanions to electrophilic centers. Some examples involving the fluoride-induced formation of a-phosphonylated carbanions from dialkyl l-(trimethylsilyl)methylphosphonates containing a fragile C-Si bond have been described. Cleavage of the carbon-silicon bond under these conditions offers the advantages of neutral conditions and contributes to obtain better yields from sensitive substrates than those obtained under basic conditions. This procedure, which appears operationally simpler and cleaner than traditional protocols, has been applied to the preparation of alkenes " and 1-alkenylphosphonates" by Homer-Wadsworth-Emmons and Peterson reactions, respectively. 

---