Greener catalytic process

This builds on the key research carried out on titanium-doped mesoporous solids and their use in selective oxidations using hydrogen peroxide. Catechol and hydroquinone are now manufactured commerdally using the Enichem catalyst TS-1 (prepared from tetraethylorthosilicate and tetraethylorthotita-nate71) and hydrogen peroxide.72 Traditional methods of manufacture have low atom efficiency and the successful exploitation of new greener catalytic methods in such processes is very important.73,74... 

In the late 1990s, Cativa catalytic process based on an active form, [Ir(CO)212] , is greener and more efficient and has largely supplanted the Monsanto process [32]. However, the problems of high separation cost and high corrosion rate still exist. 

The major advantage of this one-step catalytic synthesis is that no phosgene derivative such as R jNCOCI is used, which is greener than the traditional stoichiometric processes. It also enables straightforward access to vinylcarbamates, which are useful monomers for functional polymer production. 

Renewable raw materials can contribute to the sustainability of chemical products in two ways (i) by developing greener, biomass-derived products which replace existing oil-based products, e.g. a biodegradable plastic, and (ii) greener processes for the manufacture of existing chemicals from biomass instead of from fossil feedstocks. These conversion processes should, of course, be catalytic in order to maximize atom efficiencies and minimize waste (E factors) but they could be chemo- or biocatalytic, e.g. fermentation [3-5]. Even the chemocatalysts themselves can be derived from biomass, e.g. expanded com starches modified with surface S03H or amine moieties can be used as recyclable solid acid or base catalysts, respectively [6]. 

There are different shades of greener processes as we continue exploring several alternatives to conventional chemical transformations. Rather than remediation, which involves cleaning up of waste after it has been produced, the main objective is to avoid waste generation in the first place. That approach will require new environmentally benign syntheses, catalytic methods, and chemical products that are ""benign by design " and that utilize renewable resources wherever possible. 

An alternative means of technical-scale access to fluoroarenes is the fluoroformate method. Starting from the corresponding phenol a fluoroformate is generated by reaction with carbonyl chloride fluoride and subsequently catalytically decarboxy-lated to the aryl fluoride, in the gas phase, by contact with hot platinum [80] (Scheme 2.30). A newer, greener variant of the fluoroformate process has recently been introduced by Rhodia. In this the fluoroformate is formed by the (catalyzed) reaction of the phenol with COj in HF, and the expensive platinum catalyst is replaced by an aluminum-based material. 

In 1997, the Presidential Green Chemistry Challenge Greener Synthetic PathwaysAward was given to BHC Company (now BASF) for a novel method of ibuprofen synthesis.The new process consists of three catalytic steps, with the only byproduct being acetic acid, and has overall atom efficiency of about 80%. Since the acetic acid byproduct does not end up in the waste but is recovered, the process can be considered virtually 99% atom efficient. The older process, replaced by the award-winning one, consisted of six stoichiometric steps with an overall atom efficiency of less than 40%. 

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