OSMIUM

IAN SHOTT

Osmium, used primarily in pen nibs and armor-piercing weapon shells, is the densest metal in the periodic table. It can, however, typify an often encountered chemical conundrum. On the one hand, it is very useful as the metal in a highly stereospecific catalyst, which is both nonvolatile and nontoxic. In the development world, it has enjoyed widespread use in directly synthesizing a range of valuable pharmaceutical intermediates. On the other hand, its oxide is both highly toxic and very volatile, with high physical penetration of a variety of otherwise inert materials. Commercially, the oxide is used as a stain in microscopy.

Thus, scale-up in conventional multipurpose plants poses three significant issues: waste containment and treatment; product purification, as even parts-per-billion concentrations cannot be tolerated; and decontamination of the plant and equipment where the oxide will have penetrated surfaces, particularly PTFE (polytetrafluoroethylene) linings and joints.

This combination can result in the necessity to make an otherwise multipurpose plant dedicated, with the consequential negative impact on capacity utilization and overall production economics. A frustrating cycle then occurs, whereby industrious process researchers find an elegant solution to synthesize an otherwise difficult-to-make intermediate, and they successfully produce a sample that is purified and analyzed. This is well received by the customer, who then wants larger quantities and detailed large-scale pricing. It proves impossible to fit it into existing equipment, and a substantial investment is required for a dedicated, segregated, highly specified plant. The market is not yet established, cost is an issue, and price sensitivity is critical. High capital expenditure and low occupacity mean production costs are prohibitive, and the opportunity is consequently lost. The activation energy to convert an intellectual curiosity into a commercial reality has not been overcome.

The specialty chemical company Rhodia does have access to intellectual property in this area and has undertaken some semitechnical trials and scale-up pilot-plant activity. To my knowledge, only two or three other companies also have limited operational experience but no fully commercial activity.

The cycle can be broken only if one single opportunity is so certain, so large, so cost insensitive it can support the investment. Today, this type of opportunity is a rare animal and more probably in danger of extinction.

Standing back from this issue, we could be facing a huge generic problem with the combination of today's increasingly complex chemistry and existing state-of-the-art multipurpose technology. The latter is, in general, based on a simplified flow sheet of large stirred-tank reactors that has essentially existed for the past five centuries! Modernization has brought a plethora of new materials and instrumentation that have increased the cost of fundamentally low productivity equipment trains. Thus, no discernable benefit in terms of unit cost reduction has resulted.

Most organic synthesis routes to complex pharmaceuticals have numerous stages with high dilution and slow kinetics offering miserable overall yields and appalling productivity. These routes under batch conditions are very complex and involve inherently dirty chemistry with numerous side reactions. A new vision for tomorrow could involve a type of process "circuit board" of modules encompassing fewer stages, inherently clean and direct routes, rapid reaction kinetics, high throughputs, high overall yield, lower waste, and substantially improved productivity.

In today's world of process intensification, supercritical fluid technology, nanotechnology, and "multidisciplinarianism," there is considerable scope for innovation.

	POINTED One of osmium's major uses is in fountain pen tips.
	PHOTODISC

Coming back to osmium, it could conceivably be embedded in a microreactor module where the oxide is retained and recycled while the reactants and products have low residence time, with the product "escaping" largely contaminant-free to the next isolation and purification modules. In this world, all multipurpose synthesis lines are a "circuit board" of cheap-to-construct, high-throughput microreactor and separator modules that are rapidly interchanged and recycled for product changeover.This will be possible only if organic and physical chemists, material scientists, engineers, and mathematicians interact at a preindustrial conceptual level to rewrite the chemistry books and make a breakthrough in multipurpose plant thinking.Over the past three decades, the electronics industry has confronted this challenge and made huge advances in moving from valve technology to microchips. The enormous benefits in functionality and cost have been passed on to the public at large. The chemical enterprise now needs to seize its challenge and unlock the full power of the periodic table for the benefit of humankind and the consumer.

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Copyright © 2003 American Chemical Society