James T. Yardley

Allied Signal, Inc.

Research and Technology

Morristown, New Jersey


Photons provide unique opportunity for chemical processing—a fact which has been well-utilized by nature, has been recognized by the ancients, and has received new significance with the development of laser technology. The maturity of solar energy control and management may open up even more unique and exciting opportunity areas. In this report, I will first present a very simple tutorial view of photochemical and photothermal processing.

I will next examine some of the experiences of scientists seeking to exploit the opportunities for lasers in chemical processing. In particular, I will present some simple economic factors which place severe limitations on the practical utility for lasers in photochemical synthesis. These realities include

  • the relatively high cost of photons,

  • market size considerations,

  • the difficulty of displacement of mature technologies with unproven ones, and

  • the need to consider not just presently used alternate technologies, but also other advanced technologies.

I will also explore some of the technical factors which have limited the use of lasers for chemical processing. These include

  • secondary photochemistry,

  • scale-up limitations,

  • quantum yield/density considerations,

  • mass and energy transport, and

  • the ability of chemists to accomplish the desired chemistry nonphotochemically.

I will show how the above considerations have shaped the evolution of the quest for viable photochemical processing.

Finally, I will discuss some opportunities for solar photochemical processing. I will first examine its particular gifts and limitations. I will then consider some possibilities in the areas of

  • organic synthesis,

  • inorganic synthesis,

  • purification,

  • biomass production, and

  • materials processing.

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