Light is cheap to produce quadricyclane
from norbornadiene as it makes efficient use of easy wavelengths.
It needs a sensitizer, and many have been studied. Substituted norbornadienes tend to accept longer waves.
Acetophenone and plain norbornadiene to quadricyclane show 90% quantum efficiency at 366nm and 388nm
Crc Handbook of Photochemistry and Photobiology, table 17.1 (Google book)
so for instance azetidylquadricyclane (C10
N 147.22 g/mol) would need 7.5 mol/kg photons at 385nm (3.22eV = 311kJ/mol).
AlGaN diodes are 36% power efficient and produce 5W light at 385nm, while 405nm would be even better:http://www.nichia.co.jp/en/product/uvled.html
so 1kg azetidylquadricyclane needs 6.5MJ electricity. At 100€/MWh = 28€/GJ, electricity costs 0.2€/kg or 40k€/200t
A production capacity of 200t in 20d*13h or 0.2kg/s needs 500kW light. If the diodes cost 1€/W the investment is reasonable. The claimed life expectancy of 50,000h lets 1W light produce 77kg azetidylquadricyclane, adding 0.01€/kg.
(broad compilation, thanks Nist)https://www3.nd.edu/~ndrlrcdc/Compilations/Tta/Tta0008.htm
acetophenone extinguishes 2100 L/mol/cm at 406nm, so 1% in quadricyclane attenuates by exp(1) in 70µm.
With diodes that emit 5W and occupy 1cm2
, a sketch for a 500kW UV reactor is appended :
- h500mm * D38mm plungers can contain 8*50 diodes to emit 2kW and dissipate 4kW.
- Water would flow at 0.4m/s, but prefer phytane and similar as they insulate
- 48Vdc suffice in the plungers but are uncomfortable elsewhere.
- 250 plungers on a 40mm raster make the reactor 0.5m*1.1m*0.6m.
Marc Schaefer, aka Enthalpy