Abstract
The reaction of carbon monoxide and dichlorine over an activated carbon catalyst to produce phosgene is examined using a previously described micro-reactor arrangement. An activation energy of 34.1 kJ mol−1 is determined. The reaction profile at 323 K as a function of time-on-stream establishes steady-state operation to be achieved rapidly, with no deactivation evident within a reaction time of 300 min.. Phosgene production seemingly exhibits 100 % selectivity. However, mass balance measurements indicate a small degree of carbon and chlorine retention by the catalyst that is not directly coupled to the formation of gaseous phosgene. The molecular form of the retained moieties is unknown but, nonetheless, their presence reduces the atom economy of the process and, correspondingly, attenuates total phosgene selectivity. The order of reaction with respect CO, Cl2 and COCl2 is, respectively, 1, 0.5 and 0; leading to the determination of the rate law for phosgene production over this catalyst.
Highlights
Phosgene is an important intermediate used in the industrial manufacture of polyurethanes, polycarbonates, pharmaceuticals and agrochemicals [1]
We have undertaken a kinetic analysis of phosgene synthesis over a representative activated carbon
A previously described experimental facility [14] has been used to examine the kinetics of phosgene synthesis from the reaction of carbon monoxide and dichlorine over a commercial grade activated carbon catalyst (Donau Supersorbon K40) at ambient pressure and relatively low temperatures (298−323 K)
Summary
Phosgene is an important intermediate used in the industrial manufacture of polyurethanes, polycarbonates, pharmaceuticals and agrochemicals [1]. Over the period 1977–1980 Shapatina and co-workers produced several papers examining the kinetics of the catalytic synthesis of phosgene over activated carbon [7,8,9], with Eq 4 being representative of the rate expressions reported, r=. In 2012 Mitchell and co-workers examined a range of activated carbons for their suitability as phosgene synthesis catalysts [4]. The most recent work of Gupta and colleagues [10,11] proposes a different class of reaction mechanism compared with the earlier published body of work [3,5,6,7,8,9,12] Against this background, we have undertaken a kinetic analysis of phosgene synthesis over a representative activated carbon. An awareness of how mass is partitioned within the reaction network is a necessary perquisite for building a more comprehensive understanding of this commercially relevant reaction system
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