CuCrO
CuO*Cr O
50
Catalyst: Inert (v/v)
1 : 1 1 : 0.5
40
1 : 2 1 : 3
30
20
10
0
340
360
380
400
420
340
360
380
400
420
Reaction temperature (˚C)
Figure 5 HCl conversion vs reaction temperature of different catalyst:inert dilution ratios at 0.5 barg, HCl:O₂ of 0.5 mole/ mole and a residence time of 420 kg * s/m³
Results The catalytic oxidation of HCl yields chlorine and water in an exothermal equilibrium limited reaction with increasing volume per mole HCl converted, Equation (1). Low reaction temperatures and elevated pressures favour high chlorine yields from a thermodynamic point of view (see Figure 3 ).
conversion with rising temperature, even beyond 400°C. CeO 2 slightly became active at the upper end of the observed temperature range (not shown), which agrees with the lit- erature. However, the temperature was not raised further to protect the sensitive copper materials. Online temperature profiles were measured indicatively for positions 4, 7, and 10 under conditions with the highest heat release rate. For all of the experiments, the temperature was kept below a maximum difference of +/- 2K, as shown in Figure 4 (right chart). The catalyst:inert dilution was var- ied to ensure equal heat distribution across the catalyst bed and avoid hot spots that may lead to catalyst deactivation. The reactor of positions 5, 6, 11, 12, and 13 (CuO∙Cr 2 O 3 ) were not equipped with a thermocouple and, therefore, the T-profiles were not measured, but the dilution ratios rang - ing from 1:1 to 1:3 (full symbols) show reproducible results,
4 HCl + O₂ ↔ 2 Cl₂ + 2 H₂O
∆ R H
298 = -58 kJ/
mole Cl2
(1)
Figure 4 (left chart) shows the activity profile of the tested materials. CuO∙Cr₂O₃ was identified being the most active catalyst, followed by CuCrO₂. Copper-containing catalysts typically start to be active from 350°C to 400°C. While the former material (dark blue curve) shows the highest activ- ity at 410°C, the latter one shows a stronger increase in
HCl:O molar ratio = 0.25
HCl:O molar ratio = 0.5
HCl:O molar ratio = 1
HCl:O molar ratio = 2
100
80
410˚C 400˚C 380˚C 360˚C 340˚C
60
40
20
0
0 200 400
600 800 1000
0 200 400
600 800 1000
0 200 400
600 800 1000
0 200 400
600 800 1000
Residence time (kg s m ) –3
Figure 6 HCl conversion vs residence time at different reaction temperatures and molar feed ratios at 0.5 barg
32
PTQ Q4 2022
www.digitalrefining.com
Powered by FlippingBook