PTQ Q4 2022 Issue

residence time leads to higher conversion, while the results of all the experiments are still far from equilibrium (dashed lines). However, the residence time and temperature were considerably low, revealing a good catalyst performance. Variation of the HCl:O 2 molar feed ratio revealed that higher oxygen concentration improves HCl conversion sig - nificantly. By increasing the HCl/O 2 ratio from 0.25 to 2, for example, the activity of the CuO∙Cr 2 O 3 was reduced by a factor of 4 at 360°C. Total pressure varied from 0.5 to 3.5 barg at constant HCl:O 2 molar feed ratio and temperature (see Figure 7 ). For a short residence time and thereby low conversion levels, no influence of the pressure is measurable. When approaching higher conversion at an increased residence time, higher pressure has an increasing effect on the HCl consumption. According to the reaction equation, an influ - ence of the reverse Deacon reaction will be hampered at higher pressure levels. The reaction temperature has a dominating effect on the catalyst performance. An increase of 20°C, from 360°C to 380°C, shows a conversion was increased by 1.5-fold. The maximum temperature tested was 410°C and only showed a minor gain in HCl conversion in comparison to 400°C. A closer look at Figure 8 gives more insights into catalyst decay. It shows the HCl conversion versus time on stream right after a condition change. Using the FTIR technology, a single data point could be recorded in less than five minutes, and a full turnaround of 16 reactors took a maximum of 80 minutes. This way, even small incremental changes in the effluent concentrations of short catalyst beds can be measured to describe the deac - tivation behaviour of Deacon catalysts. The CuO∙Cr 2 O 3 shows an initial drop in conversion at every condition, within a steeper slope at higher temperatures. Reproducibility runs after a temperature variation (black symbols) show a consistent drop in conversion, revealing the temperature as a main factor in catalyst deactivation. A

mod = 600 kg s m –3 mod = 420 kg s m –3 mod = 240 kg s m –3

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reproducible results, suggesting those positions operate at an equal temperature profile, as shown in Figure 5 . At the lowest dilution of 1:0.5, the HCl conversion drops for the CuO∙Cr 2 O 3 (right graph, hollow symbols). It is assumed that local hot spots could not be avoided, which deacti - vated the catalyst. The CuCrO 2 was diluted from 1:1 to 1:3, which shows similar results. Based on dedicated packing protocols and exact temperature control, isothermal pro- cessing can be ensured, making this unit a powerful tool for catalyst benchmarking. A variation of the molar feed ratio and residence time at different reaction temperatures was carried out over a broad range. The results are shown to be exemplary for the most active material CuO∙Cr 2 O 3 , as shown in Figure 6 . A higher Figure 7 HCl conversion vs total pressure of CuO∙Cr₂O₃ at different residence times and 380°C and HCl:O₂=0.5 mole/ mole

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Figure 8 HCl conversion vs experiment time after conditions change for CuO∙Cr₂O₃ and CuCrO₂ at 0.5 barg, HCl:O₂=0.5 mole/mole and a residence time of 600 kg * s/m³

PTQ Q4 2022