Troubleshoot your hydrocracking catalyst test
Catalyst testing in parallel reactors is common practice in hydroprocessing; the accurate control and distribution of gas and liquid makes results are more reliable than ever. Tests are more cost-effective and more options or catalyst systems can be tested and/or run replicate reactors to significantly increase precision on the results. The amount of data generated makes troubleshooting of experiments more complex.
Let’s take a look at an hydrocracking screening test of 8 catalysts loaded in duplicates (16 reactors) as typically performed within refinery catalysts testing projects where small differences are expected.
Start with the basics
In such a test, one or more reactors can be affected. The first check should be if the overall mass balance across all reactors (combined liquid product weight and gas make data) is consistent. The standard deviation between the same catalysts at the same conversion level should not be higher than 2%. If it is higher, re-check the liquid product weights before having a detailed look at the online gas chromatogram (GC) (C1-C12). The peaks retention times can shift and cause differences in the gas make.
TIP: check the total amount of methane formed and compare it with the theoretical amount resulting from the DMDS added to spike the feed to check the calibration factors of the GC. In addition, as a rule of thumb, the amount of C2 formed should be lower compared to C3 and C4 – of course depending strongly on the active component used in the catalyst.
And then go step by step
If the overall mass balance of the 16 reactors is correct but you observe a large deviation between reactors, uneven distribution of the liquid or gas is the most likely scenario. This is can be caused by blockages in the upstream feed section. The helium flow mass balance between inlet and outlet across each reactor can be used to validate a working gas feed distribution and should be 100%+-2%.
TIP: check your online GC calibration by comparing the calculations based on the calibrated values with the raw GC chromatogram areas of Helium and Hydrogen (if measured on the same detector) as they should be the same. If the Helium mass balance is correct, verify that the total counts of the FID in the GC between similar reactors is similar; else there is probably an issue with your catalyst. If you have a Flowrence® Active Liquid Distribution (ALD), you can easily identify issues with the liquid distribution; simply monitor the flow signal for each reactor in the ALD flow sensor to validate equal distribution real-time.
3 key graphs you shouldn’t miss on your testing dashboard
- Mass Balance vs Time-on-stream – The standard deviation per reactor should be within 2% (95% interval) independent of the conversion. If deviations occur, especially with higher net conversion (resulting in higher gas make) look at the online GC gas quantification.
- Hydrogen Consumption vs Net Conversion – The consumption should clearly correlate with the net conversion and increase with increasing temperature. Please note if the hydrogen consumption increases with temperature but the net conversion is stable you probably reached equilibrium and/or the maximum activity of the catalyst is reached.
- Individual Hydrocarbon Selectivities vs Net Conversion – These graphs are complex and strongly depend on the catalyst active component. For example, if there is a high gas make with lower than expected conversion, then the unselective cracking towards lighter components is dominating which probably points towards an issue with the zeolitic component.
Being able to troubleshoot a hydrocracking experiment real-time is key to deliver meaningful test results; some considerations are shared above. With the Flowrence® enabled-technology like the ALD (Active Liquid Distribution) and iRPC (individual Reactor Pressure Control), you are able to execute hydrocracking experiments on-time in cost-effectively; accelerating your catalyst R&D.