Extended Data Table 1 Definitions and ranges (I) of variables used in this study
From: Assessment of transport phenomena in catalyst effectiveness for chemical polyolefin recycling
Symbol | Meaning | Formula | Units | Typical values | |
|---|---|---|---|---|---|
Polyolefin properties | μ | Local viscosity of polymer melt | - | Pa s | 200-6,000 (PP340) 400-6,500 (HDPE200) |
\(\bar{\mu }\) | Average viscosity of polymer melt under typical stirring rates | - | Pa s | 300 (PP340) 500 (HDPE200) | |
DH2 | H2 diffusivity in molten polymer | m2 s−1 | ∼10−8 | ||
ρm | Density of polymer melt | - | kg m−3 | 910 (PP340) 1,000 (HDPE200) | |
Testing conditions | T | Temperature | - | K | 473-523 |
pH2 | Pressure of hydrogen | - | bar | 10-50 | |
N | Stirring rate | - | rpm | 0-2500 | |
ω | Rotation rate | \(\omega =\frac{2\pi N}{60}\) | rad s−1 | 0-260 | |
τ | Torque | - | N m | 0.06-0.1 | |
γ | Shear rate | \(\gamma =\frac{2\tau }{\pi L{D}^{2}\bar{\mu }}\approx \frac{N{D}_{r}^{2}}{60\pi ({D}_{r}^{2}-{D}^{2})}\) | s−1 | 0-2,000 for lab mechanical stirrers | |
Geometry | dp | Catalyst particle diameter | m | <10−3 | |
D | Stirrer diameter | - | m | 0.01-0.05 for lab reactors | |
L | Height of stirrer blades | - | m | 0.01-0.05 for lab reactors | |
Dr | Inner reactor diameter | - | m | 0.01-0.10 for lab reactors | |
Chemical reaction | r | Volumetric reaction rate | r = krcH2 | molH2·s−1·m−3 | ∼0.1-10 in this study |
cH2 | H2 concentration at the interface | - | mol m−3 | ∼50 in this study (Henry’s law) | |
kr | Rate coefficient | - | s−1 | ∼0.003-0.15 in this study | |
λ | Characteristic length of reaction front | \(\lambda =\sqrt{\frac{{D}_{{\rm{H2}}}}{{k}_{{\rm{r}}}}}\) | m | 10−4 -10−3 | |
η | Effectiveness factor | \(\eta =\frac{{{\rm{YieldC}}}_{1}{-{\rm{C}}}_{45}}{{{({\rm{YieldC}}}_{1}{-{\rm{C}}}_{45})}_{\max }}\) | - | 0-1 |
