As for less branched substrates, hydrocracking on Ni/TiO2-A-SG also generates no C1-2 products (Figure , for the same reason with PP), but less C4-6. This could be explained as these substrates have less C with high steric hindrance, leading to faster dehydrogenation, higher free alkene concentration, and thus less secondary cracking. We note that LDPE and n-C16H34 both have 2 C at chain ends in the virgin structure, which allows type-B1 β-scissions. C3 yields are still low, suggesting that the isomerization -type-A β-scission sequence is preferred over type-B βscission, consistent with the literature. We also noticed that in the hydrocracking of PP (on Ni/TiO2-A-SG), the hardness of the solid residue does not seem to change with the PP conversion. This echoes with previous report that the average MW (GPC-based) of the solid does not decrease significantly with hydrocracking reaction time, and implies that hydrocracking preferentially converts smaller products over large polymers, opposite of hydrogenolysis. This could be due to the secondary cracking, which is enhanced by the mass transfer limitation in the viscous environment trapping products around BAS and causing re-adsorption, and/or the slower diffusion of large polymers preventing it to reach BAS after dehydrogenation.