In this work, a 5 wt.% Ni/HZSM-5 catalyst is prepared via precision impregnation and applied in the low-temperature hydrocracking of low-density polyethylene (LDPE), realizing the directional conversion of LDPE into narrow-distributed C₃ (propane)-C₅ (pentane) alkanes using a simple catalytic system. Experimental results show that the LDPE conversion reaches 99.0%, the C₃-C₅ yield is 85.4 wt.%, and the selectivity toward the target products exceeds 99.0%. The catalyst exhibits excellent stability with no obvious deactivation after 5 recycling runs. The catalyst preparation parameters and reaction conditions are experimentally optimized, and the optimal preparation protocol is determined: HZSM-5 with a Si/Al ratio of 25 is used as the support with a Ni loading of 5 wt.%, followed by calcination at 550 ℃ for 4 h and reduction in a hydrogen atmosphere at 450 ℃ for 4 h. Hydrogen radical regulation experiments using C₆H₁₄ and CH₃OH as model compounds confirmed that the polymerization of methyl radicals (CH₃·) contributed to the high selectivity, and hydrogen radicals (H·) mainly promoted the formation of small-molecule intermediates and stabilized the formation of alkanes from intermediates with carbon chain lengths of 3-5. This catalytic mechanism is proven to be universal for both LDPE and polypropylene. This work provides an efficient non-noble metal catalytic system and theoretical support for the directional conversion of waste polyethylene.

Pentylene glycol derived from biomass is predicted to replace 1,6-hexanediol and 1,4-butanediol derived from petroleum on the polyester market and can be utilized as an organic chemical and fine chemical raw material. The effect of catalyst element composition, reaction temperature, hydrogen pressure and reaction duration on the hydrogenolysis of biomass-derived furfural to produce 1,5-pentanediol is investigated. The results indicate that the addition of the rare earth element Re greatly increased the average particle size and particle size distribution of Pt in the catalyst. When the Pt/Re mass ratio was 3∶4, the reaction of C-O bond breaking with furan ring hydrogenation was significantly higher than that of other Pt/Re mass ratios; Increasing the reaction temperature is not only conducive to the rupture of cyclic ether C-O, but it also promotes the hydrolysis reaction of the furan ring C=C; Increasing the H₂ pressure has no appreciable effect on the hydrolysis reaction of the C-OH bond. At the interface of the ReO_x and TiO₂ layer zones, the Re-(OH)-Ti site is the center of hydrogenation from furfural to tetrahydrofurfuryl alcohol and 1,5-pentanediol. When the number of Re-(OH)-Ti adsorption sites at the boundary increased, the reaction of alkoxide and secondary carbon positive ionization to generate 1,5-pentanediol was accelerated. 1,5-pentanediol was produced with the maximum yield of 29.72% by reacting a Pt/ReO_x/TiO₂ catalyst with furfural at 130 ℃ and 6 MPa for 8 hours.