Upgrading diethyl 1,4-cyclohexanedicarboxylate (DECD) derived from waste polyethylene terephthalate into a valuable monomer (1,4-cyclohexanedimethanol, CHDM) can offer a promising strategy to reduce reliance on fossil resources and environmental pollution. Herein, a series of hydrotalcite-derived Cu-based catalysts were synthesized via co-precipitation method for catalyzing continuous hydrogenation of DECD to CHDM. The structural and physicochemical properties of both the catalyst precursors and reduced catalysts were systematically characterized, and their catalytic performance and stability were thoroughly investigated. The results revealed that the Cu2Mg2Al1 catalyst possessed a higher specific surface area, superior Cu dispersion, stronger metal-support interactions, and an optimal distribution of Cu+ species and acid-base sites compared with the other catalysts. Also, a synergistic catalytic effect among metal Cu sites, Lewis acid sites, and base sites was identified during the hydrogenation process, with the base sites playing an important role in promoting the conversion of DECD to CHDM. Under the optimized reaction conditions of 230 ℃, 4MPa, and a WHSV of 0.5g·gcat-1·h-1, the Cu2Mg2Al1 catalyst achieved a DECD conversion of 99.1% and a CHDM yield of 98.4%, along with long-term (over 96h) stability test. Notably, the obtained CHDM exhibited a higher trans/cis ratio of up to 3.76/1, far exceeding that of commercially available CHDM (2.33/1). This work provides valuable insights for designing effective and stable catalysts for the hydrogenation of DECD to CHDM in industrial applications.
In this work, the optimal Co-Ce-B/g-C3N4 thin-film catalyst was prepared on high-purity Ti foil by chemical deposition after optimizing pH value. It manifested an outstanding hydrogen generation rate of 6330ml·min-1·g-1 at 298K, together with a notably low apparent activation energy of 33.9kJ·mol-1 toward NaBH4 hydrolysis under light irradiation. The results substantiated that the ternary Co-Ce-B/g-C3N4 delivered superior catalytic activity relative to the binary Co-B/g-C3N4 and many of the reported catalysts. It might be attributed to the its distinctive microstructural features and synergistic interaction of multi-component system. Characterization analysis confirmed that the recombination of photoinduced electron–hole pairs was effectively suppressed within the ternary catalyst, meaning accelerated separation and interfacial transfer of photogenerated charge carriers, and leading to a pronounced improvement of catalytic efficiency for hydrogen generation from NaBH4 hydrolysis. In addition, after 5 cycles, the catalytic activity of Co-Ce-B/g-C3N4 remained 63.7% of its initial value, revealing moderate cycling stability that requires further enhancement for practical implementation.
