Bo Zhang,Peiyu Yao,Fei Li,Li Pan,Wuwan Xiong,Yang Zhang,Xiang Li
Hydrogen production through the catalytic pyrolysis of low-value organic solid waste offers a promising low-carbon and environmentally friendly pathway. However, the design of efficient hydrogen-producing catalysts remains a significant challenge. Herein, NiO/Al2O3as a catalyst precursor was utilized to investigate the effects of reduction temperature gradients (300–800 °C) on the distribution of three-phase products and the composition of gaseous products during the pyrolysis of waste textiles. Compared to unreduced NiO/Al2O3, increasing the reduction temperature (300–700 °C) led to a gradual decrease in liquid-phase products and a notable increase in gas-phase products, with the latter rising by 10.59% at 700 °C. Most strikingly, hydrogen gas production increased by 6.42% under the same conditions. Multi-characterization analyses, including XRD, TEM, and H2-TPR, revealed significant aggregation of highly dispersed Ni species in NiO/Al2O3at higher reduction temperatures. The emergence of XRD characteristic peaks and the (111) crystal face of metallic Ni (Ni0) became apparent at 700 °C. More importantly, the XPS test inferred that the increasement of hydrogen-rich gas production was ascribed to the appropriate Ni0/Ni2+ratio, and the highest hydrogen yield of 41.50% was achieved as the Ni0/Ni2+ratio reached about 1.57. This work not only provides an effective solution for the consumption of waste textiles, but also converts it into high value-added hydrogen-rich gas.
Zixuan Sheng,Khomidov Fakhriddin Gafurovih,Kadyrova Zulayho Raimovna,Bingying Gao,Linqiang Mao
The widespread use of NiO/Al 2 O 3 catalysts in the petrochemical industry generates hazardous spent materials due to the formation of refractory nickel-aluminum spinel (NiAl 2 O 4 ), which complicates metal recovery and exacerbates resource inefficiency. Traditional direct acid and alkali leaching cannot recover Ni and Al due to excellent stable structure of NiAl 2 O 4 . Here, we propose a simple soda roasting-water leaching strategy to disrupt the spinel lattice and recover Ni and Al with high efficiency. By roasting spent catalysts with Na 2 CO 3 at 1000 °C, Na + ions substituted Al 3+ in the octahedral sites, which destroyed the spinel framework and converted Al 2 O 3 /NiAl 2 O 4 into water-soluble NaAlO 2 . Over 98.31 % of Al was selectively leached at 90 °C, followed by pH-controlled precipitation and calcination at 600 °C to regenerate γ-Al 2 O 3 with the purity of 98.21 %. Residual NiO was recovered via 2 M H 2 SO 4 leaching, with Fe impurities removed through pH-selective precipitation. The kinetic analysis revealed a chemically controlled leaching mechanism ( E a = 47.61 kJ/mol). Final Ni(OH) 2 through calcination at 400 °C yielded reusable NiO. This approach achieved >98 % metal recovery, minimized waste, and aligned with circular economy principles by transforming hazardous spent catalysts into high-purity industrial feedstocks.
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