Study On The Functionalization Of CNTs And The Catalytic Hydrogenation Of NiB Amorphous Alloy Catalyst Supported On CNTs

NiB amorphous alloy catalysts supported on carbon nanotubes (CNTs) were prepared by impregnation-chemical reduction method with the aid of ultra-sonication. Acetylene selective hydrogenation was used as a probe reaction for the study of catalytic performances of NiB amorphous alloy catalysts. The effects of pretreatment of CNTs, functionalization of CNTs, transition metal and rare earth addition on the behaviors of NiB amorphous alloy catalysts were investigated in this paper systematically. CNTs and NiB/CNTs catalysts were characterized by means of FT-IR, TEM, XRD, TG, BET, ICP, XPS, TPR, H₂-TPD and CO chemisOrptions techniques, respectively.The dispersion of NiB particles was promoted due to the introduction of carbon nanotubes carrier, which resulted in higher active nickel surface area. As a result, the acetylene hydrogenation activity and ethylene selectivity on NiB amorphous alloy were improved, but the ethane selectivity was lowered. Meanwhile, the thermal stability of NiB catalyst was enhanced because of the dispersing effect of CNTs on NiB particles. The results of durability experiments of acetylene hydrogenation showed that the deposit of oligomer on the surface of catalysts leaded to catalysts deactivation. The formation and deposit of oligomer were suppressed, and thus the durability of catalyst was improved by supporting NiB amorphous alloy on CNTs in the time on stream experiment.Catalytic performance of NiB/CNTs was closely related to the pretreatment of CNTs. The end of CNTs was opened by heat treatment with ammonia and basic groups containing nitrogen such as -C-N and -N-H were generated on the surface of CNTs during the treatment. Functional groups, such as -COOH and -OH, were produced on the surface of CNTs and nickel residue (using Ni-Cu-Al as catalyst for synthesis CNTs) in the CNTs was eliminated effectively by nitric acid pretreatment. NiB amorphous alloy catalyst supported on ammonia treated CNTs showed higher acetylene hydrogenation activity, through nickel residue was difficult to remove by ammonia heat treatment.Functionalization could modify the hydrophobic property of CNTs and facilitate the dispersion of CNTs in liquid phase. Ammonia treated CNTs were functionalized by citric acid, n-C₈F₁₇SO₃K, sodium dodecyl sulfate, aniline and Triton X-100 for preparing high dispersed NiB particles along carbon nanotubes. Using functionalized CNTs as supports, the nickel loading, BET and active nickel surface area of NiB/CNTs were increased, due to the changes of surface property and dispersion of CNTs. TEM results implied that high density and compact NiB particles were formed on the citric acid functionalized CNTs, while NiB nanoparticles dispersed well along other reagents functionalized CNTs. Accordingly, NiB amorphous catalysts on functionalized CNTs revealed higher hydrogenation activity and better ethylene...