Hydrothermal Synthesis And Characterization Of Nickel, Cobalt And Tin Phosphides

Petroleum is widely used as vehicle fuel and raw materials of chemicalengineering. However, the conflicts between low-quality trend of petroleum and theworld’s increasing stringent environmental regulations are becoming more prominent.To solve this problem, developing a new type of deep hydrodesulfurization （HDS）and hydrodenitrogenation （HDN） catalysts has become a research focus of the cleanproduction. Owning to their excellent anti-sulfur poisoning property and superiorcatalytic activity, transition metal phosphide compounds have great applicationprospects in the catalytic field.In this paper, Ni₂P, Ni₁₂P₅and NiCoP were prepared by a mild hydrothermalmethod. At the same time, Sn₄P₃was synthesized by a solvothermal method withnon-toxic ethanolamine as solvents. All of these works, the red phosphor （anenvironment-friendly material） was used as the phosphor resource. Characterizationtechniques such as XRD, SEM, TEM, EDS, BET and DTA-TG were used for thecharacterization of the samples. And the major research results are as follows:1. The synthesis of Ni₂Pand Ni₁₂P₅micron meter powders by hydrothermal method.Reactions which were taken place in an acidity reaction system.（1）When the molar ratio of P and Ni was smaller than20（P/Ni≤20） thehydrothermal products were Ni₁₂P₅. The increasing of the ratio benefited to thesynthesis of Ni₂P. Both Ni₁₂P₅and Ni₂P powders were in micron meter level and theirmorphology were controlled by the red phosphor in raw materials.（2） The ideal hydrothermal temperature was200℃, lower temperature wouldlead to poor crystallinity of the products.2. The synthesis of Ni₂Pand Ni₁₂P₅nano meter powders by hydrothermal method.Reactions which were taken place in an alkaline system. （1）The alkaline environment was the key factor to prepare nano meter nickelphophide by hydrothermal method. Similar to the reaction in acidity environment,when the P/Ni≤20/1, the final product was Ni₁₂P₅, and when the P/Ni≥25/1, the mainphase of the products was Ni₂P. Both of the two kinds of nano powders were wellcrystallized and particle sizes ranged from10to50nm. And morphology of theproducts had nothing to do with the red phosphor.（2）The ideal reaction time to synthesize nano Ni₂P was10hours, which wasshorter than the time to synthesize micron Ni₂P.（3）200℃was the ideal temperature for the synthesizing of well crystallized Ni₂Pby hydrothermal method.3. Investigation on the special surface area and thermal stability of as-prepared Ni₂Ppowders.（1）The special area of as-prepared Ni₂P powders was measured by nitrogenadsorption method. The results showed nano Ni₂P had6m²/g special surface area,which was about two times of the micron Ni₂P.（2）The TG-DTA analysis indicated the as-prepared Ni₂P products were stableunder300oC even in air atmosphere.4. Hydrothermal synthesis exploration of cobalt–nickel bimetallic phosphidesUltrafine cobalt–nickel bimetallic phosphides were prepared by mildhydrothermal method and characterized by techniques, such as XRD, EDS, and TEM.The results showed that the as-prepared products were well crystallized and particlesizes ranged from10to20nm. With the increasing amount of Ni²⁺ in the suspensions,the crystallinity of obtained products was improved gradually and the crystallite sizesincreased accordingly.5. The synthesis Sn₄P₃powders by solvothermal method.Red phosphor and stannous chloride were used as phosphor and tin resourcesrespectively. Parameters such as reaction temperature, holding time and initial molarratio of P and Ni were investigated.（1）KBH₄could help to synthesize Sn₄P₃, but the products were not pure Sn₄P₃.（2）Sn₄P₃could be prepared with red phosphor and stannous chloride by solvothermal method with non-toxic ethanolamine as solvent. The ideal solvothermalconditions to prepare Sn₄P₃were: P/Sn=3/4, T=200℃, t=10h.