Preparation And Regulation Of Metal Catalysts Based On Atomic Layer Deposition And Their Application In 1,4-butynediol Hydrogenation

1,4-butenediol（BED）is an important raw material for fine chemicals.In industry,BED is mainly produced by hydrogenation of 1,4-butynediol（BYD）.BYD hydrogenation is a continuous reaction.Further hydrogenation and isomerization of BED are the fundamental reasons for reducing the selectivity of BED.Pt,Pd,and Ni based catalysts are commonly used in BYD hydrogenation systems.Strategies such as controlling the size and morphology of nanoparticles,changing the carrier,and adding additives can effectively improve the selectivity of BED.At present,exploring the effect of electronic properties of active metal for the adsorption and activation of reactants on the surface of active metals through the construction of model catalysts is of great significance for deeply revealing the reaction mechanism of BYD hydrogenation.However,due to the limitations of traditional methods,it is difficult to accurately control the morphology,size,and interfacial active sites of catalysts to construct model catalysts.Atomic layer deposition（ALD）is a special chemical vapor deposition technique that forms thin films by alternating pulse precursors reacting on the substrate.Due to the self limiting characteristics of ALD,it has unparalleled advantages in regulating the continuity and uniformity of deposition species.In this paper,using the advantage of atomic layer deposition that can accurately control the catalyst,Pd and Ni model catalysts were constructed to explore the impact on BYD hydrogenation performance.Specific research content is as follows:1.In the mesoporous material SBA-15,Pd nanoparticles with a certain number of cycles are deposited,and then Zn O with different thicknesses is coated on the surface of Pd.By changing the thickness of Zn O,the effect of Pd-Zn interface sites in the confined space on the hydrogenation performance of BYD is explored.The experiment result shows that the catalyst exhibits the highest catalytic activity when the size of Pd is controlled at about 2 nm.As the thickness of Zn O coating layer increases,the Pd-Zn interface sites gradually increase,which is conducive to improving BED selectivity,up to96%.Continuing to increase the thickness of the Zn O coating layer will cover the active sites of Pd,reducing the activity of the catalyst.N₂ adsorption-desorption,XRD,and TEM showed that both Pd and Zn O were deposited into the pores,resulting in the preparation of confined catalyst.XPS showed that after coating Zn O on the surface of Pd,the peak corresponding to Pd⁰3d_5/2 shifted towards a high binding energy,showing that forming a strong Pd-Zn O interface,which was conducive to the formation of the semi hydrogenation product BED.2.The current metal catalyzed BYD hydrogenation must be carried out at high temperatures and pressures using hydrogen as a hydrogen source,which poses significant safety risks.In this paper,hydrazine hydrate is proposed as hydrogen source to achieve the selective hydrogenation of BYD to produce BED.Using atomic layer deposition technology,Ni nanoparticles with different sizes were deposited on spherical Al₂O₃.After reduction and pre-oxidation,the effect of catalyst on the performance of tandem N₂H₄·H₂O decomposition and 1,4-butynediol hydrogenation was investigated.The results showed that when 100 cycles of Ni were deposited on the surface of Al₂O₃,reduced at450^oC for 2h,and then pre-oxidized in 1%O₂/Ar at room temperature for 1h,the prepared catalyst 100 Ni/Al₂O₃-1h exhibited the highest catalytic activity,with BYD conversion of 41.44%and BED selectivity of 80.87%.TEM,HRTEM,XPS,and TPR showed that the free Ni O from the Ni catalyst after pre-oxidation would interact strongly with the carrier during the catalytic BYD hydrogenation reaction and enter the carrier lattice to achieve redistribution of surface Ni O.After the reduction of the active hydrogen species produced by hydrazine hydrate,it is separated from the lattice to obtain a catalyst with higher dispersion and better catalytic effect,while slowing down the deactivation of the catalyst.