低温条件下无定形SiO_2-Al_2O_3的硅铝比对Ni_2P催化剂制备的影响
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摘要
用分步沉淀法制备了Si O2和不同SiO_2/Al_2O_3质量比的无定形SiO_2-Al_2O_3(ASA),采用饱和体积共浸渍和程序升温还原法制备Ni_2P/ASA催化剂,以X射线衍射、红外光谱、N2吸附脱附、H_2还原脱附和透射电镜对载体和催化剂进行表征,重点考察了低温条件下不同SiO_2/Al_2O_3比以及不同比表面积大小对Ni_2P相生成的影响。结果表明,在低温条件下,随载体中氧化铝含量增多,生成Ni_2P相所需的P含量增多。原因是磷首先与氧化铝生成Al PO4相,阻碍了富磷气氛的生成,而生成Ni_2P相必须在富P的气氛下进行,从而在铝含量较多的载体中必须加入更多的P含量才能生成纯Ni_2P相。TEM结果表明,AlPO_4相的生成反过来促进了Ni_2P颗粒尺寸的降低,有利于催化剂的分散。载体比表面积大小对Ni_2P相的生成影响不大。
The Si O2 and amorphous SiO_2-Al_2O_3( ASA) was prepared by stepwise precipitation method,and the Ni_2P/ASA catalyst was fabricated by saturated volume impregnation and programmed-temperature reduction.Characterizations of the supports and catalysts were performed using XRD,FT-IR,N2 adsorption-desorption,H2-TPR and TEM,and then the effects of SiO_2/Al_2O_3 mass ratio and specific surface area obtained with ASA on the Ni_2P formation were mainly investigated. Results showed that with the increasing of Al_2O_3 content in ASA support the more content of P was required for the formation of Ni_2P phase. Phosphorus firstly formed Al PO4 phase with alumina,hindered the formation of phosphorus-rich atmosphere,however phosphorus-rich atmosphere was pre-requisited to the formation of Ni_2P phase,hence more P must be added to the carrier with more aluminum content to produce pure Ni_2P phase. TEM results indicated that the formation of AlPO_4 phase,in turn,promoted the reduction of Ni_2P particle size and facilitated the dispersion of the catalyst. The specific surface area of the support has little influence on the formation of Ni_2P phase
The Si O2 and amorphous SiO_2-Al_2O_3( ASA) was prepared by stepwise precipitation method,and the Ni_2P/ASA catalyst was fabricated by saturated volume impregnation and programmed-temperature reduction.Characterizations of the supports and catalysts were performed using XRD,FT-IR,N2 adsorption-desorption,H2-TPR and TEM,and then the effects of SiO_2/Al_2O_3 mass ratio and specific surface area obtained with ASA on the Ni_2P formation were mainly investigated. Results showed that with the increasing of Al_2O_3 content in ASA support the more content of P was required for the formation of Ni_2P phase. Phosphorus firstly formed Al PO4 phase with alumina,hindered the formation of phosphorus-rich atmosphere,however phosphorus-rich atmosphere was pre-requisited to the formation of Ni_2P phase,hence more P must be added to the carrier with more aluminum content to produce pure Ni_2P phase. TEM results indicated that the formation of AlPO_4 phase,in turn,promoted the reduction of Ni_2P particle size and facilitated the dispersion of the catalyst. The specific surface area of the support has little influence on the formation of Ni_2P phase
引文
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[3]Y Lee,S T Oyama.J.Catal.,2006,239:376~389.
[4]宋华,代敏,宋华林.化学进展,2012,24(5):757~768.
[5]宋华,于洪坤,武显春等.催化学报,2010,31(04):447~453.
[6]P A Clark,S T Oyama.J.Catal.,2003,218(1):78~87.
[7]R Iwamoto,J Grimblot.Adv.Catal.,1999,44:417~503.
[8]A Corma,M T Navarro,J P Pariente.Chem.Commun.,1994,(2):147~148.
[9]宋立民,李伟,张明慧等.催化学报,2007,28(2):143~147.
[10]L M Song,W Li,G L Wang et al.Catal.Today,2007,125(3-4):137~142.
[11]F X Sun,W C Wu,Z L Wu et al.J.Catal.,2004,228:298~310.
[12]陈松,曹光伟,李廷钰.CNP:97116404.5,1999.
[13]C Louis,Z X Cheng,M J Che.Phys.Chem.,1993,97:5703~5712.