液相还原制备钌/碳纳米管及催化氨分解性能

Preparation of Ru/CNTs Nano-material by Polyol Reduction-deposition Method and Its Catalytical Performance for Ammonia Decomposition

通过乙二醇液相还原法将少量金属Ru沉积在碳纳米管（简称CNTs）上,TEM、XRD表征结果表明,该法明显提高了Ru在CNTs上的分散度,Ru微晶的粒径在3~4 nm。氨分解反应结果表明,采用乙二醇液相还原法在降低Ru负载量的同时还明显提高了Ru/CNTs的催化氨分解活性。在0.4 MPa、773 K、空速GHSV100%NH3=30 000 mL/（h.g）反应条件下,在液相还原法制备的4.2%Ru/CNTs催化剂上氨分解转化率可达48.5%,约为同条件下浸渍法所得5%Ru/CNTs的1.3倍,液相还原最佳配比5.7%Ru/γ-Al2O3的1.2倍。表观活化能测试结果显示用CNTs代替γ-Al2O3作为载体或分散相并不引起所负载Ru催化剂上NH3分解制H2反应的表观活化能发生明显变化。

Nowadays catalytic decomposition of ammonia is regarded as a method to obtain COfree hydrogen for its application in proton exchange membrane fuel cell.In this paper,with carbon nano-tubes（as CNTs） as substrate,a series of metallic Ru/CNTs were prepared using glycol reduction-deposition method which enhanced markedly dispersion of Ru on CNTs with the Rux0-crystallite size at 3~4 nm characterized through TEM and XRD.Under reaction conditions of 0.4 MPa,773 K and GHSV100%NH3 = 30 000 mL/（h·g）,the observed NH3-decomposition conversion over the 4.2%Ru/CNTs catalyst（prepared through ethylene-glycol reduction-deposition） reached 48.5%,which was about 1.2 times as high as that of the 5.7%Ru/γ-Al2O3 catalyst prepared by the same method,and about 1.3 times as high as that of the 5%Ru/CNTs catalyst prepared by conventional incipient wetness method.Over the 4%Ru/CNTs catalyst,100% of NH3-decomposition was attained at 870 K;while over 5%Ru/CNTs prepared by conventional incipient wetness method,the reaction temperature as high as 900 K was required for the same（100%） conversion.At 870 K,the observed NH3-decomposition conversion was only 81.7% over the 5.7%Ru/γ-Al2O3 catalyst.It was experimentally also found that using the CNTs in place of γ-Al2O3 as support of the metal Ru-catalyst did not cause a marked change in the apparent activation energy（Ea） for the reaction of NH3-decomposition to yield H2.