Preparation And Dehydrogenation Properties Of Hydrotalcite Supported Pt Catalyst

Hydrogen is a clean,efficient,stored,transportable and environmental energy.Hydrogen is regarded as one of the most potential energy of the 21 st century.It has become a global research hot spot to develop and utilize technology of hydrogen.Organic liquid hydrogen storage technology is mainly through unsaturated organic matter such as aromatic hydrocarbons and hydrogen of reversible reaction to hydrogenation and dehydrogenation process.The technical principle is storing unsaturated organic liquid hydrogen by catalytic hydrogenation and using traditional equipment for hydrogenation of organic liquid with high density storage and long distance transport.In order to realize the hydrogen utilization,organic liquid hydrogen by catalytic dehydrogenation at the destination has been used.After the release of organic liquid hydrogen,it was recycled and used by hydrogenation.Current industry hydrogenation technology was mature.In this paper,the catalytic dehydrogenation of organic liquid hydrogen was studied.The hydrogen storage for methylcyclohexane(MCH)is 6.2%,and toluene poison to the human body is small.So MCH was choosed as dehydrogenation research object.It was selected that Pt as the active component.In order to reduce the carrier of the acid,alkaline oxide MgO was selected into Al2O3.It was selected the alkali coprecipitation preparation of Mg-Al hydrotalcite carrier,Zr,Ce,La and Zn as additives.The Pt/Mg-Al,Pt/Zr-Mg-Al,Pt/Ce-Mg-Al,Pt/La-Mg-Al and Pt/Zn-Mg-Al catalyst were prepared.In order to reduce the preparation time and improve the aperture size,supersonic-assisted dispersion technique in the preparation of catalysts was used.The catalysts were characterized by BET,CO pulse adsorption,XRD,TG,FT-IR,H2-TPR and Py-IR.It was researched that Zr,Ce,La and Zn as additives and calcination temperature on the structure and properties of dehydrogenation catalyst.The performances of dehydrogenation of MCH of the hydrotalcite supported Pt catalysts was investigated in a simple fixed-bed micro reactor under the reasonable conditions as follow: reaction pressure 0.1 MPa and LHSV: 5.2 h-1.It was researched that the effect of different additives,calcination temperature and reaction temperature on the activity of dehydrogenation catalyst.The results showed that there was no acid sites on the surface of Pt/Mg-Al catalyst,which could Enhance the coking resistance and stability of the catalyst.When it was n-heptane as solven tand the mass fraction of MCH was 5%,Pt/Ce-Mg-Al dehydrogenation effect was best.MCH conversion rate reached 84.2%,but the product selectivity of toluene was only 92.6% under the condition of 300oC.When it was ventilation with N2 as carrier gas and used the pure MCH,Pt/La-Mg-Al catalyst had the high performance of 50% of MCH conversion under the condition of 300oC.The calcining temperature had no effect on the activity of Pt/La-Mg-Al catalyst.When it was not into N2 and used pure MCH,the Pt/Zr-Mg-Al-200 catalyst had the high performance of 99.7% of MCH conversion,toluene was the only product and hydrogen generation rate had reached to 280.4 mmol·gcat-1·h-1 under the condition of 325oC.Meanwhile,the Pt/Ce-Mg-Al-500 catalyst had the same catalytic activity under the condition of 300oC,the MCH conversion was close to 94.7%,toluene was the only product and hydrogen generation rate had reached to 266.3 mmol·gcat-1·h-1.