Hydrodeoxygenation Of Benzofuran On Supported Pt, Pd, And Pt-pd Catalysts

Owning to the decline in the availability of crude oil resources, bio-oils (bio-refinery) from fast pyrolysis of lignocellulosic materials (e.g., straw, forest by-products, etc.) are considered to be alternative sources for green or renewable fuel. However, the properties of bio-oils depend strongly on the transformation process, which may lead to low volatility, high viscosity, low heating value, and poor chemical stability due to high oxygen concentrations up to50%. Hydrodeoxygenation (HDO) can be used to remove oxygen to upgrade bio-oil feedstocks into gasoline and diesel. Due to the high hydrogenation properties of noble metals, they have been known to remove aromatic compounds from diesel fuel. By comparison to conventional metal sulfide catalysts, supported noble metal catalysts have a better hydrogenation performance at lower temperatures, which are very interesting candidates for bio-oil hydrogenation. In this work, a series of monometallic Pt, Pd and alloyed Pt-Pd catalysts (mole ratio Pt/Pd=1;4;0.25) were prepared with silica-alumina and C as support. CO chemisorption, X-ray diffraction (XRD) TEM, and XPS were applied to characterize the resulting samples. The performance of the catalysts for hydrodeoxygenation for benzofuran and dibenzofuran was evaluated in a fixed-bed flow reactor. The reaction route and the conversion and product selectivity of Pt, Pd and bimetallic Pt-Pd catalysts with the influence of the reaction condition were investigated in detail. The main contents and results are as follows:A series of Pd、Pt、Pd-Pt (Pd:Pt=4:1)/C catalysts were prepared by immersion method. The performance of the catalysts for hydrodeoxygenation for benzofuran was carried out. The optimal loading of all catalysts are3wt%. The experiments were carried out at300℃and3.0MPa. Over the Pd:Pt=4:1catalyst, the benzofuran conversion is up to100%, the selectivity to deoxygen compounds is up to94%. These values are all higher than those on nomometallic Pt, Pd catalysts.2-ethylcyclohexanone, which was not observed over the sulfide catalysts, was detected as a new oxygen-containing intermediate in the hydrodeoxygenation of benzofuran over the activated carbon supported Pt, Pd, and Pt-Pd catalysts. A ketone/enol isomerization reaction route was supposed to be happened over the activated carbon supported noble metal Pt, Pd, and Pt-Pd catalysts. A series of monometallic Pt, Pd and ailoyed Pt-Pd catalysts (mole ratio Pt/Pd=1;4;0.25) were prepared with silica-alumina as support. The conversion and product selectivity of Pt, Pd and bimetallic Pt-Pd catalysts with the influence of the contact time were investigated in detail for the hydrodeoxygenation of BF and DBF. The Pd-Pt (Pd:Pt=4:1) catalyst showed the highest activity and selectivity, which the benzofuran conversion is up to99%and selectivity to ethylcyclohexane is up to45%. Only one major route of this reaction network was found among the catalysts. The selectivity towards the2,3-dihydrobenzofuran was100%among all the other catalysts at low weight time. Over the Pd-Pt (Pd/Pt=1:4) catalyst, the dibenzofuran conversions is up to99%, the selectivity to deoxygenation compounds is up to98%.