Solid Base Catalysts: Opportunities for Revewable Fuels

Wenqin Shen

A sustainable biomass economy requires the development of different integrated steps for the conversion of biomass-derived feedstocks into a range of fuels and chemicals. Many of these steps involve basic catalysts. One key step in biorefinery concept to produce diesel and jet fuel range alkanes involves C-C bond forming reactions by aldol condensation. In this research, we present two types of novel solid base catalysts for both the liquid and gas phase aldol condensation reactions: the nitrogen-substituted zeolites and silica supported CeZrOx. Furaldehydes condensation with acetone or propanal was studied in liquid phase over the nitrogen-substituted NaY (Nit-NaY) and MgO-ZrO2, a mixed metal oxide. Nit-NaY showed comparable catalytic activity to MgO-ZrO2, but higher selectivity to furadehyde acetone monomer product, indicating the shape selective significance of Nit-NaY. In the gas phase aldol condensation reaction, butanal was selected as model compound to generate C8 to C12 hydrocarbon compounds. CeZrOx/SiO2 lowers the reaction temperature about 100°C and is very stable towards acid poisoning compared to MgO/SiO2. The nature of the basic sites, the reaction chemistries and reaction mechanisms were also investigated.

Green Gasoline from Aqueous Phase Hydrodeoxygenation of Carbohydrate

Ning Li et al.

Aqueous-phase hydrodeoxygenation (APHDO) is a promising technology to convert biomass-derived oxygenates into alkanes and oxygenates. Selectively breaking the C-O bond without C-C bond cleavage is the biggest challenge and key for this project. In the previous work of Dumesic’s group, it was shown that sorbitol can be converted to gasoline by APHDO over bifunctional catalysts (Pt/SiO2-Al2O3) that contain both metal and acid sites. However, the low octane number, high Reid vapor pressure and low yield of gasoline range compounds produced in such a process limited the real application of this technology. As the first part of this work, we investigated the reaction chemistry for the APHDO of sorbitol over Pt/SiO2-Al2O3 catalyst. From the analysis of gas phase and liquid phase products, more than 40 different compounds were identified. These compounds include dehydrated sorbitol (1,4-sorbitan, isosorbide), polyols, cyclic-ether alcohols, ketones, alkanes and CO2. From the APHDO of sorbitol and a series of model intermediates, it was found that the APHDO is mainly composed of three unit reaction: 1) C-C breaking reactions by decarbonyldration or retro-aldol reactions. 2) C-O bond cleavage (dehydration followed by hydrogenation). 3) Hydrogenation reactions. Then we investigated the effect of reaction conditions (temperature, pressure, and sorbitol concentration) and different acidic support. Base on the experience we got in above work, we achieved up to 70 % gasoline product by APHDO of sorbitol over Pt/Zirconium phosphate catalyst which was proved to be the best among the catalysts we investigated. The octane number and Reid vapor pressure were also improved by the new catalytic process.