Common ketonization catalysts such as ZrO 2 -, CeO 2 -, and TiO 2 -based catalysts have been reported to lose surface area, undergo phase transformation, and lose catalytic activity when they are utilized in the condensed aqueous phase. In this work, we synthesized a series of La x Zr y O z mixed-metal oxides with different La:Zr atomic ratios with the goal of enhancing the catalytic activity and stability for the ketonization of acetic acid in condensed aqueous media at 568 K. We synthesized a hydrothermally stable La x Zr y O z mixed-metal oxide catalyst with ketonization activity 265 and 45 times more active than La 2 O 3 and ZrO 2 , respectively. Catalyst characterization techniques suggest that the enhanced stability of the La x Zr y O z catalysts is observed with the formation of a phase isomorphic with tetragonal ZrO 2 . DRIFTS spectroscopy measurements indicated the enhanced catalytic activity of La x Zr y O z catalysts correlated with greater acetic acid surface population in the presence of H 2 O versus pure ZrO 2 .

Heterogeneous catalysis in the aqueous phase is paramount to the catalytic conversion of renewable biomass resources to transportation fuels and useful chemicals. To gain fundamental insights into how the aqueous phase affects catalytic reactions over solid catalysts, vapor- and aqueous-phase acetic acid ketonization over a monoclinic zirconia (m-ZrO2) catalyst had been comparatively investigated using ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) calculations. The monoclinic zirconia was modeled by the most stable ZrO2(1̅11) surface structure. The aqueous phase consisted of 111 explicit water molecules with a density of 0.93 g/cm3. The AIMD simulation results reveal that the aqueous phase/ZrO2(1̅11) interface is highly dynamic. At the typical reaction temperature of 550 K, ∼67% 6-fold-coordinated Zr6c Lewis acidic sites are occupied by either water molecules or hydroxyls, while all 2-fold-coordinated O2c sites are protonated as hydroxyls. As a result, it is expected that there are limited active sites on the ZrO2(1̅11) surface for acetic acid adsorption in the aqueous phase. Acetic acid ketonization on the ZrO2(1̅11) surface in both vapor and aqueous phases is assumed to be proceeded via the β-keto acid intermediate. In the vapor phase, an alternative Langmuir–Hinshelwood mechanism in which the neighboring coadsorbed acetic acid and dianion can directly combine together and form the CH3COOHCH2COO* intermediate is identified as the more feasible pathway than the traditional C–C coupling step via the combination of acyl and dianion. In the aqueous phase, our DFT results demonstrate that water molecules actively participate in the deprotonation and protonation steps via the Grotthuss proton transfer mechanism. Furthermore, our results suggest that an Eley–Rideal mechanism pathway for the formation of the β-keto acid intermediate is feasible in the aqueous phase on the basis of the observed energetic analysis. However, the low availability of dianion is also a key factor that inhibits the ketonization reaction in the aqueous phase. The effects of dynamic aqueous phase on the key surface reaction steps are further confirmed by sampling different reaction configurations from AIMD trajectories.

Hydrothermal liquefaction (HTL) uses heat and pressure to liquefy the organic matter in biomass/waste feedstocks to produce biocrude. When hydrotreated the biocrude is converted into transportation fuels including sustainable aviation fuel (SAF). Further, by liquifying the organic matter in wet wastes such as sewage sludge, manure, and food waste, HTL can prevent landfilling or other disposal methods such as anerobic digestion, or incineration. A significant roadblock to the development of a new route for SAF is the strict approval process, and the large volumes required (>400 L) for testing. Tier α and β testing can predict some of the properties required for ASTM testing with <400 mL samples. The current study is the first to investigate the potential for utilizing wet-waste HTL biocrude (WWHTLB) as an SAF feedstock. Herein, several WWHTLB samples were produced from food waste, sewage sludge, and fats, oils, and grease, and subsequently hydrotreated and distilled to produce SAF samples. The fuels (both undistilled and distilled samples) were analyzed via elemental and 2D-GC-MS. Herein, we report the Tier α and β analysis of an SAF sample derived originally from a WWHTLB. The results of this work indicate that the upgraded WWHTLB material exhibits key fuel properties, including carbon number distribution, distillation profile, surface tension, density, viscosity, heat of combustion, and flash point, which all fall within the required range for aviation fuel. WWHTLB has therefore been shown to be a promising candidate feedstock for the production of SAF.

SynopsisBatch production of urea-formaldehyde resins at temperatures up to 100°C takes several hours for completion. Reduction of the batch time may be possible with the higher reaction rates obtained at higher temperatures and increased pressures. In order to investigate this possibility, an experimental technique to obtain the necessary kinetic data, without loss of formaldehyde by evaporation, was developed. The results are compared with earlier low-temperature data extrapolated to the present range of interest. The results were interpreted on the basis of the successive reaction of two or three molecules of formaldehyde with a molecule of urea. Rate EquationsIn order to carry out the chemical engineering design procedure for a reactor producing UF (urea-formaldehyde) resins, appropriate rate equations would be required of the formwhere r = rate of appearance or disappearance of a chemical, c = concentration of that chemical, and t = time elapsed from start of reaction.It has been established1 that the combination of urea and formaldehyde begins with a series of addition reactions2 followed by condensation reactions3; that the speed and extent of reaction are dependent on temperature, pH, and U:F ratio, although the reaction rate is essentially constant in the pH range 4-9 at constant temperature4 and that UF3 is produced in significant quantities only at low U:F ratio^.^ Therefore, since the commercial process usually involves U:F molar ratios between 1:1.33 and 1:2.2, within the pH range 4-9, it is reasonable to assume initially that the reactions taking place are UF1+F+UF2so that the rate equations become