Catalytic hydropyrolysis of loblolly pine was studied in a high-pressure fluidized bed reactor using a NiMo hydrotreating catalyst. Hydropyrolysis temperature (375–475 °C) influenced the product distribution, product composition, H2 consumption, and process carbon efficiency. The material balances ranged from 84% to 106% with an average of 91%. The organic liquid yields including C4–C6 gases ranged from 20 wt % to 24 wt %, and the gas yields were between 11 and 27 wt %. The yield of the solids varied from 8 wt % to 26 wt %. Catalyst stability was studied at 450 °C and 20.68 bar (300 psig) total pressure with 40 vol % H2 for 10 days. The organic liquid product yield (22.5 ± 1.35 wt %) and quality (2.8 ± 1 wt % O) were consistent over 10 days of experiments with the same catalyst exposed to daily hydropyrolysis, regeneration, and reduction cycles indicating stable and steady-state catalyst performance over this time period.

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Concentrated solar power (CSP) is a promising large-scale, renewable power generation and energy storage technology, yet limited by the material properties of the heat transfer fluid. Current CSP plants use molten salts, which degrade above 600°C and freeze below 220°C. A dry, particle-based heat transfer fluid (pHTF) can operate up to and above 1,000°C, enabling high-efficiency power cycles, which may enhance CSP’s commercial competitiveness. Demonstration of the flow and heat-transfer performance of the pHTF in a scalable process is thereby critical to assess the feasibility for this technology. In this study, we report on a first-of-a-kind pilot system to evaluate heat transfer to/from a densely flowing pHTF. This process unit circulates the pHTF at flowrates up to 1 tonne/h. Thermal energy is transferred to the pHTF as it flows through an electrically heated pipe. A fluidization gas in the heated zone enhances the wall-to-pHTF heat transfer rate. We found that the introduction of gas mixtures with thermal conductivities 4.6 times greater than that of air led to a 65% increase in the heat transfer coefficient compared to fluidization by air alone. In addition to the fluidization gas, the particle size also plays a critical role in heat transfer performance. Particles with an average diameter of 270 μm contributed to heat transfer coefficients that were up to 25% greater than the performance of other particles of the same composition in size range of 65 to 350 μm. The considerations for the design of an on-sun system are also discussed. Moreover, the collective work demonstrates the promise of this unique design in solar applications.

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