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Effective solid acid catalysts play a key role to produce high-quality biodiesel through triglyceride transesterification.

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The article reports the first quantitative kinetics model for supercritical water gasification (SCWG) of real biomass (algae) that describes the formation of the individual gaseous products. The phenomenological model is based on a set of reaction pathways that includes two types of compounds being intermediate between the algal biomass and the final gaseous products. To best correlate the experimental gas yields obtained at 450, 500 and 550 °C, the model allowed one type of intermediate to react to gases more quickly than the other type of intermediate. The model parameters indicate that gas yields increase with temperature because higher temperatures favor production of the more easily gasified intermediate and the production of gas at the expense of char. The model can accurately predict the qualitative influence of the biomass loading and water density on the gas yields. Sensitivity analysis and reaction rate analysis indicate that steam reforming of intermediates is an important source of H(2), whereas direct decomposition of the intermediate species is the main source of CO, CO(2) and CH(4).

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We determined the effects of different process variables on the gasification of Nannochloropsis sp., a marine microalga, in water with a Ru/C catalyst at 410 °C. About 45% gasification efficiency was achieved at 75 min with a catalyst loading (mass of Ru/C catalyst/mass of dry algal biomass) of 1 g/g, a water density of 0.096 g/cm 3 , and a 4.3 wt % loading of algae. Longer reaction times, higher catalyst loadings and water densities, and lower algae loadings provided higher gas yields. The level of catalyst loading had the most significant effect on both the yields and composition of the gaseous products. Complete gasification of the microalga was achieved with a catalyst loading of 2 g/g. The Ru/C catalyst recovered from an experiment and then reused in a new experiment was less active than fresh Ru/C. This loss of activity is, in large part, due to deactivation by sulfur, which is present in the microalga at about 0.5 wt %. A simple two-step catalytic gasification mechanism, along with a step for catalyst poisoning by sulfur, led to a rate equation that was consistent with the experimental results for gasification efficiency. The presence in algae of sulfur and perhaps other elements, such as Cl, that are not as prevalent in terrestrial biomass indicates that efficient and effective gasification of microalgae could present new challenges in engineering and catalyst design.

The adsorption mechanism of carbon dioxide (CO2) on Li/UiO-66 was studied by an in situ DRIFTS study.