No abstract

During catalytic upgrading over HZSM-5 of vapors from fast pyrolysis of biomass (ex situ CFP), water reacts with aromatic intermediates to form phenols that are then desorbed from the catalyst micropores and produced as products. We observe this reaction using real time measurement of products from neat CFP and with added steam. The reaction is confirmed when 18 O-labeled water is used as the steam source and the labeled oxygen is identified in the phenol products. Furthermore, phenols are observed when cellulose pyrolysis vapors are reacted over the HZSM-5 catalyst in steam. This suggests that the phenols do not only arise from phenolic products formed during the pyrolysis of the lignin component of biomass; phenols are also formed by reaction of water molecules with aromatic intermediates formed during the transformation of all of the pyrolysis products. Water formation during biomass pyrolysis is involved in this reaction and leads to the common observation of phenols in products from neat CFP. Steam also reduces the formation of non-reactive carbon in the zeolite catalysts and decreases the rate of deactivation and the amount of measured "coke" on the catalyst. These CFP results were obtained in a flow microreactor coupled to a molecular beam mass spectrometer (MBMS), which allowed for real-time measurement of products and facilitated determination of the impact of steam during catalytic upgrading, complemented by a tandem micropyrolyzer connected to a GCMS for identification of the products.

Li-ion batteries lose both capacity and power over time due to calendar aging caused by slow parasitic processes that consume Li+ ions. Studying and mitigating these processes is traditionally an equally slow venture, which is especially taxing for the validation of new active materials and electrolyte additives. Here, we evaluate whether potentiostatic holds can be used to accelerate the diagnosis of Li+ loss during calendar aging. The technique is based on the idea that, under the right conditions, the current measured as the cell voltage is held constant can be correlated with the instantaneous rate of side reactions. Thus, in principle, these measurements could capture the rate of capacity fade in real time. In practice, we show that this method is incapable of quantitatively forecasting calendar aging trends. Instead, our study demonstrates that potentiostatic holds can be applied for initial qualitative screening of systems that exhibit promising long-term stability, which can be useful to shrink the parameter space for calendar aging studies. By facilitating the identification of improved formulations, this approach can help accelerate innovation in the battery industry.