Hydrothermal liquefaction biocrude from non-lignocellulosic feedstocks often shows properties, such as a high presence of inorganics, oxygen and especially a high nitrogen content, which are challenging in view of hydroprocessing for the production of drop-in biofuels. In particular, nitrogen removal requires severe conditions, that might compromise continuous operations and affect the yield of the different hydrocarbon fractions. This work demonstrates the possibility of successful long-time continuous operations for microalgae biocrude, a feed with a high content of metals and nitrogen, thanks to a multi-stage approach with different sulfided catalysts. Whereas hydrodeoxygenation was achieved at relatively mild conditions, nitrogen removal was challenging. By using a number of advanced characterization techniques, among which FTICR-MS, it was possible to unveil how nitrogen removal takes place at different reaction severities, in terms of temperature, WHSV and pressure. High nitrogen removal needs high temperature (∼400 °C) and low space velocities and is associated with a high H2 consumption. This causes also a remarkable change in the boiling point distribution, which is shifted to products in the gasoline range, while the yields of middle distillates are marginally affected by hydrotreating severity. This seems to be a consequence of the denitrogenation mechanism, promoting the fragmentation of larger molecules in the heavy fractions of biocrude.

中文翻译：

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了解两级连续加氢处理装置中水热液化富氮生物原油的催化加氢处理


来自非木质纤维素原料的水热液化生物原油通常表现出诸如无机物、氧气含量高，尤其是氮含量高等特性，这对于生产直接生物燃料的加氢处理来说是具有挑战性的。特别是，脱氮需要苛刻的条件，这可能会损害连续操作并影响不同烃馏分的产率。这项工作表明，由于采用不同硫化催化剂的多阶段方法，微藻生物原油（一种金属和氮含量高的饲料）成功地长期连续运行的可能性。虽然加氢脱氧是在相对温和的条件下实现的，但脱氮却具有挑战性。通过使用多种先进的表征技术，其中包括 FTICR-MS，可以揭示在不同反应强度（温度、WHSV 和压力）下脱氮的情况。高氮去除需要高温（~400°C）和低空速，并且与高氢气消耗相关。这也导致沸点分布发生显着变化，该变化转移到汽油范围内的产品，而中间馏分油的收率受到加氢处理严重程度的轻微影响。这似乎是脱氮机制的结果，促进了生物原油重馏分中较大分子的破碎。