High-Temperature Sorption Process for Oxygen Removal and Air Separation

本项目旨在研究基于钙钛矿型陶瓷吸附剂的新型高效高温吸氧工艺的基本问题，用于除氧和空气分离。新的吸附工艺利用了某些钙钛矿型陶瓷的独特性能，这些陶瓷可以在高温（300-800℃）下吸附大量的氧气，但不能吸附其他气体。本研究选择了三种不同成分的钙钛矿型陶瓷材料作为吸附剂。采用柠檬酸盐法和压烧结法制备了不同粒径的吸附剂球团和颗粒。用重量法和点缺陷和团簇缺陷模型分别对这些陶瓷中氧位的热力学缺陷平衡进行了实验和理论研究。该缺陷平衡研究提供了这些吸附剂的氧吸附等温线数据。用热重分析/差热分析方法研究了陶瓷吸附剂的吸附热和有序-无序相变。采用瞬态重量法对陶瓷吸附剂的吸氧动力学进行了实验研究，并采用简单的线性驱动力模型和基于双极性扩散理论的更复杂的模型进行了建模。通过膨胀试验和摩擦试验，系统地研究了陶瓷吸附剂颗粒的化学和机械稳定性。最后，进行了固定床除氧或空气分离实验，以获得基于该新概念设计实际分离工艺的数据。该项目代表了基于这种新型非传统吸附剂开发吸附工艺的第一次努力。从根本上说，这个项目可能会导致大量新的吸附工艺的发展，这些工艺具有传统吸附工艺所不具备的独特分离特性。如果使用碳氢化合物再生吸附剂，则可以扩展该过程，以提供新的化学反应器，用于提高选择性的部分氧化碳氢化合物。在实际应用方面，所提出的吸附工艺是基于钙钛矿型陶瓷，具有对氧的优先平衡吸附。这种吸附工艺的成功开发将对空气分离和除氧的工业过程产生重大影响。

This project is aimed at studying fundamental issues related to the development of a new, efficient high-temperature oxygen sorption process based on perovskite-type ceramic sorbents for oxygen removal and air separation. The new sorption process takes advantage of the unique properties of certain perovskite-type ceramics which can adsorb a large quantity of oxygen, but not other gases, at high temperatures (300-800oC). Three perovskite-type ceramic materials with different compositions are selected as the sorbents for this study. The sorbent pellets and particles of various sizes are prepared by citrate and press-sintering methods. The thermodynamic defect equilibrium for oxygen sites in these ceramics is being studied experimentally by the gravimetric method and theoretically using point-defect and cluster-defect models. This defect equilibrium study provides oxygen-sorption isotherm data for these sorbents. Heat of sorption and order-disorder phase transformation of these ceramic sorbents is studied also by TGA/DSC. Oxygen sorption kinetics on these ceramic sorbents are investigated experimentally by the transient gravimetric method and modeled using a simple linear-driving-force model and a more complex model based on the ambipolar diffusion theory. The chemical and mechanical stability of the ceramic sorbent particles is being studied systematically by dilatometry and attrition tests. Finally, fixed-bed experiments for oxygen removal or air separation are conducted to obtain data for design of a practical separation process based on this new concept. This project represents the first effort in developing sorption processes based on this new group of non-traditional sorbents. On the fundamental side, this project may lead to development of a large number of new sorption processes with unique separation characteristics that are not offered by the traditional sorption processes. If a hydrocarbon is used to regenerate the sorbent, this process can be extended to provide new chemical reactors for partial oxidation of hydrocarbons with improved selectivity. On the practical side, the proposed sorption process is based on perovskite-type ceramics with preferential equilibrium sorption for oxygen. Successful development of this sorption process will have a significant impact on industrial processes for air separation and oxygen removal.