High-Temperature Sorption Process for Oxygen Removal and Air Separation

本项目旨在研究开发一种新型、高效的钙钛矿型陶瓷吸氧剂用于除氧和空气分离的高温吸氧工艺的基本问题。新的吸附工艺利用了某些钙钛矿型陶瓷的独特性能，这种陶瓷可以在高温(300-800摄氏度)下吸附大量氧气，但不能吸附其他气体。本研究选用三种不同组成的钙钛矿型陶瓷材料作为脱附剂。采用柠檬酸盐法和压烧法制备了不同尺寸的脱硫剂颗粒和颗粒。用重量法，结合点缺陷模型和团簇缺陷模型，从实验上研究了这些陶瓷中氧位的热力学缺陷平衡。该缺陷平衡研究提供了这些脱硫剂的氧吸附等温线数据。用热重分析/差示扫描量热法研究了这些陶瓷吸附剂的吸附热和有序-无序相变。用暂态重量法对这些陶瓷吸附剂的吸氧动力学进行了实验研究，并用简单的线性驱动力模型和基于双极扩散理论的较复杂的模型进行了模拟。通过膨胀和磨损试验系统地研究了陶瓷吸附剂颗粒的化学稳定性和机械稳定性。最后，进行了除氧或空气分离的固定床实验，为基于这一新概念的实际分离工艺的设计提供了数据。该项目是开发基于这种新的非传统吸着剂的吸附过程的第一次努力。从根本上说，这个项目可能会导致大量新的吸附工艺的开发，这些新的吸附工艺具有传统吸附工艺所不具备的独特的分离特性。如果使用碳氢化合物再生吸附剂，则可以扩展这一过程，为碳氢化合物的部分氧化提供新的化学反应装置，并提高选择性。在实用方面，所提出的吸附工艺是基于钙钛矿型陶瓷，对氧具有优先平衡吸附。这种吸附过程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.