A new process for recovering propylene and propane from propylene oxide off-gases

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The main production processes for propylene oxide include the chlorohydrin method, the co-oxidation method, and the direct oxidation method. In all of these processes, propylene is used as the raw material; after the reaction, some of the propylene does not participate in the reaction and is released as non-condensable gas. Although various measures are taken to recover this propylene, the exhaust gases still contain high levels of propylene and propane, which not only pollutes the environment but also results in significant waste of energy. The composition of this exhaust gas is quite complex, making its recovery difficult. The presence of oxygen in it poses safety risks, and this has always been a challenge in this industry. Building on our successful experiences in recovering propylene and propane exhaust gases from refineries and butyl acetate production, we have developed a process that combines low-temperature absorption with purification, tailored to the characteristics of propylene oxide exhaust gases. This approach involves first separating propylene and propane from inert gases before proceeding with purification, thereby significantly improving the recovery efficiency compared to condensation methods. The resulting product can be used directly, yielding substantial economic benefits. This process is applicable to the propylene oxide production methods based on the chlorohydrin route, co-oxidation method, and direct oxidation method, and it represents an advanced technology for energy conservation and emission reduction.