Propylene oxide (PO) is a very important material driving the development of the chemical industry, while the environmental issues on its traditional production processes have been increasingly prominent. From high-polluting production methods to the exploration and practice of green synthesis, the eco-awakening in PO production not only reflects the advancement of industry technology but also demonstrates a commitment to sustainable development.
I. Problems with Traditional Processes
In the past, the main production process of PO was the chlorohydrin method. Although this method is mature and simple in process, the environmental effects cannot be overlooked. A large amount of saline wastewater and organic chlorides would be generated via the chlorohydrin method. These wastewaters contain high-concentration organic compounds, heavy metal ions, and difficult-to-degrade by-products, causing severe pollution to water and soil. Besides, the use of chlorine gas as one of the raw materials poses significant safety risks in its storage, transportation, and handling processes.
II. Practices of Innovative Processes
1. Eco-Awakening: Environmental Awareness and Policy Guidance
Due to increased environmental awareness and sustainable development strategies around the world, the green development of the PO industry is gradually gaining considerable interest. Various countries have introduced relevant policies to restrict the development of highly polluting production processes and to encourage and support the research and application of green synthesis technologies.
China has introduced a series of more stringent environmental policies. And the chlorohydrin process has been gradually obsoleted. This policy provides strong support for the green development of PO production.
2. Eco-Exploration: Rise and Application of Green Synthesis
The Hydrogen Peroxide to Propylene Oxide (HPPO) process stands as an eco-friendly and cost-efficient synthesis of PO. It uses a mixture of propylene, hydrogen peroxide, and methanol/water as raw materials to undergo a selective oxidation reaction under the catalysis of titanium silicate, producing PO. This process not only has high raw material utilization efficiency but also generates water as the only byproduct. Moreover, the HPPO process operates under low temperature and low pressure conditions, reducing energy consumption and safety hazards. Several companies in China have achieved scale application of HPPO process and gotten decent economic and environmental benefits.
3.Eco-Practices: Innovation in Wastewater Treatment Technologies
Innovative wastewater treatment technologies are equally important in the green synthesis of PO. Researchers have developed various efficient treatment processes and techniques for the wastewater generated by the HPPO process. For instance, employing processes like “advanced oxidation pre-treatment - biological pre-oxidation - coupled biological enhancement” can significantly reduce the concentration and toxicity of organic compounds in wastewater and achieve standard discharge for wastewater. Simultaneously, by utilizing resource recovery technologies, useful components in wastewater can be recycled to improve resource utilization efficiency.
III. Prospects for Sustainable Development
As a crucial chemical raw material, the production technology of PO has been continuously innovated and developed. Here are the latest patents or technological advancements in this field:
1. Latest Patents
In November 2023, Wanhua Chemical applied for a patent on the recycling of cumene, which involves distillation and alkaline washing to remove impurities, controlling the ratios and contents of cyclohexanol and phenol, enhancing the reuse of cumene and the recycling rate, thereby effectively reducing production costs.
In April 2024, Sinopec applied for a patent on catalysts for the copolymerization of carbon dioxide and propylene oxide. The catalyst is composed of zinc compounds and magnesium compounds, with simple preparation method, exhibiting high activity and excellent selectivity. It helps produce copolymers with high average molecular weights and low polyol content.
In July 2024, Sinopec obtained a patent for the preparation method and product of propylene oxide, involving multiple processes such as oxidation, epoxidation, product separation, and benzyl alcohol conversion, with impurity removal process to enhance product yield and reactor system efficiency.
These innovations have not only improved production efficiency but also reduced production costs and energy consumption, driving the PO industry towards a sustainable future. With advances in technology and increasing environmental awareness, more green synthetic technologies are expected to emerge and be applied. Continuous innovation and improvement in wastewater treatment will provide robust support for the green production of PO. Furthermore, the integrated development of industry chain, by integrating upstream and downstream resources to achieve the reuse of raw materials and reduce waste emissions, can significantly lower production costs, mitigate environmental pollution, and contribute to the green development of propylene oxide.
