Following the explosion occurred at the hydrogen peroxide production area of Luxi Chemical, a subsidiary of Sinochem Holdings, on May 1, which resulted in 9 deaths, 1 injury, and 1 person missing, another explosion occurred in the hydrogen peroxide workshop at Risun Chemical on September 14. It is the second major hydrogen peroxide accident that has occurred within China in 2023.
Why is hydrogen peroxide so dangerous?
Electrolysis, anthraquinone (AQ), isopropanol oxidation, electrochemical cathode reduction of oxygen, and auto-oxidation (AO) are commonly used in the production of hydrogen peroxide. The AQ method is currently the most mature method, and over 99% of hydrogen peroxide plants in China use this technology. The AQ process for hydrogen peroxide production has a high hazard coefficient. It involves using hazardous raw materials and going through hazardous processes to produce a hazardous product.
The first reaction in the production process of hydrogen peroxide, namely hydrogenation, is a hazardous chemical process that is subject to strict regulation. It has the following hazardous characteristics: (a) The reactants have explosiveness, and the explosion limit of hydrogen gas is 4-75%, making it highly flammable and explosive. (b) Hydrogenation is an exothermic reaction, and when hydrogen gas comes into contact with steel under high temperature and pressure, carbon molecules in the steel can react with hydrogen gas to form hydrocarbons, reducing the strength of the steel equipment and causing hydrogen embrittlement. (c) The regeneration and activation of catalysts can easily cause explosions. (d) The exhaust gas from the hydrogenation reaction contains unreacted hydrogen gas and other impurities, which can easily cause ignition or explosion during discharge. The second reaction in the hydrogen peroxide production – oxidation - is also a hazardous chemical process that is subject to strict regulation. It’s hazardous because that the peroxidation process has a strong risk of decomposition and explosion due to the presence of peroxide groups (-O-O-).
Hydrogen peroxide is currently an important raw material for the production of propylene oxide. The concentration of hydrogen peroxide products in China is mainly 27.5%. However, in recent years, there has been an increasing demand for high concentration products (>50%), as the use of high concentration hydrogen peroxide can effectively improve the production efficiency and product quality. The HPPO process often uses hydrogen peroxide with a concentration of 50% to 70%.
Currently, the key players in China’s HPPO-based propylene oxide industry are Jilin Shenhua and Sinopec Changling. In 2011, Jilin Shenhua introduced HPPO technology from Degussa and Uhde, with an investment of CNY 2.5 billion, and built the first and largest HPPO plant in China with a scheduled capacity of 300 ktpa. The plant started operations in July 2014. In 2013, Sinopec planned to adopt independently developed HPPO technology and invested about CNY 1.28 billion to build a 100 ktpa industrial plant at the company’s Changling Branch. The plant was completed in July 2014, and successful trial operation was conducted on December 6 of the same year. This marked Sinopec as the third company in the world to own the patent for producing propylene oxide using hydrogen peroxide technology, breaking the monopoly of foreign countries on this technology.
In addition to the aforementioned two producers, Taixing Yida Chemical (independent R&D), Qixiang Tengda (authorized by Evonik and ThyssenKrupp Uhde), Jincheng Petrochemical (independently developed by China Tianchen Engineering), and Jiahong New Material (using the process owned by China Catalyst Holding Co., Ltd) have also successfully operated their HPPO facilities in recent years. The current production capacity of HPPO (Hydrogen Peroxide to Propylene Oxide) plants in China has reached 1.55 mtpa.
However, the current stability of HPPO facilities is poor, with frequent shutdowns and maintenance issues. Although there are many newly completed or planned HPPO projects, there are still significant uncertainties and obstacles. The main reasons are as follows:
1) Inadequate hydrogen peroxide supply: Due to its unstable and highly explosive nature, hydrogen peroxide cannot be transported over long distances. It has a limited sales radius (300-500 km). Currently, hydrogen peroxide production in China is mainly concentrated in East China (63%), North China (6%), and Central China (14%), primarily located in chemical-intensive provinces such as Shandong, Hubei, Jiangsu, and Zhejiang. Southwest (4%), northwest (2%), and northeast (6%) regions have minimal production capacity, resulting in an imbalance between production layout and market size. On one hand, in some areas with concentrated downstream industries, there is a supply shortage of hydrogen peroxide, resulting in high transportation costs. On the other hand, some regions have excessive production facilities, with capacity far exceeding demand. Therefore, the issue of hydrogen peroxide supply needs to be addressed. The construction of new hydrogen peroxide plants requires sufficient hydrogen resources and faces difficulties in approval due to the classification of hydrogen peroxide as a hazardous chemical.
2) The production requires high-concentration hydrogen peroxide, while the preparation of high-concentration hydrogen peroxide presents certain difficulties. Currently, in Jilin Shenhua’s plant, the required 70% hydrogen peroxide is supplied by Evonik. The high cost leads to poor profitability of the plant.
3) In the HPPO process, hydrogen peroxide has high activity and can produce some aldehyde impurities during the production process, which can have an impact on downstream production.
