Reformed C9 Aromatics Firms Extend Industrial Chain

C9 heavy aromatics have nine isomers. C9 varieties that can be used in industry as products after separation include 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, m-ethyltoluene and p-ethyltoluene.

1,2,4-Trimethylbenzene: capacity in surplus

The output of reformed C9 heavy aromatics in China has increased considerably in recent years. Raw material sources for 1,2,4-trimethylbenzene are therefore enriched and the capacity has grown rapidly, reaching 248 kt/a in 2015, when the output was 125 kt.
1,2,4-Trimethylbenzene was in short supply in the market before 2014. But then, with the completion of several new units by Sinopec Anqing Petrochemical Co., Ltd., Liaoning Zhongke Petrochemical Group Co., Ltd., Qilu Petrochemical Co., Ltd. and Jiangsu Zhengdan Chemical Industrial Co., Ltd. in 2014, the capacity is in surplus today. The operating rate of production units is quite low, being around 50%.
1,2,4-Trimethylbenzene is mainly used in the production of trimellitic anhydride and trimethyl hydroquinone. The most important application is to synthesize trimellitic anhydride. Trimellitic anhydride is mainly used to produce the plasticizer trioctyl trimellate (TOTM), which has already gained full affirmation and development in market.
One plasticizer variety often used in the plastic industry is dioctyl phthalate (DOP). As phthalate plasticizers easily liberate benzene and cause hazards to human bodies, laws and regulations of EU have restricted their use in PVC products. With adjustments to industrial policies and improvements on product standards made in China, TOTM will gradually replace DOP and the market of trimellitic anhydride will turn still better.
Trimethyl hydroquinone is mainly used in the synthesis of vitamin E. It is also used as monomer for heat-resistant polyphenyl ether engineering plastics, raw material for plastic alloys and raw material for some pesticides and antiseptics. There are two main trimethyl hydroquinone synthesis routes. One is the m-cresol methylation route. The other is the 1,2,4-trimethylbenzene catalytic oxidation route. The supply of m-cresol in China is very tight today. The price of 1,2,4-trimethylbenzene is relatively low. Enterprises in China already use the 1,2,4-trimethylbenzene route to produce trimthyl hydroquinone, but the market demand is quite small.

1,3,5-Trimethylbenzene: demand restricted by high price

The capacity to make 1,3,5-trimethylbenzene in China was 4.5 kt/a in 2015, when output was 2.8 kt. The main producers include Nanjing Hongshun Petrochemical Co., Ltd., Jinzhou Kaiyuan Petrochemical Co., Ltd. and Langfang Tianda Petrochemical Plant. But Jinzhou Kaiyuan Petrochemical Co., Ltd. has been idle for many years. The operating rates of Nanjing Hongshun Petrochemical Co., Ltd. and Langfang Tianda Petrochemical Plant are around 80%.
Both the quality and the output of 1,3,5-trimethylbenzene in China can meet the needs in the downstream market. Small amounts are also for export.
In today’s slack chemical market, 1,3,5-trimethylbenzene is a product with high added value. The high price has however restricted the development of its downstream demand. 1,3,5-trimethylbenzene is only used in the dyestuff and pesticide sectors today, and the demand is not big either. With the reduction of the its production cost, the production of its downstream products will enter a stage of stable development and the market of 1,3,5-trimethylbenzene will be stable with growth in the future.

Technology taken as guide, development prospect promising

Among continuous-reformed C9 heavy aromatics 1,2,4-trimethylbenzene holds the highest proportion of around 25%. As boiling points of various components in feedstock are quite close, precise rectification must be used to separate high-purity 1,2,4-trimethylbenzene. Advances in technologies for 1,2,4-trimethylbenzene made in recent years are mainly energy conservation/consumption reduction in production units and co-production of high-purity 1,3,5-trimethylbenzene.
Five technologies for the production of 1,2,4-trimethylbenzene with continuous-reformed C9 heavy aromatics as raw materials have already applied for state patents in China.
The mass fraction of 1,3,5-trimethylbenzene in heavy aromatics is around 10%. Its boiling point is 0.3℃ lower than the boiling point of adjacent component o-ethyltoluene and 2.7℃ higher than the boiling point of p-ethyltoluene. They can hardly be separated through conventional rectification. Five technologies for the production of 1,3,5-trimethyl benzene with continuous-reformed C9 heavy aromatics as raw materials have also applied for state patents in China.
In 1,3,5-trimethylbenzene separation units already commercialized in China today, Langfang Tianda Petrochemical Plant uses the additive rectification process technology from Tianjin University, Nanjing Hongshun Petrochemical Co., Ltd. uses the isomerization rectification process technology and Jinzhou Kaiyuan Petrochemical Co., Ltd. uses the alkylation rectification process technology.
Overall, the reformed C9 heavy aromatics sector in China should base itself on large 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzne extraction units, highlight industrial integration and develop downstream products, especially products with sound development prospects and high added value such as environment-friendly plasticizers, green antioxidants, important fine chemical intermediates, and new material monomers and assistants.