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Area of Technology:Chemical and Allied

Title of the Innovation: Solvent Extraction based Dearomatization Technology for Processing Straight Run Naphtha for Production of High Purity BTX

Brief About Innovation


A naphtha cracker is the heart of any petrochemical complex. Selection of cracker feedstock is one of the most important issues as it not only affects the yield and quality of products but also cracker furnace operation. Keeping this in mind, the preferred feedstock is low aromatic content naphtha (<12% of aromatics). Aromatics are undesirable as they do not add any ethylene value due to their refractory nature and produce undesirable black oil. However, maintaining constant supply of low aromatic naphtha is not an easy task due to quality and price fluctuations in the market. On the contrary running naphtha crackers at full capacity is critical for operating all downstream plants at full capacity.

To process this off spec naphtha, one innovative approach is to extract pure aromatics and use the aromatics lean raffinate as naphtha cracker feedstock. Aromatic extraction technology exists for aromatic rich feedstocks with aromatic content more than 65% and naphthene content less than 2% such as reformate and hydrogenated pyrolysis gasoline (HPG).

In off spec naphtha, the aromatic content is around 10-15%, and the naphthene content is more than 25%. 
The ratio of aromatics to naphthenes (impurities) is 15 to 20, in the conventional feedstock such as reformate while in the naphtha cracker feedstock this ratio is less than 1. This makes the process to produce pure (benzene, toluene, and xylene) BTX from the said off spec naphtha highly challenging with need for innovations.

The solvent extraction technology developed by CSIR serves a dual role of recovering high purity aromatics (BTX) and producing valuable Aromatics Lean Naphtha Cracker Feedstock (ALNCF) using solvent extraction from Straight Run Naphtha (SRN). The technology can produce ALNCF with a total aromatics content of less than 3 wt. % and high purity Benzene and Toluene (purity more than 99 wt. %) with more than 98 % yield.

Process Highlights:

1.    Solvent Extraction is the most suitable process operation for de-aromatizing petrochemical feedstocks having a wide boiling range like SRN, Pyrolysis Gasoline, Reformate, etc.
2.    Initial capital expenditure may be higher but operational costs are significantly lower than Extractive distillation.

3.    Purity and yield of products are both high 

4.   Product purity and yield may be tailored by varying process parameters and configuration 
5.   Solvent Extraction is not as energy intensive as Extractive Distillation 
6.   Solvent System used is well established, versatile, tunable as per product requirements, thermally and oxidatively stable 
7.   The process is heat integrated to minimize utility requirements 
8.   Adequate measures have been taken to prevent solvent contamination of the final products 
9.   Process recycle loops minimize solvent loss through the product outlet lines