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Light naphtha is currently in surplus in our hydrocarbon industry as its high RVP and low RON, limits its use as ablending agent in gasoline pool. Moreover, lack of off-take of naphtha by other user industries such as petrochemicalsand fertilizers also lead to surplus. In addition to this, quantity of NGL (natural gas liquid), a gas condensate left behindafter gas production is increasing due to increase in discovery of new gas reservoirs. These feed stocks containconsiderable amounts of C5-C6 paraffins (40-70%) and cannot be converted to value added products by existingtraditional processes. On the other hand demand for propane and butane (Liquefied petroleum gas) is increasing ata growth rate of over 14% per year in the country and is expected to accelerate in the future as a result of future useof LPG as a clean transport fuel. The conventional production of LPG from gas fields and refineries is not adequate tomeet this deficit.
Keeping in view of above need, a novel zeolite based catalyst and process was developed at IIP to convert lightnaphtha/NGL to LPG and high octane low sulphur gasoline blend stock. It was thoroughly evaluated on both puremodel compounds and commercial light naphtha/NGL stocks. The catalyst used in this process is eco-friendly doesnot involve acid leaching with mineral acids such as HCl. This innovative process ensures that n- and i-paraffins arecracked to smaller fragments. The olefin fragments formed by the primary cracking undergo various secondary andtertiary reactions like oligomerisation cracking, cyclization, hydrogen transfer and aromatization reactions. LPG isformed as major product by the primary cracking whereas good amount of aromatics are formed as byproduct by theother secondary reactions such as dehydrogenation oligomerisation and cyclization reactions. By suitable choice ofprocess variables and catalyst formulation, production of C3 and C4 paraffins can be optimized. The overall productsare fuel gas, LPG and a C5+ liquid with BTX aromatics which can be used as an excellent feedstock for petrochemicalsbesides gasoline blend stock.
After successful demonstration of this process at bench scale, IIP approached Gas Authority of India (GAIL) for usingthis NTGG technology (Naphtha/NGL to Gas and Gasoline) at one of their LPG recovery sites. GAIL approved the NGLvalue addition project at total cost of rupees 16.5 crores for the unit of 8000 TPA to put up the NTGG plant at Vaghodia.On August 6, 2002, IIP and GAIL demonstrated the NTGG process successfully and on-spec products produced withina record time of less than four hours.
The developed process is of great relevance to the Indian hydrocarbon industry as it addresses the light alkaneutilization on one hand and the production of LPG along with high-octane low-benzene and low sulphur gasoline onthe other. This development has indeed been a breakthrough in terms of developing world scale technology suited toIndian requirements as there is a great demand for LPG in India where as in western world LPG is in surplus and isbeing converted to BTX aromatics. To our knowledge this is the first grass root plant constructed and commissionedin the hydrocarbon sector based on indigenous catalyst and know-how. Complete plant design, plant configuration,catalyst know-how and scale-up have been provided using indigenous capabilities. It is to be noted that IIP scaled upthe catalyst from milligram to tones level and performance of the catalyst has been found to excellent even till today.This is the first catalyst-based unit which brings India to the world map of providing know-how to build and operatesuch unitssuccessfully. GAIL has been operating this unit continuously and successfully over the lastseven yearsand has derived substantial financial benefit out of this technology. intends to expand this technology to other placesnamely PATA and Vijaypur with enhanced processing capacity.
An enormous amount of NGL is available in India from various gas fields. If the NTGG plant can be coupled withthese units at remote locations, the production of LPG and gasoline can be achieved by eliminating the difficulty intransportation of NGL. This will contribute to reduce LPG demand in our country and has considerable export.
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