Process for the production of LPG and high octane aromatic hydrocarbons from non-economically viable petroleum feed stock

#The present invention relates to an improved process for the preparation of liquified petroleum gas (LPG) and high octane aromatic hydrocarbon from non-economically viable petroleum feed stocks over a novel zinc aluminosilicate molecular sieve catalyst. The present invention particularly relates to a process for the preparation of LPG and aromatic hydorcarbons such as benzene, toluene, ethylbenzene and xylene(BTX) from petroleum feed stocks such as aromatic extraction raffmates, light naphtha straight run naphtha over a zinc-aluminosilicate molecular sieve catalyst.

#Proposed lead phase-out in Indian Gasoline and changing international petroleum market have led to large and rapid variations of feed costs and availability. In the present scenario, an important factor to boost profitability is to take advantage of those variations and to produce high value and high demand products. Different petroleum feedstocks such as aromatic extraction raffinate and naphtha, specially light naphtha are considered only as fuel or feedstock for stem cracking and syngas production during long periods. This is due to high vapour pressure (RVP) and low octane rating of these feedstocks. They are also non-reformable by conventional catalytic-reforming processes. These non-economically viable petroleum feedstocks can effectively be converted to valuable aromatics such as LPG and other useful by- products.

#In India, total naphtha production in 1991-92 was 3.85 MMTPA which is expected to increase to 6.98 MMTPA by 1996-76. During the same time, the demand for high octane gasoline and LPG is expected to increase drastically. At the end of 9th Indian five year plan (2001-2). The deficit between production and demand for LPG is projected to be 5.837 MMTPA ; while that for motor gasoline will be 1.524 MMTPA. Hence, good amount of foreign exchange has to be spent to import these two products as the demand can not be set by indigenous resources.

#This example describes the results using aromatic extraction raffinate as feed. The zinc-aluminosilicate molecular sieve catalyst has a composition containing 0.8 wt % Al (as Al.sub.2 O.sub.3) and 3.3 wt % Zn (as ZnO) on an anhydrous basis. The total metal content of Na, Fe, Ca, Pt, Sn and/or Re in the catalyst is up to 0.5 wt %. Same catalyst was used for all further studies. The activity results of two different temperatures and feed characteristics are presented in Table 1.

#TABLE 1 ______________________________________ Aromatic Extraction Raffinate as feed:Effect of Temperature Catalyst: Zinc-aluminosilicate; feed: Aromatic extraction raffinate; Pressure: 10 kg/cm.sup.2 ; Space velocity: 2 hr.sup.-1 ; N.sub.2 /HC: 2; Time-one-stream: 2 hr. Temperature (.degree. C.) 400 500 ______________________________________ Feed Characteristics IBP 46.1 FBP 131.9 Density 0.686 Product Composition Conversion (wt %) 89.7 96.4 Selectivity (%) Methane 5.7 Ethane + Ethylene 10.5 9.3 LPG 52.9 n-pentane + isopentane 1.7 0.9 Aromatics 31.3 ______________________________________

#This example explains the effect of time-on-stream when aromatic extraction raffinate was used as feed. The product analysis are presented in Table 2. With increase in time-on-stream fall in convention from 96.4 to 93.7 wt % was observed. But at the same time it resulted in increase in aromatic selectivity from 31.3 to 34.6% and decrease in LPG selectivity from 52.9 to 48.3.