Title of Invention

"A PROCESS FOR CONVERTING THE C5-C6 PARAFFINS RICH LIGHT NAPHTHA CUT INTO AROMATICS AND LPG"

Abstract

The present invention relates to a process for converting the C5-C6 paraffins rich light naphtha cut into aromatics and liquefied petroleum gas. In the present invention, C5-C6 paraffins in light naphtha cut are converted into aromatics and liquefied petroleum gas with gallium containing zeolite catalyst promoted by group VIII metal. Light naphtha, which does not have potential use as conventional reformer feed stock, can be used as a feed in this process.The catalyst used in this process is ecofriendly and it does not involve the acid leaching with hazardous mineral acids such as HC1 during preparation. The catalyst used in this process reduces dry gas yields to 12-wt% with increase of high-octane liquid product and thereby improves the economics of this process.

Full Text

The present invention relates to a process for converting the C5-C6 paraffins rich light naphtha cut into aromatics and liquefied petroleum gas. Particularly the present invention relates to a process for converting the C5-C6 paraffins light naphtha cut into aromatics and liquefied petroleum gas with gallium containing zeolite catalyst promoted by group VIII metal. More particularly the present invention relates to a process for the effective utilization of straight run light naphtha feedstock available from various refineries, into value added (Benzene, Toluene, Xylene, BTX) aromatics which can be used as petrochemical feed stocks or gasoline blending stocks. In addition to aromatic rich liquid product, some amounts of gas by-product are also obtained which can be used as domestic fuel (Liquefied Petroleum Gas, LPG). The recent changes in gasoline specs demands for high-octane with lower Reid Vapor Pressure(RVP). Since, light naphtha has high RVP and low octane number, it's blending into the gasoline pool beyond a certain limit is not acceptable. This has resulted into pile up of excess Light Naphtha fraction stock in refineries. To be able to use this excess stock of light naphtha effectively, the valorization of this cut was explored. This cut predominantly consisted of C5-C6 hydrocarbons and possibility of converting this to aromatics and propane, butane mixture was considered to be a good option. Light naphtha is one of the least viable petroleum feed stocks treated today. Projected production of straight run light naphtha cut (IBP-130°C) other than catalytic reforming feed in India indicates 1-1.25 MMTPA (million metric tons) of light naphtha is available from various refineries in 1996-97. Light naphtha mainly contains C5 and CV, hydrocarbons (40 to 50 wt%) depending upon the source. Due to high percentage of n-paraffins in light naphtha it has lower octane number and high RVP due to n- and i-pentanes, hence it cannot be used directly for gasoline blending. To address the benzene problem in gasoline it is suggested to increase IBP of reformer feed by adjusting naphtha splitter cut point, which leads to substantial loss in gasoline production volume besides increased quantities of light naphtha. Thus, the conversion of light naphtha into other petroleum and petrochemical products gains significance in this scenario. In addition to this, the demand for LPG is also growing much faster in India at growth rate of 14 percent per year. The production of LPG in the year 1999-2000 was 2.487 MMT with consumption of 8.029 MMT with a corresponding deficit of 5.542 MMT (Ministry of Petroleum and Natural gas "Report on basic statistics in Petroleum Products in India 2001). This disparity between LPG production and consumption patterns may expect to increase further by 2010-11 due to increase in use of LPG in domestic and automobile sector. Therefore the major concern of Indian refinery would be to have secondary refinery process to increase the production of LPG. As a result increasing interest is shown in the development of new catalysts and processes, which allow production of Valuable aromatics and LPG, making use of unconventional low value feed stock such as light naphtha. Conventionally, aromatics are being produced from the catalytic reforming process of naphtha units from various refineries. Naphtha to be used as a raw material is usually from fractions having boiling points in the range from 60-150°C. The catalyst used for reforming process is monometallic Pt/A12O3 °r Pt-Re/A12O3 bimetallic catalyst. Although these processes are used all over the world, there are number of limitations in the use of these catalysts. The conventional catalyst is not effective in promoting aromatization of light naphtha rich in C5 hydrocarbons because a rate for the conversion to. The catalyst is also not very effective in promoting the aromatization of straight chain paraffins such as n-hexane and n-heptane present in the feed that remain unconverted. Reforming process requires an organic chloride additive to provide the proper balance between acid and metal function. During the process, the organic chloride decomposes into hydrochloric acid, a waste product leads to corrosion of equipment. On the other hand, LPG production either from refineries or from gas fields is not enough to meet the demands. The import situation is also not encouraging, as only a few private entrepreneurs have actually created facilities for import market. Thus, there is a considerable incentive for conversion of these low value feed stocks to high value products such as aromatics or LPG. Similarly, conversion of other unconventional feedstocks such as natural gas liquids and raffinates into gasoline and LPG also gains significant importance in this scenario. Besides, It can also effectively help to meet the challenges posed by environmental regulations by converting these in to low RVP, high-octane aromatic rich blend stocks. The conversion of light hydrocarbons to aromatic hydrocarbons over modified zeolites such as ZSM-5 systems, which are acidic molecular sieves, is known. Modified ZSM-5 zeolite catalysts have been used to catalyze both paraffin dehydrogenation and olefin dehydrocyclo oligomerization. These catalysts provide shape selectivity such that large fractions of C10+ products are avoided. Various modifications and pretreatments of zeolite catalyst have resulted in improvement in light hydrocarbon conversion and aromatic selectivity, though often one has been achieved to the slight detriment of the other. There are reports in the literature on the conversion of these straight chain paraffins into aromatics, using zeolites and metal-doped zeolites as catalyst. Reference may be made to a process developed by Mobil researchers (Ind. Eng. Chem. Process. Design Dev., 25 (1986) 151wherein the preparation of aromatics from variety of feedstock such as pyrolysis gasoline, unsaturated gases from catalytic cracker, paraffinic naphtha and LPG have been described. The process utilizes purely acidic HZSM-5 catalyst. Another reference may be made to (J.R.Bernad in Pro.5th International conference on zeolites Edited by L.V.C.Rees, held in Heydon, London, 1980, p.686) wherein method of producing aromatics from non-acidic alkaline-L zeolite catalyst has described. The limitation of this process is that it is very sensitive to sulphur in feed even in ppm level (5ppm) Another reference may be made to (Hydrocarbon Processing Sept., 1989 p 72) wherein a process developed jointly by UOP Inc. and British Petroleum, based on gallium doped zeolite catalyst has been reported. In this process LPG was converted into BTX aromatics and the process has been demonstrated in a large-scale pilot plant of the British Petroleum Grangemouth refinery in Scotland. Yet another reference may be made to (US patent 5,026,938 dated 25th June' 1991) wherein a process for converting a gaseous feed stock containing C3-C5 paraffins into aromatics hydrocarbons by contacting the feed with gallosilicate molecular sieve catalyst has been described. The draw back of all these processes is that these are mainly related to the production of aromatics from paraffins of C3 - C5 range which are in high demand as LPG in India. Still another reference may be made to Sekiyu Gakkaaishi 37(1) 77,1994, wherein the use of Zinc aluminosilicate catalyst for the production of aromatics from light naphtha has been described. The limitation of the above process is vaporization of zinc from zinc containing HZSM-5, which occurs in reducing conditions despite its high activity in Aromatization. Still another reference may be made to (US patent No. 4,861,934 dated Aug, 29, 1989) wherein a process for the conversion of light hydrocarbon containing C2-C7 paraffins and C2-C7 olifins to high-octane gasoline using aluminogallosilicate has been reported. The disadvantage of above process is that it operates at high severity of operating conditions i.e., Temperature: 540°C, LHSV: lhr-1. Still another reference may be made to (US patent No. 5,013,423 dated May, 07, 1991) wherein a process for the conversion of C6-C7 paraffin rich light naphtha feed to aromatics over non acidic platinum indium containing high silicalite zeolite has been reported. The limitation of this process is that it utilizes isomer free n-paraffins as feedstocks and zeolite catalyst is having high loading of platinum i.e., 2.88% by weight of catalyst. The shortcomings of the above processes are firstly formation of high quantity (15-20wt %) of dry gas (C1+C2) during the reaction, which will be a loss to the economy of the process. Secondly the hydrogen gas is used in this process during feed cut in which increases the overall cost of the process. The main object of the present invention is to provide a process for converting the C5-C6, paraffins rich light naphtha cut into aromatics and liquefied petroleum gas. which obviates the drawbacks as detailed above. Another object of the present invention is to provide a process for converting the C5-Cf, paraffin rich light naphtha light naphtha cut to aromatics and liquefied petroleum gas with gallium containing ZSM-5 catalyst promoted by group VIII B metal. Still another object of the present invention is to provide a process for the conversion of light naphtha into high octane aromatic rich unleaded gasoline as a blender to boost the octane number along with LPG as by product by using a catalyst system containing group VIII B metal promoted gallium supported HZSM-5 zeolite composite. Yet another object of the present invention is to provide a process, which utilizes the straight run light naphtha containing 5 types of hydrocarbon components for the production of BTX aromatics unlike the other existing processes. Yet another object of present invention is to convert C5 - C6 paraffinic components efficiently and effectively to produce aromatic rich high-octane gasoline unlike the conventional reforming processes. Yet another object of present invention is to provide a process that produces LPG with low yields of low cost dry gas (C1+C2) from light naphtha cut. Yet another object of present invention is to develop above process, which is safe and environmentally acceptable. Accordingly the present invention provides a process for converting the C5-C6, paraffins rich light naphtha cut into aromatics and liquefied petroleum gas which comprises a) Incipient wetness impregnation of Group III A metal preferably gallium with 0.5 to 8% by weight to dried HZSM-5 zeolite extrudate, b) further impregnation of Group VIII B metal preferably platinum with 0.01 to 2 wt% to the above said dried gallium containing HZSM-5 extrudates, c) loading the above said platinum promoted gallium supported HZSM-5 catalyst in high pressure bench scale reactor (14 g catalyst capacity) and reducing it by passing hydrogen for a period of 2-5 hours at a temperature of 400-550°C at a flow rate of 14-20 1/h in to the reactor, d) cooling the above said platinum, gallium containing zeolite bed to a temperature of about 300°C under nitrogen atmosphere and increasing thereafter further bed temperature to 300-600°C, e) contacting light naphtha as feed stock containing hydrocarbon having carbon atoms in the range of C5-C6 with the catalyst bed in reactor at a weight hourly space velocity ranging from of 0.5 to 8 hrs-1 at a pressure in the range of 1 to 20 kg/Cm2 for at least 24 hours in the absence of nitrogen gas, 0 separating BTX rich C5+ liquid and LPG and other products of the resultant reaction mixture from the reactor by known methods g) carrying out in-situ regeneration of catalyst in reactor for at least 14 hours by oxidative combustion. In an embodiment of the present invention the feedstock used may be such as light naphtha cut containing non-cyclic C5 to C6 range paraffins. In another embodiment of the present invention the catalyst used may be regenerated by oxidative combustion, which is carried out in two steps. In yet another embodiment of the present invention the first step of regeneration is carried out at a temperature in the range of 375-400°C in the presence of oxygen in the range of 0.2 to 1.5 vol%. In still another embodiment of the present invention the second step of regeneration is carried out at a temperature in the range of 450-525°C in the presence of oxygen in the range of 1.5 to 3 vol%. In still another embodiment of the present invention weight hourly space velocity is preferably in the range of 1 to 3 hr-1. In still another embodiment of the present invention the reactor temperature is preferably in the range of 460-480°C. In still another embodiment of the present invention reactor pressure is preferably in the range of 2-5 kg/Cm2. In still another embodiment of the present invention the process conditions viz space velocity can be varied in order to increase the aromatic content and decrease the LPG in product mixture advantageously. In still another embodiment of the present invention the catalyst system contains platinum promoted gallium supported ZSM-5 zeolite composite used is such as prepared by incipient wetness impregnation method. In still another embodiment of the present invention the catalyst used is prepared from the Group III A metals preferably gallium with 1.5 to 3wt% to dried HZSM-5 zeolite extrudate. In still another embodiment of the present invention the catalyst used is prepared from the Group VIII B metal preferably platinum with 0.05 to 0.3-wt% to dried gallium supportedHZSM-5 zeolite extrudate. In still another embodiment of the present invention the gallium containing HZSM-5 catalyst promoted by group VIII B metal is incorporated into matrix material includes synthetic or natural occurring substances such as clay, silica, alumina. In still another embodiment of the present invention the relative proportion of ZSM-5 and matrix material on anhydrous basis may vary with ZSM-5 content ranging between 70-30% by weight. In the present invention, preparation of the catalyst for the process does not involve the steps of steaming and acid leaching before the actual catalytic application. The mentioned and claimed catalyst is environmentally friendly as the preparation does not involve the use of hazardous mineral acids, viz., HC1, HNO3 etc. The process steps are detailed below: About 18cc of the catalyst (13 g) in extruded form of 1.5 to 2 mm diameter is loaded in a fixed bed, down flow, high-pressure reactor, a-alumina is used as diluent to the catalyst with the ratio of 1: 2.5 by volume. Prior to the test runs, the catalyst is reduced at 500°C under H2 gas flow rate of 10 1/h for 4 hours. Later it is cooled down to 300°C in N2 flow and heated again to desired reaction temperature. Three independently regulated temperature controllers control the temperature of the reaction zone, pre and post heating zones. After attaining the desired process conditions, the nitrogen stream was replaced by straight run light naphtha feed vapour fed by plunger type feed pump. Reactor effluents are cooled before being fed to high-pressure separator. The vapors from separator are purged, while the liquid phase is sent to stabilizer column. Regeneration of the deactivated catalyst in reactor is carried out by conventional procedure using air and nitrogen mixture. The feed and Cs+liquid product is analyzed using a gas chromatograph fitted with OV-275, 30% packed column and a 25 mt DB-1 fused silica capillary column while the gaseous (C1-C5) fraction was analyzed by Hewlett Packard gas chromatograph model 5730 A fitted with a squalene column. In the present invention, the aromatics C9 and above have been reported as C9+ aromatics. In the present invention, the process conditions have been optimized for the controlled C1+ C2 (dry gas) yield, which is not desired in the gasoline process. In order to reduce the duration of regeneration of the catalyst thereby to improve the catalyst life against the coke lay down, 0.2 wt% of platinum metal is doped on HZSM-5 catalyst. In the present invention, the novel process developed can operate for maximization of LPG too by simply altering the process parameters. In the present invention, preparation of the catalyst for the process does not involve the steps of steaming and acid leaching before the actual catalytic application. The mentioned and claimed catalyst is environmentally friendly as the preparation does not involve the use of hazardous mineral acids, viz., HC1, HNO3 etc. The following examples are given by way of illustration of the present invention and therefore should not be construed to limit the scope of the present invention. EXAMPLE - 1 This example describes the results using C5-C6 non-cyclic paraffin rich light naphtha as feed. The Ga-alluminosilicate molecular sieve catalyst promoted by platinum has a composition containing 0.2 wt% Pt, 2.5wt% Ga on ZSM-5 with SAR 30-40. Same catalyst was used for all further studies. The hydrocarbon composition of the C5+ liquid product obtained in the present process from the light naphtha feed stock are shown in table-1. The total yield of C5+ liquid obtained is 34% and LPG is 36% on feed basis. The analysis is based on the GC fitted with Tetra Cyano Ethoxy Propionitrate column and FID detector. Table-1: Hydrocarbon composition of feed and liquid products Process conditions: Catalyst: Pt/Ga-HZSM-5; Feed: light naphtha, Reaction Temperature: 500°C; Pressure: 3kg/cm2; WHSV: 2h-1; TOS: 8 hrs; Reactor: Micro Reactor of 25 gm-catalyst capacity. (Table Removed) This table shows the conversion of light naphtha feed stock having RON of 74 into aromatic concentrates rich C5+ liquid product with delta RON gain by 30 units. This can be used as blending stock for gasoline pool or feedstock for petrochemical production. EXAMPLE - 2 This example illustrates the results of effect of temperature on product distribution of aromatics (BTX) in liquid product, LPG and dry gas. The gaseous and liquid products were analyzed by same method, which was mentioned in example -1. Table-2: Effect of temperature on product yields Process conditions: Catalyst: Pt/Ga-HZSM-5; Feed: light naphtha; Pressure: 3 kg/cm2; WHSV: 2 hr"1; TOS: 8 hrs (Table Removed) Table-2 shows that the yield of aromatics (BTX) increases with increase of temperature and the optimum temperature for the present process was chosen below 500°C due to formation of less coke lay down on catalyst at 475°C. C4and Cj hydrocarbon contains 0.5 to 1% of respective olefins in gas product. EXAMPLE- 3 This example includes the results of effect of pressure on the yields and composition of aromatics and LPG. The product analysis presented in table-3. Table-3: Effect of pressure on product yields Process conditions: Catalyst: Pt/Ga-HZSM-5; Feed: Straight run light naphtha; Temperature: 450°C; WHSV:2hr-1;TOS:8hrs (Table Removed) The experimental results reported in table-3 shows that the decrease of pressure increases the BTX production with decrease in yields of LPG. The optimum pressure for this process was kept at 3 Kg/cm due to more aromatic formation. EXAMPLE - 4 This example illustrates the results of effect of weight hourly space velocity on the yield and composition of high-octane gasoline and LPG. The product analysis presented in table-4. Table- 4: Effect of weight hourly space velocity on product yields Process conditions: Catalyst: Pt/HZSM-5; Feed: Straight run light naphtha; Temperature: 475° C; Pressure: 3 kg/cm2; TOS: 8 hrs (Table Removed) From the above table-4, it is shown that the increase of WHSV to 8 decreases the aromatic yield and LPG yields almost remain constant, while dry gas yields in increasing trend EXAMPLE -5 This example illustrates the effect of run length on the product yield viz. BTX, LPG and their composition. In the run length of 24 hrs, the product was analyzed at various intervals and results are presented in table-5. Table-5: Catalyst Stability Studies Process conditions: Catalyst: Pt/Ga-HZSM-5; Feed: Straight run light naphtha; Temperature: 475°C; WHSV: 2.0 hrs-1; Pressure: 3 Kg/cm2 (Table Removed) Table-5 shows consistent yield patterns of BTX in Liquid product and decrease in yields of LPG at WHSV of 2 hrs-1 persists over the run length of 24 hrs. The main advantages of the present invention are: 14. The process of the present invention converts low value petrochemical feedstocks into LPG and aromatic concentrates rich liquid product valuble in both petrochemical and gasoline market. 15. Light naphtha, which does not have potential use as conventional reformer feed stock, can be used as a feed in this process. 16. The catalyst used in this process is ecofriendly and it does not involve the acid leaching with hazardous mineral acids such as HC1 during preparation. 17. The catalyst used in this process reduces dry gas yields to 12-wt% with increase of high-octane liquid product and thereby improves the economics of this process. 18. LPG, which is a by-product in the present process, can meet the industrial and domestic demands. 19. The process does not require hydrogen during feed cut in. 20. The process also does not require use of corrosive organic chloride additives. 21. The high-octane liquid a major product obtained in the process can be used as a gasoline blender to boost octane number. 22. The process maintains constant production of high-octane gasoline pool by utilization of light naphtha from reformate. 10. The catalyst shows similar activity even after twelve regenerations deactivations. The process is expected to operate in swing mode of operation with multiple fixed bed reactors. We claim: 1. A process for converting the C5-C6 paraffins rich light naphtha cut into aromatics and liquefied petroleum gas which comprises: i) incipient wetness impregnation of Group III A metal preferably gallium with 0.5 to 8% by weight to dried HZSM-5 zeolite extrudate, ii) further impregnation of Group VIII B metal preferably platinum with 0.01 to 2 wt% to the above said dried gallium containing HZSM-5 extrudates, iii)loading the above said platinum promoted gallium supported HZSM-5 catalyst in high pressure bench scale reactor (14 g catalyst capacity) and reducing it by passing hydrogen for a period of 2-5 hours at a temperature of 400-550°C at a flow rate of 14-20 1/h in to the reactor, iv)cooling the above said platinum, gallium containing zeolite bed to a temperature of 300°C under nitrogen atmosphere and increasing thereafter further bed temperature to 300-600°C, v)contacting light naphtha as feed stock containing hydrocarbon having carbon atoms in the range of C5-C6 with the catalyst bed in reactor at a weight hourly space velocity ranging from of 0.5 to 8 hrs"1 at a pressure in the range of 1 to 20 kg/Cm2 for 24 hours in the absence of nitrogen gas, vi) separating BTX rich C5+ liquid and LPG and other products of the resultant reaction mixture from the reactor by known methods, vii)carrying out in-situ regeneration of catalyst in reactor by oxidative combustion for 14 hrs, which is carried out in two steps, wherein the first step of regeneration is carried out at a temperature in the range of 375-400°C in the presence of oxygen in the range of 0.2 to 1.5 vol% and the second step of regeneration is carried out at a temperature in the range of 450-525°C in the presence of oxygen in the range of 1.5 to 3 vol%. 2. A process as claimed in claim 1, wherein the feedstock used is light naphtha cut containing non-cyclic C5 to C6 range paraffins. 3. A process as claimed in claims 1 to 2, wherein weight hourly space velocity is preferably in the range of 1 to 3 hr-1. 4. A process as claimed in claims 1 to 3, wherein the reactor temperature is preferably in the range of 460-480°C. 5. A process as claimed in claims 1 to 4, wherein reactor pressure is preferably in the range of 2-5 kg/Cm2. 6. A process as claimed in claims 1 to 5, wherein the process conditions viz space velocity can be varied in order to increase the aromatic content and decrease the LPG in product mixture advantageously. 7. A process as claimed in claims 1 to 6, wherein the catalyst system contains platinum promoted gallium supported ZSM-5 zeolite composite used is such as prepared by incipient wetness impregnation method. 8. A process as claimed in claims 1 to 7, wherein the catalyst used is prepared from the Group III A metals preferably gallium with 1.5 to 3wt% to dried HZSM-5 zeolite extrudate. 9. A process as claimed in claims 1 to 8, wherein the catalyst used is prepared from the Group VIII B metal preferably platinum with 0.05 to 0.3-wt% to dried gallium supported HZSM-5 zeolite extrudate. 10. A process as claimed in claims 1 to 9, wherein the gallium containing HZSM-5 catalyst promoted by group VIII B metal is incorporated into matrix material includes synthetic or natural occurring substances such as clay, silica, alumina. 11 .A process for converting the C5-C6 paraffin rich light naphtha to aromatics and liquefied petroleum gas substantially as herein described with reference to the examples accompanying this specification.

Documents:

779-DEL-2005-Abstract-(20-07-2011).pdf

779-del-2005-abstract.pdf

779-DEL-2005-Claims-(20-07-2011).pdf

779-del-2005-claims.pdf

779-DEL-2005-Correspondence Others-(20-07-2011).pdf

779-del-2005-correspondence-others.pdf

779-del-2005-description (complete).pdf

779-del-2005-form-1.pdf

779-del-2005-form-18.pdf

779-del-2005-form-2.pdf

779-DEL-2005-Form-3-(20-07-2011).pdf

779-del-2005-form-3.pdf

779-del-2005-form-5.pdf