Title of Invention

PROCESS FOR THE PREPARATION OF LINEAR LOW MOELCULAR WEIGHT ALPHA OLEFINS BY THE OLIGOMERIZATION OF ETHYLENE

Abstract

A process for the preparation of low molecular weight linear alpha olefins having 4 to 26 carbon atoms, said process comprising oligomerising ethylene in an inert aliphatic or aromatic solvent of the kind such as herein described in the presence of a catalyst comprising of a first component which is a zirconium component selected from the group consisting of zirconium alkoxide and zirconium aryloxide prepared in association with free alcohol in a ratio of 1:0.33 to 1:2.3 and a second component which is an alkyl aluminum and/or alkyl aluminum halide component, said catalyst having the formula Zr(OR)4-Et3Al/Et3Al2Cl3 wherein R is alkyl or aryl wherein the process is carried out under a continuous supply of ethylene and agitation.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 OF 1970 ) COMPLETE SPECIFICATION (Section 10, rule 13) "PROCESS FOR THE PREPARATION OF LINEAR LOW MOELCULAR WEIGHT ALPHA OLEFINS BY THE OLIGOMERIZATION OF ETHYLENE" We, INDIAN PETROCHEMICALS CORPORATION LIMITED, a Government of India Company, incorporated under the Companies Act, 1956, of P. O. Petrochemicals, District Vadodara 391 346, Gujarat, India The following speeification particularly describes and ascertains the nature of the invention and the manner in which it is to be performed: 75/mum/2001 23-1-2001 23 JAN 2001 PROCESS FOR THE PREPARATION OF LINEAR LOW MOELCULAR WEIGHT ALPHA/ OLEFINS BY THE OLIGOMERIZATION OF ETHYLENE Field of the invention The present invention relates to a process for the preparation of linear low molecular weight alpha olefins by the oligomerization of ethylene. More particularly, the present invention relates to a process for the oligomerization of ethylene to obtain low molecular weight alpha olefins, such as C4 to C24, preferably, C4 to C18 alpha olefins, using an improved catalyst system comprising of a zirconium alkoxide, alkylaluminum halide/alkylaluminums. Background of the invention Low molecular weight alpha olefins can be synthesised by polymerisation of ethylene. It is known in the art that this process produces even carbon numbered olefins having 4 to 50 carbon atoms and terminal double bonds. In some cases branched olefins are also produced. Present commercial processes for making C4 to C20 linear alpha olefins are based on Ziegler high pressure growth reaction on aluminum triethyl (Ethyl process, US patent 3906053, 1975) followed by low pressure displacement or non-Ziegler route. The Gulf process uses a one step catalytic reaction, wherein chain growth and elimination occur simultaneously in the same reactor (DE 1443927, 1961). In the non-Ziegler route, organo-nickel complexes in combination with a modifier is employed for SHOP process (US Patents 3676523, 1972; 3726938, 1973; 3825615, 1974; European Patent 177999, 1986). ZrCl4 - ETAI2CI3 - Thiophene catalyst has been employed in the Idemitsu process (European Patent 241956, 1987; Japanese Patent 6259225, 1987). The use of Ti(OR)4 (R = Cresyl) - EtAl2Cl3 - PPh3 to obtain better control over distribution of alpha olefins is described in Indian Patent 182153 (1999) and in European Patent 0722922 (1999). The Exxon process (US Patents 4409414, 1983 and 4486615, 1984) has shown that at least 90 mole % linear alpha olefins having average molecular weight ranging from 70 to 700 can be obtained from oligomerising ethylene in the presence of AlEt2Cl-AlEtCl2-TiCl4-t-BuOH and AlEt2Cl-AlEtCl2-ZrCl4-n-BuOH catalyst systems. UOP has a process for oligomerization of ethylene, using nickel based catalyst in sulfolane solvent (US Patent 4689437, 1987). The purity and distribution of alpha olefins are increased by adding 1 to 6 wt % water as an additive. Objects of the invention The primary object of the invention is to provide a process for producing linear alpha olefins of low molecular weight form ethylene. Another object of the invention is to provide an eco-friendly process for the preparation of low molecular weight linear alpha olefins by ethylene oligomerization. It is yet another object of the invention to provide a process for preparing linear low molecular weight alpha olefins from ethylene using a catalyst system which has a lower deactivation rate. Summary of the invention The present invention provides a process for the preparation of linear low molecular weight alpha olefins from ethylene in the presence of an inert and t. ecofriendly solvent using an multicomponent catalyst. Accordingly, the present invention provides a process for the preparation of low molecular weight linear alpha olefins having 4 to 26 carbon atoms, said process comprising oligomerising ethylene in an inert aliphatic or aromatic solvent in the presence of a catalyst comprising zirconium component selected from the group consisting of zirconium alkoxide and zirconium aryloxide, and an alkyl aluminum and/or alkyl aluminum halide component. In one embodiment of the invention, the process is carried out under a continuous supply of ethylene and agitation. In another embodiment of the invention, the process is performed in semi-continuous mode with ethylene being fed continuously during each period of the process. In another embodiment of the invention, the catalyst system comprises of at least two components, the first component comprising of zirconium (IV) alkoxide/carboxy late and the second component comprising triethylaluminum/ethylaluminum sesquichloride. In a further embodiment of the invention, the catalyst if of the formula Zr(OR)4-Et3Al/Et3Al2Cl3 wherein R is alkyl or aryl. In a further embodiment of the invention, Et3Al/Et3AhCl3 is reacted with Zr(OR)4in the mole ratio of 10:1 to 60:1. In another embodiment of the invention, the ratio of zirccinium alkoxide to the_ free alcohol in the system is in the range of 1:0.33 to 1:2:3. In a further embodiment of the invention, when Et3Al and Et3Al2Cl3 are used, the EtaAl diluted in solvent is initially charged into the reactor and then Et3Al2 Cl3 and other catalyst components are added therein. In another embodiment of the invention, the ethylene pressure is in the range of 18 to 38 kg/cm2. In another embodiment of the invention the temperature of the reaction is in the range of 80°C to 140°C. In yet another embodiment of the invention, the process is carried out for a time period in the range of 1 hour to 3 hours. In yet another embodiment of the invention, the solvent used is selected from cyclohexane and toluene. In yet another embodiment of the invention, the reaction is carried out at an agitator speed of 300 to 1000 rpm. In another embodiment of the invention, the zirconium component is selected from the group consisting of zirconium tetra cresylate, zirconium tetra dimethyl phenolate, zirconium tetra n-butoxide, zirconium tetra iso-propoxide, zirconium tetra n-propoxide, zirconium tetra butyrate and zirconium tetra isobutyrate. Detailed description of the invention The zirconium (IV) component of the catalyst is represented by the formula Zr(OR)4 wherein R is alkyl or aryl. Zirconium (IV) butoxide and zirconium (IV) isopropoxides are preferred. The amount of free alcohol present in the Zr(OR)4 is critical. Zirconium (IV) carboxylate includes zirconium (IV) octoate. However, a non-limiting list of Zr(OR)4 includes zirconium (IV) cresylate, zirconium (IV) 2,6 - dimethyl phenoxide and the like. The preferred second catalyst component is ethylaluminum sesquichloride or a mixture of triethylaluminum and ethylaluminum sesquichloride system. The molar ratios of the components of the catalyst used in the invention has a bearing on the production of linear oligomers. It is observed that for the catalyst system used herein, the ratio of Zr(0R)4 to ethylaluminum sesquichloride or triethylaluminum/ethylaluminum sesquichloride is between 1:10 to 1:60. The ratio of Zr(OR)4 to free alcohol present in the system is also critical and is ideally between 1:0.33 to l:1.3/in the absence of free alcohol, Zr(0R)4 has a tendency to oligomerize itself to give an inorganic oligomer which has no activity for the present invention. The oligomerization is preferably carried out at a temperature in the range of 65 - 180°C, the most preferred range being 80 - 140°C. While the conversion of ethylene is low at a reaction temperature below 80°, elevation in temperature leads to lower productivity of the catalyst. The reaction is preferably carried out at a time range of 1 hour to 3 hours, and the preferred agitator speed is in the range of 300 to 1000 rpm, more preferably 500 to 750 rpm. The active catalyst used in the invention is made by mixing Zr(OR)4 and ethylaluminum sesquichloride. Preferably, the sequence of mixing is by initially adding triethylaluminum and solvent into the reactor followed by Zr(OR)4 and ethylaluminum sesquichloride in that order. The oligomeric products made by the present invention comprise of C4 to C24 alpha olefins. The oligomerization product is isolated using a catalyst quenching procedure comprising adding aqueous alkali or sodium bicarbonate solution followed by water wash and final recovery by distillation. , ^ The process of the present invention is described further hereinbelow with reference to the following examples, which are merely illustrative and should not be construed as limiting the scope of the invention. EXAMPLE 1 A 600 ml stainless steel reactor activated with high purity N2 for atleast lh at 140°C was cooled to 40°C and charged with 0.5 mmole Zr(0-C6H3(CH3)2)4, 150 ml cyclohexane and 5 mmole of Et3Al2Cl3. The vessel was heated to 90°C. Ethylene was continuously fed at 21 kg/cm2 for a period of lh. The temperature rose from 90°C to 110°C during the first 5 minutes. The reaction was carried out at 300 rpm. After lh the vessel was cooled and the contents quenched with 3ml of n-butanol. The gas and liquid products were then collected and analyzed by gas chromatograph. The product (19.8 gm) consisted of C4 to C20+ olefins and the ethylene conversion was 70.6% (wt). The selectivity of linear olefins was I-C4 = 27.7, 1-C6 to 1-Cio = 31.2, I-C12 to 1-Ci8 = 26.6 and I.-C20+ = 14.3. The yield of catalyst is 413 g AO/g.Zr. Table 1 shows the results obtained when Zr(OC6H4CH3)4 is employed as the catalyst. EXAMPLE 2 A dry 600 ml stainless steel vessel was initially charged with 1.5 mmole of Et3Al in 100 ml cyclohexane. It was stirred for about 10 minutes. Then 4.5 mmole Et3Al2Cl3 and 0.16 mmole Zr(OBu)4. BuOH in 200 ml cyclohexane were added. The autqckvgjyas heated to 100°C. Ethylene was continuously fed at 33 kg/cm2 for a period of 3h. The temperature rose from 100°C to 125°C during the first 5 min. The reaction was carried out at 300 rpm. About 103.8 gm of alpha olefins was obtained at an ethylene conversion of 86.2%. The selectivity of linear olefins was 1-C4 = 40.7, 1-C6 to 1-C10 = 52.7, I-C12 to \-Cn = 6.3 and I-C20+ = 0.3. The yield of catalyst is 7206 g AO/g.Zr. EXAMPLE 3 The procedure of example 2 was followed. In 600 ml vessel were added 0.75 mmole Et3Al, 2.25 mmole Et3Al2Cl3, 0.11 mmole Zr(OBu)4.BuOH and 150 ml cyclohexane. With stirrer speed 300 rpm ethylene was fed at 31 kg/cm2 for 3h continuously. About 53.6 gm of linear alpha olefins were obtained at an ethylene conversion of 88.6%. The selectivity to linear olefins was I-C4 = 43, 1-C6 tol-C10=47.5, l-C12 to 1-C18=8.7 and 1-C20+= 0.7. The yield of catalyst is 5150 g AO/g.Zr. EXAMPLE 4 The procedure of example 1 was followed. In 600 ml reactor were added 5 mmole Et3Al2Cl3, 0.38 mmole Zr(OBu)4.BuOH and 300 ml cyclohexane. The reactor was maintained at 140°C while ethylene was fed at 26 kg/cm2 for a period of 3h. About 118.7 gms of linear alpha olefins was obtained at an ethylene conversion of 95.7%. The selectivity of linear olefins was 1-C4=30.9, 1-C6 to 1-C10=49.9, l-C12to C18=16.4 and 1-C20+ = 2.8. The yield of catalyst is 3430 g AO/g.Zr. EXAMPLE 5 The procedure of example 2 was followed. In 600 ml reactor were added 1.62 mmole Et3Al, 4.85mmole Et3Al2Cl3, 0.175 mmole Zr(OBu)4.0.33BuOH and 200 ml cyclohexane. The reactor was maintained at 125°C while ethylene was fed at 34 kg/cm2 for a period of 3h. The reaction was carried out at 500 rpm. About 165.1 gm of linear olefins was obtained at an ethylene conversion of 94.9%. The selectivity to various olefins were 1-C4= 37.7, 1-C6tol-C10=54.9, l-C12tol-C18=7 and 1-C20+ = 0.3. The yield of catalyst is 10319 g AO/g.Zr. EXAMPLE 6 The procedure of example 2 was followed. In 600 ml reactor were added 0.75 mmole Et3Al, 2.25 mmole Et3Al2Cl3, 0.12 mmole Zr(OBu)4.BuOH and 200 ml cyclohexane. The reactor was maintained at 125°C while ethylene was fed at 32 kg/cm2 for 3h. The reaction was carried out at 750 rpm. About 115.2 gm linear olefins was obtained at an ethylene conversion of 84.7%. The selectivity to various olefins were 1-C4=33.2, 1-C6tol-Cio=56, 1-C12tol-C18=10,3 and 1-C20+ = 0.5. The yield of catalyst is 10666 g AO/g.Zr. EXAMPLE 7 The procedure of example 2 was followed. In 600 ml reactor were added 1.38 mmole. Et3Al, 4.14 mmole Et3Al2Cl3, 0.12 mmole Zr(OBu)4.1.3tert-BuOH 0.48 mmole. Thiophene and 200 ml cyclohexane. The reactor was maintained at 125°C while ethylene was fed at 34 kg/cm for a period of 3h. The reaction was carried out at 750 rpm. About 75.2 gm linear olefins was obtained at an ethylene conversion of 85.5%. The selectivity to various olefins were 1-C4 = 47.5, 1-C6 to l-C10=47.5, I-C12 tol-C18=4.9. The yield of catalyst is 6876 g AO/g.Zr. EXAMPLE 8 The procedure of example 2 was followed. In 600 ml reactor were added 1.6 mmole Et3Al, 4.8 mmole Ei3Al2Cl3 0.16 mmole Zr(OOCC3H7)4 and 200 ml of toluene. The reactor was maintained at 100°C while ethylene was fed at 36.5 kg/cm for a period of 3h. The reaction was carried out at 500 rpm. About 177.6 gm of linear olefins was obtained at an ethylene conversion of 89.7%. The selectivity to various olefins were 1-C4=36, l-C6 to 1-C10=55.7, l-C12to 1-Ci1=8 and 1-C20+ = 0.3. The yield of catalyst is 12200 g AO/g.Zr.. EXAMPLE 9 The procedure of example 2 was followed. In a 600 ml reactor were added 0.16 mmole Et3Al, 4.8 mmole Et3Al2Cl3, 0.2 mmole Zr(OOCC3H7-iso)4 and 200 ml toluene. The reactor was maintained at 100°C while ethylene was fed at 33 kg/cm2 for a period of 3h at 300 rpm agitation. About 103.4 gm linear olefins was obtained at an ethylene conversion of 80.7%. The selectivity to various olefins were 1-C4=36.2, 1-C6tol-Ci0=53, l-Ci2to 1-Ci8=10 and l-C2o+ = 0.6. The yield of catalyst is 5744 gm AO/g.Zr. EXAMPLE 10 The procedure of example 2 was followed. In a 600 ml reactor were added 1.6 mmole Et3Al, 4.78 mmole Et3Al2Cl3, 0.12 mmole Zr(OOCC7Hl5)4 and 200 ml toluene. The reactor was maintained at 100°C while ethylene was fed at 36 kg/cm2 for a period of 3h at 500 rpm agitation. About 86 gm linear olefins was obtained at an ethylene conversion of 66.1%. The selectivity to various olefins were 1-C4=40; 1-C6 tol-C10=55 and I-C12 to 1-C18=5. The yield of catalyst is 8970 gm AO/g.Zr. The catalyst system employed in the process of present invention and illustrated in examples 1 to 10 are influenced by various reaction conditions (Table 2 & 3) Table 1 Table 2 Table 3 75/MUM/2001 We claim: 1. A process for the preparation of low molecular weight linear alpha olefins having 4 to 26 carbon atoms, said process comprising oligomerising ethylene in an inert aliphatic or aromatic solvent of the kind such as herein described in the presence of a catalyst comprising of a first component which is a zirconium component selected from the group consisting of zirconium alkoxide and zirconium aryloxide prepared in association with free alcohol in a ratio of 1:0.33 to 1:2.3 and a second component which is an alkyl aluminum and/or alkyl aluminum halide component, said catalyst having the formula Zr(OR)4-Et3Al/Et3Al2Cl3 wherein R is alkyl or aryl wherein the process is carried out under a continuous supply of ethylene and agitation. 2. A process as claimed in claim 1 wherein Et3Al/Et3AbCl3 is reacted with Zr(OR)4 in the mole ratio of 10:1 to 60:1. 3. A process as claimed in claim 2 wherein when Et3Al and Et3Al2Cl3 are used, the Et3Al diluted in solvent is initially charged into the reactor and then Et3Al2Cl3 and other catalyst components are added therein. 4. A process as claimed in any preceding claim wherein the ethylene pressure is in the range of 18 to 38 kg/cm2. 5. A process as claimed in any preceding claim wherein the oligomerisation is carried out at a temperature in the range of 80°C to 140oC. 6. A process as claimed in any preceding claim wherein, the process is carried out for a time period in the range of 1 hour to 3 hours. 7. A process as claimed in any preceding claim wherein, the solvent used is selected from cyclohexane and toluene. 8. A process as claimed in any preceding claim wherein, the reaction is carried out at an agitator speed of 300 to 1000 rpm. 9. A process as claimed in any preceding claim wherein, the zirconium component is selected from the group consisting of zirconium tetra cresylate, zirconium tetra dimethyl phenolate, zirconium tetra n-butoxide, zirconium tetra iso-propoxide, zirconium tetra n-propoxide, zirconium tetra butyrate and zirconium tetra isobutyrate. 10. A process for the preparation of low molecular weight linear alpha olefins having 4 to 26 carbon atoms substantially as herein described with reference to the forgoing Examples. Dated this 9th January, 2001 H.SUBRAMANIAM Of SUBRAMANIAM, NATARAJ & ASSOCIATES ATTORNEYS FOR THE APPLICANTS

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