Title of Invention

CATALYTIC SYSTEM FOR ETHYLENE OLIGOMERIZATION INTO LINEAR ALPHA-OLEFINS

Abstract

A process for oligomerization of ethylene into linear alpha-olefins The present invention relates to a process for oligomerization of ethylene into linear alpha-olefins utilizing a catalystic system involving Zr compounds, aluminium compound and Lewis base, wherein Zr carboxylate is used as Zr compound, a mixture of (C2Hs)nAICI3-n, l~n~2, and al~ylalumoxanchloride is used as aluminum compound, and stable nitroxyl radical (RNO.) is used as Lewis base, with atomatic ratio Zr:AI:N=I:( 0- 1000): (0.01-1.0).

Full Text

Catalytic System for Ethylene OHgomerization into Linear alpha-Olefins MK16C08 F 10/02 C07 C2/32 The invention refers to chemistry, in particular, to complex organometallic catalytic systems (catalysts) for oligomerization of ethylene into higher linear alpha-olefins (LAO), Products of ethylene oligomerization - LAO C4-C30 are used as stock for production of domestic detergents, floating agents, emulsifiers, components of lubricant-cooling and drilling liquids, plasticizers, additives of different types, synthetic low-pouring oils, polymers and copolymers, monomers, depressors of petroleum and petroleum products, higher alkylamines, higher aluminumorganic compounds, higher alkylaromatic hydrocarbons, higher fat alcohols and carboxylic acids, olefin alpha-oxides, heat carriers, as well as for synthesis of different composites based on LAO C20-C30: niastics, hermetics, coatings. The invention can be applied in chemical and petrochemical industry, at plants for LAO production using complex organometallic catalysts. The catalyst of ethylene oligomerization into LAO C4-C30 is known, which involves zirconium tetrachloride and aluminumorganic compound (C2H5)nAlCl3_n> where n is integer or fraction in a range l Ethylene oligomerization is performed on the known catalyst in hydrocarbon solvent at 100 - 150°C and pressures of 4-8 MPa. Main disadvantages of the known catalyst are: poor ZrCl4 solubility in hydrocarbon solvents, tough conditions of the catalyst activity and its low selectivity. Together with LAO, a great amount of waxy polyethylene and up to 3.0 mas% of high molecular polyethylene form upon ethylene oligomerization with this catalyst. The improved version of this catalyst is known [3]. It involves zirconium tetrachloride, aluminumorganic compound (C2H5)nAlCl3-n and Lewis base. Esters RCOOR' where R-R1 - alkyi, aryl, aralkyl or alkaryl C1-C30 are used as Lewis bases, and mole ratio RCOOR'/ZrC^ is 2. Esters enable ZrC^ dissolving in hydrocarbon solvents. Ethylene oligomerization on this catalytic system is performed at 80-120°C and pressures of 4-8 MPa. The process is also accompanied by high molecular polyethylene formation. Main disadvantages of this catalyst are tough conditions of its activity and polymer formation. A system involving Zr salt of carboxylic acid of general formula (RCOO)mZrCl4.m and aluminumorganic compound (C2H5)nAlCl3, where m and n are integer or fraction in a range l Zr salts of carboxylic acids (RCOO)mZrCl4.m are easily soluble in hydrocarbon solvents. Ethylene oligomerization on this catalytic system is performed in toluene at 60-80°C and ethylene pressure 2-4 MPa. Concentration of Zr compound in toluene is changed in the reactor in a range of 0.5 - 1.56 mmol/1. Mole ration Al/Zr in the catalytic system is varied from 10 to 50. Ethylene and toluene should be purified and dried thoroughly before oligomerization using the known catalytic system. Introduction of water traces in the reactor together with ethylene or toluene results in alkylation of toluene and reduction of the catalyst selectivity over LAO. The main disadvantage of the known catalytic system (RCOO)mZrCl4-n + (C2H5)nAlCl3-n is formation of high molecular waxy polyethylene. Content of polyethylene in the products of ethylene.conversion depends on mole ratio of the components, on oligomerization conditions, and can vary from 0.01 to 1.5 mas% with respect to the converted ethylene. Formation of LAO and high molecular polyethylene on these catalytic systems suggests that they are bicentral ones with two similar but kinetically different active centers. LAO is formed on one of them, polyethylene - on the other. Formation of polyethylene reduces selectivity of the • catalytic system and results in complex technological design of the process. Another disadvantage of the known catalytic system is its relatively low efficiency. It results in high consumption of expensive Zr carboxylate (above 0,1. g of Zr for 1 kg of LAO). The invention was aimed for avoiding the polymer formation and decrease of specific consumption of Zr carboxylate (Zr consumption with respect to 1 kg of the resulting LAO). To achieve this purpose, we suggest the four-component catalytic system involving Zr compound, a mixture of two Al compounds and a Lewis base, for ethylene oligomerization into LAO. The system contains Zr carboxylate of the general formula (RCOO)mZrCl4-m, where R - unsaturated or aromatic hydrocarbon radical, with double or triple bond or aromatic fragment being conjugated with the COO-group, and m being integer or fraction, chosen from a range l is vinyl (CH2=CH-)» 2-propenyl (CH2=C-CH3), acetylenyl (ClfrC-), phenyl, naphthyl, cyclopentadienyl, indenyl or fluorenyl groups. A mixture of two Al compounds is presented in the catalytic system as a mixture of (C2H5)nAlCl3-n, where n is integer or fraction chosen from a range of l R-Al-(0-Al-)-x-(0-Al-)y-O-AlR II II CI R CI Ci where R is methyl, ethyl, propyl, butyl, isobutyl; and x and y are integer or fraction chosen from a range 0 can be a mixture of two or more compounds. Fraction values of n, [ and y correspond to that case. In particular, compound (C2Hs)nAlCl3.n is a mixture of (C2H5)2A1C1 and C2H5AICI2 with various ratio of the components. For alkylalumoxanchloride the situation is even more complicated. The simplest alkylalumoxanchloride corresponds to x=y=0. In this case alkylalumoxanchloride has the following structure: R-Al-O-Al-R I I Ci CI Usually x is not equal to y, and alkylalumoxanchloride is a mixture of at least two compounds. Mixtures of Al compounds with n=2 and x=y=5 are preferable. Introduction of alkylalumoxanchloride in the catalytic system provides increasing of its specific efficiency. Nitroxyl radical, i.e., 2,2,6,6-tetramethylpiperidine-l-Oxyl or ditertbutyi-nitroxyl is used as a Lewis base. If nitroxyl radical's concentration in solution is lower than that of Zr carboxylate, the former selectively reacts with active polymerization centers, thus preventing the polymer formation. If the radical concentration is higher, it reacts with active centers of ethylene oligomerization into LAO as well- This results in a decrease of activity and efficiency of the catalytic system. These factors determine the values of RNO to Zr carboxylate mole ratio: RNO»/(RCOO)mZrCl4.m=0.0t-1.0. The same characteristics determine limit and optimal atomic ratio Al/Zr. With Al/Zr1000 catalytic telomerization of ethylene by alkylaluminumchlorides to yield higher alkylaluminumorganic compounds occurs instead of ethylene oligomerization into LAO, due to a drastic increase of a rate of the chain transfer onto aluminumorganic compound. Al/Zr ratio in a range of 20-500 are preferable. The optimal results concerning activity, efficiency and selectivity of the developed catalytic system have been obtained for Zr carboxylate concentration of 0.005-0.25 g/1 (0.01-0.5 mmol/1) at 60-80°C and ethylene pressure 2 MPa. Under these conditions LAO yield is 1000 kg per 1 g of Zr in the catalytic system during 90 minutes, and Zr consumption reduces to 0.6-2.5 g with respect to 1 ton of LAO. Under these optimal conditions ethylene has not yielded. This can be due to a low speed of reducing processes which are responsible for the formation of the active polymerization centers. Specific activity and efficiency increase, similar to the case of highly efficient metallocene catalysts of olefins polymerization, is due to the presence of alkylalumoxanchloride which acts as oligomeric carrier of active centers of ethylene oligomerization. Increase of total concentration of aluminumorganic compounds in solution is also favorable for increase of specific activity and efficiency. The developed catalytic system excludes by-side processes of toluene alkylation, LAO isomerization, ethylene cationic dimerization, LAO oligomerization and co-oligomerization. This is due to the absence of strong Lewis bases in the catalytic system. Its selectivity in optimal conditions is above 98%. Ethylene oligomerization products are a mixture of olefins homo logs C4-C30 with even number of carbon atoms in the molecule. Varying of the catalytic system composition allows parameters of molar-mass distribution and fraction composition of the products to be controlled in a wide range. Ethylene to LAO oligomerization is performed in thermostated reactor of stainless steel 1X18H9T with intense stirring of the reaction mass with shielded electric motor and rotary type stirrer (about 1500 rotations/minute). Before the experiments, the cleaned reactor is desiccated at 80°C in vacuum (10*3 mm), and then is filled and blown with ethylene. Ethylene and the solvent is thoroughly purified and desiccated. The components of the catalytic system are dissolved in the hydrocarbon solvent separately using special glass calibrating vessels, and are united in the reactor of oligomerization. First, the solvent is loaded into the cooled reactor in the ethylene media, the desired temperature is fixed using thermostat, ethylene is introduced into the reactor while the solvent is stirred, to achieve the desired pressure, and then solutions of two aluminumorganic compounds, a mixture of Zr carboxylate and nitroxyl radical solutions are consecutively iniectprf intn fhp rpr^rfnr wifh a c-vrino^ksf^hpr A moment of Zr carboxylate solution injection in the reactor is considered the beginning of oligomerization. Oligomerization is performed under constant pressure, this being provided by continuous delivery of ethylene into the reactor while it is consumed in oligomerization process. To terminate oligomerization, 20 ml of 5% NaOH solution is introduced with intense stirring. Then, to determine a composition of the gas phase and amount of butene-1, analysis of the gas phase is performed by chromatography, pressure is reduced to 0.1 MPa, products are unloaded from the reactor, and are studied by distillation, gas-liquid chromatography and infra-red spectroscopy. Molar-mass distribution parameters and fraction composition of the LAO are quantitatively estimated by chromatographic method using LKhM 8-MD with ionization-flame detector in a regime of temperature programming from 20 to 320°C, 1.5 m column filled with silanizated chromaton NOW (0.25-0.40 mm) with 15% apiezon L. Synthesis of Zr carboxylates and alkylalumoxanchlorides and their purification is performed by known methods. Compositions of the developed catalytic systems, conditions of their application in oligomerization, as well as their efficiency, selectivity and main characteristics of the LAO obtained are demonstrated in the following examples, but are not confined to them: Example 1 (test). 0.4 1 of toluene is loaded in the reactor, temperature is fixed to 80°C, toluene is saturated with ethylene at pressure 2.0 MPa, and then 0.14 g of zirconium isobutyrate and 0.675 g of sesquiethylaluminumchloride (Al/Zr=17.3) in 20 ml of toluene are introduced into the reactor. Duration of the process is 60 minutes. 661.8 g of LAO and 0.2 g (0.03 mas%) of polyethylene yield. Average speed of oligomerization is 30.1 g/i min. LAO yield is 4.73 kg per 1 g of Zr carboxylate, which corresponds to the LAO yield of 22.3 kg per 1 g of Zr. Zr consumption is 0.045 g per 1 kg of LAO. Efficiency of the catalytic system is 17700 mole of LAO per 1 mole of Zr carboxylate. Selectivity over different olefins types, %: CH2=CH - 98; trans-CH=CH- 1.0; CH2=C - 1.0. LAO fraction composition, mas%: (C4-C8) - 45.8; (C10-C20) - 45.5; (C22-C30) - 8.7. Mn- 114.4 g/mol; Mw -159.4 g/mol; Mw/Mn=1.393. Example 2. 0.4 1 of toluene is loaded in the reactor, temperature is fixed to 80°C, toluene is saturated with ethylene at pressure 2.0 MPa, and then 0.04 g (0.1055 mmol) of zirconium acrylate (m=4) in 20 ml of toluene, 0.42 g (3.485 mmol) of diethylaluminumchloride (n=2) in 10 ml of toluene, 0.735 g (3.419 mmol) ethyialumoxanchloride with x=y=0 in 20 ml of toluene, and 1.646 mg (0.01055 mmol) of 2,2,6,6-tetramethylpiperidine-l-oxyl in 10 ml of toluene are introduced in the reactor. Al/Zr=97.85; N/Zr=0.1. Duration of the process is 60 minutes. 426.4 g of LAO yield. Polyethylene does not form. Average speed of oligomerization is 15.45 g/1 min. LAO yield is 10.66 kg per 1 g of Zr carboxylate, which corresponds to the LAO yield of 44.42 kg per 1 g of Zr in catalytic system. Zr consumption is 0.022 g per 1 kg of LAO. Parameters of MMD of LAO: Mn =108 g/mol; Mw =141.5 g/mol, 7=1.31. Efficiency of the catalytic system is 37420 mole of LAO per 1 mole of Zr carboxylate. Selectivity over different olefins types, %: CH2=CH - 98.5; trans-CH=CH- 0.5; CH2=C LAO fraction composition, mas%: (C4-C3) - 52.0; (C10-C20) - 45.9; (C22-C30) r-2.1. Example 3. 0.4 1 of toluene and a catalytic system involving 0.056 g (0.1687 mmol) of dimetacrylatezirconiumchloride (m=2) in 20 ml of toluene, 0.65 g (5.25 mmol) of sesquiethylaluminumchloride (n=11.5) in 10 ml of toluene, 1.14 g (1.219 mmol) of ethylalumoxanchloride with x=y=5 (molecular mass is 935.5 g/mol) in 20 ml of toluene, and 2.07 mg (0.01327 mmol) of 2,2,6,6-tetramethylpiperidine-l-oxyl in 10 ml of toluene are loaded in the reactor. Al/Zr=1178; N/Zr=0.079. Oligomerization is performed under the same conditions as in Example 1.. Duration of the process is 60 minutes. 362.1 g of LAO yields. Polyethylene does not form. LAO yield is 6.5 kg per 1 g of Zr carboxylate, or 23.7 kg per 1 g of Zr in catalytic system. Zr consumption is 0.042 g per 1 kg of LAO. Mn =96.3 g/mol; Mw= =119.4 g/mol; 7=1.24. Efficiency of the catalytic system is 26246 mole of LAO per 1 mole of Zr carboxylate. Selectivity over different olefins types, %: CH2=CH - 97.7; trans-CH=CH- 1.0; CH2=C LAO fraction composition, mas%: (C^Cg) - 61.4; (C10-C20) " 37.8; (C22-C30) " 0.8. Examples 4-17. Ethylene oligomerization into LAO on catalytic systems involving Zr carboxylate, (C2H5)nAlCl3-n, alkylalumoxanchloride and nitroxyl radical, is performed similar to Example 2. Tables 1-3 present the catalyst components, conditions and parameters of the process in toluene medium (0.46 1) at 2.0 Mpa, as well as characteristics of the formed LAO and efficiency of catalytic systems. References 1. USA Patent 4486615. Chem.Abstr. 1985. v.103. p. 149940. 2. USA Patent 4783573 3. USA Patent 4855525 4. USSR Author certificate 1042701 dated by 19.07.1978; Application in Italy 2449879; Chem.Abstr. 1980. v.93. 72615 - prototype. We claim: 1. Catalytic system for ethylene oligomerization into linear alpha-olefins, involving Zr compounds, aluminum compound and Lewis base, wherein Zr carboxylate is used as Zr compound, a mixture of (C2H5)nAlCl3.n , l alkylalumoxanchloride is used as aluminum compound, and stable nitroxyl radical (RNO) is used as Lewis base, with atomic ratio Zr:Al:N=l:(10-1000):(0.01-1.0). 2. Catalytic system of claim 1, wherein Zr carboxylate of general formula (RCOO)mZrCl4-m, is used, with R being unsaturated or aromatic hydrocarbon radical, and double or triple bond or aromatic fragment are conjugated with COO- group, and m is integer or fraction chosen from a range of l 3. Catalytic system of claims 1-2, wherein R in Zr carboxylate is a radical chosen from a group involving vinyl (CH2=CH-), 2-propenyl (CH2=C-CH3>, acetylenyl (CHsC-), phenyl, naphthyl, cyclopentadienyl, indenyl or fluorenyl groups. 4. Catalytic system of claims 1-3, wherein it contains alkylalumoxanchloride of general formula R-Al-(0-Al-)-x-(0-Al-)y-0-AlR CI R CI CI, where R is methyl, ethyl, propyl, butyl, isobutyl, and x and y - are integer or fraction chosen from a range 0 5. Catalytic system of claims 1-4, wherein 2,2,6,6-tetramethylpiperidine-l-oxyl or ditertbutylnitroxyl are used as a nitroxyl radical. 6. Catalytic system for ethylene oligomerization into linar alpha-olefins substantially as herein described and pxemplf ied.

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