Triethylaluminum

Chemical Properties

The aluminum alkyls are highly flammable and reactive, colorless to yellow liquids at room temperature. The lighter trialkylaluminums ignite spontaneously in air. They are normally supplied and used in a 20% solution with a hydrocarbon solvent, such as hexane, heptane, benzene, toluene. Properties may depend on solvent. Reacts violently with water.

Chemical Properties

Colorless liquid. Miscible with saturated hydrocarbons.

Uses

Triethylaluminum is used as a co-catalyst in the industrial production of polyethylene and for the production of medium chain alcohols. Used as a catalyst in Ziegler-Natta polymerization process for vinyl, olefin, diene polymerizations and linear oligomerization and cyclization of unsaturated hydrocarbons. It is also used as a catalyst to produce ethylene gas, chain growth of ethylene, longer chain aluminum alkyls, and in plating aluminum.

Uses

Triethylaluminum, in combination withmany transition metal complexes, is used as Ziegler-Natta polymerization and hydrogenationcatalyst. Also, it is used as intermediatein organic syntheses.

Uses

Catalyst intermediate for polymerization of olefins, especially ethylene; pyrophoric fuels; production of α-olefins and long-chain alcohols; gas plating of aluminum.

Production Methods

In a typical example, a slurry is prepared containing 7 wt % aluminum powder (0.1 wt% zirconium catalyst content) and 45 wt% recycled triethylaluminum in a paraffin hydrocarbon fraction, boiling range 177 – 260 ℃. The slurry is pumped into the reactor at a rate of 1.5 m3/h, at a reactor temperature of 132 ℃, while hydrogen is introduced at the bottom to maintain a partial pressure of 10 MPa. Excess hydrogen is removed in flash drum, wherein pressure is decreased to 3 MPa and temperature is lowered to prevent thermal reversal of the reaction. In the ethylation reactor sufficient ethylene is added to react completely with the Al – H bonds. Temperature is held at around 85 ℃ or somewhat higher. The addition rate increases with temperature, but carboalumination of ethylene also can occur to formn-butyl groups, especially at higher temperatures. Hydrogen and ethylene partial pressure is kept low in ethylation reactor to minimize hydrogenation of ethylene to ethane and to reduce excess carboalumination products. Excess ethylene and hydrogen are removed in flash drum. A portion of the triethylaluminum product solution is recycled to reactor.

General Description

A colorless liquid. Flammable gas is produced on contact with water.

Air & Water Reactions

Pyrophoric, ignites in moist air [Merck 11th ed. 1989]. Reacts violently with water.

Reactivity Profile

Triethylaluminum reacts violently with water, alcohols, phenols, amines, carbon dioxide, sulfur oxides, nitrogen oxides, halogens, and halogenated hydrocarbons, causing fire and explosion hazards. [Handling Chemicals Safely 1980 p. 929]. A mixture of dimethylformamide and triethyl aluminum exploded when heated [Bretherick 1995].

Health Hazard

Exposure to smoke from fire causes metal-fume fever (flu-like symptoms). Since liquid ignites spontaneously, contact with eyes or skin causes severe burns.

Health Hazard

The health hazard from exposure to thiscompound is attributed to its violent reactionswith many substances, including airand water. Because of its violent reactionwith moisture, skin contact can cause a dangerousburn. Contact with eyes can damagevision.

Fire Hazard

Triethylaluminum is extremely pyrophoric, igniting spontaneously in air. It reacts violently with water, alcohol, halogenated hydrocarbons, and oxidizing substances. Among the alcohols, the lower alcohols, methanol, ethanol, n- propanol, and isopropyl alcohol, react explosively with triethylaluminum. Reactions with lower aldehydes, ketones and amides can be vigorous to violent. It may explode on contact with halocarbons in excess molar ratios or upon slight warming. When heated to 200°C (392°F), it decomposes, liberating ethylene and hydrogen.

Flammability and Explosibility

Highly flammable

Safety Profile

Extremely destructive to living tissue. A very dangerous fire hazard when exposed to heat or flame. Ignites spontaneously in air. Explodes violently in water. To fight fire, use CO2, dry sand, dry chemical. Do not use water, foam, or halogenated fire-fighting agents. Explosive reaction with alcohols (e.g., methanol, ethanol, propanol), carbon tetrachloride, N,N-dmethylformamide + heat. Incompatible with halogenated hydrocarbons; triethyl borane. When heated to decomposition it emits acrid smoke and irritating fumes. See also ALUMINUM COMPOUNDS and ORGANOMETALS.

Potential Exposure

Alkyl aluminum compounds are used as components of olefin polymerization catalysts. They are also used in the synthesis of higher primary alcohols and in pyrophoric fuels, as a catalyst in making ethylene gas; and in plating aluminum.

Shipping

ntial fire or explosion hazard. Shipping: UN3399 Organometallic substance, liquid, water-reactive, flammable, Hazard Class: 4.3; Labels: 4.3 Dangerous Dangerous when wet material, 3-Flammable liquid, technical name Required. UN3051-Spontaneously combustible. Also, this material is dangerous when wet. (Note: this number does not appear in the 49/CFR HazMat tables).

Purification Methods

Purify it by fractionation in an inert atmosphere under a vacuum in a 50cm column containing a heated nichrome spiral, taking the fraction b 112-114o/27mm. It is very sensitive to H2O and should be stored under N2. It should not contain chloride ions which can be shown by hydrolysis and testing with AgNO3. [Baker & Sisler J Am Chem Soc 75 4828 5193 1953, NMR: Brownstein et al. J Am Chem Soc 81 3826 1959, Beilstein 4 IV 4398.]

Incompatibilities

The lighter trialkylaluminums ignite spontaneously in air; can self-heat in the air at room temperature without any added energy and may ignite. These compounds are strong reducing agents. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Incompatible with water, oxygen (air), acids, alcohols, phenols, amines, carbon dioxide; sulfur oxides; halogenated compounds, and many other substances

Waste Disposal

Careful incineration