Trimethylaluminum is called TMA for short. Trimethylaluminum was prepared by Buckton for the first time using methyl mercury and aluminum in 1865, but until the 1950s, TMA applications has been still limited to the scope of laboratory, its research and application was far less active than organic magnesium and organic lithium for a long time. In recent years, with the development of the research of polyolefins, TMA is as one of the cocatalyst, and starting raw materials for synthesis of cocatalyst catalysts methylalumoxane (of MAO) and modified methylaluminoxane (MMAO) in metallocene catalyst systems. In the organic chemical industry, especially polymer chemical industry, its importance began to appear.
At normal temperature and pressure, trimethyl aluminum is a colorless transparent liquid, highly reactive, spontaneous combustion in the air, and instantly be able to fire, reacts violently with alcohol and acids which have an active hydrogen, reacts violently with water, even in cold water explosive decomposition reaction can be produced, and also generates methane, and sometimes can catch fire. At 300 ℃ it slowly decompose to produce methane. It can form stable complexes with AsH3, PH3, ethers, tertiary amines and other Lewis bases, miscible in any proportion with alicyclic hydrocarbons such as hexane and heptane, aromatic hydrocarbon such as toluene, xylene. diluted to below 25% with a hydrocarbon-based solvent, trimethyl aluminum loses its spontaneous combustion.
There is an important use for trimethyl aluminum in organic catalytic chemistry, organic synthesis and polymer chemistry industry and other aspects.
Trimethylaluminum acts with water of a suitable form, may form highly reactive methylaluminoxane (MAO), which is one of the most important co-catalyst of the metallocene catalyst system. The maximum use of MAO is to form a coordination catalyst, such as with the halide of titanium, zirconium, hafnium to form a catalyst system, which can result in stereospecific polymerization, copolymerization, oligomerization of olefins. It can form catalyst with the compound of transition metal element such as nickel, cobalt, etc, which can result in lower poly, disproportionation, isomerization of olefins. Further, trimethyl aluminum itself may be used to catalyze the reaction.
TMA can be carried out oligomerization with ethylene to produce high-carbon aluminum alkyl, after oxidation and hydrolysis of the latter to form a straight-chain higher primary alcohols and advanced a-olefins. Organoaluminum is not only inexpensive, but also has high reaction activity, thus organoaluminum is commonly used for preparing other metals organic compounds, for example the reaction of TMA with stannic chloride can be prepared to produce methyl tin. TMA can also be used as mild reducing agent for high stereoselectivity reagents, vitamins, hormones and other drug synthetic. In recent years, the formation of a metal film is achieved by application of metal organic chemical vapor deposition method. As with the hydrogen carrying TMA, the substrate is heated for thermal decomposition to form a metal thin film of aluminum.
In the aerospace industry, and trimethyl aluminum can be used as liquid fuel of rockets. TMA can also be used as an important alkylating agent in organic synthesis of fine chemical industry.
As olefin polymerization catalyst, pyrophoric fuel, also used for making straight-chain primary alcohols and olefins, etc, it can be used for metal organic chemical vapor deposition.
The above information is edited by the chemicalbook of Yan Yanyong.
Spontaneous Combustion items
Oral-rat LD50: 10000 mg/cubic meter/15 minutes
Flammability hazard characteristics
In case of air, chlorine, oxidizers, high temperature can be spontaneous, emit toxic aluminide gases.
Treasury ventilation low-temperature drying, package with nitrogen charging, and stored separately from oxidants
Dry sand, powder, mountain flour
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.
Trimethylaluminium can be used as catalyst for olefin polymerization, pyrophoric fuel, manufacture of straight-chain primary alcohols and olefins, to produce luminous trails in upper atmosphere to track rockets.
Trimethylaluminum can be used in the pretreatment of Al2O3/p-type GaSb capacitors.
Trimethyl aluminum is a highly reactivereducing and alkylating agent. It is used in aZiegler-Natta catalyst for polymerization andhydrogenation.
A colorless liquid produced by the sodium
reduction of dimethyl aluminum chloride.
It ignites spontaneously on contact with air
and reacts violently with water, acids,
halogens, alcohols, and amines. Aluminum
alkyls are used in the Ziegler process for
the manufacture of high-density polyethene.
As it is pyrophoric and reacts explosivelywith moisture, skin contact can cause a dangerousburn. Contact with eyes can causeblindness. Because of its significant volatility,the risk of inhalation of this compoundis higher than with most other alkyls. Inhalationof its vapors can severely damage therespiratory tract.
TLV-TWA: 2 mg(Al)/m3 (ACGIH).
Trimethylaluminum and related alkylaluminum reagents are pyrophoric materials that can react explosively with the moisture in tissues, causing severe burns. The heat of reaction can also ignite the methane gas generated, resulting in thermal burns. Alkylaluminum reagents are corrosive substances, and contact is extremely destructive to the eyes, skin, and mucous membranes. Inhalation of trimethylaluminum and other volatile alkylaluminum compounds may cause severe damage to the respiratory tract and can lead to fatal pulmonary edema.
Flammability and Explosibility
Trimethylaluminum is pyrophoric and burns violently on contact with air or water.
Other alkylaluminum reagents show similar behavior, although most are not as
volatile as trimethylaluminum. Water or CO2 fire extinguishers must not be used to
put out fires involving trialkylaluminum reagents. Instead, dry chemical powders
such as bicarbonate, Met-L-X?, or inert smothering agents such as sand or graphite
should be used to extinguish fires involving trialkylaluminum compounds.
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.
Safety glasses, impermeable gloves, and a fire-retardant laboratory coat
should be worn at all times when working with these compounds. Trialkylaluminum
reagents should be handled only under an inert atmosphere.
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).
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
