Trioctylaluminium

Explosiveness

Link to relevant study record(s)

Reference

Endpoint:

explosiveness

Type of information:

experimental study

Adequacy of study:

key study

Study period:

not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted in accordance with generally accepted scientific principles, possibly with incomplete reporting or methodological deficiencies, which do not affect the quality of the relevant results.

Principles of method if other than guideline:

Determination of the thermal stability and the maximum safe handling time at various temperatures of Tri-n-octylaluminum, trade name TNOAL.

The thermal stability is measured by means of Differential Scanning Calorimetry (DSC) and Setaram C80. The maximum safe handling time is the maximum safe time that a compound can be stored or handled at a certain temperature. After this time the temperature of the compound should be decreased immediately.

GLP compliance:

not specified

Key result

Parameter:

other: More sensitive to shock than m-dinitrobenzene

Remarks on result:

not measured/tested

Key result

Parameter:

other: More sensitive to friction than m-dinitrobenzene

Remarks on result:

not measured/tested

Key result

Parameter:

other: Explosive under influence of flame

Remarks on result:

not measured/tested

Key result

Parameter:

other: Explosive (not specified)

Remarks on result:

not measured/tested

The results of the isothermal experiments are presented in table 1.

Table 1: DSC & Setaram isothermal data for TNOAL

Equipment	Temperature (°C)	Intake (mg)	Max. heat production, Qmax(W/kg)
Setaram	197.8	1156.3	2.13
Setaram	222.5	1095.6	8.89
Setaram	237.4	668	19.8
DSC	250	22.06	39.7

With the combined DSC and Setaram data an Arrhenius curve is constructed as is visualized in figure 3. The activation energy (Ea) and the Ln C value can be determined with this curve. For TNOAL the ln C is 29.94 and the activation energy (Ea) is 114.32 kJ/mol.

The combination of endothermic and exothermic peak just after each other is observed also for other Metal Alkyls (like DMAL-H. DIBAL-H and TIBAL). The endothermic effect is most probably due to the first step of the decomposition mechanism of the Metal Alkyl.

Safe handling times

DSC and Setaram experiments were performed in order to determine the kinetic parameters of TNOAL. With these kinetic parameters the maximum safe handling times were calculated (see table 2). The maximum safe handling time is ¼ value of the adiabatic induction time. The adiabatic induction time (tad) is the time to maximum decomposition rate under adiabatic circumstances starting at a certain temperature level T1. Recommendations for the safe handling times of TNOAL are given in table 2. A detailed graph with safe handling times at different temperatures is presented in figure 4.

Table 2: Maximum safe handling times at various temperatures for TNOAL:

Temperature (°C)	Safe Handling Time (hours)
150	23.0
160	11.4
170	5.8
180	3.1
190	1.7
200	0.9
210	0.5
220	0.3

With ln C and Ea, the adiabatic induction times (tsaf,max) were calculated. The maximum safe handling time is derived from the adiabatic induction time:

t_saf,max = ¼ t_ad

Conclusions:

Like other Metal Alkyls, TNOAL shows a combined endothermic/exothermic effect. Due to this combination no accurate determination of the decomposition heat is possible from the scan. However during isothermal measurements a total heat production (delta Hexo) of 165 J/g is measured.

For TNOAL the ln C is 29.94 and the activation energy (Ea) is 114.32 kJ/mol, this can be derived from the Arrhenius curve.

Executive summary:

Determination of the thermal stability and the maximum safe handling time at various temperatures of Tri-n-octylaluminum, trade name TNOAL.

The thermal stability is measured by means of Differential Scanning Calorimetry (DSC) and Setaram C80. The maximum safe handling time is the maximum safe time that a compound can be stored or handled at a certain temperature. After this time the temperature of the compound should be decreased immediately.

Like other Metal Alkyls, TNOAL shows a combined endothermic/exothermic effect. Due to this combination no accurate determination of the decomposition heat is possible from the scan. However during isothermal measurements a total heat production (delta Hexo) of 165 J/g is measured.

For TNOAL the ln C is 29.94 and the activation energy (Ea) is 114.32 kJ/mol, this can be derived from the Arrhenius curve.

Description of key information

Like other Metal Alkyls, Trioctylaluminium shows a combined endothermic/exothermic effect. Due to this combination no accurate determination of the decomposition heat is possible from the scan. However during isothermal measurements a total heat production (delta Hexo) of 165 J/g is measured.