WO2004099218A1

WO2004099218A1 - Production of mixed sodium and potassium tetraalkylaluminate solutions

Info

Publication number: WO2004099218A1
Application number: PCT/US2004/013406
Authority: WO
Inventors: Dennis L. Deavenport
Original assignee: Akzo Nobel N.V.
Priority date: 2003-04-30
Filing date: 2004-04-29
Publication date: 2004-11-18
Also published as: WO2004099218B1

Abstract

Mixed Na [R4A1]/K[R4A1] electrolyte compositions, where R is lower alkyl, such as ethyl, are formed by the reaction of a mixture of sodium and potassium alkali metals with one or more trialkylaluminum compounds, such as trethylaluminum.

Description

PRODUCTION OF MIXED SODIUM AND POTASSIUM TETRAALKYLALUMINATE SOLUTIONS

The basis of the present invention is that alkali metals (^WM") react readily with trialkylaluminum compounds to produce alkali metal salts of the form M⁺[R₄A1]^", wherein R is a lower alkyl group, such as methyl, ethyl, propyl, isopropyl, and the like. The reaction of triethylaluminum (^WTEAL") with alkali metals, such as sodium or potassium, produces the corresponding salts, for example, Na[Et₄Al] or K[Et₄Al]. However, in both cases, the products have limited solubility in hydrocarbon solvents. By mixing sodium and potassium metals in various proportions, mixtures can be easily made which are liquid at room temperature and below. Furthermore, the mixed Na [Et₄Al] /K [Et₄Al] electrolyte has enhanced solubility in toluene and can be produced in higher concentrations thereby yielding higher current densities in the end-use application. While toluene is the exemplified solvent described herein, the invention is deemed to be particularly applicable for use with solvents that are polar in nature due to asymmetric substitution, as exemplified by such alkylated aromatic solvents as toluene, o-xylene, p- xylene, and ethylbenzene. When the reaction is conducted in toluene as the solvent, the NaK alloy floats due to its low density. Experience shows that only moderate agitation is required to disperse the NaK into small droplets that react smoothly when TEAL is added to the reaction. As TEAL is added to the NaK dispersion, the slurry becomes dark as a result of aluminum metal by-product formation, and heat is generated. External cooling is required to remove the heat of reaction. The reaction conditions can range from about 25°C to about 105°C with no obvious consequences other than different rates of reaction. The use of temperatures below 25°C may cause the reaction to stall and temperatures above about 110°C will lead to boiling of toluene. An optimum temperature range for the reaction appears to be in the range of from about 40°C to about 70°C. The use of high shear agitation, such as with a high speed disperser, will allow the reaction to run faster at any given temperature due to higher NaK surface area and due to physical dispersal of the droplets. The high-shear generated by these agitators serves to prevent fouling of the NaK surfaces with aluminum deposits thereby facilitating the rate and completeness of reaction. It is deemed possible to obtain equivalent yields (based on NaK as the limiting reagent) in low-shear conditions if longer reaction times are allowed.

By adjusting the amounts of toluene, NaK, and TEAL in the reaction, a wide variety of electrolyte compositions can be obtained in a single reaction step. Varying the sodium to potassium atomic ratio in the NaK reagent also adds flexibility to the process as compared to any of the process options based on cation exchange with KCl) . In the cation exchange process, the end product composition is more or less fixed by the equilibrium solubility of the four principal components: NaCl, KCl, Na[Et₄Al], and K[Et₄Al]. Contamination of the final product with low concentrations of chloride can also be avoided by the NaK process. The final step in the process is filtration to remove solids from the product (mostly aluminum metal) to generate a substantially colorless product. Analysis for wt% Al, wt% Na, and wt% K is sufficient for calculation of the final product composition. Adjustments to correct for composition imbalances can be done by addition of TEAL, toluene, or product with a higher concentration or different Na [Et₄Al] /K[Et₄Al] molar ratios.

The following is a generalized depiction of the reaction of the present invention: 3 NaK + 4 Et₃Al → 3 NaK[Et₄Al] + Ali (where Na = 10-35 atomic % and K = 90-65 atomic %)

The final stoichiometry of the working electrolyte is a 1:1 complex with TEAL that is soluble in toluene. Without the extra TEAL, the product does not act as an electrolyte and has limited solubility. In effect, the complete reaction is:

3 NaK + 7 Et₃Al - toluene - 3 NaK [Et₃Al] ^• [Et₃Al] + All

Toluene is the solvent and reaction temperature is in the general range of from about 40 to about 70°C The perceived advantages of this invention are the following:

• The NaK alloy is a liquid at normal temperatures (for example, 20°C) from concentrations of about 44 wt% K to about 88 wt% K. This corresponds to 33 atomic% K to 83 atomic% K. NaK is available commercially in a variety of containers and has a low viscosity; therefore, it is very convenient to handle for the process of this invention. NaK is also easy to prepare from Na and K metals. • The handling of Na metal, as required in the Na + TEAL + KCl route, is complicated by its high melting point of 97.8°C. This also necessitates running the reaction with TEAL at high temperatures to generate a liquid dispersion or to create a solid dispersion using high-shear agitation and complex operating conditions. Temperatures below the melting point of Na cause the reaction to be slow in comparison with molten Na or NaK.

• The NaK process generates the desired product composition in a single reaction in which handling of solids is eliminated. Following the reaction, settling or filtration is required to remove aluminum generated in the reaction. All other processes that produce products of this type require multiple steps of which some require specialized equipment and challenging process conditions. • When compared with all other known process routes, the quantity of solids and by-products generated in the process are substantially reduced. The resulting filtration is simplified and requires smaller filtration equipment to accomplish clarification of the product. • Time required to produce the mixed K[T] + Na [T] solution is substantially reduced from about ten to twenty hours per batch (depending on the process utilized) to less than six hours. _*

• The finished electrolyte solution produced from TEAL and NaK is inherently free from halides. Halides in the electrolyte are reported to be detrimental to the deposition process.

Example 1

Low temperature preparation of Na₀.2oKo.8o [Et₄Al] *Et₃Al in toluene:

A reaction flask equipped with a stirrer, a condenser, and a dropping funnel was assembled and placed in an oil bath to remove the heat of reaction (See Figure 1, which follows). Toluene (311.80 g, 3.385 moles) was charged to the flask at room temperature and a total of 37.23 g of NaK alloy (20.1 mole% Na, 4.77 g = 0.208 g atom and 79.9 mole% K, 32.46 g = 0.830 g atom; fp = 12°C) was added. Agitation was adjusted to 300 rpm, and the liquid NaK was observed to disperse into small droplets . Neat triethylaluminum (Et₃Al : 285.55 g, 2.50 moles) was added over a time period of one hour and thirty-seven minutes at a reaction temperature ranging from 19-28°C. The Et₃Al addition was accompanied by formation of a black precipitate (aluminum metal) and the generation of heat. At the point where all of the NaK was consumed, the exotherm subsided and the Et₃Al addition rate was increased. Black solids that formed during the reaction were observed to settle rapidly. The black reaction slurry was transferred to a fritted glass filter funnel. The solids on the filter were rinsed with toluene and isopentane. Drying and collecting the solids gave a total of 9.48 g of black aluminum solids, which was in near quantitative agreement with the theoretical amount of 9.33 g aluminum generated in the reduction reaction. Recovery of the product in toluene solution was nearly quantitative.

Example 2 Preparation of Nao.₂₅ o.75 [Et₄Al] *Et₃Al in toluene:

A reaction flask equipped with a stirrer, a condenser, and a dropping funnel was assembled and placed in an oil bath to remove the heat of reaction. Toluene (297.15 g, 3.226 moles) was charged to the flask at room temperature and a total of 36.38 g of NaK alloy (25 mole% Na: 5.95 g = 0.259 g atom and 75 mole% K, 30.41 g = 0.778 g atom) was added. Agitation was adjusted to 200 rpm, and the liquid NaK was observed to disperse into small droplets. Neat triethylaluminum (Et₃Al: 274.57 g, 2.405 moles) was added over a time period of one hour and twelve minutes at a reaction temperature ranging from 25-45°C. The Et₃Al addition was accompanied by formation of a black precipitate (aluminum metal) and generation of heat. At the point where all of the NaK was consumed, the exotherm subsided, and the TEAL addition rate was increased. Black solids formed during the reaction were observed to settle rapidly. The black reaction slurry was transferred to a fritted glass filter funnel. The solids on the filter were rinsed with toluene and isopentane. Drying and collecting the solids gave a total of 9.23 g of black aluminum solids, which was in near quantitative agreement with the theoretical amount of 9.33 g aluminum generated in the reduction reaction. After filtration, the liquid product recovered was 547.21 g (91.4 %) compared with a theoretical weight of 598.9 g. Losses were due to solution adhering to the aluminum solids that were rinsed off separately and not accounted for in the total recovered yield. Analysis of the toluene solution showed 9.25 wt% Al (9.57 wt%, theory). By stoichiometry, the final composition of the electrolyte was 0.99 Et₃Al to Na₀.₂K₀.8 [Et₄Al] . The conductivity of the toluene solution of Na₀.2Ko.s [Et₄Al] *Et₃Al was determined to be 15.23 mS/cm at 95°C.

Example 3 Preparation of Nao.15 o.e5 [Et₄Al]«Et₃Al in toluene:

A reaction flask equipped with a stirrer, a condenser, and a dropping funnel was assembled and placed in an oil bath to remove the heat of reaction. Toluene (318.34 g, 3.455 moles) was charged to the flask at room temperature, and a total of 36.90 g of NaK alloy (15 mole% Na: 3.47 g = 0.151 g atom and 85 mole% K, 33.43 g = 0.855 g atom) was added. Agitation was adjusted to 500 rpm, and the liquid NaK was observed to disperse into small droplets. Neat triethylaluminu (Et₃Al: 292.07 g, 2.509 moles) was added over a time period of one hour and fifty-one minutes at a reaction temperature ranging from 26-63°C. The Et₃Al addition was accompanied by the formation of a black precipitate (aluminum metal) and the generation of heat. At the point where all of the NaK was consumed, the exotherm subsided, and the TEAL addition rate was increased. The reaction was allowed to cool to room temperature over fifty minutes after which the black reaction slurry was transferred to a fritted glass filter funnel. The solids on the filter were rinsed with toluene and isopentane. Drying and collecting the solids gave a total of 9.14 g of black aluminum solids, which was in near quantitative agreement with the theoretical amount of 9.05 g aluminum generated in the reduction reaction. After filtration, the liquid product recovered was 552.9 g (86.7 %) compared with a theoretical solution weight of 638.17 g. Losses were again due to solution adhering to the aluminum solids that were rinsed off separately and not accounted for in the total recovered yield. In practice, quantitative recovery of the electrolyte can be achieved by washing the solids with toluene and combining the rinsate with the initial filtrate. Analysis of the toluene solution showed 9.26 wt% Al (vs. 9.09 wt%, theory). By analysis, the final stoichiometric composition of the electrolyte was 1.134 Et₃Al to Na₀.₂K₀.8 [Et₄Al] vs. a theoretical ratio of 1.141.

Example 4 Pilot Plant demonstration campaign (five batches) (Summary of results in Table 1)

The process was run in an 89 gallon stainless steel reaction vessel with a working capacity of approximately 70 gallons. The unit was fully instrumented for continuously monitoring and the recording of temperatures, pressures, and feed rates during the process. The vessel was equipped with a variable speed agitator. Internal coils and an external jacket were available for heating and cooling. All runs were conducted under inert nitrogen atmosphere. The feed vessel for liquid NaK was a small stainless steel cylinder that was placed on a scale to obtain accurate weights during transfer of material to the reactor. Toluene was fed from a cylinder and the weight was obtained by scale. Neat triethylaluminum was also fed from a steel cylinder using a mass flow controller to monitor the rate of addition. The final weight of triethylaluminum delivered to the reactor was determined by scale.

Example from Run 1: Toluene (216.0 lbs, 2.35 moles) was charged to the reaction vessel at ambient temperature and a total of 26.8 lbs of liquid NaK alloy was added (20.1 mole% Na: 3.45 lbs = 0.150 lb moles and 79.9 mole% K, 23.30 lbs = 0.596 lb moles) . Agitation was established at 120 rpm to disperse the NaK. The temperature in the vessel was adjusted to 37 °C and neat triethylaluminum (Et₃Al at 23.18 wt% Al; 213.0 lbs, 1.90 lb moles) was added over a time period of one hour and eight minutes at a reaction temperature ranging from 37-93°C. The exotherm generated by the reaction between NaK and Et₃Al was controlled by external cooling. At the point where all of the NaK was consumed, the exotherm subsided and the Et₃Al addition was continued until all of the material was charged. The reaction was held at 90-95°C for two hours to complete the reaction. After the reaction mass was brought back to ambient temperature, the black product (455.8 lbs, 98.6% recovery) was transferred to a cylinder for settling. After all five runs had been transferred to the settling cylinder, the slurry was allowed to settle for several days. Careful decanting yielded 1,912.5 lbs of a clear, colorless product for a total recovery of finished product at 84.9% of theory. Losses were due to product remaining in the cylinder after decantation. No attempt was made to maximize recovery by filtration and washing of the solids. Analysis of the toluene solution showed 9.48 wt% Al (9.52 wt%, theory), 0.78 wt% Na (0.78 wt% theory), and 5.22 wt% K (5.26 wt% theory). The conductivity of a composite of all five runs of the electrolyte solution was determined to be 12.43 mS/cm at 95°C.

TABLE 1

TABLE 2

Target Specifications for Na₀.2 ₀.8 [Et₄Al] *Et₃Al in Toluene

Solvent

0.8 mole KalEt₄ + 0.2 NaAlEt₄ + 1 mole Et₃Al + 3.3 mole Toluene

Claims

What is Claimed:

1. A process comprising the reaction of a mixture of sodium and potassium alkali metals (collectively ^WM") with one or more trialkylaluminum compounds to produce alkali metal salts of the form M⁺[R₄A1]^", wherein R is lower alkyl.

2. A process as Claimed in Claim 1 wherein the trialkylaluminum compound is triethylaluminum.

3. A process as claimed in Claim 1 wherein the reaction is conducted in an alkylated aromatic hydrocarbon solvent.

4. A process as claimed in Claim 1 wherein the reaction is conducted in the temperature range of from about 25°C to about 105°C.

5. A process as Claimed in Claim 1 wherein the trialkylaluminum compound is triethylaluminum and the reaction is conducted in an alkylated aromatic hydrocarbon solvent .

6. A process as claimed in Claim 6 wherein the reaction is conducted in toluene in the temperature range of from about 40°C to about 70°C.

7. A mixed Na[R₄Al] /K[R₄A1] electrolyte composition, where R is lower alkyl.

8. A mixed Na [Et₄Al] /K [Et₄Al] electrolyte composition.