GB2113666A

GB2113666A - Basic aluminium compounds

Info

Publication number: GB2113666A
Application number: GB08301580A
Authority: GB
Inventors: Rex James Field; John David Wharne
Original assignee: Laporte Industries Ltd
Current assignee: Evonik LIL Ltd
Priority date: 1982-01-23
Filing date: 1983-01-20
Publication date: 1983-08-10
Also published as: GB2113666B; GB8301580D0

Abstract

Aqueous solutions of basic aluminium compounds such as basic aluminium chloride can be obtained by a reaction at elevated temperature between aluminium metal and an acid or a non-basic salt in an aqueous reaction medium in the presence of an accelerator selected from aldoses and ketoses and their corresponding carboxylic acid and hydroxyl derivatives. Particularly suitable accelerators are glucose, fructose and galactose, which can be provided as such or as bi- or polysaccharides hydrolysable to them, such as maltose, sucrose or starch, ascorbic acid and sorbitol.

Description

SPECIFICATION Basic aluminium compounds The present invention relates to basic aluminium compounds, and in particular to the process for the production of basic aluminium compounds and to the use of compounds so produced in the treatment of aqueous media.

Herein, the term "basic" when used in respect of aluminium compounds indicates that such compounds containhydroxyl groups in addition to acidic groups and by way of example where the acid group is chloride, basic aluminium chlorides can be represented by the general formula Al(OH)m(Cl)n, wherein m + n = 3. The basicity of the compound, expressed as a percentage, is given by the formula 100m/3. It will be recognised that similar formulae can be written for compounds in which one or more different acid groups are employed. The term "non-basic" is employed herein in respect of corresponding compounds that are hydroxyl-free.

Solutions of basic aluminium compounds have been produced, hitherto, by reaction between aluminium metal and either the acid itself or the normal aluminium salt of that acid under aqueous conditions and normally at temperatures at or approaching the boiling point of the aqueous phase. Even though such processes are employed commercially, it is a disadvantage of them that long reaction periods are required, especially when it is desired to produce solutions of the basic aluminium compounds at high concentrations, for example a concentration in excess of 20% by weight, calculated as Awl203. It is a further disadvantage that the resultant solution of basic aluminium compound so produced can be turbid in appearance, in that such solutions have diminished customer appeal.

According to the present invention, there is provided a process for the production of basic aluminium compounds comprising the step of reacting aluminium metal with an acid or with a non-basic aluminium salt of an acid at elevated temperature in an aqueous medium in the presence of an effective amount of an accelerator selected from aldoses and ketoses and their corresponding carboxylic acid and hydroxyl derivatives thereof until at least some basic aluminium compound has formed. By effecting the production in the presence of the effective amount aldose or ketose or corresponding derivative, the reaction is accelerated, whilst employing conditions that are otherwise identical, and the resultant solution is likely to have, in many cases, a clearer and less turbid appearance.

It will be recognised that aldoses and ketoses are monosaccharides, which can be formed in situ by hydrolysis of di- or poly-saccharides. The present invention relates not only to the use of ketoses and aldoses introduced as such into the reaction medium, but also relates to their use when introduced in the form of diand poly-saccharides hydrolysable to them. In particularly convenient embodiments of the present invention, the monosaccharide is a pentose or hexose. Examples of widely available hexoses include glucose, fructose, and galactose, and it will be recognised that these can be provided as such or in the form of di or poly saccharides that are hydrolysable to them. Thus, for example, glucose can be provided as such or in the form of maltose or starch or in mixture with fructose from sucrose, or in mixture with galactose from lactose.Further sources of glucose are the intermediate hydrolysis products from starch, including amylose, amylopectin and dextrin. Amongst pentoses of practical importance there is included xylose.

It will be understood that in the corresponding hydroxyl derivative otherwise called a glykitol, the carbonyl group in the aldose or ketose has been reduced to a hydroxyi group. Desirably, the glykitol contains 5 or 6 carbon atoms, of which readily available examples include mannitol, and preferably sorbitol.

The term "corresponding carboxylic acid derivative thereof", when used in respect of aldoses and ketoses refers not only to the polyhydroxy carboxylic acid in acid form, alternatively called a glyconic acid but also in condensed lactone form. As is also the case for aldoses and ketoses, the compounds preferably contain 5 and 6 carbon atoms, each of which is substituted by an hydroxyl or carboxylic acid group compound or lactonised, one effective and readily available example being ascorbic acid.

In practice, the concentration of accelerator is normally not more than 5 % by weight. The preferred amount of accelerator to use depends upon whether it is a glykitol or the aldose/ketose/acid derivative.

Preferably, the concentration of aldose or ketose or corresponding carboxylic acid employed is at least 0.001 /O, based on the weight of the reaction mixture, and desirably at least 0.005 %. Substantial and significant acceleration of the reaction has been obtained employing concentrations in the range of from 0.01 to 0.5 % by weight, and in practice a concentration in the range of 0.02 to 0.2 is often used. It will be recognised, however, that the degree of acceleration varies to some extent from accelerator to accelerator, it therefore being desirable and convenient to employ a highly active hexose such as galactose.For glykitols it is desirable to use at least 0.05 %, and advantageous to use at least 0.2 %, on the same weight basis, the amount generally being selected from the range of 0.4 % to 4 % by weight. Use of larger amounts of accelerator tend to promote gel formation in the resultant solution. With the exception of the shortened time taken to complete the reaction, the conditions for effecting the process of the present invention can be identical to those employed heretofore for the production of basic aluminium compounds by action between aluminium metal and the mineral acid or the non-basic aluminium salt of that mineral acid.Thus, the process is particularly suitable for the production of basic aluminium chlorides, basic aluminium nitrates and derivatives of other monobasic acids or mixtures of monobasic acids. An important feature appears to be in the use of at least part of the aluminium in the form of metal instead of alumina hydrate. The aluminium metal is employed preferably in the form of turnings or fine powder or in other forms which present a high surface area to weight ratio. In practice, the aluminium metal employed is often at least 95% pure. It will be understood that the physical form and purity of the aluminium metal can affect the absolute rate of the reaction, but the addition of the accelerators described herein in the appropriate amounts leads to an increase in the rate relative to that when the accelerator is absent.

In general, it is preferable for the reaction mixture to be maintained at a temperature of at least 80"C and more preferably at least 900C during the reaction period. One convenient temperature range to employ is that of within 5"C of the reflux temperature of the reaction mixture. After the reaction is completed to the desired extent, the mixture can be filtered and allowed or caused to cool to the ambient temperature, the cooling being effected either before or after filtration.

It is often convenient to continue the reaction by maintaining the elevated temperature until substantially no solid aluminium metal is detectable in the reaction mixture, and naturally in such circumstances the relative amounts of the aluminium, the acid or non-basic aluminium salt, and water are usually precalculated, making aliowance for any evaporation losses to produce a solution having approximately the expected basicity and concentration of the basic aluminium compound. In an alternative method of determining when to halt the reaction, the concentration of basic aluminium salt in the reaction mixture can be monitored continuously or frequently and when a predetermined concentration is reached, any unreacted aluminium metal is filtered out.

In practice, it is convenient to introduce the aqueous mineral acid such as hydrochloric acid or the non-basic aluminium salt such as aluminium chloride in an aqueous solution, gradually into a vessel containing the aluminium metal and the accelerator employed, orto add the aluminium gradually to the acidic solution. In practice, the aqueous acid or aluminium salt usually in aqueous solution is introduced over a period normally of from 30 minutes to 2 hours and during the period of its introduction, it is desirable to maintain the temperature within the aforementioned ranges, for example at 95"C.

The process of the present invention can be employed to produce most conveniently solutions having a concentration of basic aluminium compound up to about 24 %, calculated throughout the specification as A1203 by weight. Compositions having a higher concentration of product, such as 25 to 26 % as Al203 can be produced, but they have an increased tendency to gel. It is preferable to employ concentrations of aldose or hexose accelerator of not substantially more than 0.1 % by weight in conjunction with the production of solutions containing over 20% by weight basic aluminium compound, and especially between 23 and 24 % by weight as203, in order to minimise any tendency for the solution to gel.

The process of the present invention can be employed to produce not only the more concentrated solutions, by which we include those containing at least 20 % by weight of Awl203, but also solutions of somewhat lower concentrations for example in the range of 12 to 16 % by weight as A1203 which are also commercially available at present. The variation in product concentration can be achieved by variation in the ratio of total aluminium introduced into the system to total volume of solution. As a matter of practice, when calculating the ratio beforehand, allowance can be made for the water that will evaporate from the solution during the course of the reaction, or alternatively the liquid loss can be monitored and replaced as the reaction proceeds or afterwards.Thus, by way of demonstration, in order to produce a solution of basic aluminium chloride of approximately 20 % by weight, calculated as a Awl203, by a reaction between aluminium and hydrochloric acid, it is convenient to employ a weight ratio of approximately one part of aluminium per eight parts of aqueous hydrochloric acid solution of about 9.5-10 % w/w, when refluxing the mixture for about 3 hours. It will be recognised that weight ratios of aluminium to hydrochloric acid solution can be readily calculated, based on the above to achieve different concentrations of basic aluminium compound, taking into account not only the change in weight of the aluminium required, but also the change in density in the acid solution and change in reaction periods.

The basic aluminium compound can be produced by a process of the present invention with a basicity of up to 86%, in practice often from 30 to 86% and variation in basicity can be achieved by varying the mole ratio of aluminium to acid where the compound is produced directly by reaction between the acid and the aluminium metal, and by variation in the mole ratio of aluminium to aluminium salt when the latter route is followed, employing the general method and techniques known in the art for such basicity variation. In the aforementioned demonstration, the basicity of the product is about 66%. Broadly, if a higher concentration of acid is employed whilst maintaining the amount of aluminium metal introduced the same, the resultant solution will produce basic aluminium compounds having a lower basicity.Also, the effect of employing the same concentration of acid but employing a higher amount of aluminium metal is not only to increase the concentration of basic aluminium compound in the final solution measured as Awl203, but also to produce a basic aluminium compound having higher basicity.Correspondingly, in the route employing aluminium and aqueous solution of non-basic aluminium salt, increasing the weight ratio of aluminium to non-basic aluminium salt increases the basicity of the final product and employing a constant amount of aluminium metal but changing the concentration of non-basic aluminium salt not only changes the basicity of the resultant product, but also changes its concentration, calculated as Awl203. It is highly desirable to constantly agitate the reaction mixture so as to prevent the formation of localised high concentrations at the metal surface leading to the formation of gel particles and thereby produce a non-homogenous product.

Conveniently, the solutions of basic aluminium compound produced by the present invention can be subjected to further processing steps for example, the aqueous product can be dehydrated such as by spray drying to produce a solid for easy transportation. Also, it can be employed either as such or after dilution by any of the methods and for any of the uses described before for basic aluminium compound solutions produced in the absence of the accelerators described herein, and can be employed in the known manner as an antiperspirant or as a component of antiperspirant compositions, or for use in the treatment of aqueous media, such as for the purposes of water clarification, effluent treatment or sludge dewatering or for manufacture of refractory fibres or as a leather tannage.

Having described the invention in general terms, specific embodiments will now be described more fully by way of example only.

In Examples 1 to 11 and comparison 12, a solution of basic aluminium chloride was produced by a reaction between aluminium scrap in the form of small disks and hydrochloric acid. Aluminium scrap (120 g), demineralised water (540 g), and the accelerator specified in Table 1 below were placed in a 2-litre round bottomed flanged flask fitted with a nitrogen sparge, a reflux condenser and a thermometer. The mixture was heated to 95"C using an Isomantle and then concentrated hydrochloric acid (36 % by weight, 256 g) was introduced into the mixture in the flask at the constant rate of approximately 4 g per minute using a peristaltic pump, over a period of approximately 1 hour.The temperature of the reaction mixture was thereafter maintained at or near reflux temperature and the mixture was agitated by the nitrogen sparge from the moment that some of the aluminium scrap was seen to float. When it appeared, visually, that all the aluminium had dissolved, the solution was filtered through a glass fibre fiiter. The concentration of basic aluminium chloride in the filtrate was determined by the standard method described in publication Angew.

Chem. 1950 Vol. 62 p269, by O. Glemser and L. Thelen entitled (in translation) "Method for the volumetric determination of aluminium".

In Examples 13 and 14 and comparisons C15 and C16, the procedure employed in respect of Examples 1 to 11 and comparison C12 was followed, with the exception that the reaction time was standardised at 360 minutes.

TABLE 1 Example/ Accelerator Reaction Product Comparison time cone (% w/w No Compound Amount%w/w (minutes) as Al203) 1 D-Glucose 1.0 237 23.7 2 D-Fructose 1.0 265 23.2 3 Lactose 0.5 240 22.6 4 Lactose 0.1 290 23.5 5 Lactose 0.05 290 24.6 6 Lactose 0.01 415 24.1 7 Lactose 0.005 416 22.7 8 Maltose 1.0 135 23.2 9 Starch 0.1 272 24.3 10 Sucrose 0.1 235 24.3 11 Galactose 0.1 155 24.8 C12 - - 650 23.6 13 Maltose 0.1 360 24.6 14 L-ascorbic acid 0.1 360 23.8 C15 - - 360 20.8 C16 - - 360 19.2 From Table 1 it can be seen that the accelerators were responsible for shortening by at least 200 minutes, the time taken to reach the intended a concentration of approximately 23.5 %, +1-1%, in the amounts used and in many cases by about 400 minutes or more.From a comparison of examples 13 and 14 with comparisons Cl 5 and C16, it can be seen that as an alternative to achieving higher throughput, the invention can be employed to produce solutions having a higher concentration in the same reaction time. The difference between the concentrations achieved is of greater practical significance, when it is recognised that the rate of production of basic aluminium compound slows considerably as its concentration, expressed as A1203 approaches and exceeds 20 % w/w. From Table 1, moreover, it can be seen that it is possible to employ monosaccharides as in Examples 1 and 11, disaccharides as in Examples 2,3,8 and 10, and polysaccharides as in Example 9, as well as the corresponding carboxylic acid compound in Example 14.Example 13 demonstrates that it is possible to employ the disaccharide at very low concentrations and still achieve a considerable acceleration.

In Examples 17 to 21 and comparison C22 the process for making a basic aluminium chloride solution having a concentration of approximately 15% by weight compound calculated as A1203 comprised introducing aluminium scrap (450 g), demineralised water (3340 g), accelerator specified in Table 2 into a 15 litre round bottomed reactor that was equipped with a nitrogen sparge and a thermometer. The mixture was heated to 95"C using an Isomantle and concentrated hydrochloric acid (36 % by weight, 1668 g) was introduced at a substantially constant rate of approximately 17 g per minute using a peristaltic pump and a total period of addition of just below 2 hours.The temperature of the mixture was maintained at or near the boiling point of the mixture, and the mixture was agitated by the nitrogen sparge as soon as aluminium scrap was seen to float on the surface of the mixture. During the course of the subsequent reaction period, a further amount of demineralised water was introduced, judged by eye, in order to replace that which was lost by evaporation. When it appeared to the eye that all the aluminium had dissolved, the resultant solution was removed from the heat and filtered whilst still hot through glass fibre filters.

TABLE 2 Examples Accelerator Reaction Product Comparison Compound Amount time cone (% w/w No %w/w (minutes) as Al2Oa) 17 Lactose 0.1 122 13.1 18 D-Glucose 0.05 180 15.8 19 Maltose 0.05 94 16.2 20 Sucrose 0.05 120 16.6 21 Lactose 0.1 275 16.5 C22 - - 420 15.2 From a comparison of Examples 17 to 21 with the comparison C22 it will be observed that the presence of accelerator in concentrations as low as 0.05 % or 0.1 % effected a noticeable reduction in reaction time even for the production of 15 A1203 product. The concentration of the product in Example 17 resulted from an addition of an excessive amount of demineralised water and not because the aluminium had failed to react since no aluminium was retained on the filter.

In Examples 23 and comparison C24, basic aluminium chloride solutions having a concentration of about 15% by weight compound as A1203 were obtained by reaction between aluminium metal and an acidic solution of aluminium chloride. The reaction was carried out by introducing scrap aluminium (248 g), demineralised water (882 g), and the accelerator specified in Table 3 into a 15 litre round-bottomed open flask equipped with thermometer and nitrogen sparge and the mixture heated to 950C on an Isomantle.

Acidic aluminium chloride solution (2880 g 5.2 % w/w as Al203 and 3.74 % w/w excess hydrochloric acid was introduced using a peristaltic pump at a constant rate of about 35 g/min over a period of just below 1.5 hours.

As in the preceding Examples, the nitrogen sparge was started when some aluminium was seen to float and the mixture was boiled throughout the reaction period. During this period, the mixture was replenished by addition of demineralised water, the amount being judged by eye. When it appeared that all the aluminium had dissolved the solution was filtered through glass fibre filters.

TABLE 3 Example Accelerator Reaction Product Comparison Compound Amount time cone (% w/w No %w/w (mins.) A1203) 23 Sucrose 0.05 255 15.3 C24 - - 390 15.1 From Table 3 it can be seen that a marked acceleration was observed when part of the aluminium was provided in the form of aluminium chloride.

In comparison C25 and Examples 26 to 29, in which the general method of Examples 1 to 11 was followed except for using aluminium powder of 99.7 % purity and variations as seen from Table 4. In Examples 28 and 29, a glass anchor stirrer was employed to provide the agitation.

TABLE 4 - Example/ Accelerator Period Total Comparison of Acid Reaction No. Compound Amount Addition Period wiw C25 - - 205 415 26 Sorbitol 3 65 200 27 Sorbitol 1 65 205 28 Sorbitol 0.5 100 285 29 Sorbitol 0.1 100 340 The product characteristics are summarised in Table 5.

TABLE 5 Examples Rate of Appearance Concn,. Basicity Comparison Filtration (% w/w% as A12O3 C25 slow yellow-brown 24.9 84.16 and turbid C26 V. Fast clear 24.2 85 C27 V. Fast clear 24.3 85.3 C28 V. Fast clear 24.4 85.3 C29 medium turbid 25.0 85.7 From Tables 4 and 5 it can be seen that sorbitol improved the product characteristics as well as the rate of production and that the extent of improvement varied in relation to its concentration up to about 1% above which substantially the same results were obtained.

The utility of representative samples of the solutions as a sewage sludge conditioner was tested using 3 representative sewage sludges obtained from 3 different treatment works, each of which treat a mixture of domestic and industrial sewage. The sludges employed were; A- raw primary of 1.8 % solids content B - raw primary plus humus sludge of 5.9 % solids content C - digested, primary plus surplus activated of 4.2 % solids content.

The effectiveness as a conditioner was tested employing the standard Jones filtration test. This test mesures the amount of conditioning agent required for the treated sludge have a Specific Resistance to filtration (abbreviated to SR) of respectively 4.0 x 1012 m/kg or 2 x 1012 m/kg, as specified. It is inherently desirable to produce a treated sludge having as low a Specific Resistance to filtration as is practicable, and the better that the sludge conditioner is, the lower the dose of it that will be required to achieve any specified SR.The results of the tests are summarised in Table 6 hereinbelow, together with results obtained using a comparison product which comprised a basic aluminium chloride solution containing 15 % product, calculated as A1203 having a basicity of 70 % and produced by the general method of comparison of C22, but on a larger scale. The dose shown in Table 6 is the weight % of conditioner required, based on the sludge to be treated, to achieve the specified SR.

TABLE 6 Sludge SR Dose of conditioner using (% A1203 on sludge solids) m/kg Cobmparison Ex4 Ex 18 Ex 19 A 4 x 1012 0.5 0.5 0.6 0.6 C 4 x 1012 3.5 3.5 3.3 3.2 A 2 x 1012 0.7 0.8 1.2 0.75 B 2 x 1012 1.3 1.2 1.0 0.5 From Table 6 it can be seen that even though the Example products had been produced substantially more quickly than the comparison product, the resultant basic aluminium solution was still at least equally effective at conditioning the sewage sludges, within the limits of accuracy of the Jones filtration test.

Claims

1. A process for the production of a basic aluminium compound comprising the step of reacting aluminium metal with an acid or with a non-basic aluminium salt of an acid at elevated temperature in an aqueous medium in the presence of an effective amount of an accelerator selected from aldoses and ketoses and their corresponding carboxylic acid and hydroxyl derivatives thereof until at least some basic aluminium compound has formed.

2. A process according to claim 1 in which the acclerator is a pentose or hexose.

3. A process according to claim 2 in which the accelerator is xylose and/or the hexose is glucose, fructose or galactose or a mixture thereof.

4. A process according to claim 3 in which the hexose is provided in the form of a di- or poly-saccharide hydrolysable in use to the hexose.

5. A process according to claim 4 in which the di- or poly-saccharide is maltose, lactose, sucrose, starch or intermediate hydrolysis products of starch.

6. A process according to claim 1 in which the accelerator is a 5 or 6 carbon atom-containing glykitol, or glyconic acid or lactone thereof.

7. A process according to claim 6 in which the glykitol is sorbitol.

8. A process according to claim 6 in which the glyconic acid is ascorbic acid.

9. A process according to any preceding claim in which the concentration of accelerator is not more than 5% w/w of the reaction mixture.

10. A process according to claim 9 in which the concentration of accelerator selected from aldoses, ketoses and carboxylic acid derivatives thereof is in the range of 0.01 to 0.5% w/w.

11. A process according to claim 10 in which the concentration of accelerator is in the range of 0.02 to 0.2% w/w.

12. A process according to claim 9 in which the concentration of accelerator selected from glykitols is in the range of 0.4% to 4% w/w.

13. A process according to any preceding claim in which the acid or the non-basic salt of an acid is introduced progressively into a mixture of the aqueous medium, the aluminium metal and the accelerator during a period of 30 minutes to 2 hours.

14. A process according to any preceding claim in which reaction mixture is maintained at an elevated temperature until no solid aluminium metal is detectable therein.

15. A process according to any of claims 1 to 13 in which the concentration of basic aluminium compound in the reaction mixture is monitored and when a predetermined concentration is reached, any solid aluminium is filtered out.

16. A process according to any preceding claim in which the reaction is carried out at a temperature within 5"C of the reflux temperature of the reaction mixture.

17. A process according to any preceding claim in which the reagents are employed in such relative amounts and the reaction continued until the concentration of basic aluminium compound in solution is from 20 to 26% w/w as Awl203.

18. A process according to any preceding claim in which the acid employed is a mono-basic mineral acid.

19. A process according to claim 18 in which the mineral acid employed is hydrochloric acid.

20. A process for producing a basic aluminium compound substantially as described herein with respect specifically to anyone of Examples 1 to 11, 13, 14, 17 to 21,23 and 27 to 29.

21. A basic aluminium compound whenever obtained by a process according to any preceding claim.

22. A process for producing a basic aluminium compound employing any novel feature described herein either by itself or in combination with any other feature described herein and the product so produced.