EP0787039A1

EP0787039A1 - Process for reprocessing and utilizing boron trifluoride catalyst residues

Info

Publication number: EP0787039A1
Application number: EP95934057A
Authority: EP
Inventors: Eberhard Giebeler
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-10-18
Filing date: 1995-10-12
Publication date: 1997-08-06
Also published as: DE4437138C1; AU3649995A; WO1996011744A1

Abstract

The invention concerns a process for reprocessing and utilizing boron trifluoride catalysts which are used in particular for the cationic polymerization, isomerization and alkylation of paraffins and in acylation. After use, the catalyst is reacted with lime, calcium oxide or calcium hydroxide, deactivated and then separated as a filter cake from the reaction mixture. Useful products are extracted from the filter cake. The essential reaction products are calcium fluoride and boric acid which can be separated according to a simple process and utilized in known areas of application.

Description

Process for processing and recycling Bortπfluoπd catalysts

description

Boron trifluorine is used as a catalyst in numerous chemical reactions. Examples of such reactions are cationic polymerizations of olefins and olefin oxides, Fπedel-Crafts alkylations and acylations, isomerizations and alkylations of paraffins

In all cases, the effect of boron trifluond is used as an extremely strong Lewis acid. The catalyst concentrations set vary widely depending on the task and can be between 10 ppm and 10 mol%, based on the components to be reacted in polymerizations and Isomerizations are inevitably controlled by the catalyst concentration in addition to the rate of conversion, the chain length distribution and thus the product properties 20

In the catalytic reactions, boron trifluond is partly gaseous at a defined partial pressure. partly used as a solid or liquid adduct. Liquid adducts are, for example, those of ether, hydrofluoric acid and water; solid adducts use, for example, 2 ^* . Zeolites, silica gel, calcium fiuoπd, inter alia, as a carrier. The combination of a solid carrier and gaseous boron trifluoride secondary components, such as a defined proportion of water, can also have a significant effect on the reaction

In the reactions, the highly corrosive tetrafluoroboric acid forms from boron trifluoron, which, like the boron trifluoron, must be separated from the reaction mixture after the reaction

Because of the high price of boron trifluoride and the sometimes high concentrations of this catalyst required, the recovery of this catalyst is difficult. wishes, but only possible with great effort Simple or improved jerking Recovery processes for the catalyst are a common topic in patent literature

In the simplest case, the gaseous catalyst is recovered by distillation or stipping of the boron fluoride from the reaction mixture and recycling of the gaseous catalyst into the reaction zone

This procedure has been widely described for continuous and discontinuous processes using gaseous boron trifluond as a catalyst (EP

10 318186, FR 2575152 A, SU 1153813 A)

The use of the gaseous boron fluoride in the implementation and recycling of the catalyst is, however, associated with considerable effort and handling and safety risks because of the corrosive effect of the boron fluoride and the corrosive effect of the tetrafluoroboric acid which forms in the presence of water More recently, processes have been described in which the boron trifluond is used and recycled as a liquid or solid adduct

In US Pat. No. 5,120,897 (1990), for an alkylation process, the addition of boron trifluond distilled in the process to Lewis bases, such as, for example, calcium fluoride, is described on 20 activated carbon supports, from which the boron fluoride can be desorbed for reuse. Ad and absorbents are alternative such as polyvinyl alcohol and Lewis bases called Regeneration can be integrated into discontinuous and continuous processes

2s Also in US Pat. No. 5,245,101 (Mobil Oil 1993), an alkylation process based on boron fluoride complexes with complexing agents such as water and phosphoric acid describes a partially complex recycling process which includes the decantation of a phase containing boron fluoride. In addition, the Hydrocarbons are deacidified, since hydrofluoric acid, tetrafluoroboric acid and boron trifluorine are at least

^■ .0 ren are present For this washing or deacidification of the organic products, for example, solid Lewis bases such as calcium fluoride or polyvinyl alcohol or liquid bases such as potassium hydroxide solution are mentioned

The decanted Bortnfluoπd phase can be recycled internally. For the washed-out residual quantities, recycling is not considered to be worthwhile.

3 hen US Pat. No. 5,173,467 (Mobil Oil 1993) describes a complex of boron trifluoride and fluorophophore acid as a catalyst, with which an increased safety is achieved in comparison with the combination of boron trifluoride and hydrofluoric acid. This catalyst is washed out by neutralization and not recycled because the recycling costs are considered too high.

Plant internal recycling of the catalyst always means, in addition to the increased effort in the plant and the safety risk, also an increased quality risk, in particular in reactions in which a kinetically controlled product mixture is formed, such as in particular in polymerizations, oligomerizations and isomerizations. The exact regulation of the catalyst concentration as well as the cocatalysts and adduct formers required for direct recycling within the plant is extremely complex and difficult to control in terms of quality.

That is why external recycling or the disposal of catalyst residues by landfill are widely used in this area. In these cases, the consumption of the catalyst with 0.01-0.5% by weight of boron trifluoride relative to the monomers is relatively low and not very cost-effective. However, external recycling outside the production plant can also be an alternative in other implementations with boron trifluoride. This applies in particular to small production capacities and discontinuous manufacturing processes.

In these cases, the following variant has been found to be preferred: Boron trifluoride is bound to potassium hydroxide solution or potassium fluoride to form stable potassium tetrafluoroborate. Potassium tetrafluorobarate is the preferred starting material for obtaining boron trifluoride from the point of view of energy and yield. The withdrawal of potassium tetrafluoroborate is therefore offered by manufacturers of boron trifluoride, since this residue can be integrated into existing boron trifluoride productions, provided that the potassium tetrafluoroborate is pure, i.e. is also delivered free of organic residues.

US 4981578 (Ethyl Corp. 1991) describes a general process for removing boron trifluoride catalysts from reaction products. Solid alkali fluorides or, alternatively, an aqueous potassium fluoride solution are used as washing-out chemicals called. The dried and pure potassium tetrafluoroborate can be thermally split back into boron trifluoride and potassium fluoride. This is an example of a recycling which is preferably carried out centrally and outside the plant and which helps to reduce the high outlay for recycling within the plant. The relatively high price of potassium fluoride is disadvantageous. An alternative process is based on aqueous potassium hydroxide solution with the disadvantage that water is introduced into the reaction product.

In practice it is e.g. difficult and expensive in the production of hydrocarbon resins catalyzed by boron trifluoride, a potassium tetrafluoroborate free of organic residues such as e.g. Resin residues, as is the case for boron trifluoride

Recovery is a prerequisite. In these cases, complex washing out of the catalyst residue with suitable solvents and their subsequent complete separation by distillation are additionally required.

The known processes for the internal recovery of the catalyst boron trifluoride have partly for the reasons mentioned above. considerable disadvantages and require complex systems and process control. The recycling of catalyst residues outside the plant in the form of potassium tetrafluoroborate has the disadvantage that solid potassium fluoride is an expensive adsorber with poor efficiency for boron trifluoride, which can only be used technically for the recovery of boron trifluoride if the organic residues are completely separated beforehand. This is associated or not possible, particularly in the production of polymers, with increased effort. If potassium fluoride is replaced by potassium hydroxide solution or aqueous potassium fluoride, the adsorber costs can be reduced, but the result is an undesirable introduction of water into the product, particularly in the case of polymers.

The object of the invention was therefore to develop a safe, economical and, as far as possible, universally applicable process for separating the catalysts from the reaction medium with a usability of the catalyst residues, which supplements and improves the known recycling processes. The background to this task was also the consideration of offering an economical central recycling solution for users of boron trifluoride who do not carry out internal recycling, which can replace previous disposal of the catalyst residues in landfills or waste water streams and meet the requirements of a circular economy becomes. The developed process is based on the idea that lime, by far the cheapest Lewis base, is an alternative to the adsorbents and absorbents for boron trifluoride and its accompanying substances described in the patent literature, such as hydrofluoric acid, if it succeeds, an alternative use for to open up the neutration products. The use of lime in the form of calcium oxide, calcium hydroxide or chalk in boron trifluoride recycling has so far explicitly not played a role in the patent literature, since calcium tetrafluoroborate or the mixture of the hydrolysis products calcium fluoride and boric acid are possible but not customary starting materials for the Are boron trifluoride synthesis

The use of lime or calcium compounds for the binding and neutralization of boron trifluoride becomes surprisingly attractive if, in addition to the two alternatives for catalyst residue, landfill and boron trifluide recovery described so far, an alternative use of the reaction products can be developed. The primary adducts are as reaction products Calcium tetrafluoroborate and their hydrolysis products calcium fluoride and boric acid were understood.

A secondary goal of the patent development was, however, the greatest possible separation of the adhering organic components from the original process from the inorganic catalyst residue, because if the organic ingredients can be largely separated off, a higher-value utilization of the inorganic product mixture is also conceivable. eg in the production of boron trifluoride in processes known per se.

A further object of the invention was to process the mixture of calcium fluoride and boric acid resulting from the hydrolysis and to break it down into the two components in such a way that a decoupled and safe use of these two versatile raw materials is possible

The preferred form of presentation of lime in the context of the invention is hydrated lime powder. Due to the manufacturing process, this material has a large surface area and, in contrast to ground quicklime, is quickly and completely available for reaction with boron trifluoride and hydrofluoric acid. can be accepted, the use of an aqueous potassium hydroxide suspension is alternatively possible. Approximately only stoichiometric amounts are required according to the gross reaction equation

3 Ca (OH) ₂ + 2 BF ₃ -> 3 Ca F ₂ + 2 B (OH) ₃

After thorough mixing of the introduced solid with the liquid reaction mixture consisting of catalyst and organic products, the converted solid is separated off by decanting, filtration or centrifugation. In particular in the case of adhering polymers, high boilers or odorless or toxicologically disruptive products, this is initially washed sludge-like residues with a good detergent are useful. To complete and accelerate the hydrolysis of the fluoroborate, the slightly alkaline filter cake is then mixed with water and - in a favorable variant of the process - additionally with calcium chloride, calcium chloride has an accelerating effect on the hydrolysis of the fluoroborate Boric acid

This hydrolysis can be additionally required thermally and preferably takes place simultaneously with the removal by distillation of the adhering organic products or the organic detergents

In the case of a discontinuous process, the process steps of adding water and, if appropriate, calcium chloride, heating, and distillative removal of the solvent and water are carried out. Detergents which can be azeotropically distilled off with water are preferably used in the preceding step Process these steps are carried out in dryers with a length / diameter ratio> 4 and special internals which ensure a low jerk mixing

The desired complete separation of the evaporable organic constituents from the filter cake by distillation is possible in special kneading or thin-layer evaporators. Particularly preferred for drying this sludge are intensively mixing and indirectly heated kneading evaporators. Drying in vacuum mode is preferred. Solids temperatures higher than 165 ° C. are preferably avoided in order to avoid the conversion of orthoboric acid into poorly soluble metaboric acid.

Drying results in a very fine powder mixture of approx. 60-65% calcium fluoride and 30 -35% boric acid if neutralized with a minimal excess of lime. If an excess of lime is used, some of the boric acid is bound as calcium borate. One possible use of this product results from the properties of calcium fluoride as a flux e.g. in cement production and the property of boric acid and borates to influence the setting speed of the cement. Mixtures of calcium fluoride, calcium borate and boric acid can therefore in principle be used in cement production. It is particularly common in cement production to add calcium fluoride as a flux, which enables energy to be saved by reducing the firing temperature.

The fine grain in which this intermediate product is obtained is, however, also particularly favorable for the further processing of the mixture by extraction of the boron compounds. Depending on the excess lime used in the original neutralization, a stoichiometric amount of sulfuric acid is preferably added before the extraction in order to release boric acid from the calcium borate. Preferred solvents for boric acid extraction are hot (70-120 ° C.) water or combinations of hot water and up to 0.2 parts by weight of sodium hydroxide solution, based on the proportion of boric acid, or in particular also water-soluble aliphatic amines and alkanolamines. The subsequent separation of the extract from insoluble calcium fluoride is carried out by filtration or preferably by centrifugation.

The use of hot water has the advantage that, after the aqueous phase has cooled, a technical boric acid crystallizes out, so that a separation into crystalline boric acid and an aqueous phase which can be used for further extractions is easily possible. The background is the pronounced temperature dependence of the solubility of boric acid in water, which is 23% by weight at 90 ° C and only 4.6% by weight at 20 ° C.

The solubility and dissolution rate of the boron compounds could be increased by adding small amounts of sodium hydroxide solution. This results in mixtures of Boric acid and sodium borates, which can be used directly in wood preservative formulations. Surprisingly, a rapid and high extraction of the boric acid with the formation of a clear aqueous phase was found in the manufacture of boric acid concentrates with the addition of sodium hydroxide solution in the heat. This result is also surprising because in patent DE 3633366 A1 the attempt to dissolve crystalline boric acid with water in a ratio of 1: 1 to 1: 5 and sodium hydroxide amounts of 0.01-0.2%, based on the boric acid, increases stable boric acid suspensions. These suspensions would then have been difficult to separate from the very fine-grained calcium fluoride. In this respect, the production of clear phases according to the invention is a surprising and favorable result, which can be explained by the extremely fine distribution in which the boric acid is present in the process according to the invention. If the goal is to achieve the purest possible boric acid solution, the amount of caustic soda is minimized. If, on the other hand, an increased proportion of alkali is permissible, the proportion of alkali can be increased as desired to improve the degree of extraction. The temperature dependence of the solubility of sodium borate is even more favorable for the process than for boric acid: approx. 2.4% at 20 ° C, approx. 37% at 90 ° C.

Such concentrates of boric acid or its sodium salts have a widespread use as a fungicide and as a fire protection agent. This gives the opportunity to allow the extract from the removal of the boric acid to flow directly into such formulations without further workup steps.

It was also found that even with water-soluble aliphatic amines and polyamines in the presence of alcohols or with alkanolamines, an extraction in the solid boron compounds can be carried out particularly well. Particularly in alkanolamines, highly concentrated boric acid solutions can be achieved in a weight ratio of boric acid: alkanolamine> 2: 1.

The calcium fluoride residue remaining during the extraction is preferably washed with water. The boric acid-containing wash water can be used together with the extract directly as an aqueous fungicide, for example in the area of particle board, or after cooling and partial crystallization of the boric acid in a cycle mode can be used for further boric acid extractions. The residue, which is largely freed from boric acid, consists almost exclusively of calcium fluoride, which is used as a flux and as a raw material source for hydrofluoric acid and other fluorochemicals. The fine-grained form is generally of great advantage for use as a flux. There is no need for complex milling processes. The high purity of this calcium fluoride compared to naturally occurring technical qualities is important for use as a raw material for fluorine chemistry, in particular the production of hydrogen fluoride. In the case of natural calcium fluoride, for example, accompanying substances such as quartz interfere considerably, since in this case, in addition to hydrogen fluoride, the silicon tetrafluoride, which would then be difficult to separate, would also arise. By selecting extremely pure lime qualities for the implementation of the catalysts it is possible to obtain extremely pure and fine calcium fluoride particles. This also shows a way of producing fine, amorphous calcium fluoride which can offer advantages in special applications, for example in the production of special glasses such as frosted glass or optical lenses.

The following examples illustrate the invention but are not intended to limit it.

example 1

The discontinuous production of a hydrocarbon resin by cationic polymerization with the addition of boron trifluoride (used as an adduct with diethyl ether) is terminated by adding powdered lime (hydrated lime) in the well-stirred stirred tank. 2 parts by weight of calcium hydroxide were added to 1 part by weight of boron trifluoride. After switching off the stirrer, the solid phase formed was filtered off and washed with an aromatic solvent mixture in the boiling range 160-210 ° C. The filter cake was then dried in a 160 l turbulent dryer (Drais) by indirect heating at an absolute pressure of 60 mbar. The speed of rotation of the kneading arms of the tumble dryer was 90 rpm. In contrast to the drying of other sludges, increased sludge toughness was not observed in any phase. The final temperature of the solid was 160 ° C. The dried filter cake still contained 0.3% hydrocarbon resin that had not been washed out and 0.03% of the detergent. The grain size distribution of the fine powder was as follows: 10% <2 ^■ 10 ^"6 m; 50% <3.5 ^* 10 ^{" 6} m; 90% <10 - 10 ^"6 m; 97% <25 ^* 10 ^{" 6} m Example 2

The powder obtained in Example 1 was admixed with 3 parts of water and 0.03 part of sodium hydroxide solution at 90 ° C. and stirred in the turbulent mixer described in Example 1 for 4 hours. After the kneading elements had been switched off, the calcium fluoride settled rapidly -containing solution separated The analysis of the solution showed that 69% of the amount of boron had gone into solution

Example 3

The powder obtained in Example 1 was adjusted to pH 50 with dilute sulfuric acid, mixed with 1 part of monoethanolamine and 0.1 part of calcium chloride and stirred at 40 ° C. for 5 hours. Analysis of the extract solution showed that 91.5% of the existing Amount of boron had gone into solution

EXAMPLE 4 s The powder obtained in Example 1 was adjusted to pH 5 with aqueous sulfuric acid and 1 part of powder 6 parts of water were slurried with water in a weight ratio of 80 and the mixture was stirred for 4 hours. After filtration and rinsing with 2 parts by weight of water, based on the solids obtained, 82% of the total amount of boron was contained 0

Example 5

The powder obtained in Example 1 was melted at 1330 ° C. in an oxidizing flame. The melt solidified on cooling to form a light slag with a closed ceramic surface. The weight ratio of boron and fluorine s remained unchanged. The subsequent reaction of this solidified melt with oleum at 120 ° C gave gaseous boron trifluond. The decomposition and decomposition of the solids proceeded quickly and completely

Example 6 0 The powder obtained in Example 1 with still small amounts of high-boiling organic residues was subjected to pyrolysis at 450 ° C. for 2 hours. The organic residues then had no noticeable odor. The petroleum ether extract of the residue gave 1200 ppm extractable organic Fabrics

Claims

Claims:

1.Process for the processing and recycling of boron trifluoride catalyst residues, characterized in that the reaction product containing these catalyst residues is treated in the following order: (a) neutralization with lime, quicklime or hydrated lime in at least a stoichiometric amount based on the content of boron trifluoride and hydrogen fluoride or tetrafluoroboric acid, (b) separation of the solid adducts and neutralization products from lime and the catalyst residues, (c) washing out high boilers and polymers from the separated sludge-like adduct with suitable solvents, (d) pasting up the sludge with water if necessary with the addition of sulfuric acid at least in the stoichiometric ratio to the excess lime and if necessary additionally from 0.1 to 5% by weight of calcium chloride, (e) thermal treatment of the sludge, (f) dissolving or extracting the boric acid from the dried residue with a at least 2 times the excess of water , based on the boric acid content at temperatures above 70 ° C, or dissolving or extracting the boric acid in a water-soluble aliphatic amine or polyamine in the presence of mono- or polyhydric alcohols or in water-soluble alkanolamines or alkoxiamines, (g) separating and washing the insoluble residue with hot water, whereby depending on the system and the later use, the sub-steps (c), (d), (f) and (g) may be omitted in whole or in part.

2.The method according to claim 1 (f), characterized in that the amine monoethano¬ lamin is used in a weight ratio of 1: 1 to 1: 4 to the amount of boric acid.

3. The method according to claim 1, characterized in that, in deviation from step (f), the boric acid is dissolved in a 3-8 times excess of water, based on the amount of boric acid present, at temperatures between 70 ° C and 140 ° C and then after Separation and washing of the insoluble residue, the boric acid is crystallized from the solutions by cooling, the cooled liquid phase depleted in boric acid being used again in the cycle for boric acid extraction.

4. The method according to claim 3, characterized in that in step (f) the water, based on the amount of boric acid to be extracted, contains stoichiometrically 0.05-100% alkali metal hydroxide.

S.Procedure according to one of claims 1 to 4, characterized in that in step (a) lime with turbulent mixing in the form of hydrated lime as a fine-grained powder or as an aqueous suspension in a 5-50% stoichiometric excess based on the total amount boron trifluoride, hydrofluoric acid and other acidic components are added.

6. The method according to any one of claims 1 to 5, characterized in that the separation of the sludge phase in step (b) is carried out by filtration.

7. The method according to any one of claims 1 to 6, characterized in that the thermal treatment in step (e) by direct or direct heating in a sludge dryer at temperatures up to 165 ° C to separate the evaporable ingredients.

δ.Verfahren according to any one of claims 1-7, characterized in that the thermal treatment in step (e) is carried out by combining drying and subsequent pyrolysis or melt.

9. Use of the solid obtained according to one of claims 1 to 6 in step (e) as a flow aid for mineral melts or as a raw material for the

Boron trifluoride production.

10. Use of the calcium fluoride obtained according to one of claims 1 to 6 in step (g) as a flow aid, as a raw material for the production of special glasses or as a raw material for the production of hydrofluoric acid

11. Use of the boric acid concentrate obtained according to one of claims 1 to 10 after step (g) as a formulation component for wood and fire protection agents, in particular in the area of particle board.