Classifications

• • C—CHEMISTRY; METALLURGY
  • C13—SUGAR INDUSTRY
  • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
  • C13B20/00—Purification of sugar juices
  • C13B20/14—Purification of sugar juices using ion-exchange materials
• • C—CHEMISTRY; METALLURGY
  • C13—SUGAR INDUSTRY
  • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
  • C13B20/00—Purification of sugar juices
  • C13B20/14—Purification of sugar juices using ion-exchange materials
  • C13B20/146—Purification of sugar juices using ion-exchange materials using only anionic ion-exchange material

Definitions

• the present application relates to a process for decolorization of sugar juices with monodisperse ion exchangers according to claim 1.
• monodisperse anion exchangers are used for the inventive use.
• Sugar is produced by numerous plants. Economically important is the extraction of sugar from sugar beets and cane sugar from sugar cane as well as sugar from corn, wheat, rice, cassava, potatoes and starch hydrolysates.
• sugar When sugar is produced either by extraction of beet pulp with hot water or by pressing sugar cane, a raw sugar solution, the so-called thin juice or pressed juice won. It contains, in addition to the sugar content, varying amounts of non-sugar, such as alkali and alkaline earth, chloride and sulfate ions, pyrrolidone carbon and amino acids. During the concentration of the pressed juices, further dyes such as caramel dyes and melanoidins are formed.
• non-sugar such as alkali and alkaline earth, chloride and sulfate ions, pyrrolidone carbon and amino acids.
• Colored ingredients present in sugars are predominantly anionic in nature.
• substances some of which are high molecular weight Nature are.
• they may contain carboxyl groups, amino groups, phenolic groups and other structural elements.
• the decolorization of sugar solutions can be carried out in high-color crude solutions (> 1000 lcumsa) by precipitation methods based on carbonation, Sufitation or Phosphatation. Less colored solutions ( ⁇ 1000 lcumsa) are decolorized either by physical processes such as crystallization or adsorption processes using ion exchangers or activated carbon.
• the dye content of the solutions is determined by photometric measurement at 420 nm. The details are explained in the examination methods.
• the unit of dye content is Icumsa.
• Icumsa is equal to the product 1000 ⁇ E koe .
• E koe is equal to the extinction coefficient.
• bead-type adsorbent resins based on crosslinked polystyrene / divinylbenzene or on a polyacrylate basis are available.
• the adsorber resins are usually strong base anion exchangers with different porosity.
• macroporous or gelfdrmige types are preferably used.
• According to the dye supply one, two or three stages are worked. Combinations of different ion exchangers based on acrylate and / or styrene / divinylbenzene on the one hand and macroporous and / or gel-type types on the other hand are conceivable.
• US Pat. No. 2,874,132 uses gel-type strongly basic anion exchangers with quaternary ammonium groups based on styrene / divinylbenzene with divinylbenzene contents of 0.5 to 2% by weight for sugar juice dyeing.
• the anion exchangers are used in particular in mixed beds together with weakly acidic cation exchangers.
• Macroporous anion exchangers and acrylic resins have greater absorptivity for dye components and exhibit higher physical stability than gel anion exchangers in sugar juice dyeings.
• the performance of the bead-shaped adsorber resins is determined inter alia by the porosity, the inner surface, the particle size and the degree of functionalization. Fine particles have a larger outer surface and therefore a better adsorption capacity. However, due to the high viscosity of the highly concentrated sugar syrups and the very fast adjusting maximum pressure loss that occurs when the sugar solution is filtered through the adsorber resin bed. By contrast, coarse beads only cause a low pressure drop, However, they are characterized by lower adsorption capacity compared to the sugar colors.
• the ion exchangers and adsorbers used according to the prior art are bead polymers having a broad bead size distribution (heterodisperse ion exchangers).
• the bead diameter of these adsorber resins is in the range of about 0.3 to 1.2 mm.
• the preparation of the polymer beads on which they are based can be carried out by known methods of suspension polymerization, cf. Ullmann's Encyclopedia of Industrial Chemistry, 5 th ed., Vol. A 21, 363-373, VCH Verlagsgesellschaft mbh, Weinheim 1992.
• the beads Due to the presence of different sized ion exchangers, the beads exhibit different adsorption capabilities for the dyes. This leads to a broad Adsorbtions- and separation front.
• the object of the present invention was therefore to search for suitable ion exchangers which avoid the disadvantages of the broad adsorption front and separation front and with the aid of which sugar juices of high quality and quality are obtained.
• the high quality and quality is reflected in the least possible discoloration of the sugar juices.
• Monodisperse ion exchangers can be obtained by functionalization of monodisperse bead polymers.
• Monodisperse in the present application refers to those substances in which at least 90% by volume or by mass of the particles have a diameter which lies in the interval of ⁇ 10% of the most frequent diameter around the most frequent diameter.
• a bead polymer its beads have a most common diameter of 0.50 mm, at least 90% by volume or mass% in a size interval between 0.45 mm and 0.55 mm, or a bead polymer whose beads have a most common diameter of 0.70 mm have at least 90% by volume or mass% in a size interval between 0.77 mm and 0.63 mm.
• the ion exchangers can be present or used as microporous or gelatinous or macroporous bead polymers.
• microporous or gel or macroporous are known from the literature, for example from Adv. Polymer Sci., Vol. 5, pages 113-213 (1967).
• seed / feed process One of the possibilities for producing monodisperse ion exchangers is the so-called seed / feed process, according to which a monodispersed, unfunctionalized polymer ("seed") is swollen in monomer and this is then polymerized.
• seed / feed methods are described, for example, in patents EP-0 098 130 B1, EP-0 101 943 B1, EP-A 418 603, EP-A 448 391, EP-A 0 062 088, US-A 4 419 245 ,
• monodisperse ion exchangers Another possibility for producing monodisperse ion exchangers is to produce the underlying monodisperse bead polymers by a process in which the uniformly formed monomer droplets are formed by vibrationally exciting a laminar flow of monomers and are subsequently polymerized, see US Pat. No. 4,444,961, EP-0 046 535 DE-A-19954393.
• a uniformly formed drop of a monomer / porogen mixture is formed by vibrationally exciting a laminar flow of a mixture of monomers and porogen and then polymerizing.
• anion exchangers to be used for the inventive use are present as bead polymers in monodisperse form. They contain secondary or tertiary amino groups or quaternary ammonium groups or mixtures thereof. Thus, the use of anion exchangers with trimethylamine, dimethyl or dimethyl, hydroxyethylammonium groups is customary.
• They consist of crosslinked polymers, ethylenically monounsaturated monomers which consist predominantly of at least one compound of the series styrene, vinyltoluene, ethylstyrene, ⁇ -methylstyrene or their ring-halogenated derivatives such as chlorostyrene; they may also contain one or more compounds from the series vinylbenzyl chloride, acrylic acid, their salts or their esters, in particular their methyl esters, furthermore vinylnaphthalenes, vinylxylenes or the nitriles or amides of acrylic or methacrylic acids.
• crosslinking monomers include, for example, polyfunctional vinylaromatics such as di- or trivinylbenzenes, divinylethylbenzene, divinyltoluene, divinylxylene, divinylethylbenzene, divinylnaphthalene, polyfunctional allylaromatics such as di- or triallylbenzenes, polyfunctional vinyl or allyl heterocycles such as trivinyl or triallyl cyanurate or isocyanurate, N, N ' C 1 -C 6 -alkylenediacrylamides or -dimethacrylamides such as N, N'-methylenediacrylamide or -dimethacrylamide, N, N'-ethylenediacrylamide or -dimethacrylamide, polyvinyl or
• the crosslinking monomers are generally used in amounts of 1 to 80 wt .-%, preferably 2 to 25 wt .-%, based on the total amount of the polymerizable monomers used.
• crosslinking monomers need not be used in their pure form, but may also be used in the form of their technically-treated, lower-purity mixtures (such as divinylbenzene mixed with ethylstyrene).
• free-radical-forming catalysts include, for example, diacyl peroxides such as diacetyl peroxide, dibenzoyl peroxide, di-p-chlorobenzoyl peroxide, lauroyl peroxide, peroxyesters such as tert-butyl peroxyacetate, tert-butyl peroctoate, tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxybenzoate, Dicyclohexyl peroxydicarbonate, alkyl peroxides such as bis (tert-butylperoxybutane), dicumyl peroxide, tert-butylcumyl peroxide, hydroperoxides such as cumene hydroperoxide, tert-butyl hydroperoxide
• diacyl peroxides such as diacetyl peroxide, dibenzoyl peroxide,
• the radical formers can be used in catalytic amounts, ie preferably 0.01 to 2.5% by weight, in particular 0.12 to 1.5% by weight, based on the sum of monomer and crosslinker.
• the water-insoluble monomer / crosslinker mixture is added to an aqueous phase which preferably contains at least one protective colloid for stabilizing the monomer / crosslinker droplets in the disperse phase and the resulting bead polymers.
• protective colloids natural and synthetic water-soluble polymers, e.g. Gelatin, starch, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid or copolymers of (meth) acrylic acid or (meth) acrylic esters are preferred.
• cellulose derivatives in particular cellulose ethers or cellulose esters, such as methylhydroxyethylcellulose, methylhydroxypropylcellulose, hydroxyethylcellulose or carboxymethylcellulose.
• the amount used of the protective colloids is generally 0.02 to 1 wt .-%, preferably 0.05 to 0.3 wt .-%, based on the water phase.
• the weight ratio aqueous phase / organic phase is in the range of preferably 0.5 to 20, in particular 0.75 to 5.
• the base polymers are prepared during the polymerization in the presence of a buffer system.
• buffer systems which adjust the pH of the aqueous phase at the beginning of the polymerization to a value between 14 and 6, preferably between 12 and 8.
• protective colloids with carboxylic acid groups are wholly or partially present as salts. In this way, the effect of protective colloids is favorably influenced.
• the buffer concentration in the water phase is preferably 0.5 to 500 mmol, in particular 2.5 to 100 mmol per liter of aqueous phase.
• the monomer stream is injected into the aqueous phase, the generation of droplets of uniform size being avoided by oscillation-induced jet decay and / or microencapsulation of the resulting monomer droplets of coalescence is ensured (EP 0 046 535 B1 and EP 0 051 210 B1).
• the polymerization temperature depends on the decomposition temperature of the initiator used. It is generally between 50 and 150 ° C, preferably between 55 and 100 ° C. The polymerization takes 0.5 to a few hours. It has been proven to use a temperature program in which the polymerization at low temperature, e.g. 60 ° C, started and the reaction temperature is increased with increasing polymerization conversion.
• the resulting bead polymers can be fed to the functionalization as such or else via an intermediate having an enlarged particle size which can be obtained by a so-called seed / feed process.
• a seed / feed process involves the steps of "feeding" the originally obtained polymer ("seed") with copolymerizable monomers and polymerizing the monomer that has penetrated into the polymer. Suitable seed / feed processes are described, for example, in EP 0 098 130 B1, EP 0 101 943 B1 or EP 0 802 936 B1.
• porogens are added to the monomer / crosslinker mixture, as described, for example, in Seidl et al., Adv. Polym. Sci., Vol. 5 (1967), pp. 113 to 213, e.g.
• aliphatic hydrocarbons preferably hexane, octane, isooctane, isododecane, isodecane, methyl isobutyl ketone or methyl isobutylcarbinol, in amounts of 1 to 150% by weight, preferably 40 to 100% by weight, in particular 50 to 80 wt .-%, based on the sum of monomer and crosslinker.
• Macroporous bead polymers have pore diameters of about 50 angstroms and larger.
• resin volume 1 bed volume [BV]
• the resin bed was backwashed for 15 minutes to adjust the usual classification of the resin beads as necessary and to free the resin bed of any debris.
• the to be decolored aqueous sugar solution in a possible concentration between 5 - 72% dry matter content of sugar and a color content of 50 -. 3000 Icumsa filtered through the Adsorberharzbett in the loading direction from top to bottom or in the reverse flow direction. In a Aufstraubeladung the formation of a fixed bed is to strive. The filtration rate during decolorization is 1-5 bed volumes / hour). The decolorizable in this arrangement sugar solution volume is dependent on the color content of the starting solution. Depending on the color content, 50 - 200 bed volumes per cycle are possible.
• the adsorber resin After passing through the sugar solution intended for decolorizing, the adsorber resin is sweetened with demineralized water, that is to say freed from sugar.
• demineralized water that is to say freed from sugar.
• the flow rate at decanting corresponds to the flow rate set during loading.
• the volume of water required for desiccation, an important indicator for the sugar industry, is 2-4 BV, depending on the adsorber resin.
• the adsorbent resin is regenerated with 2 BV of an alkaline saline solution in the concentration of 10% NaCl and 1-2% NaOH and thereby of in the Pre-loading of absorbed sugar colors freed.
• the regeneration solution is filtered through the resin bed within one hour and then displaced with demineralized water at the same flow rate and the residual chemicals are also washed with deionized water to pH 7. The volume of water required for this purpose is determined.
• Table 1 Decolorization of sugar solutions with monodisperse and heterodisperse anion exchangers bed volume Resin A Monodisperse gel-like strongly basic anion exchanger Resin B heterodisperse gel-form strongly basic anion exchanger Resin C monodisperse macroporous strongly basic anion exchanger Resin D heterodisperse macroporous strongly basic anion exchanger 5 91.8 79.0 88.8 86.5 10 91.6 72.0 88.7 86.3 55 82.4 53.0 77.1 74.0 65 80.3 50.1 74.7 71.4 72 79.0 47.2 72.4 69.0
• the beet sugar solution to be decolored has a color content of 1000 Icumsa, a temperature of 75 ° C, a dry matter of 65%.
• the loading is carried out with a specific load of 3 bed volumes per hour, the total loading time is 24 hours.
• the monodisperse gelatinous and macroporous strongly basic anion exchangers show distinctly better decolorization performances than the comparable heterodisperse types.
• Sweet on amount of water the ion exchanger prepared for decolorization is applied with a sugar solution of predetermined concentration, for example 60 Brix, until the sugar concentration in the feed is the same as in the discharge.
• the required amount of water is equal to the sweet on amount of water.
• Sweet off amount of water after passing through the intended for decolorization sugar solution, the adsorbent resin is sweetened with demineralized water, that is, free of sugar.
• demineralized water that is, free of sugar.
• the water front fed in from above pushes the specifically heavier sugar solution out of the filter until no sugar (dry matter content equal to zero) can be detected in the filter outlet.
• the volume of water required for sedimentation is the sweet off amount of water.
• Rinse water after completion of the loading of the resin with sugar solution, the resin is regenerated with 2 bed volumes of an alkaline saline solution. With demineralized water, the remainder of the regeneration chemicals are washed out. The amount of water required for this is the rinse water.
• Table 2 Rinse water sweet on sweet off Water levels on sugar juice discoloration Lewatit Mono Plus® Lewatit Mono Plus® Lewatit.RTM M 500 MP 500 MP 500 Rinse water in bed volume 2.25 2.75 4.0 Sweet on in bed volume 1.25 1.25 1.5 Sweet off in bed volume 1.25 1.75 2.0
• the two monodisperse resins require significantly less water than a heterodisperse strongly basic, macroporous anion exchanger.
• the monodisperse gel-type strongly basic anion exchanger requires even less water for the processes mentioned than the monodisperse, macroporous strongly basic anion exchanger.

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• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Biochemistry (AREA)
• Organic Chemistry (AREA)
• Treatment Of Liquids With Adsorbents In General (AREA)
• Treatment Of Water By Ion Exchange (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Saccharide Compounds (AREA)
• Non-Alcoholic Beverages (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Peptides Or Proteins (AREA)

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• 2000
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