Europaisches Patentamt J European Patent Office CO Publication number: 0 302 970 Office europeen des brevets A1 EUROPEAN PATENT APPLICATION © Application number: 87307086.6 © int. ci.4: C07H 3/02 ® Date of filing: 11.08.87 @ Date of publication of application: © Applicant: UOP INC. 15.02.89 Bulletin 89/07 25 East Algonquin Road Des Plaines Illinois 6001 7-501 7(US) © Designated Contracting States: AT BE CH DE FR GB IT LI NL SE @ Inventor: Chang, Chin-Hsiung 511 Revere Lane Palatine Illinois 60067(US) 0 Representative: Brock, Peter William UOP Processes International Corporation 48 Leicester Square London WC2H 7LW(GB) Process for separating psicose from another ketose. © Psicose is sepatated from at least one other ketose in an adsorption step using a type Y zeolite adsorbent having calcium cations at exchangeable cationic sites. After desorption, psicose is recovered in the extract in high purity with the other ketose or ketoses being concentrated in the raffinate. In a preferred mode of operation, the psicose separation is performed with an aqueous feed mixture of monosaccharides containing psicose along with other aldoses and ketoses. The feed is contacted with a calcium-Y type zeolite in two stages. In the first stage, psicose and fructose are selectively adsorbed, to the substantial exclusion from the extract of other aldoses. In the second stage, psicose is adsorbed from the extract of the first stage, and recovered in higher purity than the feed. Fructose is recovered substantially psicose-free in high purity in the raffinate. 200000 'GLUCOSE * I6OOOO ft: ^ 120000 ^J 80000 psicose o oc j/oooo CO ,O IO ZO 3O HO SO 6O 7O BO 9O too LLJ RETENTION VOLUMN, ML. JT/G. f Xerox Copy Centre EP 0 302 970 A1 "PROCESS FOR SEPARATING PSICOSE FROM ANOTHER KETOSE" This invention relates to the solid bed adsorptive separation of psicose (a ketose), from other ketoses and aldoses. More specifically, the invention relates to a process for separating psicose from a mixture comprising psicose, fructose and one or more additional ketoses, and-or aldoses, which process employs an adsorbent comprising a calcium-exchanged Y-type zeolite for selective adsorption of psicose from the 5 feed mixture. The use of crystalline aluminosilicates in non-hydrocarbon separations is known, for instance for separating specific carbohydrate feed mixtures. A specific example of such a separation is given in US-A- 4024331 disclosing the separation of ketoses from a mixture of ketoses and aidoses using a type X zeolite. Specific monosaccharides, such as glucose and fructose, are isolated from a feed mixture containing the w same by an adsorptive separation process using an X zeolite as taught in US-A-4442285. This invention is particularly concerned with the separation of a ketose, psicose, from another ketose, fructose, mixed with the aldoses mannose and glucose. Heretofore, no feasible method for commercially separating psicose from the other products of isomerization of aldose sugars, e.g., glucose, was available. Therefore, enzymatic means, rather than simple isomerization methods, have been used for the productiuon 75 of fructose, because the enzymatic route minimizes the production of psicose. A means for separating psicose from fructose, and other ketoses and aldoses, has now been discovered and this means that simpler, less costly isomerization methods can be used to produce fructose. There are two isomerization routes known for obtaining fructose from glucose, namely by the reaction of weak alkali with glucose and the reaction of hot pyridine with glucose, (see Chemistry of the Carbohydrates Pigman et al., Academic 20 Press Inc. NY, NY 1948, pages 41, 126-7). Similarly, isomerization of galactose) and a mixture of ketoses, (sorbose and tagatose) which may be separated by means here disclosed. Furthermore, there is consider- able interest in the various L-sugars, which are believed to below in calories and possibly non-metabolized, and which cannot be made enzymatically, but only by isomerization routes such as those mentioned above. This invention applies to the L-sugars as well as D-sugars, and is seen to be an advantageous method for 25 obtaining L-fructose, free of contamination by L-psicose. Data related to potential adsorbents for the separation of mannose from other monosaccharides are set forth in US-A-4471 1 1 4. This patent contains data related to theuse of a Y type faujasite exchanged with calcium cations as an adsorbent for the adsorbent for the separation of mannose from glucose and other monosaccharides. 30 The separation on mannose from glucose is the subject of GB-A-1 540556, in which the adsorbent is a cation exchange resin in salt form, preferably calcium form. US-A-4340724 teaches the separation by adsorption of a ketose from an aldose, with a Y zeolite exchanged with NH4, Na, K, Ca, Sr, Ba or combinations thereof at ion exchangeable sites, or will an X zeolite exchanged with Ba, Na, Sr or combinations thereof. 35 The separation of psicose from other ketoses is stated US-A-4096036 to be possible with ion exchange resins capable of complexing with a polyol at a first temperature, and dissociating the complex at a second temperature in a thermal parametric pumping apparatus. Accordingly, the present invention concerns the problem of providing a process forthe separation of a ketose from feed mixture which is the alkaline- or pyridine-catalyzed isomerization product of an alddohex- 40 ose or aldopentose. This problem is solved by using a Y type zeolite with calcium cations at cation exchanged sites. In one embodiment, this invention provides a process for separating psicose from an aqueous feed misture containing psicose and at least one other ketose, contacting said mixture with an adsorbent comprising a type Y zeolite having calcium cations at exchangeable cationic sites, thereby selectively 45 adsorbing said psicose, separating the nonadsorbed portion of the feed mixture from the adsorbent, and thereafter recovering psicose by contacting the psicose-containing adsorbent with desorbent. In another embodiment, this invention provides a process for recovering fructose substantially free of psicose from a feed mixture comprising fructose and psicose and at least one other monosaccharide selected from glucose and mannose, by contacting said feed mixture with a first adsorbent comprising a so type Y zeolite having calcium cations at exchangeable sites, thereby selectively adsorbing said psicose and said fructose, separating the nonadsorbed portion of the feed mixture from the adsorbent, recovering an extract mixture comprising said psicose and said fructose from said first adsorbent, and then contacting said extract mixture with a second adsorbent comprising a type Y zeolite having calcium cations at exchangeable sites, thereby selectively adsorbing said psicose, separating the nonadsorbed portion of said extract mixture from the second adsorbent to form a substantially psicose-free raffinate containing fructose, EP 0 302 970 A1 and thereafter recovering said psicose by desorption of the second adsorbent. In either embodiment, the psicose may be recovered by desorption using, for example, water as desorbent. Alternatively, the psicose may be selectively adsorbed in the first step to produce a raffinate containing 5 fructose and other monosaccharides in the original feed mixture. The psicose can be recovered by desorption under desorption conditions with water as desorbent. Subsequently, the raffinate phase contain- ing non-adsorbed fructose can again be contacted with a Ca-exchanged Y zeolite, the fructose being selectively adsorbed by the zeolite, and recovered as one product by desorption with water. Other details and embodiments of the present invention relate to specific feed mixtures, adsorbents, desorbent materials, w operating conditions and flow cofigurations, all of which are hereinafter disclosed in the following discussion of the present invention. The single Figure of the Drawings provides a graphical representation of relative concentration of specified sugars versus retention volume for the process of the present invention. At the outset the definitions of various terms used through the specification will be useful in making rs clear the operation and advantages of this process. A "feed mixture" is a mixture containing one or more extract components and one or more raffinate components to be separated by this process. The term "feed stream" indicates a stream of a feed mixture which passes to the adsorbent used in the process. An "extract component" is a component that is more selectively adsorbed by the adsorbent, while a 20 "raffinate component" is a component that is less selectively adsorbed. The term "desorbed material" means generally a material capable of desorbing an extract component. The term "desorbent stream" or "desorbent input stream" means a stream of desorbent material which is passed to the adsorbent. The term "raffinate stream" or "raffinate output stream" means a stream by which a raffinate component is removed from the adsorbent. The composition of the raffinate stream can vary from essentially 100% desorbent 25 material to essentially 100% raffinate compounds. The term "extract stream" or "extract output stream" means a stream in which an extract material which has been desorbed by a desorbent material is removed from the adsorbent. The composition of the extract stream, likewise, can vary from essentially 100% desorbent material to essentially 100% extract components. At least a portion of the extract stream, and preferably at least a portion of the raffinate stream, from the adsorption - desorption process are passed to 30 separation means, typically fractionators or evaporators, where at least a portion of desorbent material is separated to produce an extract product and a raffinate product. The term "extract product" and "raffinate product" mean products produced by the process containing, respectively, an extract component and a raffinate component in higher concentrations than those found in the extract stream and the raffinate stream. The adsorbent materials used according to this invention comprise type Y crystalline aluminosilicates 35 having calcium cations at cation exchange sites.