SE179723C1

SE179723C1 -

Info

Publication number: SE179723C1
Authority: SE
Publication date: 1962-01-01

Description

Uppfinnare: jD Garber och R E Jones Prioritet begdrd fran den 26 november 1956 (USA) Foreliggande uppfinning avser ett fOrfarande for framstallning air 5-hydroximetyl-furfural (HMF) fran sacker. Uppfinningen avser ett kontinuerligt forfarande som utfores yid relativt hoga temperaturer, for omvandling av invertsocker, glykos, fruktosaner, fruktos eller sackaros och hydrolyserat tra eller starkelse (i fortsattningen kallade socker) i vattenlOsning till HMF. Forfarandet Or saval snabbt som effektivt. Inventors: J. Garber and R. E. Jones Priority Required as of November 26, 1956 (USA) The present invention relates to a process for producing air 5-hydroxymethyl-furfural (HMF) from sacs. The invention relates to a continuous process carried out at relatively high temperatures, for the conversion of invert sugar, glucose, fructosans, fructose or sucrose and hydrolysed starch or starch (hereinafter referred to as sugar) in aqueous solution to HMF. Procedure Or saval quickly and efficiently.

Det Si kant att omvandla sackaros till HMF i sma satser med syrakatalysator, sasom utspadda mineralsyror eller organiska syror, t. ex. oxalsyra, och vid relativt laga temperaturer. Med de lAnga omvandlingstiderna och lOga utbytena ha de hittills kanda forfarandena joke varit kommersiellt praktiska. De maximalt angivna utbytena ha uppnatts vid 162 —167°C, varvid HMF-utbytet faller till 0 vid 225°C. Humin är en ay produkterna: fran omvandlingsreaktionen och vid de hittills anvinda temperaturerna har utbytet Gray Rat progressivt med en Wining av temperaturen och har betankligt paverkat utvinningen ay HMF. It Si edge to convert sucrose to HMF in small batches with acid catalyst, such as diluted mineral acids or organic acids, e.g. oxalic acid, and at relatively low temperatures. With the long conversion times and low exchanges, the hitherto known procedures joke have been commercially practical. The maximum stated yields have been reached at 162-167 ° C, with the HMF yield falling to 0 at 225 ° C. Humin is one of the products: from the conversion reaction and at the temperatures used hitherto, the exchange of Gray Rat has progressively with a Wining of the temperature and has significantly affected the recovery of HMF.

Humin är ett brunt till svart, luckert fast amne, som Or nastan fullstandigt olosligt i vat-ten, alkalier, syror och organiska losningsmedel ay alla slag. Det bildar en belaggning pa reaktionskarlens vaggar och tjanar sasom effektiv varmeisolering, varigenom dalig varmeoverforing astadkommes. Det ger Oven upphov till emulgering av vattenfasen med olika losningsmedel for extraktion och komplicerar problemet med utvinningen am HMF. Humin is a brown to black, loose solid substance which is almost completely insoluble in water, alkalis, acids and organic solvents of all kinds. It forms a coating on the rocks of the reaction vessel and thus serves as effective thermal insulation, thereby achieving poor heat transfer. This gives rise to the emulsification of the aqueous phase with various solvents for extraction and complicates the problem of the recovery of HMF.

Det har nu visat sig, att socker i vattenhaltig losning kan omvandlas till HMF vid temperaturer Over c:a 250° G under hOgt utbyte, pa kort tid, utan bildning ay lagtemperaturforfarandenas humin och med forbattringar i effektiviteten av HMF-utvinningen. Uppfinningen avser ett kontinuerligt fOrfarande for omvandling am socker till HMF vid temperaturer fran c:a 250° G till c:a 380° C samt utvinning am HMF. Uppfinningen innefattar ett tid-temperatur-samband, i vilket tiden for upphettning till det ovre temperaturomradet kan minskas till mycket kort tid. I omradet 250 till 380° G skall kontakttiden vara mind-re On 2 minuter vid sackaros eller invertsocker och kan vara sa lag som 1/10 eller nagra hundradels sekunder yid de bogre reaktionstemp eraturerna. It has now been found that sugars in aqueous solution can be converted to HMF at temperatures above about 250 ° C in high yields, in a short time, without formation in the humine of the low temperature processes and with improvements in the efficiency of HMF recovery. The invention relates to a continuous process for the conversion of sugar to HMF at temperatures from about 250 ° C to about 380 ° C and the recovery of HMF. The invention comprises a time-temperature relationship in which the time for heating to the upper temperature range can be reduced to a very short time. In the range 250 to 380 ° C, the contact time should be less than 2 minutes for sucrose or invert sugar and can be as low as 1/10 or a few hundredths of a second above the higher reaction temperatures.

Anvandningen av en katalysator Or lake nadvanclig i foreliggande forfarande, men dess anvandning Or i vissa fall fordelaktig, &Isom vid omvandlingen ay glykos eller lOsningar, som overvagande innehalla glykos, eller nar moderlutar, fran vilka storre delen av fruktosen avlagsnats vid omvandlingen till HMF, bringas att cirkulera. Den effektiva omvandlingen av sadana losningar .erfordrar mer drastiska f5rhallanden, sasom hogre temperaturer, langre kontakttider eller en katalysator, och fOr detta andamal kunna syrakatalysatorer anvandas, vilket forut angivits. Anvandningen av lavulinsyra, som visat sig vara en utmarkt katalysator, foredrages. The use of a catalyst may be useful in the present process, but its use may in some cases be advantageous, to circulate. The efficient conversion of such solutions requires more drastic conditions, such as higher temperatures, longer contact times or a catalyst, and for this purpose acid catalysts can be used, as previously indicated. The use of lavulinic acid, which has been found to be an excellent catalyst, is preferred.

Vid utforandet av forfarandet enligt uppfinningen genom anvandning ay forhallanden med vasentligt 'Ogre temperaturer, dvs. Over c:a 250° C, elimineras praktiskt taget .eller fullstandigt bildningen ay humin. Nar kontakttiderna Oro langa eller de ursprungliga sockerkoncentrationerna hoga bildas en tjara, joke humin Denna tiara Or lOslig i manga organiska losningsmedel, t. ex. furfural, etylacetat, formamid, dimetylformamid, dimetylsulfoxid, och omvandlas dessutom joke till oloslig humin ens under drastiska reaktionsfOrhallanden. I jamforelse med huminbildningen Or denna tjara utan huminets olagenheter vid drift i stor skala. I exempelvis ett reaktionskarl med rorspiraler for kontinuerlig drift belagger olosligt humin ytor och Oppningar och tapper till anordningen tamligen snabbt. Tjaran Or 0 andra sidan belt flytande vid reaktionstemperatur och uppfOr sig, sasom man 2— — kan vanta av en emulsion av ett halvviskost material i ett vattenhaltigt system. In carrying out the process according to the invention by using ay conditions with substantially Ogre temperatures, i.e. Above about 250 ° C, the formation of humine is practically eliminated or completely eliminated. When the contact times are long or the initial sugar concentrations are high, a tar, joke humin is formed. This tiara is soluble in many organic solvents, e.g. furfural, ethyl acetate, formamide, dimethylformamide, dimethylsulfoxide, and in addition the joke is converted to insoluble humine even under drastic reaction conditions. In comparison with humin formation Or this tar without humin's imperfections in large scale operation. In, for example, a reaction vessel with rudder coils for continuous operation, insoluble humin coats surfaces and openings and taps to the device fairly quickly. Tar, on the other hand, is highly liquid at reaction temperature and behaves as one might expect from an emulsion of a semi-viscous material in an aqueous system.

FOrutom namnda fOrdelar, vilka ha ytterst stor praktiskt betydelse, Oro HMF-utbytena betydligt hogre an som forut rapporterats. Raknat pt sackaros siisom utgangsmaterial ha HMF-utbyten (rOknat pt ultraviolett-absorptionsspektra, som utgOr grunden f8r ett lampligt fOrsoksforfarande) pa nastan 40 % observerats i laboratorieforsok. Dvs. man kan pa 300 g sackaros erhalla 88 g HMF vid en passage genom upphettningsanordningen, varyid icke nfigon hansyn tagits till atervinnbart socker. Detta kan jamforas med forut rapporterade 48 g. In addition to the aforementioned benefits, which have extremely great practical significance, the HMF yields are significantly higher than previously reported. Shaved on sucrose as starting material, HMF yields (calculated on ultraviolet absorption spectra, which form the basis of an appropriate test procedure) have been observed in almost laboratory experiments by almost 40%. Ie. 300 g of sucrose can be obtained in 88 g of HMF during a passage through the heating device, without any consideration being given to recoverable sugar. This can be compared with previously reported 48 g.

Vid utforandet av forfarandet enligt uppfinningen upphettas socker snabbt i vattenlosning med eller utan katalysator i flagon lamplig anordning, som ãr fOrsedd med organ for kontinuerlig passage av sockerlosningen in i anordningen och bortforande av reaktionsprodukterna, inklusive HMF. Anordningen skull i sin fullstandiga utforingsform innefatta organ for franskiljning av vattenfasen, som innehaller icke omvandlat socker och som skall cykliskt aterforas till processen, det tjarliknande materialet och HMF. In carrying out the process of the invention, sugar is rapidly heated in aqueous solution with or without catalyst in a flake lamp device, which is provided with means for continuous passage of the sugar solution into the device and removal of the reaction products, including HMF. The device, in its complete embodiment, should comprise means for separating the aqueous phase, which contain unconverted sugar and which are to be cyclically returned to the process, the tar-like material and HMF.

I vilket som heist system for utforande av reaktionen maste hansyn tagas till sambandet mellan tid och temperatur under upphettningsperioden, under reaktionen och nedkylningen. Ett ldmpligt kontinuerligt system for omvandling av socker till HMF är ett sadant, som ger snabb upphettning till reaktionstemperatur och ddrefter snabb kylning. For detta andamal finnas sadana anordningar, vilka tilllata, att processen utf6res saval vid atmosfOsstry& som vid forhojd temperatur. Speeiellt lampliga anordningar for utforande av fareliggande forfarande innefatta atminstone en pump, en upphettningsanordning, ett reaktionskirl och en tryekreduceringsventil. Det är ldmpligt att anyanda en doseringspump, sasom sadana av typ Hills-McKanna eller Milton Roy, och en mottrycks-regleringsventil av sadan typ som Annin-Hammel-Dahl eller Mason-Neilan. Reaktionskarlet innefattar lampligen en eller flera kontinuerliga rorslingor av rostfritt stal eller kolstal med shdan diameter, att det mest effektiva forhallandet av varmeoverforing till losningsvolym Ostadkommes. Mottrycks-regleringsventilen medger att reaktionsinnehdllet hdlles vid vilket lampligt Mgt tryck som heist, medan den tinker, att den vatskeformiga produkten utstrommar vid vilket Mgt tryck som heist, lampligen atmosfarstryck. Annan utrustning, som Or lamplig yid industriell drift, innefattar temperatur- och tryckregulatorer av kommersiellt tillganglig typ. In any system for carrying out the reaction, consideration must be given to the relationship between time and temperature during the heating period, during the reaction and the cooling. An exemplary continuous system for converting sugar to HMF is one that provides rapid heating to reaction temperature and then rapid cooling. For this purpose, there are such devices which allow the process to be carried out both at atmospheric pressure and at elevated temperature. Particularly suitable devices for carrying out the hazardous process comprise at least one pump, a heating device, a reaction vessel and a pressure reducing valve. It is advisable to use a dosing pump, such as the Hills-McKanna or Milton Roy type, and a back pressure control valve of the type such as Annin-Hammel-Dahl or Mason-Neilan. The reaction vessel suitably comprises one or more continuous tubes of stainless steel or carbon steel of such diameter that the most efficient ratio of heat transfer to discharge volume is achieved. The back pressure control valve allows the reaction contents to be maintained at whichever high pressure is raised, while it tinks that the liquid product flows out at which high pressure is raised, namely atmospheric pressure. Other equipment, such as Or lamplig yid industrial operation, includes temperature and pressure regulators of commercially available type.

Organet for upphettning av losningen i reaktionskarlet ar betydelsefullt vid regleringen av reaktionssambandet mellan tid och temperatur. Det dr betydelsefullt att uppnd reak tionstemperatur sa snabbt som mojligt. For detta andamal utgores ett Ott for snabb upphettning genom inblasning av overhettad anga i sockerlosningen. Angans varme plus det latenta varmet vid kondensationen Ostadkommer en. snabb hojMng av temperaturen. En. annan metod for snabb hojning av temperaturen innefattar rorslingor i reaktionskarlet, genom vilka losningen passerar och som ha mycket liten diameter och Oro utvandigt uppvarmda i en ugn pd samma satt, som upphettning i en modern hogtrycksangpanna. Andra salt, sasom elektriska, kunna Oven anvandas for upphettning av reaktionskarlet. The means for heating the solution in the reaction vessel is important in regulating the reaction relationship between time and temperature. It is important to reach the reaction temperature as quickly as possible. For this purpose, an Ott for rapid heating is provided by blowing superheated steam into the sugar solution. The heat of steam plus the latent heat of condensation does not cause a. rapid rise in temperature. One. Another method of rapidly raising the temperature involves rudder loops in the reaction vessel through which the discharge passes and which have a very small diameter and are externally heated in an oven in the same manner as heating in a modern high pressure steam boiler. Other salts, such as electric, can also be used to heat the reaction vessel.

Med hansyn till HMF:s instabilitet Or det betydelsefullt, att det kan avlagsnas ur reaktionsblandningen sh snabbt som mojligt. Delia kan goras genom kontinuerlig drift i narvaro av ett extraktionslosningsmedel, &Isom furfural, varvid den vattenhaltiga sockerlosningen och furfural pumpas genom reaktionskarlet i med- eller motstrom. Reaktionsblandningen kan behandlas pet ett antal sail, sasom extraktion, destillation, adsorption for utvinning av HMF. Det Or vanligen lampligt att extrahera I-IMF film den neutraliserade reaktionsblandningen for franskiljning av socker och andra partiellt dehydrerade kolhydrater. Extraktionslosningsmedlen kunna utgoras av i vat-ten olosliga alkoholer, ketoner, etrar, estrar och halogenerade kolvaten och deras blandningar. Det Or lampligt att anvanda furfural, eftersom den vanligen bildas i liten utstrackning i reaktionskarlet och foljaktligen maste skiljas frail HMF pa nagot satt. Den vattenhaltiga renade produkt, som erhalles yid extraktionen, kan behandlas for utvinning av losningsmedel i pavisbara mangder och cirkuleras ddrefter 'ger till reaktionskarlet efter tillsats av en lamplig katalysator. In view of HMF's instability, it is important that it can be removed from the reaction mixture as quickly as possible. Delia can be made by continuous operation in the presence of an extraction solvent, & Isom furfural, whereby the aqueous sugar solution and furfural are pumped through the reaction vessel in co- or countercurrent. The reaction mixture can be treated with a number of sails, such as extraction, distillation, adsorption to recover HMF. It is usually convenient to extract I-IMF film the neutralized reaction mixture to separate sugar and other partially dehydrated carbohydrates. The extraction solvents may be water-insoluble alcohols, ketones, ethers, esters and halogenated hydrocarbons and their mixtures. It is convenient to use furfural, since it is usually formed to a small extent in the reaction vessel and consequently must be separated from the HMF in some way. The aqueous purified product obtained by the extraction can be treated to recover solvents in detectable amounts and then circulated to the reaction vessel after the addition of a suitable catalyst.

Losningen, som inneh011er HMF, kan behandlas med aktivt kol for avlagsnande av fororeningar och darefter destilleras for utvinning av HMF. The solution, which contains HMF, can be treated with activated carbon to remove contaminants and then distilled to recover HMF.

Eftersom fruktos Or mer latt dehydratiserat till HMF On glykos, Or det fordelaktigt att vid foreliggande forfarande anvanda losningar av vdsentligen ren fruktos. Detta socker kan erhallas genom hydrolys av fruktosaner, som finnas i ti-vaxten, jordOrtskocka, eller genom separering av invertsocker i sina bestandsdelar. Av ekonomiska orsaker kan man any5.nda rorsockersaft, koncentrerad rOrsockersaft, krossad sockerrorsuppslamning, invert- eller hogkvalitetsmelass, hydrolyserat Ira eller starkelse eller ddrav erhallen melass. Sirapsmelass kan Oven anvandas. Because fructose is more easily dehydrated to HMF on glucose, it is advantageous to use solutions of substantially pure fructose in the present process. This sugar can be obtained by hydrolysis of fructosans, which are present in the ti-plant, artichoke, or by separating invert sugar into its constituents. For economic reasons, any5th cane sugar juice, concentrated cane juice, crushed sugar cane slurry, invert or high quality molasses, hydrolyzed Ira or starch or ddrav obtained molasses. Syrup molasses can be used above.

Det har visat sig, aft nar en blandning av glykos eller sackaros och fruktos sonderdelas yid en temperatur c:a 275° C, erhallet HMF huvudsakligen harror friin fruktos och endast delvis frail glykos eller sackaros. Be Otercirkulerade sockerarterna Oro darfor huvudsakligen glykos eller sackaros. Vid behandling av — —3 sadana blandningar Sr det lampligt att anvanda mer drastiska forhallanden, inklusive anvandningen av en katalysator. It has been found that when a mixture of glucose or sucrose and fructose is subdivided at a temperature of about 275 ° C, HMF is obtained mainly free of fructose and only partially frail glucose or sucrose. Be Otercirculated sugars Oro darfor mainly glucose or sucrose. When treating - —3 such mixtures, it is advisable to use more drastic conditions, including the use of a catalyst.

Foljande exempel askadliggora forfarandet enligt uppfinningen. The following examples illustrate the process of the invention.

Exempel 1. En rorreaktor tillverkades av Ire 4,20 m langa r5r av rostfritt stal, 18 gage, nr 316, i serie och en yttre diameter av 6,2 mm och forbundna med en 9 m kylslinga. Varme tillfordes roren genom pumpning av varm olja genom en mantel. En hjalputrustning, som bestod av en tryckreduceringsventil och tryckoch temperaturregulatorer, anvandes. Example 1. A rudder reactor was made of Ire 4.20 m long tubes of stainless steel, 18 gage, no. 316, in series and an outer diameter of 6.2 mm and connected to a 9 m cooling coil. Heat is supplied to the pipes by pumping hot oil through a jacket. An auxiliary equipment, which consisted of a pressure reducing valve and pressure and temperature regulators, was used.

Vatten pumpades f8rst genom reaktionskarlet med en pump, Hills-McCanna Duplex, som är installd att ge 43 sek. kontakttid. Nar reaktionstemperaturen var 256° C, inkopplades till pumpen en 40-procentig losning av sackaros i vatten, vilken inneholl 0,04 % lavulinsyra, sa.som katalysator. En mork produkt, som inneh011 spar av tjarmaterial men ej humin, uppsamlades vid likformig hastighet under en langre tid. Water was first pumped through the reaction vessel with a pump, Hills-McCanna Duplex, which is installed to give 43 sec. contact time. When the reaction temperature was 256 ° C, a 40% solution of sucrose in water was added to the pump, which contained 0.04% lavulinic acid as catalyst. A dark product, which contained traces of tar material but not humine, was collected at a uniform rate for a long time.

Extraktion av reaktionsblandningen med etylacetat gay brun kristallin HMF vid torkning till torrhet. Utbytet var 30-31 % raknat pa sackaros. Tjarmaterialet visade samma analysvarden som HMF och kan Tara en polymer av nagot slag: Analys: Ber. for (HMF)x eller (C011603) C 57,2 %, H 4,8 %, funnet C 57,08 %, H 4,53 %. Extraction of the reaction mixture with ethyl acetate gay brown crystalline HMF on drying to dryness. The yield was 30-31% calculated on sucrose. The tar material showed the same analysis value as HMF and can Tara a polymer of some kind: Analysis: Ber. for (HMF) x or (CO11603) C 57.2%, H 4.8%, found C 57.08%, H 4.53%.

Exempel 2. De i exempel 2 angivna anordningarna och forhallandena anvandes i detta exempel, i vilket furfural insprutades i systemet omedelbart efter reaktionszonen (upphettningszonen). Detta forhindrade avskiljning av tjara Iran reaktionsblandningen i reaktionsroren. Vid kylning franskiljdes furfuralskiktet och behandlades for utvinning av HMF. Hogre utbyten av vatskeformig produkt, som omedelbart kristalliserade vid kylning till 15° C, erhollos. Example 2. The devices and conditions set forth in Example 2 were used in this example, in which furfural was injected into the system immediately after the reaction zone (heating zone). This prevented the separation of the tar Iran reaction mixture in the reaction tubes. Upon cooling, the furfural layer was separated and treated to recover HMF. Higher yields of liquid product, which immediately crystallized on cooling to 15 ° C, recovered.

Furfural valdes sasom losningsmedel pa grund av sin speciellt lampliga fordelningskoefficient for HMF i vatten. Metoximetyloch etoximetylfurfural kunna aven anvandas for detta andamal. Furfural was chosen as the solvent because of its particularly suitable partition coefficient for HMF in water. Methoxymethylox ethoxymethylfurfural can also be used for this purpose.

Exemp el 3. Reaktionsanordningen beskrivs i exempel 2. En losning av 35 % sackaros i vatten plus 0,04 % lavulinsyrakatalysator pumpades genom reaktionsslingorna. Vid 280 —285° C och vid en kontakttid av c:a 30 sek. blev reaktionsprodukten en brun losning, nastan fri frAn olosliga tjaror. Nar den filtrerade reaktionsblandningen provades (med UV-absorptionsspektra), visade det sig, att 62 % av sockret omvandlats till HMF. Example 3. The reaction apparatus is described in Example 2. A solution of 35% sucrose in water plus 0.04% lavulinic acid catalyst was pumped through the reaction loops. At 280-285 ° C and at a contact time of about 30 sec. the reaction product became a brown solution, almost free of insoluble tar. When the filtered reaction mixture was tested (with UV absorption spectra), it was found that 62% of the sugar was converted to HMF.

HMF utvanns latt frail reaktionsblandningen genom kontakt med flera volymer etyleter. Losningsmedlet avdunstades och aterstoden destillerades i vakuum, varvid erholls HMF av god kvalitet. Dvs. produkten kristalliserade fullstandigt vid kylning och visade en smaltpunkt av 30° C. HMF was easily recovered from the reaction mixture by contact with several volumes of ethyl ether. The solvent was evaporated and the residue was distilled in vacuo to give good quality HMF. Ie. the product crystallized completely on cooling and showed a melting point of 30 ° C.

Exempel 4. En losning av 6,8 kg sackaros framstalldes i 13600 ml vatten och nagon sur katalysator tillsattes ej. Denna losning pumpades kontinuerligt genom den i exempel 2 beskrivna rorreaktorn. Oljetemperaturen i reaktorn var 260-265° C och kontakttiden var 40 sek. Example 4. A solution of 6.8 kg of sucrose was prepared in 13600 ml of water and no acid catalyst was added. This solution was continuously pumped through the tube reactor described in Example 2. The oil temperature in the reactor was 260-265 ° C and the contact time was 40 sec.

Det morka utfRidet fran reaktorn kyldes snabbt i en iskondensor och den framstallda mangden HMF var 38 % av det teoretiska, sasom efter lamplig spadning visades med UVanalys. HMF extraherades och isolerades pa redan beskrivet salt. The dark effluent from the reactor was rapidly cooled in an ice condenser and the amount of HMF produced was 38% of theory, as shown by UV analysis after light spasm. HMF was extracted and isolated on the salt already described.

Claims

Patent claim:

Process for the conversion of sugars, such as glucose, fructose, invert sugar, fructosans, sucrose, hydrolysed starch and starch, to 5-hydroxymethyl-furfural, characterized in that an aqueous solution of the sugar is heated to a temperature above about 250 ° C. ° C for a maximum of 2 minutes to give 5-hydroxymethylfurfural in Mgt yield, the starting materials being continuously fed into a reaction zone and the resulting final product being continuously removed.

2. A process according to claim 1, characterized in that a catalyst is added to the sugar solution in an organic acid, & Isom lavulinic acid.

3. A process according to claim 1 or 2, characterized in that the conversion reaction is carried out in the presence of a 5-hydroxymethyl-furfural solvent for rapid removal of the reacted liquid from the 5-hydroxymethylfurfural Iran.

4. A method according to claim 3, characterized in that furfural is used as a lubricant.

Procedure according to any of the patent claims. 1-4, may indicate that an aqueous solution of unconverted sugar is separated from the reaction products and recycled for conversion.

6. A process according to any one of claims 1-5, characterized in that a paralysis comprising a mixture of glucose and fructose and a catalyst is treated, wherein the fructose is selectively converted to 5-hydroxymethyl-furfural, and the solution of unconverted sacs, which for the most part consists of glucose, is atherfores.

7. A process according to any one of claims 1-6, characterized in that the temperature is kept below about 380 ° C and that furfural is added after the conversion of the sugar. Request Publications: U.S. Patent Nos. 2,750,394. Stockholm 1962. Royal. Poktr. P. A. Norstedt & S6ner. 020089