CONTINUOUS PROCESS FOR PRODUCING METHYL GLUCOSIDES FROM STARCH

Abstract: The present invention is directed to a continuous process for producing hydrocarbyl aldosides. i.e., alkyl aldosides, from carbohydrates and more particularly mixed alkyl glycosides from starch by direct alcoholysis. A carbohydrate, such as starch, is slurred in an alcohol and passed through a heated, confined zone under pressure and other particular conditions in the presence of an acid catalyst to form a mixed alkyl aldoside. According to a preferred embodiment, the converted carbohydrate/alcohol slurry is rapidly cooled after alcoholysis and before recovery of the alkyl aldoside or aldosides. According to another preferred embodiment at least one alkyl aldoside is separated from the resultant alkyl aldoside mixture and the resultant mother liquor is recycled to carbohydrate/alcohol feed slurry. When using starch as car­ bohydrate and methanol as alcohol, this embodiment optim­ izes methyl-alpha-D-ghucopyranoside production.

Description: SPECIFICATION CONTINUOUS PROCESS FOR PRODUCING HYDROCARBYL ALDOSIDES FROM CARBOHYDRATES Alkyl aldosides have been used as an intermediate products in the menufacture of various chemicals, such as surfactants, glycoside polyols, etc. Because these alkyl aldosides are primarily used to synthesize other chemical products, the aldoside purity becomes a very important factor affecting its ultimate usefulness. Alpha sethyl-flglucoside, an alkyl aldo- side, As a particularly useful intermediate, provided it could be inexpensively and expeditiously manufactured in a relatively pure form from inexpensive raw materials. Alpha methyl glucosides are typically manufactured by the reaction alcoholysis of a monosaccharide (e.g. dextrose) with methanol in a batch process. The reaction product is comprised primarily of four alkyl mon saccharide isomers (methyl-alpha-D-glucopyranoside; methyl-beta-D-glucopyranoside; methyl-alpha-D-glucofuranoside and methyl-beta-D-glucorurano- side). These isomers have different temperatures of crystallization. This facilitates the separation and recovery of nrthyl-alpha-D-glucopyranoside frequently referred to as methyl-alpha-D-glucoside) therefrom. This process yields a purer methyl-alpha-D-glucopyranoside product when corrared to glucosides prepared from polysaccharides. The alcoholysls of starch typically produces a crude alkyl glycoside mixture which, in addition to the methyl-alpha-D-glucopyranoside, also contains a variety of other contaminante. The manufacture of sethyl- Dglucoside directly from starch has not been practical because Or numerous pro- cessing and production difficulties (e.g. excessive and undesirable byproduct contamination, prolonged and tedious refining steps required to produce a relatively pure product, costly capital equipment investments, incomplete conversion of the raw naterials into the desired end-product, low yields, etc.). The use of starch as a starting raw material to continously manufacture and recover methyl-alpha-D-glucopyranoside from crude coside mixtures would be highly desirable. PRIOR AW Numerous methods for producing alkyl glucosides have been prior posed. U.S. Patent No. 2,276,621 discloses batch alcoholysis of starch. By concentrating the crude reaction product, methyl-alpha-D-glucoside may be selectively crystallized therefrom. The resultant mother liquor (obtained after crystallization of the alpha methyl glucoside therefrom) is described as a disequilibrate solution of methyl glucoside deficient in methyl alpha glucoside. By adding starch, methanol and catalyst thereto, the mother liquor may be recycled and reused in a batch reaction. It is indicated that this operation may be repeated until the accumulation of by-product is so great as to render further conversion with the original mother liquor impractical. U.S. Patent No. 2,606,186 by Dean et al. discloses the use of a column reactor containing a cat ironic exchange resin to catalyze and convert anhydrous dextrose and methanol into methyl glucoside at a reaction tempera- ture less than about 1000C. In U.S. Patent No. 3,296,245 crude alkyl glycoside mixtures are reportedly produced by the batch alcoholysis of starch in the presence of a Lends acid catalyst at an elevated temperature and pressure. The methyl alpha glucoside is recovered from the crude mixture and the mother liquor reportedly may be recycled and reused in the batch reactor several tires (2-5 times). A patent by Molotsky et al. (U.S. Patent No. 3,565,885) discloses a batch process for preparing an alkali color stable glucoside. Undesirable byroduct contamination is reduced by using dextrose as a starting material. An ion-exchange treatment is used tp remove reaction product inpurities. After recovering the glucoside, the ion-exchanged mother liquor reportedly may be recycled. Garefully controlled conditions (e.g. dextrose starting material, temperature, pH and pressure control, ion exchange, additional refining, etc.) are required to produce a relatively pure product. Gibbons et al. (U.S. Patent No. 3,450,690) is similarly concerned with the removal of alkali labile, color producing bodies from crude alkyl glycosides. In Example 1, a crude alkyl glycoside is obtained by passing an anhydrous dextrose and methanol solution through a colurm packed with a Strong cationic resin (e.g. sulfonated crosslinked polystyrene in acid form). The reaction is conducted at a relatively low reaction temperature to protect the resin. A clear alkyl glycoside solution is obtained by reflexing the crude alkyl glycoside reaction product with a base (e.g. 69 C., 30 minutes, pH 12) followed by its cooling and filtration. me alkali treatment reportedly converts the undesirable contaminants (non-glucosides) into a form which can be readily separated and removed (e.g. filtration, chemical treatment, ion exchange treatment, etc.) without causing the alkyl glucosides to crystallize therefrom. More recently, U.S. Patent No. 3,375,243 (Nevin et al.) discloses a method of n methyl glucosides from starch using p-toluene sulfonic acid catalyst in a pressure reactor (e.g. 1650C. - 275 psig). Approximately 85-90% of the starch is reported as being converted to methyl glucoside. Panusch et al. in U.S. Patent No. 3,928,318 disclose an anhydrous batch process for making methyl glucoside by the alcoholysis of glucose. Crystalline alpha-methyl glucoside is recovered from the reaction mixture and the mother liquor is recycled and reused in the batch reactor. A continuous method for preparing polyol glucosides is disclosed by Both et al. (U.S. Patent No. 3,346,558). In the Roth et al. patent, a fluid feed mixture of starch, polyol and acid catalyst is converted to a polyol glycoside by mechanically working and shearing the mixture under elevated tenperatures and pressures. SUMMARY OF THE INVENTION According to the present invention there is provided a process for directly converting mo monohydric alcohols and carbohydrates into crude aldosides, said process comprising the steps of: (a) providing to a tubular reaction zone under a positive fluid pressure, a fluid slurry comprised of carbohydrate, mono hydric alcohol and acid catalyst in an amount suf ficient to permit chemical conversion of the fluid slurry into a fluid hydrocarbyl aldoside mixture; ; (b) heating said feed slurry within said continuous tubular reaction zone to an elevated temperature for a period of time sufficient to convert said fluid slurry into a fluid hydrocarbyl aldoside mixture comprised of hydrocarbyl-alpha aldoside andhydroarbyl-beta aidoside while continuously providing additional feed slurry to said tubular reaction zone under a positive fluid pressure to force the converted fluid aldoside mixture through said tubular reaction zone; and (c) recovering from said hydrocarbyl aldoside mixture at least one hydrocarbyl aldoside. According to a preferred embodiment of the present invention, the converted fluid hydrocarbyl aldoside mixture from (b) above is rapidly cooled before recovery of the hydrocarbyl aldoside or aldoside mixture. According to another preferred embodiment of the present process, the fluid hydrocarbyl aldoside mixture from (b) above is partitioned into a mother liquor portion and aldoside portion by selectively recovering at least one hydrocarbyl aldoside from the fluid hydro carbyl aldoside mixture, whereafter the mother liquor is recycled to the feed slurry of step (a) above. amler equipment with less necessary capital investment can be effectively used to continuously produce relatively large quantities of a relatively pure aldoside. Because the total reaction cycle takes less tine, the process is sore energy efficient. There is no separate "heat-up", which saves considerable energy. The total reaetionWrbe be completed within 6-15 minutes. present method is capable of producing a glycoside mixture at high glucoside purity. The continuous reaction conditions assure that a product of sore uniform, acceptable quality will be obtained, since the reagents are thoroughly mixed, and each part of the starch slurry is sub Jected to substantially the same conditions of temperature and pressure. The key to the success for producing a sore pure methylwalpha-D-glucopyrano- side at a higher total yield is in the fact that the alcohol-slurried starch is heated very quickly to obtain the catalyzed alconolysis reaction to nake the desired product. Polymerization of the glucosides to the less desirable polyglycosides is avoided. In addition, undesirable side reactions, which lower yields and give more color bodies, are avoided by the subject method. The composition of the resulting mixed glycosides is surprisingly uniform and consistent in properties. By selectively separating and recovering at least one glucoside fran the glycoside mixture and repeatedly or continuously recycling the rather liquor to the reactor, the reactants can be more effectively utilized to achieve optimum production of the desired end product. DETAILED DESCRIPTION OF THE INVENTION This invention relates to a continuous alcoholysis process for making added aldosides from carwdrates and, according to a preferred embodiment, selectively removing at least one aldoside therefrom. In the present process an aldoside mixture is produced by sllurying a carbohydrate in an alcohol containing media and passing it though a confined zone under fluid pressure at an elevated temperature in the presence of an acid catalyst. Mixed hydrocarbyl aldosides containing a high proportion of sonoaldosides (l.e. alpha- and beta-) may be prepared from monosaccharides axWcr polysacoharides by thls process. the resultant aldoside mixture may then be partitioned into a mother liquor portion and glucoside portion by selectively partitioning at least one hydrocarbyl aldoside from the crude aldoside mixture. The partitioned aldoside is recovered therefrom and the mother liquor is recycled to the converter. In the present process, the feed slurry is continuously provided to a tubular reaction zone under a positlve fluid pressure. Although starch is the preferred carbohydrate reactant the feed slurry reactants may broadly encompass sonohydric alcohols and carbohydrates. Monosaccha- rides (e.g. dextrose, etc.), polysaocheride materials (e.g. hemi-cellulose, insulin, dextran, xylan and the like). and/or mixtures (e.g. corn syrup solids) thereof may be "alcoholized" to aldosides the presence of a catalyst to form the corresponding aldosidesunder the appropriate temperatures and pressures. Illustrative monohydric alcohols include the aliphatic all hols (saturated or unsatureted) such as the C1-C18 alkanols and C3-C alkenols. Exemplary aliphatic monohydric alcohols include methanol, ethanol, propanol allyl alcohol, butanol, alcohols having five to eighteen carbon atoms, their isomers, derivatives and mixtures thereof. The process is particularly well adapted for the alcoholysis of starch with the C1-C4 monohydric alocohols especially methanol. The mono hydric alcohol Serves as a reactant and as a liquid dispersant through out the entire process. Accordingly, the alcohol functions as a dis persant for the chemical reactants and as a solvent for the reaction prior ducts fran which the desired end product may be effectively crystallized The anrxtnt of monohydric alcohol used in the process should be sufficient t6 maintain the reactor feed slurry and reaction product in a fluidized state. A molar excess of alcohol is typically needed for this purpose. When starch is utilized, the monohydric alcohol to starch molar ratio will most generally range from about 15:1 to about 6.5:1. In the alcoholysis of starch with methanol, the starting feed slurry will typically contain from about 30% to about 50% by weight starch and from 50% to about 70% by weight methanol. The alcoholysis of the carbohydrate is conducted in the presence of sufficient acid catalyst to catalyze the reactants to an alkyl aldoside mixture. Although the catalyst concentration may vary considerably, a catalyst concentration from about 0.001 to about 0.1 mole catalyst per mole of starch may typically be used. Illustrative acid catalysts therefore include hydrochloric acid, sulfuric acid, phosphoric acid, crtho-, seta-, and para-toluene-sulfonic acid, benzene-sulfonic acid, various substituted benzene-sulfonic acids, such as orUbo-, meta-, and para-bromo- benzene-sulfonic acids, ethane-sulfonic acid and the like, as well as combinatlons thereof. When starch is used as a starting reactant, the preferred catalyst concentration is advantageously at least 0.004 mole catalyst per starch mole and preferably in an amount raing from about 0.005 to about 0.01 mole of catalyst for each mole of starch. As previously mentioned, the chemical reaction is appropriately conducted within a tubular reaction zone suitably equipped with heating means sufficient to convert the reactants into the desired aldoside mixture. Apparatus of the type disclosed in U.S. Patent Nos. 2,735,792 and 3,617,383 may be appropriately adapted to the present process. The continuous coil of the reactor may be of any convenient length (e.g. 50-5000 ft.) and inner diameter (e.g. about .18 inch to about 6 inches). The chemical reaction should be conducted within the reactor for a period of time and at a temperature sufficient to convert the reactants into the desired aldoside mixture. Although these tençerature-time conditions can vary considerably, the temperature will generally range between about 1000C. to about 4000C. for a period of time ranging from about 2 to about 150 minutes. Prolonged exposure of the reactants to elevated temperatures which result in charring or excessive formation of nonglucoside by-products should be avoided. Conversely, low temper atures can lead to plugging or fouling of the reactor and incomplete glycoside conversion. If the reactants are comprised of starch and methanol, the reactants will advantageously have a residence within the reactor of less than about 30 minutes (e.g. 2-30) and preferably less than about 20 minutes (e.g. about 520 minutes). The reaction will usually be conducted at a temperature greater than 1600C. (e.g. about 1600C. to about 1800C.) and preferably at a tenperature of at least 1650C The feed slunk and reaction products are forced through the reaction zone under a positive fluid pressure. Means for providing the feed slurry to the reactor under positive pressure (e.g. pumps, etc.) at a controlled pressure and rate (e.g. valves, pressure regulators, etc.) may be suitably used for this purpose. Means to automatically measure and setter the flow of reactants through the reactor and to replenish the reactants in the correct proportions in the feed pressure vessel may also be appropriately adapted to the process. A second feed pressure vessel with valves may be provided in a parallel line so that the reactants may be alternately fed to the continuous coil reactor from either pressure feed vessel as desired. Under the proper processing conditions (e.g. temperature, pressure, catalyst, reaction media and time, etc.), the composition of the reaction mixture will remain relatively constant. The consistency and reproducibility of the equilibrated glycoside mixture via the present process provides a means whereby the reaction by-products may be effectively recycled and used to optimize the production of the desired glycoside reaction product. The chemical reactivity and type of reactants used to prepare the aldosides will affect the relative proportion of mono-, di-, triand higher aldosides, including their isomeric.forms, in the aldoside mixture. As flrrther illustrated by the examples, modification of the reaction conditions may also alter these proportions. Under at given set of processing conditions, a relatively constant proportion of aldo side: carponents will be produced for any given reactant system. AccordingRy, any given reaction system can be satisfactorily and uniformly reproduced by controlling the processing conditions under which the aldoside mixtures have been prepared. When starch and methanol are subjected to the alcoholysis process of this invention, the equilibrated glycoside mixture will generally yield methyl-Dglucooyronosides (alpha- and beta- fonris) as the major reaction products (solid weight basis). The alpha isomer is typically the most predominant reaction product (i.e. its weight exceeds all other glycosides) of the mixture. For most operations, the methyl D-glucopyranosides content (alpha- and beta- forms) will typically range from about 65% to about 90% by weight of the total non-volatile solids of the glycoside mixture. The proportion of alpha-isomer can be altered by changing the reaction conditions. The alpha isomer content will generally range from greater than 25% to less than about 75; by weight of the total non-volatile mixture solids. Because of recovery considerations, it is generally desirable to maximize the alpha-glucopyranoside isomer yield. Methyl-alpha-Dglucopyranoside recovery is promoted by operating under reaction conditions which yield a glycoside mixture containing at least 40% by weight methyl-alpha-D-glucopyranoside (solids basis), It is expedient and advantageous to normally produce a g3coside mixture which contains at least 45% by weight alpha isomer with an amount ranging from about 45% to 60% being the most typical. operational range. When the methyl-alpha-D-glucopyanoside is the predominant reaction product, the methyl-beta-D-glucopyranoside is typically the seccnd most prevalent product of the reaction mixture. It win usually range from about 40% to about 60Z of the alpha isomer weight with an amount between about 20% to about 35S by weight of the total glycoside mix- ture solids being most typical thereof. Under such conditions, the remaining glucosidic isomers (i.e. methyl-alpha-D-glucofuranoside and methyl-beta-D-glucofuranoside) will normally constitute a considerably smaller proportion (less than 20% and preferably less than 15S) of the total glycoside mixture solids weight. Preferably the total rurano- side (alpha- and beta-) content of the glycoside mixture will be less than 10% by weight with an amount ranging from about 5Z to about 8% being most typical thereof. Other than the glucopyranosides, the methyl-D-maltosides (alphaand beta- forms)willnormally comprise the major constituent (weight basis) of the remaining solids in the glycoside mixture. These diglyc sides will generally constitute less than 202 by weight of the total glycoside mixture solids with an amount ranging from about 8% to about 15Z by weight being most typical thereof. When the process conditions are adjusted to optimize alpha-glucopyranoside production, the triglycosides /e.g. methyl-alpha-D-maltotrioside and methyl-beta-D naltotrioside) will usually ccnprise a smaller proportion (e.g. less than 5fi) of the glycoside mixture with levels ranging from about 1% to 4% being most common. Under such process conditions, the oligosides (i.e. > D.P.3 glycosides) will constitute but a very smell amount of the glycoside mixture weight (e.g. less than15 and most typically less than 0.5% As evident from the relatively small proportion of tri and oligosides, the process conditions herein effectively produce gluco sides and inhibit their repolymerisation into these polyglucosides. Under the appropriate processing conditions, the methyl-alpha- D-glucopyranoside content of the glycoside mixture (on a dry weight ratio basis) may be designed to exceed the methyl-beta-D-glucopyrarxF side by at least a 3:2 weight ratio (e.g. about 1.53 times greater), the methyl-alpha-D-maltoside and methyl-beta-Dmaltoside content by at least 3:1 (e.g. between 3:1 and about 6:1), the methyl-alpha-N maltotrioside and methyl-beta-Dnaltotrioside content by at least 10:1 (e.g. between 11:1 and about 50:1), the methyl-alpha-Nglucofuranoside and methyl-beta-D-glucofuranoside by at least 6:1 (e.g. 6:1 to about 10:1) and the higher methyl-alpha- and beta-oligosides (i.e. > D.P.3) by at least 35:1 (e.g. between 38:1 to about 740:1). Other non-glyco- side reaction by-products such as dextrose will typically comprise less than about 5S of the total reaction product dry solids weight. As further illustrated, glycoside mixtures comprising (weight percent basis) from about 45.67-51.54 methyl-alpha-D-glucopyranoside; 25.88-27.96 methyl-beta-D-glucopyrano side; 8.67-14.73; methyl-alpha-D-maltoside and methyl-beta-D-malto side; 1.04-3.92 methyl-alpha-Daltotrioside and methyl-beta-D-malto- trioside; 0.07-1.19 higher methyl-alpha- and beta-oligosides; 5. 7.54 methyl-alpha-D-glucofuranoside and methyl-beta-D-glucofuranoside; and 1.02-3.34 dextrose are easily obtainable by the present process. She present invention broadly applies to the alcoholysis of carbohydrates with monohydric alcohols to produce an aldoside mixture and partitioning at least one aldoside thereform. Crude glycoside mixtures produced by the present method provide a particularly suitable substrate for selectively removing at least one hydrocarbyl glucoside and the recycllng of the balance of the glycoside mixture to the tubular reactor as feed stock. A variety of conventlonal techniques for partitioning and recovering hydrocarbyl glucosides from glycoside mixtures may be used (e.g. chromatographic, membrane separation, diffusion, crystallization, etc.), crystallization is the preferred method of product separation and recovery. The most suitable conditions for crystallizing and recovering at least one aldoside frail the resultant aldoside mixture will depend uçXxn the crystallization characteristics (e.g. saturation, concentration, crystallizing temperature, etc.) for the particular aldoside crystal toe to be recovered from the aldoside mixture. The most appropriate crystallization conditions may be ascertained by means of conventional supersaturation and crystallization temperature curves. Such curves may be effectively utilized to cptindze crystal yields for batch or continuous crystallization (e.g. progressively coneentrating the mixture and gradationally cooling to maintain optimmum critical saturation concentration for continuous crystal recovery) operations. The process is particularly adapted for the crystallisa- tion and recovery of methyl-alpha-Dgluccpyranoside because of its lower solubility in alcohols. This will provide a mother liquor rich in the remaining components of the glycoside mixture. The return of the mother liquor to the methanolysis reaction, in which more starch and methanol are added, results in substantial quantitative conversion of the starch to methyl-alpha-D-glucopyranoside. A particularly unique attribute of the present invention is the ability to produce an eouilibrated reaction product containing a high proportion of methyl-alpha-D-glucopyranoside which can be easily removed therefrom by crystallization. This will provide a mother liquor which contains an excess of the reaction products other than methyl alpha-D-glucopyranoside. When this mol mother liquor is recycled to the reactor, the reaction media contains its complement of reaction pry ducts other than methyl-alpha-D-glucopyranoside. As a result of this deficiency, the chemical reaction will be driven almost entirely towards the production of methyl-alpha-D-glucopyranoside since essentially all of the remaining by-products for the equilibrated chemical reaction are already present in the recycled mother liquor. Although the methyl-alpha-DLglueopyranoside concentration obtained fsom the reaction is sufficient to permit its direct crystallization from the glycoside mixture upon cooling, more effective methyl alpha-flglucooyranoside crystallization and recovery my be accomplished by concentrating the glycoside mixture. This will increase the alpha-D-glucopyranoside supersaturation temperature and reduce the overall cooling requirements for satisfactory crystallization In the present process, it is advantageous to immediately flashcool, without solidiifying the glycoside mixture as it issues from the reactor. Flash-cooling facilitates hydrocarbyl-alpha-D-glucoside crystal lization by increasing the glycoside solids concentration. In addition to concentrating the glycoside mixture, flash-cooling will terminate the chemical reaction and alleviate undesirable by-product production repolymerization. If desired, the volatiles of the flash-cooling (methanol and water) may be recovered by conventional means and recycled into the process. The amount of methyl-alpha-D-glucopyranoside produced with each pass through the converter will be inversely proportional to its level in the mother liquor. It is therefore advantageous to remove as much methyl-alpha-D-glucopyranoside as commercially feasible from the glycoside mixture before recycllng the mother stream to the reactor. Overall methyl-alpha-D-glucopyranoside production will be impaired if less than one-fourth of the total methyl-alpha-D-glucopyranoside within the glycoside mixture is removed before the mother liquor is recycled to the reactor. For most operations, it is advantageous to leave a minor portion (preferably about 25% to about 40fi) of the total methyl-alpha D-glucopyranoside in the mother liquor and recycle it to the reactor. In the crystallisation of methyl-alpha-D-glucopyranoside from the glycoside mixture the nOxture is cooled sufficiently to permit the glucoside to crystallize therefrom. The crystallization temperature will depend upon the methyl-alpha-Dglucopyasnoside concentration. For commercial purposes, the dry solids content of the glycoside mixture will typically be concentrated from about 40% to about 80% and preferably from about 50S to about 75%. At this concentration, methyl-alpha-D-glucopyranoside may be typically crystallized therefrom at a crystallization terperature ranging from about 50C. to about 50 C and preferably within a tem- perature ranging from about 15 C to about 350C. If desired, the crystallization temperature may be incrementally decreased to optimize crystallization of the methyl-alpha-D-glucopyrano- side from the glycoside mixture. Likewise, the solids concentration of the glycoside mixture nay be periodically adjusted to take into account the glucoside crystallized therefrom so as to permit the recovery of additional glucoside therefrom. Alternatively the glycoside mixture may be subjected to a series of crystallization steps with the mixture being concentrated between each successive batch. Similarly, the glucoside nay be continually crystallized and recovered from a glycoside mixture by progressively decreasing the crystallization temperature with or without simultaneous or intermittent concentration of the glycoside mixture. Conventional seeding techniques may also be used, if desired to expedite crystallite formation in the glycoside mixture. If more than one aldooide is to be recovered from the mixture, the least soluble aldoside component may be exhaustively crystallized followed by the crystallizaticn therefrom of the next least soluble aldoside component (e.g. see U.S. Patent No. 3,565,885). She hydrocarbyl glucoside crystallites may be recovered from the glycoside mixture by conventional recovery techniques (e.g. via filtration, centrifugation, etc). Under proper washlng and extraction techniques, the purity of the hydrocarbyl glucoside crystals will be significantly improved. Surface and non-occluded contaminants may be conveniently removed from the hydrocarbyl crystals by conventional cold washing techniques. Washing the crystals with monohydric alcohol at a cool temperature (e.g. 15 C. to 250C.) is generally sufficient to remove these contaminants therefrom and to provide the desired purified product. For example, washed crystalline methyl-alpha-D-glucopyramide containing less than 1% methyl-beta-D-glucopyranoside, less than 2S and preferably less than 1.5S maltosides, less than 0.5% oligosides, less than 1% dextrose (preferably less than 0,4%), essentially free from furanosides and less than about 0.5S of other impurities may be prepared. Ab maintain an adequate recoverable yield of aldoside in a continuous operation, it is generally necessary to fortify the mother liquor with reactants and catalyst. After the initial run, the mother liquor will typically contain its full complement of reaction by-pro- ducts (i.e. those not recovered from the mother liquor) except for those minor impurities removed from the aldoside mixture during the partiticning step. Satisfactory conversion and recovery of the desired aldoside from the aldoside mixture will generally necessitate addi tional carbohydrate to be added to the recycled stream. The overall carbohydrate requirement for recycled feed stream is significantly. reduced because the recycled mother liquor willtypicalIy contain su:- stantially its fUIl complement of aldoside by-products. Accordingly, the use of the recycled mother liquor as a feed slurry component pro vides reaction medium whereby substantially all of the carbohydrate may be directly converted into the desired end product. When methyl-alpha D-glucopyranoside is the desired product, the amount of starch typically added to the feed slurry should advantageously be sufficient to maintain a yield of at least 40% and preferably at least 45% by weight methyl alpha-Dglucopyranoside . A portion of these yield requirements will be nasally fulfilled by the unrecovered residual methyl-alpha-D-gluco- pyranoside which is recycled with the mother liquor to the conversion zone. The e molar requirements for satisfactory conversion of other carbohydrates ray likewise be conputed on the basis of their reaction equations. In the conversion process, the mother liquor will nonnally lack a sufricient amount of monohydric alcohol to maintain a satisfactory end product yield. This deficiency will arise because of direct con version of the alcohol reactant into the recovered product and the evaporative losses which arise from concentrating the aldoside mixture to effectively crystallize and recover the methyl-alpha-'dLglucopyrano- side therefrom. The mascot of alcohol added to the recycled feed slurry should be sufficient to maintain satisfactory yields of the desired end product as well as to provide a fecd slurry having the necessary rluidity prerequisite to be processed in accordance with the process ing conditions of this invention. 'Under normal operation, a small amount of catalyst will be physically lost by the processing conditions. Small amounts of catalyst, as needed, may be accordingly added to the recycled feed allury to insure adequate conversion of the reactants into the desired conversion product. As further illustrated by the examples, crystalllne methylalpha glucoside of a purity of at least 94% and most preferably of at least 96% may be easily prepared by the present process. The , purity of. the methyl-alpha-D-glucopyranoside crystals is not adversely affected by continuous recycllng and reuse of the mother liquor. The following examples are illustrative of the invention. ELATE 1 In this example, a starch scurry was continuously converted in a continuous coil reactor (360 feet long and .305 inch internal diameter) submerged in a hot hydrogenated vegetable oil bath. The continuous reactor was continuously fed by means of a nitrogen pressurized Parr vessel. The effluent reaction productissuing from the reactor was flashcooled (under atmospheric pressure and ambient temperature) and collected in two liter graduated cylinders. Starch containing about 5S moisture was slurried in methanol at 43% solids. About 0.005 moles of p-toluene-sulfonic acid per mole AGU (annydroglucose unit) was added. The : continuous reactor was adjust- ed to provide a temperature of about 165 C. therein as the starch/acid alcohol slurry mixture passed through. The pressure control means was adjusted to obtain about ten minutes retention time in the continuous coil reactor. There was obtained a crude methyl glycoside product (after flashing to atmospheric pressure) containing 62Z solids solution in methanol. The solids analyzed as follows: 48.0% methyl-alpha-D-glucopyranoside 25,0% methyl-beta-D-glucopyranoside 6.0% methyl-alpha-D-glucofuranoside and methyl beta-D-glucofuranoside 13.5% methyl-alpha-D-maltosiderand methyl-beta-D-maltoside 3.0% methyl-alpha-D-maltotrioside and methyl-beta-D-maltotrioside 0.3Z higher methyl-alpha- and beta-oligosides 2.0% dextrose 1.5% unidentified corrponent (possibly a 5-earbon reducing sugar) 0.7% residual catalyst and/or moisture 100.0% EXAMPLE 22 The following results were obtained when the reaction was performed using decreasing methanol/starch molar ratio. The methanol/starch ratio was decreased in seven steps from 15:1 to 6.8:1, while maintaining all other variables constant. All runs were at 172 C., 16 minutes reten- tion tire, using 0.01 mole of para-toluene sulfonic acid catalyst per mole of anhydroglucose unit (AGU) based on starch adjusted to 5Z moisture. As set forth below, it. can be seen that this change reduced the percen- tage of methyl-alpha and beta- gucosides in the crude product while the levels of dextrose and polyglycosides increased. See Table I below: TABLE I EFFECT OF tECRE METHANOL:STARCH RATIO OF PRODUCT COMPOSITION Sample A B C D E F G Moles Methanol/Mole AGU 15.0 12.5 10.7 9.4 8.3 7.5 6.8 Product Composition: : methyl-alpha-D glucopyranoside, % 51.54 51.46 50.27 51.01 48.72 47.38 45.67 methyl-beta-D glucopyranoside, % 27.96 27.74 27.82 27.11 26.37 26.17 25.88 methyl-alpha-D maltoside and methyl-beta-D maltoniside, % 8,67 9.45 10.54 11.24 12.53 13.37 14.17 methyl-alpha-D maltotrioside and methyl-beta-D maltotrioside, % 1.04 1.01 1.36 1.62 2.26 2.51 3.10 higher methyl-alpha and beta-oligosides, % 0.08 0.05 0.06 0.09 0.10 0.13 0.18 duct color at the 0.005 mole catalyst level was significantly lighter than at higher levels. The results for four samples having various levels of para-toluene sulfonic acid catalyst are set forth below: TABLE II Effect of Catalyst Level on Product Composition sample H* I J . K Moles Catalyst/Mole AGU 0.010 0.0066 0.0050 0.0034 Product Composition: methyl-alpha-D-glucopyranoside, S 45.67 46.31 46.64 methyl-beta-D-glucopyranoside, % 25.88 25.62 25.75 methyl-alpha-D-maltoside and 14.17 14.40 14.31 Not methyl-beta-D-maltoside, % methyl-alpha-D-maltotrioside and methyl-beta-D-maltotrioside, S 3.10 3.18 2.93 Analyzed higher methyl alpha- and beta- 0.18 0.16 0.12 oligosides, % methyl-alphaDglucofaanoside and methyl-beta-D-glucofuranoside, % 6.78 6.96 6.87 Dextrose, % 2.33 1.70 1.67 Other and unidentified, 5 1.88 1.66 1.70 Color Dk.Brown Brown Cream Sane as Sample G, Table I. (All runs at 6.8:1 moles methanol:mole AGU, 172 C., 15-16 minutes reten tion tine, PFP starch at 5.0% moisture.) Sample K was not analyzed because it plunged the reactor. It appears that a different reactor design may be required for lower catalyst TABLE I (cont. A B C p E F a methyl-alpha-D glucofuranoside and methyl-beta-D glucofuranoside, % 7.54 7.28 6.66 6.57 6.73 6.78 Dextrose, % 1.02 1.16 1.46 1.65 1.77 2.01 2.33 Other and unident liied, % 2.15 1.84 1.66 1.62 1.67 1.70 1.88 (All runs at 172 C., 16 minutes retention time, 0.01 mole para-toluene sulfonic acid/mole AGU on PFP starch adJusted to 5S moisture.) In the above Table I, it can be seen that Sample A product composition gave a yield of 79.5S methyl-alpha-D-glucopyranoside and-methyl-beta D-glucopyranoside, and only 10.81S of polyglycosides and dextrose. Sample D produced 77.12 % methyl-alpha-D-glucopyranoside and methyl-beta D-glucopyranoside, while Sample G produced only 71.55% of the glucosides. At the same time, the percentages of polyglycosides and dextrose increased as the methanol:starch ratio decreased. The cost of removal of excess methanol must be balanced against the slightly increased yield of glucodides EXAMPLE 3 Tests were made to determine the effect of reducing the amount of catalyst used. Para-toluene sulfonic acid was reduced from 0.01 to 0.005 mole/mole AGU (anhycroglucose unit) in a series of tests. There was no observable change in the chemical cooposition of the product. However, at 0.0034 mole catalyst/mole AGU, the reactor plugged. Pro- levels. The preferred amount of catalyst using the present reactor is about 0.0050 mole/catalyst/mole AGU, although 0.004 mole catalyst/mole AGU was used in one comparison in Example 4, below. EXAMPLE 4 Tests were also done to determine the effect of tenperature on the resulting composition Temperature of the reaction mixture was changed in four steps from 1780C. to 1610C. with the results reported below. TABLE III Effect of Reaction Temperature on Product Composition Sample L M N O Product Composition methyl-alpha-D-glucopyranoside, % 45.79 45.89 47.29 46.61 methyl-beta-D-glucopyranoside, S 25.96 25.80 26.21 25.92 methyl-alpha-D-maltoside and methyl-beta-D-maltoside, 5 13.70 14.53 13.87 14.14 methyl-alpha-D-maltotriosode and methyl-beta-D-maltotrioside, S 2.97 3.08 2.89 3.49 higher methyl-alpha- and beta oligosides, S 0.23 0.29 0.28 1.19 methyl-alpha-D-glucofuranoside and methyl-beta-D-glucoranoside, 5 6.97 6.42 6.15 5.78 Dextrose. 5 2.08 1.91 1.66 1.51 Other and unidentified, 5 2.29 2.08 1,64 1.35 Reaction Temp., C. 178 172 166 161 color Brown Dark Tan Tan Cream (All runs at 6:8:1 moles methanol mole AGU, 0.005 mole p-TSA/mole, AGU, 16 minutes retention time on PFP starch at 5.05 moisture.) In another experiment, the reaction temperature was increased to 181 C. while decreasing the catalyst 0.004 mole/mole AGU. Product compositlon showed only minor changes in almost all components when compared to a run at 172 C where catalyst level was 0.005 mole/mole AGU. Color was significantly poorer, however. As can be seen above in Table III, product color inproves form bum to cream. The chemical composition changed very little with the only significant increase occurring in the higher glycosides at the lowest temperature. EXAMPLE 5 The combined effect of reducing the reaction temperature to 152 C. while increasing the retention time to 26 minutes was compared to a run at 17 172 C. and 16 minutes retention time. The results are reported below: TABLE IV Effect of Low Temperature and Increased retention Time on Composition Sample P Q Product Composltion: : methyl-alpha-D-glucopyranoside, % 46.31 47.65 methyl-beta-D-glucopyranoside, S 25.62 26.20 methyl-alpha-D-meltoside and methyl-beta-D-maltoside, b 14.40 14.47 methyl-alpha-Dmaltotrioside and methyl-beta-D-maltotrioside, Z 3.18 3. oIl higher nethyl-alpha- and beta-oligosides, % 0.16 0.42 methyl-alpha-D-glucofuranoside and methyl-beta-D-glucofuranoside, % 6.96 5.01 Dextrose, % 1.70 1.79 Other and unidentified, % 1.66 1.42 Reaction Temperature, C 172 152 Retention time, min. 16 26 "Same as Sample I, Table II. (Both runs at 6:8:1 mole methanol/mole AGU, 5% moisture on feed starch, 0.0066 mole p-TSA/Mole/AGU.) It can be see in Table IV that the combination of lower reaction temper- ature and longer retention time did not avoid the trend on increase in higher oligosides and dextrose observed above in Table III. The results reported in Table IV indicate that the higher temperature Or Sample P is preferred to avoid an increase of higher oligosides and dextrose, even though the amount of methyl-glucopyranoside did decrease in this comparison. EXAMPLE 6 The effect of feed starch moisture on product quality was also checked by conducting four runs at feed starch moisture levels rangine from 2% to 11%. The results are reported below: TABLE V Effect of Feed Starch Moisture on Product Composition Sample R S T U Product Ccmposition: : methyl-alpha-D-glucopyranoside, % 48.17. 45.05 45.78 48.59 methyl-beta-D-glucopyranoside, % 26.78 28.46 27.86 26.33 methyl-beta-D-maltoside and methyl-beta-D-maltoside % 12.67 13.16 12.76 11.88 methyl-beta-D-maltoside, % 12.67 13.16 12.76 11.88 methyl-alpha-D-maltotrioside and methyl-beta-D-maltotrioside, % 2.49 2.40 2.23 2.09 higher nethyl-alpha-; ;and beta oligosides, % 0.07 0.09 0.07 0.15 methyl-alpha-D-glucoferanoside and methyl-beta-D-glucofuranoside % - 7.32 7.00 6.48 methyl-beta-D-glucofuranoside, % - 7.32 7.00 6. 48 Dextrose, % 1.07 1.68 2.22 2.74 Other and unidentified, % - 1.84 2.09 1.73 Feed starch moisture, % 2.00 5.00 8.00 11.00 (All runs at 8.3:1 moles methanol:mole AGU, 0.005 mole p-TSA/mole AGU, 14.5 minutes retention time, 1720C.).. It can be seen from the above results in Table V that the percentage or dextrose produced increases as moisture increases. Quite surprisingly, the product also becomes unexpectedly lighter. This improvement in color is opposite to the expected trend. It would be expected that higher dextrose levels would cause darker color. Starch is usually available at about 10-13% moisture, and the above results show that it is not necessary to predry the starch prior to use in the subject process. EXAMPLE 7 Tests were carried out to determine the effect of retention tines on product composition. Retention time of 16.5, 10.7 and 8.0 minutes in the reactor were compared with the results reported below: TABLE VI Sample V W X Product Composition: methyl-alpha-D-glucopyranoside, % 44.88 45.66 43.21 methyl-beta-D-glucopyranoside, % 27.68 27.58 27.54 methyl-alpha-D-maltoside and methyl-beta-D-maltoside, % 14.44 14.04 14.73 methyl-alpha-DLmaltotrioside and methyl-beta-D-maltotrioside, S 2.95 2.84 3.92 higher methyl-alpha- and beta oligosides, S 0. 25 0.25 0.85 methyl-alpha-D-glucofuranoside and methyl-beta-D-glucofuranoside, % 5.26 4.79 6.03 Dextrose, S 2.95 3.34 2.12 Other and unidentified, % 1.60 1.52 1.59 Retention time, min., 16.50 io.70 8.00 (All runs at 6.8:1 moles methanolmole AGU, 0.005 mole p-TSA/mole AGU, 167 C., PFP starch at 5.0% moisture.) All of the above runs were performed at 1670C. It can be seen from Table VI that increasing the retention time from 8 to 16.5 minutes favors increased nethyl-alpha-Doglucopyranoside yields, and a decrease in the levels of polyglycosides. EXAMPLE 8 In this example, a methyl glycoside fixture was continuously prepared according to Example 1 except the pressurized vessel was placed with a high pressure pump to transfer and force the feed slurry through the reactor. After each cycle through the reactor, a portion of the methyl-alpha-D-glucopyranoside was recovered from the glycoside mix- ture. The balance of the unrecovered methyl-alpha-D-glucopyranoside was then recycled, as part of the mother liquor, to the feed slurry. Supplerental amounts Or starch, methanol, catalyst (as needed) were added to the mother liquor to maintain a satisfactory yield of methyl-alpha-P glucopyraooside. The parts by weight material used for the initial start- up reaction, the supplemental amounts of reactants and catalyst added to the mother liquor for each recycle, the percentage of non-volatiles produced in each recycled feed slumr and the yield of recovered crystal line methyl-alpha-D-glucopyranoside (parts by weight and its percentage of the total weight of non-volatile reaction product solids) for each successive pass through the reactor are tabulated in Table VII. TABLE VII INITIAL RECYCLE RECYCLE RECYCLE RECYCLE RECYCLE Run 1 2 3 4 5 Methanol 16,000 5,140 4,311 5,070 3,287 5,605 Starch (d. s.) 8,100 1,873 1,419 1,670 1,536 1,766 H2O (form starch) 426 99 75 88 81 93 Recycle of mother liquor (as is) 0 10,121 12,593 12,604 13,127 12,457 p-TSA 57 13,2 10,3 0 0 0 TOTAL WEIGHT, g 24,583 17,246 18,408 19,432 18,031 20,011 % solids 32.9 32.1 32.8 29.9 35.9 32.1 Crystalline Harvest p.b.w. 2,244 1,699 1,670 1,536 1,766 1,678 Harvest as % of Total.solids, d. s. 33.7 27.1 26.5 25.3 27.2 25.9 On a non-volatile weight basis, the composition of the methyl glycoside obtained from the initialrun consisted of methyl-alpha-D- glucopyranoside 49.95%, methyl-beta-D-glucopyranoside 27.19% methylalpha and methyl-beta-D-glucofuranoside 5.95%, methyl-alpha- and methylbeta-D-maltosides 10.70%, methyl-alpha- and methyl-beta-D-maltotriosides 1.57%, methyl-alpha and methyl-beta-D-oligisides 0.12%, dextrose 2.72%, unidentified components 1.38% and other components 0.41%. By maintaining relatively constant reaction conditions, a comparable equilibrated reaction product was obtained fcca each of the ensuing recycle reactions. In the initial and subsequent recycles, the tubular reactor was maintained at 170 C with the slurry feed rate being adjusted to provide an average reactor residence time o± between 12-15 minutes. The effluent issuing from the tubular reactor for each run was instantaneously flashed to atmospheric pressure. The flash-cooling step concentrated the glycoside mixture to approximately 50S by weight nonvolatile solids. Crystallisation of the methyl-alpha-D-glucopyranoside was accomplished by cooling the mixture to about 150C. The crystals were then recovered from the glycoside mixture by filtration, washed with methanol (250C.) and vacuum-oven dried (600C. - 28 inch mercury). The conposition of the crystalline fraction and mother liquor was determined by liquid chromatographic analysis. The resultant cos- position for each mother liquor following the recovery of crystalline methyl-alpha-D-glucopyranoside is set forth in Table VIII. TABLE VIII COMPOSITION OF THE MOTHER LIQUOR Initial Recycled Mother Liquor Form Run 1 2 3 4 5 methyl-alpha-D-glucopyranoside 27.26 35.50 29.19 32.58 29.20 26.72 methyl-beta-D-glucopyranoside 40.20 39.01 39.70 38.28 38.72 38.75 methyl-alpha-D-glucofuranoside and methyl-beta-D-glucofuranoside 8.98 9.31 8.93 10.11 11.19 11.16 methyl-alpha-D-maltoside and methyl-beta-D-maltoside 15.04 11.94 12.45 11.96 12.21 12.09 methyl-alpha-D-maltotrioside and methyl-beta-D-maltotrioside 2.05 1.21 1.39 1.24 1.49 1.26 higher methyl- alpha- and beta- oligisides .13 .15 .48 .44 .65 .74 Dextrose 3.66 3.41 4.59 3.15 3.45 3.64 Unidentified 2.08 2.42 3.22 2.24 2.96 2.97 Other .58 .05 .05 - .48 .47 Yiled, % 33.7 27.1 26.5 26.3 27.2 25.9 (Ratio of recovered crystals to total weight, d. s., available) Table IX abows that the present invention affords a menas for continuously producing a high purity methyl-alpha-D-glucopyranoside crystalnine product hum a reaction medium comprised of recycled mother liquor rich in reaction by-products, starch and methanol. TABLE IX Recycle Process- Liquid Chromatographic Anylysis of Isolated Crystals and Mother Liquor Initial Crystals Form Run 1 2 3 4 5 COMPOSITION methyl-alpha-D-glucopyranoside 94.54 96.52 97.11 98.39 95.57 98.08 methyl-beta-D-glucopyranoside 1.61 < 1 < 1 < 1 < 1 < 1 methyl-alpha-D-glucofuranoside and methyl-beta-D-glucofuranoside - - - - - methyl-alpha-D-maltotrioside and 2.17 1.77 1.72 .88 1.26 .88 methyl-beta-D-maltotrioside methyl-alpha-D-maltotrioside and .61 .27 .29 - .78 .31 methyl-beta-D-maltotrioside higher methyl- alpha- and beta- oligosides .10 .06 - - 2.02 .25 Dextrose .87 1.09 .88 .66 .37 .48 Other .10 .30 - .07 - - As illustrated above, the present recycle process affords the moans of optimizing the effective use of starch and methanol and directly converting these reactants into the desired methyl-alpha-D-glucopyranoside product. The recycle process provides a means for providing a fUll complement of the reaction by-products (i.e. nethyl-beta-D-glucopyrano- side, methyl-alpha-and methyl-beta-D-glucofuranoside, methyl-alpha and methyl-beta-D-maltosides, methyl-alpha-and methyl-beta-D-maltotriosides, methyl-alpha- and methyl-beta-D-oligosides, dextrose, unidentified CCT- pcnents and other compounds)which avoids the subsequent unnecessary production of these by-products in the ensuing runs. This permits the recycled reactants to be converted substantially into the desired end product. Although not shown by this example, the methanol is advan tageously recovered and recycled into the process (e.g. crystal wash and/or recycled to the feed slurry). It should also be noted that the recycled mother liquor did not adversely affect either the yield or the purity of the recovered crystalline product. Similarly, the mother liquor of recycle 5 and subsequent mother liquors (which could have been obtained by further continuous operation)could have been effectively used to produce further amounts of methyl-alpha-D-glucopyranoside,

Claims: Claims: 1. The method for directly converting monohydric alcohols and carbohydrates into hydrocarbyl aldoside mixtures, characterized in that (a) a fluid slurry comprised of carbohydrate, monohydric alcohol and acid catalyst in an amount sufficient to permit chemical conver sion of the fluid slurry into a fluid hydro carbyl aldoside mixture, is provided to a continuous tubular reaction zone under a posi tive fluid pressure; (b) said feed slurry within said continuous tubular reaction zone is heated to a elevated tempera ture for a period of time sufficient to convert said fluid slurry into a fluid hydrocarbyl aldoside mixture while continuously providing additional feed slurry to said tubular reaction zone under a positive fluid pressure to force the converted fluid hydrocarbyl aldoside mix ture through said tubular reaction zone; and (c) at least one hydrocarbyl aldoside is recovered from said fluid hydrocarbyl aldoside mixture. 2. The method according to claim 1 characterized in that the converted fluid hydrocarbyl aldoside mixture is rapidly cooled before recovery of the converted hydrocarbyl aldoside or mixture of such aldosides therefrom. 3. The method according to claim 1 or 2 characterized in that the converted fluid hydrocarbyl aldoside mixture is partitioned into a mother liquor and aldoside by selectively removing at least a portion of one hydrocarbyl aldoside from the fluid hydro b P carbyl aldoside mixture and that the mother liquor is recycled to the fluid slurry of step (a) of claim 1. 4. The method according to any of claims 1 to 3 characterized in that the catalyst is selected from the group consisting of hydrochloric acid, sulfuric acid, ortho-, meta- and para-toluene-sulfonic acid, benzene-sulfonic acid, phosphoric acid, substituted benzene-sulfonic acids, ethane-sulfonic acid and combinations of the above. 5. The method according to any of claims 1 to 4 characterized in that the catalyst concentration in the slurry is continuously adjusted to the range of about 0.001 to 0.1 mole per mole of carbohydrate on dry solid.basis. 6. The method according to any of claims 1 to 5 characterized in that the monohydric alcohol consists essentially of aliphatic monohydric alco hol containing from 1 to 4 carbon atoms inclusive and the carbohydrate consists essentially of starch. 7. The method according to claim 6 characterized in that the monohydric alcohol consists essentially of methanol, the continuous tubular reactor has a total length of at least about 15.24 m (50 feet), and has internal diameter of about 0.45. to 15.25 cm (0.18 to 6.0 inches), the temperature of the slurry within-the reaction zone is maintained between 100 and 4000C., and the auerage reaction time in the reaction zone ranges from about 2-30 minutes with said reaction conditions being sufficient to provide a hydrocarbyl aldoside mixture comprised of (in percent by weight): : 45.67-51.54 alpha-methyl glucoside, 25.88-27.96 beta-methyl glucoside, 8.67-14.73 alpha- and beta-methyl diglycoside, 1.04-3.92 alpha- and beta-methyl triglycoside, 0.07-1.19 higher methyl glycoside, 5.26-7.54 glucofuran, and 1.02-3.34 dextrose. 8. The method according to any of claims 1, 2 and 4 to 7 characterized in that a fluid slurry of carbo hydrate is continuously made in monohydric alcohol in which the amount by weight of monohydric alcohol exceeds the amount by weight of carbohydrate, said carbohydrate/monohydric alcohol slurry is heated instantaneously to a temperature ranging from 00 to 4000C. while moving said slurry through a confined zone comprising a continuous tubular reactor which is at least 15.24 m (50 feet) in length* and has an internal diameter of about 0.45 to 15.25 cm (0.18 to 6.0 inches), and in which the slurry is transferred therethrough by fluid pressure only under high temperature and pressure in the presence of the acid catalyst to continuously pro duce a mixture of hydrocarbyl aldosides. 9. The method according to any of claims 1, 2 and 4 to 8 characterized in that the monohydric alcohol is methanol and the methanol/starch mole ratio in the slurry is in the range of 15:1 to 6.5:1, the reaction temperature in the confined zone is about 160 to 1800C., the retention time in the confined zone is about 8 to 20 minutes, the catalyst is present in an amount of at least 0.004 mole per anhydroglucose units, and the alcoholysis of the slurry within said confined zone is maintained under conditions sufficient to yield a mixture of alkyl glycosides containing from about 65 to 90 % alpha and beta-methyl glucoside. 10. The method according to any of claims 3 to 6 characterized in that the hydrocarbyl aldoside mixture forced through the tubular reaction zone is immediately passed through a cooling zone of a substantially reduced pressure and temperature to cool the hydrocarbyl aldoside mixture to a tempera ture below its boiling point. 11. The method according to any of claims 3 to 6, 8 and 10 characterized in that the monohydric alcohol consists essentially of methanol and the feed slurry is converted to a hydrocarbyl aldoside mixture containing at least 40 % by weight (solids basis) methyl-alpha-D-glucopyranoside. 12. The method according to any of claims 3 to 6 and 8 to 11 characterized in that at least 25 % of the total weight of the methyl-alpha-D-glucopyrano side of the aldoside mixture is recovered from the aldoside mixture prior to recycling of the mother liquor to the feed slurry. 13. The method according to any of claims 3 to 6 and 9 to 12 characterized in that the hydrocarbyl aldoside mixture forced through the tubular reaction zone is flash-cooled to the boiling point of the hydrocarbyl aldoside mixture. 14. The method according to any of claims 3 to 6 and 9 to 13 characterized in that the hydrocarbyl aldo side mixture is concentrated to a dry solids content between about 40 % to about 80 % by weight and at least a major weight portion of the methyl-alpha-D glucopyranoside is crystallized from the mixture at a crystallization temperature ranging from about 50C. to about 500C. 15. The method according to any of claims 3 to 6 and 10 to 14 characterized in that the mother liquor is fortified with sufficient starch and methanol to permit the conversion of the feed slurry into a hydrocarbyl aldoside mixture containing, on a solids weight basis, at least 45 5 % by weight methyl-alpha D-glucopyranoside.

Inventors: BOMBALL, WILLIAM ALLEN, MOSER, KENNETH BRUCE, ROTH, CLARIS DEANE
Applicants: A.E. STALEY MANUFACTURING COMPANY
Application year: 1980
Main classification: C07H15
IPC codes: C07H15, B01J19