Methods and systems for producing alkyl polyglucosides

Abstract

Methods and systems for producing alkyl polyglucosides are provided. These methods and systems offer improved purification that results in reduced product degradation.

Description

Technical Field

[0001] This invention relates to methods and systems for producing alkyl polyglucoside. Background Technology

[0002] The listing or discussion of previously published documents in this specification should not necessarily be construed as an admission that such documents are part of the prior art or common general knowledge.

[0003] Alkyl polyglucosides (APGs) are nonionic surfactants used in a variety of applications such as cosmetics, laundry detergents, and industrial cleaning. APGs are derived from glucose and fatty alcohols, making them desirable because they are highly biodegradable. APG production typically involves three main stages: a glycosylation step in the presence of a large excess of alcohol, purification of the APG product (including removal of excess alcohol), and post-processing steps such as dissolution and pH / color adjustment.

[0004] The problem associated with APG production is that it has a high melting point and viscosity, but is also prone to thermal degradation and oxidation at high temperatures. These properties pose challenges during APG production, especially during the purification stage.

[0005] Typically, the purification of APG involves using a falling film evaporator to remove most of the fatty alcohol remaining from the glycosylation step, followed by a mechanically stirred thin-film evaporator (also known as a scraped-film evaporator) to remove the remaining fatty alcohol and separate the APG product. During evaporation, a vacuum is usually used because the lower operating pressure reduces the boiling point of the liquid to be evaporated, allowing for the use of lower temperatures than required under standard pressure.

[0006] The first evaporation step, using a falling film evaporator, removes most of the fatty alcohol solvent from the APG product. A falling film evaporator is a vertical tubular evaporator that relies on gravity to allow a thin fluid, fed from the top of the unit, to flow freely downwards to the bottom where the concentrate is collected. Evaporation occurs on the surface of a highly turbulent falling liquid film. Separation of the entrained liquid from the vapor is typically accomplished in a column connected to the bottom unit. Due to its large unit size, low liquid holdup, small footprint, and good heat transfer over a wide range of conditions, the falling film unit is well-suited for removing large amounts of diluent (which can typically be up to 70% alcohol solvent in APG product samples).

[0007] The remaining highly viscous residue is then subjected to a second evaporation step using a thin-film evaporator to further reduce the fatty alcohol content to less than 1%. A second distillation at a higher temperature is required because the high viscosity of the residue necessitates higher temperatures to evaporate the fatty alcohol. Thin-film evaporators are well-suited for processing viscous fluids due to their mechanical blades, which produce high surface renewal rates and highly turbulent conditions even for extremely viscous fluids. As the APG product mixture (feed) enters the thin-film evaporator, a scraper rotates at high speed (typically several hundred rpm) to spread the process fluid and create a thin film on the evaporator surface. The evaporator is heated under vacuum (e.g., 50 mbar) to the boiling point of the fatty alcohol, causing it to evaporate into a gas. The gas enters a condenser, where it is condensed and collected in a distillate collection tank. Simultaneously, the residue left after thin-film evaporation flows down the sidewalls of the evaporator and is collected in a concentrate collection tank.

[0008] Single-pass plug flow operation of thin-film evaporators is advantageous for minimizing the thermal degradation of heat-sensitive products during the evaporation step. A variety of standard thin-film evaporator designs are commercially available, including short-pass distillation with a built-in condenser in the evaporation chamber. This configuration shortens the distance the gas travels from the evaporator surface to the condenser, thereby reducing residence time and the chance of distillate decomposition or oxidation.

[0009] Despite using a vacuum, the required high operating temperatures inevitably lead to some degree of product degradation and discoloration. The use of thin-film evaporators for APG purification also contributes to the high cost of the process, as thin-film evaporators are typically precision machines and therefore more expensive than other types, especially when strictly comparing equivalent heat transfer areas. Furthermore, short-path distillation tends to accumulate residues inside the evaporator and requires regular maintenance. The entire system includes several leak-prone connection parts, such as valves and flanges. These moving parts and multiple connections require regular and periodic maintenance, increasing the overall cost of the process. Finally, the system also requires the use of expensive gear pumps to remove high-viscosity residues.

[0010] Therefore, there is a need for a purification method that involves lower operating temperatures and reduced process costs. Summary of the Invention

[0011] The inventors have unexpectedly discovered that plate heat exchangers can be used instead of thin-film and short-path distillation equipment in the purification process. Plate heat exchangers have many advantages over conventional thin-film evaporators and short-path distillers used in the art.

[0012] Plate heat exchangers offer high heat transfer coefficients.

[0013] Plate heat exchangers allow for highly customizable heat transfer areas due to the flexibility in plate size, corrugation pattern, and passage layout.

[0014] Plate heat exchangers can be easily disassembled for cleaning, inspection, and maintenance.

[0015] Plate heat exchangers offer high shear rates and stresses, high turbulence and mixing, and low fouling on the plates. This means that plate heat exchangers are well-suited for handling high-viscosity flow, such as APG.

[0016] Plate heat exchangers are cheaper than traditionally used equipment.

[0017] Plate heat exchangers also allow for the efficient separation of APG from fatty alcohols through a single separation step rather than multiple evaporation or distillation steps.

[0018] Therefore, the present invention provides the following.

[0019] 1. A method for removing at least one impurity from a stream containing alkyl polyglucosides, the method comprising the steps of:

[0020] (i) providing a first fluid flow in which the liquid phase contains alkyl polyglucoside and at least one impurity; and

[0021] (ii) Passing a first fluid stream containing alkyl polyglucosides and at least one impurity through a plate heat exchanger.

[0022] In step (ii), the second fluid flow simultaneously passes through a plate heat exchanger, the second fluid flow is fluidly isolated from the first fluid flow, and heat energy is transferred from the second fluid flow to the first fluid flow, thereby increasing the temperature of the first fluid flow to form a heated first fluid flow with a temperature higher than the boiling point of at least one impurity in the first fluid flow, such that the heated first fluid flow includes a liquid phase containing alkyl polyglucosides and a gas phase containing at least one impurity, and the gas phase is separated from the liquid phase.

[0023] 2. The method according to Clause 1, wherein the at least one impurity comprises one or more fatty alcohols.

[0024] 3. The method according to Clause 2, wherein the one or more fatty alcohols include fatty alcohols having 4 to 26 carbon atoms, for example 8 to 20 carbon atoms, for example 10 to 16 carbon atoms, for example 12 carbon atoms.

[0025] 4. The method according to any one of the preceding clauses, wherein the second fluid flow comprises steam.

[0026] 5. The method according to any one of the preceding clauses, wherein the first fluid flow enters the plate heat exchanger at a temperature of about 60°C to about 100°C, optionally about 70°C to about 90°C, for example about 80°C.

[0027] 6. The method according to any one of the preceding clauses, wherein the second fluid flow enters the plate heat exchanger at a temperature of about 160 to about 200°C, optionally about 170 to about 190°C, for example about 180°C.

[0028] 7. The method according to any one of the preceding clauses, wherein the first fluid flow is heated by the second flow to a temperature of about 125°C to about 165°C, for example about 140°C to about 155°C.

[0029] 8. The method according to any one of the preceding clauses, wherein the first fluid flow is subjected to a pressure of about 0.1 to 10 kPa, optionally about 0.5 to about 5 kPa, in the plate heat exchanger.

[0030] 9. The method according to any one of the preceding clauses, wherein one or more of the following are applicable:

[0031] (a) The at least one impurity includes one or more fatty alcohols;

[0032] (b) The first fluid flow is heated by the second fluid flow to a temperature of approximately 110°C to approximately 170°C; and

[0033] (c) The first fluid flow is subjected to a pressure of about 0.1 to 10 kPa in the plate heat exchanger.

[0034] 10. The method according to any one of the preceding clauses further includes the step of condensing and collecting at least one impurity present in the separated gas phase of the first fluid flow after step (i).

[0035] 11. The method according to any one of the preceding clauses, wherein the separation of the first heated phase is achieved by introducing a heated first stream into a flash tank having an internal volume larger than that of a plate heat exchanger, so as to separate the gas phase containing at least one impurity from the liquid phase containing alkyl polyglucosides.

[0036] 12. The method according to Clause 11, wherein the pressure inside the flash tank is lower than the pressure of the first heated fluid flow entering the tank, optionally wherein the pressure inside the flash tank is about 1 kPa to about 3 kPa.

[0037] 13. A system for purifying alkyl polyglucosides, the system comprising a plate heat exchanger configured to heat a first fluid stream containing alkyl polyglucosides and at least one impurity to a temperature above the boiling point of said at least one impurity. Attached Figure Description

[0038] Figure 1 The diagram shows a process flow chart of a conventional APG production system, in which APG is purified using a falling film evaporator and a short-path distiller.

[0039] Figure 2 A process flow diagram of an APG production system according to the present invention is shown, wherein a plate heat exchanger is used to purify APG.

[0040] Some embodiments of this disclosure are described more fully below with reference to the accompanying drawings. Detailed Implementation

[0041] The present invention provides a method for removing at least one impurity from a stream containing alkyl polyglucosides during the production process of alkyl polyglucosides.

[0042] Alkyl polyglucosides are typically produced commercially using Fischer glycosylation. This process involves direct glycosylation and transglycosylation to create an acetal bond between the glucose glycohead and the fatty alcohol hydroxyl group. The method is generally a batch process, in which a fatty alcohol (typically lauryl alcohol) is pumped into a reactor, where it is stirred and heated. During the heating process, glucose (typically in anhydrous solid form) is fed into the reactor. Proper mixing is required to ensure good dispersion of the solid particles in solution. When the reaction mixture reaches a temperature of about 110°C to 115°C, a dodecylbenzenesulfonic acid (DBSA) catalyst is added to the reactor. The reaction proceeds at about 110°C and a pressure of about 3 to about 5 kPa for about 4 hours. During the reaction, alkyl polyglucosides (APGs) with varying degrees of polymerization are produced, along with water (as steam). The steam is simultaneously removed to improve the reaction yield. This steam stream, typically vented from the top of the reactor containing both water and evaporated fatty alcohol, enters a cooler where it is partially condensed. The collected fatty alcohol can be recycled as feedstock for the next batch of processing. The main advantage is that the residual vapor from the water can be further condensed to form liquid water, which can then be sent to a wastewater treatment plant.

[0043] Once the reaction is complete, the reactor temperature is lowered to approximately 70°C, and the pressure is increased to atmospheric pressure. The reaction mixture is neutralized within the reactor, for example, by adding sodium hydroxide. The final pH of the solution is typically adjusted to a value of approximately 8 to 10. The product stream contains approximately 25% APG and must be purified.

[0044] Preliminary purification may involve filtration to remove solid impurities, such as unreacted glucose, as well as byproducts polydextrose and sodium laurylbenzenesulfonate. Subsequent purification steps are then performed on the liquid crude reaction product.

[0045] This invention provides a method useful for purifying liquid crude reaction products containing APG. Specifically, this invention provides a method for removing at least one impurity from a stream containing alkyl polyglucosides, the method comprising the following steps:

[0046] (i) providing a first fluid flow in which the liquid phase contains alkyl polyglucoside and at least one impurity; and

[0047] (ii) Passing a first fluid stream containing alkyl polyglucosides and at least one impurity through a plate heat exchanger.

[0048] In step (ii), the second fluid flow simultaneously passes through a plate heat exchanger, the second fluid flow is fluidly isolated from the first fluid flow, and heat energy is transferred from the second fluid flow to the first fluid flow, thereby increasing the temperature of the first fluid flow to form a heated first fluid flow with a temperature higher than the boiling point of at least one impurity in the first fluid flow, such that the heated first fluid flow includes a liquid phase containing alkyl polyglucosides and a gas phase containing at least one impurity, and the gas phase is separated from the liquid phase.

[0049] As used herein, alkyl polyglucoside (APG) refers to a chemical comprising a polyglucoside moiety attached to an alkyl moiety. The polyglucoside moiety is attached to the alkyl moiety via a CO bond formed by a carbon atom in the alkyl chain and an outer oxygen atom in the polyglucoside ring.

[0050] As used herein, a polyglucoside is a moiety consisting of multiple glucose rings linked by glycosidic bonds. Depending on the intended use of the polyglucoside, a wide range of number-average molecular weights can be produced. The number-average molecular weights of polyglucosides are typically 100 to 5000 Daltons, 200 to 2000 Daltons, 250 to 1000 Daltons, or 300 to 600 Daltons.

[0051] The alkyl group in alkyl polyglucosides typically contains 4 to 26 carbon atoms, for example 8 to 20 carbon atoms, for example 8 to 16 carbon atoms, for example 10 to 14 carbon atoms. In a specific embodiment of the invention, the alkyl group in the alkyl polyglucoside may contain 12 carbon atoms.

[0052] The chain length of alkyl groups affects the properties of APGs; different chain lengths are suitable for different applications. For example, C 12 Or C 14 Chain lengths are available for personal care applications (such as cosmetics, bath products, detergents, wipes, and oral care products) and household care applications (such as surface cleaners, dishwashing liquids, and laundry detergents). C8 or C 10 The chain length is suitable for hard surface cleaners, agricultural chemicals, and industrial cleaning products.

[0053] As used herein, “removal” of impurities means reducing the amount of the impurities in a product stream, such as a product stream containing APG. Impurities may be reduced to an amount not exceeding 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, or 0.1 wt% of the product stream. Typically, impurity removal results in the product stream containing less than 1 wt%.

[0054] As used herein, "impurity" refers to a chemical present in the product stream, not the desired product and water. Therefore, when the product stream contains APG as the desired product, the impurity in the product stream refers to any chemical present in the product stream other than APG or water. In some embodiments of the invention, the impurity may be one or more fatty alcohols.

[0055] As used herein, a fatty alcohol refers to a compound comprising a hydrophobic hydrocarbon moiety and an alcohol functional group. The hydrocarbon moiety may be saturated (i.e., alkyl) or unsaturated (e.g., alkenyl, or a group containing two or more C=C double bonds, such as dienyl or trialenyl). For example, a fatty alcohol may comprise an alkyl or alkenyl group attached to an alcohol group. Typically, a fatty alcohol may contain 4 to 26 carbon atoms, for example 8 to 20 carbon atoms, for example 8 to 16 carbon atoms, for example 10 to 14 carbon atoms. In a particular embodiment of the invention, the alkyl group in the fatty alcohol may contain 12 carbon atoms. Typically, a fatty alcohol comprises a linear (i.e., unbranched) carbon chain attached to a primary alcohol group.

[0056] As used herein, when used in the context of method steps, the “boiling point” of a chemical refers to the lowest temperature at which the chemical evaporates under the conditions it undergoes. Certain conditions, such as pressure or the presence of other components in the stream, can affect the boiling point of a chemical. Therefore, if a chemical is subjected to reduced pressure, its boiling point will be lower than its boiling point at standard pressure. Specifically, when within a plate heat exchanger, the boiling point of impurities present in the first stream will be lower than their boiling point at standard pressure. Similarly, and as those skilled in the art will understand, the boiling points of chemicals present in the mixtures disclosed herein may be higher or lower than the expected boiling point of the chemical alone. This is because boiling points can be increased or decreased due to the presence of other components in the mixture. Therefore, when used herein, the boiling point of a chemical (e.g., an impurity) means the boiling point of the chemical in the mixtures disclosed herein.

[0057] When the first fluid stream is heated to a temperature above the boiling point of at least one impurity, the impurity will evaporate and enter the gas phase, forming a gas phase together with the liquid phase within the first stream. This gas phase can be easily separated from the liquid phase, and the at least one impurity can be collected by a condenser. This is desirable when the at least one impurity contains a useful chemical such as unreacted fatty alcohol. In this case, the fatty alcohol can be collected and used to produce further alkyl polyglucosides.

[0058] To facilitate the separation of the gas and liquid phases within a plate heat exchanger, the plate heat exchanger can be designed to operate as a falling film evaporator, with a chamber placed at the bottom of the tubes to provide the necessary top space for vapor-liquid equilibrium.

[0059] The separation of the liquid first stream from the gaseous impurities can be carried out in a flash tank. Therefore, the heated liquid first stream and the gaseous impurities enter a flash tank having a larger volume than the internal space of a plate heat exchanger. This larger volume causes the liquid phase containing APG to accumulate at the bottom of the flash tank, while the gaseous phase can be removed from the top. As those skilled in the art will understand, the pressure inside the flash tank can be the same as, but typically lower than, the pressure inside the plate heat exchanger, for example, from about 1 kPa to about 3 kPa, such as about 2 kPa.

[0060] The highly viscous purified APG residue can be mixed with water to facilitate further processing.

[0061] The first stream is heated within a heat exchanger by a second stream, which is flowably isolated from the first stream but is able to transfer heat to the first stream through the heat exchanger. The second stream may contain or consist of steam heated to a temperature suitable for raising the temperature of the first stream to a desired temperature. For example, the second stream may enter the heat exchanger at a temperature of about 160 to about 200°C, optionally about 170°C to about 190°C, such as about 180°C.

[0062] To improve the efficiency of the heat exchanger, the first stream is typically preheated before entering the heat exchanger so that the temperature difference between the first and second streams is not excessively high. Therefore, the first stream can enter a heat exchanger having a temperature of about 60°C to about 100°C, optionally about 70°C to about 90°C, for example about 80°C.

[0063] It is explicitly considered here that the endpoints of any range disclosed herein can be combined with the endpoints of any other range of the same variable. As an illustrative example using the temperature range of the first stream entering a heat exchanger, the following temperature ranges are disclosed:

[0064] From about 60°C to about 70°C, from about 60°C to about 80°C, from about 60°C to about 90°C, and from about 60°C to about 100°C;

[0065] From about 70°C to about 80°C, from about 70°C to about 90°C, and from about 70°C to about 100°C;

[0066] From about 80°C to about 90°C, and from about 80°C to about 100°C; and

[0067] From approximately 90°C to approximately 100°C.

[0068] The following examples illustrate the invention and should not be construed as limiting.

[0069] Example

[0070] Example for reference: Synthesis of APG

[0071] APG can be synthesized in a batch reaction via Fischer glycosylation. Lauryl alcohol can be added to the reactor with stirring and heating, followed by anhydrous lauryl alcohol. The mixture is stirred to ensure good dispersion of the solid particles in solution. Once the reaction mixture reaches a temperature of 110°C to 115°C, a dodecylbenzenesulfonic acid (DBSA) catalyst is added. The reaction mixture is stirred at 110°C and a pressure of 3 to 55 kPa for 4 hours. Water vapor is continuously removed from the reactor and fed to a first condenser to collect the fatty alcohol, followed by a second, lower-temperature condenser to collect the liquid water.

[0072] The reaction products are alkyl polyglucosides (APGs) with varying degrees of polymerization. Once the reaction is complete, the reactor temperature is lowered to approximately 70°C, and the pressure is increased to atmospheric pressure. The pH of the reaction mixture is adjusted to 8–10 using a 5 wt% sodium hydroxide solution. The reaction mixture, containing approximately 25% APG, is then pumped into a hydrocyclone to filter out unreacted glucose and the byproducts polyglucoside and sodium laurylbenzenesulfonate. A crude product containing APG is obtained.

[0073] Comparative example: Conventional purification methods

[0074] The crude product can be used Figure 1 The purification equipment shown contains the following components.

[0075]

[0076] Before entering the falling film evaporator 103 (FFE), the product stream 124 from the cyclone filter is preheated to approximately 135°C by a heater (not shown). It then enters the falling film evaporator 103 (FFE). The desired operating temperature, pressure, and flow rate of the FFE are approximately 165°C, 1 kPa, and 0.6–8 m / s. Inside the FFE, the product stream flows through an externally steam-heated internal tube. Partial fatty alcohol and water evaporate and pass through a condenser to collect the fatty alcohol, which can be recovered for future batches. The residue leaving the bottom of the FFE is then transferred through a heat exchanger 103 before entering the short-path still 105. The desired operating temperature, pressure, and flow rate of the short-path still are approximately 170°C (evaporator and residue lines), 0.05–0.1 kPa (fluctuations), 0.7 L / h feed flow rate, and 300 rpm stirrer speed.

[0077] The fatty alcohols in the product stream will be evaporated, then condensed and collected for reuse (see circulating alcohol stream 126). Simultaneously, the distilled APG is collected and immediately mixed with water before being fed into storage tank 111. The stream entering the storage tank consists of approximately 50 wt% APG and less than 1% fatty alcohols in the water.

[0078] Example: Purification process using a plate heat exchanger

[0079] The crude product can be used Figure 2 The apparatus and method of the present invention shown are for purification, wherein the components are as follows.

[0080]

[0081] The product stream 124 from reactor 101 is preheated to approximately 80°C by a heater (not shown) before entering PHE 103 via a cold fluid inlet. Simultaneously, steam 127, serving as the working fluid, enters via a hot fluid inlet. The heat load of the PHE is approximately 0.5 kW. The arrangement of the gaskets allows the product stream to spread on one plate, while the steam spreads on adjacent plates. The desired operating temperatures, pressures, and flow rates for both streams are shown in Table 1.

[0082] Plate heat exchanger operating conditions Hot aisle Cold aisle 2. Fluid steam APG 3. Inlet temperature (°C) 180 80 4. Outlet temperature (°C) 120 125～165 5. Flow rate (L / h) 1 0.5～1 6. Maximum working pressure (MPag) 0.2 0.005

[0083] Table 1: Operating Conditions of Plate Heat Exchangers

[0084] Within PHE 103 (which exists at high temperature and low pressure), a portion of the fatty alcohols and water in the product stream is evaporated, such that the stream comprises a gas phase containing fatty alcohol and water vapor, and a liquid phase containing APG and any unevaporated fatty alcohol / water. To enable efficient separation of the entrained liquid from the vapor, the plate heat exchanger can be designed to operate as a falling film evaporator, with a chamber placed at the bottom of the tubes to provide the necessary vapor-liquid equilibrium headspace. The stream is then directed to flash tank 105, where the APG is separated from the evaporated fatty alcohols and water. The flash tank can withstand the same pressure and temperature as the plate heat exchanger, but typically at reduced pressure (e.g., from about 1 kPa to about 3 kPa, for example, about 2 kPa). The fatty alcohol vapor is discharged as distillate or top product 126 and condensed and pumped into storage tank 106 for recycling as feedstock for the next batch of reaction. Simultaneously, the purified APG residue 128 will be discharged as a bottom product and can be pumped out and mixed with water and NaOH 129 to facilitate further processing. If necessary, product stream 128 can be bleached with hydrogen peroxide 130 in mixing tank 110. If bleaching is not required, the mixing tank can be bypassed with line 131. The final APG stream can consist of approximately 50 wt% APG in water with less than 1% fatty alcohol, as such a stream is easier to process than APG residue without water.

[0085] If the flow leaving the plate heat exchanger requires further separation, APG and alcohol 132 can enter the storage tank 104 and then return to the plate heat exchanger 103.

[0086] As shown in this embodiment, the advantage associated with using PHE to separate APG from fatty alcohols is that efficient separation can be achieved without the need for multiple distillation steps, as is required in existing processes utilizing stirred evaporation and short-path distillation techniques.

Claims

1. A method for removing at least one impurity from a stream containing alkyl polyglucosides, the method comprising the steps of: (i) Providing a first fluid flow in a liquid phase containing alkyl polyglucosides and at least one impurity; and (ii) Passing the first fluid stream containing alkyl polyglucosides and at least one impurity through a plate heat exchanger. In step (ii), the second fluid flow simultaneously passes through the plate heat exchanger, the second fluid flow being fluidly isolated from the first fluid flow, and heat energy is transferred from the second fluid flow to the first fluid flow, thereby increasing the temperature of the first fluid flow to form a heated first fluid flow with a temperature higher than the boiling point of at least one impurity in the first fluid flow, such that the heated first fluid flow comprises a liquid phase containing alkyl polyglucosides and a gas phase containing the at least one impurity, and the gas phase is separated from the liquid phase.

2. The method according to claim 1, wherein the at least one impurity comprises one or more fatty alcohols.

3. The method according to claim 2, wherein the one or more fatty alcohols include fatty alcohols having 4 to 26 carbon atoms.

4. The method of claim 1, wherein the second fluid flow comprises steam.

5. The method according to claim 1, wherein the first fluid flow enters the plate heat exchanger at a temperature of 60°C to 100°C.

6. The method according to claim 1, wherein the second fluid flow enters the plate heat exchanger at a temperature of 160 to 200°C.

7. The method of claim 1, wherein the first fluid flow is heated to a temperature of 125°C to 165°C by the second flow.

8. The method of claim 1, wherein the first fluid flow is subjected to a pressure of 0.1 to 10 kPa in the plate heat exchanger.

9. The method of claim 1, wherein one or more of the following are applicable: (a) The at least one impurity contains one or more fatty alcohols; (b) The first fluid flow is heated to a temperature of 110°C to 170°C by the second fluid flow; and (c) The first fluid flow is subjected to a pressure of 0.1 to 10 kPa in the plate heat exchanger.

10. The method of claim 1, further comprising, after step (i), condensing and collecting the at least one impurity present in the separated gas phase of the first fluid flow.

11. The method of claim 1, wherein the separation of the first heated stream is achieved by feeding the first heated stream into a flash tank having an internal volume larger than that of the plate heat exchanger to separate the gas phase containing the at least one impurity from the liquid phase containing the alkyl polyglucoside.

12. The method of claim 11, wherein the pressure inside the flash tank is lower than the pressure of the first heated fluid flow entering the tank.

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