A STATIC MIXER CONTINUOUS FUOW REACTOR

TECHNICAL FIELD

[0001] The present disclosure relates to methods of producing hydroxyaldehyde, more specifically methods of producing hydroxypivaldehyde by using a static mixer continuous flow reactor.

BACKGROUND

[0002] Hydroxypivaldehyde (HP A, 3 -hydroxy-2, 2-dimethylpropanal, also known as hydroxypivalaldehyde) is a widely used starting material for the preparation of various products such as neopentyl glycol (NPG, 2, 2-dimethyl-l, 3 -propanediol), ester glycol (HPHP, hydroxypivalyl hydroxypivalate), spiroglycol [SPG, 3,9-bis(l,l-dimethyl-2-hydroxyethyl)-2,4,8,10- tetraoxaspiro(5.5)undecane], etc., which are used in lubricants, plastics, surface coatings, surfactants, synthetic resins, antioxidants, and chemical intermediates.

[0003] HPA is typically produced by an aldol condensation reaction of isobutyraldehyde (P3A) and formaldehyde (FA, HCHO) in the presence of a base catalyst to form HPA. Conventionally, HPA synthesis occurs as a batch reaction, most often catalyzed by a strong base such as sodium hydroxide (NaOH), or any other suitable alkali metal hydroxide and/or alkaline earth metal hydroxide, typically employed as an aqueous solution with a concentration of about 10 wt.%. A disadvantage of this method of HPA synthesis resides in the isolation of HPA from the product mixture. For example, the separation requires a large amount of extractive solvent, and is followed by rectification or direct distillation of HPA from the product mixture, which leads to heavies formation as well as Tishchenko and Cannizzaro byproducts formation. Further, salt is produced during the reaction, which is also difficult to separate from the product mixture.

[0004] Phase transfer catalysts (PTC) have also been employed in HPA synthesis, for example tetraalkyl ammonium or phosphonium hydroxides; however, such synthesis methods require the separation of PTC and suffer from the same disadvantages as the methods that use alkali metal hydroxide or carbonate catalysts. Further, the salts formation can hinder HPA hydrogenation to neopentyl glycol (NPG), and thus the salt must be separated from the product mixture.

[0005] Trialkylamine (TAA) catalysts (e.g., trimethylamine (TMA) and/or triethylamine (TEA)) have also been employed in HPA synthesis. However, TAA are conventionally used in HPA synthesis in high concentrations that require an efficient separation process, since amines are hydrogenation catalyst poisons. Further, in batch HPA synthesis reactions, TAA catalysts enable side reactions and formation of acid salts (given that excess formaldehyde is also used conventionally in HPA synthesis), which are hydrogenation catalyst inhibitors. Thus, there is an ongoing need for the development of HPA production processes without excess reactants (e.g., HCHO and IB A) and with a decreased amount of amine catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] For a detailed description of the preferred aspects of the disclosed methods, reference will now be made to the accompanying drawing in which:

[0007] Figure 1A displays a configuration of a hydroxypivaldehyde (HPA, 3 -hydroxy-2, 2- dimethylpropanal) production system;

[0008] Figure IB displays another configuration of an HPA production system;

[0009] Figure 2 displays a schematic of byproduct formation reactions through Tischenko and Cannizzaro that can accompany the cross-aldol condensation reaction between isobutyraldehyde (IB A) and formaldehyde (FA);

[0010] Figure 3 displays a configuration of a reactor temperature control system;

[0011] Figure 4 displays by-products that can form via cross Cannizzaro/Tischenko side reactions;

[0012] Figure 5 displays specific experimental conditions and samples collection point for the cross-aldol condensation reaction between P3A and FA;

[0013] Figure 6 displays a graph of P3A conversion as a function of reaction time in a batch cross-aldol condensation reaction; and

[0014] Figure 7 displays a graph of P3A conversion as a function of reaction time in batch vs. continuous flow cross-aldol condensation reactions.

DETAILED DESCRIPTION

[0015] Disclosed herein are processes for producing hydroxypivaldehyde (HPA, 3 -hydroxy-2, 2- dimethylpropanal). In an aspect, a process for producing HPA can comprise (a) reacting under isothermal conditions, via a cross-aldol condensation reaction, an HPA reactant mixture in a continuous flow HPA reactor to produce an HPA product mixture; wherein the HPA reactant mixture comprises isobutyraldehyde (P3A), formaldehyde (FA), water, and a trialkylamine (TAA); wherein TAA comprises trimethylamine (TMA) and/or triethylamine (TEA); wherein the HPA reactant mixture is characterized by an IB A to FA mole ratio of from about 1 : 1 to about 1.2: 1, preferably about 1 : 1; wherein the HPA reactor is characterized by an internal HPA reactor volume and an internal HPA reactor surface area; wherein the ratio of the internal HPA reactor surface area to the internal HPA reactor volume is from about 30 m ¹ to about 4,000 m ¹ ; wherein the HPA reactor is characterized by a reactor temperature of less than about 100 °C; wherein the isothermal conditions comprise a reactor temperature variation of less than about + 10 °C, preferably less than about + 1 °C; wherein the HPA product mixture comprises HPA, water, TAA, and optionally neopentyl glycol (NPG, 2, 2-dimethyl-l, 3 -propanediol); wherein the HPA reactor is characterized by an IBA conversion of equal to or greater than about 90%, preferably equal to or greater than about 95%, as determined by gas chromatography-mass spectrometry (GC-MS); wherein the HPA reactor is characterized by a selectivity to HPA and NPG of from about 95% to about 99.9%, preferably from about 98% to about 99.9%, as determined by GC-MS; and (b) recovering at least a portion of the HPA and optionally NPG from the HPA product mixture. In an aspect, the HPA reactant mixture can further comprise methanol; wherein the step of recovering at least a portion of the HPA and optionally NPG from the HPA product mixture can comprise a one-step distillation of at least a portion of the HPA product mixture to yield an HPA solution and a TAA solution; wherein the HPA solution comprises HPA, water, methanol, and optionally NPG; and wherein the TAA solution comprises TAA, and methanol. In such aspect, the HPA solution can be further subjected to hydrogenation for NPG production. The TAA solution can be recycled to the continuous flow HPA reactor. The process for producing HPA as disclosed herein excludes dynamic mixing of the HPA reactant mixture within the HPA reactor.

[0016] In an aspect, HPA can be collected for analysis from the HPA product mixture by cooling the HPA product mixture to a temperature lower than the reactor temperature, more specifically by cooling the HPA product mixture to room temperature and recovering the solid HPA phase. The recovered HPA was analyzed by gas chromatography-mass spectrometry (GC-MS) on a Shimadzu GC-MS QP-2010 plus system for product identification and quantification. A few milligrams (mg) of solid sample (i.e., solid HPA phase) was dissolved in acetonitrile and analyzed on the Shimadzu GC-MS QP-2010 plus system equipped with flame ionization detector (FID). The GC was equipped with CP- WAX 52 CB column of dimensions 50 m (length) x 0.32 mm (internal diameter, ID) x 1.2 pm (film thickness) and FID detector. The oven temperature was initially maintained at 35 °C (for 2 minutes) and then was ramped to 200 °C at a ramp rate of 10 °C x min ¹ (for 15minutes). The inlet and detector temperatures were maintained at 250 °C and 280 °C, respectively. 1 mΐ injection volume was processed for analysis.

[0017] Other than in the operating examples or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, and the like, used in the specification and claims are to be understood as modified in all instances by the term“about.” Various numerical ranges are disclosed herein. Because these ranges are continuous, they include every value between the minimum and maximum values. The endpoints of all ranges reciting the same characteristic or component are independently combinable and inclusive of the recited endpoint. Unless expressly indicated otherwise, the various numerical ranges specified in this application are approximations. The endpoints of all ranges directed to the same component or property are inclusive of the endpoint and independently combinable. The term“from more than 0 to an amount” means that the named component is present in some amount more than 0, and up to and including the higher named amount.

[0018] The terms“a,”“an,” and“the” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. As used herein the singular forms“a,”“an,” and“the” include plural referents.

[0019] As used herein,“combinations thereof’ is inclusive of one or more of the recited elements, optionally together with a like element not recited, e.g., inclusive of a combination of one or more of the named components, optionally with one or more other components not specifically named that have essentially the same function. As used herein, the term“combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0020] Reference throughout the specification to“an aspect,”“another aspect,”“other aspects,” “some aspects,” and so forth, means that a particular element (e.g., feature, structure, property, and/or characteristic) described in connection with the aspect is included in at least an aspect described herein, and may or may not be present in other aspects. In addition, it is to be understood that the described element(s) can be combined in any suitable manner in the various aspects.

[0021] As used herein, the terms“inhibiting” or“reducing” or“preventing” or“avoiding” or any variation of these terms, include any measurable decrease or complete inhibition to achieve a desired result.

[0022] As used herein, the term“effective,” means adequate to accomplish a desired, expected, or intended result. [0023] As used herein, the terms“comprising” (and any form of comprising, such as“comprise” and“comprises”),“having” (and any form of having, such as“have” and“has”),“including” (and any form of including, such as“include” and“includes”) or“containing” (and any form of containing, such as“contain” and“contains”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0024] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art.

[0025] Compounds are described herein using standard nomenclature. For example, any position not substituted by any indicated group is understood to have its valency fdled by a bond as indicated, or a hydrogen atom. A dash (“-”) that is not between two letters or symbols is used to indicate a point of attachment for a substituent. For example, -CHO is attached through the carbon of the carbonyl group.

[0026] As used herein, the terms“C _x hydrocarbons” and“C _x s” are interchangeable and refer to any hydrocarbon having x number of carbon atoms (C). For example, the terms“C4 hydrocarbons” and “C4S” both refer to any hydrocarbons having exactly 4 carbon atoms, such as n-butane, iso butane, cyclobutane, 1 -butene, 2-butene, isobutylene, butadiene, and the like, or combinations thereof.

[0027] As used herein, the term“C _x+ hydrocarbons” refers to any hydrocarbon having equal to or greater than x carbon atoms (C). For example, the term “C2 ₊ hydrocarbons” refers to any hydrocarbons having 2 or more carbon atoms, such as ethane, ethylene, C3S, C4S, C5S, etc.

[0028] Referring to Figure 1A, a hydroxypivaldehyde (HP A, 3 -hydroxy-2, 2-dimethylpropanal) production system 1000 is disclosed. The HPA production system 1000 generally comprises a continuous flow HPA reactor 100; a back-pressure regulator 150; an HPA product mixture collection unit 200; reagent containers 10, 20; pumps 15, 25; fluid flow monitoring devices (e.g., flow meters) 16, 26, 36, wherein flow meter 36 can be optional; temperature monitoring devices (e.g., temperature sensors) 17, 27, 37; pressure monitoring devices (e.g., pressure sensors) 18, 28, 38; valves (e.g., check valves) 19, 29; and a T-joint 30. In some aspects, the temperature monitoring devices can be kept directly in reagent containers 10, 20 (e.g., inside reagent containers 10, 20) and/or in the HPA product mixture collection unit 200 to monitor temperature. The continuous flow HPA reactor 100 can have its own temperature sensor to monitor and/or control the temperature of reaction.

[0029] Referring to Figure IB, an HPA production system 2000 is disclosed. The HPA production system 2000 generally comprises a continuous flow HPA reactor 100; and an HPA product mixture separating unit 250. As will be appreciated by one of skill in the art, and with the help of this disclosure, HP A production system components shown in Figures 1A-1B can be in fluid communication with each other (as represented by the connecting lines indicating a direction of fluid flow) through any suitable conduits (e.g., pipes, streams, etc.). Common reference numerals refer to common components present in one or more of the Figures, and the description of a particular component is generally applicable across respective Figures wherein the component is present, expect as otherwise indicated herein.

[0030] In an aspect, a process for producing HPA as disclosed herein can comprise a step of contacting an aqueous formaldehyde (FA) solution 11 and a solution of trialkylamine (TAA) in isobutyraldehyde (IB A) 21 to form the HPA reactant mixture 31; wherein the HPA reactant mixture 31 can be characterized by an P3A to FA mole ratio of from about 1 : 1 to about 1.2: 1, alternatively from about 1 : 1 to about 1.1: 1, alternatively from about 1 : 1 to about 1.05: 1, alternatively from about 1: 1 to about 1.02: 1, or alternatively about 1 : 1. As will be appreciated by one of skill in the art, and with the help of this disclosure, and without wishing to be limited by theory, having the P3A to FA mole ratio approaching 1 : 1, without an excess of FA in the HPA reactor 100 minimizes the use of FA, as well as reduces or eliminates the need to recover unconverted FA downstream of the HPA reactor 100

[0031] In an aspect, the aqueous FA solution 11 can comprise FA in the amount of from about 30 wt.% to about 40 wt.%, alternatively from about 32 wt.% to about 39 wt.%, alternatively from about 36.5 wt.% to about 38 wt.%, or alternatively about 37 wt.%, based on the total weight of the aqueous FA solution 11. The aqueous FA solution 11 can further comprise methanol in the amount of from about 5 wt.% to about 20 wt.%, alternatively from about 7.5 wt.% to about 17.5 wt.%, or alternatively from about 10 wt.% to about 15 wt.%, based on the total weight of the aqueous FA solution 11. As will be appreciated by one of skill in the art, and with the help of this disclosure, and without wishing to be limited by theory, methanol can be added to FA aqueous solutions as a stabilizer, for example to prevent oligomerization and/or polymerization of FA.

[0032] The aqueous FA solution 11 can generally be stored in the reagent container 10. The pump 15 can be used for conveying the aqueous FA solution 11 from the reagent container 10 to the T-joint 30, or alternatively to the HPA reactor 100; for example via check valve 19. The flow meter 16 can monitor the flow of the aqueous FA solution 11 to the T-joint 30, or alternatively to the HPA reactor 100. The temperature sensor 17 and/or the pressure sensor 18 can optionally monitor the temperature and/or the pressure, respectively, of the aqueous FA solution 11.

[0033] In an aspect, the solution of TAA in IB A 21 can comprise TAA in the amount of from about 0.01 mol% to about 0.1 mol%, alternatively from about 0.02 mol% to about 0.08 mol%, alternatively from about 0.03 mol% to about 0.05 mol%, or alternatively about 0.04 mol%. As will be appreciated by one of skill in the art, and with the help of this disclosure, the use of a small amount of TAA in the HPA reactant mixture 31 can reduce the need for an extensive separation and recovery process of TAA downstream of the HPA reactor 100. The TAA can comprise trimethylamine (TMA) and/or triethylamine (TEA).

[0034] The solution of TAA in IBA 21 can generally be stored in the reagent container 20. The pump 25 can be used for conveying the solution of TAA in IBA 21 from the reagent container 20 to the T-joint 30, or alternatively to the HPA reactor 100; for example via check valve 29. The flow meter 26 can monitor the flow of the solution of TAA in IBA 21 to the T-joint 30, or alternatively to the HPA reactor 100. The temperature sensor 27 and/or the pressure sensor 28 can optionally monitor the temperature and/or the pressure, respectively, of the solution of TAA in IBA 21.

[0035] In some aspects, for example as depicted in the configuration of Figure 1A, the aqueous FA solution 11 (e.g., aqueous FA phase) and the solution of TAA in IBA 21 (e.g., organic IBA phase) can be contacted upstream of the HPA reactor 100, for example via the T-joint 30. In such aspects, the process for producing HPA as disclosed herein excludes the use of a device (e.g., a static mixer and/or a dynamic mixer) for mixing the HPA reactant mixture 31 upstream of the HPA reactor 100. As will be appreciated by one of skill in the art, and with the help of this disclosure, the T-joint 30 allows for the aqueous FA solution 11 and the solution of TAA in IBA 21 to contact each other. Further, and as will be appreciated by one of skill in the art, and with the help of this disclosure, the aqueous FA phase (e.g., aqueous FA solution 11) and the organic IBA phase (e.g., solution of TAA in IBA 21) are generally immiscible; and while flowing into and/or flowing through the same conduit allows for some level of mixing to occur (e.g., owing to flowing profiles into the T-joint 30), the two immiscible liquids require the use of a mixing device (such as a static mixer and/or dynamic mixer) to provide for a mixing of the two phases (e.g., aqueous FA phase and organic IBA phase) effective to promote a cross-aldol condensation reaction between the FA and IBA (e.g., intimate mixing of the aqueous FA phase and organic IBA phase). For purposes of the disclosure herein, the term “immiscible” refers to liquids that display phase separation when contacted with each other. Furthermore, as will be appreciated by one of skill in the art, and with the help of this disclosure, the terms“dynamic mixer,”“dynamic mixing,”“static mixer,” and“static mixing” are known to one of skill in the art. Furthermore, as will be appreciated by one of skill in the art, and with the help of this disclosure, flow in a conduit lacking a mixing device (such as a static mixer and/or dynamic mixer) can produce some degree of radial mixing, however, effective mixing of immiscible liquids cannot be generally achieved without the use of a mixing device, unless impractical lengths of the conduit are used.

[0036] Generally, a static mixer or motionless mixer is a device inserted into a conduit or chamber (e.g., housing, pipe, pipeline, etc.) with the purpose of manipulating one or more fluid streams flowing through the conduit or chamber containing the mixer, thereby intimately mixing the components of the one or more fluid streams. As will be appreciated by one of skill in the art, and with the help of this disclosure, static mixers do not have any moving parts. For purposes of the disclosure herein, the term“static mixing” refers to the type of mixing that a static mixer provides for.

[0037] Generally, a dynamic mixer is mixer that has moving parts (e.g., magnetic stirrer, paddles, etc.) that manipulate one or more fluid streams flowing through the conduit or chamber containing the mixer, thereby intimately mixing the components of the one or more fluid streams. For purposes of the disclosure herein, the term“dynamic mixing” refers to the type of mixing that a dynamic mixer provides for.

[0038] In an aspect, a process for producing HPA as disclosed herein excludes dynamic and/or static mixing of the HPA reactant mixture 31, e.g., dynamic and/or static mixing of the HPA reactant mixture 31 upstream of the HPA reactor 100. For purposes of the disclosure herein, and as will be appreciated by one of skill in the art, and with the help of this disclosure, the T-joint (e.g., T-joint 30) is not considered a static mixer (since it lacks a static mixing device), and as such the T-joint (e.g., T- joint 30) does not provide for the static mixing of the HPA reactant mixture 31, e.g., static mixing of the HPA reactant mixture 31 upstream of the HPA reactor 100. However, the T-joint (e.g., T-joint 30) provides for contacting the aqueous FA solution (e.g., aqueous FA phase) and the solution of TAA in P3A (e.g., organic P3A phase) upstream of the HPA reactor 100. In aspects where the T-joint (e.g., T-joint 30) is used, the aqueous FA solution (e.g., aqueous FA phase) and the solution of TAA in IB A (e.g., organic IB A phase) can contact each other upstream of the HPA reactor 100, and can undergo static mixing within the HPA reactor 100. [0039] In an aspect, a process for producing HPA as disclosed herein excludes dynamic mixing of the HPA reactant mixture 31 within the HPA reactor 100. In an aspect, a process for producing HPA as disclosed herein comprises static mixing of the HPA reactant mixture 31 within the HPA reactor 100

[0040] In other aspects, the aqueous FA solution (e.g., aqueous FA phase) and the solution of TAA in IB A (e.g., organic IB A phase) can be introduced separately to the HPA reactor 100, and allowed to contact each other within the HPA reactor 100. In such aspects, the aqueous FA solution (e.g., aqueous FA phase) and the solution of TAA in IB A (e.g., organic IB A phase) can contact each other and can undergo static mixing within the HPA reactor 100.

[0041] In an aspect, a process for producing HPA as disclosed herein can comprise a step of reacting, via a cross-aldol condensation reaction, the HPA reactant mixture 31 in the continuous flow HPA reactor 100 to produce an HPA product mixture 35; wherein the HPA reactant mixture 31 comprises P3A, FA, and TAA (e.g., TMA and/or TEA); and wherein the HPA product mixture 35 comprises HPA and TAA. Without wishing to be limited by theory, cross-aldol condensation reactions are generally catalyzed by a base, wherein the base enables the formation of an P3A carbanion or enolate that subsequently reacts with the FA via a nucleophilic reaction to form the HPA. Conventionally, bases such as an alkali metal hydroxide and/or an alkaline earth metal hydroxide can be used to catalyze the cross-aldol condensation reaction between P3A and FA.

[0042] In an aspect, a process for producing HPA as disclosed herein excludes the use of an alkali metal hydroxide (e.g., NaOH) and/or an alkaline earth metal hydroxide (e.g., Ca(OH)2) as a base catalyst in the cross-aldol condensation reaction between P3A and FA. In an aspect, a process for producing HPA as disclosed herein excludes the use of NaOH as a base catalyst in the cross-aldol condensation reaction between P3A and FA. As will be appreciated by one of skill in the art, and with the help of this disclosure, the use of alkali metal hydroxides and/or alkaline earth metal hydroxides for catalyzing cross-aldol condensation reactions can disadvantageous^ lead to the formation of high amounts of salts (as opposed to the desired product of the cross-aldol condensation reactions).

[0043] As will be appreciated by one of skill in the art, and with the help of this disclosure, the HPA reactant mixture 31 is a bi-phasic reactant mixture comprising an aqueous phase (e.g., aqueous FA phase, aqueous FA solution 11) and an organic phase (e.g. organic IB A phase, solution of TAA in P3A 21). Further, and as will be appreciated by one of skill in the art, and with the help of this disclosure, the cross-aldol condensation reaction between P3A and FA cannot occur to a meaningful extent while the IB A and the FA are in different phases (e.g., organic phase and aqueous phase, respectively). However, a basic phase-transfer catalyst (PTC) can be used to allow for the transfer of a reagent (e.g., FA) from the aqueous phase into the organic phase, thus enabling the cross-aldol condensation reaction to occur. Furthermore, and as will be appreciated by one of skill in the art, and with the help of this disclosure, and without wishing to be limited by theory, the PTC (e.g., TAA) is not consumed during the reaction.

[0044] In an aspect, the cross-aldol condensation reaction between P3A and FA can be catalyzed by TAA (e.g., TMA and/or TEA). Generally, the cross-aldol condensation reaction between IB A and FA (HCHO) can be represented by equation (1):

I BA HPA

(1)

[0045] Without wishing to be limited by theory, side reactions can take place along with the cross-aldol condensation reaction depicted in equation (1); and such side reactions can produce various by-products, e.g., via Cannizzaro and/or Tischenko type reactions, for example as depicted in Figure 2. As will be appreciated by one of skill in the art, and with the help of this disclosure, byproducts decrease the selectivity towards a desired product (e.g., HPA). Further, and as will be appreciated by one of skill in the art, and with the help of this disclosure, the use of conventional strong base catalysts (e.g., alkali metal hydroxide and/or an alkaline earth metal hydroxide) can increase the formation of various by-products, for example by-products produced via Cannizzaro type reactions.

[0046] In an aspect, the HPA reactor 100 can be characterized by an internal HPA reactor volume and an internal HPA reactor surface area; wherein the ratio of the internal HPA reactor surface area to the internal HPA reactor volume is from about 30 m ¹ to about 4,000 m ¹ , alternatively from about 30 m ¹ to about 500 m ¹ , alternatively from about 1,000 m ¹ to about 4,000 m ¹ , or alternatively from about 500 m ¹ to about 1,000 m ¹ .

[0047] In an aspect, the HPA reactor 100 can comprise any suitable reactor (e.g., any suitable reactor configuration) that can provide for the ratio of the internal HPA reactor surface area to the internal HPA reactor volume of from about 30 m ¹ to about 4,000 m ¹ . For example, the HPA reactor 100 can comprise a static mixer, wherein the static mixer can provide for the ratio of the internal HPA reactor surface area to the internal HPA reactor volume of from about 30 m ¹ to about 4,000 m ¹ . As will be appreciated by one of skill in the art, and with the help of this disclosure, and without wishing to be limited by theory, introducing a static mixer inside a reactor increases the internal reactor surface area (e.g., internal HPA reactor surface area) while decreasing the internal reactor volume (e.g., internal HPA reactor volume), thereby providing for an increased ratio of the internal reactor surface area to the internal reactor volume (e.g., ratio of the internal HPA reactor surface area to the internal HPA reactor volume).

[0048] Nonlimiting examples of reactors suitable for use as the HPA reactor 100 in the present disclosure include a tubular reactor, a jacketed tubular reactor, a shell and tube heat exchanger reactor, a double pipe heat exchanger reactor, a pinched tube reactor, a compact heat exchanger reactor, a micro-reactor, a microchannel reactor, a microfluidic reactor, an advanced-flow reactor, a spinning disk reactor, and the like, or combinations thereof. In some aspects, the HPA reactor 100 can comprise a coiled tubular reactor having a tubular shell and a static mixer disposed therein.

[0049] For example, the HPA reactor 100 can comprise a continuous flow reactor comprising a static mixer, such as the Vapourtec tubular reactor for rapid mixing. As another example, the HPA reactor 100 can comprise a continuous flow reactor, such as the Plantrix ^® industrial flow reactor (e.g., Chemtrix micro-reactor). As yet another example, the HPA reactor 100 can comprise a continuous flow reactor, such as the Coming ^® Advanced-Flow™ reactor.

[0050] In some aspects, the HPA reactor 100 can be characterized by at least one operational parameter selected from the group consisting of a reactor temperature, a reactor pressure, a reactor residence time, and combinations thereof. For example, the HPA reactor 100 can be operated under any suitable operational parameters that can provide for a desired conversion and/or selectivity.

[0051] In an aspect, the HPA reactor 100 can be characterized by any suitable reactor temperature. In an aspect, the HPA reactor 100 can be characterized by a temperature (e.g., reactor temperature) of from about 60 °C to about 99 °C, alternatively from about 90 °C to about 99 °C, alternatively from about 95 °C to about 99 °C, or alternatively from about 98 °C to about 99 °C. Without wishing to be limited by theory, the cross-aldol condensation reaction between P3A and FA as depicted by equation (1) is exothermic in nature, with the heat of reaction being about -60 kJ/mol at 25 °C; which means that the heat of the reaction can increase the reactor temperature. However, in some aspects, and as will be appreciated by one of skill in the art, and with the help of this disclosure, the heat of the reaction might not be sufficient for increasing the reactor temperature to a desired temperature (e.g., heating the reactor to a desired temperature), and supplemental heat can be introduced to the reactor to achieve and/or maintain the desired temperature. Further, in other aspects, and as will be appreciated by one of skill in the art, and with the help of this disclosure, the heat of the reaction might increase the temperature of the reactor above a desired temperature, and heat can be withdrawn from the reactor (e.g., the reactor can be cooled) to achieve and/or maintain the desired temperature.

[0052] The HPA reactor 100 can be operated under any suitable temperature profile that can provide for a desired conversion and/or selectivity. For example, the HPA reactor 100 can be operated under isothermal conditions. In some aspects, the isothermal conditions in the HPA reactor 100 can be provided by external heat exchange or transfer (e.g., the reactor is heated; or the reactor is cooled), which can be direct heat exchange and/or indirect heat exchange. As will be appreciated by one of skill in the art, and with the help of this disclosure, the terms“direct heat exchange” and “indirect heat exchange” are known to one of skill in the art. In other aspects, the isothermal conditions in the HPA reactor 100 can be provided without subjecting the reactor to external heat exchange (e.g., the reactor is not heated; or the reactor is not cooled). Generally, external heat exchange implies an external heat exchange system (e.g., a cooling system; a heating system) that requires energy input and/or output. As will be appreciated by one of skill in the art, and with the help of this disclosure, external heat transfer can also result from heat loss from the reactor owing to radiation heat transfer, conduction heat transfer, convection heat transfer, and the like, or combinations thereof. For example, the reactor can participate in heat exchange with the external environment, such as the air surrounding the reactor (e.g., heat loss to the surrounding, ambient air).

[0053] In some aspects, the HPA reactor 100 could be operated under isothermal conditions by employing a temperature control system as shown in Figure 3.

[0054] For purposes of the disclosure herein, the term“isothermal conditions” refers to process conditions (e.g., operational parameters) that allow for a substantially constant temperature of the reactor (e.g., HPA reactor 100 isothermal temperature) that can be defined as a temperature that varies by less than about + 10 °C, alternatively less than about + 9 °C, alternatively less than about + 8 °C, alternatively less than about + 7 °C, alternatively less than about + 6 °C, alternatively less than about + 5 °C, alternatively less than about + 4 °C, alternatively less than about + 3 °C, alternatively less than about + 2 °C, or alternatively less than about + 1 °C within the reactor.

[0055] Further, for purposes of the disclosure herein, the term“isothermal conditions” refers to process conditions (e.g., HPA reactor 100 operational parameters) effective for providing a desired conversion and/or selectivity, wherein the isothermal conditions comprise a temperature variation of less than about + 10 °C within the reactor.

[0056] The HPA reactor 100 can be operated under any suitable operational parameters that can provide for isothermal conditions.

[0057] As will be appreciated by one of skill in the art, and with the help of this disclosure, and without wishing to be limited by theory, designing a reactor that undergoes heat transfer (whether by heat loss to the environment and/or by external heat exchange) has to account for the following parameters; the reactor ratio of surface area (SA) to volume (V), the heat transfer coefficient (U), as well as the log mean temperature difference (LMTD); and the combinations of these parameters which gives the reactor power density in terms of energy per unit volume: [(U*SA)/(V*LMTD)].

[0058] In an aspect, the HPA reactor 100 can be characterized by any suitable reactor power density that can provide for isothermal conditions within the HPA reactor 100. In an aspect, the HPA reactor 100 can be characterized by a reactor power density of from about 60 kW/m ³ to about 1,500 kW/m ³ , alternatively from about 120 kW/m ³ to about 1,300 kW/m ³ , or alternatively from about 500 kW/m to about 1,300 kW/m . In an aspect, the isothermal conditions within the HPA reactor 100 can be provided by a reactor power density of from about 60 kW/m ³ to about 1,500 kW/m ³ .

[0059] As will be appreciated by one of skill in the art, and with the help of this disclosure, the power density of a reactor is related to the internal reactor surface area (e.g., internal HPA reactor surface area), as well as the internal reactor volume (e.g., internal HPA reactor volume). For example, the reactor (e.g., HPA reactor 100) could have a relatively high internal reactor surface area with the ratio of the internal reactor surface area to the internal reactor volume of from about 1,000 m ¹ to about 4,000 m ¹ , or alternatively a relatively low internal reactor surface area with the ratio of the internal reactor surface area to the internal reactor volume of from about 30 m ¹ to about 500 m ¹ , with the proviso that the reactor power density is maintained in the range of from about 60 kW/m ³ to about 1,500 kW/m ³ . The HPA reactor 100 can be characterized by any suitable internal reactor diameter and/or internal reactor length (e.g., any suitable internal reactor surface area and/or internal reactor volume) that can provide for a reactor power density of from about 60 kW/m ³ to about 1,500 kW/m ³ .

[0060] In an aspect, the HPA reactor 100 can be characterized by any suitable reactor pressure. In an aspect, the HPA reactor 100 can be characterized by a reactor pressure (e.g., reactor pressure measured at the reactor exit or outlet, for example as monitored by the pressure sensor 38) of from about 1 barg to about 15 barg, alternatively from about 6 barg to about 9 barg, or alternatively from about 6 barg to about 8 barg. In an aspect, a process for producing HPA as disclosed herein excludes the use of an inert gas (e.g., nitrogen, argon, helium, etc.) to regulate the pressure in the HPA reactor 100. Generally, the inert gas is inert with respect to the cross-aldol condensation reaction between IBA and FA as depicted by equation (1), e.g., the inert gas does not participate in the cross-aldol condensation reaction between IBA and FA as depicted by equation (1). Conventionally, an inert gas (such as nitrogen) is introduced to the cross-aldol condensation reactor to provide for the desired pressure. However, when an inert gas is used in the cross-aldol condensation reactor, a portion of the FA can reach the inert gas, and thus it can lead to emissions to FA into the environment, which is undesirable.

[0061] In an aspect, the back-pressure regulator 150 can be employed downstream of the HPA reactor 100 to regulate the pressure in the HPA reactor 100. Generally, a back-pressure regulator is a device that maintains a defined pressure upstream of itself (i.e., at its own inlet); when fluid pressure exceeds a target pressure, a back-pressure regulator valve can open more to relieve the excess pressure.

[0062] In an aspect, the HPA reactor 100 can comprise a reactor wall (e.g., a reactor shell) material and/or reactor internals (e.g., static mixer) material, wherein the reactor wall material and/or reactor internals material can comprise any suitable material that provides for operating the HPA reactor 100 at the desired operating conditions, such as a reactor temperature of from about 60 °C to about 99 °C and/or a reactor pressure of from about 1 barg to about 15 barg. In an aspect, the reactor wall (e.g., a reactor shell) material and/or reactor internals (e.g., static mixer) material can comprise a perfluoroalkoxy (PFA) polymer, a metal, an alloy, stainless steel, a nickel alloy, a chromium alloy, a molybdenum alloy, and the like, or combinations thereof.

[0063] In an aspect, the HPA reactor 100 can be characterized by any suitable residence time. The HPA reactor 100 can be characterized by a residence time of from about 1 minute to about 15 minutes, alternatively from about 6 minutes to about 12 minutes, or alternatively from about 8 minutes to about 10 minutes. Generally, the residence time of a reactor refers to the average amount of time that it takes for a compound (e.g., a molecule of that compound) to travel through the reactor.

[0064] As will be appreciated by one of skill in the art, and with the help of this disclosure, a variety of factors have to be accounted for while designing a reactor for a particular application. For example, and without wishing to be limited by theory, selectivity to a desired product is inversely proportional to residence time and temperature. As another example, and without wishing to be limited by theory, a desired residence time can be achieved by varying the diameter and/or the length of the reactor; however, with the proviso that the reactor power density is maintained in the range of from about 60 kW/m ³ to about 1,500 kW/m ³ . As yet another example, and without wishing to be limited by theory, as residence time increases, conversion increases under isothermal conditions (e.g., a temperature variation of less than about + 10 °C within the reactor).

[0065] In an aspect, a process for producing HPA as disclosed herein can comprise a step of recovering at least a portion of the HPA and optionally at least a portion of the TAA from the HPA product mixture 35. The HPA product mixture 35 can be recovered from the HPA reactor 100. The flow meter 36 can monitor the flow of the HPA product mixture 35 from the HPA reactor 100. The pressure sensor 38 and optionally the temperature sensor 37 can monitor the pressure and optionally the temperature, respectively, of the HPA product mixture 35. The pressure sensor 38 is upstream of the back-pressure regulator 150.

[0066] In an aspect, at least a portion of the HPA product mixture 35 can be introduced to the HPA product mixture collection unit 200.

[0067] In some aspects, at least a portion of the HPA product mixture can be conveyed from the HPA product mixture collection unit to an HPA product mixture separating unit to yield an HPA product, wherein the HPA product comprises HPA, and optionally neopentyl glycol (NPG, 2,2- dimethyl- 1 ,3 -propanediol).

[0068] In other aspects, for example as depicted in the configuration of Figure IB, at least a portion of the HPA product mixture 35 can be introduced to HPA product mixture separating unit 250 to yield an HPA solution 40 and a TAA solution 45; wherein the HPA solution 40 comprises HPA, water, methanol, and optionally NPG; and wherein the TAA solution 45 comprises TAA, and methanol.

[0069] In an aspect, the HPA product mixture separating unit 250 can comprise any suitable separating unit configured for the recovery of the HPA solution 40 and the TAA solution 45. For example, the HPA product mixture separating unit 250 can employ distillation, rectification, extractive distillation, and the like, or combinations thereof. The HPA product mixture separating unit 250 can comprise a distillation column, a rectification column, etc.

[0070] In an aspect, a process for producing HPA as disclosed herein can comprise a one-step distillation of at least a portion of the HPA product mixture 35 to yield the HPA solution 40 and the TAA solution 45.

[0071] In an aspect, at least a portion of the HPA solution 40 can be further used for NPG synthesis, for example via a reduction reaction as represented by equation (2):

HPA

NPG (2)

As will be appreciated by one of skill in the art, and with the help of disclosure, in aspects where the HPA is used for NPG synthesis, having NPG already in the HPA solution 40 is advantageous, as less HPA has to be converted to the final desired product, NPG. The HPA solution 40 can be subjected to hydrogenation to produce NPG without any further processing.

[0072] In an aspect, the HPA reactor 100 can be characterized by a selectivity to HPA and NPG of equal to or greater than about 95%, alternatively equal to or greater than about 96%, alternatively equal to or greater than about 98%, alternatively from about 95% to about 99.9%, alternatively from about 98% to about 99.9%, or alternatively from about 98% to about 99%. Generally, a selectivity to a desired product or products refers to how much desired carbon product was formed divided by the total carbon products formed, both desired and undesired. For purposes of the disclosure herein, the selectivity to a desired product is a % selectivity based on moles converted into the desired product.

[0073] In an aspect, the HPA reactor 100 can be characterized by an IBA conversion of equal to or greater than about 90%, alternatively equal to or greater than about 92%, alternatively equal to or greater than about 95%, alternatively equal to or greater than about 97%, or alternatively equal to or greater than about 99%. Generally, a conversion of a reagent or reactant refers to the percentage (usually mol%) of reagent that reacted to both undesired and desired products, based on the total amount (e.g., moles) of reagent present before any reaction took place. For purposes of the disclosure herein, the conversion of a reagent is a % conversion based on moles converted. [0074] In an aspect, a process for producing HPA as disclosed herein can comprise recycling at least a portion of the TAA solution 45 to the HPA reactor 100, for example via the HPA reactant mixture 31. In aspects where the conversion of FA and/or IBA is incomplete (e.g., less than 100% conversion), the TAA solution 45 can further comprise FA and/or IBA, respectively.

[0075] As will be appreciated by one of skill in the art, and with the help of this disclosure, while TAA is not consumed during the cross-aldol condensation reaction as depicted in reaction (1), some TAA can be lost during the recovery process, and as such supplemental TAA may be necessary to be combined with the recovered TAA to provide for the necessary amount of TAA in the HPA reactor 100

[0076] In an aspect, a process for producing HPA as disclosed herein can comprise (a) contacting an aqueous FA solution and a solution of TEA in IBA to form the HPA reactant mixture; wherein the FA is present in the aqueous FA solution in the amount of from about 36.5 wt.% to about 38 wt.%, based on the total weight of the aqueous FA solution; wherein the aqueous FA solution comprises from about 10 wt.% to about 15 wt.% methanol, based on the total weight of the aqueous FA solution; wherein TEA is present in the solution of TEA in IBA in the amount of from about 0.03 mol% to about 0.05 mol%; and wherein the HPA reactant mixture is characterized by an IBA to FA mole ratio of about 1 : 1; (b) feeding at least a portion of the HPA reactant mixture to a continuous flow HPA reactor; and reacting under isothermal conditions, via a cross-aldol condensation reaction, at least a portion of the HPA reactant mixture in the HPA reactor to produce an HPA product mixture; wherein the HPA reactor is characterized by a reactor temperature of from about 90 °C to about 99 °C; wherein the HPA reactor is characterized by a reactor pressure of from about 6 barg to about 8 barg; wherein the HPA reactor is characterized by a reactor residence time of from about 6 minutes to about 12 minutes; wherein the isothermal conditions comprise a reactor temperature variation of less than about + 1 °C; wherein the HPA reactor is characterized by an internal HPA reactor volume and an internal HPA reactor surface area; wherein the ratio of the internal HPA reactor surface area to the internal HPA reactor volume is from about 30 m ¹ to about 4,000 m ¹ ; wherein the HPA reactor optionally comprises a static mixer; wherein the HPA product mixture comprises HPA, water, methanol, TEA, and optionally NPG; (c) one step-distilling of at least a portion of the HPA product mixture to yield an HPA solution and a TEA solution; wherein the HPA solution comprises HPA, water, methanol, and optionally NPG; and wherein the TEA solution comprises TEA, methanol, and optionally unconverted IBA and/or unconverted FA; (d) optionally recycling at least a portion of the TEA solution to the continuous flow HPA reactor; and (e) optionally hydrogenating at least a portion of the HPA solution to yield NPG, for example as represented by equation (2). In such aspect, the HPA reactor can be characterized by an IBA conversion of equal to or greater than about 95%; and/or by a selectivity to HPA and NPG of equal to or greater than about 98%.

[0077] In an aspect, a process for producing HPA as disclosed herein can advantageously display improvements in one or more process characteristics when compared to conventional processes for the production of HPA. Conventional processes for the production of HPA can employ batch synthesis methods, wherein the reaction time can be about 90-300 minutes (with an initial 30 minutes time period for reactant addition), to account for slow interphase mass transfer and temperature control. The 30 minutes time period for reactant addition can provide for near isothermal conditions of reaction, by controlling the heat generation rate via slow reagent addition. Batch reactions for the production of HPA, as well as continuous stirred tank reactors (CSTRs) that utilize an inert gas blanket can further increase emissions of FA during pressure release, as compared to the process for producing HPA as disclosed herein. Further, CSTRs display increased back-mixing, which leads to decreased HPA selectivity (e.g., increased formation of impurities or by-products). Conventional processes for the production of HPA generally utilize strong base catalysts, and the catalyst may or may not be recycled. Further, strong base catalysts are poisons for the catalyst used in the reduction (e.g., hydrogenation) of HPA to NPG. Further, strong base catalysts promote the formation of undesired by-products via cross Cannizzaro/Tischenko side reactions, for example as displayed in Figure 4. Conventional processes for the production of HPA generally employ excess reagents, which in turn requires a complex HPA recovery process. Generally, the cross-aldol condensation reaction state for the production of HPA is difficult to control in conventional processes for the production of HPA, with the cross-aldol condensation reaction being accompanied by a variety of side reactions, wherein HPA can easily oligomerize or polymerize to form undesired side products, for example as represented by equation (3) that depicts the formation of a dimer:

Molecular Weight: 102.13

Heat/solvent

Molecular Weight: 204.27

HPA

(3) [0078] In an aspect, a process for producing HPA as disclosed herein can advantageously employ a static mixer micro-channel flow reactor (e.g., coiled tubular reactor having a tubular shell and a static mixer disposed therein) using cross-aldol condensation of IBA and aqueous FA solution in the presence of an amine catalyst. The process for producing HPA as disclosed herein can advantageously reduce the use of excess reactants and lower side reactions, as well as result in higher selectivity (e.g., greater than about 98%) and higher conversion (e.g., greater than about 95%) when compared to the selectivity and conversion, respectively, of conventional processes for the production of HPA. Further, the process for producing HPA as disclosed herein can advantageously employ reagents in a stoichiometric ratio of IBA to FA of 1 : 1 (i.e., no excess reagents), with a small amount of catalyst (e.g., about 0.04 mol% TEA). Furthermore, the process for producing HPA as disclosed herein can advantageously complete the cross-aldol condensation reaction in about 10-12 minutes residence time in flow reactor, thus resulting in higher throughput (at lower energy input) and better selectivity, when compared to the throughput and selectivity, respectively, of conventional processes for the production of HPA. Consequently, the process for producing HPA as disclosed herein can advantageously be safer, as well as a more energy efficient process with a smaller equipment footprint, when compared to conventional processes for the production of HPA.

[0079] In an aspect, a process for producing HPA as disclosed herein can advantageously employ a continuous flow reactor that has about a hundred times larger surface area to volume ratio than a standard stirred reactor. The large surface area to volume ratio of the continuous flow reactors as disclosed herein can provide for isothermal reaction conditions. Further, a high heat transfer rate across reactor walls can advantageously maintain isothermal conditions in the continuous flow reactor. The internals of such continuous flow reactor can be designed to promote enhanced mass transfer (e.g., about 50x) and enhanced heat transfer (e.g., about 150x) capacity (e.g., no high concentration spots, as well as no“dead” zones/limiting reactants zones; and no hot spots formation) and to achieve about instantaneous mixing of the biphasic reactants, e.g., aqueous FA solution and IBA containing TEA catalyst. Efficient heat transfer and about isothermal conditions in the continuous flow reactor and can advantageously afford to run the reaction at higher temperatures (e.g., 90-100 °C). Further, the reaction time can be advantageously reduced from about 90 minutes in a stirred reactor to less than about 10-12 minutes (e.g., narrow residence time distribution) in the continuous flow reactors as disclosed herein, thereby resulting in a process for producing HPA as disclosed herein with higher productivity and better selectivity when compared to the productivity and selectivity, respectively, of conventional processes for the production of HPA. Furthermore, the continuous flow reactors as disclosed herein can advantageously provide for very little to no back- mixing, which in turn leads to less by-products formation.

[0080] In an aspect, a process for producing HPA as disclosed herein employs a continuous flow reactor, which can advantageously increase safety, process performance, as well as it can be easily automated.

[0081] In an aspect, a process for producing HPA as disclosed herein can advantageously employ a one-step distillation process to recover HPA from the HPA product mixture, wherein the recovered HPA can be subjected to hydrogenation for NPG production without the need for further processing. By contrast, conventional processes for HPA production can suffer from low IBA conversion, which is disadvantageous. For example, at IBA conversions lower than 70%, the mixture inside the reactor can become a viscous mass, which would hinder the recovery of HPA. Additional advantages of the processes for producing HPA as disclosed herein can be apparent to one of skill in the art viewing this disclosure.

EXAMPLES

[0082] The subject matter having been generally described, the following examples are given as particular embodiments of the disclosure and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification of the claims to follow in any manner.

EXAMPLE 1

[0083] Hydroxypivaldehyde (HPA, 3 -hydroxy-2, 2-dim ethylpropanal) synthesis reactions were carried out as disclosed herein, for example by using the HPA production system 1000 of Figure 1A. The reactor was from Vapourtec: a coiled tubular static mixer continuous flow reactor having 3.2 mm tube diameter and 2.48 m length (20 ml volume) was used to perform the cross-aldol condensation reaction for the formation of HPA. The reactor was characterized by a surface area to volume ratio of about 2420-2500 m ¹ . The reactor was characterized by a power density of from about 600 kW/m ³ to about 900 kW/m ³ . The reaction conditions were: temperatures of 95 °C to 100 °C; pressures of 6 barg to 10 barg; and residence times of 6 minutes to 12 minutes.

[0084] Figure 5 shows one set of experimental conditions used for running the cross-aldol condensation reaction for the formation of HPA, as well as the sample region from steady-state flow. As shown in Figure 5, a molar ratio of 1 : 1 was maintained for FA (A) and IBA + TEA solution (B), along with a reactor temperature of 90 °C and a residence time of 10 minutes. A 4 ml sample was collected from the steady-state region indicated in Figure 5. The reactor was a static mixer continuous flow reactor with a volume of 20 ml.

[0085] The parameters displayed in Figure 5 were varied in different experiments to investigate the effect of various reaction parameters on the cross-aldol condensation reaction for the formation of HPA. The residence times were changed in the flow system by changing flow rates. The data in Tables 1, 2, and 3 is from three different experiments performed at different total flows, while maintaining all other process conditions and parameters same. The data in Table 1 displays flow rates, residence time, GBA conversion and HPA+NPG selectivity at 90 °C. Similarly, the data in Table 2 was collected at 95 °C, and the data in Table 3 was collected at 99 °C. About 95% conversion of IB A at 99 °C was achieved in 12 minutes residence time with >98% selectivity towards HPA.

Table 1

Table 2

Table 3

EXAMPLE 2

[0086] A comparative batch reaction for the formation of HPA was performed as follows. The batch reaction was performed at 90 °C under reflux conditions at atmospheric pressure with an IB A/FA mole ratio of 1 : 1. The graph in Figure 6 shows the conversion of IB A as a function of reaction time. A typical batch reaction was performed as outlined in Tables 4 and 5 below.

Table 4

Table 5

[0087] Figure 7 further compares the conversion of IB A as a function of reaction time in a batch reaction versus continuous flow reactions. Conventional HPA synthesis reactions generally display about 85% IBA conversion and HPA+NPG selectivity of about 91.8%. In the batch reaction in Figure 7, after 340 min about 96% selectivity was achieved. Further, for the continuous flow reactions in Figure 7, greater than about 98% HPA+NPG selectivity was achieved. As will be appreciated by one of skill in the art, and with the help of this disclosure, a higher selectivity towards HPA+NPG could help eliminate purification steps needed to purify HPA prior to further use, for example prior to an NPG production process.

[0088] The selectivity to HPA+NPG for the continuous flow reactions in Figure 7 is displayed in Table 6.

Table 6

[0089] Further, Table 7 displays a comparison between the cross-aldol condensation reactions for the formation of HPA performed with the continuous flow reactor as disclosed herein as compared with conventional processes of HPA production.

Table 7

[0090] As conversion and selectivity towards product is higher, raw material requirement per kg of product is less compared with conventional systems #1 and #2.

EXAMPLE 3

[0091] The continuous flow reactor for the cross-aldol condensation reactions for HP A production could be scaled up for industrial production of HPA.

[0092] For example, in order to get a production capacity of 20 KTA HPA plant, a double pipe heat exchanger reactor or a pinched tube reactor of 4 inch tube diameter and 120 m length with a power density parameter of 800 kW/m ³ to 1,000 kW/m ³ could be used. Double pipe heat exchanger can have one or more static mixers disposed therein. Pinched tube reactors do not require a static mixer.

[0093] As another example, in order to get a production capacity of 20 KTA HPA plant, about 320 tubes having about 1 inch diameter and 6 m length could be used, in the format of a shell and tube heat exchanger reactor with a static mixer in tube, which could result in a smaller equipment footprint.

[0094] The product (HPA +NPG) selectivity could reach equal to or greater than about 98.9%, which would in turn decrease downstream equipment requirement (e.g., extractors, distillation columns, as well as eliminate the conventional multi-stage rectification after hydrogenation of HPA to NPG).

[0095] For the purpose of any U.S. national stage filing from this application, all publications and patents mentioned in this disclosure are incorporated herein by reference in their entireties, for the purpose of describing and disclosing the constructs and methodologies described in those publications, which might be used in connection with the methods of this disclosure. Any publications and patents discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention.

[0096] In any application before the United States Patent and Trademark Office, the Abstract of this application is provided for the purpose of satisfying the requirements of 37 C.F.R. § 1.72 and the purpose stated in 37 C.F.R. § 1.72(b)“to enable the United States Patent and Trademark Office and the public generally to determine quickly from a cursory inspection the nature and gist of the technical disclosure.” Therefore, the Abstract of this application is not intended to be used to construe the scope of the claims or to limit the scope of the subject matter that is disclosed herein. Moreover, any headings that can be employed herein are also not intended to be used to construe the scope of the claims or to limit the scope of the subject matter that is disclosed herein. Any use of the past tense to describe an example otherwise indicated as constructive or prophetic is not intended to reflect that the constructive or prophetic example has actually been carried out.

[0097] While embodiments of the disclosure have been shown and described, modifications thereof can be made without departing from the spirit and teachings of the invention. The embodiments and examples described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention.

[0098] Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are a further description and are an addition to the detailed description of the present invention. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference.