WO2020260237A1

WO2020260237A1 - A method of preparing ethylbenzene

Info

Publication number: WO2020260237A1
Application number: PCT/EP2020/067426
Authority: WO
Inventors: Sandeep Negi; Kartick Chandra Mondal; Sonal Sant SANT; Vikram BHIDE; Hyacinth Mary Bastian; Puneet Gupta
Original assignee: Shell Internationale Research Maatschappij BV; Shell Oil Co
Current assignee: Shell Internationale Research Maatschappij BV; Shell USA Inc
Priority date: 2019-06-28
Filing date: 2020-06-23
Publication date: 2020-12-30
Anticipated expiration: 2021-12-28

Abstract

The present invention provides a process for making ethylbenzene including reacting toluene with a C1 source in the presence of a zeolite catalyst in one or more reactor zones to form a product comprising ethylbenzene and maintaining a molar ratio of toluene:C1 source ranging from 3:1 to 30:1 throughout the one or more reactor zones. The reacting is performed at a pressure of from 1 to 10 bara and the partial pressure of the C1 source ranges from about 0.04 to about 0.5 bara.

Description

A METHOD OF PREPARING ETHYLBENZENE

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a method of preparing ethylbenzene by reaction of toluene and methanol. Various methods of preparing ethylbenzene by reaction of toluene and methanol are known in the art.

[0002] Alkyl styrenes, including ethylbenzene, are important starting materials for the organic chemical industry, mainly used for producing polystyrenes, ABS resins, SBR rubbers, and unsaturated resins. Up to now, styrene-based resins rank worldwide only after PEs and PVCs in terms of production.

[0003] The prior art has developed a process wherein (alkyl) styrenes are directly alksynthesized by alkylating alkyl benzenes (e.g. toluene) on the side chain in the presence of an alkaline catalyst with an alkylating agent (e.g. methanol), which has been identified as a promising production process due to low cost, low consumption of energy, little environmental pollution, simple procedure and easy availability of the starting materials, and drawn more and more attention. However, such processes have been characterized by having very low yields in addition to having very low selectivity to styrene and ethylbenzene.

[0004] From the standpoint of economic value, it is noted that as much alkylating agent as possible be converted into ethyl benzene and styrene by reacting with toluene, rather than unnecessarily consumed by the decomposition into CO and ¾. When other alkyl benzenes or alkylating agents (e.g. dimethoxy methane) are to be used for the alkylating process, there is a similar concern.

[0005] One example of preparing ethylbenzene by reaction of toluene and methanol is disclosed in US4371729. According to US4371729, ethylbenzene is prepared by bringing a gaseous mixture of methanol and toluene in contact with a catalyst composed of a carrier of activated carbon or alumina supporting potassium and either one or both of zinc and copper. According to Examples of US4371729, a molar ratio of toluene/methanol of 3.95/1 was passed through a reaction tube filled with catalyst and kept at a temperature of 425 °C.

[0006] There still exists a need for an alkylating process for alkyl benzenes, which is capable of effectively inhibiting decomposition of the alkylating agent (especially methanol), improving the utilization efficiency of the alkylating agent including high yield and selectivity to ethylbenzene. SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to overcome or minimize one or more of the above problems. The present invention provides a process for making ethylbenzene including reacting toluene with a C1 source in the presence of a zeolite catalyst in one or more reactor zones to form a product comprising ethylbenzene and maintaining a molar ratio of toluene: C1 source ranging from 3: 1 to 30:1 throughout the one or more reactor zones. The reacting is performed at a pressure of from 1 to 10 bara and the partial pressure of the C1 source ranges from about 0.04 to about 0.5 bara.

DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a flow diagram showing an aspect of an exemplary, but non-limiting, embodiment of a process described herein.

DETAILED DESCRIPTION

[0009] The following description of the variations is merely illustrative in nature and is in no way intended to limit the scope of the disclosure, its application, or uses. The description and examples are presented herein solely for the purpose of illustrating the various embodiments of the disclosure and should not be construed as a limitation to the scope and applicability of the disclosure.

[0010] The terminology and phraseology, used herein, is for descriptive purposes and should not be construed as limiting in scope. Language such as“including,”“comprising,” “having,”“containing,” or“involving,” and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited.

[0011] Also, as used herein, any references to“one embodiment” or“an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily referring to the same embodiment.

[0012] The inventors have found that during the reaction of toluene and a C1 source to produce ethylbenzene and styrene, increased ethyl benzene selectivity may be achieved by manipulating the toluene: C1 source molar ratio, the reactor pressure and the the partial pressure of the C1 source push the C1 source based selectivity to ethyl benzene to greater than 60%. [0013] Embodiments of the invention provide a process for making ethylbenzene by reacting toluene with a C1 source in the presence of a zeolite catalyst in one or more reactor zones to form a product comprising ethylbenzene. In the reactor zones, a molar ratio of toluene:C1 source is maintained between from 3:1 to 30: 1 throughout the one or more reactor zones, reactor zones are at a pressure ranging from 1 to 10 bara; and the partial pressure of the C1 source is maintained in the range from about 0.04 to about 0.5 bara. Within these reaction conditions, there is greater than 90% methanol conversion, greater than 95% methanol conversion, greater than 98% methanol conversion, greater than 99% methanol conversion or methanol based selectivity to ethyl benzene being greater than 60%.

[0014] Toluene is reacted with a carbon source, which can be referred to as a C1 source, capable of coupling with toluene to form ethylbenzene or styrene. In an embodiment, the C1 source includes methanol, formaldehyde, formalin, trioxane, methylformcel, paraformaldehyde and methylal and combinations thereof. In a preferred embodiment, the C1 source is methanol.

[0015] In some embodiments, the reaction has a 1:1 molar ratio of toluene to the C1 source, the ratio of the feedstream is not limited within the present invention and can vary depending on operating conditions and the efficiency of the reaction system. If excess toluene or C1 source is fed to the reaction zone, the unreacted portion can be subsequently separated and recycled back into the process. In alternate embodiments, the molar ratio of toluene:C1 source can range between from 100:1 to 1:100, from 50:1 to 1:50; from 20:1 to 1:20; from 10:1 to 1:10; from 5:1 to 1:5; from 2:1 to 1:2, and from 3: 1 to 30:1. In some embodiments, the ratio of toluene:methanol can range between from 50: 1 to 1:50; from 20:1 to 1:20; from 10:1 to 1:10; from 5:1 to 1:5; from 2:1 to 1:2, and from 3: 1 to 30:1. According to an especially preferred embodiment according to the present invention, the molar ratio for toluene: C1 source in all reaction zones is maintained above 3:1, preferably above 10:1, more preferably above 15:1. Typically, a molar ratio for toluene: C1 source is maintained below 30:1 throughout the reaction zones.

[0016] The reaction conditions can vary depending on the feedstream composition and the desired composition of the product streams. In some embodiments, reactions occur at elevated temperatures and pressures and occur in the presence of a basic catalyst system.

[0017] The person skilled in the art will readily understand that the basic zeolite-based catalyst can be varied widely. As the person skilled in the art is familiar with zeolite-based catalysts, this is not further discussed here in detail. A zeolite is generally a porous, crystalline alumino-silicate, and it can be formed either naturally or synthetically. The inclusion of various metal oxides can lead to several different zeolite compositions. Furthermore, zeolite is commonly altered through a variety of methods to adjust characteristics such as pore size, structure, activity, acidity, and silica/alumina molar ratio. Thus, a number of different forms of zeolite are available.

[0018] Zeolite materials suitable for this invention may include silicate-based zeolites or amorphous compounds such as faujasites, mordenites, etc. Silicate-based zeolites are made of alternating Si04- and MOx tetrahedra, where M is an element selected from the Groups 1 through 16 of the Periodic Table (new IUPAC). These types of zeolites have 4, 6, 8, 10, or 12- membered oxygen ring channels. According to a preferred embodiment of the present invention, the zeolite-based catalyst comprises a zeolite selected from an X-type zeolite, a Y- type zeolite or a combination thereof.

[0019] Another method of altering zeolites is by ion-exchange. Ion exchange may be performed by conventional ion exchange methods in which sodium, hydrogen, or other inorganic cations that may be typically present in a substrate are at least partially replaced via a fluid solution. According to a preferred embodiment of the present invention, the zeolite- based catalyst has been ion-exchanged with an alkali metal, preferably selected from the group consisting of Na, K, Cs, Rb and Fr and a combination thereof.

[0020] Furthermore, the zeolites for use according to the present invention may include one or more metal oxides, such as Cs20. The metal oxide(s) may be present within the structure of the zeolite, or support. The metal oxide present within the structure of the zeolite may be loosely contained within the structure of the zeolite. In one embodiment, the metal oxide is not physically attached to the zeolite, but physically trapped within the zeolite cage structure, which can be referred to herein as‘occluded metal oxide.’ The occluded metal oxide present in the structure of the zeolite can electrically influence the zeolite and alter its catalytic abilities.

[0021] The prepared catalyst can be ground, pressed, sieved, shaped and/or otherwise processed into a form suitable for loading into a reactor. The reactor can be any type known in the art which uses catalyst particles, such as a fixed bed, fluidized bed, or swing bed reactor. Optionally, an inert material, such as quartz chips, can be used to support the catalyst bed and to place the catalyst within the bed. Depending on the catalyst, a pre-treatment of the catalyst may, or may not, be necessary. For the pre-treatment, the reactor can be heated to elevated temperatures (i.e, the desired reaction temperature), such as 200° C to 900° C with an inert gas flow, such as 100 mL/min, and held at these conditions for a length of time, such as 1 to 3 hours. Then, the reactor can be brought to the operating temperature of the reactor, for example 300° C to 550° C, or optionally down to atmospheric or other desired temperature. The reactor can be kept under an inert purge, such as under a nitrogen or helium purge.

[0022] The temperature can range in a non-limiting example from 250° C to 750° C, from 300° C to 500° C, from 325° C to 450° C, preferably below 400° C. The pressure can range in a non-limiting example from 1 bara to 20 bara, from 1 bara to 10 bara, from 1 bara to 5 bara. In some embodiments, the partial pressure of MeOH about 0.04 bara to about 0.5 bara, from about 0.06 bara to about 0.3 bara, and from 0.9 bara to 0.15 bara.

[0023] Although the method according to the present invention is not limited to a certain space velocity, it is preferred that the reaction is performed at a space velocity (WHSV) of from 0.1 to 10.0 h-1, preferably below 5.0 h-1, more preferably below 3.0 h-1, even more preferably below 2.0 h-1, yet even more preferably below 1.0 h-1. The person skilled in the art is aware with how to determine or calculate the space velocity. According to the present invention the space velocity has been based on standard calculations (mass flow rate of feed/reactant pass through per gram of catalyst per hour).

[0024] Based on the above conditions, the ethylbenzene selectivity based on methanol is above 40%, preferably above 50%, more preferably above 60%. This high ethylbenzene selectivity based on methanol reflects that the methanol is converted to the desired product rather than decomposing into CO and H2.

[0025] Furthermore, it is preferred according to the present invention that the ethylbenzene-enriched product mixture obtained comprises at least 30 mol% ethylbenzene, preferably at least 10 mol%. Typically, the ethylbenzene-enriched mixture comprises at most 4 mol% ethylbenzene.

[0026] Figure 1 is a simplified flow chart of an embodiment of the ethylbenzene process 100 discussed above. A C1 source containing feed stream 102 and a feed stream of toluene 104 are fed into reactor 105 to produce ethylbenzene/styrene.

[0027] Embodiments of reactor 105 that can be used with the present invention can include, but not limited to: fixed bed reactors; fluid bed reactors; and entrained bed reactors. Reactors capable of the elevated temperature and pressure as described herein, and capable of enabling contact of the reactants with the catalyst, can be considered within the scope of the present invention. Embodiments of the reactor system may be determined based on the design conditions and throughput, as by one of ordinary skill in the art, and are not meant to be limiting on the scope of the present invention. An example of a suitable reactor can be a fluid bed reactor having catalyst regeneration capabilities. This type of reactor system employing a riser can be modified as needed, for example by insulating or heating the riser if thermal input is needed, or by jacketing the riser with cooling water if thermal dissipation is required. These designs can also be used to replace catalyst while the process is in operation, by withdrawing catalyst from the regeneration vessel from an exit line or adding new catalyst into the system while in operation. In some embodiments, there may one or more reactors 105.

[0028] In another embodiment, the one or more reactors may include one or more catalyst beds 107a, 107b, 107c, 107d and 107e. In the event of multiple beds, an inert material layer can separate each bed. The inert material can comprise any type of inert substance, including quartz. In an embodiment, a reactor includes between 1 and 10 catalyst beds. In a further embodiment, the reactor includes between 2 and 5 catalyst beds. In some embodiments, the C1 source is injected into each catalyst bed and the toluene feed 104 is injected into the bottom of the reactor. In some embodiments, a portion of the C1 source containing feed stream 102 is fed into each of the one or more catalyst beds 107a, 107b, 107c, 107d and 107e.

[0029] In other embodiments, the C1 source 102 and toluene 104 may be injected into a catalyst bed, an inert material layer, or both. In a further embodiment, at least a portion of the C1 source 102 is injected into a catalyst bed(s) and at least a portion of the toluene feed 104 is injected into an inert material layer(s).

[0030] In still other embodiments, the entire C1 source 102 is injected into a catalyst bed(s) and all the toluene feed 104 is injected into an inert material layer(s). In another aspect, at least a portion of the toluene feed 104 is injected into a catalyst bed(s) and at least a portion of the C1 source 102 is injected into an inert material layer(s). In a further aspect, all the toluene feed 104 is injected into a catalyst bed(s) and the entire C1 source 102 is injected into an inert material layer(s).

[0031] The product 106 of the reactor 105 may then be sent to an optional separation unit 109 where a recycle stream 108 including any unreacted C1 source, unreacted methanol, unreacted formaldehyde is separated from the ethylbenzene 110 and the styrene 112. The recycle stream 108 can be recycled back into the reactor 105. The styrene product stream 112 can be removed from the separation unit 109 and subjected to further treatment or processing if desired.

[0032] Hereinafter the invention will be further illustrated by the following non-limiting examples.

Examples [0033] A toluene and methanol containing mixture was prepared by mixing 20 moles of toluene (Sigma Aldrich) with 1 mol of methanol (Sigma Aldrich). A NaX zeolite was sourced from (Sigma Aldrich) and the“Na” form was exchanged with“Cs” from a CsOH precursor by a liquid ion exchange method, wherein the molecular sieve and the alkali metal ion source contact each other in the presence of a solvent (i.e., water) so as to conduct the ion exchange. The content of the alkali metal ion (i.e., Cs ion) in the aqueous solution may be between 0.5 - 2.5 mol/L. The ion-exchange can be conducted at temperatures between 50-90 °C, for between 1-3 hours, and the weight ratio of the molecular sieve to the aqueous solution for each contacting could be 1:5 to 1:10. The contacting could be conducted for one or more times depending upon the require loading of alkali metals.

[0034] Table 1 below lists the reaction conditions and the results of the reaction. As can be seen from the Examples, the present invention surprisingly provides a method for preparing ethylbenzene by reaction of toluene and methanol, wherein a relatively high ethylbenzene selectivity (higher than 40% based on methanol) can be obtained. The high methanol conversion helps to reduce costs for downstream separation processes by eliminating the need for typically expensive 3-phase separation processes.

[0035] Examples 1-5 demonstrate the effect of the temperature at the same WHSV. Example 1 is comparative. It is hypothesized that ethylbenzene (EB) selectivity based on toluene conversion improves with temperature, as shown below EB selectivity based on methanol conversion increases between 375 °C to 390 °C temp and decreases thereafter.

[0036] Examples 4-11 demonstrate the effect of WHSV at different temperatures. It is hypothesized that EB selectivity based on toluene & methanol conversion improve with more residence time (lower space velocity). Dimethyl ether (DME) is observed as a major by-product at higher space velocity.

[0037] Examples 12-16 demonstrate the effect of the molar toluene/methanol ratio at different temperatures. Examples 15 and 16 are comparative. It is hypothesized that EB selectivity based on toluene & methanol conversion improves with higher T/M molar ratio. DME is observed as a major by-product from methanol at lower T/M ratio.

[0038] Examples 17-22 show the effect of the methanol partial pressure at different temperatures. Higher ethylbenzene (and styrene) selectivity is observed based on toluene & methanol conversion. DME is observed as major methanol decomposition by-product other than CO at higher MeOH partial pressure. With higher methanol partial pressure, one of ordinary skill would have expected higher methanol conversion. However, contrary to expectations, the examples show higher methanol conversion at lower methanol partial pressures, resulting in higher methanol utilization at lower methanol partial pressures.

[0039] Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Claims

C L A I M S

1. A process for making ethylbenzene comprising:

reacting toluene with a C1 source in the presence of a zeolite catalyst in one or more reactor zones to form a product comprising ethylbenzene;

maintaining a molar ratio of toluene: C1 source ranging from 3:1 to 30:1 throughout the one or more reactor zones,

wherein the reacting is performed at a pressure of from 1 to 10 bara;

wherein the partial pressure of the C1 source ranges from about 0.04 to about 0.5 bara.

2. The process according to claim 1, wherein the C1 source is selected from the group consisting of methanol, formaldehyde, formalin, trioxane, methylformcel, paraformaldehyde, methylal, DME and combinations thereof, preferably methanol.

3. The process according to claim 1, wherein the reacting is performed at a space velocity (WHSV) of from 0.1 to 10.0 h^-1.

4. The process according to claim 1 , wherein the product further comprises unreacted toluene and the process further comprises recycling the unreacted toluene to the one or more reactors.

5. The process according to claim 1, wherein the reacting is performed at a temperature of from 350 to 450C.

6. The process according to claim 1 , wherein maintaining the molar ratio of toluene:C1 source throughout the one or more reactor zones comprises injecting a portion of the C1 source into each of the one or more reactor zones.

7. The process according to claim 1, wherein the C1 source conversion is greater than 99%.

8. The process of claim 1, wherein the C1 source selectivity to ethyl benzene is greater than 60%.