CATALYSTS FOR HYDROGENATION OF AROMATIC CONTAINING POLYMERS AND USES THEREOF

Abstract

Catalysts for the hydrogenation of aromatic containing polymers are described. Such a catalyst can include, based on the total weight of the catalyst, 99.1 wt. % to 99.95 wt. % of a metal oxide support, and 0.05 wt. % to 0.9 wt. % of catalytic metal nanoparticles comprising platinum (Pt), palladium (Pd), ruthenium (Ru), any combination thereof, or alloy thereof. The catalyst can have a specific surface area of 5 m.sup.2/g to 80 m.sup.2/g, a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, and a catalyst median particle size of less than 300 microns. Processes to produce the catalyst and methods of hydrogenating aromatic containing polymers are also described.

Claims

1. A catalyst for the hydrogenation of an aromatic containing polymer, the catalyst comprising, based on the total weight of the catalyst: (a) 99.1 wt. % to 99.95 wt. % of a metal oxide support, and (b) 0.05 wt. % to 0.9 wt. % of catalytic metal nanoparticles comprising platinum (Pt), palladium (Pd), ruthenium (Ru), any combination thereof, or alloy thereof, wherein the catalyst has a specific surface area of 5 m.sup.2/g to 80 m.sup.2/g, a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, and a median particle diameter of less than 300 microns.

2. The catalyst of claim 1, wherein the catalyst has a surface area of 5 m.sup.2/g to 40 m.sup.2/g.

3. The catalyst of claim 1, wherein the catalyst has a pore volume of 0.03 cm.sup.3/g to 0.30 cm.sup.3/g.

4. The catalyst of claim 1, wherein the catalyst has a median particle diameter of less than 150 microns.

5. The catalyst of claim 1, wherein the metal oxide support comprises silica (SiO.sub.2), alumina (Al.sub.2O.sub.3), or titania (TiO.sub.2), or any combination thereof.

6. The catalyst of claim 1, wherein the catalytic metal nanoparticles have a size of 0.5 nm to 7 nm.

7. The catalyst of claim 1, wherein the dispersion of catalytic metal atoms on the nanoparticle surface is between on 30% to 80% with respect to the total metal atoms in the nanoparticle.

8. The catalyst of claim 1, wherein the catalyst comprises 0.05 wt. % to 0.8 wt. % of the catalytic metal nanoparticles, preferably 0.20 wt. % to 0.60 wt. % based on the total weight of the catalyst.

9. The catalyst of claim 1, wherein the catalytic metal nanoparticles are Pt nanoparticles.

10. The catalyst of claim 9, wherein the metal oxide support is TiO.sub.2, SiO.sub.2, Al.sub.2O.sub.3, or combinations thereof.

11. A method for the hydrogenation of an aromatic containing polymer, the method comprising contacting the catalyst of claim 1 with a polymer comprising at least one aromatic ring in the presence of hydrogen (H.sub.2) gas under conditions sufficient to produce a polymer composition comprising at least one hydrogenated and/or at least one partially hydrogenated aromatic ring.

12. The method of claim 11, wherein the aromatic containing polymer is a polystyrene and the hydrogenated or partially hydrogenated polymer comprises poly(vinyl cyclohexane), and wherein the hydrogenated or partially hydrogenated polymer composition is free or substantially free of polymer scission compositions, and/or wherein contacting conditions comprise a temperature of 130° C. to 200° C.

13. A process to produce the catalyst of claim 1, the process comprising: (a) contacting a slurry comprising 1) SiO.sub.2 or TiO.sub.2 metal oxide support in powder form, water, and a base, or 2) a Al.sub.2O.sub.3 metal oxide support in powder form, water, and an acid, with a catalytic metal precursor composition to produce a catalytic metal precursor/metal oxide support composition; and (b) reducing the catalytic metal precursor/metal oxide support composition under conditions to produce the catalyst.

14. The process of claim 13, further comprising drying the catalytic metal precursor/metal oxide support composition prior to step (b) and wherein the reducing conditions comprise contacting the catalytic metal precursor/metal oxide support composition with H.sub.2 at 250° C. to 450° C.

15. The process of claim 13, wherein the reducing conditions comprise adding a reducing agent to the catalytic metal precursor/metal oxide support composition to produce the catalyst, wherein the reducing agent is sodium borohydride or formaldehyde.

16. The process of claim 13, wherein the reducing conditions comprise adding a reducing agent to the catalytic metal precursor/metal oxide support composition to produce the catalyst, wherein the reducing agent is sodium borohydride or formaldehyde, and wherein the catalytic metal precursor comprises a platinum salt, a palladium salt, or a ruthenium salt, and wherein the base comprises ammonium hydroxide or a metal hydroxide and the acid comprises hydrochloric acid or nitric acid.

17. The process of claim 13, wherein the reducing conditions comprise adding a reducing agent to the catalytic metal precursor/metal oxide support composition to produce the catalyst, wherein the catalytic metal precursor comprises a platinum salt, a palladium salt, or a ruthenium salt, and wherein the base comprises ammonium hydroxide or a metal hydroxide and the acid comprises hydrochloric acid or nitric acid.

18. A catalyst for the hydrogenation of an aromatic containing polymer, the catalyst comprising, based on the total weight of the catalyst: (a) 99.1 wt. % to 99.95 wt. % of a metal oxide support in powder form, and (b) 0.05 wt. % to 0.9 wt. % of catalytic metal nanoparticles comprising platinum (Pt), or alloy thereof, wherein the catalyst has a specific surface area of 5 m.sup.2/g to 80 m.sup.2/g, a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, and a median particle diameter of less than 300 microns, wherein Brunauer-Emmett-Teller (BET) N.sub.2-adsorption measurements are performed at 77 K to characterize the surface area and pore volume; wherein the mean particle diameter of the supports is performed on a dynamic light scattering instrument, and wherein the amount of catalytic metal in the catalyst is determined using inductively coupled plasma atomic emission spectroscopy.

19. A process to produce the catalyst of claim 1, the process comprising: (a) contacting a slurry comprising 1) SiO.sub.2 or TiO.sub.2 metal oxide support in powder form, water, and a base, or 2) a Al.sub.2O.sub.3 metal oxide support in powder form, water, and an acid, with a catalytic metal precursor composition to produce a catalytic metal precursor/metal oxide support composition; and (b) reducing the catalytic metal precursor/metal oxide support composition under conditions to produce the catalyst of any one of claims 1 to 10, and (c) drying the catalytic metal precursor/metal oxide support composition prior to step (b) and wherein the reducing conditions comprise contacting the catalytic metal precursor/metal oxide support composition with H.sub.2 at 150° C. to 600° C.

20. The process of claim 18, wherein the reducing conditions comprise adding a reducing agent to the catalytic metal precursor/metal oxide support composition to produce the catalyst, wherein the reducing agent is sodium borohydride or formaldehyde, and/or wherein the catalytic metal precursor comprises a platinum salt and wherein the base comprises ammonium hydroxide or a metal hydroxide and the acid comprises hydrochloric acid or nitric acid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0029] FIG. 1 is an illustration of a reactor system to produce hydrogenated or partially hydrogenated aromatic polymers using the hydrogenation catalyst of the present invention.

[0030] FIGS. 2A and 2B are low (FIG. 2A) and high (FIG. 2B) resolution transmission electron microscope images of a catalyst of the present invention that includes Pt metal nanoparticles on a TiO.sub.2 support at different magnifications.

[0031] FIGS. 3A and 3B are low (FIG. 3A) and high (FIG. 3B) resolution transmission electron microscope images of a catalyst of the present invention that includes Pt metal nanoparticles on a SiO.sub.2 support.

[0032] FIGS. 4A and 4B are low (FIG. 4A) and high (FIG. 4B) resolution transmission electron microscope images of a catalyst of the present invention that includes Pt metal nanoparticles on an Al.sub.2O.sub.3 support.

[0033] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0034] At least one solution to some of the problems associated with hydrogenating aromatic-containing polymers has been discovered. The solution can include a cost-effective catalyst that has a low catalytic metal loading on a low pore-volume support. Such a catalyst can efficiently hydrogenate or partially hydrogenate aromatic containing polymers without causing polymer scission.

[0035] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Catalyst

[0036] The catalyst of the present invention can include a low pore volume support (pore volume less than 0.4 cm.sup.3/g) and a catalytic metal. The catalyst can have a specific surface area of at least 5 m.sup.2/g to 45 m.sup.2/g, or 5 m.sup.2/g to 40 m.sup.2/g, or 5 m.sup.2/g to 20 m.sup.2/g or 5 m.sup.2/g, 10 m.sup.2/g, 15 m.sup.2/g, 20 m.sup.2/g, 25 m.sup.2/g, 30 m.sup.2/g, 35 m.sup.2/g, 40 m.sup.2/g, or 45 m.sup.2/g, or any value or range there between. The pore volume of the catalyst can be 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, or 0.03 cm.sup.3/g to 0.3 cm.sup.3/g, or 0.05 cm.sup.3/g to 0.25 cm.sup.3/g, or 0.01, 0.03, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 cm.sup.3/g, or any value or range there between. The median particle diameter of the catalyst can be less than 300 microns, preferably less than 150 microns or 300, 250, 200, 150, 100, 50, 25, 15, 10, 1 microns or less, but greater than 0.1 micron. The catalyst has at least 50% of its pores having diameters of less than 100 nm. The support can be alumina (Al.sub.2O.sub.3), titania (TiO.sub.2), silica (SiO.sub.2), or mixtures thereof, or combinations thereof. The support can be in powder form. In a preferred embodiment, the support is not in an extrudate or a bead form. The support can have a specific surface area of at least 5 m.sup.2/g to 80 m.sup.2/g, 5 m.sup.2/g to 60 m.sup.2/g, 5 m.sup.2/g to 45 m.sup.2/g, or 5 m.sup.2/g to 40 m.sup.2/g, or 5 m.sup.2/g to 20 m.sup.2/g or 5 m.sup.2/g, 10 m.sup.2/g, 15 m.sup.2/g, 20 m.sup.2/g, 25 m.sup.2/g, 30 m.sup.2/g, 35 m.sup.2/g, 40 m.sup.2/g, 45 m.sup.2/g, 50 m.sup.2/g, 55 m.sup.2/g, 60 m.sup.2/g, 65 m.sup.2/g, 70 m.sup.2/g, 75 m.sup.2/g, or 80 m.sup.2/g, or any value or range there between. The pore volume of the support can be 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, or 0.03 cm.sup.3/g to 0.3 cm.sup.3/g, or 0.05 cm.sup.3/g to 0.25 cm.sup.3/g, or 0.01, 0.03, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 cm.sup.3/g, or any value or range there between. The median particle diameter of the support can be less than 300 microns, preferably less than 150 microns or 300, 250, 200, 150, 100, 50, 25, 15, 10, 1 microns or less, but greater than 0.1 micron. In one aspect, the support can have 1) a specific surface area of at least 5 m.sup.2/g to 80 m.sup.2/g, 5 m.sup.2/g to 60 m.sup.2/g, 5 m.sup.2/g to 45 m.sup.2/g, or 5 m.sup.2/g to 40 m.sup.2/g, or 5 m.sup.2/g to 20 m.sup.2/g or 5 m.sup.2/g, 10 m.sup.2/g, 15 m.sup.2/g, 20 m.sup.2/g, 25 m.sup.2/g, 30 m.sup.2/g, 35 m.sup.2/g, 40 m.sup.2/g, 45 m.sup.2/g, 50 m.sup.2/g, 55 m.sup.2/g, 60 m.sup.2/g, 65 m.sup.2/g, 70 m.sup.2/g, 75 m.sup.2/g, or 80 m.sup.2/g, or any value or range there between; 2) a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, or 0.03 cm.sup.3/g to 0.3 cm.sup.3/g, or 0.05 cm.sup.3/g to 0.25 cm.sup.3/g, or 0.01, 0.03, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 cm.sup.3/g, or any value or range there between and 3) a median particle diameter less than 300 microns, preferably less than 150 microns or 300, 250, 200, 150, 100, 50, 25, 15, 10, 1 microns or less, but greater than 0.1 micron. The support has at least 50% of its pores having diameters of less than 100 nm. Based on the total weight of the catalyst, the catalyst can include 99.1 wt. % to 99.95 wt. %, 99.75 wt. % to 99.5 wt. % or any range or value there between (e.g., 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, 99.9, 99.95 wt. %). The amount of support will balance the amount of catalytic metal used.

[0037] The catalyst include catalytic nanoparticles that include platinum (Pt), palladium (Pd), ruthenium (Ru) or any combination thereof. The nanoparticles can be 0.5 nm to 7 nm, or 1 nm, to 4 nm, or 1 nm to 2 nm in size or any range or value there between (e.g., 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, or 7 nm). The dispersion of catalytic metal atoms on the nanoparticle surface is between on 30% to 80%, 30% to 70% or 40% to 50% or any range or value there between (e.g., 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%) with respect to the total metal atoms in the nanoparticle. The total amount of catalytic metal nanoparticles, based on the total weight of catalyst, can range from 0.05 wt. % to 0.9 wt. %, or 0.2 to 0.6 wt. %, or 0.25 to 0.5 wt. %, or 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, wt. % or any range or value there between. In a preferred instance, the total amount of catalytic metal can be about 0.25 to 0.5 wt. %.

[0038] In one embodiment, the catalyst can include, based on the total weight of the catalyst, 0.05 wt. % to 0.9 wt. % of Pt nanoparticles and 99.1 wt. % to 99.95 wt. % of TiO.sub.2, 0.20 wt. % to 0.60 wt. % of Pt nanoparticles and 99.4 wt. % to 99.8 wt. % of TiO.sub.2, or 0.25 wt. % to 0.50 wt. % of Pt nanoparticles and 99.5 wt. % to 99.75 wt. % of TiO.sub.2. Such a catalyst has a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, preferably 0.03 cm.sup.3/g to 0.30 cm.sup.3/g, more preferably 0.05 cm.sup.3/g to 0.25 cm.sup.3/g, a surface area of 5 m.sup.2/g to 80 m.sup.2/g, preferably 5 m.sup.2/g to 40 m.sup.2/g, more preferably 5 m.sup.2/g to 20 m.sup.2/g, and a median pore diameter of less than 300 microns, preferably less than 100 microns.

[0039] In one embodiment, the catalyst can include, based on the total weight of the catalyst, 0.05 wt. % to 0.9 wt. % of Pt nanoparticles and 99.1 wt. % to 99.95 wt. % of SiO.sub.2, 0.20 wt. % to 0.60 wt. % of Pt nanoparticles and 99.4 wt. % to 99.8 wt. % of SiO.sub.2, or 0.25 wt. % to 0.50 wt. % of Pt nanoparticles and 99.5 wt. % to 99.75 wt. % of SiO.sub.2. Such a catalyst can have a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, preferably 0.03 cm.sup.3/g to 0.30 cm.sup.3/g, more preferably 0.05 cm.sup.3/g to 0.25 cm.sup.3/g, a surface area of 5 m.sup.2/g to 802/g, preferably 5 m.sup.2/g to 40 m.sup.2/g, more preferably 5 m.sup.2/g to 20 m.sup.2/g, and a median pore diameter of less than 300 microns, preferably less than 100 microns.

[0040] In one embodiment, the catalyst can include, based on the total weight of the catalyst, 0.05 wt. % to 0.9 wt. % of Pt nanoparticles and 99.1 wt. % to 99.95 wt. % of Al.sub.2O.sub.3, 0.20 wt. % to 0.60 wt. % of Pt nanoparticles and 99.4 wt. % to 99.8 wt. % of Al.sub.2O.sub.3, or 0.25 wt. % to 0.50 wt. % of Pt nanoparticles and 99.5 wt. % to 99.75 wt. % of Al.sub.2O.sub.3. Such a catalyst has a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, preferably 0.03 cm.sup.3/g to 0.30 cm.sup.3/g, more preferably 0.05 cm.sup.3/g to 0.25 cm.sup.3/g, a surface area of 5 m.sup.2/g to 80 m.sup.2/g, preferably 5 m.sup.2/g to 40 m.sup.2/g, more preferably 5 m.sup.2/g to 20 m.sup.2/g, and a median pore diameter of less than 300 microns, preferably less than 100 microns.

B. Catalyst Preparation

[0041] The catalyst can be made using catalyst preparation methodology known to a person with skill in performing catalyst synthesis (e.g., a chemist or an engineer). Depending on the support material, a base or acid may be employed during the process of producing the catalyst. More than one method of reducing the catalyst precursor to a nanoparticle can also be used. Non-limiting examples of preparing the catalyst are described below.

1. SiO.SUB.2 .and TiO.SUB.2 .Supports, Catalytic Metal and H.SUB.2 .Reduction

[0042] A catalytic metal precursor can be dissolved in deionized water to form a catalytic metal precursor solution. Catalytic metal precursors can be obtained as a metal nitrate, a metal amine, a metal chloride, a metal coordination complex, a metal sulfate, a metal phosphate hydrate, metal complex, or any combination thereof. These metals or metal compounds can be purchased from any chemical supplier such as Millipore Sigma (St. Louis, Mo., USA), Alfa-Aesar (Ward Hill, Mass., USA), and Strem Chemicals (Newburyport, Mass., USA). A non-limiting example of a metal precursor compound is tetraammineplatinum(II) chloride, tetraamineplatinum(II) nitrate, tetraamineplatinum(II) hydroxide, tetraaminepalladium(II) chloride, tetraaminepalladium(II) nitrate, hexaammineruthenium(III) chloride, or hexaammineruthenium(II) chloride. The catalytic metal precursor solution can be added to a composition that includes a known quantity of support (e.g., SiO.sub.2 or TiO.sub.2), water, and a base (e.g., ammonium hydroxide or sodium hydroxide) to form a catalytic metal precursor/support composition. Support materials can be obtained from commercial suppliers such as Millipore Sigma, Alfa-Aesar, Cristal, Evonik, and the like. In some embodiments, the water suspension of catalyst supports can be added to the metal precursor solution. The catalytic metal precursor/support composition can be agitated for a period of time (e.g., 0.5 to 24 hours) at ambient temperature (e.g., 20° C. to 35° C.). The catalytic metal precursor/support composition can be separated from the water using known separation techniques (e.g., filtration, centrifugation, and the like) and washed sufficiently with deionized water to remove any residual base. Residual water in the filtered catalytic metal precursor/support composition can be removed by drying the catalytic metal precursor/support composition at a temperature of 80° C. to 100° C., or about 95° C. Once dried, the dried catalytic metal precursor/support composition can be subjected to reducing conditions to convert the catalytic metal precursor to metal nanoparticles. Reducing conditions can include using H.sub.2 balanced with N.sub.2 with at a desired flowrate (e.g., 450 to 600 standard cubic centimeter per min) at a desired temperature. For example, a temperature rate of 5 to 10° C./min from 20° C. to 400° C. and kept at 400° C. for 0.5 to 1 hr before cooling to room temperature to produce the catalysts of the present invention.

2. SiO.SUB.2 .and TiO.SUB.2 .Supports, Catalytic Metal and Solution Reduction

[0043] A catalytic metal precursor described in Section B. la can be dissolved in deionized water to form a catalytic metal precursor solution. The catalytic metal precursor solution can be added to a composition that includes a known quantity of support (e.g., SiO.sub.2 or TiO.sub.2), water, and a base (e.g., ammonium hydroxide or sodium hydroxide), and agitated for a period of time (e.g., 0.5 to 24 hours) at ambient temperature (e.g., 20° C. to 35° C.) to form a catalytic metal precursor/support composition. In some embodiments, the water suspension of catalyst supports can be added to the metal precursor solution. A reducing agent such as sodium borohydride or formaldehyde dissolved in deionized water can be added dropwise into catalyst precursor/support composition and the resulting mixture can then be stirred for a desired amount of time (e.g., 1 hr to 24 hrs). A molar reducing agent to Pt ratio can be 1:1, 2:1, 3:1, 4:1, 5:1 or any value or range there between. The solid catalyst/support material can be separated from the slurry and washed with deionized water to remove excess materials (e.g., three times with deionized water). The washed solid catalyst/support material can be dried in an oven at 95° C. to produce the Pt/TiO.sub.2 catalyst of the present invention.

3. Al.SUB.2.O.SUB.3 .Support, Catalytic Metal, and H.SUB.2 .Reduction

[0044] A catalytic metal precursor can be dissolved in deionized water to form a catalytic metal precursor solution. Catalytic metal precursors can be obtained as a metal nitrate, a metal amine, a metal chloride, a metal coordination complex, a metal sulfate, a metal phosphate hydrate, metal complex, or any combination thereof. Non-limiting examples of metal precursor compounds include chloroplatinic acid, potassium hexachloroplatinate(IV), potassium tetrachloroplatinate(II), sodium hexachloroplatinate(IV), sodium tetrachloroplatinate (II), potassium hexachloropalladate(IV), potassium tetrachloropalladate(II), sodium hexachloropalladate(IV), sodium tetrachloropalladate(II), or ammonium hexachlororuthenate(IV). These metals or metal compounds can be purchased from any chemical supplier such as Millipore Sigma (St. Louis, Mo., USA), Alfa-Aesar (Ward Hill, Mass., USA), and Strem Chemicals (Newburyport, Mass., USA). The catalytic metal precursor solution can be added to a composition that includes a known quantity of Al.sub.2O.sub.3, water, and a mineral acid (e.g., hydrochloric acid or nitric acid) and, then, agitated for a period of time (e.g., 0.5 to 24 hours) at ambient temperature (e.g., 20° C. to 35° C.) to form a catalytic metal precursor/Al.sub.2O.sub.3 composition. It should be understood that the order of addition of the catalyst and support solutions can be reversed. Al.sub.2O.sub.3 can be obtained from commercial suppliers such as Alfa-Aesar, Millipore Sigma, and the like. The catalytic metal precursor/ Al.sub.2O.sub.3 composition can be separated from the water using known separation techniques (e.g., filtration, centrifugation, and the like) and washed sufficiently with deionized water to remove any residual acid. Water in the filtered catalytic metal precursor/Al.sub.2O.sub.3 composition can be removed by drying the catalytic metal precursor/Al.sub.2O.sub.3 composition at a temperature of 80° C. to 100° C., or about 95° C. Once dried, the dried catalytic metal precursor/Al.sub.2O.sub.3 composition can be subjected to reducing conditions to convert the catalytic metal precursor to metal nanoparticles. Reducing condition can include using H.sub.2 balanced N.sub.2 with at a desired flowrate (e.g., 450 to 600 standard cubic centimeter per min) at a desired temperature. For example, a temperature rate of 5 to 10° C./min from 20° C. to 400° C. and kept at 400° C. for 0.5 to 1 hr before cooling to room temperature to produce the Al.sub.2O.sub.3 supported catalysts of the present invention.

C. Methods of Hydrogenating Aromatic-Containing Polymers

[0045] FIG. 1 depicts a schematic for a process for the hydrogenation of an aromatic-containing polymer using the catalyst(s) of the present invention. Reactor 100 can include inlet 102 for a polymer reactant feed, inlet 104 for H.sub.2 reactant feed, reaction zone 106 that is configured to be in fluid communication with the inlets 102 and 104, and outlet 108 configured to be in fluid communication with the reaction zone 106 and configured to remove the product stream (e.g., hydrogenated or partially hydrogenated aromatic containing polymer) from the reaction zone. Reactor 100 can be any reactor suitable for performing polymer hydrogenations (e.g., a batch reactor or continuous reactor). Reaction zone 106 can include the hydrogenation catalyst of the present invention. The polymer reactant feed can enter reaction zone 106 via inlet 102. The reactant feed can be a mixture of solvent (e.g., cyclohexane or decahydronaphthalene) and polymer. A mass ratio of solvent to polymer can be 4:1, 9:1, 19:1 or any range or value there between. The H.sub.2 reactant feed can enter reactor 100 after purging the reactor with nitrogen via inlet 104. Pressure of reactor 100 can be maintained with the H.sub.2 reactant feed. The product stream can be removed from the reaction zone 106 via product outlet 108. The product stream can be sent to other processing units, stored, and/or be transported.

[0046] Reactor 100 can include one or more heating and/or cooling devices (e.g., insulation, electrical heaters, jacketed heat exchangers in the wall) or controllers (e.g., computers, flow valves, automated values, etc.) that can be used to control the reaction temperature and pressure of the reaction mixture. While only one reactor is shown, it should be understood that multiple reactors can be housed in one unit or a plurality of reactors housed in one heat transfer unit. In some embodiments, a series of physically separated reactors with interstage cooling/heating devices, including heat exchangers, furnaces, fired heaters, and the like can be used.

[0047] The temperature and pressure can be varied depending on the reaction to be performed and is within the skill of a person performing the reaction (e.g., an engineer or chemist). Temperatures can range from 130° C. to about 200° C., 140° C. to 190° C., 150° C. to 180° C., or any value or range there between. H.sub.2 pressures can range from about 3.45 MPa to 7 MPa or 3.45, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.5, 5.0, 5.5, 6.0, 6.5, or 7.0 or any range or value there between.

[0048] The product stream can include at least one hydrogenated, at least one partially hydrogenated aromatic ring, or both, or mixtures thereof. For example, polystyrene can be hydrogenated to produce poly(vinylcyclohexane). The produced polymer product is absent lower molecular weight polymers due to polymer scission. The hydrogenation activity can be at least 10 moles of aromatic rings per hour per gram of catalytic metal (e.g., Pt, Pd, and/or Ru) at the reaction temperature of 140° C., pressure of 6.9 MPa, and polymer concentration of 8 wt %. Hydrogenation level can be at least 90%.

EXAMPLES

[0049] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.

Testing Methodology and Instrumentation

[0050] Brunauer-Emmett-Teller (BET) N.sub.2-adsorption measurements were performed at 77 K on a Quantachrome Autosorb-6iSA analyzer to characterize the surface area and pore volume. Particle size analysis of the supports was performed on a Malvern Panalytical Zetasizer Dynamic Light Scattering (DLS) instrument. The amount of catalytic metal in the catalysts of the present invention was determined using inductively coupled plasma atomic emission spectroscopy (ICP-AES) on a PerkinElmer Optima 8300 ICP-OES Spectrometer. The catalytic metal was dissolved by aqua regia, followed by dilution with deionized H.sub.2O and filtration to remove the solid support to obtain a clear metal solution. The metal nanoparticles were characterized by transmission electron microscopy using an FEI Tecnai F20 TEM operating at 200 keV. TEM samples of the catalysts were prepared through dry deposition, namely slight shaking a lacey-carbon Cu-mesh TEM grid within the catalyst powder in a glass vial. The metal dispersion in the metal nanoparticles was measured by static H.sub.2-O.sub.2 titration technique. The H.sub.2 chemisorption experiments were performed on a Micrometrics 3Flex instrument. Approximately 600 mg of the catalyst powder was loaded in a quartz tube and subjected to pretreatment that consisted of H.sub.2 reduction (50 standard cubic centimeter per minute) at 200° C. for 4 hr, followed by evacuation at 200° C. for 4 hr and cooling down to 35° C. under evacuation for another 30 min. Then, O.sub.2 was admitted to the catalyst at 35° C. and 1 atm to contact the catalyst for 60 min. After evacuating the O.sub.2 out at 35° C. for 1 hr, the first H.sub.2 uptake was measured over a pressure range at 35° C. by H.sub.2 adsorption isotherm. After evacuating the H.sub.2 out at the same temperature, the second H.sub.2 uptake was measured at the same condition as the first H.sub.2 adsorption isotherm. The amount of chemisorbed H.sub.2 was calculated from difference between the first H.sub.2 uptake and the second H.sub.2 uptake. Because the reaction PtO (surface)+3/2 H.sub.2.fwdarw.PtH (surface)+H.sub.2O took place, the stoichiometry of 3:1 for the adsorbed H atom and the surface Pt atom was used. The metal dispersion was normalized by the surface metal atoms over the total metal atoms in the catalysts measured from ICP analysis.

Examples 1(a) and 1(b)

(Synthesis of Pt on Low Pore Volume TiO.SUB.2 .Catalyst)

[0051] TiO.sub.2 (commercial TiO.sub.2), calcined at static air at 820° C. for 5 h, surface area of 10.4 m.sup.2/g, pore volume of 0.24 cm.sup.3/g, a median particle diameter (D50) of less than 2 microns, 6 grams) was dispersed in deionized H.sub.2O (60 mL). Ammonium hydroxide solution (30 wt. %, 0.78 mL) was added into the mixture, and the slurry stirred for 30 min.

[0052] Tetraammineplatinum(II) chloride (from 106 mg) dissolved in H.sub.2O (2 mL) was added into the slurry and then the mixture was stirred for 1.5 hrs. The resulting catalyst precursor/support material was separated from the slurry using vacuum filtration. The solid catalyst precursor/support material was washed (3 times) with deionized water (100 mL), and then dried in a drying oven at 95° C. for 3 hours to produce the catalyst precursor/support material as a dry powder. The catalyst precursor/support dry powder was reduced in a horizontal tube furnace using 10% H.sub.2 balanced N.sub.2 with a total flowrate of 500 standard cubic centimeter per min under the following conditions: a temperature rate of 10° C./min from 20° C. to 400° C. and keep at 400° C. for 1 hr before cooling to room temperature to produce the Pt/TiO.sub.2 catalysts of the present invention. The final Pt loading was determined to be 0.33 wt. % by ICP analysis.

[0053] The Pt/TiO.sub.2 catalysts prepared through the above methods had highly dispersed small crystalline Pt nanoparticles with the size of 1 to 2 nm and a metal atom dispersion of 40% to 60%. FIGS. 2A and 2B show representative electron transmission microscopic images of the Pt/TiO.sub.2 catalysts.

Examples 2(a)-2(e)

[0054] (Synthesis of Pt on low pore volume SiO.sub.2 Catalysts)

[0055] SiO.sub.2 (commercial silica, calcined at static air at 820° C. for 5 h, having a surface area of 17.2 m.sup.2/g, a pore volume of 0.22 cm.sup.3/g, and a median particle diameter (D.sub.50) of less than 5 microns, 6 grams) was dispersed in deionized H.sub.2O (60 mL). Ammonium hydroxide solution (30 wt. %, 0.78 mL) was added into the mixture, and the slurry stirred for 30 min. Tetraammineplatinum(II) chloride (106 mg) dissolved in H.sub.2O (2 mL) was added into the slurry and then the mixture was stirred for 1.5 hrs. The resulting catalyst precursor/support material was separated from the slurry using vacuum filtration. The solid catalyst precursor/support material was washed (3 times) with deionized water (100 mL) and then dried in a drying oven at 95° C. for 3 hours to produce the catalyst precursor/support material as a dry powder. The catalyst precursor/support dry powder was reduced in a horizontal tube furnace using 10% H.sub.2 balanced N.sub.2 with a total flowrate of 500 standard cubic centimeter per min under the following conditions: a temperature rate of 10° C./min from 20° C. to 400° C. and keep at 400° C. for 1 hr before cooling to room temperature. The catalyst of the present invention had a Pt weight loading of 0.41 wt. % as determined by ICP anlysis. The particle size was 1 to 2 nm and the metal atom dispersion was 40% to 60%. FIGS. 3A and 3B show electron transmission microscopy images of the Pt nanoparticles on the SiO.sub.2 support.

Example 3

[0056] (Preparation of Pt on Low Pore Volume Al.sub.2O.sub.3 Catalysts)

[0057] Al.sub.2O.sub.3 (having a specific surface area of 8.4 m.sup.2/g, a pore volume of 0.19 cm.sup.3/g, and a median particle diameter of less than 1 micron, 6 grams) was dispersed in deionized H.sub.2O (60 mL). Hydrochloric acid (1.6 mL, 0.1 M HCl) was added into the mixture, and the slurry stirred for 30 min. H.sub.2PtCl.sub.6 (125 mg) dissolved in H.sub.2O (2 mL) was added into the slurry and then mixture was stirred for 1.5 hrs. The resulting catalyst precursor/support material was separated from the slurry using vacuum filtration. The solid catalyst precursor/support material was washed (3 times) with deionized water (100 mL) and then dried in a drying oven at 95° C. for 3 hours to produce the catalyst precursor/support material as a dry powder. The catalyst precursor/support dry powder was reduced in a horizontal tube furnace using 10% H.sub.2 balanced N.sub.2 with a total flowrate of 500 standard cubic centimeter per min under the following conditions: a temperature rate of 10° C./min from 20° C. to 400° C. and keep at 400° C. for 1 hr before cooling to room temperature to produce the Pt/Al.sub.2O.sub.3 catalyst of the present invention. The final Pt loading was determined to be 0.17 wt. %, the Pt nanoparticles were 1 to 2 nm in size, and the metal atom dispersion was 40 to 60%. FIGS. 4A and 4B show representative electron transmission microscopic images of the Pt/Al.sub.2O.sub.3 catalysts.

Example 4

[0058] (Preparation of Pt on Low Pore Volume Al.sub.2O.sub.3 Catalysts—Impregnation Method)

[0059] Al.sub.2O.sub.3 (having a specific surface area of 8.8 m.sup.2/g, a pore volume of 0.21 cm.sup.3/g, and a median particle diameter of less than 100 microns) was used in the impregnation preparation of Pt on low pore volume Al.sub.2O.sub.3. A H.sub.2PtCl.sub.6 stock solution Pt (3.6 wt. %) was prepared by dissolving H.sub.2PtCl.sub.6 in de-ionized H.sub.2O. Then H.sub.2PtCl.sub.6 stock solution (0.7 g, 0.025 g Pt in the solution) was diluted with deionized H.sub.2O (4.5 g). The diluted H.sub.2PtCl.sub.6 solution was added slowly to the Al.sub.2O.sub.3 (5.0 g), and the mixture was agitated and mixed to wet the solid and form a Pt catalyst precursor/Al.sub.2O.sub.3 composition. The Pt catalyst precursor/Al.sub.2O.sub.3 composition was dried in the oven overnight at 90° C. Then the dried sample was reduced in a horizontal tube furnace using 10% H.sub.2 balanced N.sub.2 with a total flow rate of 500 standard cubic centimeter per min under the following conditions: a temperature rate of 5° C./min from 20° C. to 200° C. and keep at 200° C. for 1 hr before cooling to room temperature to produce the 0.5 wt. % Pt/Al.sub.2O.sub.3 catalyst of the present invention.

Example 5

[0060] (Preparation of Pt on Low Pore Volume Al.sub.2O.sub.3 Support)

[0061] Al.sub.2O.sub.3 (having a specific surface area of 8.8 m.sup.2/g, a pore volume of 0.21 cm.sup.3/g, and a median particle diameter of less than 100 microns) was used in the preparation of a catalyst of the present invention (Pt on low pore volume Al.sub.2O.sub.3). Al.sub.2O.sub.3 (6 g) were dispersed in deionized H.sub.2O (60 mL). H.sub.2PtCl.sub.6 (125 mg) dissolved in H.sub.2O (2 mL) was added into the slurry and then mixture was stirred for 2 hrs. The resulting catalyst precursor/support material was separated from the slurry using vacuum filtration. The solid catalyst precursor/support material was washed (3 times) with deionized water (100 mL) and then dried in a drying oven at 95° C. for 3 hours to produce the Pt catalyst precursor/Al.sub.2O.sub.3 support material as a dry powder. The Pt catalyst precursor/Al.sub.2O.sub.3 support dry powder was reduced in a horizontal tube furnace using 10% H.sub.2 balanced N.sub.2 with a total flowrate of 500 standard cubic centimeter per min under the following conditions: a temperature rate of 10° C./min from 20° C. to 400° C. and keep at 400° C. for 1 hr before cooling to room temperature to produce the Pt/Al.sub.2O.sub.3 catalyst of the present invention. The final Pt loading was determined to be 0.16 wt. %.

Comparative Example A

[0062] (Preparation of Pt on High Pore Volume Al.sub.2O.sub.3 Catalyst—Impregnation Method)

[0063] Al.sub.2O.sub.3 (having a specific surface area of 103 m.sup.2/g, a pore volume of 0.55 cm.sup.3/g, and a median particle diameter of less than 100 microns) was used in the impregnation preparation of Pt on high pore volume Al.sub.2O.sub.3. A H.sub.2PtCl.sub.6 stock solution (3.6 wt. % Pt) was prepared by dissolving H.sub.2PtCl.sub.6 in de-ionized H.sub.2O. Then the premade H.sub.2PtCl.sub.6 stock solution (0.7 g, 0.025 g Pt in the solution) was diluted with deionized H.sub.2O (4.5 g). The diluted H.sub.2PtCl.sub.6 solution was added slowly to Al.sub.2O.sub.3 powder (0.5 g) and the mixture was agitated and mixed to wet the solid. The comparative catalyst precursor/support material was dried in the oven overnight at 90° C.

[0064] Then the dried comparative catalyst precursor/support material was reduced in a horizontal tube furnace using 10% H.sub.2 balanced N.sub.2 with a total flow rate of 500 standard cubic centimeter per min under the following conditions: a temperature rate of 1° C./min from 20° C. to 200° C. and keep at 200° C. for 1 hr before cooling to room temperature to produce the comparative Pt/Al.sub.2O.sub.3 material having a Pt loading of 0.5 wt. %.

Comparative Example B

[0065] (Preparation of Pt on High Pore Volume Al.sub.2O.sub.3 Catalyst)

[0066] Al.sub.2O.sub.3 (having a specific surface area of 103 m.sup.2/g, a pore volume of 0.55 cm.sup.3/g, and a median particle diameter of less than 100 microns) was used in the preparation of Pt on high pore volume Al.sub.2O.sub.3. Al.sub.2O.sub.3 (6 g) was dispersed in deionized H.sub.2O (60 mL). H.sub.2PtCl.sub.6 (125 mg) dissolved in H.sub.2O (2 mL) was added into the slurry and then mixture was stirred for 2 hrs. The resulting comparative catalyst precursor/support material was separated from the slurry using vacuum filtration. The solid comparative catalyst precursor/support material was washed (3 times) with deionized water (100 mL) and then dried in a drying oven at 95° C. for 3 hours to produce the comparative catalyst precursor/support material as a dry powder. The comparative catalyst precursor/support dry powder was reduced in a horizontal tube furnace using 10% H.sub.2 balanced N.sub.2 with a total flowrate of 500 standard cubic centimeter per min under the following conditions: a temperature rate of 10° C./min from 20° C. to 400° C. and keep at 400° C. for 1 hr before cooling to room temperature to produce the comparative Pt/Al.sub.2O.sub.3 catalyst having a Pt loading of 1.0 wt. %.

Comparative Example C

[0067] (Preparation of Pt on Al.sub.2O.sub.3 Extrudate Catalyst)

[0068] Extruded Al.sub.2O.sub.3 sphere beads (having a specific surface area of 2.2 m.sup.2/g, a pore volume of 0.01 cm.sup.3/g, sphere beads size 0.7 to 1.4 mm) was used in the preparation of Pt on Al.sub.2O.sub.3 extrudate. Al.sub.2O.sub.3 (6 g) was dispersed in deionized H.sub.2O (60 mL). H.sub.2PtCl.sub.6 (125 mg) dissolved in H.sub.2O (2 mL) was added into the slurry and then mixture was stirred for 2 hrs. The resulting comparative catalyst precursor/Al.sub.2O.sub.3 extrudate was separated from the slurry using vacuum filtration. The solid comparative catalyst precursor/Al.sub.2O.sub.3 extrudate was washed (3 times) with deionized water (100 mL) and then dried in a drying oven at 95° C. for 3 hours to produce the comparative catalyst precursor/Al.sub.2O.sub.3 extrudate as a dry powder. The comparative catalyst precursor/Al.sub.2O.sub.3 extrudate was reduced in a horizontal tube furnace using 10% H.sub.2 balanced N.sub.2 with a total flowrate of 500 standard cubic centimeter per min under the following conditions: a temperature rate of 10° C./min from 20° C. to 400° C. and keep at 400° C. for 1 hr before cooling to room temperature to produce the comparative Pt/Al.sub.2O.sub.3 extrudate catalyst having a Pt loading of 0.01 wt. %.

Example 6

(Physical Properties of Catalysts of the Present Invention and Comparative Catalysts)

[0069] The surface area, pore volume, and median particle diameter of the support material, catalysts of the present invention (Examples 1, 2 and 5) and the comparative catalysts (Comparative Example 7) were measured using the instrumentation described above under Testing Methodology and Instrumentation. The results are listed in Table 1. The Examples of the present invention (Examples 1, 2, and 5) had a surface area of 5 m.sup.2/g to 80 m.sup.2/g, a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, and a catalyst median particle diameter (D.sub.50) of less than 300 microns. In contrast, the comparative catalyst (Comparative Example B) had a surface area of 105 m.sup.2/g, a pore volume of 0.56 cm.sup.3/g and a median particle diameter of 52.6 microns.

TABLE-US-00001 TABLE 1 Support Material or Surface Pore Median particle Catalyst/support area volume diameter Example material (m.sup.2/g) (cm.sup.3/g) (μm) 1 TiO.sub.2 10.4 0.24 0.95 1 Pt/TiO.sub.2 10.4 0.20 0.72 2 SiO.sub.2 17.2 0.22 3.33 2 Pt/SiO.sub.2 21.8 0.27 2.82 5 Al.sub.2O.sub.3 8.8 0.21 82.8 5 Pt/Al.sub.2O.sub.3 9.1 0.26 53.5 CE B Al.sub.2O.sub.3 103 0.55 88.9 CE B Pt/Al.sub.2O.sub.3 105 0.56 52.6

Example 7

(Methods of Hydrogenation of Polystyrene)

[0070] The catalysts of the present invention (Examples 1(a) to 1(b), 2(a) to 2(e), 3, 4 and 5) and the comparative catalysts (Comparative Examples A, B and C) were used to hydrogenate polystyrene. A determined amount of the catalysts (typically in the range of 0.013 g to 0.780 g) was placed in a stainless reactor (Parr Series 5000 Multiple Reactor System, Parr Instrument Company, 100 mL) together with cyclohexane (30 mL, solvent) and polystyrene (PS-155, SABIC® (Saudi Arabia), average molecular weight M.sub.w=235,000, 2 g). The reactor was purged first with N.sub.2 for three times, and then with H.sub.2 three times to remove air and moisture and the charged with high-pressure H.sub.2 to the desired reaction pressure, about 500 and 1000 psi (3.4 MPa to 6.9 MPa). After the desired pressure has been reached the reactor content was heated to a set temperature between 140 and 200° C., at a rate of 1° C./min, and maintain at the final set temperature for a certain time, generally from 1 hr to 12 hr. After the reaction finished, the reactor was cooled to room temperature, the pressure discharged to atmospheric pressure (101 kPa), the contents in the reactor recovered, and the solid catalysts was separated from the polymer solution using centrifugation or filtration.

[0071] The conversion of aromatic rings was determined by comparing the Fourier Transfer Infrared (FT-IR) spectrum of the final polymer product using a FT-IR spectrometer (NICOLET iS50 FT-IR) with that of unsaturated polystyrene. The unsaturated aromatic rings showed a distinct IR absorptions at about 700 cm.sup.−1 due to out-of-plane bends for the C—H bond attached to the aromatic rings. The conversion was 100% for the Pt catalysts of the present invention. The molecular weight of the final product was measured by gel permeation chromatography (GPC) and showed no scission of the polymer chains after the hydrogenation reaction. The catalytic hydrogenation results are tabulated in Table 2.

TABLE-US-00002 TABLE 2 Catalyst Reaction H.sub.2 Reaction Mass Temp Press. time Hydrogenation Hydrogenation Example Catalyst (g) (° C.) (psig) (min) activity.sup.(1, 2) level (%) 1a 0.33% Pt/TiO.sub.2  0.78 140 1000 30 15 100 1b 0.33% Pt/TiO.sub.2  0.78 160 1000 15 30 100 2a 0.41% Pt/SiO.sub.2  0.26 140 1000 28 40 100 2b 0.41% Pt/SiO.sub.2  0.13 140 1000 60 36 100 2d 0.41% Pt/SiO.sub.2  0.067 160 1000 60 70 100 2d 0.41% Pt/SiO.sub.2  0.067 180 1000 25 169 100 2e 0.41% Pt/SiO.sub.2  0.067 200 1000 13 326 100 3 0.17% Pt/Al.sub.2O.sub.3 0.78 140 1000 36 24 100 4 0.50% Pt/Al.sub.2O.sub.3 0.78 140 1000 17 17 100 5 0.16% Pt/Al.sub.2O.sub.3 0.78 140 1000 30 31 100 Comparative 0.50% Pt/Al.sub.2O.sub.3 0.78 140 1000 120 2.5 100 Ex . A Comparative  1.0% Pt/Al.sub.2O.sub.3 0.78 140 1000 48 3.1 100 Ex. B Comparative 0.01% Pt/Al.sub.2O.sub.3 0.78 140 1000 280 2.0 4 Ex. C .sup.(1)Polystyrene, M.sub.w = 235,000 g/mol, PDI = 2.81, SABIC ®. .sup.(2)Hydrogenation activity refers to as a measured rate of polymer hydrogenation, in the unit of moles of aromatic rings per hour per gram of Pt at a specific reaction temperature, pressure, and polymer concentration.

[0072] From these results, the catalysts of the present invention having 0.05 wt. % to 0.9 wt. % of catalytic metal nanoparticles that includes platinum (Pt), palladium (Pd), ruthenium (Ru), any combination thereof, or alloy thereof on a metal oxide support SiO.sub.2, Al.sub.2O.sub.3, or TiO.sub.2, or any combination thereof, and having a surface area of 5 m.sup.2/g to 80 m.sup.2/g, a pore volume of 0.01 cm.sup.3/g to 0.35 cm.sup.3/g, and a catalyst median particle diameter (D.sub.50) of less than 300 microns had higher hydrogenation activity as compared to Comparative Example A (catalyst made through impregnation methods) and Comparative Example B (catalyst having a high pore volume). The examples of the present invention (Examples 1-5) had a higher hydrogenation activity and level than the extrude catalyst of Comparative Example 8. Thus, the catalysts of the present invention provide at least one solution to some of the problems associated with hydrogenating aromatic-containing polymers has been discovered. Such a catalyst can efficiently hydrogenate or partially hydrogenate aromatic containing polymers without causing polymer scission. The catalysts of the present invention are also cost-effective catalysts and have a low catalytic metal loading on a low pore-volume support.

[0073] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.