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Publication numberWO2003062196 A2
Publication typeApplication
Application numberPCT/US2003/001873
Publication date31 Jul 2003
Filing date22 Jan 2003
Priority date23 Jan 2002
Also published asWO2003062196A3
Publication numberPCT/2003/1873, PCT/US/2003/001873, PCT/US/2003/01873, PCT/US/3/001873, PCT/US/3/01873, PCT/US2003/001873, PCT/US2003/01873, PCT/US2003001873, PCT/US200301873, PCT/US3/001873, PCT/US3/01873, PCT/US3001873, PCT/US301873, WO 03062196 A2, WO 03062196A2, WO 2003/062196 A2, WO 2003062196 A2, WO 2003062196A2, WO-A2-03062196, WO-A2-2003062196, WO03062196 A2, WO03062196A2, WO2003/062196A2, WO2003062196 A2, WO2003062196A2
InventorsMichiel Makkee, Aalbert Zwijnenburg, Jacob Adriaan Moulijn
ApplicantHuntsman International Llc
Export CitationBiBTeX, EndNote, RefMan
External Links: Patentscope, Espacenet
Gas-phase process and catalyst for the preparation of propylene oxide
WO 2003062196 A2
Abstract
Gas-phase process for the preparation of propylene oxide comprising contacting propylene with oxygen and hydrogen in the presence of a catalyst comprising a bimetallic compound supported on a titanium containing support, the bimetallic compound comprising gold and a metal M selected from the group consisting of platinum, tin, and rhodium. The invention also provides for the catalyst.
Claims  (OCR text may contain errors)
ClaimsWhat is claimed:
1. A gas-phase process for the preparation of propylene oxide comprising contacting propylene with oxygen and hydrogen in the presence of a catalyst, wherein the catalyst comprises a bimetallic compound supported on a titanium containing support, the bimetallic compound comprising gold and a metal M selected from the group consisting of platinum, tin, and rhodium.
2. The gas-phase process according to claim 1, wherein the metal M is platinum.
3. A gas-phase process according to claim 1, wherein the bimetallic compound has a metal M:gold molar ratio in the range from 0.01:0.99 to 0.10:0.90.
4. The gas-phase process according to claim 2, wherein the bimetallic compound has a platinum.-gold molar ratio of about 0.05:0.95.
5. The gas-phase process according to claim 1, wherein the titanium containing support comprises titanium oxide and silicon oxide.
6. The gas-phase process according to claim 1, wherein the bimetallic compound is deposited on the titanium containing support by a deposition-precipitation method.
The gas-phase process according to claim 1, wherein the catalyst comprises from 0.1 to 5 weight percent of bimetallic compound, based on the total weight of the catalyst .
The gas-phase process according to claim 1, wherein the catalyst comprises from 0.5 to 1.5 weight percent of bimetallic compound, based on the total weight of the catalyst .
The gas-phase process according to claim 1, wherein the gas-phase process is carried out in the presence of a diluent gas.
10. The gas-phase process according to claim 1, wherein the gas-phase process is carried out at a temperature in the range from 50C to 250C.
11. The gas-phase process according to claim 1, wherein the gas-phase process is carried out at a temperature in the range from 75C to 200C.
12. A gas-phase process for the preparation of propylene oxide comprising contacting propylene with oxygen and hydrogen in the presence of a catalyst, wherein the catalyst comprises platinum and gold with a platinum:gold molar ratio of about 0.5:0.95 on a support comprising titanium oxide and silicon oxide, the platinum and gold being deposited on support by the deposition-precipitation method.
13. The gas-phase process according to claim 12, wherein the catalyst comprises about 1 weight percent of gold and platinum, based on the total weight of the catalyst, and the gas-phase process is carried out in the presence of nitrogen as a diluent gas and at a temperature of about 100 C.
14. A catalyst for use in a gas-phase process for the preparation of propylene oxide, wherein the catalyst comprises a bimetallic compound supported on a titanium containing support, wherein the bimetallic compound comprises gold and a metal M selected from the group consisting of platinum, tin, and rhodium.
15. The catalyst according to claim 14, wherein the metal M is platinum.
16. The catalyst according to claim 14, wherein the bimetallic compound has a metal M:gold molar ratio in the range from 0.01:0.99 to 0.10:0.90.
17. The catalyst according to claim 15, wherein the bimetallic compound has a platinum: gold molar ratio of about 0.05:0.95.
18. The catalyst according to claim 14, wherein the titanium containing support comprises titanium oxide and silicon oxide.
19. The catalyst according to claim 14, wherein the bimetallic compound is deposited on the titanium- containing support by a deposition-precipitation method.
20. The catalyst according to claim 14, wherein the catalyst comprises from 0.1 to 5 weight percent of bimetallic compound, based on the total weight of the catalyst .
21. The catalyst according to claim 14, wherein the catalyst comprises from 0.5 to 1.5 weight percent of bimetallic compound, based on the total weight of the catalyst .
22. A catalyst for use in a gas-phase process for the preparation of propylene oxide, the catalyst comprising a bimetallic compound supported on a titanium containing support, wherein the bimetallic compound comprises platinum and gold and has a platinum: gold molar ratio of about 0.5:0.95, the titanium-containing support comprises titanium oxide and silicon oxide, and the bimetallic compound is deposited on the support by the deposition-precipitation method.
23. The catalyst according to claim 22, wherein the catalyst comprises about 1 weight percent of bimetallic compound, based on the total weight of the catalyst.
Description  (OCR text may contain errors)

GAS-PHASE PROCESS AND CATALYST FOR THE PREPARATION

OF PROPYLENE OXIDE

Cross Reference to Related Applications This application claims priority to U.S. Provisional Application Serial No. 60/351,111, which was filed on January 23, 2002.

Field of the Invention This invention relates to a gas-phase process for the preparation of propylene oxide, also called hydro-oxidation of propylene with hydrogen and oxygen or epoxidation of propylene using hydrogen and oxygen. The invention also relates to a catalyst that can be used for the preparation of propylene oxide.

Background of the Invention

It is known to prepare propylene oxide by direct oxidation of propylene with oxygen in the presence of hydrogen and a catalyst comprising gold supported on a titanium substrate. Prior art representative of such a process includes WO 98/00413, WO 98/00414, WO 98/00415, U.S. Patent No. 5965754, and U.S. Patent No. 6031116. These disclosures exemplify the uses or titanium dioxide, titania coated silica and various titanosilicates. However, very low conversions of propylene are reported in these disclosures

(typically 0.2-0.3 v/v %) , although selectivity in the region of 99% is claimed. The best results are reported in

US 5965754, where example 1 gives propylene conversion of 1.5% with selectivity to propylene oxide of 92% at 145C.

The results of a study of the epoxidation of propylene were also disclosed in "Selective Vapor-Phase Epoxidation of Propylene over Au/Ti02 Catalysts in the Presence of Oxygen and Hydrogen", Journal of Catalysis 178, 566-575 (1998), article CA982157.

More recently, WO 00/59633 described the preparation of gold catalysts for the epoxidation of propylene, wherein the gold is at least partially oxidized; and WO 00/59632 disclosed a process for the hydro-oxidation of propylene to propylene oxide using catalysts containing both titanium and at least partially oxidized gold and with a propylene conversion of 3.5% and a selectivity to propylene oxide of 92.6% (see example 7).

Although the production of propylene oxide from propylene, oxygen, and hydrogen has been extensively studied over the past 5-6 years in both industry and universities, the overall propylene conversion remains still low. Another drawback is the production of water through the direct reaction of hydrogen and oxygen, leading to poor raw material efficiencies in the processes that have been proposed so far. Reducing the excess of production of water is a key technical obstacle that must be overcome for the successful implementation of this technology.

Therefore, an object of this invention is to provide a process that enables the preparation of propylene oxide with a high selectivity to propylene oxide and a reduced water production.

Summary of the Invention Accordingly, the invention resides in a gas-phase process for the preparation of propylene oxide comprising contacting propylene with oxygen and hydrogen in the presence of a catalyst comprising a bimetallic compound supported on a titanium containing support, wherein the bimetallic compound comprises gold and a metal M selected from the group consisting of platinum, tin, and rhodium. In one embodiment of the invention, the bimetallic compound comprises platinum and gold and has a platinum: gold molar ratio in the range from 0.01:0.99 to 0.10:0.90, and preferably of about 0.05:0.95. In a further embodiment, the bimetallic compound is deposited on the titanium-containing support by a deposition-precipitation method.

The invention also resides in a catalyst for the preparation of propylene oxide, comprising a bimetallic compound supported on a titanium containing support, wherein the bimetallic compound comprises gold and a metal M selected from the group consisting of platinum, tin and rhodium.

Other objects, features and advantages will become more apparent after referring to the following specification and accompanying drawings.

Brief Description of the Drawings

Figure 1 represents micrographs of a catalyst of the invention (b) and a control catalyst (a) . Figure 2 is a graph showing the yield of propylene oxide and the water/propylene oxide molar ratio as a function of the Au fraction in the Pt-Au bimetallic compound of a catalyst of the invention at 75C.

Figure 3 is a graph showing the yield of propylene oxide and the water/propylene oxide molar ratio as a function of the Au fraction in the Pt-Au bimetallic compound of the catalyst of the invention at 100 C.

Figure 4 is a graph showing the yield of propylene oxide as a function of the yield of water, when using various bimetallic compounds in the catalyst for the epoxidation of propylene.

Figure 5 is a graph showing the yield of propylene oxide as a function of the yield of propane, when using various bimetallic compounds in the catalyst for the epoxidation of propylene.

Detail Description of the Invention A gas-phase process for the preparation of propylene oxide comprising contacting propylene with oxygen and hydrogen in the presence of a catalyst comprising a bimetallic compound supported on a titanium containing support. The titanium-containing support may take a variety of forms. Preferably, the titanium in the support exists essentially as non-metallic titanium. Details concerning the titanium-containing support that may be used in the invention can be found in WO 00/59632 (page 8, line 27 to page 15, line 27) , which is herein incorporated by reference.

According to the invention, the bimetallic compound supported by the titanium-containing support comprises gold and a metal M selected from the group consisting of platinum, tin and rhodium. A generally advantageous metal M:gold molar ratio is in the range from 0.01:0.99 to

0.10:0.90, and preferably is about 0.05:0.95. Preferably, the metal M is platinum.

Although there is no limitation on the method of incorporating the bimetallic compound onto the titanium- containing support, the deposition-precipitation method is generally preferred. This method is described, for example, by R. Meiers, U. Dingerdissen and W.F. Hόlderich in Journal of Catalysis, 176,376(1998).

The bimetallic compound loading of the support can be any amount that yields an active catalyst in the process of this invention. Generally, the bimetallic compound loading is in the range from 0.1 to 5 and preferably from 0.5 to 1.5 weight percent, based on the total weight of the catalyst. In carrying out the process of the invention, the quantity of propylene employed can vary over a wide range. Generally, the quantity of propylene depends upon the specific process features, including, for example, the design of the reactor and economic and safety considerations. Those skilled in the art know how to determine a suitable range of propylene concentrations for the specific process features.

Oxygen is also required for the process, and any source of oxygen is acceptable, including air or essentially pure molecular oxygen. Other sources of oxygen may be suitable, including ozone and nitrogen oxides, such as nitrous oxide. Molecular oxygen is preferred. The quantity of oxygen employed can vary over a wide range provided that the quantity is sufficient for producing the desired propylene oxide .

Hydrogen is also required for the process, and any source of hydrogen can be used in the process, including, for example molecular hydrogen obtained from the dehydrogenation of hydrocarbons or alcohols. In an alternative embodiment of this invention, the hydrogen may be generated in si tu in the propylene oxidation reactor, for example, by dehydrogenating propane. Any quantity of hydrogen can be employed in the process provided that the amount is sufficient to produce propylene oxide.

It may be desirable to employ a diluent, although the use thereof is optional. Because the process is exothermic, a diluent beneficially provides a means of removing and dissipating the heat produced. In addition, the diluent provides an expanded concentration regime in which the reactants are non-flammable. The diluent can be any gas that does not inhibit the process. Suitable diluents include, but are not limited to, helium, nitrogen, argon, methane, carbon dioxide, steam, and mixtures thereof. Most of these gases are essentially inert with respect to the process disclosed herein.

The process may be conducted in a reactor of any conventional design suitable for gas-phase processes.

The process conditions for the epoxidation can vary considerably. Usually, the process is conducted at a temperature that ranges from 50C to 250C, and preferably from 75C to 225C. Usually, the pressure ranges from about atmospheric to 30bar.a and preferably from atmospheric to 20bar.a

In flow reactors, the residence time of the reactants and the molar ratio of reactants to catalyst are determined by the space velocity. Typically, the weight hourly space velocity (WHSV) is greater than 0.2 .propylene/g. catalyst/hr preferably greater than 0.6 g .propylene/g . catalys /hr .

The most preferred embodiment of the process of the invention comprises the following features: (a) the bimetallic compound comprises platinum and gold and has a platinum: gold molar ratio of about 0.5:0.95; (b) the titanium-containing support comprises titanium oxide and silicon oxide; and (c) the bimetallic compound is deposited on the support by the deposition-precipitation method. Additional preferred features may also be the following ones: (a) the catalyst comprises about 1 weight percent of bimetallic compound, based on the total weight of the catalyst; and (b) the process is carried out in the presence of nitrogen as a diluent gas and at a temperature around 100C.

Another aspect of the invention is a catalyst that can be used in the gas-phase process of the invention. The catalyst comprises a bimetallic compound supported on a titanium containing support, wherein the bimetallic compound comprises gold and a metal M selected from the group consisting of platinum, tin and rhodium.

The catalyst of the invention may have some or all of the advantageous features as aforementioned in connection with the gas-phase process of the invention and which are summarized as follows: (a) the metal M of the bimetallic compound is platinum; (b) in the bimetallic compound, the molar ratio metal M:gold is in the range from 0.01:0.99 to 0.10:0.90, and preferably is about 0.05:0.95; (c) the titanium containing support comprises titanium oxide and silicon oxide; (d) the bimetallic compound has been deposited on the titanium-containing support by a deposition-precipitation method; (e) the catalyst comprises from 0.1 to 5 and preferably from 0.5 to 1.5 weight percent of bimetallic compound, based on the total weight of the catalyst .

The most preferred catalyst of the invention comprises the following features: (a) the bimetallic compound comprises platinum and gold and has a platinum:gold molar ratio of about 0.5:0.95; (b) the titanium-containing support comprises titanium oxide and silicon oxide; and (c) the bimetallic compound is deposited on the support by the deposition-precipitation method. An additional preferred feature may also be the bimetallic compound content of about 1 weight percent based on the total weight of the catalyst .

The following examples are provided to illustrate the invention, but it should be understood that these examples are given for the purpose of illustration only, and are not intended to limit the invention. Examples

Example 1 (invention) : Preparation of a Pt-Au/Ti02/Si02 catalyst Gold and platinum were deposited on a Ti02/Si02 support by the deposition-precipitation method as follows. A 1.6 wt . % Ti02 (0.1 monolayer) Ti02/Si02 support was prepared by reaction of titanium (IV) ethoxide (Fluka, 97 %) in 2-propanol with surface hydroxyls of Si02 (Aldrich Davisil 646) based on the method described by Rajadhyaksha and co-workers in Applied Catalysis, 51,67(1989). Diffuse Reflectance UN-Vis Spectroscopy confirmed that the Ti02/Si02 support did not contain anatase (only a band of isolated tetrahedral Ti at 230 nm was observed) , indicating a high dispersion of Ti species. The Ti02/Si02 support was dispersed in water

(approximately 10 ml per gram of support) to which ammonia was added to raise the pH to a value between 9 and 10. An aqueous solution of AuCl3 and H2PtCl6 was prepared with a molar ratio Pt:Au = 5:95. Over a period of 2 hours, the solution was added dropwise to the support suspension under vigorous stirring. The mixture was stirred for another half an hour after which it was centrifuged and washed with at least ten times its own volume of distilled water. The platinum-gold-loaded catalyst thus obtained was then dried at 80C for 2 hours and calcined at 400C for 4 hours. This catalyst comprised 1 weight percent of bimetallic (platinum- gold) compound, based on the total weight of the catalyst.

Example 2 (control) : Preparation of a Pd-Au/Ti02/Si02 catalyst A Pd-Au/Ti02/Si02 catalyst was prepared in the same way as in Example 1, except that PdCl2 was used instead of the Pt salt. This catalyst comprised 1 weight percent of bimetallic (palladium-gold) compound, based on the total weight of the catalyst. Example 3 (comparative) : Micrographs of the catalysts

Transmission electron microscopy (TEM) was performed using a Philips CM30T electron microscope with an LaB6 filament as the source of electrons operated at 300 kV. Samples were mounted on a carbon polymer microgrid supported on a copper grid by placing a few droplets of a suspension of grounded sample in ethanol on the grid, followed by drying at ambient conditions.

The TEM micrographs are given in Figure 1, wherein the micrograph (a) corresponds to the control catalyst of Example 2 and the micrograph (b) corresponds to the catalyst according to the invention as prepared in Example 1. The micrographs show homogeneously distributed metal particles up to 5 nm. No separate Pt or Pd metal particles were found. XRF (X-ray fluorescence) analysis confirmed the presence of Pd and Pt in the bimetallic samples and EDX (energy dispersive X-ray analysis) indicated the presence of Pd or Pt in the Au particles.

Example 4 (control) :Preparation of an Au/Ti02/Si02 catalyst

A Au/Ti02/Si02 catalyst was prepared in the same way as in example 1, except that the aqueous solution contained only AuCl3. This catalyst comprised 1 weight percent of gold, based on the total weight of the catalyst.

Example 5 (comparative) : Epoxidation of propylene

Steady-state experiments were performed in a microflow set-up. In this set-up, nitrogen (70% vol) , oxygen (10% vol) , hydrogen (10% vol) and propylene (10% vol) were continuously fed over a 10 ml fixed-bed reactor placed in a fluidized-bed oven. The analysis of the reaction products was performed using an automated sampling gas chromatograph and analyzing a gas sample every 12 minutes. The column used for the analysis was a Poraplot Q (0.53 mm diameter and 25 m length capillary column) with He as carrier gas. An FID detector (flame ionization detector) was used for the analysis. This configuration was able to separate all oxygenated organic components . The hydrogen and oxygen consumption was measured on the same gas chromatograph using a Molsieve 5 A (2 mm diameter, 3 m length column) with a TCD detector (thermal conductivity detector) . The results are summarized in the following table, wherein PO means propylene oxide.

propylene expressed as a percentage

Propane (%) means the moles of obtained propane/moles of fed propylene expressed as a percentage

H20/P0 means the number of moles of water obtained/number of moles of PO obtained

The term "conversion" is herein defined as the mole percentage of propylene that reacts to form products . The term "selectivity" is herein defined as the mole percentage of reacted propylene that forms a particular product, desirably propylene oxide.

It can be seen that both Pt and Pd induce hydrogenation of propylene to the unwanted propane. However, the Pd-Au catalyst only shows hydrogenation activity to H20 and propane, but no epoxidation activity. The addition of Pt leads to the formation of some propane at temperatures of 100C or higher, but this catalyst exhibits less water formation in comparison to the Au-only catalyst. The molar ratio of H20 to PO is much smaller (9.3) for the Pt-modified catalyst than for the Au-only sample (30) .

Example 6 (invention) : Effect of Pt concentration The PO yield and water/PO mole ratio were measured as a function of the Pt concentration. The following table summarizes the results obtained at 75 C.

propylene expressed as a percentage

Propane (%) means the moles of obtained propane/moles of fed propylene expressed as a percentage

H20/PO means the number of moles of water obtained/number of moles of PO obtained

These results are also shown on Figure 2

The following table summarizes the results obtained at

100C.

(*) : PO (%) means the moles of obtained PO/moles of fed propylene expressed as a percentage

Propane (%) means the moles of obtained propane/moles of fed propylene expressed as a percentage

H20/PO means the number of moles of water obtained/number of moles of PO obtained

These results are also shown on Figure 3

It appears that the gas-phase process of the invention is more effective at 100C than at 75C.

Example 7 (comparative)

The catalyst of example 4 (supported Au only) was compared to other catalysts prepared as in Example 1, having a metal :Au ratio of 0.05:0.95 and a bimetallic content of 1 wt% based on the total weight of the catalyst. The tested metals were Pt, Pd, Sn, Rh, Cd, Ag, Ir, Hg, Zn, Pb and Cu. The PO and water yields (%) were measured in the following conditions :

temperature: 100 C hydrogen/oxygen/propylene/nitrogen molar ratio : 1:1:1:7 productivity : WHSV = 0 . 71 gPropylene/gcatalyst/h In Figure 4, the PO yield (%) was plotted versus the water yield (%) . As one can see, only the Pt-Au, Sn-Au and

Rh-Au catalysts give satisfactory results in terms of relatively high PO yield and low water yield, Pt-Au being the most satisfactory bimetallic compound.

Example 8 (comparative)

The catalyst of Example 4 (supported Au only) was compared to other catalysts prepared as in Example 1, having a metal: Au ratio of 0.05:0.95 and a bimetallic content of 1 wt% based on the total weight of the catalyst. The tested metals were Pt, Pd, Sn, Rh, Cd, Ag, Ir, Hg, Zn, Pb and Cu. The PO and water yields (%) were measured in the following conditions :

temperature: 100C hydrogen/oxygen/propylene/nitrogen molar ratio : 1:1:1:7 productivity : WHSV = 0 . 71 gPropylene/gcatalySt/h

In Figure 5, the PO yield (%) was plotted versus the propane yield (%) . As one can see, only the Pt-Au and Sn-Au catalysts give satisfactory results in terms of relatively high PO yield and low propane yield, Pt-Au being the most satisfactory bimetallic compound.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US5821394 *15 Nov 199513 Oct 1998SolvayProcess for converting a chlorinated alkane into a less chlorinated alkene
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
WO2015162562A121 Apr 201529 Oct 2015Sabic Global Technologies B.V.Method for the synthesis of supported gold (au) nanoparticles for epoxidation reactions
US818339926 Mar 200822 May 2012Dow Global Technologies LlcIntegrated hydro-oxidation process with separation of an olefin oxide product stream
US82883117 Nov 200716 Oct 2012Dow Global Technologies LlcHydro-oxidation process using a catalyst prepared from a gold cluster complex
Classifications
International ClassificationB01J21/06, C07D301/10, B01J23/68, B01J23/42, B01J37/03, B01J23/52
Cooperative ClassificationY02P20/52, C07D301/10, B01J37/031, B01J21/063, B01J23/52, B01J23/68, B01J23/42
European ClassificationC07D301/10, B01J23/52, B01J37/03B
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