Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2003-02-20
2004-08-24
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S479000, C568S485000
Reexamination Certificate
active
06781018
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
This invention relates to a process for production of formaldehyde, and optionally also methyl formate as a co-product, by oxidation of dimethyl ether (DME), and to catalysts for use in the process, including catalysts that are novel per se. In addition, this invention relates to the use of such novel catalysts in other processes.
Formaldehyde is widely used as an intermediate or basic building block in the commercial synthesis of many chemicals. Because of the existence of large reserves of methane worldwide it has been considered desirable for some time to develop processes to convert methane to more valuable chemicals. One such effort has been in the area of direct conversion of methane to formaldehyde via selective oxidation. However, this has not been particularly successful. Up to now, all such processes have resulted in low yields due to the tendency of the formaldehyde so produced being further oxidized to carbon oxides under the severe reaction conditions required for methane oxidation.
Instead, formaldehyde is commercially produced from methane indirectly, for instance, by first converting the methane to synthesis gas (CO and H
2
), then reacting that to form methanol, and finally oxidizing the methanol to produce formaldehyde. The oxidation of methanol to formaldehyde has been extensively studied, and is the dominant process today for formaldehyde synthesis, typically using silver- or iron/molybdenum-based catalysts.
Another possible route to formaldehyde involves the oxidation of dimethyl ether (CH
3
OCH
3
) via cleavage of the C—O—C linkages. This process, however, has not been widely studied.
Dimethyl ether is a generally environmentally benign molecule. Its physical properties resemble those of LPG (liquefied petroleum gases), and dimethyl ether thus can be transported within existing and developing LPG infrastructures. Like methanol, dimethyl ether can be produced from synthesis gas. These characteristics give it the potential to be a new, clean alternative fuel. This potential is expected to lead to the production of substantially larger quantities of dimethyl ether than in the past, thus making it available for use as an intermediate in production of other chemicals, including formaldehyde.
Several patents disclose processes for producing formaldehyde from dimethyl ether using various catalysts. U.S. Pat. No. 2,075,100 describes such a process using a number of comparatively mild oxidation catalysts including platinum wire or foil, palladium black, and metals such as gold, silver, and copper. Vanadium pentoxide and iron, chromium and uranium sesqui-oxides are termed “very suitable”. U.S. Pat. No. 3,655,771 describes using catalysts containing tungsten oxide, alone or optionally with no more than 10% of an additive. The additives mentioned include bismuth, selenium, molybdenum, vanadium, phosphorus and boron oxides, as well as phosphoric acid, ammonium phosphate and ammonium chloride.
More recently, U.S. Pat. No. 4,435,602 describes a process for production of formaldehyde from dimethyl ether using naturally occurring manganese nodules as a catalyst. U.S. Pat. No. 4,439,624 describes such a process using an intimate mixture of bismuth, molybdenum and copper oxides, preferably prepared by coprecipitation. U.S. Pat. No. 4,442,307 describes such a process using an intimate mixture of bismuth, molybdenum and iron oxides, similarly prepared. U.S. Pat. No. 6,256,528 describes oxidation of dimethyl ether with a catalyst containing metallic silver to produce a mixture of products including formaldehyde, light alkanes, carbon oxides and water. Information in these patents indicates that formaldehyde was produced with reasonable yields, but that overoxidation of that product to carbon oxides occurred to an undesirable degree.
As described above, it would be advantageous to provide a process and associated process technology for production of formaldehyde from dimethyl ether with good conversion and good selectivity to formaldehyde. Preferably such a process could be operated without the occurrence of substantial direct oxidation of dimethyl ether to carbon oxides or further oxidation of product formaldehyde to carbon oxides, thus improving the chemical and energy efficiency of the process.
BRIEF SUMMARY OF THE INVENTION
In brief, in one aspect, this invention comprises a process for the production of formaldehyde by oxidation of dimethyl ether in the presence of a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides. The support is one that substantially does not react with the molybdenum or vanadium oxide to form unreducible mixed oxide(s). Preferred supports comprise alumina, zirconia, stannic oxide, titania, silica, ferric oxide, ceric oxide, other reducible metal oxides, and mixtures and combinations thereof.
In one preferred embodiment this invention comprises such a process in which the molybdenum and/or vanadium oxides are dispersed on the surface of the support, the surface density of the oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and in which the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides.
Most preferably the surface density of the molybdenum and/or vanadium oxide or oxides on the support is approximately that of a monolayer of the oxide or oxides at the surface of the support.
In another preferred embodiment, the catalyst comprises one or more reducible metal oxides. More preferably in this embodiment, the catalyst comprises a layer of the reducible metal oxide or oxides, most preferably stannic oxide, on a particulate support (preferably alumina and/or zirconia) with the molybdenum and/or vanadium oxide or oxides being present as an upper layer or layers on the layer of reducible metal oxide(s) layer. In this embodiment, preferably the surface density of the molybdenum and/or vanadium oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides. Most preferably the surface density of the molybdenum and/or vanadium oxide or oxides on the support is approximately that of a monolayer of the oxide or oxides at the surface of the support.
Catalysts of the above type in which the catalyst comprises one or more reducible metal oxides, particularly stannic oxide, and more particularly in which the molybdenum and/or vanadium oxide is supported on a layer or layers of reducible metal oxide or oxides, with the oxide layer or layers being disposed on a particulate alumina and/or zirconia, are novel and form another feature of this invention.
Yet another aspect of this invention is the use of the novel catalysts just described to catalyze other processes, particularly oxidation of methanol to formaldehyde, oxidative dehydrogenation of alkanes, and oxidation of alkenes.
DETAILED DESCRIPTION OF THE INVENTION
In brief, a primary aspect of this invention comprises a process for the production of formaldehyde by oxidation of dimethyl ether in the presence of a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides. Preferably the oxides are supported on alumina (Al
2
O
3
) and/or zirconia (ZrO
2
), and more preferably on such a support that also includes one or more reducible metal oxides, as described herein. Preferably, the molybdenum and/or vanadium oxides are dispersed on the surface of the support, the surface density of the oxide or oxides on the support is greater than that for the isolated monomeric oxide or oxides, and the catalyst is characterized by a substantial absence of bulk crystalline molybdenum or vanadium oxides. More preferably the molybdenum and//or vanadium oxides are dispersed on a layer or layers of a reducible oxide or oxides that is further supported on alumina, titania, silica or zirconia (if zirconia is not used as the above-mentioned layer).
Iglesia Enrique
Liu Haichao
Barts Samuel
The Regents of the University of California
Townsend and Townsend / and Crew LLP
Witherspoon Sikarl A.
LandOfFree
Process and catalyst for production of formaldehyde from... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and catalyst for production of formaldehyde from..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and catalyst for production of formaldehyde from... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3293892