Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – From nonhydrocarbon feed
Reexamination Certificate
1998-04-29
2001-02-13
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
From nonhydrocarbon feed
C585S639000, C585S640000, C585S641000, C585S642000, C204S157150, C204S157600
Reexamination Certificate
active
06187983
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a catalytic process of converting an oxygenate feed to olefins in the presence of an electromagnetic energy.
BACKGROUND OF THE INVENTION
Light olefins (defined herein as ethylene, propylene, butenes and mixtures thereof) serve as feeds for the production of numerous chemicals and polymers. Light olefins traditionally are produced by petroleum cracking. Due to the escalating cost of crude petroleum, efforts to develop light olefin production technologies based on alternative feedstocks have increased.
An important type of alternative feedstocks are oxygenates, such as alcohols, particularly methanol, dimethyl ether, dimethyl carbonate and ethanol. Alcohols may be produced by fermentation, or from synthesis gas derived from natural gas, petroleum liquids, carbonaceous materials, including coal, recycled plastics, municipal wastes, or any organic material. Because of the wide variety of sources, alcohols, alcohol derivatives, and other oxygenates have promise as an economical, non-petroleum source for olefin production.
Because olefins, particularly light olefins, are the most sought after products from oxygenate conversion and catalytic petroleum cracking processes, a continuing need exists for new catalysts, new ways of making known catalysts, and/or new processes to:
increase the yield of olefin products;
increase the yield of light olefin products;
reduce the yield of unwanted products such as heavy hydrocarbons having molecular weights heavier than butane or low-valued by-products like methane;
reduce coke formation;
increase catalyst performance—life, maintenance, activity, selectivity, stability; and
regenerate spent catalyst more easily and/or more efficiently.
SUMMARY OF THE INVENTION
The present invention provides a process of contacting an oxygenate feed with a catalyst in the presence of electromagnetic energy at a sufficient power and under conditions effective to convert said oxygenate feed to a product comprising olefins.
DETAILED DESCRIPTION OF THE INVENTION
In the process of converting an oxygenate feed to olefins, it is desirable to increase the yield of and selectivity to olefins, reduce the production of byproducts, reduce coke formation, improve catalyst performance, and regenerate the spent catalyst more easily and/or more efficiently. The present invention provides a process of converting a oxygenate feed to olefins in the presence of electromagnetic energy. Many aspects of the oxygenate conversion process are improved.
Most catalysts that are used in oxygenate conversion and petroleum cracking processes are molecular-sieve containing catalysts. Molecular sieves generally comprise a stable crystalline framework structure enclosing cavities of molecular dimensions. The cavities form a well-defined microporous system of cages and one-, two- and/or three-dimensional channels. The channels may or may not be connected with one another. The cavities or pores in a given type of molecular sieve have well-defined dimensions which will only allow molecules up to a certain size to enter the pores. The pores can be as small as about 3 Angstroms and as large as about 15 Angstroms or larger. Most catalytic reactions are believed to take place inside of these pores.
The present invention should achieve many of the desired improvements by substantially any molecular sieve catalyst, regardless of the structure type or pore size. Preferred molecular sieve catalysts for use according to the present invention comprise “small” and “medium” pore molecular sieve catalysts. “Small pore” molecular sieve catalysts are defined as catalysts with pores having a diameter of less than about 5.0 Angstroms. “Medium pore” molecular sieve catalysts are defined as catalysts with pores having a diameter in the range of from about 5.0 to about 13.0 Angstroms.
A molecular sieve catalyst can be zeolitic or non-zeolitic. Zeolitic molecular sieve catalysts suitable for the use in the present invention with varying degree of effectiveness include, but are not necessarily limited to AEI, CHA, ERI, FAU, LOV, MON, RHO, THO, MFI, FER, AEL, MEL, and substituted examples of these structural types, as described in W. M. Meier and D. H. Olson,
Atlas of Zeolitic Structural Types
(Butterworth Heineman—3rd ed. 1997), incorporated herein by reference.
Preferred zeolite catalysts include but are not necessarily limited to zeolite A, zeolite X, zeolite Y, zeolite USY, ZSM-5, ZSM-11, ZSM-22, ZSM-34, MCM-41, erionite, chabazite, mordenite, zeolite L, zeolite beta, borosilicates and mixtures thereof.
Zeolites possess acidity as a result of the difference in valences between the two major framework elements—silicon (valence of 4+) and aluminum (valence of 3+). It is believed that zeolites can have both Lewis acid sites which accept electron donating moieties, and Bronsted acid sites which donate protons (H
+
ions). Most catalytic reactions take place at or near various acidic sites.
Zeolites may be used in the present invention as synthesized or the zeolites may be modified with a variety of modifiers or treatments. These modifiers may change the acidity, the nature of acid sites, pore size, pore size distribution, crystallinity, surface area, and other properties of the zeolites. Metal ions such as alkali metal ions, alkaline earth metal ions, transition metal ions, and ions of B, Ge, Sn, Ti, Zr, and others, can be incorporated into either the zeolite framework and/or outside the framework. Calcination, hydrothermal treatment, treatment with oxidizing and/or reducing agents, and treatment with acids such as HF, HCl, and chelating agents, also can be carried out to alter the physical and chemical properties of zeolites.
Non-zeolitic molecular sieves also are suitable for use in the present invention. Silicoaluminophosphates (SAPO's), metal aluminophosphates (MeAPO's), and metal aluminophosphosilicon oxides (MeAPSO's) have been synthesized and investigated as catalysts for converting oxygenate feeds or cracking heavy hydrocarbons to light olefins. Aluminophosphate molecular sieves (ALPO's) also may be used in the present invention too. These non-zeolitic molecular sieves collectively are referred to herein as “SAPO type” molecular sieves.
SAPO type molecular sieves have a three-dimensional microporous crystalline framework of PO
2
+
, AlO
2
−
, SiO
2
and MeO
2
m
tetrahedral units, with or without metals in the framework. The “m” superscript represents a net electric charge depending on the valence state of the metal, Me. When Me has valence state of +2, +3, +4, +5, or +6 valence state, m is −2, −1, 0, +1, and +2, respectively. “Me” includes, but is not necessarily limited to Zn, Mg, Mn, Co, Ni, Ga, Fe, Ti, Zr, Ge, Sn, Cr, and mixtures thereof.
Because an aluminophosphate (AlPO
4
) framework inherently is neutral in electrical charges, the incorporation of silicon or other metallic or nonmetallic elements into the framework by substitution generates more active catalytic sites, particularly acid sites and increased acidity. Controlling the quantity and location of silicon atoms and other elements incorporated into an AlPO
4
framework is important in determining the catalytic properties of a particular SAPO type molecular sieve. Properly adjusted acid strength, acidity distribution, and acid site density are the keys to forming a good oxygenate conversion or petroleum cracking catalyst.
The catalytic properties can be modified after the SAPO type molecular sieve catalyst has been synthesized. “Post-synthesis” modification is accomplished by treating the molecular sieve with metallic, semi-metallic or non-metallic materials comprising nickel, cobalt, manganese, beryllium, magnesium, calcium, strontium, barium, lanthanides, actinides, fluorine, chlorine, chelating agents, and others. The modifiers may or may not become part of the final composition of the modified catalyst.
In the present invention, SAPO type molecular sieves suitable for converting an oxygenate feed t
Exxon Chemical Patents Inc
Griffin Walter D.
Keller Bradley
Russell Linda
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