Chemistry of hydrocarbon compounds – Plural serial diverse syntheses – Same catalyst – solvent – or component thereof used in both...
Reexamination Certificate
2000-06-14
2001-10-16
Tran, Hien (Department: 1764)
Chemistry of hydrocarbon compounds
Plural serial diverse syntheses
Same catalyst, solvent, or component thereof used in both...
C585S312000, C585S311000, C585S314000, C585S315000, C585S324000, C585S328000, C585S329000, C585S330000, C585S639000, C585S648000, C585S653000
Reexamination Certificate
active
06303839
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the production of light olefins from an oxygenate feedstream.
BACKGROUND OF THE INVENTION
Light olefins have traditionally been produced through the process of steam or catalytic cracking. Because of the limited availability and high cost of petroleum sources, the cost of producing light olefins from such petroleum sources has been steadily increasing. Light olefins serve as feeds for the production of numerous chemicals. As the emerging economies of the Third World strain toward growth and expansion, the demand for light olefins will increase dramatically.
The search for alternative materials for light olefin production has led to the use of oxygenates such as alcohols and, more particularly, to the use of methanol, ethanol, and higher alcohols or their derivatives. These alcohols may be produced by fermentation or from synthesis gas. Synthesis gas can be produced from natural gas, petroleum liquids, and carbonaceous materials including coal, recycled plastics, municipal wastes, or any organic material. Thus, alcohol and alcohol derivatives may provide non-petroleum based routes for the production of olefin and other related hydrocarbons.
Molecular sieves such as the microporous crystalline zeolite and non-zeolitic catalysts, particularly silicoaluminophospbates (SAPO), are known to promote the conversion of oxygenates to hydrocarbon mixtures. Numerous patents describe this process for various types of these catalysts: U.S. Pat. Nos. 3,928,483; 4,025,575; 4,252,479; 4,496,786; 4,547,616; 4,677,243; 4,843,183; 4,499,314; 4,447,669; 5,095,163; 5,191,141; 5,126,308; 4,973,792; and 4,861,938.
The process may be generally conducted in the presence of one or more diluents which may be present in the oxygenate feed in an amount between about 1 and about 99 molar percent, based on the total number of moles of all feed and diluent components fed to the reaction zone (or catalyst). Diluents include—but are not limited to—helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water, paraffins, hydrocarbons (such as methane and the like), aromatic compounds, or mixtures thereof. U.S. Pat Nos. 4,861,938 and 4,677,242 particularly emphasize the use of a diluent combined with the feed to the reaction zone to maintain sufficient catalyst selectivity toward the production of light olefin products, particularly ethylene. The above U.S. patents are hereby incorporated by reference.
U.S. Pat. No. 5,026,935 discloses a process for the preparation of ethylene from C
4
or higher feed by the combination of cracking and metathesis to form ethylene and propylene and at least a portion of the propylene is metathesized to ethylene. U.S. Pat. No. 4,590,174 discloses an olefin metathesis process employing a catalyst comprising an inorganic refractory oxide support containing at least one of tungsten oxide and molybdenum oxide and a promoting agent for the disproportionation reaction. Example 3 of U.S. Pat. No. 3,723,562 describes the conversion of propylene to a mixture of ethylene and butenes using a WO
3
-SiO
2
catalyst containing about 8 weight percent tungsten oxide. Conditions used were 800° F., 100 psig and 15 hr
−1
WHSV. Propylene conversion was 19 percent with 37.6 percent selectivity to ethylene and 62.4 percent selectivity to butenes. U.S. Pat. No. 3,723,562 is hereby incorporated by reference.
CA-1,219,882 discloses a process for the production of 1-butene from C
4
hydrocarbon mixtures containing 2-butene. The C
4
hydrocarbon mixture is isomerized in a reaction zone to 1-butene in the presence of an acid catalyst. The isomerization zone effluent is distilled to recover a hydrogen offgas, a 1-butene side-draw product, and 2-butene in a bottom stream. The bottom stream is recycled to the isomerization zone for the further isomerization of the 2-butene to 1-butene. The process is operated in the absence of steam without significant cracking or skeletal isomerization.
International Patent Application No. 93/13013 to Kvisle et al. relates to an improved method for producing a silicon-alumino-phosphate catalyst which is more stable to deactivation by coking. The patent discloses that after a period of time, all such catalysts used to convert methanol to olefin (MTO) lose the active ability to convert methanol to hydrocarbons primarily because the microporous crystal structure is coked; that is, filled up with low volatility carbonaceous compounds which block the pore structure. The carbonaceous compounds can be removed by conventional methods such as combustion in air. In a paper by T. Inui titled “Structure-Reactivity Relationships in Methanol to Olefins Conversion on Various Microporous Crystalline Catalysts,” which was included in
Structure
-
Activity and Selectivity Relationships in Heterogeneous Catalysis,
edited by R. K. Grasselli and A. W. Sleight, Elsevier Science Publishers B.V., Amsterdam, 1991, on pages 233-242, Inui discloses the highest reported ratio of ethylene/propylene produced from methanol over a SAPO-34 catalyst as about 15:1 (see
FIG. 4
, page 240).
Generally, the ratio of ethylene/propylene on a carbon basis varies from about 0.1 to about 10 and, more typically, varies from about 0.8 to about 2.5. Furthermore, ethylene and propylene yields are reduced by the production of heavier hydrocarbons such as C
4
and C
5
olefins. This narrow band limits the flexibility of the process and the value of the net products produced. Methods are sought to alter the product distribution of the MTO process for making light olefins to provide processing flexibility and overcome the equilibrium limitations of aluminophosphate catalyst of the MTO process. Methods are sought to reduce the production of C
4
and C
5
olefins from the MTO process relative to the production of ethylene and propylene. These and other disadvantages of the prior art are overcome by the present invention, and a new improved process for conversion of oxygenates to hydrocarbons is provided.
SUMMARY OF THE INVENTION
In the present invention, a combination of a light olefin production process and a catalytic cracking process is employed to improve the amount of desirable olefin products above the equilibrium amount provided by a molecular sieve catalyst. It was discovered that the use of this combination of an aliphatic hetero compound conversion process in a first reaction zone and a secondary reaction zone, operating at an effective temperature which is elevated relative to the temperature of the first reaction zone, improved the overall yield of light olefins beyond the limitations of the molecular sieve catalyst. By operating at conditions which are favorable for the ethylene and propylene production, the yields of butylene and heavier hydrocarbons can be reduced in favor of the more profitable and desirable ethylene and propylene products and the catalyst life and stability of the aluminophosphate catalyst in the oxygenate conversion zone can be improved. Preferably, the ratio of butylene and heavier to propylene from a combination of oxygenation conversion and cracking is reduced to less than about 0.30 on a weight basis, and more preferably, the yield of butylene and heavier to propylene is reduced to less than about 0.15 on a weight basis.
The invention provides a process for the production of light olefins comprising ethylene and propylene from an oxygenate feedstock such as an alcohol or an ether. The process comprises passing an oxygenate feedstock to a fluidized reaction zone in the presence of a diluent, the feedstock having from 1 to 4 carbon atoms per molecule. The first or fluidized reaction zone contains an aluminophosphate molecular sieve catalyst at conditions effective to convert the oxygenate feedstock to a light olefin product stream comprising olefins comprising ethylene, propylene and butylene and to produce a spent aluminophosphate molecular sieve catalyst. The light olefin product stream is passed to a separation zone to separate the light olefin product stream into an ethylene stream, a propylene stream, and a
Dang Thuan D.
Molinaro Frank S.
Silverman Richard P.
Tolomei John G.
Tran Hien
LandOfFree
Process for producing polymer grade olefins 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 for producing polymer grade olefins, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing polymer grade olefins will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2588786