Method for preparing a light olefin using an oxygen-containing compound, and device for use thereof

Abstract

A method for preparing a light olefin using an oxygen-containing compound, and a device for use thereof, more specifically, taking methanol and/or dimethyl ether as main starting materials, using a multi-stage (n≧2) dense phase fluidized bed reactor and a multi-stage (m≧2) catalyst regenerator, which solves the problem in the prior art of the uniformity of catalyst carbon deposition and the carbon content being difficult to control and the light olefin selectivity being low.

Claims

1. A method for preparing a light olefin using an oxygen-containing compound, comprising the following steps: step a) in which a raw material comprising the oxygen-containing compound is introduced in parallel from n feeding branch lines into 1.sup.st to n.sup.th secondary reaction zones in a dense phase fluidized bed reactor, and is brought into contact with a catalyst to generate a light olefin product-containing stream and a spent catalyst, wherein said catalyst is sequentially passed through 1.sup.st to n.sup.th secondary reaction zones, with the carbon content thereof increasing gradually, and wherein said dense phase fluidized bed reactor is divided by a material flow controller into n secondary reaction zones; step b) in which the light olefin product-containing stream flowed out from the 1.sup.st to n.sup.th secondary reaction zones is separated from the spent catalyst that it carries; said light olefin product-containing stream is passed into a product separation section, and after separation and purification, a light olefin product is obtained; the isolated spent catalyst is passed into the n.sup.th secondary reaction zone; and step c) in which the spent catalyst flowed out from the n.sup.th secondary reaction zone, after being stripped and lifted, is passed into a dense phase fluidized bed regenerator for regeneration; said spent catalyst is sequentially passed through 1.sup.st to m.sup.th secondary regeneration zones; a regeneration medium is introduced in parallel from m feeding branch lines of regeneration zone into the 1.sup.st to m.sup.th secondary regeneration zones; the spent catalyst is brought into contact with the regeneration medium, with the carbon content thereof decreasing gradually; after the completion of the regeneration, the catalyst is returned back to the 1.sup.st secondary reaction zone via stripping and lifting; wherein the dense phase fluidized bed regenerator is divided by a material flow controller into m secondary regeneration zones; wherein n≧2 and m≧2.

2. The method according to claim 1, wherein 8≧n≧3 and 8≧m≧3.

3. The method according to claim 1, wherein, in the dense phase fluidized bed reactor, the apparent linear velocity of gas in the material flow controller is less than or equals to the minimum fluidizing velocity of the catalyst.

4. The method according to claim 1, wherein, in the dense phase fluidized bed regenerator, the apparent linear velocity of gas in the material flow controller is less than or equals to the minimum fluidizing velocity of the catalyst.

5. The method according to claim 1, wherein the catalyst comprises SAPO-34 molecular sieve.

6. The method according to claim 1, wherein the reaction conditions in the dense phase fluidized bed reaction zone are as follows: the apparent linear velocity of gas is 0.1-1.5 m/s, the reaction temperature is 400-550° C., and the bed density is 200-1200 kg/m.sup.3.

7. The method according to claim 1, wherein the average carbon deposition amount of the catalyst is increased sequentially in the 1.sup.st to n.sup.th secondary reaction zones of the dense phase fluidized bed, wherein the average carbon deposition amount of the catalyst in the 1.sup.st secondary reaction zone is 0.5-3 wt %, and the average carbon deposition amount of the catalyst in the n.sup.th secondary reaction zone is 7-10 wt %.

8. The method according to claim 1, wherein the reaction conditions in the dense phase fluidized bed regeneration zone are as follows: the apparent linear velocity of gas is 0.1-1.5 m/s, the regeneration temperature is 500-700° C., and the bed density is 200-1200 kg/m.sup.3.

9. The method according to claim 1, wherein the average carbon deposition amount of the catalyst is decreased sequentially from the 1.sup.st to m.sup.th secondary regeneration zones of the dense phase fluidized bed regeneration zone, wherein the average carbon deposition amount of the catalyst in the 1.sup.st secondary regeneration zone is 3-10 wt %, and the average carbon deposition amount of the catalyst in the m.sup.th secondary regeneration zone is 0-3 wt %.

10. The method according to claim 1, wherein the oxygen-containing compound is methanol and/or dimethyl ether; the light olefin is any one of ethylene, propylene or butylene, or a mixture thereof; and the regeneration medium is any one of air, oxygen-deficient air or water vapor, or a mixture thereof.

11. The method according to claim 1, said dense phase fluidized bed reactor comprising a reaction zone, a gas-solid separation zone, and a stripping zone, wherein the reaction zone is divided by a material flow controller into n secondary reaction zones, wherein n≧2.

12. The method according to claim 1, the dense phase fluidized bed regenerator comprising a regeneration zone, a gas-solid separation zone, and a stripping zone, wherein the regeneration zone is divided by a material flow controller into m secondary regeneration zones, wherein m≧2.

13. The method according to claim 11, wherein 8≧n≧3.

14. The method according to claim 11, wherein, in the dense phase fluidized bed reactor, the apparent linear velocity of gas in the material flow controller is less than or equals to the minimum fluidizing velocity of the catalyst.

15. The method according to claim 11, wherein the reaction conditions in the dense phase fluidized bed reaction zone are as follows: the apparent linear velocity of gas is 0.1-1.5 m/s, the reaction temperature is 400-550° C., and the bed density is 200-1200 kg/m.sup.3.

16. The method according to claim 11, wherein the average carbon deposition amount of the catalyst is increased sequentially in the 1.sup.st to n.sup.th secondary reaction zones of the dense phase fluidized bed, wherein the average carbon deposition amount of the catalyst in the 1.sup.st secondary reaction zone is 0.5-3 wt %, and the average carbon deposition amount of the catalyst in the n.sup.th secondary reaction zone is 7-10 wt %.

17. The method according to claim 12, wherein 8≧m≧3.

18. The method according to claim 12, wherein, in the dense phase fluidized bed regenerator, the apparent linear velocity of gas in the material flow controller is less than or equals to the minimum fluidizing velocity of the catalyst.

19. The method according to claim 12, wherein the reaction conditions in the dense phase fluidized bed regeneration zone are as follows: the apparent linear velocity of gas is 0.1-1.5 m/s, the regeneration temperature is 500-700° C., and the bed density is 200-1200 kg/m.sup.3.

20. The method according to claim 12, wherein the average carbon deposition amount of the catalyst is decreased sequentially from the 1.sup.st to m.sup.th secondary regeneration zones of the dense phase fluidized bed regeneration zone, wherein the average carbon deposition amount of the catalyst in the 1.sup.st secondary regeneration zone is 3-10 wt %, and the average carbon deposition amount of the catalyst in the m.sup.th secondary regeneration zone is 0-3 wt %.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1 is a schematic flow chart of the method in the present disclosure;

(2) FIG. 2 is a structural schematic diagram of the dense phase fluidized bed comprising 4 secondary reaction zones in the present disclosure, wherein the arrows in the A-A sectional view show the flow direction of the catalyst between the secondary reaction zones;

(3) FIG. 3 is a structural schematic diagram of the dense phase fluidized bed comprising 4 secondary regeneration zones in the present disclosure, wherein the arrows in B-B sectional view show the flow direction of the catalyst between the secondary regeneration zones;

(4) FIG. 4 is a structural schematic diagram of the stripper in the present disclosure;

(5) FIG. 5 is a structural schematic diagram of the material flow controller in the present disclosure.

(6) The reference signs of the figures are illustrated as follows: 1: reactor feed line; 1-1: feeding branch line of 1.sup.st secondary reaction zone; 1-2: feeding branch line of 2.sup.nd secondary reaction zone; 1-3: feeding branch line of 3.sup.rd secondary reaction zone; 1-4: feeding branch line of 4.sup.th secondary reaction zone; 2: dense phase fluidized bed reactor; 2-1: 1.sup.st secondary reaction zone; 2-2: 2.sup.nd secondary reaction zone; 2-3: 3.sup.rd secondary reaction zone; 2-4: 4.sup.th secondary reaction zone; 3: cyclone separator; 4: product material line; 5: stripper; 6: water vapor line; 7: lift pipe; 8: lifting gas line; 9: regenerator feed line; 9-1: feeding branch line of 1.sup.st secondary regeneration zone; 9-2: feeding branch line of 2.sup.nd secondary regeneration zone; 9-3: feeding branch line of 3.sup.rd secondary regeneration zone; 9-4: feeding branch line of 4.sup.th secondary regeneration zone; 10: dense phase fluidized bed regenerator; 10-1: 1.sup.st secondary regeneration zone; 10-2: 2.sup.nd secondary regeneration zone; 10-3: 3.sup.rd secondary regeneration zone; 10-4: 4.sup.th secondary regeneration zone; 11: cyclone separator; 12: exhaust gas line; 13: stripper; 14: water vapor line; 15: lift pipe; 16: lifting gas line; 17: material flow controller; 18: material overflow port; 19: partition plate; 20: orifice; 21: material downward flow pipe; 22: bottom baffle; 23: heat extraction member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) In order to increase the selectivity for light olefins in the process of preparation of a light olefin using an oxygen-containing compound, the present disclosure provides a method for preparing a light olefin using an oxygen-containing compound, comprising the following steps: a) a step in which a raw material comprising the oxygen-containing compound is introduced in parallel from n feeding branch lines into 1.sup.st to n.sup.th secondary reaction zones in a dense phase fluidized bed reactor, and is brought into contact with a catalyst to generate a light olefin product-containing stream and a spent catalyst, wherein said catalyst is sequentially passed through 1.sup.st to n.sup.th secondary reaction zones, with the carbon content thereof increasing gradually, and wherein said dense phase fluidized bed reactor is divided by a material flow controller into n secondary reaction zones; b) a step in which the light olefin product-containing stream flowed out from the 1.sup.st to n.sup.th secondary reaction zones is separated from the spent catalyst that it carries; said light olefin product-containing stream is passed into a product separation section, and after separation and purification, a light olefin product is obtained; the isolated spent catalyst is passed into the n.sup.th secondary reaction zone; and c) a step in which the spent catalyst flowed out from the n.sup.th secondary reaction zone, after being stripped and lifted, is passed into a dense phase fluidized bed regenerator for regeneration; said spent catalyst is sequentially passed through 1.sup.st to m.sup.th secondary regeneration zones; a regeneration medium is introduced in parallel from m feeding branch lines of regeneration zone into the 1.sup.st to m.sup.th secondary regeneration zones; the spent catalyst is brought into contact with the regeneration medium, with the carbon content thereof decreasing gradually; after the completion of the regeneration, the catalyst is returned back to the 1.sup.st secondary reaction zone via stripping and lifting; wherein the dense phase fluidized bed regenerator is divided by a material flow controller into m secondary regeneration zones.

(8) Wherein n≧2, preferably 8≧n≧3; m≧2, preferably 8≧m≧3.

(9) Preferably, in the dense phase fluidized bed reactor, the apparent linear velocity of gas in the material flow controller is less than or equals to the minimum fluidizing velocity of the catalyst.

(10) Preferably, in the dense phase fluidized bed regenerator, the apparent linear velocity of gas in the material flow controller is less than or equals to the minimum fluidizing velocity of the catalyst.

(11) Preferably, the catalyst comprises SAPO-34 molecular sieve.

(12) Preferably, the reaction conditions of the reaction zone in the dense phase fluidized bed are as follows: the apparent linear velocity of gas is 0.1-1.5 m/s, reaction temperature is 400-550° C., the bed density is 200-1200 kg/m.sup.3; the average carbon deposition amount of the catalyst in the 1.sup.st secondary reaction zone is 0.5-3 wt %, and the average carbon deposition amount of the catalyst in the n.sup.th secondary reaction zone is 7-10 wt %.

(13) Preferably, the reaction conditions in the dense phase fluidized bed regeneration zone are as follows: the apparent linear velocity of gas is 0.1-1.5 m/s, the regeneration temperature is 500-700° C., and the bed density is 200-1200 kg/m.sup.3; the average carbon deposition amount of the catalyst is decreased sequentially from the 1.sup.st to m.sup.th secondary regeneration zones, the average carbon deposition amount of the catalyst in the 1.sup.st secondary regeneration zone is 3-10 wt %, and the average carbon deposition amount of the catalyst in the m.sup.th secondary regeneration zone is 0-3 wt %.

(14) Preferably, the oxygen-containing compound is methanol and/or dimethyl ether; the light olefin is any one of ethylene, propylene or butylene, or a mixture thereof; the regeneration medium is any one of air, oxygen-deficient air or water vapor, or a mixture thereof.

(15) The technical solution provided in the present disclosure may further comprises:

(16) (1) providing a dense phase fluidized bed reactor, comprising a reaction zone, a gas-solid separation zone, and a stripping zone, the reaction zone being divided by a material flow controller into n secondary reaction zones, wherein n≧2;

(17) (2) providing a dense phase fluidized bed regenerator, comprising a regeneration zone, a gas-solid separation zone, and a stripping zone, the regeneration zone being divided by a material flow controller into m secondary regeneration zones, wherein m≧2.

(18) Preferably, the raw material comprising an oxygen-containing compound is introduced into the dense phase fluidized bed reactor and is brought into contact with regenerated catalyst, resulting in a light olefin-containing product and a carbon-containing spent catalyst, meanwhile, the regenerated catalyst is sequentially passed through 1.sup.st to n.sup.th secondary reaction zones, with the carbon content thereof increasing gradually.

(19) Preferably, via stripping and lifting, the spent catalyst flowing out from the n.sup.th secondary reaction zone is passed into the dense phase fluidized bed regenerator for regeneration, the spent catalyst is sequentially passed through 1.sup.st to m.sup.th secondary regeneration zone, and is brought into contact with the regeneration medium, with the carbon content thereof gradually decreasing, and then the catalyst is returned back to 1.sup.st secondary reaction zone via stripping and lifting.

(20) Preferably, the stream of the light olefin product is passed into separation section after separation with spent catalyst, and the isolated spent catalyst is passed into n.sup.th secondary reaction zone.

(21) In a specific embodiment, the schematic flow chart for preparing a light olefin using a oxygen-containing compound in the present disclosure is as shown in FIG. 1. The raw material comprising the oxygen-containing compound is introduced from reactor feed line (1) and breach lines (1-1, . . . , 1-n) thereof in parallel into secondary reaction zones (2-1, . . . , 2-n) in the dense phase fluidized bed reactor (2), and is brought into contact with a catalyst comprising SAPO-34 molecular sieve, to generate a gas phase product stream and a spent catalyst. The gas phase product stream and the entrained spent catalyst are passed into a cyclone separator (3), wherein the gas phase product stream flows through the outlet of the cyclone separator and the product material line (4) and enters into the subsequent separation section, the entrained spent catalyst is passed into n.sup.th secondary reaction zone (2-n) via the dipleg of the cyclone separator; the regenerated catalyst from the dense phase fluidized bed regenerator (10) is passed into the dense phase fluidized bed reactor (2) via a stripper (13) and a lift pipe (15), wherein the bottom of the stripper (13) is connected to a water vapor line (14), and the bottom of the lift pipe (15) is connected to a lifting gas line (16); the regenerated catalyst is sequentially passed through 1.sup.st to n.sup.th secondary reaction zones (2-1, . . . , 2-n) in the dense phase fluidized bed reactor (2), and forms spent catalyst after carbon deposition; the regeneration medium is introduced from regenerator feed line (9) and branch lines (9-1, . . . , 9-m) thereof into secondary regeneration zones (10-1, . . . , 10-m) in the dense phase fluidized bed regenerator (10), and is brought into contact with the spent catalyst, to generate exhaust gas and regenerated catalyst after charking, and then the exhaust gas and the entrained regenerated catalyst are passed into a cyclone separator (11), from which, the exhaust gas is passed into a tail gas processing section through the outlet of the cyclone separator and exhaust gas line (12), and is emitted after processing, and the entrained regenerated catalyst is passed into m.sup.th secondary regeneration zone (10-m) via the dipleg of the cyclone separator. The spent catalyst from the dense phase fluidized bed reactor (2) is passed into the dense phase fluidized bed regenerator (10) via a stripper (5) and a lift pipe (7), wherein the bottom of the stripper (5) is connected to a water vapor line (6), and the bottom of the lift pipe (7) is connected to a lifting gas line (8). In the dense phase fluidized bed regenerator (10), the spent catalyst is sequentially passed through 1.sup.st to m.sup.th secondary regeneration zones (10-1, . . . , 10-m), and forms a regenerated catalyst after charking.

(22) In a more specific embodiment, the structural schematic diagram of the dense phase fluidized bed reactor comprising 4 secondary reaction zones in the present disclosure is as shown in FIG. 2. Three material flow controllers (17) and one baffle are vertically provided to separate the dense phase fluidized bed reaction zone into 4 secondary reaction zones. The catalyst is sequentially passed through the 1.sup.st to the 4.sup.th secondary reaction zones and is then passed into the stripper.

(23) In a more specific embodiment, the structural schematic diagram of the dense phase fluidized bed regenerator comprising 4 secondary regeneration zones in the present disclosure is as shown in FIG. 3. Three material flow controllers (17) and one baffle are vertically provided to separate the regeneration zone into 4 secondary regeneration zones. The catalyst is sequentially passed through the 1.sup.st to the 4.sup.th secondary regeneration zones and is then passed into the stripper.

(24) In a more specific embodiment, the structural schematic diagram of the stripper in the present disclosure is as shown in FIG. 4. The opening on the tube wall on the upper part of the stripper is a material overflow port (18) between n.sup.th secondary reaction zone (or m.sup.th secondary regeneration zone) and the stripper.

(25) In a more specific embodiment, the structural schematic diagram of the material flow controller in the present disclosure is as shown in FIG. 5. The material flow controller (17) is composed of a partition plate (19), an orifice (20), a material downward flow pipe (21), a bottom baffle (22) and a heat extraction member (23). The catalyst is passed into the material downward flow pipe from the top of the downward flow pipe, wherein the apparent linear velocity of gas is less than or equals to the minimal fluidizing velocity, the catalyst in the material downward flow pipe is in a dense phase packing state, and a material flow driving force is formed to drive the catalyst to flow into a next secondary reaction zone (or regeneration zone) via the orifice. A coil structure may be used as the heat extraction member, which is fixed onto the partition plate.

(26) Preferably, in the above technical solutions, the apparent linear velocity of gas in the dense phase fluidized bed reaction zone is 0.1-1.5 m/s; the apparent linear velocity of gas in the dense phase fluidized bed regeneration zone is 0.1-1.5 m/s; the apparent linear velocity of gas in the material flow controller is less than or equals to the minimum fluidizing velocity of the catalyst; the catalyst includes SAPO-34 molecular sieve; a feed inlet is provided at the bottom of the reaction zone, and the feed includes methanol, dimethyl ether etc.; the stripping medium in the stripper includes water vapor; an inlet for regeneration medium is provided at the bottom of the regeneration zone, and the regeneration medium includes air, oxygen-deficient air, water vapor etc.; the reaction temperature in the reaction zone is 400-550° C., the bed density is 200-1200 kg/m.sup.3, the average amount of carbon deposition on the catalyst increases sequentially from 1.sup.st to n.sup.th secondary reaction zones, the average amount of carbon deposition in the 1.sup.st secondary reaction zone is 0.5-3 wt %, the average amount of carbon deposition in the n.sup.th secondary reaction zone is 7-10 wt %; the reaction temperature in the regeneration zone is 500-700° C., the bed density is 200-1200 kg/m.sup.3, the average amount of carbon deposition on the catalyst decreases sequentially from 1.sup.st to m.sup.th secondary regeneration zones, the average amount of carbon deposition in the 1.sup.st secondary regeneration zone is 3-10 wt %, and the average amount of carbon deposition in the m.sup.th secondary regeneration zone is 0-3 wt %. Using the method of the present disclosure, the object of controlling the amount of carbon deposition on catalyst, improving the uniformity of the carbon content and increasing the selectivity for light olefins can be achieved. Therefore, it has significant technical advantages, and is useful in the industrial production of light olefins.

(27) For better illustrating the present disclosure, and facilitating the understanding of the technical solution of the present disclosure, the exemplary but non-limiting examples of the present disclosure are provided as follows.

Example 1

(28) 4 secondary reaction zones were provided in the dense phase fluidized bed reactor, and 4 secondary regeneration zones were provided in the dense phase fluidized bed regenerator. The raw material comprising an oxygen-containing compound was passed into the dense phase fluidized bed reactor and was brought into contact with a catalyst comprising SAPO-34 molecular sieve, to generate a gas phase product stream and a spent catalyst. The gas phase material and the entrained spent catalyst were passed into a cyclone separator. The gas phase product stream was passed into a subsequent separation section via an outlet of the cyclone separator, and the entrained spent catalyst was passed into 4.sup.th secondary reaction zone via the dipleg of the cyclone separator. The regenerated catalyst was passed into the dense phase fluidized bed reactor through a stripper and a lift pipe, and sequentially passed through 1.sup.st to 4.sup.th secondary reaction zones, forming a spent catalyst after carbon deposition. The spent catalyst was further passed into the dense phase fluidized bed regenerator through a stripper and lift pipe, and sequentially passed through 1.sup.st to 4.sup.th secondary regeneration zones, forming a regenerated catalyst after charking. The reaction conditions in the dense phase fluidized bed reactor were as follows: the reaction temperature was 400° C., the linear velocity of gas was 0.3 m/s, the bed density was 1000 kg/m.sup.3, the average amount of carbon deposition in the 1.sup.st secondary reaction zone was 2 wt %, the average amount of carbon deposition in 2.sup.nd secondary reaction zone was 6 wt %, the average amount of carbon deposition in 3.sup.rd secondary reaction zone was 8 wt %, and the average amount of carbon deposition in 4.sup.th secondary reaction zone was 10 wt %; the reaction conditions in the dense phase fluidized bed regenerator were as follows: the reaction temperature was 500° C., the linear velocity of gas was 0.3 m/s, the bed density was 1000 kg/m.sup.3, the average amount of carbon deposition in 1.sup.st secondary regeneration zone was 7 wt %, the average amount of carbon deposition in 2.sup.nd secondary regeneration zone was 4 wt %, the average amount of carbon deposition in 3.sup.rd secondary regeneration zone was 2 wt %, and the average amount of carbon deposition in 4.sup.th secondary regeneration zone was 1 wt %. The reaction product was analyzed by on-line gas phase chromatography, and the carbon based yield of light olefins was 91.1 wt %.

Example 2

(29) 3 secondary reaction zones were provided in the dense phase fluidized bed reactor, and 2 secondary regeneration zones were provided in the dense phase fluidized bed regenerator. The raw material comprising an oxygen-containing compound was passed into the dense phase fluidized bed reactor and was brought into contact with a catalyst comprising SAPO-34 molecular sieve, to generate a gas phase product stream and a spent catalyst. The gas phase material and the entrained spent catalyst were passed into a cyclone separator, the gas phase product stream was passed into a subsequent separation section via an outlet of the cyclone separator, and the entrained spent catalyst was passed into 3.sup.rd secondary reaction zone through the dipleg of the cyclone separator. The regenerated catalyst was passed into the dense phase fluidized bed reactor through a stripper and a lift pipe, and sequentially passed through 1.sup.st to 3.sup.rd secondary reaction zones, forming a spent catalyst after carbon deposition. The spent catalyst was passed into the dense phase fluidized bed regenerator through a stripper and lift pipe, and sequentially passed through 1.sup.st to 2.sup.nd secondary regeneration zone, forming a regenerated catalyst after charking. The reaction conditions in the dense phase fluidized bed reactor were as follows: the reaction temperature was 450° C., the linear velocity of gas was 0.5 m/s, the bed density was 900 kg/m.sup.3, the average amount of carbon deposition in 1.sup.st secondary reaction zone was 3 wt %, the average amount of carbon deposition in 2.sup.nd secondary reaction zone was 7 wt %, and the average amount of carbon deposition in 3.sup.rd secondary reaction zone was 9 wt %; the reaction conditions in the dense phase fluidized bed regenerator were as follows: the reaction temperature was 600° C., the linear velocity of gas was 0.7 m/s, the bed density was 700 kg/m.sup.3, the average amount of carbon deposition in 1.sup.st secondary regeneration zone was 4 wt %, and the average amount of carbon deposition in 2.sup.nd secondary regeneration zone was 2 wt %. The reaction product was analyzed by on-line gas phase chromatography, and the carbon based yield of light olefins was 90.5 wt %.

Example 3

(30) 6 secondary reaction zones were provided in the dense phase fluidized bed reactor, and 5 secondary regeneration zones were provided in the dense phase fluidized bed regenerator. The raw material comprising an oxygen-containing compound was passed into the dense phase fluidized bed reactor, and was brought into contact with a catalyst comprising SAPO-34 molecular sieve, to generate a gas phase product stream and a spent catalyst. The gas phase material and the entrained spent catalyst were passed into a cyclone separator, the gas phase product stream was passed into a subsequent separation section via an outlet of the cyclone separator, and the entrained spent catalyst was passed into 6.sup.th secondary reaction zone via the dipleg of the cyclone separator. The regenerated catalyst was passed into the dense phase fluidized bed reactor through a stripper and a lift pipe, and sequentially passed through 1.sup.st to 6.sup.th secondary reaction zones, forming a spent catalyst after carbon deposition. The spent catalyst was further passed into the dense phase fluidized bed regenerator through a stripper and a lift pipe, and sequentially passed through 1.sup.st to 5.sup.th secondary regeneration zones, forming a regenerated catalyst after charking. The reaction conditions in the dense phase fluidized bed reactor were as follows: the reaction temperature was 480° C., the linear velocity of gas was 0.7 m/s, the bed density was 700 kg/m.sup.3, the average amount of carbon deposition in 1.sup.st secondary reaction zone was 1 wt %, the average amount of carbon deposition in 2.sup.nd secondary reaction zone was 3 wt %, the average amount of carbon deposition in 3.sup.rd secondary reaction zone was 4 wt %, the average amount of carbon deposition in 4.sup.th secondary reaction zone was 5 wt %, the average amount of carbon deposition in 5.sup.th secondary reaction zone was 6 wt %, and the average amount of carbon deposition in 6.sup.th secondary reaction zone was 7 wt %; the reaction conditions in the dense phase fluidized bed regenerator were as follows: the reaction temperature was 650° C., the linear velocity of gas was 1.0 m/s, the bed density was 500 kg/m.sup.3, the average amount of carbon deposition in 1.sup.st secondary regeneration zone was 5 wt %, the average amount of carbon deposition in 2.sup.nd secondary regeneration zone was 3 wt %, the average amount of carbon deposition in 3.sup.rd secondary regeneration zone was 2 wt %, the average amount of carbon deposition in 4.sup.th secondary regeneration zone was 1 wt %, and the average amount of carbon deposition in 5.sup.th secondary regeneration zone was 0.01 wt %. The reaction product was analyzed by on-line gas phase chromatography, and the carbon based yield of light olefins was 91.4 wt %.

(31) The present invention has been described in detail above, but the invention is not limited to the specific embodiments described herein. It will be appreciated by those skilled in the art that other modifications and variations can be made without departing from the scope of the invention. The scope of the invention is defined by the appended claims.