A method for preparing styrene using polystyrene waste

Abstract

The present invention discloses a method for preparing styrene using polystyrene waste, comprising the following steps: A. heating the polystyrene waste to a molten state, defoaming and injecting it into a cracking furnace; B. pre-filling a catalyst in the cracking furnace, injecting molten polystyrene, and then heating and cracking the polystyrene; C. the cracking gas flows from the cracking furnace into a condenser for cooling and condensation; D. distilling and purifying the condensate to obtain styrene monomer. The present invention can improve the deficiencies of the prior art, reduce the condensation and reflux of the cracking gas in the cracking furnace during the cracking of polystyrene, and improve the yield of styrene.

Description

Technical Field

[0001] The invention relates to the technical field of resource utilization of polystyrene waste, in particular to a method for preparing styrene by using polystyrene waste. Background Art

[0002] Styrene is a widely used chemical raw material. Styrene can be produced by heating and cracking polystyrene waste. However, in the existing preparation process, the cracking gas will produce obvious condensation reflux during the rising process, which will lead to secondary degradation in the cracking process and reduce the yield of styrene. How to solve this problem and improve the yield of styrene has become one of the problems to be solved in this field. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing styrene using polystyrene waste, which can solve the shortcomings of the prior art, reduce the condensation and reflux of cracking gas in the cracking furnace during the cracking process of polystyrene, and improve the yield of styrene.

[0004] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0005] A method for preparing styrene using polystyrene waste comprises the following steps:

[0006] A. Heat the polystyrene waste to a molten state, defoam and inject it into a cracking furnace;

[0007] B. Pre-filling the catalyst in the cracking furnace, injecting molten polystyrene, and then heating and cracking the polystyrene;

[0008] C. The cracking gas flows from the cracking furnace into the condenser for cooling and condensation;

[0009] D. The condensate is purified by distillation to obtain styrene monomer.

[0010] Preferably, the catalyst is a transition metal oxide molecular sieve, and the filling amount is 30% to 50% of the cracking furnace volume.

[0011] Preferably, the distillation pressure is 4 to 6 × 10 3 Pa, 0.1% hydroquinone was added to the condensate before distillation.

[0012] Preferably, the cracking furnace includes a furnace body, a catalyst tray is arranged at the bottom of the furnace body, an aeration plate is installed at the bottom of the catalyst tray, the aeration plate is connected to the first nitrogen delivery pipe, an insulation board is installed in the middle of the furnace body, a plurality of through holes are arranged on the insulation board, a raw material injection pipe and a first heater are installed between the insulation board and the catalyst tray, a second heater is installed above the insulation board, an inclined surface is arranged on the top of the furnace body, and a cracking gas exhaust pipe is installed at the connection between the bottom edge of the inclined surface and the side wall of the furnace body.

[0013] Preferably, a second nitrogen delivery pipe is installed on the top edge of the inclined surface, the gas outlet direction of the second nitrogen delivery pipe is parallel to the inclined surface, and a preheater is installed on the outer side of the second nitrogen delivery pipe.

[0014] Preferably, the edge of the heat insulation board is provided with a mesh area.

[0015] Preferably, the reaction temperature below the insulation board is 380-400°C, the reaction temperature above the insulation board is 450-470°C, the reaction pressure in the furnace is 0.1 MPa, and the heating temperature of the preheater is 470-480°C.

[0016] The beneficial effects brought about by adopting the above technical scheme are: the present invention optimizes the structure of the cracking furnace and uses a layered heating cracking reaction process of the upper and lower layers. Low-temperature cracking is used in the lower layer to reduce the influence of high temperature on the catalyst activity and the proportion of side reactions. At the same time, by filling nitrogen at the bottom, the problem of carbon deposition on the furnace wall is effectively avoided. High-temperature cracking is used in the upper layer to effectively reduce the condensation and reflux of the cracking gas. Since the residence time of the cracking gas on the upper part of the insulation board is short and normal pressure cracking is adopted, the higher reaction temperature will not significantly increase the production of other gasification products. The top of the cracking furnace adopts an inclined design, which can make the cracking gas and the nitrogen ejected from the second nitrogen delivery pipe produce counter-flow, further reduce the condensation and reflux of the cracking gas, so that the cracking gas is quickly discharged from the cracking gas exhaust pipe. The mesh area at the edge of the insulation board can guide part of the nitrogen at the bottom to flow upward from the vicinity of the furnace wall to reduce carbon deposition on the furnace wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of a specific implementation mode of the present invention.

[0018] Figure 2 It is a structural diagram of a cracking furnace in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0019] Example

[0020] A method for preparing styrene using polystyrene waste comprises the following steps:

[0021] A. Heat the polystyrene waste to a molten state, defoam and inject it into a cracking furnace;

[0022] B. Pre-filling a catalyst in a cracking furnace, injecting molten polystyrene, and then heating and cracking the polystyrene; the catalyst is a transition metal oxide molecular sieve, and the filling amount is 50% of the cracking furnace volume;

[0023] C. The cracking gas flows from the cracking furnace into the condenser for cooling and condensation;

[0024] D. The condensate is distilled and purified to obtain styrene monomer; the distillation pressure is 5.5×10 3 Pa, 0.1% hydroquinone was added to the condensate before distillation.

[0025] The cracking furnace comprises a furnace body 1, a catalyst tray 2 is arranged at the bottom of the furnace body 1, an aeration plate 3 is installed at the bottom of the catalyst tray 2, a first nitrogen delivery pipe 4 is connected to the aeration plate 3, a heat insulation board 5 is installed in the middle of the furnace body 1, a plurality of through holes 6 are arranged on the heat insulation board 5, a raw material injection pipe 7 and a first heater 8 are installed between the heat insulation board 5 and the catalyst tray 2, a second heater 9 is installed above the heat insulation board 5, a slope 10 is arranged at the top of the furnace body 1, and a cracking gas exhaust pipe 11 is installed at the connection between the bottom edge of the slope 10 and the side wall of the furnace body 1. A second nitrogen delivery pipe 12 is installed at the top edge of the slope 10, the gas outlet direction of the second nitrogen delivery pipe 12 is parallel to the slope 10, and a preheater 13 is installed outside the second nitrogen delivery pipe 12. A mesh area 14 is arranged at the edge of the heat insulation board 5.

[0026] The reaction temperature below the insulation plate 5 is 385°C, the reaction temperature above the insulation plate 5 is 470°C, the reaction pressure in the furnace body 1 is 0.1 MPa, and the heating temperature of the preheater 13 is 475°C.

[0027] Comparative Example

[0028] This comparative example is modified on the basis of the embodiment, specifically using a conventional cracking furnace of the prior art, with a cracking reaction temperature of 360° C. and a reaction pressure of 0.04 MPa.

[0029] After comparative experiments, the styrene yield of the embodiment of the present invention is 72.4%, and the styrene yield of the comparative example is 54.9%. The cracking process provided by the present invention can effectively improve the yield of styrene.

[0030] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0031] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing styrene using polystyrene waste, characterized in that The following steps are involved: A. Heat the polystyrene waste to a molten state, defoam and inject it into a cracking furnace; B. Pre-filling the catalyst in the cracking furnace, injecting molten polystyrene, and then heating and cracking the polystyrene; The cracking furnace comprises a furnace body (1), a catalyst tray (2) is arranged at the bottom of the furnace body (1), an aeration plate (3) is installed at the bottom of the catalyst tray (2), the aeration plate (3) is connected to a first nitrogen delivery pipe (4), a heat insulation plate (5) is installed in the middle of the furnace body (1), a plurality of through holes (6) are arranged on the heat insulation plate (5), a raw material injection pipe (7) and a first heater (8) are installed between the heat insulation plate (5) and the catalyst tray (2), and a first heating element (8) is installed above the heat insulation plate (5). A second heater (9) is provided, a slope (10) is provided on the top of the furnace body (1), a cracking gas exhaust pipe (11) is installed at the connection between the bottom edge of the slope (10) and the side wall of the furnace body (1); a second nitrogen delivery pipe (12) is installed on the top edge of the slope (10), the gas outlet direction of the second nitrogen delivery pipe (12) is parallel to the slope (10), and a preheater (13) is installed on the outside of the second nitrogen delivery pipe (12); and a mesh area (14) is provided on the edge of the heat insulation board (5); The reaction temperature below the heat insulation plate (5) is 380-400°C, the reaction temperature above the heat insulation plate (5) is 450-470°C, the reaction pressure in the furnace body (1) is 0.1 MPa, and the heating temperature of the preheater (13) is 470-480°C; C. The cracking gas flows from the cracking furnace into the condenser for cooling and condensation; D. The condensate is purified by distillation to obtain styrene monomer.

2. The method for preparing styrene using polystyrene waste according to claim 1, characterized in that: The catalyst is a transition metal oxide molecular sieve, and the filling amount is 30% to 50% of the cracking furnace volume.

3. The method for preparing styrene using polystyrene waste according to claim 2, characterized in that: The distillation pressure is 4~6×10 3 Pa, 0.1% hydroquinone was added to the condensate before distillation.

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