A method and system for isobutane oxidation

Abstract

The present invention discloses a method and a system for isobutane oxidation; the method includes: 1) mixing a gas stream rich in isobutane with a gas stream rich in nitrogen to form a first carrier gas for use; 2) uniformly mixing oxygen with the first carrier gas in proportion to obtain an oxygen-containing gas stream with an oxygen concentration of 1-10 vol%; 3) feeding the above-mentioned oxygen-containing gas stream to the bottom of a reactor to react with the liquid-phase isobutane entering the reactor to generate tert-butyl hydroperoxide. By setting a two-component carrier gas of isobutane and nitrogen in different proportions and introducing a safe concentration of oxygen into the reactor by formulation, the present invention ensures the operability and safety of the isobutane oxidation reaction. Moreover, the nitrogen circulation in the carrier gas of the present invention is separately set, and only one compressor needs to be set for a system with multiple reactors. At the same time, the liquid-phase materials of multiple oxidation reactors overflow to the next stage by gravity, eliminating the inter-stage transfer pump and reducing the equipment investment.

Description

Technical Field

[0001] The present invention relates to the field of chemical engineering, and particularly to a method for oxidizing isobutane to improve the operability and safety of liquid-phase oxidation reactions. By setting a binary carrier gas of isobutane and nitrogen in different proportions and introducing a safe concentration of oxygen into the reactor through formulation, the operability and safety of the isobutane oxidation reaction are ensured. Background Art

[0002] Tert-Butyl Hydroperoxide (TBHP) is an organic peroxide widely used as an oxidant and an initiator for free radical reactions. It is also a commonly used oxygen source for the co-oxidation process of propylene to produce propylene oxide. The large-scale industrial production of tert-butyl hydroperoxide usually uses isobutane as the raw material and molecular oxygen as the oxidant.

[0003] The currently known methods for the liquid-phase oxidation of isobutane to produce tert-butyl hydroperoxide are based on the processes for the liquid-phase non-catalytic oxidation of isobutane to produce tert-butyl hydroperoxide and tert-butanol disclosed in patents US2845461 and US3478108. American companies ARCO and Texaco also disclosed in patents US5243084 and US5399777 methods for the non-catalytic liquid-phase oxidation of isobutane with molecular oxygen to produce tert-butanol and tert-butyl hydroperoxide. Typical reaction conditions for the liquid-phase oxidation of isobutane are a reaction temperature of 100 - 150 °C, a reaction pressure of 2.0 - 4.8 MPa, directly oxidizing liquid-phase isobutane with molecular oxygen for 2 - 5 h, an isobutane conversion rate of 36 - 46%, and selectivities of TBHP and TBA of 48.0 - 53.4% and 40.2 - 47.0% respectively.

[0004] In addition to the oxidation method under liquid-phase conditions of isobutane, patent US4404406 of European company Shell discloses a method for producing tert-butyl hydroperoxide in a supercritical state. This method operates in a supercritical state, with an operating temperature higher than the critical temperature of the mixture and > 140 °C, and an operating pressure greater than the critical pressure of the mixture and > 4.8 MPag, which can significantly improve the production efficiency of TBHP per unit time and per unit reactor volume.

[0005] There are also some patent disclosures in China for improving the isobutane oxidation method. The patent CN201110113828.4 of Sinopec uses ozone as an oxidant, without the need for a catalyst, simplifies the process of isobutane oxidation, improves the conversion rate of isobutane, reduces costs, and is suitable for industrialization. There are also many patents that use catalysts to improve the conversion rate of isobutane and the selectivity of tert-butyl hydroperoxide that have been disclosed. For example, the patent CN201710467464.7 of Yuxin Chemical Industry uses an NHPI catalyst and a β-cyclodextrin modifier to improve the conversion rate and selectivity, and is environmentally friendly. The patent CN201410449806.9 of Huizhou Research Institute of Sun Yat-sen University uses a metal porphyrin compound catalyst, with mild reaction conditions and high selectivity.

[0006] In summary, currently in the field of the oxidation of isobutane to tert-butyl hydroperoxide and tert-butanol, most research focuses on optimizing process conditions, improving catalysts, and increasing production efficiency. There are also some studies on improving the reactor and process safety for the reaction of liquid-phase isobutane with molecular oxygen.

[0007] In the process flow of the liquid-phase oxidation of isobutane to prepare TBHP disclosed in the patent US5149885 of Arco, a spherical reactor is used, the reaction temperature is 137 °C, and it is carried out by the way of liquid-phase circulation heat removal. After oxygen is mixed with the liquid-phase circulating material, it enters the reactor. This process is not conducive to the control of the reactor liquid level and is extremely likely to cause the liquid level to be either full or lower than the circulating extraction line; in addition, after the circulating material is transported by the circulating pump, cavitation is extremely likely to occur; in addition, there are also difficulties in the production of large spherical reactors.

[0008] In the process flow of the liquid-phase oxidation of isobutane to prepare TBHP disclosed in the patent US5243083 of Texco, an internal circulation tower reactor is used. After oxygen is mixed with the gas-phase circulating material, it enters the middle of the tower reactor. During the upward flow, isobutane and oxygen react to form TBHP. After gas-liquid separation at the top, the liquid-phase material and fresh isobutane flow downwards from the outer ring of the reactor to form a thermosyphon cycle. This process has high requirements for equipment. Liquid-phase isobutane and oxygen are directly mixed in the reactor and are extremely likely to enter the explosion limit range.

[0009] In the process flow of the preparation of TBHP disclosed in the patent US4408081 of Shell, isobutane and oxygen are operated in a supercritical state at a reaction temperature of 145 - 165 °C and a reaction pressure of 5.5 - 10.3 MPa. A multi-stage series reaction form is used. By controlling the oxygen concentration in the reaction mixture below 0.1% M, the selectivity of tert-butyl hydroperoxide is improved. This process is not easy to operate under conditions of a relatively high oxygen concentration. This is because it is impossible to ensure that oxygen completely reacts in the reactor. When the amount of incompletely reacted oxygen increases, the preset operating conditions will not be able to ensure that the reaction material maintains the supercritical state, and when it transforms to the gas-liquid phase state, the material will fall into the explosion range.

[0010] Shandong Tianhong Chemical's patent CN116099483 discloses a tower reactor and production system for preparing tert-butyl hydroperoxide by oxidation of isobutane. The tower structure eliminates the need for a delivery pump between reactors. The nitrogen regulating component regulates the amount of nitrogen introduced into the reaction space to remove the heat of reaction, thereby preventing the material in the reaction space from reacting too violently and causing the temperature to be too high. The gas-phase oxygen concentration between the trays in the tower reactor of this process is difficult to control, making it difficult to ensure safe production.

[0011] Patent CN109928863B of Beijing Shuimu Binhua Technology Co., Ltd. discloses a reaction device and method for preparing tert-butyl alcohol and tert-butyl hydroperoxide from isobutane and oxygen. Gaseous oxygen is dissolved in a liquid reaction material in a static mixer to obtain an oxygen-containing liquid material, which is then sent to a reactor for reaction. There is no gaseous space above the reactor (full liquid level operation), which improves the safety of the reaction. Summary of the invention

[0012] The main purpose of the present application is to provide an isobutane oxidation method and system, which ensures the operability and safety of the isobutane oxidation reaction by setting a two-component carrier gas of isobutane and nitrogen in different proportions and introducing a safe concentration of oxygen into the reactor.

[0013] In order to achieve the above objectives, in a first aspect, the present application provides an isobutane oxidation method, comprising the following steps:

[0014] S1, carrier gas configuration, mixing an isobutane-rich gas flow and a nitrogen-rich gas flow in a uniform proportion to form a first carrier gas;

[0015] S2, reacting the carrier gas configuration, mixing the oxygen with the first carrier gas in a uniform proportion to form a second carrier gas, wherein the oxygen concentration is 1 to 10 vol%;

[0016] S3, oxidation reaction, the second carrier gas is introduced into the bottom of the oxidation reactor to react with the liquid isobutane in the oxidation reactor to generate tert-butyl hydroperoxide, the nitrogen ratio in the first carrier gas is adjusted to control the reaction temperature of the oxidation reactor, and the oxygen ratio in the second carrier gas is adjusted to control the oxidation rate and tail oxygen concentration.

[0017] Optionally, it also includes S4, exhaust gas and condensate circulation, the exhaust gas flowing out from the top of the oxidation reactor is condensed and compressed in sequence, the gaseous exhaust gas is used as a nitrogen-rich gas flow to configure the first carrier gas, a part of the condensed liquid exhaust gas is vaporized and used as an isobutane-rich gas flow to configure the first carrier gas, and the other part is heated and enters the oxidation reactor as a reaction raw material.

[0018] Optionally, the tail gas flowing out from the top of the oxidation reactor is condensed step by step, with the number of condensation stages being 1 to 5. The high-temperature condensate above 110 °C condensed out is returned to the oxidation reactor as reaction raw materials.

[0019] Optionally, the tail gas flowing out from the top of the oxidation reactor is heat-exchanged with liquid-phase isobutane and then condensed and compressed.

[0020] Optionally, in the nitrogen-rich gas stream in step S1, the nitrogen concentration > 80 vol%, and the oxygen concentration < 1 vol%; in the isobutane-rich gas stream, the isobutane concentration > 70 vol%.

[0021] Optionally, the content of nitrogen in the first carrier gas is 10 - 95 vol%.

[0022] Optionally, in step S3, the temperature of the oxidation reactor is maintained at 120 - 150 °C, the reaction pressure is 2.8 - 4.5 MPa, the oxidation reaction zone is provided with 1 - 10 stages, and the reaction temperature decreases step by step.

[0023] To achieve the above object, in a second aspect, a preparation system for an isobutane oxidation method includes an oxidation reactor group, an oxidation tail gas condenser connected to the tail gas outlet of the oxidation reactor group, an oxidation tail gas liquid separation tank connected to the oxidation tail gas condenser, an oxidation tail gas recycle compressor connected to the gas phase outlet of the oxidation tail gas liquid separation tank, a tail gas condensate booster pump connected to the liquid phase outlet of the oxidation tail gas liquid separation tank, an oxidation feed heating and vaporizer connected to the tail gas condensate booster pump, the material inlet of liquid-phase isobutane is connected to the oxidation feed heating and vaporizer, the gas flowing out from the gas phase outlet of the oxidation feed heating and vaporizer and the gas flowing out from the oxidation tail gas recycle compressor are mixed in proportion to form a first carrier gas, and further includes a static mixer and an oxygen supply device. The oxygen generated by the oxygen supply device is mixed with the first carrier gas in the static mixer to form a second carrier gas, the second carrier gas is connected to the oxidation reactor group, and the liquid phase outlet of the oxidation feed heating and vaporizer is connected to the oxidation reactor group.

[0024] Optionally, an oxidation tail gas heat exchanger is further provided between the oxidation reactor group and the oxidation tail gas condenser. The tail gas discharged from the oxidation reactor group is heat-exchanged with the liquid-phase isobutane material and the tail gas condensate discharged from the tail gas condensate increase pump through the oxidation tail gas heat exchanger.

[0025] Optionally, a high-temperature condensate tank is further provided between the oxidation tail gas heat exchanger and the oxidation tail gas condenser. The gas phase outlet of the high-temperature condensate tank is connected to the oxidation tail gas condenser, and the liquid phase outlet of the high-temperature condensate tank is connected to the oxidation reactor group through a high-temperature condensate pump.

[0026] An isobutane oxidation method and system provided by the present invention, compared with the prior art, has the following beneficial effects:

[0027] Gas-phase isobutane is introduced into the oxygen-carrying gas stream. The gas stream entering the reactor mainly has three components, namely oxygen, nitrogen, and isobutane. Since the isobutane vapor is the same as the liquid-phase material in the reactor, the circulation of the isobutane vapor will not cause the vaporization heat absorption of the liquid-phase material, so the reaction temperature can be guaranteed. At the same time, the regulation of the tail oxygen concentration does not require the addition of nitrogen, but can directly adjust the oxygen concentration in the inlet gas, which completely avoids the heat balance problem during the circulation of the oxygen and nitrogen components. In the gas stream entering the reactor, both the oxygen content and the nitrogen content can be flexibly adjusted. Adjusting the oxygen content can control the oxidation rate and the tail oxygen concentration, and adjusting the nitrogen content can control the reaction temperature, taking into account both the safety and operability of the oxidation reaction.

[0028] The oxygen of the present invention is pre-prepared with the carrier gas outside the reactor, and the oxygen content in the prepared gas stream is strictly controlled, which is determined by the explosion upper limit of the materials (such as isobutane / tert-butanol and other organic substances) in the reactor, but usually a suitable safety range is left for the operating point. The present invention requires that the oxygen content in the gas stream entering the reactor <= 8%. This is considered based on inherent safety. Even if there is a misoperation (such as the reaction temperature is too low and the reaction of oxygen is insufficient), it can ensure that the tail oxygen concentration in the reactor does not exceed the standard and prevent the tail gas from falling into the explosion range.

[0029] The number of isobutane oxidation reactors usually exceeds one. When multiple reactors are used, the operating temperatures and TBHP concentrations in the reactors are different, which results in different compositions of the gas phases flowing out of each reactor. If directly mixed and entered into the same compressor for pressurized circulation, the inlet gas components of multiple reactors will be the same, and it is impossible to take into account the operating temperatures and component changes of multiple reactors. Therefore, the traditional process is equipped with corresponding compressors for each reactor, resulting in a large equipment investment cost. The carrier gas of the present invention is prepared according to the operating temperature of each reactor by using a nitrogen-rich gas stream and an isobutane-rich gas stream. Even if the tail gas components of multiple reactors are different, after mixing and condensation, they will be divided into a nitrogen-rich gas stream and an isobutane-rich liquid phase. A single tail gas compressor can compress the nitrogen-rich gas stream, and then according to the requirements of each reactor, mix the nitrogen-rich gas stream with the isobutane-rich gas stream in proportion to prepare the carrier gas required by each reactor. Therefore, when multiple reactors are used, the present invention can significantly reduce the compressor investment cost.

[0030] The liquid-phase materials of multiple oxidation reactors overflow to the next stage by gravity, eliminating the inter-stage transfer pump and reducing the equipment investment. Description of the Drawings

[0031] The accompanying drawings, which form a part of this application, are used to provide a further understanding of this application, making other features, objectives, and advantages of this application more apparent. The schematic embodiments and their descriptions of this application are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0032] Figure 1 It is a schematic diagram of the reaction process shown in a preferred embodiment of the present invention.

[0033] Figure 2 It is a schematic diagram of the reaction process shown in a preferred energy-saving embodiment of the present invention.

[0034] Wherein: 101, the first oxidation reactor; 102, the second oxidation reactor; 103, the third oxidation reactor; 104, the oxidation tail gas condenser; 105, the oxidation tail gas liquid separation tank; 106, the oxidation tail gas recycle compressor; 107, the tail gas condensate booster pump; 108, the oxidation feed heating vaporizer; 109, the oxidation tail gas heat exchanger; 110, the high-temperature condensate tank; 111, the high-temperature condensate pump; 112a - 112c, static mixers; S1 - S11 are the logistics numbers. Detailed implementation manners

[0035] In order to enable those skilled in the art of this technology to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of this application and the above-mentioned accompanying drawings are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances for the embodiments of this application described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0037] In this application, the orientation or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. are based on the orientation or positional relationships shown in the drawings. These terms are mainly used to better describe this application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0038] Moreover, in addition to being able to represent orientation or positional relationships, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0039] In addition, the meaning of the term "plurality" should be two or more.

[0040] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will detail this application with reference to the drawings and in combination with the embodiments.

[0041] Embodiment 1:

[0042] A method for oxidizing isobutane, comprising the following steps:

[0043] S1. Carrier gas configuration: uniformly mixing a gas stream rich in isobutane and a gas stream rich in nitrogen in proportion to form a first carrier gas;

[0044] S2. Reaction carrier gas configuration: uniformly mixing oxygen and the first carrier gas in proportion to form a second carrier gas, wherein the oxygen concentration is 1-10 vol%;

[0045] S3. Oxidation reaction: introducing the second carrier gas into the bottom of the oxidation reactor to react with the liquid-phase isobutane in the oxidation reactor to generate tert-butyl hydroperoxide, adjusting the nitrogen ratio in the first carrier gas to control the reaction temperature of the oxidation reactor, and adjusting the oxygen ratio in the second carrier gas to control the oxidation rate and the tail oxygen concentration.

[0046] In the gas stream rich in nitrogen in step S1, the nitrogen concentration > 80 vol%, and the oxygen concentration < 1 vol%; in the gas stream rich in isobutane, the isobutane concentration > 70 vol%. The content of nitrogen in the first carrier gas is 10-95 vol%. In step S3, the temperature of the oxidation reactor is maintained at 120-150 °C, the reaction pressure is 2.8-4.5 MPa, and the oxidation reaction zone is provided with 1-10 stages, and the reaction temperature decreases step by step.

[0047] Preferably, it further includes step S4, tail gas and condensate circulation. The tail gas flowing out from the top of the oxidation reactor is successively condensed and compressed. The gaseous tail gas is configured as the first carrier gas as a nitrogen-rich gas stream. A part of the condensed liquid-phase tail gas is vaporized and configured as the first carrier gas as an isobutane-rich gas stream. Another part is heated and then enters the oxidation reactor as a reaction raw material.

[0048] Preferably, the tail gas flowing out from the top of the oxidation reactor is subjected to step-by-step condensation, and the number of condensation stages is 1 to 5. The high-temperature condensate above 110°C condensed is returned to the oxidation reactor as a reaction raw material.

[0049] Preferably, the tail gas flowing out from the top of the oxidation reactor is heat-exchanged with liquid-phase isobutane and then condensed and compressed.

[0050] Principle description:

[0051] For the liquid-phase oxidation reaction of isobutane, oxygen enters the reactor and reacts with liquid-phase isobutane to generate tert-butyl hydroperoxide, and reaction heat is released. Introducing nitrogen into the reactor will cause partial vaporization and endothermic absorption of liquid-phase isobutane, taking away the reaction heat. This is the basis for controlling the temperature of the heterogeneous alkane liquid-phase oxidation reaction. However, in fact, it is difficult to achieve the normal operation of the isobutane liquid-phase oxidation reaction by using the conventional two-component gas stream scheme of oxygen + nitrogen. Since the boiling point of isobutane is low, -10.5°C under normal pressure, the equilibrium partial pressure of nitrogen (N2) is relatively high. For a material system with isobutane / tert-butanol = 0.7 / 0.3 wt / wt, after reaching the equilibrium state, adding 1 mol of nitrogen to the liquid phase will cause ~4 mol of liquid-phase material to vaporize and take away 44.4 kJ of heat at 3.7 MPa and 135°C. To balance this part of the heat taken away, it is necessary to make up for it with the reaction heat of isobutane oxidation. The unit reaction heat of the reaction of isobutane with oxygen to produce tert-butyl hydroperoxide is 108.4 kJ / mol. To balance the heat taken away in the oxidation reaction, 0.41 mol of oxygen needs to participate in the oxidation reaction in the reactor. Calculated at an oxygen utilization rate of 95%, the oxygen content in the oxygen-containing gas introduced into the oxidation reactor is 30%. This poses a considerable safety risk for the liquid-phase oxidation reaction of isobutane, especially when the oxygen utilization rate is low, which will directly cause the gas phase in the oxidation reactor to fall into the explosion range. At the same time, the control of the two-component oxygen-containing gas is also very difficult. When the temperature of the isobutane oxidation reaction is slightly low and the oxygen utilization rate is low, the oxygen concentration in the gas phase in the reactor will increase. To control the continuous increase of the oxygen concentration, it is necessary to reduce the injection amount of oxygen or increase the injection amount of nitrogen. However, as analyzed above, both of these methods will cause the reaction temperature to further decrease and the tail oxygen to further increase, forming a vicious cycle of continuous decrease in the reaction temperature and unable to maintain normal operation.

[0052] In this method, isobutane in the gas phase is introduced into the oxygen-carrying gas stream. The gas stream entering the reactor mainly has three components, namely oxygen, nitrogen, and isobutane. Since the isobutane vapor is the same as the liquid-phase material in the reactor, the circulation of the isobutane vapor will not cause the liquid-phase material to absorb heat due to vaporization, so the reaction temperature can be ensured. At the same time, the regulation of the tail oxygen concentration does not require the addition of nitrogen, but can directly adjust the oxygen concentration in the inlet gas, which completely avoids the heat balance problem during the circulation of the oxygen and nitrogen components. In the gas stream entering the reactor, both the oxygen content and the nitrogen content can be flexibly adjusted. Adjusting the oxygen content can control the oxidation rate and the tail oxygen concentration, and adjusting the nitrogen content can control the reaction temperature, taking into account both the safety and operability of the oxidation reaction.

[0053] The following takes the isobutane oxidation reaction process with an oxygen consumption of 10 t / h as an example.

[0054] Prepare the carrier gas: Nitrogen and the gas rich in isobutane are mixed to prepare a carrier gas with a flow rate of 5937 kmol / h.

[0055] Prepare the oxygen-containing gas: Inject 312.5 kmol / h (10 t / h) of oxygen into the carrier gas according to the ratio to make an oxygen-containing gas with an oxygen content of 5% mol / mol.

[0056] Send the oxygen-containing gas to the bottom of the reactor. 300 t / h of liquid-phase isobutane (isobutane / tert-butanol mass ratio = 70:30) enters the bubble reactor. Oxygen reacts with the liquid-phase isobutane in the reactor to generate tert-butyl hydroperoxide and tert-butanol, and heat is released. The reaction heat is removed by the vaporization of isobutane, and 45.8 t / h of the reaction liquid-phase flows out of the reactor, containing about 8.5 wt% of tert-butyl hydroperoxide.

[0057] This embodiment can conveniently adjust the reaction temperature while ensuring the oxidation efficiency and safety.

[0058] When the tail gas concentration is high and the oxygen reaction is incomplete, the reaction temperature can be adjusted by increasing the reaction temperature: when the gas rich in isobutane:nitrogen = 1:1.24 mol / mol and the nitrogen content in the carrier gas is 56 vol%, the reaction temperature of the reactor can be controlled at 146 °C; when the tail oxygen concentration is low and it is desired to increase the selectivity of tert-butyl hydroperoxide, it can be operated at a lower reaction temperature: reduce the flow rate of the gas rich in isobutane, increase the nitrogen flow rate, and adjust the nitrogen content in the carrier gas to 66 vol%. The total flow rate of the carrier gas and the oxygen feeding flow rate remain unchanged, and the reaction temperature of the reactor can be reduced to 142 °C. At this time, more isobutane will vaporize to lower the reaction temperature, so the content of tert-butyl hydroperoxide in the liquid phase flowing out of the reactor will also increase, to ~9.7%; if it is desired to further lower the operating temperature of the reactor, the oxygen flow rate can be further increased while the total flow rate of the carrier gas and the oxygen feeding flow rate always remain unchanged: adjust the flow rate ratio of nitrogen to the gas rich in isobutane so that the nitrogen content in the carrier gas is 90 vol%, and the reaction temperature of the reactor can be reduced to 132 °C. Due to the inflow of more nitrogen, more isobutane vaporizes and heat is removed. At this time, the content of tert-butyl hydroperoxide in the liquid flowing out of the reactor >13%.

[0059] This example illustrates the convenience of adjusting the operating temperature of the reactor according to the present invention. During the adjustment process, the oxygen content in the gas phase at any position in the reactor is always lower than the safety limit. While improving the operability of the oxidation reactor, the safety of the oxidation reaction operation is also ensured.

[0060] Example 2:

[0061] As Figure 1 shown, fresh liquid-phase isobutane feed S9 (isobutane content ~70 wt%, and the rest are mainly tert-butanol, methanol and acetone) at 230 t / h is mixed with the oxidation condensate S8 and sent to the oxidation feed heating vaporizer 108 to be heated to 150 °C. The vaporized isobutane gas is used for the preparation of the reactor carrier gas, and the heated liquid phase S1 enters the oxidation reactor group.

[0062] The oxidation reactor group can adopt multiple oxidation reactors connected in series in sequence. The number of oxidation reactors can be set from 1 to 10, preferably 2 to 6. Multiple oxidation reactors can be arranged side by side, or arranged vertically, or arranged in a horizontal multi-compartment type. In addition, in order to improve the conveying efficiency, a liquid conveying pump is arranged between each oxidation reactor for the conveying of the oxidation liquid.

[0063] There are 3 oxidation reactors (101, 102, 103) in the oxidation reaction area. The liquid feed S1 enters the first oxidation reactor 101 and reacts with oxygen in the reactor. The oxidation liquid containing approximately 6% tert-butyl hydroperoxide overflows by gravity into the second oxidation reactor 102 for further reaction. The oxidation liquid after the reaction contains approximately 12% tert-butyl hydroperoxide and then overflows by gravity into the third oxidation reactor 103 for further reaction. After the reaction is completed, the flow rate of the oxidation liquid flowing out of the third oxidation reactor 103 is 264 t / h, and the content of tert-butyl hydroperoxide is approximately 20%.

[0064] The oxygen-containing gases S2a / b / c entering the three oxidation reactors are in parallel, and the oxygen content in the gas phase entering each stage of the reactor is the same, approximately 10 t / h. The oxygen content in the oxygen-containing gas after oxygen distribution is controlled at 5 - 6% vol, which is lower than the highest safety limit of the oxygen content in the gas phase, ensuring the safety of the oxidation reaction. In order to ensure the uniform distribution of oxygen in the carrier gas, static mixers 112a / b / c are set during oxygen distribution. In order to improve the selectivity of tert-butyl hydroperoxide and reduce the proportion of its decomposition into tert-butanol, the reaction temperatures of the three reactors decrease gradually, being 146 °C, 142 °C, and 137 °C respectively. According to the method of the present invention, by adjusting the ratio of nitrogen and isobutane-containing gas in the carrier gas S7a / b / c entering each reactor, the temperature in each reactor can be controlled. In this embodiment, the nitrogen contents in the carrier gases entering the three oxidation reactors (101, 102, 103) are 25 vol%, 49 vol%, and 66 vol% respectively.

[0065] The tail gases flowing out of the three oxidation reactors (101, 102, 103) are combined into one stream S3 (temperature 141 °C, pressure 3.66 MPa), enter the oxidation tail gas condenser 104 and are cooled to 55 °C, and then enter the tail gas separation tank 105 for liquid separation to remove high-boiling components such as isobutane, tert-butanol, and tert-butyl hydroperoxide in the oxidation tail gas. The non-condensable gas S6 enters the oxidation tail gas recycle compressor 106 for pressurization. The pressurized recycled nitrogen is divided into 3 streams, mixed with isobutane gas from the oxidation feed heating vaporizer 108 according to the required ratio to form recycled carrier gases S7a / b / c, and then 5 - 6% vol of oxygen is proportionally added and they respectively enter the three reactors (101, 102, 103) for further reaction. The liquid phase S8 isobutane flowing out of the tail gas separation tank 105 is pressurized by the pump 107 and then returns to the oxidation feed heating vaporizer 108 for circulation. In addition, the oxidation feed heating vaporizer is split into two devices, an isobutane vaporizer and an oxidation feed heater, which are respectively used for vaporization and heating.

[0066] Example 3:

[0067] As Figure 2As shown, compared with Embodiment 2, in this embodiment, the heat exchange between the oxidation tail gas and the isobutane feed is increased, reducing the energy consumption of the entire oxidation operation.

[0068] The temperature of the oxidation tail gas S3 is 141 °C and contains condensable components such as ~80% isobutane, tert-butanol, and tert-butyl hydroperoxide. The oxidation tail gas S3 is heat-exchanged with the liquid-phase feed S11 of the oxidation. The liquid-phase material S11 is heated to 134 °C and then enters the oxidation feed heating vaporizer 108. The content of tert-butyl hydroperoxide in the liquid-phase material condensed from S3 is relatively high and is directly returned to the first oxidation reactor 101. A heat exchanger is added in front of the oxidation tail gas condenser to recover heat. The number of stages of the added heat exchanger is preferably 1 to 5, and the condensate collected at each stage is preferably sent to the oxidation reactor by adding a transfer pump.

[0069] Compared with Embodiment 2, this embodiment can consume ~61 MW less heat.

[0070] In addition, a high-temperature condensate tank 110 and a high-temperature condensate pump 111 are added. The heat-exchanged tail gas forms high-temperature condensate in the high-temperature condensate tank 110, and this high-temperature condensate is preferably sent to the oxidation reactor through the high-temperature condensate pump 111 to continue the oxidation reaction.

[0071] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An isobutane oxidation method, characterized in that: The following steps are involved: S1, carrier gas configuration, the isobutane-rich gas flow and the nitrogen-rich gas flow are uniformly mixed in proportion to form a first carrier gas, the nitrogen concentration in the nitrogen-rich gas flow is >80vol%, and the oxygen concentration is <1vol%; the isobutane concentration in the isobutane-rich gas flow is >70vol%, and the nitrogen content in the first carrier gas is 10-95vol%; S2, reaction carrier gas configuration, oxygen and the first carrier gas are uniformly mixed in proportion to form a second carrier gas, wherein the oxygen concentration is 1-10 vol%; S3, oxidation reaction, the second carrier gas is introduced into the bottom of the oxidation reactor to react with the liquid isobutane in the oxidation reactor to generate tert-butyl hydroperoxide, the nitrogen ratio in the first carrier gas is adjusted to control the reaction temperature of the oxidation reactor, and the oxygen ratio in the second carrier gas is adjusted to control the oxidation rate and tail oxygen concentration.

2. The isobutane oxidation method according to claim 1, characterized in that: It also includes S4, tail gas and condensate circulation. The tail gas flowing out from the top of the oxidation reactor is condensed and compressed in sequence, and the gaseous tail gas is used as a nitrogen-rich gas flow to configure the first carrier gas. A part of the condensed liquid tail gas is vaporized and used as an isobutane-rich gas flow to configure the first carrier gas, and the other part is heated and then enters the oxidation reactor as a reaction raw material.

3. A method for oxidation of isobutane as claimed in claim 2, characterized in that: The tail gas flowing out of the top of the oxidation reactor is condensed step by step, and the condensation stages are 1 to 5. The condensed high-temperature condensate greater than 110°C is returned to the oxidation reactor as a reaction raw material.

4. The isobutane oxidation method according to claim 2, characterized in that: The tail gas flowing out from the top of the oxidation reactor is condensed and compressed after heat exchange with liquid isobutane.

5. The isobutane oxidation method according to claim 1, characterized in that: In step S3, the temperature of the oxidation reactor is maintained at 120-150°C, the reaction pressure is 2.8-4.5MPa, the oxidation reaction zones are set at levels 1-10, and the reaction temperature is reduced step by step.

6. An isobutane oxidation system, characterized in that: The invention comprises an oxidation reactor group, an oxidation tail gas condenser connected to the tail gas outlet of the oxidation reactor group, an oxidation tail gas separator connected to the oxidation tail gas condenser, an oxidation tail gas circulation compressor connected to the gas phase outlet of the oxidation tail gas separator, a tail gas condensate booster pump connected to the liquid phase outlet of the oxidation tail gas separator, and an oxidation feed heating vaporizer connected to the tail gas condensate booster pump, wherein the material inlet of liquid isobutane is connected to the oxidation feed heating vaporizer, the gas flowing out of the gas phase outlet of the oxidation feed heating vaporizer is mixed with the gas flowing out of the oxidation tail gas circulation compressor in proportion to form a first carrier gas, and further comprises a static mixer and an oxygen supply device, the oxygen generated by the oxygen supply device is mixed with the first carrier gas in the static mixer to form a second carrier gas, the second carrier gas is connected to the oxidation reactor group, and the liquid phase outlet of the oxidation feed heating vaporizer is connected to the oxidation reactor group.

7. An isobutane oxidation system as claimed in claim 6, characterized in that: It also includes an oxidation tail gas heat exchanger arranged between the oxidation reactor group and the oxidation tail gas condenser. The tail gas discharged from the oxidation reactor group is heat exchanged with the liquid isobutane material and the tail gas condensate discharged from the tail gas condensate increasing pump through the oxidation tail gas heat exchanger.

8. An isobutane oxidation system as claimed in claim 7, characterized in that: It also includes a high-temperature condensate tank arranged between the oxidation tail gas heat exchanger and the oxidation tail gas condenser, the gas phase outlet of the high-temperature condensate tank is connected to the oxidation tail gas condenser, and the liquid phase outlet of the high-temperature condensate tank is connected to the oxidation reactor group through a high-temperature condensate pump.

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