Isobutane oxidation method and system

Abstract

The invention discloses an isobutane oxidation method and system. The method comprises the following steps: 1) mixing gas flow rich in isobutane and gas flow rich in nitrogen to prepare first carrier gas for later use; 2) uniformly mixing oxygen with a first carrier gas in proportion to obtain an oxygen-containing gas flow with the oxygen concentration of 1-10vol%; 3) feeding the oxygen-containing gas flow into the bottom of the reactor to react with liquid-phase iso-butane entering the reactor to generate tert-butyl hydroperoxide.The method ensures operability and safety of iso-butane oxidation reaction by setting two-component carrier gas of iso-butane and nitrogen in different proportions and introducing oxygen with safe concentration into the reactor through preparation, and is suitable for industrial production. Moreover, nitrogen circulation in the carrier gas is separately arranged, only one compressor needs to be arranged for a system with multiple reactors, meanwhile, liquid-phase materials of the multiple oxidation reactors overflow to the next stage by means of gravity, an inter-stage conveying pump is omitted, and equipment investment is reduced.

Description

Technical Field

[0001] The invention relates to the field of chemical engineering, and in particular to an isobutane oxidation method for improving the operability and safety of a liquid phase oxidation reaction. The method 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 oxygen of a safe concentration into a reactor. Background Art

[0002] Tert-Butyl Hydroperoxide (TBHP) is an organic peroxide widely used as an oxidant and initiator of free radical reactions. It is also a common oxygen source for the production of propylene oxide by propylene co-oxidation. 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 method of producing tert-butyl hydroperoxide by liquid-phase oxidation of isobutane is based on the process of preparing tert-butyl hydroperoxide and tert-butyl alcohol by liquid-phase non-catalytic oxidation of isobutane disclosed in patents US2845461 and US3478108. American companies ARCO and Texaco also disclosed in patents US5243084 and US5399777 a method of preparing tert-butyl alcohol and tert-butyl hydroperoxide by non-catalytic liquid-phase oxidation of isobutane with molecular oxygen. The typical reaction conditions of liquid-phase oxidation of isobutane are reaction temperature of 100-150°C and reaction pressure of 2.0-4.8 MPa. Liquid-phase isobutane is directly oxidized with molecular oxygen for 2-5 hours, and the conversion rate of isobutane is 36-46%. The selectivity of TBHP and TBA is 48.0-53.4% ​​and 40.2-47.0%, respectively.

[0004] In addition to the oxidation method under isobutane liquid phase conditions, the European company Shell's patent US4404406 discloses a method for producing tert-butyl hydroperoxide under supercritical conditions. This method operates under supercritical conditions, 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 >4.8MPag, which can significantly improve the production efficiency of TBHP per unit time and per unit reactor volume.

[0005] There are also some patents disclosed in China for improving the isobutane oxidation method. Sinopec's patent CN201110113828.4 uses ozone as an oxidant, does not require a catalyst, simplifies the isobutane oxidation process, improves the isobutane conversion rate, reduces costs, and is suitable for industrialization. There are also many patents that use catalysts to improve the isobutane conversion rate and tert-butyl hydroperoxide selectivity, such as Yuxin Chemical's patent CN201710467464.7, which uses NHPI catalysts and β-cyclodextrin modifiers to improve conversion and selectivity, and is environmentally friendly. Sun Yat-sen University Huizhou Research Institute's patent CN201410449806.9 uses metal porphyrin compound catalysts, mild reaction conditions, and high selectivity.

[0006] In summary, currently in the field of isobutane oxidation to produce tert-butyl hydroperoxide and tert-butyl alcohol, most of the research focuses on optimizing process conditions, improving catalysts, and increasing production efficiency. Some work has also been conducted on improving the reactor and process safety of the reaction of liquid isobutane with molecular oxygen.

[0007] In the process flow of preparing TBHP by liquid-phase oxidation of isobutane disclosed in Arco's patent US5149885, a spherical reactor is used, the reaction temperature is 137°C, and the liquid phase circulation heat removal method is used. Oxygen is mixed with the liquid phase circulating material and then enters the reactor. This process is not conducive to the liquid level control of the reactor, and it is very easy to cause the liquid level to be full or lower than the circulation production line; in addition, the circulating material is very easy to cause cavitation after being transported by the circulating pump; in addition, the production of large spherical reactors is also difficult.

[0008] In the process of preparing TBHP by liquid-phase oxidation of isobutane disclosed in Texco's patent US5243083, an internal circulation tower reactor is used. Oxygen is mixed with gas-phase circulating materials and 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, liquid materials and fresh isobutane flow downward from the outer ring of the reactor to form a thermal siphon cycle. This process has high requirements for equipment. Liquid isobutane and oxygen are directly mixed in the reactor, which is very easy to enter the explosion limit range.

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

[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, and the condensation stages are 1 to 5. The condensed high-temperature condensate with a temperature greater than 110° C. is returned to the oxidation reactor as a reaction raw material.

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

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

[0021] Optionally, the nitrogen content 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 zones are arranged in 1-10 stages, and the reaction temperature is reduced step by step.

[0023] In order to achieve the above-mentioned purpose, in a second aspect, a preparation system of an isobutane oxidation method 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 phase 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.

[0024] Optionally, it also includes an oxidation tail gas heat exchanger arranged between the oxidation reactor group and the oxidation tail gas condenser, and 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.

[0025] Optionally, 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.

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

[0027] Gaseous isobutane is introduced into the oxygen-carrying gas flow, and the gas flow 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 adjustment of the tail oxygen concentration does not require the addition of nitrogen, but can directly adjust the oxygen concentration in the intake air, which completely avoids the heat balance problem when the oxygen and nitrogen components are circulated. In the gas flow entering the reactor, the oxygen content and nitrogen content can be flexibly adjusted. Adjusting the oxygen content can control the oxidation rate and tail oxygen concentration, and adjusting the nitrogen content can control the reaction temperature, while taking into account the safety and operability of the oxidation reaction.

[0028] The oxygen of the present invention is prepared in advance with the carrier gas outside the reactor, and the oxygen content in the prepared gas flow is strictly controlled, which is determined by the explosion upper limit of the material (isobutane / tert-butyl alcohol and other organic matter) in the reactor, but the operation point usually leaves a suitable safety range. The present invention requires that the oxygen content in the gas flow entering the reactor is less than or equal to 8%, which is based on the consideration of intrinsic safety. Even if a misoperation occurs (such as the reaction temperature is too low, 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 is usually more than one. When multiple reactors are used, the operating temperature and TBHP concentration in the reactor are different, which causes the composition of the gas phase flowing out of each reactor to be different. If they are directly mixed and enter the same compressor for supercharging cycle, the intake components of multiple reactors will be the same, and the operating temperature and component changes of multiple reactors cannot be taken into account. Therefore, the traditional process is equipped with a corresponding compressor for each reactor, and the equipment investment cost is large. The carrier gas of the present invention is prepared by using a nitrogen-rich gas flow and an isobutane-rich gas flow according to the operating temperature of each reactor. Even if the tail gas components of multiple reactors are different, they will be divided into a nitrogen-rich gas flow and an isobutane-rich liquid phase after mixing and condensing. A single tail gas compressor can compress the nitrogen-rich gas flow, and then according to the needs of each reactor, the nitrogen-rich gas flow and the isobutane-rich gas flow are mixed in proportion to prepare the carrier gas required by each reactor. Therefore, the present invention can significantly reduce the compressor investment cost when multiple reactors are used.

[0030] Liquid materials from multiple oxidation reactors overflow to the next stage by gravity, eliminating the need for inter-stage transfer pumps and reducing equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The schematic embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

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

[0033] Figure 2 The schematic diagram of the reaction flow diagram shows a preferred energy-saving scheme of the present invention.

[0034] Among them: 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 circulation 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, the static mixer; S1~S11 logistics numbers. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

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

[0038] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency 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 term "plurality" shall mean two or more.

[0040] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0041] Embodiment 1:

[0042] An isobutane oxidation method comprises the following steps:

[0043] 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;

[0044] 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%;

[0045] 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.

[0046] In the nitrogen-rich gas flow in step S1, the nitrogen concentration is >80 vol%, and the oxygen concentration is <1 vol%; in the isobutane-rich gas flow, the isobutane concentration is >70 vol%, and the nitrogen content 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, the oxidation reaction zone is set at 1-10 levels, and the reaction temperature is reduced step by step.

[0047] Preferably, step S4, tail gas and condensate circulation is also included, the tail gas flowing out from the top of the oxidation reactor is condensed and compressed in sequence, 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 enters the oxidation reactor as a reaction raw material.

[0048] Preferably, the tail gas flowing out from the top of the oxidation reactor is condensed step by step, and the condensation stages are 1 to 5. The condensed high-temperature condensate with a temperature greater than 110° C. 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 condensed and compressed after heat exchange with liquid isobutane.

[0050] Principle description:

[0051] For the liquid phase oxidation reaction of isobutane, oxygen enters the reactor and reacts with liquid isobutane to generate tert-butyl hydroperoxide and releases reaction heat; while nitrogen introduced into the reactor will cause the vaporization of part of the liquid phase isobutane to absorb heat and take away the reaction heat, which is the basis for controlling the temperature of the liquid phase oxidation reaction of isobutane. However, in fact, it is difficult to achieve normal operation of the liquid phase oxidation reaction of isobutane using the conventional two-component gas flow scheme of oxygen + nitrogen. Since the boiling point of isobutane is low, which is -10.5℃ under normal pressure, the equilibrium partial pressure of nitrogen (N2) is relatively high. For the material system of isobutane / tert-butyl alcohol = 0.7 / 0.3wt / wt, after reaching equilibrium, adding 1 mol of nitrogen to the liquid phase will cause ~4 mol of liquid phase material to vaporize at 3.7MPa and 135℃, and bring out 44.4kJ of heat. In order to balance this part of the heat brought out, it is necessary to rely on the oxidation reaction heat of isobutane to make up for it. The unit heat of reaction of isobutane and oxygen to produce tert-butyl hydroperoxide is 108.4 kJ / mol. In order to balance the heat taken away in the oxidation reaction, 0.41 mol of oxygen is required in the reactor to participate in the oxidation reaction. Calculated based on the utilization rate of oxygen of 95%, the oxygen content in the oxygen-containing gas introduced into the oxidation reactor is 30%. This is a considerable safety risk for the liquid phase oxidation reaction of isobutane, especially when the oxygen utilization rate is low, it 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. In order to control the oxygen concentration to continue to increase, it is necessary to reduce the injection amount of oxygen or increase the injection amount of nitrogen. However, from the above analysis, it can be seen that both methods will cause the reaction temperature to further decrease and the tail oxygen to further increase, which forms a vicious cycle of continuous decrease in the reaction temperature and cannot maintain normal operation.

[0052] In the present method, gaseous isobutane is introduced into the oxygen-carrying gas flow, and the gas flow 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 does not cause the vaporization heat absorption of the liquid phase material, so the reaction temperature can be guaranteed; at the same time, the adjustment of the tail oxygen concentration does not require the addition of nitrogen, but the oxygen concentration in the intake air can be directly adjusted, which completely avoids the heat balance problem when the two components of oxygen and nitrogen are circulated. In the gas flow entering the reactor, the oxygen content and 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, while taking into account the safety and operability of the oxidation reaction.

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

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

[0055] Preparation of oxygen-containing gas: Inject 312.5 kmol / h (10 t / h) of oxygen into the carrier gas in proportion to prepare oxygen-containing gas with an oxygen content of 5% mol / mol.

[0056] The oxygen-containing gas is fed into the bottom of the reactor, and 300 t / h of liquid isobutane (mass ratio of isobutane to tert-butyl alcohol = 70:30) enters the bubbling reactor. Oxygen and liquid isobutane undergo oxidation reaction in the reactor to generate tert-butyl hydroperoxide and tert-butyl alcohol, and release heat. The reaction heat is removed by vaporization of isobutane, and 45.8 t / h of the liquid phase after the reaction flows out of the reactor, which contains tert-butyl hydroperoxide ~8.5wt%.

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

[0058] When the tail gas concentration is high and the oxygen reaction is not complete, the reaction temperature can be increased to adjust: when the isobutane-rich gas: nitrogen = 1: 1.24 mol / mol, 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 hoped to increase the selectivity of tert-butyl hydroperoxide, it can be operated at a lower reaction temperature: reduce the flow of isobutane-rich gas, increase the nitrogen flow, adjust the nitrogen content in the carrier gas to 66 vol%, and keep the total carrier gas flow and oxygen flow unchanged. The reaction temperature of the reactor can be reduced to 142 ° C. When the reaction temperature is reduced, more isobutane will be vaporized to reduce the reaction temperature, so the tert-butyl hydroperoxide content in the liquid phase flowing out of the reactor will also increase, ~9.7%; if it is desired to further reduce the operating temperature of the reactor, the oxygen flow rate can be further increased, while the total carrier gas flow rate and the oxygen flow rate remain unchanged: adjust the flow ratio of nitrogen to isobutane-rich gas 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. As more nitrogen flows in, more isobutane is vaporized and heat is removed. At this time, the tert-butyl hydroperoxide content in the liquid flowing out of the reactor is >13%.

[0059] This embodiment illustrates the convenience of the present invention in regulating the reactor operating temperature, and during the regulation process, the oxygen content in the gas phase at any position in the reactor is always below the safety limit, which improves the operability of the oxidation reactor while ensuring the safety of the oxidation reaction operation.

[0060] Embodiment 2:

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

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

[0063] The oxidation reaction area is provided with three oxidation reactors (101, 102, 103). After the liquid feed S1 enters the first oxidation reactor 101, it reacts with oxygen in the reactor. The generated oxidation liquid containing about 6% tert-butyl hydroperoxide overflows by gravity into the second oxidation reactor 102 to continue the reaction. The oxidation liquid after the reaction contains about 12% tert-butyl hydroperoxide, and then overflows by gravity into the third oxidation reactor 103 to continue the reaction. After the reaction, the flow rate of the oxidation liquid flowing out of the third oxidation reactor 103 is 264 t / h, of which the tert-butyl hydroperoxide content is about 20%.

[0064] The oxygen-containing gas S2a / b / c entering the three oxidation reactors is parallel, and the oxygen content in the gas phase entering the reactors at each level is the same, about 10t / h. The oxygen content in the oxygen-containing gas after oxygen distribution is controlled at 5-6%vol, which is lower than the maximum 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, a static mixer 112a / b / c is set during oxygen distribution. In order to improve the selectivity of tert-butyl hydroperoxide and reduce the proportion of its decomposition into tert-butyl alcohol, the reaction temperature of the three reactors is gradually reduced, which is 146°C, 142°C, and 137°C respectively. According to the method of the present invention, the ratio of nitrogen and isobutane-containing gas in the carrier gas S7a / b / c entering each reactor can be adjusted to control the temperature in each reactor. In this embodiment, the nitrogen content in the carrier gas entering the three oxidation reactors (101, 102, 103) is 25vol%, 49vol%, and 66vol% respectively.

[0065] The tail gas flowing out from the three oxidation reactors (101, 102, 103) merges into one stream S3 (temperature 141°C, pressure 3.66MPa), enters the oxidation tail gas condenser 104 to be cooled to 55°C, and then enters the tail gas separator 105 for separation to remove high boiling point components such as isobutane, tert-butyl alcohol, and tert-butyl hydroperoxide in the oxidation tail gas. The non-condensable gas S6 enters the oxidation tail gas circulation compressor 106 for pressurization. The pressurized circulating nitrogen is divided into three streams and mixed with the isobutane gas from the oxidation feed heating vaporizer 108 according to the required ratio to prepare the circulating carrier gas S7a / b / c. After 5-6%vol of oxygen is added in proportion, it enters the three reactors (101, 102, 103) respectively to continue the reaction. The liquid phase S8 isobutane flowing out of the tail gas separator 105 is pressurized by the pump 107 and then returned 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 used for vaporization and heating respectively.

[0066] Embodiment three:

[0067] like Figure 2As shown, compared with Example 2, this embodiment increases the heat exchange between the oxidation tail gas and the isobutane feed, thereby reducing the energy consumption of the entire oxidation operation.

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

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

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

[0071] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. 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, mixing an isobutane-rich gas flow and a nitrogen-rich gas flow in a uniform proportion to form a first carrier gas; 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%; 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 the nitrogen-rich gas flow in step S1, the nitrogen concentration is >80 vol%, and the oxygen concentration is <1 vol%. In the isobutane-rich gas flow, the isobutane concentration is >70 vol%.

6. The isobutane oxidation method according to claim 1, characterized in that: The content of nitrogen in the first carrier gas is 10-95 vol%.

7. 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 2.8-4.5 MPa, the oxidation reaction zones are arranged in 1-10 levels, and the reaction temperature is reduced step by step.

8. A preparation system for an isobutane oxidation method, 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.

9. The preparation system of an isobutane oxidation method according to claim 1, 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.

10. The preparation method of an isobutane oxidation method according to claim 9, 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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