Method for generating 2-methyl-1-butene through isomerization of 2-methyl-2-butene

Abstract

The invention belongs to the technical field of fine chemical intermediates, and particularly relates to a method for generating 2-methyl-1-butene through isomerization of 2-methyl-2-butene. The method comprises the following steps: (1) 2-methyl-2-butene enters a fixed bed reactor and is subjected to an isomerization reaction under the action of an isomerization catalyst; the pressure of the fixed bed reactor is 0.1-0.5 Mpa, the temperature is 200-250 DEG C, and the mass space velocity is 0.5-2.0 h <-1 >; (2) feeding the reacted material into a rectifying tower, rectifying and separating to obtain 2-methyl-1-butene at the top of the rectifying tower, and returning 2-methyl-2-butene obtained at the bottom of the rectifying tower to the inlet of the fixed bed reactor to continue the reaction; the isomerization catalyst comprises active components and a carrier, wherein the active components comprise NiO and MgO. The catalyst provided by the invention has the advantages of high catalyst activity, low reaction temperature, high reaction selectivity, long catalyst life and the like, and meets market requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical intermediates, and particularly relates to a method for isomerizing 2-methyl-2-butene to generate 2-methyl-1-butene. Background Art

[0002] Tert-amylene is a colorless, volatile liquid with an unpleasant odor. It is usually a mixture of 2-methyl-1-butene and 2-methyl-2-butene. It is mainly used to produce isoprene, pinacolone and tert-amyl alcohol. It can also be used as an intermediate for synthetic rubber, resin and organic synthesis. Its derivatives, 4-tert-amylphenol and 2,4-di-tert-amylphenol, can be used as photographic photosensitive materials and surfactants.

[0003] 2-Methyl-1-butene is a colorless, volatile liquid with an unpleasant odor and a boiling point of 31.05°C. Due to its low reaction activation energy, 2-methyl-1-butene has significantly higher reactivity and reaction rate than 2-methyl-2-butene. For example, it reacts with water to form tert-amyl alcohol and with synthesis gas to form the corresponding aldehyde. It is an important intermediate in organic synthesis.

[0004] Tert-amylene is currently mainly produced by the decomposition of tert-amyl methyl ether, in which the ratio of 2-methyl-1-butene to 2-methyl-2-butene is about 1:4, and the output of 2-methyl-1-butene is significantly less than that of 2-methyl-2-butene. In addition to the decomposition of tert-amyl methyl ether, there is no other reliable method to obtain 2-methyl-1-butene.

[0005] There are few reports on the isomerization of 2-methyl-2-butene to 2-methyl-1-butene. Currently, the technical routes for the isomerization of 2-butene double bonds to produce 1-butene reported publicly at home and abroad are mainly as follows: The technology used by Dow Chemical is a process production route that combines the production route of 2-butene double bond isomerization to 1-butene with a 1-butene and 2-butene fractionation system. The isomerization and fractionation are combined to increase the production of 1-butene. The process is carried out using a metal oxide catalyst at high temperature and in the absence of hydrogen. The single-pass equilibrium conversion rate of 2-butene isomerization to 1-butene reaches 20%-30%. The product yield of 1-butene in Dow Chemical's process production system has increased by more than 65%.

[0006] Lummus uses a basic metal oxide catalyst, capable of converting over 20% of 2-butene to 1-butene at reaction temperatures of 340-500°C and pressures of 0.1-2.7 MPa. The feed undergoes dehydrogenation, dehydration, and heat exchange before entering the isomerization reactor, where the double bond of 2-butene isomerizes to 1-butene. The catalyst then passes through a separation tower, significantly increasing the yield of 1-butene.

[0007] A technology for increasing 1-butene production through olefin isomerization, jointly developed by Sinopec Shanghai Research Institute of Petrochemical Engineering and Zhongyuan Petrochemical Company, has successfully been put into operation at a 30,000-ton / year industrial plant. This technology utilizes a large axial-flow fixed-bed reactor and a proprietary solid aluminosilicate catalyst. The process involves a liquid C4 olefin mixture undergoing heat exchange with the catalytic product before vaporization. After heating to 300-350°C, the mixture enters the reactor. In the reactor, 2-butene undergoes double bond isomerization to 1-butene under the action of the solid acid catalyst. The product enters a stripping tower for separation, yielding a high-purity 1-butene product at the top. The bottoms of the tower are then recycled back to the reactor for further reaction. The 1-butene selectivity exceeds 95%, with a yield of 16%-21%. The catalyst regeneration cycle exceeds 1,800 hours, ensuring long-term stable operation. The 1-butene product quality meets the requirements of gas-phase polyethylene production, thereby increasing the added value of the C4 mixture.

[0008] The disadvantages of this process route are the high reaction temperature and the generation of numerous side reactions during the reaction process, primarily due to the low reactivity of the catalyst. In the process of preparing 1-butene from 2-butene, not only does double bond isomerization occur to generate 1-butene, but skeletal isomerization also occurs to generate isobutylene, cracking to generate ethylene and propane, polymerization to generate C5, and hydrogen transfer to generate other byproducts. This reaction system is not a single reaction, but rather a complex reaction system composed of multiple parallel reactions. The selection of a suitable catalyst is crucial; according to the requirements of the reaction system, a suitable catalyst should be prepared to reduce the generation of side reactions such as isomerization, cracking, and polymerization, thereby increasing the yield of 1-butene.

[0009] Chinese invention patent CN104549295B points out that alkaline earth metal oxides such as magnesium oxide and calcium oxide have excellent catalytic performance in the isomerization reaction of olefin double bonds. However, at higher reaction temperatures, the surface of such catalysts will gradually lose their reaction activity due to coking and other reasons. The technical solution adopted by this invention is as follows: an olefin isomerization catalyst, which includes the following components in parts by weight: a) 77-100 parts of magnesium oxide; b) 0.1-20 parts of calcium oxide; c) 0.01-2 parts of iron oxide; d) 0-1 part of nickel oxide. This catalyst is suitable for the method of isomerization of 1-butene to 2-butene, at a reaction temperature of 200-400°C, a reaction pressure of 1-4 MPa, and a 1-butene mass space velocity of 0.1-20 h -1Under the conditions of , 1-butene contacts the isomerization catalyst to react and produce 2-butene. By using Ca, Fe, and Ni as additives for the isomerization catalyst, the reaction activity of the isomerization catalyst can be effectively improved through the interaction between Ca, Fe, Ni and the main active component Mg. At the same time, the active components are evenly distributed on the surface of the molecular sieve support and are not easily covered by carbon deposits during the reaction, thereby effectively improving the life of the catalyst. The synergistic effect between the active components is significant. Only when the active components Ca, Fe, and Ni are all present can the catalyst have good disproportionation activity. When the active component Mn is added, the isomerization activity of the catalyst is significantly improved, and the stability can be increased by more than 10%. The catalyst in this patent uses MgO as the main component and other metals as additives for isomerization reactions. Due to the low reaction activity of MgO, the reaction temperature is high, which is not conducive to energy saving and consumption reduction, and is not conducive to improving the service life of the catalyst.

[0010] Chinese invention patent CN103028388B relates to a catalyst for olefin isomerization and its preparation method, primarily addressing the low specific surface area, lack of strong basic sites on the surface, and poor stability of such catalysts in the prior art. This invention utilizes an olefin double bond isomerization catalyst comprising the following components, calculated by weight: a. 80-99% of at least one oxide selected from alkaline earth metals; b. 0.0001-10% of at least one oxide selected from alkali metals; c. 0-8% of an oxide of at least one element selected from Groups IB-VIIB and VIII; and d. 0-20% of at least one selected from a neutral or slightly alkaline support. This technology addresses the low specific surface area, lack of strong basic sites on the surface, and poor stability of prior alkaline earth metal oxide catalysts in olefin double bond isomerization reactions. This invention provides a new olefin double bond isomerization catalyst with a large specific surface area, strong basic sites on the surface, and excellent stability. It also provides a method for preparing an olefin double bond isomerization catalyst that addresses one of the aforementioned technical issues.

[0011] Chinese invention patent CN1488722A provides a catalyst for the hydroisomerization of normal paraffins: nickel oxide content of 1.0-10% (m), nano-HBeta content of 50-90% (m), and the balance being alumina as a binder. This catalyst exhibits high isomerization activity and, due to the smooth diffusion of positive carbon ions within the catalyst pores, suppresses polymerization and coking, reducing carbon deposits on the catalyst.

[0012] Chinese invention patent CN1169760C relates to a method for isomerizing α-olefins to produce a mixture of linear internal olefins. The α-olefins are heated in the presence of pentasil zeolite, which contains an isomerization catalyst composed of 1%-10% (m) nickel monoxide. The reaction is carried out at 100-250°C. This catalyst is not suitable for isomerization reactions of linear internal olefins to α-olefins, such as the isomerization of 2-methyl-2-butene to 2-methyl-1-butene or the isomerization of 2-butene to 1-butene.

[0013] In addition, compared with butene-2, 2-methyl-2-butene has a methyl group in the double bond, which increases steric hindrance. Therefore, using the catalysts described in the above patents and literature, it is more difficult to combine 2-methyl-2-butene with the isomerization catalyst, and it is more difficult to convert 2-methyl-2-butene into 2-methyl-1-butene. Therefore, the reaction activity is low and it is not suitable for the isomerization of 2-methyl-2-butene to 2-methyl-1-butene.

[0014] In summary, the production of tert-amylene products in the current industry and literature generally adopts the process flow of C5 etherification-etherolysis-water washing with methanol-distillation-isomerization. The output of 2-methyl-2-butene is much higher than that of 2-methyl-1-butene. Since the reaction activation energy of 2-methyl-1-butene is lower, its reaction activity and reaction rate are much higher than those of 2-methyl-2-butene. The production capacity of 2-methyl-butene-1, which is urgently needed in the market, is insufficient to meet production needs. Therefore, it is urgent to develop a new process for producing 2-methyl-butene-1. Summary of the Invention

[0015] In order to solve the above technical problems, the present invention provides a method for isomerizing 2-methyl-2-butene to produce 2-methyl-1-butene, which has the advantages of high catalyst activity, low reaction temperature, high reaction selectivity, and long catalyst life, and meets market demand.

[0016] The method for isomerizing 2-methyl-2-butene to produce 2-methyl-1-butene according to the present invention comprises the following steps: (1) 2-Methyl-2-butene enters the fixed bed reactor and undergoes isomerization reaction under the action of the isomerization catalyst; the fixed bed reactor pressure is 0.1-0.5 MPa, the temperature is 200-250 ° C, and the mass space velocity of 2-methyl-2-butene is 0.5-2.0 h -1 ; (2) The reacted material enters the distillation tower, and after distillation separation, 2-methyl-1-butene is obtained at the top of the distillation tower, and the 2-methyl-2-butene obtained at the bottom of the distillation tower is returned to the inlet of the fixed bed reactor to continue the reaction; The isomerization catalyst comprises an active component and a carrier, wherein the active component comprises a main active component NiO and an auxiliary active component MgO.

[0017] Preferably, the mass fraction of NiO in the isomerization catalyst is 20%-40%, the mass fraction of MgO is 13%-20%, and the balance is the support.

[0018] Preferably, the carrier of the isomerization catalyst is one or both of SiO2 and Al2O3.

[0019] Preferably, the preparation method of the isomerization catalyst comprises the following steps: a. Dissolve the corresponding nitrates of Ni and Mg in water to prepare a mixed nitrate solution; b. Prepare precipitant solution; c. adding the precipitant solution and the mixed nitrate solution into the reaction tank in sequence, causing a precipitation reaction to produce a precipitate; d. After aging, filtering and washing, the precipitate is added with a carrier and an auxiliary agent, mixed and filtered; e. After drying the filter cake, it is roasted, granulated and formed into tablets to obtain the product.

[0020] The precipitant is nickel nitrate and the auxiliary agent is magnesium nitrate.

[0021] The conversion rate of 2-methyl-2-butene in the present invention is 20%-30%, and the reaction selectivity of generating 2-methyl-1-butene is ≥95%.

[0022] Compared with alkaline metal oxides, NiO has higher isomerization reaction activity and is more suitable for the isomerization reaction of 2-methyl-2-butene. Therefore, NiO is selected as the main active component. However, due to the high NiO content, it is easy to cause the catalyst particles to aggregate and grow larger during the reaction, which is not conducive to improving the service life. Therefore, a certain amount of auxiliary agent MgO must be added to improve the dispersion of NiO and change the electron cloud density of NiO.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses nickel oxide as the main component, which has high reaction activity, and uses magnesium oxide as an auxiliary agent, which helps the synergistic effect of the two and changes the electron cloud density and the number of active sites of nickel oxide, so the reaction temperature is lower; 2. The active component NiO in the isomerization catalyst of the present invention contributes to the synergistic effect of the additive MgO and the carrier SiO2 and / or Al2O3, changing the electron cloud density and the number of active sites of NiO. This will directly affect the adsorption rate of the reactants on the catalyst and the isomerization ability, thereby improving the reaction activity and product selectivity. 3. The present invention has the advantages of high catalyst activity, low reaction temperature, high reaction selectivity, and long catalyst life, which meets market demand. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments.

[0025] The method for isomerizing 2-methyl-2-butene to produce 2-methyl-1-butene according to the present invention comprises the following steps: (1) 2-Methyl-2-butene enters the fixed-bed reactor and undergoes isomerization reaction under the action of the isomerization catalyst; the fixed-bed reactor pressure is 0.15-0.3 MPa, the temperature is 220-250°C, and the mass space velocity of 2-methyl-2-butene is 0.6-1.3 h -1 ; (2) The reacted material enters the distillation tower, and after distillation separation, 2-methyl-1-butene is obtained at the top of the distillation tower, and the 2-methyl-2-butene obtained at the bottom of the distillation tower is returned to the inlet of the fixed bed reactor to continue the reaction; The isomerization catalyst comprises an active component and a carrier, wherein the active component comprises a main active component NiO and an auxiliary active component MgO.

[0026] The preparation method of the isomerization catalyst comprises the following steps: a. Dissolve the corresponding nitrates of Ni and Mg in water to prepare a mixed nitrate solution; b. Prepare precipitant solution; c. adding the precipitant solution and the mixed nitrate solution into the reaction tank in sequence, causing a precipitation reaction to produce a precipitate; d. After aging, filtering and washing, the precipitate is added with a carrier and an auxiliary agent, mixed and filtered; e. After drying the filter cake, it is roasted, granulated and formed into tablets to obtain the product.

[0027] The precipitant is nickel nitrate and the auxiliary agent is magnesium nitrate.

[0028] The specific reaction conditions and evaluation results of Examples 1 to 5 are shown in Table 1.

[0029] Table 1 Reaction conditions and evaluation table of Examples 1-5

Claims

1. A method for isomerizing 2-methyl-2-butene to produce 2-methyl-1-butene, characterized in that: The following steps are involved: (1) 2-Methyl-2-butene enters the fixed bed reactor and undergoes isomerization reaction under the action of the isomerization catalyst; the pressure of the fixed bed reactor is 0.1-0.5Mpa, the temperature is 200-250℃, and the mass space velocity of 2-methyl-2-butene is 0.5-2.0h -1 ; (2) The reacted materials enter a distillation tower, and after distillation and separation, 2-methyl-1-butene is obtained at the top of the distillation tower, and the 2-methyl-2-butene obtained at the bottom of the distillation tower is returned to the inlet of the fixed bed reactor to continue the reaction; The isomerization catalyst comprises an active component and a carrier, wherein the active component comprises a main active component NiO and an auxiliary active component MgO.

2. The method for isomerizing 2-methyl-2-butene to produce 2-methyl-1-butene according to claim 1, characterized in that: The mass fraction of NiO in the isomerization catalyst is 20%-40%, the mass fraction of MgO is 13%-20%, and the balance is the carrier.

3. The method for isomerizing 2-methyl-2-butene to produce 2-methyl-1-butene according to claim 1, characterized in that: The carrier of the isomerization catalyst is one or both of SiO2 and Al2O3.

4. The method for isomerizing 2-methyl-2-butene to produce 2-methyl-1-butene according to claim 1, characterized in that: The preparation method of the isomerization catalyst comprises the following steps: a. Dissolving the corresponding nitrates of Ni and Mg in water to prepare a mixed nitrate solution; b. Prepare precipitant solution; c. adding the precipitant solution and the mixed nitrate solution into the reaction tank in sequence, causing a precipitation reaction to obtain a precipitate; d. After aging, filtering and washing, the precipitate is added with a carrier and an auxiliary agent, mixed and filtered; e. After the filter cake is dried, it is roasted, granulated and formed into tablets to obtain the product.

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