阅读说明：本技术 一种催化环己酮肟气相重排制备己内酰胺的方法 (Method for preparing caprolactam by catalyzing cyclohexanone-oxime gas phase rearrangement ) 是由 李相呈 杨为民 王振东 刘闯 于 2020-06-24 设计创作，主要内容包括：本发明公开了一种己内酰胺的制备方法,包括以SCM-14分子筛为催化剂,原料环己酮肟溶于低碳醇溶剂后,经气相重排反应合成己内酰胺的步骤。该方法在较低的反应温度和较高空速下,具有环己酮肟高效转化和己内酰胺选择性高的特点。(The invention discloses a preparation method of caprolactam, which comprises the step of taking an SCM-14 molecular sieve as a catalyst, dissolving cyclohexanone-oxime serving as a raw material in a low-carbon alcohol solvent, and then carrying out gas phase rearrangement reaction to synthesize the caprolactam. The method has the characteristics of high-efficiency conversion of cyclohexanone-oxime and high caprolactam selectivity at a lower reaction temperature and a higher space velocity.)

1. A preparation method of caprolactam is characterized by comprising the step of taking an SCM-14 molecular sieve as a catalyst, dissolving cyclohexanone-oxime serving as a raw material in a low-carbon alcohol solvent, and then carrying out gas phase rearrangement reaction to synthesize caprolactam.

2. The method for preparing caprolactam according to claim 1, wherein the raw material cyclohexanone oxime is dissolved in a low-carbon alcohol solvent, mixed with an inert carrier gas, preheated to a gaseous phase, and then conveyed to a reactor for rearrangement reaction to synthesize caprolactam.

3. Process for the preparation of caprolactam according to claim 1, wherein the reaction temperature in the reaction is 260-360 ℃, preferably 280-340 ℃.

4. The process for producing caprolactam according to claim 1, wherein the weight space velocity of the raw material in the reaction is 1.0 to 8.0 hours^-1Preferably 2.0-6.0h^-1And still more preferably 2.0 to 4.0 hours^-1。

5. Process for the preparation of caprolactam according to claim 1, wherein the SiO of SCM-14 molecular sieve₂/GeO₂The molar ratio is 2.0 or more.

6. Process for the preparation of caprolactam according to claim 1, wherein the SiO of SCM-14 molecular sieve₂/GeO₂The molar ratio is 2.0-8.0.

7. Process for the preparation of caprolactam according to claim 1, wherein the SiO of SCM-14 molecular sieve₂/GeO₂The molar ratio is 2.0-5.0.

8. The process for producing caprolactam according to claim 1 or 2, wherein the lower alcohol solvent is at least one selected from the group consisting of C1-C4 alcohols, preferably at least one selected from the group consisting of methanol and ethanol.

9. Process for the preparation of caprolactam according to claim 1 or 2, characterized in that the content of cyclohexanone oxime in the starting material, cyclohexanone oxime dissolved in the lower alcohol solvent, is 5-40 wt.%, preferably 10-20 wt.%.

10. The process for producing caprolactam according to claim 2, wherein the inert carrier gas is at least one of nitrogen, argon, helium and carbon dioxide.

Technical Field

The invention relates to the field of catalytic chemistry, in particular to a method for preparing caprolactam by catalyzing cyclohexanone oxime to carry out gas phase rearrangement.

Background

Caprolactam is an important organic chemical raw material, is an important monomer for synthesizing nylon-6 and nylon-6 (PA6) engineering plastics, and has excellent thermal stability, processability, mechanical property and chemical resistance. The main consumption fields of caprolactam are fibers (civil silk, industrial silk and carpet silk), engineering plastics and food packaging films, and the caprolactam is widely applied to the fields of automobiles, ships, medical products, daily necessities, electronics, electronic components and the like. Caprolactam is prepared mainly from cyclohexanone oxime by Beckman rearrangement. The prior industrial production takes oleum as a catalyst, converts cyclohexanone oxime into caprolactam sulfate, and then neutralizes the caprolactam sulfate by ammonia, and the process not only produces a large amount of low-efficiency fertilizer ammonium sulfate, but also causes serious environmental pollution. The new process for synthesizing caprolactam by the gas-phase cyclohexanone-oxime rearrangement reaction catalyzed by solid acid does not pollute the environment, is easy for large-scale industrial application, conforms to the development trend of green chemistry, and is widely concerned by scientists.

As early as in 1996,et al (Journal of catalysis.1999,186,12-19) designed and prepared Silicalite-1 molecular sieves with high density of Si-OH groups on the outer surface thereof which can catalyze the Beckman rearrangement of cyclohexanone oxime with high selectivity to caprolactam. 10 weight percent of ethanol solution of cyclohexanone-oxime is taken as raw material, the conversion rate of cyclohexanone-oxime and the selectivity of caprolactam product reach 86 percent and 97 percent respectively at the lower temperature of 300 ℃, but the weight space velocity of the reaction is very low and is only 0.33h^-1. Yang et Al (Catalysis communications.2011,12,399-^-1Under the condition, the caprolactam is prepared by catalyzing the rearrangement of cyclohexanone-oxime, and the selectivity of the caprolactam product is low and is only 65.0 percent. Deng et al (Industrial)&Engineering Chemistry research.2012,51,9492-9499) investigated the catalytic performance of nano-type Silicalite-1 molecular sieve in cyclohexanone oxime rearrangement reaction. Taking 10 wt% of ethanol solution of cyclohexanone-oxime as raw material, reacting at 370 ℃ for 6h^-1Under the condition of high weight space velocity, the cyclohexanone-oxime is basically completely converted, and the selectivity of caprolactam reaches 88.2 percent. Chinese patent CN104307556A describes MFI-type zeolites treated with a nitrogen-containing organic base in combination with an organosilaneThe sub-sieve realizes the high-efficiency conversion of the cyclohexanone-oxime under the high-temperature reaction condition of 390 ℃, the cyclohexanone-oxime is basically and completely converted, and the selectivity of caprolactam reaches 96.5 percent. In conclusion, the prior art shows good catalytic activity in the reaction of preparing caprolactam by cyclohexanone-oxime gas phase rearrangement, but also has the problems of low weight space velocity of raw materials or high reaction temperature, which causes overlarge reaction energy consumption and brings great problems to industrial practical application.

Disclosure of Invention

The invention aims to solve the technical problem of low space velocity or high reaction temperature of raw materials in the prior art, and provides a method for preparing caprolactam by catalyzing cyclohexanone oxime gas phase rearrangement, which has the characteristics of high-efficiency conversion of cyclohexanone oxime and high selectivity of caprolactam at lower reaction temperature and higher space velocity.

In order to solve the technical problem, the invention provides a preparation method of caprolactam, which comprises the step of taking an SCM-14 molecular sieve as a catalyst, dissolving cyclohexanone-oxime serving as a raw material in a low-carbon alcohol solvent, and then carrying out gas phase rearrangement reaction to synthesize caprolactam.

Further, the raw material cyclohexanone oxime is dissolved in a low-carbon alcohol solvent, mixed with an inert carrier gas, preheated into a gas phase and conveyed to the reactor.

Further, a fixed bed reactor is preferably used, in which the SCM-14 molecular sieve can be used as a catalyst after being formed, for example, the SCM-14 molecular sieve is sieved to 40-60 meshes and then tableted and formed.

Further, the reaction temperature in the reaction is 260-360 ℃, preferably 280-340 ℃; the weight space velocity of the raw material is 1.0-8.0h^-1Preferably 2.0-6.0h^-1And still more preferably 2.0 to 4.0 hours^-1。

Further, SiO of the SCM-14 molecular sieve₂/GeO₂The molar ratio is more than 2.0, preferably 2.0-8.0, and in the value range, SiO₂/GeO₂Non-limiting specific points of the molar ratio may be 2.0, 2.5, 2.7, 3.0, 3.5, 3.6, 3.7, 3.8, 4.0, 4.2, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5; most preferably 2.0-5.0.

Further, the specific surface area (BET method) of the SCM-14 molecular sieve is 120-330m²Per g, preferably 170-280m²(ii) in terms of/g. The micropore volume (t-plot method) of the SCM-14 is 0.05-0.15cm³Per g, preferably from 0.06 to 0.12cm³/g。

Further, the lower alcohol solvent is selected from at least one of C1-C4 alcohols, preferably at least one of methanol and ethanol.

Further, the content of the cyclohexanone oxime dissolved in the low-carbon alcohol solvent is 5-40 wt%, preferably 10-20 wt%.

Further, the inert carrier gas is at least one of nitrogen, argon, helium, and carbon dioxide.

The SCM-14 molecular sieve and the method for preparing the same of the present invention are further described in chinese patent application CN109081360A, which is hereby incorporated by reference in its entirety.

According to the invention, the SCM-14 molecular sieve is used as a catalyst to catalyze the gas phase rearrangement of cyclohexanone-oxime to prepare caprolactam, the conversion rate of cyclohexanone-oxime and the selectivity of caprolactam product are very high under the conditions of low reaction temperature and high weight space velocity, and the technical effect is outstanding in the technical field.

Detailed Description

The reaction product caprolactam is analyzed and characterized by gas chromatography-mass spectrometry (GC-MS), and the product caprolactam yield and the conversion rate of reaction substrate cyclohexanone oxime are analyzed by Gas Chromatography (GC). The gas chromatograph-mass spectrometer is Agilent 7890A of Agilent, America, a chromatographic column is an HP-5 nonpolar capillary column (30m, 0.53mm), the gas chromatograph is Agilent 7890B, the detector is a hydrogen Flame Ionization Detector (FID), and the chromatographic column is an SE-54 capillary column (30m, 0.53 mm).

The formula of the conversion rate of cyclohexanone oxime is as follows:

the conversion of cyclohexanone oxime: (molar amount of cyclohexanone oxime reacted)/(molar amount of cyclohexanone oxime as a reaction substrate) × 100%.

The yield of the product caprolactam is calculated by the formula:

the yield of caprolactam which is a product (% by mol of caprolactam produced by the reaction)/(the molar amount of cyclohexanone oxime which is a reaction substrate) x 100%.

The selectivity of the product caprolactam was ═ molar (caprolactam formed by the reaction)/(molar cyclohexanone oxime reacted) × 100%.

For the convenience of understanding the present invention, the present invention will be described below with reference to examples, which are only for the purpose of facilitating understanding of the present invention and should not be construed as specifically limiting the present invention.

Example 1

This example uses SiO₂/GeO₂An SCM-14 molecular sieve (prepared by adopting the preparation method of CN109081360A example 4) with the molar ratio of 2.7 is used as a catalyst, and the SCM-14 molecular sieve catalyst is sieved to 40-60 meshes by adopting a normal-pressure continuous flow fixed bed reactor device and is tabletted and molded. Taking 20 wt% methanol solution of cyclohexanone-oxime as raw material, the reaction temperature is 300 ℃, and the weight space velocity of cyclohexanone-oxime is 2.0h^-1And taking nitrogen as carrier gas, and collecting the reaction product after cooling by water circulation. The reaction solution is subjected to gas phase analysis to obtain the cyclohexanone-oxime with the conversion rate of 91 percent and the caprolactam selectivity of 97 percent.

Example 2

This example uses SiO₂/GeO₂An SCM-14 molecular sieve with the molar ratio of 2.7 (the preparation method of the molecular sieve is the same as that in example 1) is used as a catalyst, and an ordinary-pressure continuous-flow fixed bed reactor device is adopted to sieve the SCM-14 molecular sieve catalyst into 40-60 meshes for tabletting and forming. Taking a methanol solution of 15 wt% cyclohexanone oxime as a raw material, wherein the reaction temperature is 300 ℃, and the weight space velocity of the cyclohexanone oxime is 3.0h^-1And taking nitrogen as carrier gas, and collecting the reaction product after cooling by water circulation. The reaction solution was subjected to gas phase analysis to obtain cyclohexanone oxime with a conversion of 86% and caprolactam selectivity of 98%.

Example 3

This example uses SiO₂/GeO₂SCM-14 molecular sieve with a molar ratio of 4.2 (preparation of molecular sieve same as example 1, only SiO was adjusted)₂/GeO₂The molar ratio) is used as a catalyst, and an ordinary pressure continuous flow fixed bed reactor device is adopted to sieve the SCM-14 molecular sieve catalyst to 40-60 meshes for tabletting and forming. At 15wtEthanol solution of% cyclohexanone oxime as raw material, reaction temperature is 340 ℃, and weight reaction space velocity of cyclohexanone oxime is 3.0h^-1And taking nitrogen as carrier gas, and collecting the reaction product after cooling by water circulation. Gas phase analysis is carried out on the reaction liquid to obtain the cyclohexanone-oxime with the conversion rate of 93 percent and the caprolactam selectivity of 96 percent.

Example 4

This example uses SiO₂/GeO₂SCM-14 molecular sieve with a molar ratio of 3.5 (preparation of molecular sieve in the same way as in example 1, only SiO was adjusted)₂/GeO₂The molar ratio) is used as a catalyst, and an ordinary pressure continuous flow fixed bed reactor device is adopted to sieve the SCM-14 molecular sieve catalyst to 40-60 meshes for tabletting and forming. Taking 10 wt% of ethanol solution of cyclohexanone-oxime as raw material, the reaction temperature is 280 ℃, and the weight reaction space velocity of cyclohexanone-oxime is 2.0h^-1Carbon dioxide is used as carrier gas, and reaction products are collected after being cooled by water circulation. The reaction solution was subjected to gas phase analysis to obtain cyclohexanone oxime with a conversion of 81% and caprolactam selectivity of 95%.

Example 5

This example uses SiO₂/GeO₂SCM-14 molecular sieve with a molar ratio of 3.6 (preparation of molecular sieve in the same way as in example 1, only SiO was adjusted)₂/GeO₂The molar ratio) is used as a catalyst, and an ordinary pressure continuous flow fixed bed reactor device is adopted to sieve the SCM-14 molecular sieve catalyst to 40-60 meshes for tabletting and forming. Taking 20 wt% methanol solution of cyclohexanone-oxime as raw material, the reaction temperature is 320 ℃, and the weight reaction space velocity of cyclohexanone-oxime is 2.4h^-1Argon is used as carrier gas, and reaction products are collected after being cooled by water circulation. The reaction solution was subjected to gas phase analysis to obtain cyclohexanone oxime with a conversion of 83% and caprolactam selectivity of 96%.

Example 6

This example uses SiO₂/GeO₂SCM-14 molecular sieve with a molar ratio of 3.5 (preparation of molecular sieve in the same way as in example 1, only SiO was adjusted)₂/GeO₂The molar ratio) is used as a catalyst, and an ordinary pressure continuous flow fixed bed reactor device is adopted to sieve the SCM-14 molecular sieve catalyst to 40-60 meshes for tabletting and forming. With 10% by weight of cyclohexanone oximeThe methanol solution is taken as a raw material, the reaction temperature is 340 ℃, and the weight reaction space velocity of the cyclohexanone-oxime is 2.0h^-1Argon is used as carrier gas, and reaction products are collected after being cooled by water circulation. Gas phase analysis is carried out on the reaction liquid to obtain the cyclohexanone-oxime with the conversion rate of 93 percent and the caprolactam selectivity of 94 percent.

Example 7

This example uses SiO₂/GeO₂SCM-14 molecular sieve with a molar ratio of 3.7 (preparation of molecular sieve in the same way as in example 1, only SiO was adjusted)₂/GeO₂The molar ratio) is used as a catalyst, and an ordinary pressure continuous flow fixed bed reactor device is adopted to sieve the SCM-14 molecular sieve catalyst to 40-60 meshes for tabletting and forming. Taking 20 wt% of ethanol solution of cyclohexanone-oxime as raw material, the reaction temperature is 300 ℃, and the weight reaction space velocity of cyclohexanone-oxime is 3.6h^-1Argon is used as carrier gas, and reaction products are collected after being cooled by water circulation. The reaction solution was subjected to gas phase analysis to obtain cyclohexanone oxime with a conversion of 83% and caprolactam selectivity of 95%.

Example 8

This example uses SiO₂/GeO₂SCM-14 molecular sieve with a molar ratio of 4.2 (preparation of molecular sieve same as example 1, only SiO was adjusted)₂/GeO₂The molar ratio) is used as a catalyst, and an ordinary pressure continuous flow fixed bed reactor device is adopted to sieve the SCM-14 molecular sieve catalyst to 40-60 meshes for tabletting and forming. Taking 15 wt% ethanol solution of cyclohexanone-oxime as raw material, the reaction temperature is 320 ℃, and the weight reaction space velocity of cyclohexanone-oxime is 2.4h^-1Helium is used as carrier gas, and reaction products are collected after being cooled by water circulation. The reaction solution is subjected to gas phase analysis to obtain cyclohexanone oxime with the conversion rate of 82% and the selectivity of caprolactam of 95%.

Comparative example 1

The method of embodiment 1 of the chinese patent CN1142147C is adopted to synthesize the titanium silicalite molecular sieve as the catalyst, the reaction conditions are the same as those of embodiment 1, and a normal pressure continuous flow fixed bed reactor device is adopted to sieve the titanium silicalite molecular sieve catalyst to 40-60 meshes for tabletting and forming. Taking 20 wt% methanol solution of cyclohexanone-oxime as raw material, the reaction temperature is 300 ℃, and the weight space velocity of cyclohexanone-oxime is 2.0h^-1And taking nitrogen as carrier gas, and collecting the reaction product after cooling by water circulation. The reaction solution is subjected to gas phase analysis to obtain the cyclohexanone-oxime with the conversion rate of 64 percent and the caprolactam selectivity of 94 percent.

Comparative example 2

The method adopts the Silicate-1 molecular sieve synthesized in the example 2 of Chinese patent CN1338427A as a catalyst, adopts the reaction conditions as in the example 1, adopts a normal-pressure continuous flow fixed bed reactor device, sieves the SCM-14 molecular sieve catalyst to 40-60 meshes, and performs tabletting and molding. Taking 20 wt% methanol solution of cyclohexanone-oxime as raw material, the reaction temperature is 300 ℃, and the weight space velocity of cyclohexanone-oxime is 2.0h^-1And taking nitrogen as carrier gas, and collecting the reaction product after cooling by water circulation. The reaction solution was subjected to gas phase analysis to obtain cyclohexanone oxime with a conversion of 73% and caprolactam selectivity of 92%.

As can be seen from the experimental data of examples 1-8 and comparative examples 1-2, by using SCM-14 molecular sieve as the catalyst, the reaction temperature is relatively low (280 ℃ C. and 340 ℃ C.) and the weight space velocity is high (2.0-6.0 h)^-1) Under the condition, the conversion rate of cyclohexanone-oxime and the selectivity of caprolactam which is a product are both very high, but the catalysts prepared according to Chinese patents CN1142147C and CN1338427A can not achieve the catalytic effect of the catalyst in the technical scheme of the invention under the same reaction condition.