CN1169711C - Method for prepn. of high concentration hydroxymaline in the prodn. process of hexanolactam - Google Patents
Method for prepn. of high concentration hydroxymaline in the prodn. process of hexanolactam Download PDFInfo
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- CN1169711C CN1169711C CNB021512264A CN02151226A CN1169711C CN 1169711 C CN1169711 C CN 1169711C CN B021512264 A CNB021512264 A CN B021512264A CN 02151226 A CN02151226 A CN 02151226A CN 1169711 C CN1169711 C CN 1169711C
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Abstract
The present invention discloses a method for preparing hydroxylamine with high concentration in the production process of caprolactam. The present invention adopts a production method of two reaction vessels connected in series and adopts high superficial velocity, and a liquid and liquid quick mixer is added between the two reaction vessels so as to accelerate the micro mixing of intermediate supplementing nitric acid and the outlet inorganic liquid of the first reaction vessel. Therefore, the method can obviously increase the hydroxylamine concentration, greatly reduce the circulation of the inorganic liquid and reduce the operation cost of relevant infusion devices and heat exchange devices, and the investment cost of the devices can also be reduced. Meanwhile, the two vessels are connected in series, so the flow type of the inorganic liquid tends to flat push flow from original complete mixing flow. Therefore, the method can reduce the side reactions of the series connection of the hydroxylamine so as to keep high reaction selectivity when obtaining the hydroxylamine with high concentration, and the unit consumption of reaction raw materials is not obviously increased.
Description
Technical Field
The invention relates to a preparation method of high-concentration hydroxylamine, in particular to a method for generating hydroxylamine by hydrogenation reduction of nitrate.
Background
Caprolactam is an important chemical raw material and a monomer for synthesizing nylon 6 and engineering plastics. The cyclohexanone-hydroxylamine process is currently the predominant process for preparing caprolactam, and therefore, the production of hydroxylamine directly affects the production cost and yield of caprolactam during the production of caprolactam. The traditional production method of hydroxylamine is to react dilute aqueous nitric acid solution (inorganic liquid for short) with ammonium hydrogen phosphate as buffer solution with hydrogen in the presence of bimetallic Pd + Pt/C or monometallic Pd/C catalyst in a single-tower reactor, as reported in Moesdijk, C.van de (1979), Thesis, THEIndhoven. The reaction formula is as follows:
due to H in inorganic liquid in single tower reactor+、NO3 -The concentration is limited by a plurality of process factors, so the NH in the inorganic liquid after the reaction3OH+The concentration is low, and each kilogram of inorganic liquid contains 0.7 to 0.8mol of hydroxylamine ions, so that a large amount of water is circulated in the production system. The process has a low capacity to produce hydroxylamine and is not satisfactory and therefore must be improved.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a preparation method of high-concentration hydroxylamine in a caprolactam production process, so as to overcome the defect of low production efficiency in the prior art.
The technical idea of the invention is as follows:
the reaction of generating hydroxylamine by hydrogenating and reducing nitrate is a heterogeneous reaction with simultaneous existence of gas-liquid-solid three phases, the catalyst is a bimetallic Pd + Pt/C or monometallic Pd/C catalyst, the concentration of hydroxylamine in the reaction product is directly influenced by the concentration of the catalyst, the hydrogen partial pressure and the hydrogen ion concentration, and researches show that the hydroxylamine hydrogenation reduction and the hydroxylamine disproportionation reaction are inversely proportional to the 0.4 th power of the hydrogen ion concentration, are proportional to the catalyst concentration and are unrelated to the hydrogen partial pressure. Therefore, the inventor designs a production method with two reactors connected in series, optimizes process parameters, adopts high altitude tower linear speed, increases a liquid-liquid rapid mixer between the two reactors, and accelerates the micro mixing of the middle supplementary nitric acid and inorganic liquid at the outlet of the first reactor to prevent hydroxylamine from decomposing under the strong acid condition. Through the secondary reaction, the concentration of hydroxylamine in the outlet liquid of the reactor is improved, so as to achieve the purpose of increasing the yield.
The technical scheme of the invention is as follows:
the method of the invention comprises the following steps:
the method comprises the steps of enabling raw material inorganic liquid to enter the middle-lower part of a first reactor firstly, enabling the raw material inorganic liquid to react with hydrogen entering from the bottom of the first reactor in the presence of a catalyst to generate hydroxylamine, enabling inorganic liquid containing hydroxylamine to overflow from the top of the first reactor and then enter a first gas-liquid separator, enabling inorganic liquid containing low-concentration hydroxylamine and asmall amount of catalyst to enter a first filter, enabling the filtered catalyst to be sent back to the first reactor, enabling the inorganic liquid containing low-concentration hydroxylamine to enter a mixer to be rapidly mixed with additionally fed nitric acid, enabling the inorganic liquid to enter the middle-lower part of a second reactor to react with hydrogen entering from the bottom of the second reactor in the presence of the catalyst, enabling the concentration of hydroxylamine in the inorganic liquid to be increased to 1.3-1.35mol/kg from 0.7-0.85 mol/kg, enabling the inorganic liquid to enter a second gas-liquid separator from the top of the second reactor, enabling the inorganic liquid containing high-concentration hydroxylamine and a small amount, the filtered catalyst is returned to the second reactor and the inorganic liquid containing hydroxylamine at a high concentration is sent to the subsequent step. Unreacted hydrogen in the first reactor and the second reactor is discharged from the top of the reactors, and can be sent into the reactors again for recycling after being compressed by a circulating compressor.
The invention has the advantages that the invention has remarkable effect, the hydroxylamine concentration can be obviously improved by connecting two reactors in series and supplementing nitric acid in the middle, the circulation amount of inorganic liquid is remarkably reduced, the operation cost of related infusion equipment and heat exchange equipment is reduced, the investment cost of the equipment can also be reduced, and simultaneously, the flow pattern of the inorganic liquid tends to plug flow from the original fully mixed flow due to the adoption of the two towers connected in series, so that the series side reaction of hydroxylamine can be reduced, the high reaction selectivity can be still kept while the high-concentration hydroxylamine is obtained, and the unit consumption of reaction raw materials is not remarkably increased.
Drawings
FIG. 1 is a schematic flow chart of the present invention.
Detailed Description
Referring to fig. 1, a raw material inorganic liquid firstly enters a first reactor 1 from the middle lower part of the first reactor 1, reacts with hydrogen entering from the bottom of the first reactor 1 in the presence of a catalyst to generate hydroxylamine, the inorganic liquid containing hydroxylamine overflows from the top of the first reactor 1 and enters a first gas-liquid separator 2, the inorganic liquid containing low-concentration hydroxylamine and a small amount of catalyst enters a first filter 3, the filtered catalyst is returned to the first reactor 1, the inorganic liquid containing low-concentration hydroxylamine enters a mixer 4 to be mixed with nitric acid which is additionally fed, then enters the middle lower part of a second reactor 5 to continue reacting with hydrogen entering from the bottom of the second reactor 5 in the presence of the catalyst, so that the concentration of hydroxylamine in the inorganic liquid is increased from 0.7-0.85 mol/kg to 1.3-1.35mol/kg, and then enters a second gas-liquid separator 6 from the top of the second reactor 5, the inorganic liquid containing high concentration hydroxylamine and a small amount of catalyst enters the second filter 7, the filtered catalyst is returned to the second reactor 5, and the inorganic liquid containing high concentration hydroxylamine is sent to the subsequent process. Unreacted hydrogen in the first reactor 1 and the second reactor 5 flows out from the top of the reactors, and can be sent into the reactors again for recycling after being compressed by a circulating compressor.
The component and content of the raw material inorganic liquid comprise H3PO4(19～21wt％)、NH3OHH2PO4(0.5～1.0wt％)、NH4NO3(17～24wt％)、HNO3(1～4wt％)、H2O(50～61wt％)。
The weight ratio of the amount of the additionally fed nitric acid to the inorganic liquid at the outlet of the first reactor 1 is 1: 0.10-1: 0.25, and the concentration of the nitric acid is 60-68 wt%.
For the first reactor 1, due to the low hydroxylamine concentration, a single or double metal mixed catalyst can be adopted, the reaction rate is increased, and the maximum production capacity is pursued. For the second reactor 5, a single Pd/C catalyst may be used because of the higher hydroxylamine concentration, and although the reaction rate may be slightly decreased, the reaction selectivity to hydroxylamine may be improved. Therefore, the selectivity of the whole reaction system can be kept at a proper level, the yield of hydroxylamine after expansion is ensured, and the production cost is reduced. The Pd/C and Pt + Pd/C single and double metal mixed catalysts are reported in Lopatin, V.L., K.A.Lezhneva, N.V.Kul' kova and M.I.Temkin (1979), Kinet.Katal., 20, 302-.
The adopted reactor is a bubbling reactor;
the reaction temperature is higher than 65 ℃, the generation of by-products is accelerated, the temperature is lower than 55 ℃, the nitrate radical reduction rate is obviously reduced, and the optimal reaction temperature is about 60 ℃.
The superficial linear velocity of the inorganic reaction liquid is 0.13-0.18 m/s, and too high superficial linear velocity can cause gas-liquid entrainment, and too low can reduce liquid phase circulation volume and gas-liquid mass transfer rate.
The mixer for replenishing the nitric acid is an efficient liquid-liquid quick mixer, can ensure that the replenished nitric acid is instantly and quickly mixed with inorganic liquid at the outlet of the first reactor, and meets the process requirements.
EXAMPLE 1
The raw material inorganic liquid has the component and the content of H3PO4(20wt％)、NH3OHH2PO4(0.75wt％)、NH4NO320wt％)、HNO3(2.5wt％)、H2O(55wt％)。
90000 kg/h of inorganic raw liquid enters a first reactor 1 from the middle lower part of the reactor 1, reacts with hydrogen entering from the bottom of the first reactor 1 in the presence of a catalyst to generate hydroxylamine, the concentration of the hydroxylamine is 0.8mol/kg, the inorganic liquid containing hydroxylamine overflows from the top of the first reactor 1, enters a first gas-liquid separator 2, the inorganic liquid containing low-concentration hydroxylamine and a small amount of catalyst enters a first filter 3, the filtered catalyst is returned to the first reactor 1, the inorganic liquid containing low-concentration hydroxylamine enters a mixer 4, is mixed with additionally fed nitric acid, then enters the middle lower part of a second reactor 5, continuously reacts with hydrogen entering from the bottom of the second reactor 5 in the presence of the catalyst to increase the concentration of hydroxylamine in the inorganic liquid to 1.35mol/kg, and then enters a second gas-liquid separator 6 from the top of the second reactor 5, the inorganic liquid containing high concentration hydroxylamine and a small amount of catalyst enters the second filter 7, the filtered catalyst is returned to the second reactor 5, and the inorganic liquid containing high concentration hydroxylamine is sent to the subsequent process. Unreacted hydrogen in the first reactor 1 and the second reactor 5 flows out from the top ofthe reactors, and can be sent into the reactors again for recycling after being compressed by a circulating compressor.
The first reactor 1 adopts a single-metal and double-metal mixed catalyst, the second reactor 5 adopts a single Pd/C catalyst, and the adopted reactor is a bubbling reactor;
the reaction temperature was 60 ℃, the superficial linear velocity of the inorganic reaction solution was 0.15m/s, and the amount of the additionally fed 66 wt% nitric acid was 12700 kg/h.
Claims (7)
1. A preparation method of high-concentration hydroxylamine in a caprolactam production process is characterized by comprising the following steps:
the method comprises the steps of enabling raw inorganic liquid to enter a first reactor (1) from the middle lower part of the first reactor (1), enabling the raw inorganic liquid to react with hydrogen entering from the bottom of the first reactor (1) in the presence of a catalyst to generate hydroxylamine, enabling the inorganic liquid containing hydroxylamine to overflow from the top of the first reactor (1) and enter a first gas-liquid separator (2), enabling the inorganic liquid containing low-concentration hydroxylamine and a small amount of catalyst to enter a first filter (3), enabling the filtered inorganic liquid to enter a mixer (4), mixing with nitric acid fed additionally, then entering the middle lower part of a second reactor (5), enabling the inorganic liquid to continue reacting with hydrogen entering from the bottom of the second reactor (5) in the presence of the catalyst to enable the concentration of hydroxylamine in the inorganic liquid to be increased from 0.7-0.85 mol/kg to 1.3-1.35mol/kg, and then entering a second gas-liquid separator (6) from the top of the second reactor (5), the inorganic liquid containing high-concentration hydroxylamine and a small amount of catalyst enters a second filter (7), the inorganic liquid after filtration is sent to a subsequent process, and unreacted hydrogen in the first reactor (1) and the second reactor (5) flows out from the top of the reactors;
the raw material inorganic liquid comprises the following components in percentage by weight: h3PO419～21wt％、NH3OHH2PO40.5～1.0wt％、NH4NO317～24wt％、HNO31 to 4 wt% and H2O50～61wt％；
The first reactor (1) adopts a single-metal and double-metal mixed catalyst, and the second reactor (5) adopts a single Pd/C catalyst.
2. The method according to claim 1, wherein the weight ratio of the amount of the additionally fed nitric acid to the inorganic liquid at the outlet of the reactor 1 is 1: 0.10 to 1: 0.25.
3. The process according to claim 1, wherein the reaction temperature is 55 ℃ to 65 ℃.
4. The method according to claim 1, wherein the superficial linear velocity of the inorganic reaction solution is 0.13 to 0.18 m/s.
5. The process according to claim 1, characterized in that the reactor employed is a bubble reactor; the mixer for adding the nitric acid is a high-efficiency liquid-liquid quick mixer.
6. The method according to claim 1, characterized in that the catalyst filtered out by the first filter (3) is returned to the first reactor (1) and the catalyst filtered out by the second filter (7) is returned to the second reactor (5).
7. The method according to any one of claims 1 to 6, wherein unreacted hydrogen in the first reactor (1) and the second reactor (5) flows out from the top of the reactors, is compressed by a recycle compressor, and is sent to the reactors again for recycling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB021512264A CN1169711C (en) | 2002-12-11 | 2002-12-11 | Method for prepn. of high concentration hydroxymaline in the prodn. process of hexanolactam |
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| Application Number | Priority Date | Filing Date | Title |
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| CNB021512264A CN1169711C (en) | 2002-12-11 | 2002-12-11 | Method for prepn. of high concentration hydroxymaline in the prodn. process of hexanolactam |
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| CN1418809A CN1418809A (en) | 2003-05-21 |
| CN1169711C true CN1169711C (en) | 2004-10-06 |
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| CNB021512264A Expired - Lifetime CN1169711C (en) | 2002-12-11 | 2002-12-11 | Method for prepn. of high concentration hydroxymaline in the prodn. process of hexanolactam |
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Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1330563C (en) * | 2005-08-04 | 2007-08-08 | 浙江大学 | Method of preparing solid hydroxylamine hydrochloride |
| CN103987658A (en) | 2011-12-29 | 2014-08-13 | 帝斯曼知识产权资产管理有限公司 | Process for the continuous preparation of hydroxylamine |
| CN103848406A (en) * | 2012-11-30 | 2014-06-11 | 帝斯曼知识产权资产管理有限公司 | Method for continuously separating water-based hydroxylammonium salt by use of demister |
| CN104557706B (en) * | 2013-10-28 | 2017-06-30 | 中国石油化工股份有限公司 | A kind of hexanolactam hydrofining process |
| CN104557707B (en) * | 2013-10-28 | 2017-02-08 | 中国石油化工股份有限公司 | Caprolactam hydrofining method |
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2002
- 2002-12-11 CN CNB021512264A patent/CN1169711C/en not_active Expired - Lifetime
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