1. A reaction system for preparing propionic acid by ethanol liquid-phase oxo synthesis comprises a first reactor and a second reactor; the method is characterized in that: raw materials of ethanol and carbon monoxide enter a first reactor, the raw materials are subjected to oxo synthesis to obtain propionic acid in a solution containing a catalyst, unreacted ethyl propionate, unreacted carbon monoxide and a catalyst solution enter a second reactor to continuously react, and therefore the conversion rates of the raw materials of carbon monoxide, ethanol, ethyl propionate and diethyl ether are improved.

2. The reaction system for the liquid-phase oxo-synthesis of ethanol to propionic acid according to claim 1, wherein the first reactor is a fully back-mixed reactor, which maintains a high reaction rate; the second reactor is a fully back-mixed reactor or a plug flow reactor that maintains high conversion of the feedstock.

3. A reaction system for the liquid phase oxo-synthesis of ethanol to propionic acid as claimed in claim 1 or claim 2, wherein the pressure in the second reactor is lower than the reaction pressure in the first reactor; the material is transferred from the first reactor to the second reactor by means of a pressure difference.

4. A reaction system for the liquid phase oxo-synthesis of ethanol to propionic acid as claimed in claim 1 or claim 2, wherein the pressure in the first reactor is in the range of 1.0 to 10.0 MPa.

5. The reaction system for preparing propionic acid by ethanol liquid-phase oxo synthesis as claimed in claim 1 or claim 2, wherein the reaction temperature of the first reactor and the second reactor is 170-220 ℃.

6. A reaction system for liquid phase oxo-synthesis of ethanol to propionic acid as claimed in claim 1 or claim 2, wherein the concentration of ethyl propionate in the first reactor is 1% to 20%; the concentration of ethyl propionate in the material at the outlet of the second reactor is 0.5-10%.

7. A reaction system for the liquid phase oxo-synthesis of ethanol to propionic acid as claimed in any one of claims 1 to 6, wherein the raw material ethanol is replaced by ethyl propionate or diethyl ether.

8. The reaction system for liquid-phase oxo-synthesis of ethanol to propionic acid as claimed in claim 1, wherein the catalyst system is a catalyst with rhodium or iridium as main active component and ethyl iodide as auxiliary.

Background

Propionic acid, a three-carbon saturated fatty acid, is mainly used as a food preservative and a mildew preventive.

At present, the industrial production methods mainly comprise three methods: the method is a low-carbon alkane conversion method, which is gradually eliminated due to low selectivity and complex separation; the second is propionaldehyde oxidation method, and the third is ethylene carbonyl synthesis method. At present, the latter two methods are basically adopted internationally. The two methods both adopt ethylene as raw material, China is a poor oil country, the petroleum reserve is limited, and China has mature grain ethanol technology and adopts renewable plant resources, so that the research on the preparation of propionic acid by ethanol carbonylation is more, and particularly the industrialization of the technology for preparing acetic acid by methanol liquid phase carbonylation lays a foundation for the industrialization of the preparation of propionic acid by ethanol liquid phase carbonylation.

The liquid-phase ethanol carbonylation method for preparing propionic acid has more laboratory researches, and mainly comprises the following steps:

du pont, usa first carbonylated with ethanol to afford propionic acid: under the conditions of 180 ℃ and 400 ℃ and 35.5-70.9MPa, boron trifluoride, carbon tetrachloride, copper acetate, manganese or halides of aluminum, nickel, cobalt and iron, chromium, molybdenum, tungstic acid and the like are used as catalysts, and ethanol and carbon monoxide react in an acidic medium to generate propionic acid. The yield of propionic acid is 72%, and the method has not been industrialized so far because the process problems such as reaction rate/yield/catalyst loss, high-temperature and high-pressure equipment corrosion and the like are not solved.

A soluble rhodium carbonyl-iodide catalytic system is reported by F.E.Paulik and the like of Monsanto company in 1968, has high selectivity and catalytic activity on the synthesis of acetic acid by methanol carbonylation, and has mild reaction conditions. Because of the success of rhodium homogeneous catalysis in the carbonylation of methanol to acetic acid, it has been found that the rhodium homogeneous catalysis in the carbonylation of ethanol to propionic acid is also a viable process. In 1985, Thomas W. et al reported the study of the carbonylation kinetics and reaction mechanism of methanol, ethanol, and n-propanol in the presence of rhodium catalysts. The rate of ethanol carbonylation is reported to be only around 1/20 for methanol.

Zhaoweijun et al, from southern Kai university, 1994, synthesized cobalt and nickel complexes containing phosphine ligands and examined the catalytic performance of these complexes on ethyl propionate preparation by ethanol carbonylation; the effect of these different ligands on the catalytic reaction was compared. On the basis of the above, in 1995, nickel, cobalt and palladium complexes containing phosphine and phosphine nitrogen ligands were synthesized, and the catalytic activity was evaluated, and the activity of nickel and cobalt was found to be equivalent, but not comparable to that of palladium.

The Wangzhan university at southern working university in 1996 reported that a catalyst for synthesizing nickel in a hydrogen atmosphere is used for preparing propionic acid and ethyl propionate by liquid-phase ethanol carbonylation, and the influence of factors such as reaction time, complex ligand and solvent on the activity and selectivity of the catalyst is considered, so that a certain effect is achieved.

The 2004 british patent by BP company states that one method for producing propionic acid is to synthesize propionic acid from a carbonylatable reactant, ethanol or its derivatives such as ethyl propionate, in the presence of an iridium catalyst, a rhodium or osmium halide as a promoter.

In 2008, southwest chemical research and design institute used ethanol liquid phase carbonylation to synthesize propionic acid based on the catalyst for preparing acetic acid by methanol carbonylation, wherein the space-time yield of propionic acid was 1 mol/L.h.

In 2013, Laichun wave of Shanghai Huayi group technology research institute reported that propionic acid is synthesized by ethanol liquid-phase carbonylation in an iridium catalyst system, and the space-time yield of propionic acid exceeds 3 mol/L.h.

In 2013, Song hope of Shandong Hualu Hengsheng chemical Co., Ltd reports that the ethanol is carbonylated to synthesize the propionic acid in a rhodium catalytic system, the influence of the feeding speed and the water content on the oxo synthesis is researched, and the maximum space-time yield is 5.2mol/L.h.

In 2014, Jiangsu Sorpu chemical industry Co., Ltd./Shao York of Chinese institute of chemistry/Yuanqing, etc. discloses a preparation method of a dipropylenetriamine/rhodium carbonyl catalyst and application thereof in preparation of propionic acid by ethanol oxo synthesis.

In 2016, shanghai friendship energy and chemical company, tang bin et al, disclose the use of a rhodium-ruthenium catalyst in the preparation of propionic acid by low-pressure ethanol oxo synthesis.

The technology for preparing propionic acid by ethanol liquid-phase carbonyl synthesis mostly stays in the aspect of catalyst development at present, and a large amount of development and utilization are needed in the actual operation part.

Disclosure of Invention

The invention aims to provide an industrialized reaction system for preparing propionic acid by ethanol liquid-phase oxo synthesis according to the characteristics of the reaction for preparing propionic acid by ethanol liquid-phase oxo synthesis, which comprises the following steps: two reactors are connected in series, and the first reactor adopts a full back-mixing reactor to maintain a higher reaction speed; the second reactor adopts a full back-mixing or plug flow reactor, so that the ethyl propionate and the carbon monoxide are further converted, the circulation amount of the ethyl propionate is reduced, and the utilization rate of the carbon monoxide is improved. Compared with a single reactor with the same volume, the reaction system can obtain higher capacity under the same condition.

In order to achieve the above purpose, the specific technical scheme of the invention is as follows:

a reaction system for preparing propionic acid by ethanol liquid-phase oxo synthesis comprises a first reactor and a second reactor; raw materials of ethanol and carbon monoxide enter a first reactor, the raw materials are subjected to oxo synthesis to obtain propionic acid in a solution containing a catalyst, unreacted ethyl propionate, unreacted carbon monoxide and a catalyst solution enter a second reactor to continuously react, and therefore the conversion rates of the raw materials of carbon monoxide, ethanol, ethyl propionate and diethyl ether are improved.

The raw material ethanol can be replaced by ethyl propionate or diethyl ether; the ethyl alcohol enters the reactor and is then esterified with propionic acid to form ethyl propionate, the ether enters the reactor and is then hydrolyzed to form ethyl alcohol, and the ethyl alcohol and propionic acid are esterified to form ethyl propionate.

As a preferred embodiment in the present application, the first reactor is a fully back-mixed reactor, which maintains a high reaction rate; the second reactor is a fully back-mixed or plug flow reactor that maintains high conversion of the feedstock, which allows greater capacity to be obtained under the same conditions than a single reactor of the same volume.

As a preferred embodiment herein, the pressure in the second reactor is lower than the reaction pressure in the first reactor; the material is transferred from the first reactor to the second reactor by means of a pressure difference without consuming excessive energy.

As a preferred embodiment herein, the pressure in the first reactor is in the range of 1.0 to 10.0MPa, preferably 1.2 to 8.0MPa, more preferably 1.5 to 5.0 MPa.

As a preferred embodiment of the present application, the reaction temperature of the first reactor and the second reactor is 170-220 ℃.

As a preferred embodiment herein, the concentration of ethyl propionate in the first reactor is between 1% and 20%, preferably between 1.5% and 10%; the concentration of ethyl propionate in the second reactor outlet material is 0.5-10%, preferably 1.0-5%.

In a preferred embodiment of the present application, the catalyst system is a catalyst with rhodium or iridium as a main active component and iodoethane as an auxiliary agent, and the catalyst is a commercially available product.

Through the intensive research on the preparation of propionic acid by ethanol liquid-phase carbonyl synthesis, aiming at the characteristics of the reaction, the invention provides an industrialized reaction system scheme which comprises the following steps: two reactors are connected in series, the first reactor adopts a full back-mixing reactor (ethanol is used as a raw material, the main reaction involved in the reactor is shown in (2) (3), ethyl propionate is used as a raw material, the reaction formula involved in the reactor is shown in (3), diethyl ether is used as a raw material, the reaction formula involved in the reactor is shown in (1) (2) (3)), and a high reaction speed is maintained; the second reactor adopts a full back-mixing or plug flow reactor (the reaction formula involved in the reactor is shown in (3)), so that the ethyl propionate and the carbon monoxide are further converted, the circulating amount of the ethyl propionate is reduced, and the utilization rate of the carbon monoxide is improved. This allows to obtain a greater capacity than a single reactor of the same volume, under the same conditions.

CH₃CH₂COOCH₂CH₃+H₂O+CO→2CH₃CH₂COOH (3) in contrast to the prior artIn comparison, the positive effects of the invention are as follows:

two reactors are connected in series, and the first reactor adopts a full back-mixing reactor to maintain a higher reaction speed; the second reactor adopts a full back-mixing or plug flow reactor, so that the ethyl propionate and the carbon monoxide are further converted, the circulation amount of the ethyl propionate is reduced, and the utilization rate of the carbon monoxide is improved.

And secondly, the reaction system for preparing the propionic acid by the ethanol liquid-phase carbonyl can be industrially designed, and the yield can be higher than that of a single reactor with the same volume.

Drawings

FIG. 1 is a schematic flow diagram of a reaction system for liquid phase carbonylation of ethanol to produce propionic acid in example 1, wherein two fully back-mixed reactors are connected in series;

wherein 101 is a first reactor, 102 is a second reactor, 1 is a first reactor vapor phase material, 2 is a first reactor liquid phase material, 3 is a second reactor vapor phase material, and 4 is a second reactor liquid phase material.

FIG. 2 is a schematic diagram of a series connection of a full back-mixing reactor and a plug flow reactor;

FIG. 2 is a schematic diagram of a reaction system for liquid-phase carbonylation of ethanol to produce propionic acid according to example 2 (the first reactor is a total back-mixing reactor, and the second reactor is a plug flow reactor);

wherein 101 is a first reactor, 102 is a second reactor, 1 is a first reactor vapor phase material, 2 is a first reactor liquid phase material, and 3/4 is a second reactor vapor phase material.

Detailed Description

A reaction system for preparing propionic acid by ethanol liquid-phase carbonyl synthesis comprises the following steps: feeding reactive raw materials such as raw materials of ethanol or ethyl propionate or ethyl ether and carbon monoxide into a first reactor, wherein the first reactor contains a propionic acid solution of a catalyst and a cocatalyst, and in the reactor, if the ethyl ether is used for feeding, the ethyl ether is firstly hydrolyzed into ethanol (shown in a reaction formula (1)), then the ethanol and the propionic acid are subjected to an esterification reaction (shown in a reaction formula (2)) to generate ethyl propionate, and finally the ethyl propionate is partially carbonylated to generate the propionic acid (shown in a reaction formula (3)); if an ethanol feed is used, the ethanol is firstly subjected to an esterification reaction with propionic acid (see the reaction formula (2)) to generate ethyl propionate, and then the ethyl propionate is partially carbonylated to generate propionic acid (see the reaction formula (3)); if an ethyl propionate feed is employed, the ethyl propionate is partially carbonylated to produce propionic acid (see equation (3)); the unreacted carbon monoxide and organic steam in the first reactor and the byproduct hydrogen and carbon dioxide (material 1) enter a second reactor, the liquid phase (material 2) in the first reactor also enters the second reactor, and the ethyl propionate continues to be synthesized with CO carbonyl in the second reactor to generate propionic acid, and the utilization rate of the carbon monoxide and the conversion rate of the ethyl propionate are improved after the ethyl propionate passes through the two reactors.

CH₃CH₂COOCH₂CH₃+H₂O+CO→2CH₃CH₂COOH (3)

The reaction system for preparing propionic acid by ethanol liquid-phase carbonyl synthesis comprises a first reactor and a second reactor, wherein the first reactor is a full back-mixing reactor and keeps high reaction speed; the second reactor is a full back-mixing or plug flow reactor; maintaining a high conversion of the feedstock allows to obtain a higher capacity under the same conditions than a single reactor of the same volume.

The reaction system for preparing propionic acid by ethanol liquid phase oxo synthesis has the first reactor pressure of 1.0-10.0MPa, preferably 1.2-8.0MPa, and more preferably 1.5-5.0 MPa. The pressure of the second reactor is lower than the reaction pressure of the first reactor; the material is transferred from the first reactor to the second reactor by means of a pressure difference without consuming excess energy. The pressure difference is based on the principle that the material in the first reactor can be smoothly fed into the second reactor.

The reaction system for preparing propionic acid by ethanol liquid phase oxo synthesis, which is disclosed by the invention, has the reaction temperature of 170-220 ℃ in the first reactor and the temperature of 170-220 ℃ in the second reactor 102. The temperatures of the two reactors may be the same or different.

According to the reaction system for preparing propionic acid by ethanol liquid-phase oxo synthesis, the concentration of ethyl propionate in the first reactor is preferably 1.0-20%, and more preferably 1.5-10%; the concentration of ethyl propionate in the second reactor outlet stream is preferably from 0.5 to 10%, more preferably from 1.0 to 5.0%.

The reaction system for preparing propionic acid by ethanol liquid phase oxo synthesis adopts ethanol or ethyl propionate, diethyl ether and the like as raw materials.

The invention relates to a reaction system for preparing propionic acid by ethanol liquid-phase oxo synthesis, wherein a catalyst system is rhodium or iridium, an auxiliary agent is iodoethane, water and propionic acid are used as solvents, iodide ions are used as a catalyst stabilizer, and the catalyst is a commercially available product.

The specific embodiment provides a reaction system for preparing propionic acid by ethanol liquid-phase carbonyl synthesis, which comprises the following steps:

(1) the solution containing the raw material, the catalyst and the cocatalyst is prepared, and the catalyst and the cocatalyst are prepared in the feeding to simulate the continuous reaction process because the reaction system is not linked with the separation system, so that the catalyst and the cocatalyst cannot return to the reaction system.

(2) In order to keep the concentration of the catalyst constant, the initially added material in the reactor is the same as the prepared material, and because the prepared material has higher ethanol content, after the temperature is raised for reaction for a period of time, the ingredients are continuously added after the composition of the reaction liquid reaches a preset value, so that the reaction is always maintained in a preset state.

(3) The purpose of the comparative example is to contrast with the inventive example, so the reactor outlet feed composition was made to coincide with the second reactor outlet reaction liquid of the inventive example by changing the feed flow rate.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.

The catalysts used in the reactors of the following examples are commercially available products.

Example 1:

preparing a reaction liquid raw material containing 10 wt% of ethanol (the detailed composition is shown in a raw material row in a table 1), adding the prepared reaction liquid into two serially-connected stirred reactors (a first reactor, 1L) and (a second reactor, 200ml), replacing three times with carbon monoxide, pressurizing to 0.3MPa with the carbon monoxide, heating two stirred kettles to 200 ℃, supplementing the carbon monoxide to the pressure of 4.0MPa in the first reactor, starting a feeding pump after 1 hour, adding the prepared reaction liquid at the speed of 15g/min, taking a vapor phase outlet and a liquid phase outlet of the first reactor and the second reactor after stable operation for 30 minutes, taking a tail gas composition and a reaction liquid composition by using a gas chromatography, wherein the vapor phase and the liquid phase are both sampled by adopting chilled water cooling and sampling. The results are shown in Table 1:

TABLE 1 gas-liquid composition of each of the two back-mixing kettles during series operation

Example 2:

preparing reaction liquid containing 10 wt% of ethanol (the detailed composition is shown in a raw material row in a table 2), adding the prepared reaction liquid into a 1L stirring reactor and a 200mL tubular reactor (two kettles are connected in series, the stirring type reaction is performed before (a first reactor), the tubular reactor is performed after (a second reactor)), replacing the reaction liquid with carbon monoxide for three times, pressurizing the reaction liquid to 0.3MPa by using the carbon monoxide, heating the two kettles to 200 ℃, supplementing the carbon monoxide to 4MPa, and starting a feeding pump, wherein the pressure of the second reactor is 3.7MPa, the prepared reaction liquid is added at the speed of 15g/min, a vapor phase outlet and a liquid phase outlet of the first reactor and the second reactor are taken after 30 minutes, and the vapor phase and the liquid phase are sampled by adopting chilled water cooling and sampling, and the tail gas phase composition and the reaction liquid composition are measured by gas phase chromatography. The results are shown in Table 2:

TABLE 2 gas-liquid composition of each reactor when the full back-mixing reactor and the plug flow reactor are operated in series

COMPARATIVE EXAMPLE 1 (COMPARATIVE EXAMPLE 1)

Preparing a reaction liquid raw material containing 10 wt% of ethanol (the detailed composition is shown in a raw material row in a table 3), adding the prepared reaction liquid into a 1.2L stirring reactor, replacing the reaction liquid with carbon monoxide for three times, pressurizing the reaction liquid to 0.3MPa with the carbon monoxide, heating the reactor to 200 ℃, supplementing the carbon monoxide to the pressure of the reactor of 4MPa, starting a feeding pump after 1 hour, adding the prepared reaction liquid at the speed of 12g/min, taking a vapor phase outlet and a liquid phase outlet of the reactor after stable operation is carried out for 30 minutes, (the vapor phase and the liquid phase are both cooled and sampled by adopting chilled water), and measuring the tail gas composition and the reaction liquid composition by using gas chromatography. The results are shown in Table 3:

TABLE 3 gas-liquid composition during operation of Single complete back-mixing kettle (comparative example 1)

As can be seen from comparative example 1, in order to obtain the same outlet composition, the feed rate to the single pot (12g/min) was lower than the feed rate to the double pot (15 g/min).

COMPARATIVE EXAMPLE 2 (COMPARATIVE EXAMPLE 2)

Preparing a reaction liquid raw material containing 10 wt% of ethanol (the detailed composition is shown in a raw material row in a table 4), adding the prepared reaction liquid into a 1.2L stirring reactor, replacing the reaction liquid with carbon monoxide for three times, pressurizing the reaction liquid to 0.3MPa with the carbon monoxide, heating the reactor to 200 ℃, supplementing the carbon monoxide to the pressure of the reactor of 4MPa, starting a feeding pump after 1 hour, adding the prepared reaction liquid at the speed of 11g/min, taking a vapor phase outlet and a liquid phase outlet of the reactor after stable operation is carried out for 30 minutes, (the vapor phase and the liquid phase are both cooled and sampled by adopting chilled water), and measuring the tail gas composition and the reaction liquid composition by using gas chromatography. The results are shown in Table 4:

TABLE 4 gas-liquid composition during operation of Single complete back-mixing kettle (comparative example 2)

As can be seen from comparative example 2, in order to obtain the same outlet composition, the feed rate to the single pot (11g/min) was lower than the feed rate to the double pot (15 g/min).

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.