KR100873271B1 - Method of producing unsaturated aldehyde and/or unsaturatede fatty acid in fixed-bed catalytic partial oxidation reactor with high efficiency - Google Patents

Abstract

The present invention provides a process for preparing unsaturated aldehydes and / or unsaturated fatty acids from olefins by fixed-bed catalytic partial oxidation in a shell-and-tube heat exchange reactor. , Second time period,. , Divided by the nth time interval (n is a natural number of 2 or more), and the operating conditions in the first time interval are lower than the space velocity of the olefin based on the operating conditions in the nth time interval. The temperature is set high, the ratio of molecular oxygen and olefin (volume ratio of fractional element / volume of olefin) is low, and the amount of water flowing into the reactor is set high, and the time period is changed before the nth time period after the first time period. If present, the manufacturing process is characterized in that in the time interval after the first time interval and before the nth time interval, the operating conditions are sequentially changed from the operating condition criterion of the first section to the operating condition criterion of the nth time section.

Shell-and-Tube Heat Exchanger, Unsaturated Aldehydes, Unsaturated Fatty Acids

Description

METHODS OF PRODUCING UNSATURATED ALDEHYDE AND / OR UNSATURATEDE FATTY ACID IN FIXED-BED CATALYTIC PARTIAL OXIDATION REACTOR WITH HIGH EFFICIENCY}

1 is a schematic diagram showing the structure of a shell-and-tube type multi-tube reactor in which Example 1 and Comparative Example 1 are performed.

Figure 2 is a schematic diagram showing a catalyst charging structure for one reaction tube in the reactor of FIG.

The present invention relates to a process for producing unsaturated aldehydes and / or unsaturated fatty acids from olefins using metal oxides as catalysts in shell-and-tube heat exchanger type reactors, in more detail. Relates to startup and initial operation after charging the catalyst to the reactor.

The process for producing unsaturated aldehydes and / or unsaturated acids from olefins in the gas phase using a catalyst corresponds to representative catalytic vapor phase oxidation.

As a specific example of the catalytic phase oxidation reaction, a process of oxidizing propylene or propane to produce acrolein and / or acrylic acid, and isobutylene, t-butyl alcohol or methyl-t-butyl ether to oxidize methacrolein and / or methacrylic acid Manufacturing process;

In general, a catalytic gas phase oxidation reaction includes one or more catalysts filled in a reaction tube in the form of granules, a feed gas is supplied to the reactor through the reaction tube, and the feed gas is brought into contact with the catalyst in the reaction tube to perform a gas phase oxidation reaction. To perform. The heat of reaction generated during the reaction is removed by heat transfer with the heat transfer medium, and the temperature of the heat transfer medium is maintained at a predetermined temperature. At this time, the heat transfer medium for heat exchange is provided on the outer surface of the reaction tube to transfer heat. The reaction mixture containing the desired product is sent through tubes to the collection recovery and purification steps. Since the catalytic phase oxidation reaction is usually a high exothermic reaction, it is very important to control the reaction temperature within a specific range and to reduce the size of the hot spot in the reaction zone.

In the partial oxidation reaction of olefins, molybdenum and bismuth or molybdenum and vanadium-containing complex oxides or mixtures thereof are used as catalysts.

In general, the final product (meth) acrylic acid is produced by two stages of catalytic gas phase partial oxidation reaction from propylene, isobutylene, t-butylalcohol or methyl-t-butylether (hereinafter referred to as propylene). . That is, in the first step, propylene or the like is oxidized by oxygen, dilute inert gas, water vapor, and any amount of catalyst to produce (meth) acrolein, and in the second step, oxygen, dilute inert gas, water vapor, and any amount of catalyst The (meth) acrolein is oxidized to produce (meth) acrylic acid. The first stage catalyst is an oxidation catalyst based on Mo-Bi, and mainly oxidizes propylene to produce (meth) acrolein. In addition, some (meth) acrolein continues to oxidize on this catalyst to produce some (meth) acrylic acid. The second stage catalyst is an oxidation catalyst based on Mo-V, and mainly (meth) acrolein is oxidized in the (meth) acrolein-containing mixed gas produced in the first stage to mainly produce (meth) acrylic acid.

The reactor for performing such a process may be provided to perform the above two steps in one apparatus, or may be provided to perform the two steps of processes in different devices.

The first step may be divided into two or more reaction zones as described in Korean Patent 2002-0040043. In the first reaction zone of the first stage, the reaction is violently performed due to the relatively high concentration of propylene and the amount of oxygen in the entire reactor, and hot spots of the catalyst layer are easily formed.

Furthermore, when producing (meth) acrolein and / or (meth) acrylic acid using high space velocities and high concentrations of propylene or the like, as non-ideal temperature rises occur in the reactor, active component release from the catalyst bed, metal components Problems such as a decrease in the number of active sites due to the sintering of the sintering may be caused and the function may be degraded.

Up to now, the plant has been started for about 24 hours. At this time, when producing at the desired space velocity such as the final propylene and the composition of the reactants, the temperature of the hot spot is excessively high in the first stage, so that the catalyst It was observed that there are many damaged contact tubes, and in the second stage, side reactions are actively progressed, and more by-products such as carbon monoxide, carbon dioxide, and acetic acid are generated, which lowers the yield of unsaturated fatty acids such as (meth) acrylic acid. There was.

The catalyst used in the production of unsaturated aldehydes and / or unsaturated acids from olefins, such as the production of (meth) acrolein or (meth) acrylic acid from propylene, etc., is a metal oxide, and the characteristics of the catalyst are active at the start-up. Since it is very high, the side reaction proceeds relatively much, lowering the yield of (meth) acrolein or (meth) acrylic acid, and raising the temperature of the catalyst layer to damage the catalyst.

In order to solve the above problem, the present invention is to start up and charge the catalyst by gradually adjusting the composition and reaction temperature of the mixed gas flowing into the reactor for a predetermined time (for example about 120 hours) after charging the catalyst It is intended to provide an optimized method for initial operation.

The present invention provides a process for preparing unsaturated aldehydes and / or unsaturated fatty acids from olefins by fixed-bed catalytic partial oxidation in a shell-and-tube heat exchange reactor. , Second time period,. , Divided by the nth time interval (n is a natural number of 2 or more), and the operating conditions in the first time interval are lower than the space velocity of the olefin based on the operating conditions in the nth time interval. The temperature is set high, the ratio of molecular oxygen and olefin (volume ratio of fractional assets / volume ratio of olefin) is low, and the amount of water flowing into the reactor is set high, and the time interval is changed before the nth time interval after the first time interval. If present, a manufacturing process characterized in that the operating conditions are sequentially changed from the operating condition criterion of the first time interval to the operating condition criterion of the nth time interval in the time interval after the first time interval and before the nth time interval. .

Hereinafter, the present invention will be described in detail.

The present invention is characterized by stepwise adjusting the olefin space velocity, the heat transfer medium temperature, the volume ratio of water in the total mixed gas, the volume ratio of molecular oxygen / olefin volume flows into the reactor for a predetermined time after the catalyst is charged.

By increasing the concentration of propylene and the like in the mixed gas flowing into the reactor step by step and by decreasing the temperature of the heat transfer medium step by step from a relatively high temperature to a low temperature, it is possible to reduce the side reaction by suppressing excessive reaction at the beginning of the reaction, the temperature in the catalyst bed Can prevent a sharp rise. At the initial stage of startup, the temperature of the heat transfer medium filled in the shell is set higher than the temperature of the normal operation, and the (volume ratio of powdered fraction) / (volume ratio such as propylene) is operated at a lower state than in the normal operation, so that the catalyst It may contribute to reducing side reactions by removing excess molecular oxygen contained in. By increasing the amount of water and decreasing it step by step, the amount of heat generated excessively at the beginning of the reaction can be removed, and the temperature of the hot spot in the catalyst layer can be lowered.

In one embodiment of the present invention, a space velocity of 40 to 80% of the target olefin space velocity in the nth time interval after the catalyst filling, the temperature of the heat transfer medium filled in the shell is 320 ~ 340 ℃, into the reactor The volume ratio of water in the inlet mixed gas is set to 10 to 15%, the volume ratio of molecular oxygen / olefin to 1.65 to 1.75, and the space velocity of the desired final olefin is 110 to 185 hr-1, in the nth period. The temperature of the heat transfer medium may be operated by setting the volume ratio of water to 5.0 to 8.0% and the volume ratio of molecular oxygen / olefin to 1.8 to 1.9 in the total mixed gas flowing into the reactor at 300 to 320 ° C.

In the present invention, the first time period to the n-th time period may correspond to a start-up time, and the nth time period may correspond to a final normal operation time.

After filling the catalyst and starting the reaction, the time interval is divided into two or more sections, and the space velocity of the desired propylene such as the final propylene in the last time section, nth, is 100 hr ⁻¹ or more and less than 200 hr ⁻¹ , Preferably it is 110-185hr ^-1 . If the space velocity of the olefin is less than 100 hr ^{-1, the} productivity decreases. At 200 hr ^-1 or more, the catalyst may be burned out due to the increase in hot spot temperature due to shortening of the catalyst life and excessive exotherm.

If there is a time interval after the first time interval and before the nth time interval, the space velocity of the olefin is increased by 0 to 30hr ^-1 and the temperature of the heat transfer medium is increased based on the adjacent previous time interval in each time interval. Lowering by 0 ~ 15 ℃, it is preferable to increase the ratio of molecular oxygen and olefin (volume ratio of fractional assets / volume ratio of olefin) by 0 ~ 0.1, and the amount of water introduced into the reactor is reduced by 0 ~ 5%. The olefin space velocity, heat transfer medium temperature, moisture volume ratio, molecular oxygen volume ratio, and olefin volume ratio were sequentially changed so as not to affect the temperature of the hot spot in the catalyst bed from the first time period to the nth normal operation. It is the core of the present invention, and the range that does not give a sudden change is as mentioned above.

In the present invention, 'the operating conditions are sequentially changed from the operating condition criterion of the first time period to the operating condition of the nth time period', the olefin space velocity, heat transfer medium temperature, moisture volume ratio, molecular oxygen volume ratio At least one of the volume ratios of the / olefin is the same as the previous time interval, that is, the amount of change = 0.

The first time period is preferably 12 to 48 hours after the start of the reaction. When the number of time sections n is three or more, the second time section is preferably 36 to 72 hours. When the number of time sections n is four or more, the third time section is preferably 60 to 96 hours. When the number of time intervals n is five or more, the fourth time interval is preferably 84 to 120 hours. When the number of time intervals n is six or more, it is preferable that the fifth time interval is 108 to 144 hours. The time range is based on long experimental results.

The total time range from the first time interval to the n-th time interval (start-up) is preferably 48 to 120 hours. If the start-up time is within 48 hours, it is difficult to exert an effect of reducing side reactions and lowering the temperature of the hot spot in the catalyst bed, and if it is more than 120 hours, the productivity per unit time is reduced because the normal operation time is reduced.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

<Reactor Installation>

The reactor as shown in Figure 1 was used, the inner diameter of the contact tube in the reactor is 26mm, the thickness of the wall is 2mm, the thermocouple protective tube is installed in the middle of the contact tube in the contact tube, the outer diameter of the thermocouple protective tube is 1/8 It is configured to measure the temperature of the entire region of the reactor using a thermocouple in the thermocouple protective tube in inches. In the outer wall of the contact tube, molten salt circulated to maintain a constant temperature of the contact tube, and raw materials were introduced into the contact tube from the bottom. In the contact tube catalyst filling, as shown in Fig. 2, sequentially filled a 250 mm inert material layer (alumina), 1550 mm LGC1, 150 mm inert material layer, 1450 mm LGC2. The LGC1 and LGC2 are the first stage oxidation catalyst layer based on molybdenum (Mo) and bismuth (Bi) as the first stage catalyst material, and the preparation method of the catalyst is Korean Patent No. 0349602 (Application No. 10-1997-0045132) It is described in. The molten salt circulated on the outer wall of the contact tube is controlled at the same temperature from below to 1800mm (first reaction zone in the first stage), and the upper part (second reaction zone in the first stage) is controlled independently of the temperature of the molten salt at the bottom. The temperature of the LGC1 layer and the temperature of the LGC2 layer can be set differently, and the mixed gas of the raw materials entering the contact tube can be introduced into the reactor at a sufficiently high temperature through the preheating device before entering the reactor. After the LGC2 layer was filled with a mixture of 700mm inert material and 15% by weight of LGC4. Next, 800mm LGC3 and 1900mm LGC4 were sequentially charged, and the LGC3 and LGC4 are second stage oxidation catalyst layers based on molybdenum (Mo) and vanadium (V) as second stage catalyst materials. The preparation method is described in Korean Patent No. 0378018 (Application No. 10-1998-0054814). The molten salt of the outer wall of the contact tube (second stage reaction zone) filled with LGC3 and LGC4 may be temperature controlled independently of the molten salt of the outer wall of the contact tube filled with the first stage catalyst material.

 Example 1

After charging the catalyst, the temperature of the molten salt in the first reaction zone of the first stage was 330 degrees, the temperature of the molten salt in the second reaction zone of the first stage was 340 degrees, and the temperature of the molten salt in the second stage of the reaction zone was 290 degrees. , The space velocity of propylene is 75 hr ^-1 , the volume ratio of water in the mixed gas flowing into the reactor is 13.0% of the total mixed gas, and the ratio of molecular oxygen and propylene (volume ratio of powdered assets / volume ratio of propylene) to 1.70 After 24 hours, the composition of the reactants was analyzed and the distribution of temperature in the catalyst layer was measured. Every 24 hours, the reaction temperature and the composition of the raw materials were gradually changed as shown in Table 1, and the composition of the reactants after 120 hours and the temperature in the catalyst layer were measured and compared. In this example, start-up was divided into five stages. The temperature of the molten salt in the first reaction zone of the first stage of the last section (the fifth time section) was 305 degrees and the temperature of the molten salt in the second reaction zone of the first stage was 315 degrees. , The temperature of the molten salt in the second reaction zone is set to 270 degrees, the space velocity of propylene is 75 hr ^-1 , the volume ratio of water in the mixed gas flowing into the reactor is 7.5% of the total mixed gas, molecular oxygen and propylene The ratio of (volume ratio of minute assets / volume ratio of propylene) was introduced to 1.85.

Reaction time (Hr) 24 (hour 1 section) 48 (Second Hour) 72 (3rd hour interval) 96 (4 hours) 120 (5th hour interval) C ₃ H ₆ (Volume%) 5.0 6.0 7.0 7.5 7.5 C ₃ H ₆ .SV (hr ^-1 ) 75.0 90.0 105.0 112.5 112.5 O ₂ / C ₃ H ₆ 1.70 1.75 1.80 1.85 1.85 HTS1 / HTS2 (℃) 330/340 320/333 312/328 308/325 305/315 HTS3 (℃) 290 275 273 272 270 Moisture content (%) 13.0 10.5 9.0 7.5 7.5

SV (space velocity): hr ^-1 (Standard Temperature and Pressure, STP)

O ₂ / C ₃ H ₆ : volume ratio of molecular oxygen / volume ratio of propylene.

HTS (Heat Transfer Salt): Molten salt circulating on the outer wall of the reactor.

% Conversion: [moles of propylene participating in the reaction / moles of total propylene entered] * 100

Table 2 shows the analysis results and the temperature of the hot spots.

Reaction time (Hr) 24 (hour 1 section) 48 (Second Hour) 72 (3rd hour interval) 96 (4 hours) 120 (5th hour interval) Conversion rate 98.44% 98.39% 98.27% 97.97% 97.41% AA yield 83.65% 84.13% 84.45% 84.70% 84.34% COx yield 10.50% 10.00% 9.62% 9.15% 8.60% Hot Spot Temp. (LGC1) 379.1 ℃ 379.2 ℃ 378.8 ℃ 378.4 ℃ 374.5 ℃ ΔT of Hot Spot and HTS1 49.1 ℃ 59 ℃ 59.5 ℃ 70.4 ℃ 69.5 ℃ Hot Spot Temp. (LGC3) 333.1 ℃ 322.3 ℃ 333.4 ℃ 328.8 ℃ 319.8 ℃ ΔT on Hot Spots and HTS3 41.7 ℃ 47.3 ℃ 60.4 ℃ 56.8 ℃ 49.8 ℃

Comparative Example 1

After the catalyst was charged, the temperature of the molten salt in the first reaction zone of the first stage was 305 ° C, the temperature of the molten salt in the second reaction zone of the first stage was 315 ° C, and the temperature of the molten salt in the second stage of the reaction zone was 270 ° C. The space velocity of propylene is 112.5 hr ^-1 , the volume ratio of water in the mixed gas flowing into the reactor is 7.5% of the total mixed gas, and the ratio of molecular oxygen and propylene (volume ratio of powdered assets / volume ratio of propylene) is 1.85. The composition of the reactants was analyzed every 24 hours by loading up the feed, and the temperature in the catalyst bed was measured. Table 3 shows the analysis results and the temperature of the hot spots.

Reaction time (Hr) 24 (hour 1 section) 48 (Second Hour) 72 (3rd hour interval) 96 (4 hours) 120 (5th hour interval) Conversion rate 97.36% 97.42% 97.46% 97.21% 97.37% AA yield 82.84% 83.09% 83.19% 83.08% 83.20% COx yield 10.29% 10.13% 9.75% 9.63% 9.61% Hot Spot Temp. (LGC1) 377.0 ℃ 379.2 ℃ 378.8 ℃ 383.2 ℃ 383.2 ℃ ΔT of Hot Spot and HTS1 72.0 ℃ 74.2 ℃ 73.8 ℃ 78.2 ℃ 78.2 ℃ Hot Spot Temp. (LGC3) 334.9 ℃ 328.7 ℃ 327.8 ℃ 326.0 ℃ 323.3 ℃ ΔT on Hot Spots and HTS3 64.9 ℃ 58.7 ℃ 57.8 ℃ 56.0 ℃ 53.3 ℃

Comparative Example 2

After the catalyst was charged, the temperature of the molten salt in the first reaction zone of the first stage was 305 ° C, the temperature of the molten salt in the second reaction zone of the first stage was 315 ° C, and the temperature of the molten salt in the second stage of the reaction zone was 270 ° C. The volume velocity of propylene is 75 hr ^-1 , the volume ratio of water in the mixed gas flowing into the reactor is 7.5% of the total mixed gas, and the ratio of molecular oxygen and propylene (volume ratio of powdered assets / volume ratio of propylene) is 1.85. Loaded up to flow. Every 24 hours, the space velocity of propylene was increased as in Example 1, and the reaction temperature and the composition of the raw materials were kept constant regardless of time as in Comparative Example 1. Table 4 shows the analysis results and the temperature of the hot spots.

Reaction time (Hr) 24 (hour 1 section) 48 (Second Hour) 72 (3rd hour interval) 96 (4 hours) 120 (5th hour interval) Conversion rate 97.17% 97.63% 97.46% 97.53% 97.43% AA yield 82.21% 83.12% 83.22% 83.38% 83.40% COx yield 10.57% 10.37% 10.18% 10.04% 9.88% Hot Spot Temp. (LGC1) 348.0 ℃ 359.3 ℃ 359.9 ℃ 384.5 ℃ 385.0 ℃ ΔT of Hot Spot and HTS1 43 ℃ 54.3 ℃ 54.9 ℃ 79.5 ℃ 80.0 ℃ Hot Spot Temp. (LGC3) 311.7 ℃ 321.8 ℃ 322.7 ℃ 325.3 ℃ 327.5 ℃ ΔT on Hot Spots and HTS3 41.7 ℃ 51.8 ℃ 52.7 ℃ 55.3 ℃ 57.5 ℃

Table 5 compares the temperature difference of the hot spot with the analysis result of Example 1, Comparative Example 1, Example 1, and Comparative Example 2. As shown in Table 5, compared with Comparative Examples 1 and 2 in Example 1, the AA yield was improved, the COx yield as a side reaction was reduced, and the temperature of the hot spot was lowered, indicating that the process was stabilized.

Comparison after 120 hours Comparative Example 1 Example 1 △ 1 Comparative Example 2 Example 1 △ 2 Conversion rate 97.37% 97.41% 0.04% 97.43% 97.41% -0.02% AA yield 83.20% 84.34% 1.14% 83.40% 84.34% 0.95% COx yield 9.61% 8.60% -1.01% 9.88% 8.60% -1.28% Hot Spot Temp. (LGC1) 383.2 ℃ 374.5 ℃ -8.7 ℃ 385 ℃ 374.5 ℃ -10.5 Hot Spot Temp. (LGC3) 323.3 ℃ 319.8 ℃ -3.5 ℃ 327.5 ℃ 319.8 ℃ -7.7

When starting up after filling the catalyst, by adjusting the composition and reaction temperature of the reactants step by step as in the method of the present invention, the conversion temperature in the first reaction zone of the first stage is not lowered, and the temperature of the hot spot is significantly lowered, thereby reducing the active ingredient from the catalyst layer. Stable production can be achieved by reducing problems such as desorption and reduction of the number of active sites due to sintering of metal components, reducing the amount of COx (carbon monoxide and carbon dioxide) in the product, and producing highly efficient (meth) acrylic acid.

Claims (13)

A process for producing unsaturated aldehydes and / or unsaturated fatty acids from olefins by fixed bed catalytic partial oxidation in a shell-and-tube heat exchange reactor, After the catalyst is charged and the reaction is started, the time intervals are sequentially selected from the first time interval, the second time interval,. , Divide by the nth time interval (n is a natural number of 2 or more), The operating conditions in the first time period were low in the space velocity of olefin based on the operating conditions in the last n time period, the temperature of the heat transfer medium filled in the shell was high, and the ratio of molecular oxygen and olefins (volume ratio of minute assets). / Olefin volume ratio) is low, the amount of water flowing into the reactor is set to operate, If there is a time interval after the first time interval but before the nth time interval, in the time interval after the first time interval and before the nth time interval, the operation conditions of the first period to the operating condition criteria of the nth time interval are sequentially Manufacturing process characterized by changing the operating conditions. The process of claim 1, wherein the space velocity of the final olefin in the nth time period is 100 hr ⁻¹ or more but less than 200 hr ⁻¹ . The method of claim 1, wherein in the first time period after the catalyst filling, the space velocity of 40-80% of the olefin fin space velocity in the n-th time interval, the temperature of the heat transfer medium filled in the shell is 320-340 ° C, and introduced into the reactor. The manufacturing process characterized in that the operation by setting the volume ratio of water in the total mixed gas to 10 to 15%, the volume ratio of molecular oxygen / olefin to 1.65 ~ 1.75. The method of claim 1, wherein in the n-th time interval, the space velocity of the olefin is 110 ~ 185hr ^-1 , the heat transfer medium temperature is 300 ~ 320 ℃, the volume ratio of water in the total mixed gas flowing into the reactor 5.0 ~ 8.0%, molecular oxygen Production process characterized in that the operation by setting the volume ratio of / olefin volume ratio of 1.8 ~ 1.9. The method of claim 1, wherein if there is a time interval after the first time interval before the nth time interval, the space velocity of the olefin is increased by 0 ~ 30hr ^{-1 in} each of the time intervals based on the adjacent previous time intervals The temperature of the heat transfer medium is lowered by 0 ~ 15 ℃, and the ratio of molecular oxygen and olefin (volume ratio of fractional element / volume of olefin) is increased by 0 ~ 0.1, and the amount of water flowing into the reactor is reduced by 0 ~ 5%. Characterized in that the manufacturing process. The process according to claim 1, wherein the first time period is 12 to 48 hours after the start of the reaction. The process according to claim 1, wherein when the number of time sections n is three or more, the second time section is 36 to 72 hours after the start of the reaction. The process according to claim 1, wherein when the number of time sections n is four or more, the third time section is 60 to 96 hours after the start of the reaction. The process according to claim 1, wherein when the number of time sections n is 5 or more, the fourth time section is 84 to 120 hours after the start of the reaction. The process according to claim 1, wherein when the number of time sections n is 6 or more, the fifth time section is 108 to 144 hours after the start of the reaction. The process of claim 1, wherein the total time range from the first time period to the n-th time period is 48 to 120 hours. The process according to any one of claims 1 to 11, wherein the olefin is at least one selected from the group consisting of propylene, isobutylene, t-butyl alcohol or methyl t-butyl ether. delete

Images