WO2009006815A1 - A method of protecting catalyst used for preparing low fatty ester - Google Patents

Abstract

A method of protecting catalyst used for preparing low fatty ester is provided. An acid ion exchanging resin catalyst is protected by washing 2-5C olefin to eliminate part of catalyst toxin in olefin before they enter the reactor; and eliminating harmful substances of 1-4C fatty acid and/or 2-5C olefin using reaction assistant agent in a pre-reactor. The advantage of the invention is that the method prevents catalyst poisoning since the harmful impurities have been eliminated, so that catalyst will not lose reactive ability when it is used more than 6 months, at the same time the reaction assistant agent for protecting the catalyst has no metal ion crossing filter phenomenon, and there is small pressure difference between the bed layers of the reaction agent.

Description

 Method for protecting catalyst for preparing lower fatty acid ester

Technical field

 This invention relates to a process for the protection of catalysts, and more particularly to a process for protecting a catalyst for the preparation of lower fatty acid esters.

Background technique

 The use of ion exchange resin as a catalyst to catalyze the reaction of lower fatty acids and lower olefins to synthesize lower fatty acid esters generally has a better reaction effect. However, most of the ion exchange resin catalysts have low chemical stability and thermal stability, and are prone to swelling or loss of active components in long-term use, which in turn leads to catalyst deactivation.

 U.S. Patent 5,457,228 discloses the use of a styrene sulfonic acid ion exchange resin or a phenol sulfonic acid resin as a catalyst to catalyze the reaction of acetic acid with propylene to form isopropyl acetate or acetic acid with 1-butene or 2-butene to produce sec-butyl acetate. The process is characterized in that the tubular fixed bed reactor and the reaction material mixing cycle are used to effectively control the reaction temperature, avoid catalyst corrosion, slow down the catalyst deactivation, and inhibit the reverse reaction rate and the olefin polymerization side reaction. However, according to the knowledge of those familiar with the profession, organic carboxylic acids and chain olefins as raw materials may contain a small amount of metal ions, basic substances and sulfur-containing substances, which can be adsorbed on the ion exchange resin, causing catalyst loss. live. When the olefin used is a mixed hydrocarbon, such as when C4 is mixed, the diene and isobutylene in the mixed C4 are liable to coke, thereby causing the catalyst to be deactivated. Therefore, in the case of esterification of an organic carboxylic acid and a chain olefin by using an ion exchange resin as a catalyst, it is necessary to pretreat the reaction raw material to remove catalyst toxin and factors which may cause catalyst deactivation, thereby prolonging the service life of the catalyst.

 The applicant's patent application No. 200710200147.5 discloses a method of pretreating a reaction raw material with an ion exchange resin-based protective agent before the reaction to thereby prolong the service life of the catalyst. The method can effectively protect the reaction catalyst and prolong its catalytic activity. However, since the exchange capacity of the protective agent is limited, when the catalyst toxin is contained in the reaction raw material, the protective agent is also susceptible to the toxicity of the catalyst toxin and gradually loses the protective property. When the olefin used is a mixed hydrocarbon, if C4 is mixed, the mixed C4 contains a small amount of metal ions, a basic substance, a sulfur-containing substance, and a sludge, and the metal ion, the alkaline substance, and the sulfur-containing substance are catalyst poisons, and the sludge is Attached to the surface of the catalyst, causing catalyst deactivation.

Summary of the invention

 The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and to provide a method for protecting a catalyst for preparing a lower fatty acid ester which can effectively prevent catalyst poisoning and keep the catalyst active for a long period of time.

Preparation of lower fatty acid esters by reacting C1~C4 fatty acids with C2~C5 olefins is an industrial acquisition in the prior art A preferred process for the lower fatty acid ester, wherein the molar ratio of the reactant C1 to C4 fatty acid to the C2 to C5 olefin (referred to as the acid to olefin ratio) is 0.7 to 3.0, preferably 0.8 to 2.5, because the acid to ene ratio is low. At 0.7, side reactions such as olefin polymerization will increase, and when the acid to olefin ratio is greater than 3.0, the amount of unreacted fatty acid will increase, which will increase the production load during product refining; C1~C4 fatty acids in the reactants The space velocity (feed space velocity) relative to the catalyst bed is 0.1 to 10.0 hr - preferably O S. Ohr - ¹ , if the feed space velocity is lower than 0.1 hr - ¹ , the reaction efficiency is low, and the side reaction is increased. On the contrary, if the space velocity is higher than lO.Ohr- ¹ , the reaction conversion rate will decrease; the reaction temperature is 30 to 150 ° C, preferably 65 to 135 ° C. When the temperature is lower than 30 ° C, the reaction is difficult to initiate, when the temperature is Above 150 ° C, side reactions such as olefin polymerization will increase; the reaction pressure is not particularly strict, but generally should be controlled at 0.8 to 2.0 MPa, preferably 0.8 to 1.8 MPa, the purpose is to At the reaction temperature, the reactant olefin can Preferably dissolved in a lower fatty acid. The reaction is carried out in a tubular fixed bed reactor in which industrial pure titanium containing a catalyst is used (a reactor which is preferably made of industrial pure titanium because of the organic carboxylic acid contained in the reaction raw material, which is easy to corrode the reaction equipment). The reaction is carried out in the liquid phase to prepare a lower fatty acid ester.

 The C1 to C4 fatty acid is a fatty acid having 1 to 4 carbon atoms, and may be formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid or acrylic acid, with acetic acid being preferred. The C2~C5 olefin is selected from one or more of ethylene, propylene, 1-butene, 2-butene, isobutylene, 1-pentene, 2-pentene, preferably propylene, 1-butene And / or 2-butene.

In the above reaction for preparing a lower fatty acid ester by reacting a C1~C4 fatty acid with a C2~C5 olefin, a catalyst (a catalyst installed in a tubular fixed bed reactor), a strongly acidic ion exchange resin, having a specific surface area is used. 20 to 50 m ² /g, a pore volume of 0.1 to 0.3 ml/g, and a particle size of 0.1 to 1.5 mm. The hydrocarbon material as a reaction raw material may contain metal ions, a basic substance, and a sulfur-containing substance, and these metal ions, a basic substance, and a sulfur-containing substance may cause deactivation of the strongly acidic ion exchange resin catalyst. When the olefin contained in the reaction raw material is a mixed hydrocarbon (for example, C4 is mixed), the mixed C4 further contains sludge which adheres to the surface of the catalyst to cause deactivation of the catalyst. The catalyst protection method of the present invention is a method for protecting the strongly acidic ion exchange resin catalyst, that is, pretreatment of the reaction raw material before entering the reactor to remove harmful impurities in the reaction raw material, thereby preventing catalyst poisoning. .

 In order to solve the above technical problems, the technical solution proposed by the present invention is a method for protecting a catalyst for preparing a lower fatty acid ester, which is characterized in that: when a lower fatty acid ester is prepared by using a C1~C4 fatty acid and a C2~C5 olefin, before the reaction First, the C2~C5 olefin is washed with water, dehydrated after washing with water, and then the C1~C4 fatty acid and the dehydrated olefin, or only one of them is subjected to a pretreatment apparatus equipped with a reaction aid. After the treatment, the above-mentioned treated raw materials C1 to C4 fatty acids and C2 to C5 olefins are fed to a reactor to prepare a lower fatty acid ester.

In the above technical solution, the hydrocarbon material containing C2~C5 olefin is introduced before the reaction raw material enters the reactor. By washing with water, a part of the toxin and the sludge of the above catalyst contained in the olefin can be washed away by water washing, thereby protecting the catalyst. In the case of water washing, the flow rate of the washing water should be controlled to a certain extent, and the mass flow ratio of the washing water to the hydrocarbon substance can be controlled to 0 to 10, preferably 0 to 3. In general, the mass flow ratio of the washing water to the hydrocarbon material is increased, and the water washing effect is good. However, when the mass flow ratio of the water washing water to the hydrocarbon material is greater than 10, the amount of water consumed is too large, and the operation is uneconomical. The washing water can also be placed in a washing tower, a washing tank or a washing tank. At this time, the mass flow rate of the washing water is 0, and the hydrocarbon substance is washed with water to achieve a water washing effect. Washed water is generally available with demineralized water.

 Since water will affect subsequent preparation reactions and catalysts, it is necessary to take the necessary measures to ensure that the water content of the hydrocarbons after washing is less. The dehydration method adopted by those skilled in the art can be used as an optional dewatering measure of the technical solution, such as the hydrocarbon intermediate tank after water washing or water washing, and the hydrocarbon substance is agglomerated by dehydration. The coalescing device of the filter element, and the like.

 Another pretreatment in the above technical solution is to remove the C1~C4 fatty acid and the dehydrated hydrocarbon material, or only the C1~C4 fatty acid through a pretreatment device equipped with a reaction aid to remove harmful impurities. The reaction aid in the preprocessor is an ion exchange resin, and the exchange capacity is not particularly controlled, but it is generally not less than 3 mmol/gH. Examples of alternative ion exchange resins are S54 ion exchange resin or D72 ion exchange resin. The temperature of the pre-processor can be 20~80 °C, the purpose of which is to fully absorb harmful impurities in the material under the condition of ensuring smooth flow, so that the diene and isobutylene in the hydrocarbon substance (such as mixed C4) and The organic carboxylic acid is reacted. There are three main purposes for the use of reaction auxiliaries: one is to remove the metal ions contained in the reaction raw materials; the other is to adsorb the nitrogen-containing substances and sulfur-containing substances in the reaction raw materials; the third is when the olefins used are mixed hydrocarbon substances ( For example, when C4 is mixed, the diene and isobutylene in the mixed hydrocarbon are first reacted with the organic carboxylic acid to avoid coking in the reactor.

 Compared with the prior art, the present invention has the advantages that: in the above reaction for preparing a lower fatty acid ester by reacting a C1~C4 fatty acid with a C2~C5 olefin, the harmful impurities contained in the reaction raw material before being introduced into the reactor have been removed. In addition, this prevents poisoning of the catalyst used in the subsequent preparation reaction. After the treatment by the method of the present invention, the catalyst has no deactivation phenomenon after being used for more than 6 months, and the reaction aid which acts as a catalyst protection has no metal ion permeation phenomenon, and the pressure difference before and after the reaction auxiliary bed layer changes. Not big.

detailed description

The invention is further illustrated by the following examples, but does not limit the invention. In the examples: the purity of acetic acid was 99.5%; the mass composition of mixed C4 was: 1-butene 4.72%, 2-butene 49.22% butane 46.01%, isobutylene 0.05%. Example 1:

Using a strong acidic ion exchange resin with a specific surface area of 30 m ² /g, a pore volume of 0.25 ml/g and a particle size of 1.0 mm as a catalyst, a total of 3.5 t of catalyst was charged into the split tubular reactor, the catalyst layer Both ends are packed with styrene-divinylbenzene polymer pellets.

The desalted water and the mixed C4 were passed to the water wash tower at a mass flow ratio of 5. The water-washed mixed C4 and acetic acid were passed to a pretreatment apparatus equipped with a D72 type ion exchange resin, and the outlet temperature of the preprocessor was 70 °C. The pretreated acetic acid and the mixed C4 were continuously fed into the tubular fixed bed reactor of the industrial pure titanium containing the catalyst from the bottom of the reactor, and the molar ratio of the acetic acid to the butene in the mixed C4 (acid to olefin ratio) was 1.3. The feed mode is liquid phase feed, the acetic acid feed space velocity is l.Ohf ¹ , the reaction pressure is 1.6 MPa, and the reaction temperature is 110 °C.

 The composition of the reaction product was sampled every 8 hr and analyzed by gas chromatography. Determination of sec-butyl acetate selectivity

98% or more. At the initial stage of the reaction, the concentration of Fe, Cr and Ni ions in the reaction medium after the pretreatment is less than 0.01 μ _§ / _§ , and the pressure difference between the reaction aid bed and the bed is less than 0.1 MPa. After 6 months of operation, the catalyst activity was stable, and the reaction conversion rate and selectivity did not change significantly. The concentration of Fe, Cr and Ni ions in the reaction medium after pre-processor was less than 0.01μ _§ / _§ , the pressure difference between the reaction aid bed and the bed Less than 0.1 MPa.

 Comparative Example 1:

A strongly acidic ion exchange resin having a specific surface area of 30 m ² /g, a pore volume of 0.25 ml/g, and a particle size of 1.0 mm was used as a catalyst. A total of 3.5 t of the catalyst was charged into the split tubular reactor, and both ends of the catalyst layer were packed with styrene-divinylbenzene polymerized beads.

The mixed C4 and acetic acid were passed to a pretreatment apparatus equipped with a D72 type ion exchange resin, and the outlet temperature of the preprocessor was 70 °C. The pretreated acetic acid and the mixed C4 were continuously fed into the reactor from the bottom of the reactor, and the molar ratio of the acetic acid to the butene in the mixed C4 (acid to olefin ratio) was 1.3, and the feed mode was liquid phase feed, acetic acid feed airspeed. It is l.Ohr- ¹ , the reaction pressure is 1.6 MPa, and the reaction temperature is 110 °C.

The composition of the reaction product was sampled every 8 hr and analyzed by gas chromatography. The selectivity of sec-butyl acetate was determined to be above 98%. At the initial stage of the reaction, the concentration of Fe, Cr and Ni ions in the reaction medium after the pretreatment is less than 0.01 μ _§ / _§ , and the pressure difference between the reaction aid bed and the bed is less than 0.1 MPa. After 1 month of operation, the pressure difference between the reaction aid bed and the bed began to increase slightly. After 4 months of operation, the Fe ion concentration in the reaction medium after the pre-processor reached 9.6 μ _§ / _§ , and the pressure difference between the reaction aid bed and the bed reached 0.4 MPa.

 Example 2:

Using a strong acidic ion exchange resin with a specific surface area of 30 m ² /g, a pore volume of 0.25 ml/g and a particle size of 1.0 mm Catalyst. A total of 3.5 t of catalyst was charged to the split tube reactor. Both ends of the catalyst layer are packed with styrene-divinylbenzene polymerized beads.

The desalted water and the mixed C4 were passed to the water wash tower at a mass flow ratio of 5. The acetic acid was passed to a pretreatment apparatus equipped with a D72 type ion exchange resin, and the outlet temperature of the preprocessor was 70 °C. After the pretreated acetic acid and the mixed C4 were mixed, the reactor was continuously fed from the bottom of the reactor, and the molar ratio of the acetic acid to the butene in the mixed C4 (acid to olefin ratio) was 1.3, and the feed mode was a liquid phase feed. The acetic acid feed space velocity was 1.0 Ohf ¹ , the reaction pressure was 1.6 MPa, and the reaction temperature was 110 °C.

The composition of the reaction product was sampled every 8 hr and analyzed by gas chromatography. The selectivity of sec-butyl acetate was determined to be above 98%. At the initial stage of the reaction, the concentration of Fe, Cr and Ni ions in the reaction medium after the pretreatment is less than 0.01 μ _§ / _§ , and the pressure difference between the reaction aid bed and the bed is less than 0.1 MPa. After 3 months of operation, the catalyst activity was stable, and the reaction conversion rate and selectivity did not change significantly. The concentration of Fe, Cr and Ni ions in the reaction medium after the pre-processor was less than 0.01μ _§ / _§ , the pressure difference between the reaction aid bed and the bed Less than 0.1 MPa.

 Example 3:

A strongly acidic ion exchange resin having a specific surface area of 30 m ² /g, a pore volume of 0.25 ml/g, and a particle size of 1.0 mm was used as a catalyst. A total of 3.5 t of catalyst was charged to the split tube reactor. Both ends of the catalyst layer are packed with styrene-divinylbenzene polymerized beads.

Mix C4 into a water wash tank containing desalinated water. The acetic acid was passed to a pretreatment apparatus equipped with a D72 type ion exchange resin, and the outlet temperature of the preprocessor was 70 °C. After the acetic acid and the mixed C4 were mixed, the reactor was continuously fed from the bottom of the reactor, and the molar ratio of the acetic acid to the butene in the mixed C4 (acid to olefin ratio) was 1.3, and the feed mode was a liquid phase feed. The acetic acid feed space velocity was 1.0 Ohf ¹ , the reaction pressure was 1.6 MPa, and the reaction temperature was 110 °C.

 The composition of the reaction product was sampled every 8 hr and analyzed by gas chromatography. The selectivity of sec-butyl acetate was determined to be above 98%. After 80 days of operation, the catalyst activity was stable, and the reaction conversion rate and selectivity did not change significantly. The concentration of Fe, Cr and Ni in the reaction medium after the pretreatment was less than 0.01 μg/g, and the pressure difference before and after the reaction aid bed was less than 0.1 MPa.

Claims

Rights request  A method for protecting a catalyst for preparing a lower fatty acid ester, characterized in that: before the reactant is introduced into the reactor, the C2-C5 olefin is washed with water to remove a part of the catalyst toxin in the olefin, and the reactant C1- The C4 fatty acid and the C2-C5 olefin or one of them is subjected to a pretreatment device containing a reaction aid to remove harmful impurities. 2. The method according to claim 1, wherein the reactor is a tubular fixed bed reactor made of industrial pure titanium containing a catalyst, wherein the catalyst is a strongly acidic ion exchange resin, and the specific surface area thereof is 20 to 50 m ² /g, a pore volume of 0.1 to 0.3 ml/g, and a particle size of 0.1 to 1.5 mm. O. l The feed space velocity of the C1~C4 fatty acid is O. l. The molar ratio of the C1 to C4 fatty acid to the C2 to C5 olefin is 0.7 to 3.0. lO.Ohr- ¹ , the reaction temperature is 30 to 150 ° C, and the reaction pressure is controlled at 0.8 to 2.0 MPa. The method according to claim 3, wherein the molar ratio of the C1 to C4 fatty acid to the C2 to C5 olefin in the reactant is 0.8 to 2.5, and the feed space velocity of the C1 to C4 fatty acid is O S. Ohr- ¹ , the reaction temperature is 65 to 135 ° C, and the reaction pressure is controlled at 0.8 to 1.8 MPa.  The method according to any one of claims 1 to 4, wherein the C1 to C4 fatty acid is formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid or acrylic acid.  The method according to any one of claims 1 to 4, wherein the C2 to C5 olefin is selected from the group consisting of ethylene, propylene, 1-butene, 2-butene, isobutylene, 1-pentene, 2 One or more of pentene.  The method according to any one of claims 1 to 4, characterized in that the mass flow ratio of the water washing water to the hydrocarbon substance is 0 to 10 when the water washing is performed.  8. The method according to claim 7, wherein the mass flow ratio of the water washing water to the hydrocarbon substance is 0 to 3 when the water washing is performed.  The method according to any one of claims 1 to 4, wherein the pretreatment unit has a reaction temperature of 20 to 80 ° C; the reaction auxiliary agent is an ion exchange resin, and the exchange capacity is not less than 3 mmol/gH.