SA99200624B1 - A method for producing vinyl acetate - Google Patents

Abstract

IN PROCESS FOR THE PRODUCTION OF VINYL ACETATE IN WHICH ETHYLENE, ACETIC ACID AND OXYGEN-CONTAINING GAS ARE COMBINED AT ELEVETED TEMPERATURE IN THE PRESENCE OF A CATALYST MATERIAL TO PRODUCE (i) A PRODUCT MIXTURE COMPRISING VINYL ACETATE, (ii) ALIQUID BY-PRODUCT COMPRISING ACETIC ACID AND WATER AND (iii) A GESEOUS BY-PRODUCT COMPRISING CARBON DIOXIDE, THE LIQUID BY-PRODUCT IS SEPARATED FROM THE PRODUCT MIXTURE AND TREATED TO REDUCED THEWATER CONTENT THEREIN BEFORE BEING RECYCLED TO THE REACTOR SUCH THAT THE AMOUNT OF WATER ENTERING THE REACTOR COMPRISES LESS THAN 6WT400237C8REFERABLY LESS THAN 4 WTMORE, PREFERABLY LESS THAN 3 WTOF THE TOTAL OF ACETIC ACID AND WATER ENTERING THE REACTOR.

Description

‎Y —_ _— A method for producing vinyl acetate Full Description BACKGROUND This invention relates to a method for producing vinyl acetate from ethylene; Acetic acid and a gas containing oxygen in the presence of a catalyst. The methods of the lower layers (cradle layers) of fluids for the production of vinyl acetate from ethylene; 0 Acetic acid and a gas containing oxygen in the presence of a catalyst with a fluidized substrate known for example from international patents: 34 lacquer p (T = lacquer “Vellat” f = EP No. 1,854449-a shows a method for the manufacture of vinyl acetate In a fluidized bed reactor the method includes feeding ethylene and acetic acid to the fluidized bed reactor through one or more inlets; then feeding the oxygen-containing gas 0 to the aga fluidized bed reactor through another inlet at least one ; then the combination of oxygen-containing gases; and ethylene and acetic acid in the FBD reactor with contact with the catalyst in the FBD to allow ethylene; Acetic acid and oxygen react with each other to obtain vinyl acetate and extract vinyl from the fluid bed reactor. Vo The process of manufacturing vinyl acetate from ethylene acetic acid and oxygen is an exothermic reaction and it is necessary to have a way to cool the reactor with a fluid bed to get rid of the heat produced 0 and failure to cool can lead to loss of control of

Y _ -__ temp; There is a possibility that damages/inactivation of the catalyst may occur due to high temperatures. One of the means of cooling the system is to inject a liquid into the reaction mixture, where the liquid is introduced into the reactor for the purpose of removing heat from it by evaporating this liquid.

° It is possible to use water for this purpose; This is because water has a high latent heat of vaporization. Although the water effectively cools the reactor; That is, its use for this purpose works to negatively affect the resulting Ji acetate compound. Alternatively, liquid acetic acid can be used to cool the system. European Patent No. 847987 - A. Use of recycled acetic acid for this purpose. European Patent No. 867487 T=

0 also that there may be water in the recycled stream as a by-product of the reaction . general; It is very difficult and inconvenient to remove all of the water from the recycled acid stream. We have now found that the selectivity of the resulting vinyl acetate can be maintained at an acceptable level while maintaining the reaction system at the desired operating temperature Jal aan Take the recycled liquid to the reactor where the recycled stream contains an amount of 10 low - impressive tone; from water . General Description of the Invention Accordingly, this invention works on preparing a method for producing vinyl acetate induction. This mentioned method includes the following:

- og

0) Feeding ethylene; acetic acid and oxygen-containing gas into a reactor + bonding ethylene; acetic acid and oxygen-containing gas at elevated temperature to each other in the reactor in the presence of a catalyst (1) to obtain a resulting mixture comprising vinyl acetate (Y) a liquid by-product comprising eles acetic acid and (©) a gaseous by-product comprising 0 CO2© (b) separation of the liquid by-product from the product mixture© (c) treatment of the liquid by-product to reduce The amount of water in it; and (d) the recycling of the treated liquid by-product to the reactor, where the amount of water entering the reactor is less than “ # by weight; preferably less than 4 7 by weight; preferably less than 727 by weight, compared to the amount of acetic acid and water entering to

reactor

1 This invention solves the problems associated with previous inventions by maintaining the reaction temperature and obtaining a high selectivity (response) for the resulting vinyl acetate compound by introducing water into the reactor; at relatively low concentrations; It is convenient for water to be mixed with acetic acid in the re-passed liquid by-product. What is meant is that acetic acid enters the reactor, which means the total amount of acetic acid; Namely, the new acetic acid and acid

,. Recycled or passed vinegar ye

In this invention; Reducing the amount of water that enters the reactor reduces the negative effects of water on the reaction. With getting the cooling effect as is. This invention prepares a method for producing vinyl acetate from ethylene; A gas containing oxygen and acetic acid. It is possible that the ethylene is completely pure, or it is possible that it is mixed, Ye, with one or more nitrogens; methane; Ethan; carbon dioxide © hydrogen and/or concentrations

This is lower than the entities or alkanes ,© - ,© . It is possible that the percentage of ethylene in the reactor feed is 110 mol # at least. The oxygen-containing gas can be air or a gas that contains oxygen in a higher or lower percentage than air. It is appropriate for the gas to be oxygen diluted 0 with a masking diluent; as nitrogen; Argon or carbon dioxide. It is preferable that the gas containing oxygen is oxygen. The catalyst suitable for use in the method of this invention is a catalyst containing a group VIII metal on a support. It is preferred that the metal of the eighth group is palladium. Suitable sources of palladium include palladium chloride (ID) tetrachloride (I) sodium or potassium (Bl©118200 or KoPACly) palladium acetate; P11:00; palladium nitrate (ID) and sulfate Palladium (I) It is recommended that the palladium concentration be by weight, preferably greater than 1.9 7 by weight, in particular about 71 on the basis of the total weight of the catalyst. 701 by weight In addition to palladium 0 it is appropriate for the catalyst to include activator 1 and suitable activators include gold; copper and/or nickel. The metal of choice is gold chloride; suitable sources of gold include gold chloride; tetrachloride KAuCly gold acid “NaAuCly” HAuCl Dimethyl gold acetate Barium aceto gold or COA gold The preferred compound is NaAuCly The metal may be present in an amount ranging from 1.1 to 10 7 by weight in the final catalyst.

+ In addition to pallidium and tonic; The catalyst may include an activating cofactor, which is a metal selected from group I metals; the second group; lanthanides or selective metals; as cadm ¢ barium; potassium © sodium; iron ; manganese; nickel; Antimony and/or lanthanum and these metals are present in the final catalyst as salts such as acetate salts. And in general there will be potassium. The metal may be present in a concentration ranging from 11 to 715 ; Preferably from 1 to 75 by weight in the final catalyst. It is not uncommon for the catalyst to include an amount up to ve by weight of the activator aid. and if that process is carried out in a fixed bed reactor; It is preferable to have the concentration of the activator assistant from? to 11 7 by weight. and if that process is carried out in a fluidized bed reactor; a fifth 0 using liquid acetic acid; The detailed concentration of activator adjuvant is up to 716 by weight; Especially from 7.9 to 0.07 by weight where feed containing liquid acetic acid is used. And if the acid is used in the vapor phase; The activator adjuvant can be present in concentration up to 11 7# by weight. The catalyst is a fortified catalyst. Suitable supports include 0 porous silica; alumina; silica; alumina; Silica / titia 0 zirconia or carbon. It is preferable that the support be silica. It is appropriate for the pore size to range from 8.7 to 3.8 ml per kg of the support, and for that support to have a surface area ranging from ½ to 800 m" per g of the support, and for the apparent mass density to be from 1.7 to .1 # volume/mL For operation in a fluid substrate, the support will ideally have a particle size distribution such that at least 7 70 of 0 catalyst particles have a particle diameter of less than yoo microns. For a percentage of at least 7 80 and more preferably a percentage of at least 7980 particles.

-

The catalyst has a molecular diameter of less than 1,000 microns. It is preferable that the percentage does not exceed 1400%

The catalyst particles are less than ½ micron in diameter. It is important that the catalyst is prepared according to the method described in detail in European Patent No. T= IVY EOY. It is appropriate that the first stage of preparing the catalyst 0 is an Adee impregnation of the support material with a solution containing the required metal belonging of the eighth group and the activated metal in the form of suitable salts. Examples of these salts include ALE Called soluble derivatives. It is preferable that the impregnation solution be an aqueous solution, and that the volume of the used solution be an appropriate volume, corresponding to a ratio ranging from

0 to 7,001 of the stent size; preferably from 90 to 744 of the pore size.

0: After that, the impregnated support is dried at normal pressure or at low pressure and at a temperature ranging from normal temperature to cp Vou, preferably from 01 to 171 m before metal reduction. and to convert these materials to the metallic state; The impregnated support is treated with a reducing agent Jie Echelon; Hydrazine, formaldehyde, or hydrogen. if hydrogen is used; It is necessary to heat the catalyst to a temperature of 001 to

0 8006m to get the full downsampling.

And after implementing the previously described steps; The reducing catalyst is then washed with water

It dries. The dried carrier is then impregnated with the required amount of activator adjuvant

Then it is dried. Instead the wetted material is impregnated; reductive; Washed by activator assistant and then dried.

M - It is possible to change the method of preparing the catalyst to reach the level of performance of the catalyst to an optimal value on the basis of maximizing the value of the vinyl acetate product and on the basis of selectivity. The method of the present invention requires a step to reduce the water content in the liquid by-product stream and return this treated stream to the reactor.

° It is possible to reduce the water content in the liquid secondary stream in several ways. It is convenient to reduce the amount of water by passing the liquid secondary stream through a distillation column and then extracting the mixture consisting of acetic acid / water from the base of the distillation column. It is possible to choose the number of panels that can be added to the column according to the amount of water to be reduced. The acetic acid/water mixture may be withdrawn from the base of the distillation column either in liquid form or in vapor form.

01 The advantage of a distillate product that is a mixture of acetic acid/water and water as vapor is that the vapor contains a lower level of corrosive metals and/or other heavy compounds than the liquid product which has less catalyst poisoning. And with regard to the steam product; It can be further processed to reduce a larger amount of all content by partial condensation. in this embodiment; The total vapor of the column located at the base of the distillation column

1 “It is passed through a condenser, which condenses part of the incoming steam. Then the non-condensed steam is passed to the distillation column during the collection of the condensate and then recycled to the reactor. Partial ES is preferably present in the distillation column; But it can fall outside the channels. The advantage of using the partial condensation method is that a mixture of acetic acid / water is obtained from the distillation column, as this mixture contains a lower concentration of water than can be

0 Obtained by withdrawing or separating part of the steam from the distillation column and condensing it. Where is he to get

And the required concentration of water in the vapor product from the base of the distillation column by the last method (complete condensation of part of the column vapor), then the distillation column must work with a low concentration of water; Which can cause Jia difficulties in operation. Ideally, partial condensation can reduce the SL content in the secondary stream containing acid and water to a level of 75 by weight. Therefore, oo the water content in the acid stream entering the reactor will be less than that value. Lind can reduce the amount of water in the liquid secondary stream by chemical means; Jie Interact with Anhedrik Khalik. The recycled treated stream containing acid/water can be fed into the reactor by itself, independent of the acetic acid being fed. The recycled stream may be mixed with 0 fresh acetic acid before being introduced into the reactor. And his work is to introduce fresh acetic acid into the reactor (which contains a small amount of water) that is useful in reducing the amount of water that is fed into the reactor. Lad fresh acetic acid can be used in other parts of the method, including use as an absorbent. Both streams or one stream may be introduced into the reactor by several different methods including the grid of rods in the fluidized bed; Spray Columns 1 and Liquid / Gas Feed Nozzles It is preferable to introduce the stream or streams containing or containing acetic acid into the reactor through a live spray nozzle. A gas is used to assist in spraying the liquid. Alternatively, nozzles may be used to spray liquids only. It is possible to enter ethylene and gas containing oxygen through two separate entrances. Orifices suitable for use in this invention are shown in patent 186077/44.

11. - The process of preparing vinyl acetate using the method of this invention is ideally in contact with ethylene; Acetic acid and a gas containing oxygen with the catalyst at a temperature ranging from 001 to tee m, preferably from 1450 to 701 m, and a pressure ranging from 10 m Pa scale to XY m Pa scale ( from 1 to 010 barges); Preferably from 01 XT Pascal to 1.0 x 0 01 Pascal (1 to 15 barg). The method of this invention can be implemented in a fixed bed reactor or a fluidized bed reactor. It is preferable to use a fluidized bed catalyst in the fluidized bed reactor. The method of this invention will be clarified by referring to Figure 1 and the following experiments: 0 Brief explanation of the drawings Figure 1 is a schematic diagram of a fluidized bed reactor. Detailed description In the method of this invention, the diameter of the reactor is 1©, (ptt YAN) inch ( gay) with two feed inlets. The reactor is determined by (01) a tubular housing (VY) that has an outlet (V€) and two inlets First (V1) ve and second 0 (VA) reactor bad (01) comprises a plate of sintered crossbars enclosed in housing (OY) when operational; reactor (V0) is charged by 00 g of a fluidized substrate catalyst to form a fluidized bed dak A feed comprising ethylene, nitrogen, oxygen, © acid is introduced

— \ \ _ Evaporated water and evaporated water are left in the reactor (01) through a first inlet (V1). The oxygen, Ss, nitrogen is introduced into the reactor (01) through a second inlet (VA) in These experiments ¢ Then (ae) acetic acid and water are introduced into the reactor as a vapor and not as a liquid. The experiments show the effect of water on the reaction. It is expected that the introduction of acetic acid and water in the form of 0 liquids can affect the cooling according to the method of this invention. The experiments 1 , 7 , © are experiments in which the acetic acid stream contains less than + 7 by weight of water, and experiment A is not an experiment according to this invention as the stream contains Cel 77 oe lel Ap le preparation of the (Jalal) catalytic support ys The support used in the catalyst preparation processes was prepared by spray drying of a mixture of Silicaso 0100818 (Nolco Chemical Company) and Aerosil® (Degussa Chemical Company) and in the dried support; the percentage of 780% of The silica comes from the sol and 7 01 of the silica comes from the Aerosil The spray-dried microspheres were roasted in air at a temperature of Eh C for hours The particle size distribution of the Vo support was then used to prepare The catalyst is as follows: ‎Void

over 010 µm Y 4 to 0 µm TA over 4; Micron 7 It should be understood that the given particle size distribution is not specific and it is possible to make several changes in this distribution process, depending on the size of the reactor and the operating conditions. 0 Preparation of the al catalyst. A 4.4 #5 kg silica support was impregnated with a solution of NayPsClixH,0 (containing 1,000 gm of lithium) and NAuCLxH,0 (containing 4,060 gm of gold) in Distilled water in the initial wetness. The resulting mixture was thoroughly mixed; Then leave for an hour and then dry all night. A part of the impregnated material (YA kg) was slowly added to a solution of 1111 in distilled water (Ve), then the mixture was stirred with stirring for two periods, and then the mixture was filtered, then Jue was filtered by foe x liters of distilled water. The solid material was dried overnight, then the material was impregnated with he solution of potassium acetate (0 kg) primary Jb 0. The resulting mixture was mixed well and then left for an hour, then Cada all night. He was

The composition of the resulting catalyst is 1.17 7 by weight in lithium, 1.77 by weight in gold, 76.4 by weight in potassium acetate. Experiment 1

The fluidized bed reactor shown in Figure 1 was used in this method.

0 The reactor contains two feeding inlets. Oxygen and nitrogen are fed through the second inlet while ethylene ¢ nitrogen is fed; oxygen; Raw evaporated acetic acid mixed with recycled acetic acid and evaporated water (when used by the first inlet. The feed consists of ethylene) YY. g / Jaan ¢ (aclu acetic) Yoo g / hour ('oxygen) how much g/hour). Nitrogen is shown in Table 1. The reactor has been charged with 00g of agent

0 The fluidized bed catalyst was prepared as previously described. aly The acid stream contains water. The inlet gas flow has been regulated by mass flow controllers; The fluids were fed using a pump. The reactor pressure was maintained at /barg. The temperature of the reactor has been maintained at a temperature of 100 C, and then all lines that lead to 10 _ of the reactor have been thermally tracked, and their temperatures have been maintained at 16 C to prevent condensation of feed or products. The gaseous exhaust from the reactor was analyzed directly using a gas chromatograph of the type Chrompack Model CP9000 equipped with units observed for both FID and TCD. Ethylene and carbon dioxide have been separated on a Poraplot U column

_ p \ _ evaluated by TCD; Oxygen and nitrogen were separated on a molecular sieve column a evaluated by TCD; Vityl acetate, acetic acid and other by-products were then separated on capillary column 131710 and quantitatively evaluated by FID. The data was analyzed using the modified Excel computer program. The results are given in Table 1. Yaa 0, then repeat the method of experiment 1 using the water content YA by weight in the acid stream and the results are shown in Table 1. Experience ? Then repeat the method of experiment 1 using a water content of 8.1/wt in the acidic stream. 0 and the results are shown in Table 1. Experiment A The method of Experiment 1 was repeated using a water content of 797.4 wt in the acid stream. The results are shown in Table 1. The results shown in Table 1 show that the selectivity is improved as the concentration of cold) 1 decreases, especially if it reaches less than + # by weight. It should be noted that the maximum level of selectivity is obtained if the feeding system does not contain any amount of water. This is possible in the large production unit; However, it is not preferred because of the costs involved in removing all of the water

Sg \ — from the secondary stream 0. Commercial operating conditions therefore include water but the water concentration is maintained at a level of less than 6” 7 by weight in the acid stream. By using acetic acid containing less than +7 by weight water as a liquid, the reactor can be cooled. Table 1: The average weight of the experiment rate | Acetate quantity | The quantity of the Acetate quantity | JASE Water in | Entering the water Adal | dl redox | Ninyl eal acid (JA) Nutrition | nitrogen | g/h in | carbon | g/amount | dnd) * g of catalyst product ex el ee rel vel vel ver] 0 is calculated as the percentage of vinyl acetate (vinyl acetate + 0 + CO2)

Claims (1)

- 11 elements _ protection A method for the production of vinyl acetate. This mentioned method includes - 1 1 ¥ 0 feeding ethylene, acetic acid and oxygen-containing gas to a reactor; then the Y-ethylene union; Acetic acid is a gas containing oxygen at an elevated temperature in ; - the reactor in the presence of a catalyst to obtain (1) a product mixture comprising (Y) vinyl acetate “©” liquid by-product comprising acetic acid and water and (©) gaseous by-product 1 comprising carbon dioxide; (b) separation of the liquid by-product from the product mixture; A (c) treatment of the liquid by-product to reduce the amount of water in it; And 4 | (d) Recycle the treated liquid by-product back to the reactor where the amount of water entering the reactor is less than 6 7 by weight; preferably less than 74 by weight; 11 The best is less than 77 by weight of the total weight of acetic acid and water entering 1 reactor. 1? - a method according to claim 1; The water content of the liquid by-product Y is reduced by passing the liquid by-product through a distillation column and then removing a distillate containing less water from the distillation column. 1 * - A method according to claim oY in which the aforementioned distillate containing a JH SE Je A Z is removed 1? - lg method for claim 9; Wherein the complete vapor flow modulated Y at the base of the distillation column is passed through a partial condenser and then a distillate product containing the 1 © - method is collected according to the claim; ; Where the distillate has a water concentration of about 75 by weight. 1 1 - method according to the claim; ; or protection element ©; Where the partial condenser Y is located inside the distillation column. 1 7 - a method according to any of the previous elements; The water content (gs) of the secondary liquid is reduced by a chemical reaction. A) - method according to claim 7; Where the chemical reaction is Mg-7-acetic anhydride. 1 1 - A method according to any of the previous elements; where the by-product is mixed The treatment containing acetic acid / water and containing a lower concentration of water with ¥ fresh acetic acid before being introduced into the reactor. The eighth is preferably palladium and an activator to be chosen from the YF group, which consists of gold, copper, nickel, and mixtures thereof. Ham - 11 1 - A method according to any of the previous elements; Where the catalyst Y also includes an activation cofactor to be selected from the group consisting of group I metals + group II metals lanthanides and transition metals. 11 1 - a method according to any of the previous elements; The reactor includes Y reactor with a fluid bed.