CS214341B1 - Process and equipment for the production of acetaldehyde - Google Patents

Abstract

Acetaldehyde is produced by oxidation and/or dehydrogenation of ethanol on a silver catalyst at a temperature of 340 to 640 °C. The catalyst is mainly electrolytic silver or silver on a carrier, especially on zeolites. The catalyst may be further diluted with inert substances (the carrier itself, metal or glass beads, etc.). A mixture of ethanol vapor, water, air, and possibly also diethyl ether and acetals, as the main components, above the upper explosion limit, is fed to the catalyst, usually at a molar ratio of 0.5 to 2.5. In this case, the vapors leaving the reaction zone are rapidly cooled below a temperature of 340 °C (200 to 50 °C). They are then further cooled, condensed, acetaldehyde is isolated and unconverted ethanol and part of the admixtures are recirculated. The equipment consists of apparatus used for the production of formalin from methanol, supplemented by a separation system consisting of at least one pressure rectification column at a pressure of 0.1 - 0.3 MPa and one atmospheric column and the relevant tanks and intermediate tanks.

Description

1,214,341

The present invention relates to the production of acetaldehyde from petrochemical and / or fermenting ethanol containing, in addition to water, also admixtures of side-active substances, carried out on a readily technically readily available apparatus using air or oxygen-containing oxygen as the oxidizing agent ,

The known processes for the preparation of acetaldehyde from ethanol consist in dehydrogenation to form honey or in oxidation, with the exception of acetldehyde, water is formed. In the case of dehydrogenation processes, catalysts based on platinum, silver, medium and nickel are used, the most preferred catalysts based on media and its oxides with a variety of promoters and carriers (U.S. Pat. No. 1,977,750, as well as ethanol dehydration agents for ethylene; No. 2,861,106, NSR Pat. 1,044,791]. For the oxidation, platinum metals are actively employed, both in the form of metallic particles and supported on carriers / NSR pat. 1 913311]. However, the disadvantage is a lower selectivity for acetaldehyde. In doing so, the oxidation of ethanol to acetaldehyde

CH 3 GH 2 OH + 1/2 O 2 = CH 3 CHO + H 2 O + 169.7 kJ with oxygen can be catalyzed by similar catalysts as dehydrogenation, but silver and honey / German pat. 422,729 and 590,099 /, respectively. a combination of roasted net of these two metals (U.S. Pat. 1,956,440; 2,482,742; and 2,682,560]. Since the reaction proceeds at relatively high temperatures, dehydrogenation also takes place in the oxidation.

Thus, the exothermic oxidation (169.7 to 203.5 kJ / mol) can be complete or partially compensated by endothermic (-82.5 kJ / mol / dehydrogenation). However, while the temperature is not controlled, the controlled, low selectivity is achieved, since total oxidation to carbon monoxide, carbon dioxide and water, as well as oxidation to acetic acid and to the decomposition of acetaldehyde to methane and carbon monoxide, are achieved. In addition, ethyl acetate / Denisov E.T., Mickevich I.N., Agabekov V.E; Mechanizm židkofaznogo okislenija kislorodso-derzashchich soedinenij. Education "Science and Technology," Minsk 1975 /. In order to control the temperature, the external cooling of tubes containing catalyzing meshes / Swedish pat. 171,059 and USA-pat. 3 106 581 / or using such an air-to-ethanol ratio to justify exothermic and en-dope reactions / Faith WL, Keyes DB, Clark RL: Ihdútria Chemi-cals, p. 1 J. Wiley, New York 1950, '2 1957} Kirk-Othmer: Encyclopedia of Chemical Technology, 2nd ed., Volume 1, p. 77. J. Wiley, New York 1963; Encyclopedia of ChemicalProcessing and Design, red. McKetta J.J., Vol. 1, p. 114, Deckker, New York 1976]. Ethanol is used as a coating with conc. 50 to 95%, even very diluted, as obtained by direct hydration of ethylene / NSR Pat. 1,913,311). However, an obvious disadvantage is the energy consumption, because it is necessary to evaporate significant amounts of water together with ethanol.

According to the present invention, the process for the production of acetaldehyde by partial oxidation and / or ethanol dehydration on a silver catalyst at a temperature of 340 DEG-640 DEG C. is carried out on a silver catalyst, preferably consisting of electrolytically prepared crystalline silver and / or silver. on a support, preferably on a zeolite carrier, a vapor of ethanol, water and oxygen-containing gas, preferably air, optionally diethyl ether and monoethyl and diethyl acetal, are introduced as the main components, with a molar ratio of organic to oxygen containing of gas, preferably air, is above the upper explosion limit of 214 341 2, generally at a molar ratio of 0.5 to 2.5, wherein the crude product vapor from the reaction zone is rapidly cooled to below 340 ° C, preferably to a temperature of 200 to 50 ° C, then further cooled and condensed, preferably by trituration with an aqueous solution of ethanol, alone alone water and the acetaldehyde formed are separated, unconverted ethanol and with a portion of the water, acetals, optionally ether, are recirculated.

Apparatus for the production of acetaldehyde according to the invention, consisting of a saturator, a reactor, a condenser, columns, reservoirs, pumps, exchangers, conduits, fittings and dual-purpose devices is a flood of a formalin production plant consisting of a choke, a reactor and an absorption part for the formaldehyde is supplemented with a separating system of at least one pressure-regulating column to separate acetaldehyde from the high-boiling liquid particles and generally one atmospheric column, as well as feedstocks, intermediate and product.

The process according to the invention is feasible by using formaldehyde-producing devices, respectively. formalin by oxidation of methanol, which is technically and investment-friendly and easy to modify and modifies technologies, taking into account the kinetics, thermodynamics and physico-chemical properties of acetaldehyde and the aqueous solution of ethanol, usually with admixtures of acetaldehyde, diethyl ether and acetals, raw material. An advantage of the process according to the invention is the high selectivity of oxidation to acetaldehyde, the possibility of! The by-products used in the recirculation process are utilized after minor technical modifications and accessories to the equipment previously used for the production of formalin. Further, as a starting material, not only ethanol, but also direct ethanol hydration of ethylene, but also fermenting ethanol obtained from sulphite "liquors" is used, while its high concentration, which can be consumed under ethanol azeotrope concentration, is not required. steam for distillation, resp. rectification. There is no need for basic refining of ethanol. As the raw material can be ethanol, respectively. an aqueous ethanol solution comprising acetaldehyde, acetals, diethyl ether, ethyl acetate, acid acetic acid, vinylethyl ether, and the like as a by-product or admixture. Preferably, synthetic ethanol, obtained by direct ethylene hydration, may be used, distilled to 88-92% ethanol and containing byproducts of the hydration process, i.e., diethyl ether, acetaldehyde, acetals, crotonaldehyde, butnols and the like. ethanol does not fade, it is also partially oxidized and, if not provided with acetaldehyde, the products of their oxidation are removed from the process with waste gas or waste water from the separation column.

The silver catalyst may form a skeletal silver catalyst, e.g., Raney-silver, further electrolytically prepared crystalline silver, silver on a support (e.g. alpha-alumina, gamma-alumina, pumice, ceramic particles (generally prepared by impregnating inorganic carriers with silver salts or silver complexes, especially silver on synthetic or natural zeolites). In order to avoid overheating of the catalyst bed as well as its higher utilization, it is suitable, especially in the case of silver catalysts with a higher specific surface area (e.g. silver on zeolites / or even electrolytic silver, this is "diluted" by the addition of the carriers themselves, or metal or glass balls, rollers, etc., which, in addition, assists in a more uniform, better temperature distribution, if not heat removal. Λ

Typically, the catalyst is located in a low and wide layer reactor. The catalyst bed geometry is important. With a circular diameter, the ratio of height to width is 1: 6 to 1: 100. In such an arrangement, the heat exchange with the environment, and thus the reactor walls, is small so that the re-actuator operates virtually adiabatically. The reaction heat generated by the oxidation of ethanol is partially unbalanced by the simultaneous dehydrogenation of the ethanol and partially heats the reaction mixture. Therefore, it is advantageous to add water vapor / resp. use 1 dilute aqueous ethanol solution (which takes up part of the reaction temperature). Although the catalyst layer is low, there is a significant temperature gradient over it. The reactor reactor temperature mode must be controlled by the choice of feed composition / ethanol vapor / prime / water / air vapor /, inlet temperature prior to catalyst bed / 180 to 330 ° C) and loading the catalyst so that the temperature of the reaction mixture downstream of the catalyst bed is 340 to 640 ° C, preferably 440 to 560 ° C.

Oxygen-containing gas is diluted nitrogen with oxygen, most often air, possibly with ozone impurities. Clean air is needed, so it is usually pre-refined from sulfur dioxide, hydrogen sulfide, hydrogen chloride, nitrogen oxides, and other impurities that can be exhaled from industrial activity and are catalytic poisons. Refining can be done. by washing with a solution or by absorption or adsorption in a bed of solid material, the beads reacting with said acid gases.

The apparatus for producing acetaldehyde, the principal scheme of which is shown in the drawing, is made of stainless steel, respectively. of aluminum and its alloys, consisting of crimping devices and apparatus, such as choke 1, reactor 3, with a quenching device, washing machines, or a condenser 5, an extraction column 8, a pressure column 13 and a column 17, containers 20, 24, Salmarmatur, pumps, intermediate containers, measurement and control techniques. Further details of the manufacturing process as well as the device as well as the advantages apparent from the examples. f Example 1

A 7 cm of silver-plated catalyst is loaded into the tubular reactor heated in the jacket by an electric winding, having a diameter of 0.4 mm. After the conditions are stable, the reaction is carried out at an average temperature of 413 ° C with a mixture of air and ethanol with an air: ethanol molar ratio of 1.11: 1. The product is effectively cooled and the reaction gas is passed through a washing machine where residues are trapped in tetrahydrofuran acetaldehyde. At a time point of W / F = 2.73 (in ghole) 1 and a catalyst loading of 259.8 mol / cm @ 2, the ethanol version (used ethanol purity 99%) is synthetic, made by ethylene hydration / 50.7% and selectivity of acetaldehyde formation is 91.2%. In addition to ethanol and acetaldehyde, the reaction product also contains 2.4% acetaldehyde diethyl acetal and water (17.3% w / w). Example 2 o

7 cm of an electrolytic silver catalyst and 0.4 to 2 mm grains are charged into the tubular reactor. After stabilization of the oxidation conditions at 425 ° C, with mole. with an air to ethanol ratio of 1.19: 1 and the reaction mixture was analyzed by gas chromatography at a catalyst loading of 239.3 mol / ml. Ethanol conversion reaches 54.1%, acetaldehyde formation selectivity 90.6%. The reaction product also contains 4.4 wt. acetal and water (20.2% 214 341 4 w / w) also formed by the reaction. In addition to nitrogen, the gases contain small amounts of carbon dioxide, hydrogen and oxygen. Example 3

The stainless steel tubular reactor is charged with electroplated silver of a similar type to that used for the oxidation of methanol to formaldehyde. In the run-in period, ethanol was injected into the reactor at a concentration of 90.7% by weight, 0.1% acetaldehyde, 0.05% acetals and 0.2% by weight. diethyl ether, the remainder being water / mol. ratio of air to ethanol - 1.21: 1 /. The catalyst load is 244.5 mol.dm, h. After the temperature has stabilized at 409 ° C, the oxidation products condense by efficient cooling. According to the composition of the reaction product, an ethanol conversion of 59.1% is achieved. Acetaldehyde is produced with a selectivity of 91.5%. Another component of the reaction product is a mixture of acetaldehyde monoethyl acetal and acetaldehyde diethyl acetal (2.4% w / w and water / 25.3% w / w). Example 4

This example illustrates the effect of water on oxidation selectivity. The reaction is carried out by the apparatus described in Example 3, with an aqueous solution of ethanol being injected into the reactor at a concentration of 80.5% by weight. At a load of 277.1 mol / m @ 2 / mol. air: ethanol ratio: I, 07: 1, at an average temperature of 405 ° C, an ethanol conversion of 52.4% and a selectivity for acetaldehyde of 99.1% are obtained. The acetal content of the product is 0.8% by weight. and water 33.1 wt. Example 5

Using ethanol with conc. 69.7 wt. under experimentally similar conditions as in Example 2 / temperature 401 ° C, loading 271 mol.dm < -1 > air: ethanol ratio of 1.09: 1: ethanol conversion of 54.4% and acetaldehyde formation selectivity of 92.7% are achieved. The product also contains 3.5 wt. % acetal and 40.8 wt. water. Example 6

This example illustrates the effect of moles. air / oxygen / ethanol ratio for ethanol oxidation and dehydrogenation results.

The reaction is carried out under similar conditions as in Example 4 (temperature 402 ° C, load 247 mol.dm, 3 h-1) except that mole is used. poiper air to ethanol 0.563: 1.

Kelt

Chromatographic analysis of the product composition gave an ethanol conversion of 26.4% and a selectivity for acetaldehyde formation of 94.4%. The product contained 2.3 wt. % acetal, 2.5 wt. % diethyl ether and II, 2 wt. water. Example 7

A liquid composition of (% w / w): 74.3 ethanol is sprayed into the stainless steel reactor at 400 ° C; 8.8 water, 13.8 acetal / acetaldehyde monoethyl acetal and acetaldehyde diethyl acetal / 0.1 diethyl ether. Pri mol. air ratio: ethanol + acetal - 1.1: 1a by - 3 "1" 1 catalyst draw 248.5 mol.dm ^ at.h / time coordinate W / F - 2.81 ghmol / product containing 0 %, 8 wt. acetal / 94.2% conversion. The ethanol conversion is 53.6%. Example 8

Ethanol was injected into the stainless steel reactor at 400 ° C and contained 2.1 wt. 5,214,341 acetals and 10.2% wt. water. Pri mol. air / ethanol ratio of 1.12: 1 and a load of 252.1m.dm < tb > h / time co-ordinate W / F = 2.75 gmol / yield a product containing 1.1% w / w in the absence of acetal in the feed. Ethanol conversion is 51.2%. Example 9

The non-refined ethanol 92.5 wt.% Is sprayed into the stainless steel reactor at 520 ° C, containing small amounts of acetaldehyde, diethyl ether, higher alcohols (sec-butyl alcohol) and 100% water as admixtures.

The feed conditions are adjusted to a time coordinate of W / F = 1.1 g.h.mol 1 and mol. The ratio of air to ethanol was 1.1: 1. and selectivity of acetaldehyde formation 93.5%. Example 10

This example illustrates the possibility of decreasing the catalytic silver charge and replacing it with an inert filler with which the silver catalyst is mixed.

The procedure is similar to Example 2, with the difference that 5 g of electrolytic spray is mixed with 7? an inert filler such as natural zeolite - clinoptilolite and glassy beads of 0.5 mm diameter / weight of catalyst in Example 2 is 22.3 g /. After loading into the reactor, ethanol (90.7% w / w) and air were sprayed. The molar ratio of air to ethanol = 1.22: 1 and the time coordinate of 2.91 g.h.mol Χ. Under these conditions, an ethanol conversion of 65% and an acetaldehyde formation selectivity of 92% are achieved. Example 11 A mixture of ethanol and water prepared in a mixer, respectively. An aqueous raw ethanol solution coming directly from the ethanol production plant passes through the intermediate storage tank and enters through the conduit 27 into the steam-heated choke 1 and the ring ring, which also receives the regenerated ethanol with the addition of acetaldehyde, acetals and diethyl ether. Filtered air is fed to the bottom of the choke via line 26. The preheated mixture of air with water and organic vapors consisting of ethanol and admixture of acetaldehyde, acetals, diethyl ether and stopethylacetate enters the oxidation reactor 3 together with the quenching plant line 2. In reactor 3, electrolytic silver is deposited on the mesh as an oxidation catalyst while the reactor temperature is is maintained at 445 + 20 ° C. The molar ratio of air to ethanol is 1.19: 1, and the catalyst loading with ethanol is 240 mol / m 2 / hr. The oxide mixture is rapidly cooled to 150-100 ° C in the subsequent quenching portion of the reactor 3 heat exchanger 28, whereby the heat obtained is used to preheat the feedstocks in choke 1. Schladenazmes enters condenser 5 via line 4. through line 6 introduced by the ethanol solution. The liquid from the condenser 5 is fed through the lines 10 and 12 to the acetaldehyde column 13, in case of lower purity requirements via line 10 to column 17. Gas and steam from the apparatus. 5, they pass through line 7 to the extraction column 8, which is a scrubber line 9. The liquid phase passes through line 11 to an acetaldehyde column 13 operating at an overpressure of 0.11 to 0.17 MPa. The distillate-acetaldehyde is generally fed via line 16 through a condenser to and from the reservoir 24 for distribution or further use. Impoverished

Claims (2)

214 341 6 parts from the bottom of column 13 are passed through line 15 to column 17, which is optionally sprayed with fresh sulfur ethanol feed line 19. Distilled ethanol, optionally with acetyl acetyl acetate admixtures, is passed through line 18 to intermediate tray 20, with fresh feedstock feed line 27 The remainder of column 17 is passed through line 21 for recovery or separation of acid-acetic residues, acetals and esters, optionally a wastewater treatment plant and, as a rule, a portion of the effluent is passed through line 23 to the intermediate 20 via an admixture of organic by-products. A process for producing acetaldehyde by partial oxidation and / or dehydrogenation of ethanol on a silver catalyst at a temperature of 340 to 640 ° C, characterized in that it is a silver catalyst, preferably consisting of electrolytically prepared crystalline silver and / or silver on a support. , preferably on a zeolite carrier, a mixture of a vapor of ethanol, water and an oxygen-containing gas, preferably air, optionally diethyl ether and monoethyl and diethyl acetal, is supplied as the main components, with a molar ratio of organic substances to oxygen containing gas, preferably air. is above the upper explosion limit, generally a primary to a ratio of 0.5 to 2.5, wherein the crude product vapor from the reaction zone is cooled to below 340 ° C, preferably 200 to 50 ° C, then further cooled and condensed, preferably by spraying with an aqueous solution of ethanol, L is added by water alone and the acetaldehyde formed is optionally added also ethyl acetate and acetic acid are separated off, unconverted ethanol and with a portion of water, acetals, optionally ethers are recycled. 2. Apparatus for producing acetaldehyde according to claim 1, comprising a choke, a reactor, a condenser, columns, reservoirs, pumps, heat exchangers, conduits, fittings and auxiliary equipment, characterized in that the formalin-containing floodwater plant is made up of cheese The reactor (3) and the absorption part (5 and 8) for formaldehyde are supplemented with a separation system of at least one rectification column pressure (13) to separate the acetaldehyde from the high-boiling liquid portions and generally one atmosferic column (13). 17 / as well as raw material storage, intermediate product and product. 1 drawing