MXPA98007618A - Preparation of acetaldeh - Google Patents

Abstract

A process for the preparation of acetaldehyde by the hydrogenation of ketene in the presence of a hydrogenation catalyst based on a transition metal is described.

Description

PREPARATION OF ACETALDEH1DO Field of the Invention This invention relates to a process for the preparation of acetaldehyde by the hydrogenation of ketene in the presence of a transition metal hydrogenation catalyst.

Background of the Invention Acetaldehyde is an important industrial chemical that has been used commercially in the manufacture of acetic acid, acetic anhydride, cellulose acetate, other acetate esters, vinyl acetate resins, synthetic pyridine derivatives, terephthalic acid, peracetic acid and pentaerythritol. Historically, some acetaldehyde has been associated with the production of acetic acid, but improvements in technology have resulted in the production of cheaper acetic acid from synthesis gas (a mixture of carbon monoxide and hydrogen). This development implies that acetaldehyde can be more economically produced from acetic acid than producing acetic acid from acetaldehyde if a technically viable route exists. An object of the present invention is to provide means for producing acetaldehyde efficiently from acetic acid. Acetaldehyde has been produced commercially by the reaction of ethanol with air at 480 ° C in the presence of a silver catalyst. This process has been replaced by Wacker's oxidation of ethylene which is more direct and efficient than the oxidation route of ethanol. Both the ethanol process and the Wacker process start with ethylene. Acetaldehyde has also been produced by the hydration of acetylene using mercury salts as a catalyst. It is clear that mercury management has both environmental and safety problems. The use of acetylene also implies safety concerns and the high cost of acetylene in relation to ethylene has made this process obsolete. Acetaldehyde can also be produced by reacting synthesis gas on a rhodium or silica catalyst at elevated temperature and pressure, but the selectivity of acetaldehyde is poor. Acetaldehyde has also been produced from the reaction of methanol with synthesis gas at elevated temperature and pressure and using a cobalt iodide catalyst with a group 15 promoter. Neither the process with rhodium catalyst nor in process with catalyst Cobalt iodide have been practiced commercially. While the Wacker process is the The preferred process on a commercial scale at present, this also has many ß ^ undesirable aspects. These include the special handling and safety problems associated with the reaction of ethylene with oxygen and the highly corrosive nature of aqueous reaction mixtures containing acidic chloride, which require very expensive building materials. Therefore, there is the The need for an acetaldehyde synthesis that constitutes an improvement over the known processes that exist. A potentially attractive means for synthesizing acetaldehyde is the hydrogenation of acetic acid. However, selective hydrogenation of acetic acid is difficult. The reaction is not favored thermodynamically and, therefore, high temperatures and excessive amounts of hydrogen are required. When these conditions are used, the selectivity is poor and the byproducts include acetone, carbon dioxide, formaldehyde, ethanol and methane. The acetaldehyde product that is initially produced is often more reactive than starting acetic acid, often resulting in an overreduction to ethanol. 25 Carr et al., In J. Chem Phys., 49, 846-852 (1968), teaches that the reaction of ketene with hydrogen atoms produces mainly methane and carbon monoxide. White et al., In J. Am. Chem. Soc. 1 1 1, 1 185-1 193 (1989), J. Phys. Chem., 92 41 1 1-41 (1988), J. Phys. Chem. ., 92 4120-4127 (1988), Surface Science, 183, 377-402 (1987) and Surface Science, 183, 403-426 (1987), describes the interaction of ketene with metal surfaces (Ru and Pt) as studied with spectroscopic techniques. Although acetaldehyde was absorbed in some cases, it decomposed or polymerized on the catalyst. No free acetaldehyde was produced. The products desorbed from these reactions were usually methane or higher hydrocarbons and carbon monoxide. Ponec et al., In J. Catal., 148, 261-269 (1994) and Red. Trav. Chim. Pays-Bas, 1 13, 426-430 (1994) describes a hydrogenation at high temperature (350 ° C) of acetic acid over reduced iron oxide catalysts. The addition of platinum improves the selectivity of acetaldehyde in some way. Ketene was identified as a by-product and possible intermediate. Under conditions where the selectivity to acetaldehyde is good (87-97%), the production of acetaldehyde is poor (6% or less) even when the reactions are carried out with a large excess of hydrogen (hydrogen: keten ratio = 60) :1 ). The operation in this mode is impractical from an industrial point of view due to the stream of diluted product, excessive recycling and the extreme temperature extremes required to isolate the product. The low selectivity of acetaldehyde was observed (16-40%) at high yields (13-40%) on a tin oxide catalyst. Byproducts of the reaction include acetone together with small amounts of methane and carbon dioxide. The platinum metal (one of the active metals of the present invention) by itself did not produce acetaldehyde in the hydrogenation reaction of acetic acid and the only byproducts observed were methane, water, carbon monoxide and carbon dioxide. A number of ketene-metal complexes have been described in the literature. Shapley et al., In J. Am. Chem. Soa, 108, 508-510 (1986), describes a ruthenium based ketene complex, which does not react with hydrogen. Miyashita et al., In Organometallícs, 4, 1463-1464 (1985) describes a complex of platinum-based ketene, which produces a mixture of acetaldehyde, ethanol and hydrocarbons when treated with hydrogen. Geoffroy, et al., In J. Am. Chem. Soc., 106, 4783-4789 (1984) describes a ketene complex based on an osmium agglomerate, which decomposes in the presence of hydrogen to form various other agglomerates. of osmium, acetic acid and acetaldehyde. None of these complex metal materials are catalytic in their reaction with hydrogen and only the complex described by Miyashita et al., Was prepared from ketene. The present invention provides efficient means for the production of acetaldehyde from ketene under very mild conditions. The process can be used in combination with known ketene manufacturing process to convert a variety of acetyl and related compounds such as acetic acid, acetic anhydride, diketene and acetone to acetaldehyde. The process of the present invention comprises the preparation of acetaldehyde by the steps of (1) contacting hydrogen and ketene gases with a catalyst that comprises a metal selected from the elements of group 9 and 10 (classification ^ IUPAC, Group 9 = Co, Rh and Ir, Group 10 = Ni, Pd and Pt) of the periodic table in a hydrogenation zone and (2) recovered Acetaldehyde from the hydrogenation zone.

Our novel process does not involve the formation of ketene-metal complexes of the type described in the literature mentioned hereinabove. 15 The process can be operated at temperatures in the range of from 0 and 250 ° C, although low temperatures give low reaction speeds and excessively high temperatures cause the accelerated degradation of ketene, which results in loss of production. Therefore, a more preferred range of temperatures is between 50 and 200 ° C. The temperature range that is most preferred is between 70 and 150 ° C. The catalytic hydrogenation process can be carried out at pressures ranging from 0.05 to 100 bars absolute (the pressures given here are absolute bars). Nevertheless, excessively high pressures increase the possibility of the formation of ketene polymerization products, while excessively low pressures cause low reaction rates and it is difficult to remove heat from the reaction. The process is preferably carried out at a pressure of from 0.1 to 20 bars, with the most preferred range being from 0.25 to 10 bars. Because ketene is normally generated and used at a pressure of one bar or less, the hydrogenation is most conveniently carried out at a pressure of one bar or less.

The reaction mixture may consist essentially of 100% ketene and hydrogen or a non-reactive (inert) diluent gas such as nitrogen, argon, helium or a light hydrocarbon may be added. For example, the presence of a non-reactive gas in the reaction mixture can help with the removal of heat from the reaction zone. When used, the inert diluents may comprise from up to 95 volume percent of the feed reagent. The use of excessive amounts of diluent gas reduces the reaction rate and makes the isolation of the acetaldehyde product more difficult. The presence of significant amounts of carbon monoxide can adversely affect the hydrogenation catalysts, especially the preferred palladium catalysts. Therefore, the reaction mixture should normally contain less than 1 volume percent carbon monoxide, preferably less than 1000 ppm carbon monoxide. The molar ratio of hydrogen to ketene can vary considerably, and can vary from 0.25: 1 to 10: 1. The hydrogen molar ratio: ketene preferably is in the range of 1: 1 to 8: 1, more preferably 2: 1 to 4: 1. The hydrogen: ketene molar ratios below 1: 1 limit the conversion of ketene and lower the reaction rate. Although the speed of the reaction increases with increasing ratios of hydrogen: ketene, excessive amounts of hydrogen increase the difficulty encountered in isolating the product. Also, the use of excessively high amounts of hydrogen in combination with a low spatial velocity can result in the production of some ethanol or ethyl acetate after most of the ketene has been consumed. Ethanol is not normally produced in the process of the invention, but ethyl acetate is perceptible at higher conversions. The metals that catalyze the hydrogenation of ketene to acetaldehyde according to the present invention can be found in what has been formally known as group VIII or group VlllA of the periodic table of the elements and, more specifically, what is currently called groups 9 and 10 of the periodic table of the elements. The catalyst is preferably selected from rhodium, platinum and, especially, palladium. The catalytic metals can be used in the form of unsupported metals or can be used in the form of a supported catalyst comprising the catalytic metal deposited in a catalyst support material. Examples of suitable support materials are alumina, carbon, titanium dioxide, silica, barium sulfate, barium carbonate and calcium carbonate. The Lindlar catalyst (palladium carbonate or lead-modified calcium) is also effective for the reaction but is not as selective as palladium on the other supports mentioned above. When a support is used, the metal loading can vary from 0.1 to 10 weight percent. Metal loads outside these ranges also perform the reaction but in general do not optimize the use of metal and support. It is often preferable to use an unsupported palladium catalyst, such as palladium sponge, because hydrogen treatment often restores the activity more effectively than what happens with a supported catalyst. It is also possible to employ catalytically active metals in the form of salts or complexes which are soluble in a liquid reaction medium in which the process can be carried out. Various means of operation can be used in the practice of the process of the invention. For example, the process can be used as a vapor phase, heterogeneous process, wherein a vapor (gas) comprising ketene, hydrogen and, optionally, a non-reactive diluent gas is fed to a reaction zone (hydrogenation) containing one or more beds of the catalysts described above. An alternative heterogeneous mode of operation consists of a vapor / liquid / solid phase process in which a feed gas comprising ketene, hydrogen and, optionally, a non-reactive diluent gas is fed to a reaction zone containing the catalyst as a suspension finally divided in a non-reactive liquid reaction medium such as a mineral oil. The product acetaldehyde can be removed from the reaction zone by gas desorption. In another embodiment of the vapor / liquid / solid phase operation method, a mixture of the fed gas and a non-reactive liquid can be fed to a hydrogenation zone where it is passed over the solid catalyst in an operation mode. bed with drip. Finally, the process can be carried out using a homogeneous catalyst solution consisting of a salt or complex of the catalytically effective metal dissolved in a liquid and non-reactive reaction medium (solvent) to which the gaseous mixture comprising ketene is fed. , Hydrogen and, optionally, a non-reactive diluent gas. This homogeneous operation is not preferred. The process of the invention can be operated as a batch, semi-continuous or continuous process. The most efficient operation of the hydrogenation process is achieved by working the process continuously in a mode of operation in gas phase 10 and in heterogeneous form. In this preferred method of operation the process * of the invention provides the continuous production of acetaldehyde by the steps of: (1) continuously feeding a vapor (gas) comprising ketene, hydrogen and, optionally, a non-reactive diluent gas to an area of Reaction (hydrogenation) containing one or more beds of the catalytically effective hydrogenation catalyst; and (2) continuously withdrawing a product gas comprising acetaldehyde from the reaction zone. The catalyst used in the heterogeneous continuous process which is preferred comprises supported and unsupported palladium catalysts. The gas space velocity per hour (GHSV - reagent volumes per catalyst volume per hour) of the ketene containing reagent and the feed diluent gases may vary from 10 to 100,000 using the preferred heterogeneous mode of operation. The GHSV preferably is in the range of 10 to 50,000 and, more preferably, is in the range of 1,000 to 20,000. In general, an increase in GHSV increases the reaction rate but decreases the conversion. The selection of the optimal GHSV depends on the physical form of the catalyst and the desired speed and conversion. The process of the present invention is further illustrated in the following examples. In the apparatus used in the examples, gas flows measured by four mass flow controllers model Tylan FC-260 were provided. Electric temperature control and monitoring were provided through a Dow Camile® control system interfaced with a Gateway 2000 model 486DX / 33 computer. Tygon® pipe was used for ketene free gases and ParMed® pipe was used for the gases containing ketene. The capacitors, the cyclone assembly, all the traps, reactors and desorbedores were built based on glass or quartz. Measured gases were fed through 4 gas lines L1 to L4 and each gas line was connected to a pressure release column containing water to prevent accidental overpressurization. Ketene was produced for laboratory use by the method described by Fisher et al., In J. Org. Chem., 18, 1055-1057 (1953) by the pyrolysis of acetic anhydride with minor modifications. Although pyrolysis of acetic acid is the preferred industrial route to ketene, it is generally not laboratory-scale practice. Any ketene source can be used as long as it is substantially free of inhibitors or catalyst poisons. Acetic anhydride was fed at 600 mL per hour using an infusion pump by Harvard Apparatus Model 22 syringe. The acetic anhydride was fed to the top of a vaporization / pyrolysis vertical tube of a length of 107 cm and a outer diameter (od) of 25 mm, together with 25 standard cubic centimeters per minute (SCCM) of helium. The vaporization / pyrolysis tube was drilled at a distance of 27 cm from the top and contained a quartz thermocouple cavity with an o.d. of 9 mm extending approximately two thirds of the length of the reactor from the top to the bottom. The portion of the vaporization / pyrolysis tube extending 22 cm above the perforation also contained quartz chips and was heated with controlled heating tape at 200 ° C. The lower section of the vaporization / pyrolysis tube was heated by a three-element Lindberg electric furnace controlled at 520 ° C. The mitigation condenser under the vaporization / pyrolysis tube was maintained at about -55 ° C by circulating cold methanol in a solid carbon dioxide / acetone bath. The mixture from the mitigation condenser passed through two identical cyclones that measured 16 mm of o.d. in the upper part and 80 mm from the upper part of the cyclone body to the lower part of the tapered section.

The cyclone inlet and outlet lines had an inner diameter (i.d.) of 2 mm and the liquid from the bottom of the cyclone assembly was drained into a 500 ml bottle. The gas displacement tube (10 mm o.d.) that connected the drain bottle to the cyclone assembly was bent to provide a ^^ 10 liquid seal. Steam in fog from the production cyclone assembly The ketene was passed through two mist traps maintained at 0 ° C to a three-way stopcock (SC1) through the ketene production line, in one position, SC1 was dewatering vapors containing ketene excess and that they came from the keten generation line to a water scrubber.

In another position, SC1 sent the vapors containing ketene to the ketene entrance line of a trap / vaporizer assembly. The trap / vaporizer assembly was a modified two-piece vacuum trap of 32 x 200 mm and had the lower portion of the trap narrowed to 19 mm from o.d. and extending an additional 100 mm. A gas inlet tube with an o.d. of 20 20 7 mm / i.d. of 2 mm, it extended along the outer body of the trap / vaporizer assembly and was connected to the base of the extended tube section. The gas inlet tube was connected to a measured nitrogen line that contained a stopcock (SC2). The ketene entry line was the normal 10 mm tube of o.d. that was in the standard design of the vacuum trap. The The output line of the ketene was the normal 10 mm side tube of o.d. found in the standard design of the vacuum trap. The trap / vaporizer assembly was charged with approximately 30 ml of liquid ketene by immersing the assembly in a -78 ° C bath with the SC2 closed and the SC1 open towards the trap / vaporizer assembly while the ketene generator was working.

During the loading procedure of the trap / vaporizer assembly with ketene, the outlet line of the trap / vaporizer assembly was isolated from the reactor and had access to the water scrubber through stopcocks SC3, SC4 and SC5. The stopcock SC3 connected to the outlet line of the trap / vaporizer assembly to the inlet line of the hydrogenation reactor or the reactor branch line. The SC4 three-way stopcock connected the reactor outlet and the bypass line to the line leading to the SC5 three-way stopcock. The stopcock SC5 directed the gas stream from the reactor or bypass line to a general-purpose water washer that was used to destroy ketene before venting or to an analytical washer containing circulating methanol. Helium -10 (normally calibrated at 50 SCCM) was always flowing through line L2 and mixed, with any material, which would drain through the trap / vaporizer assembly line during the procedure of ketene generation as during the hydrogenation process. Approximately 15 minutes of ketene generation operation was required to fill the tapered portion of the trap / vaporizer assembly. After the ketene trap / vaporizer was charged, it was isolated from the ketene generator by turning to SC1 to divert the vapors from the ketene generator line to the water scrubber. The stopcock SC2 was opened and nitrogen was measured (normal speed of 88 SCCM) through liquid ketene r-20 maintained at -78 ° C. These conditions evaporated the ketene from the trap / vaporizer at a rate of 1 mmol / minute (approximately 22.4 SCCM). Hydrogen (normal speed of 44.8 SCCM) was measured through L1 to the temperature controlled reactor. Details of the type of reactor used and the reaction conditions are provided in the specific examples. The reaction of The hydrogenation began by turning SC3 to feed the ketene / nitrogen gas mixture to the inlet line of the hydrogenation reactor to which hydrogen was also fed. Initially, the product vapor was vented to the water scrubber through SC4 and SC5. For the vapor phase reactions, a two-necked bottle, with a rounded bottom and 100 mL, was connected to the base of the reactor to trap any material that is not volatile at room temperature. To collect a sample dk for analysis, SC5 was rotated to send the product vapors to an analytical washer containing methanol (100 mL). The mixture of scrubber and methanol was circulated by a Masterflex peristaltic pump. Any unreacted ketene was converted to methyl acetate in the methanol scrubber. Acetaldehyde existed in 5 methanol as free acetaldehyde and acetaldehyde dimethylacetal. A condenser containing solid carbon dioxide and acetone was fixed to the top of the scrubber to avoid loss of material. After establishing a period of time, the product vapor stream was again diverted to the water scrubber through the SC5 and the methanol solution was drained from the scrubber base through the SC6 drain wrench and weight. The scrubber was then filled with fresh methanol for the subsequent sample. The products contained in the methanol scrubber solution were analyzed by gas chromatography using a Hewlett Packard Model 5890 gas chromatograph coupled with a capillary column FFAP of 30 mx 0.25 15 mm (0.25 micron film thickness) programmed at 35 ° C for 7 minutes, 15 ° C / minute at 220 ° C and holding at 220 ° C for 2 minutes using a flame ionization detector maintained at 280 ° C (injector temperature = 240 ° C). Mixtures were prepared for analysis by gas chromatography by adding 5 mL of a tetrahydrofuran solution containing an internal standard of 2% decane to a IJF 20 1 g sample, accurately weighed, of the methanol scrubber solution. The following definitions apply to specific examples: Gas Space Speed per Hour (GHSV) = gas volumes, that is, the total volume of ketene + hydrogen + diluent gases, per volume of catalyst per hour under reaction conditions. 25 Production Space Time (STY) = grams of acetaldehyde produced per liter of catalyst per hour. Conversion% (Conv) = 100 (mmoles of ketene reacted) / (mmoles of ketene fed). % of Cetena Accounting (Acct) = 100 (mmoles of ketene recovered + 30 mmoles of acetaldehyde produced) / (mmoles of ketene fed).

% Selectivity of Acetaldehyde (Select) = 100 mmoles of acetaldehyde produced) / (mmoles of reacted ketene). The GHSV is based on the total volume of all gases, that is ketene, hydrogen and diluent gases, fed to the hydrogenation reactor. The volume of any non-catalytic solid (operation in vapor phase) or liquid material (vapor / liquid / solid) added to the reactor as a diluent is not included in the GHSV or STY calculations. Accounting calculations were performed on the basis of the routine described above of the gas chromatography analysis performed and which could detect methyl acetate, acetaldehyde, dimethyl acetal and ethanol. Methane, carbon monoxide, diketene, oligomerization products of ketene, ethyl acetate and ethylene have been detected but not quantified as by-products, particularly in the early stages of evaluation of high activity catalysts. Other material losses resulted from the absorption of material within the porous pipe used to connect the various parts of the reaction apparatus.

EXAMPLE 1 This example illustrates the use of a catalyst of 5% palladium on barium sulfate, for the selective production of acetaldehyde from ketene and hydrogen using a steam heated reactor for temperature control. The glass reactor used in this example consisted of a tube 53 cm long by 25 mm o.d. adapted with a permanent thermocouple that extended from the base of the reactor. The central portion of the reactor tube was constructed with a condensing jacket that was in turn enclosed in a vacuum jacket to avoid heat loss. The length of the chamfered portions was 37 cm. The tube of 25 mm of o.d. it had notches 6 cm above the base of the jacket to support the catalyst bed. The reactor was loaded at a distance extending 25 mm above the notches with quartz wool covered with quartz splinters 8x16 mesh. It became a Physical mixture of 5% Pd on a barium sulfate powder (1.0015 g = 0.9 ml) and quartz splinters 8x16 mesh (50 ml), and this mixture was loaded on top of the quartz chips covering the quartz wool. The length of the catalyst bed was 15 cm. An additional charge of 4x8 mesh quartz chips was loaded onto the top of the catalyst bed to increase the height of the packed bed an additional 8 cm to the top of the condensation jacket. Hydrogen was fed to the reactor at 44.8 SCCM and an atmospheric pressure and the reactor was heated with steam at 97 ° C. The temperature along the entire length of the catalyst bed was constant up to 0.5 ° C. The catalyst was treated with hydrogen in this form for 22 hours and subsequently a mixture of ketene (1 mmol / minute), nitrogen (88 SCCM) and helium (50 SCCM) was added to the hydrogen stream entering the reactor. The temperature of the catalyst bed remained constant at 97-98 ° C during the hydrogenation reaction. Samples were taken throughout the day and at the end of the day ketene, nitrogen and helium were diverted from the reactor to the water scrubber, and the reactor was allowed to stand at 97-98 ° C with hydrogen flow at 10 ° C. SCCM throughout the night to restore catalyst activity. Cetena was allowed to evaporate from the trap / vaporizer assembly, which was then cleaned to prepare it for the next day's operation. The reactor was operated in this way for 4 days. The following samples were taken in the total time on the current (TOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst; and samples were collected in periods of 60 or 90 minutes: Sample TTOS. min 1-A 286-376 1-B 641-731 1-C 739-799 1-D 994-1084 1-E 1097-1157 1-F 1362-1452 f Treatments to the catalyst with hydrogen overnight were performed after TTOS was 376, 731 and 1084 minutes. Below is shown the space gas velocity per hour (GHSV) that was used and the production of space time (STY), conversion of ketene (Conv), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which the samples were collected 1 -A - 1 -F Sample GHSV STY Conv Acct Select 1-A 18600 1420 78 70 61 1-B 18600 1440 70 79 70 f 1-C 18600 1680 100 57 57 1-D 18600 1500 66 85 78 1-E 18600 1600 65 90 84 1-F 18600 1370 72 75 65 The differences in the results over time reflect the effects of the natural aging of the catalyst and the time elapsed following the treatments with hydrogen overnight.

? - EXAMPLE 2 This example illustrates the use of a Pd catalyst on barium carbonate 15 instead of Pd catalyst on barium sulfate which was used in example 1. A physical mixture of 5% Pd was prepared on carbonate powder barium (1.0075 g = 0.91 mL) and quartz chips as described in Example 1. As in Example 1, the same reactor, reactor loading sequence, hydrogen pretreatment, flow and temperature settings were used. The following 20 samples were taken in the total time over the current (TTOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst, and the samples were collected over periods of 60 or 90 minutes: Shows TTOS. min 2-A 286-376 2-B 380-440 2-C 635-725 2-D 729-7894 2-E 984-10747 2-F 1350-1440 The catalyst treatments with hydrogen overnight were performed after TTOS was 376, 725 and 1074 minutes. Below is shown the space gas velocity per hour (GHSV) that was used and the production of space time (STY), conversion of ketene (Conv), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which the samples were collected 2-A-2-F Sample GHSV STY Conv Acct Select 2-A 18400 1390 67 81 72 2-B 18400 1550 62 92 87 2-C 18400 1230 57 85 74 2-D 18400 1480 56 95 92 2-E 18400 1310 53 92 86 2-F 18400 1240 56 86 76 The differences in the results over a period of time reflect the effects of the natural aging of the catalyst and the time elapsed following the hydrogen treatments throughout the night.

EXAMPLE 3 This example illustrates the use of a Pd catalyst on calcium carbonate powder. A physical mixture of 5% Pd was prepared over calcium carbonate powder (1.0028 g = 1.4 mL) and quartz chips as described in Example 1. As in Example 1 the same reactor was used, the loading sequence of reactor, pretreatment with hydrogen, flow and temperature adjustments. The following samples were taken in the total time on the current (TTOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst, and the samples were collected over periods of 60 or 90 minutes: Shows TTOS. min 3-A 195-285 3-B 573-663 ß 3-C 955-1045 3-D 1146-1206 3-E 1411-1501 The treatments with the catalyst with hydrogen during the whole night were performed after the TTOS times were 380, 758 and 1140 minutes. Below is shown the space gas velocity per hour (GHSV) that was used and the production of space time (STY), conversion of ketene (Conv), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which the samples were collected 3-A - 3-E 15 Sample GHSV STY Conv Acct Select 3-A 12000 1210 82 81 78 3-B 12000 1070 85 72 67 3-C 12000 1020 82 71 65 3-D 12000 1220 100 65 65 3-E 12000 1080 100 57 57 f The differences in the results achieved over the time periods reflect the effects of natural aging of the catalyst and the time elapsed after the hydrogen treatments throughout the night .

EXAMPLE 4 This example illustrates the use of a Pb catalyst modified with Pb on calcium carbonate (Lindlar catalyst) and can be compared with Example 3 to illustrate the effect of lead modification on catalyst performance. A physical mixture was prepared from 5% lead-modified Pd on calcium carbonate powder (1.0048 g = 1.2 mL) and quartz chips as described in Example 1. As in Example 1, used the same reactor, reactor loading sequence, hydrogen pretreatment, flow and temperature adjustments. The following samples were taken in the total time on the current (TTOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst, and the samples were collected over periods of 60 or 90 minutes: Sample TTOS, min 4-A 188-278 4-B 561 -651 4-C 929-1019 4-D 1122-1182 4-E 1382-1472 The catalyst treatments with hydrogen overnight were performed after the TTOS times were 373, 746 and 11 14 minutes. Below is shown the space gas velocity per hour (GHSV) that was used and the production of space time (STY), conversion of ketene (Conv), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which the samples 4-A-4-E were collected.

F Sample GHSV STY Conv Acct Select 4-A 13900 760 77 57 45 4-B 13900 740 71 62 47 4-C 13900 630 66 63 44 4-D 13900 680 100 31 31 4-E 13900 605 62 65 44 The differences in the results achieved over the time periods reflect the effects of the natural aging of the catalyst and the time elapsed following the treatments with hydrogen throughout the night. F EXAMPLE 5 This example illustrates the use of a Pd catalyst on alumina in a prolonged experiment in which the total time over current exceeded 100 hours. A physical mixture was prepared from 1% Pd on alumina, granules of 2 mm in size (5.0186 g = 6 ml) and quartz chips as described in Example 1. As in Example 1 the same reactor, reactor loading sequence, hydrogen pretreatment and reaction conditions were used. . Although the reaction conditions were modified during this long experiment (refer to Examples 6, 7 and 8 below), the data presented in this example were obtained under the flow and temperature settings reported in Example 1. The following samples were taken in the total time over current (TTOS) indicated in minutes when both hydrogen and ketene were in contact with the catalyst, and the samples were collected over periods of 60 or 90 minutes: 20 F Sample TTOS. min 5-A 260-350 5-B 641-731 5-C 1051-1141 5-D 2363-2423 5-E 2618-2708 5-F 6762-6822 The catalyst treatments with hydrogen overnight were performed after the TTOS times were 350, 731, 1 141, 1563, 1971, 2350, 2708, 31 16, 3514, 3918, 431 1, 4702, 5086, 5464, 5915, 6294 and 6754 minutes. Below is shown the space gas velocity per hour (GHSV) that was used and the production of space time (STY), conversion of ketene (Conv), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which the samples 5-A-5-F were collected. 10 Sample GHSV STY Conv Acct Select 5-A 2800 190 59 84 72 5-B 2800 150 50 84 69 5-C 2790 120 43 84 62 5-D 2790 140 34 96 89 5-E 2790 110 27 99 96 5-F 2790 90 25 94 78 The differences in performance over time reflect the effects of natural aging of the catalyst and the time elapsed following the treatments with hydrogen throughout the night. EXAMPLE 6 This example illustrates the effect of the reaction temperature on the acetaldehyde production rate using the Pd catalyst on alumina and the procedure described in Example 5. The steam heating system was replaced with a circulating water bath with controlled temperature for information obtained below 90 ° C. The data was obtained at a point where the history of the catalyst where the changes in activity due to catalyst deactivation were minimal. The flow adjustments were the same as those used in the previous examples. The following examples were taken in the total time on the current (TTOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst, and the samples were collected over periods of 60 or 90 minutes. The temperature values given below are the temperatures in ° C of the catalyst bed.

Sample TTOS, min Temperature 6-A 5374-5464 98.0 6-B 5730-5820 88.4 6-C 6204-6294 77 8 6-D 5550-5640 69.8 6-E 5986-6076 59.3 6-F 6394-6484 49.4 The catalyst treatments with hydrogen overnight were performed as in Example 5. The gas velocity space per hour (GHSV) that was used and the space time production (STY), ketene conversion (Conv. ), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which the samples were collected. 6-A - 6-F Sample GHSV STY Conv Acct Select 6-A 2790 91 32 89 65 6-B 2720 62 34 80 41 6-C 2640 41 30 80 31 6-D 2580 41 28 82 33 ß-E 2500 24 13 92 41 6-F 2420 15 12 91 29 EXAMPLE 7 This example illustrates the effect of altering the amounts of hydrogen and ketene on the acetaldehyde production rate using the process and the Pd catalyst on alumina described in Example 5. The data was obtained at a point where the history of the catalyst where changes in activity due to deactivation of the catalyst were minimal. The catalyst temperature was maintained at 98 ° C and the velocity space remained essentially constant by changing the amount of helium diluent when other gas flows were changed. A different velocity space was used for the study of varying levels of hydrogen than that used for the study of varying levels of ketene. A more dilute gas stream was used when the ketene levels were varied.

The following samples were taken in the total time on the current (TTOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst, and the samples were collected over periods of 60 or 90 minutes. The values given for the feed speeds of ketene (speed of the ketene feed) and hydrogen (speed of the feed of hydrogen) are mmoles per minute.

Vel Alim of Vel Alim Shows TTOS, min. Hydrogen ketene 7-A 3703-3793 1.0 0.5 7-B 3583-3673 1.0 1.0 7-C 1563-1473 1.0 2.0 7-D 1215-1305 1.0 3.0 7-E 1348-1438 1.0 4.0 7-F 3986-4076 0.5 4.0 7-G 4382-4472 1.0 4.0 7-H 4771-4861 1.5 4.0 7-1 5249-5339 2.0 4.0 The catalyst treatments with hydrogen overnight were performed as in Example 5. The gas velocity space per hour (GHSV) that was used and the space time production (STY), ketene conversion (Conv. ), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which samples 7-A-7-I were collected.

Sample GHSV STY Conv Acct Select 7-A 2800 59 23 91 59 7-B 2800 77 37 80 47 7-C 2800 128 47 83 62 7-D 2800 165 51 87 74 7-E 2800 172 49 90 80 7-F 4300 77 46 90 77 7-G 4300 110 36 89 70 7-H 4300 109 33 84 50 7-I 4300 131 34 81 43 EXAMPLE 8 # This example illustrates the effect of altering the gas velocity space per hour (GHSV) of hydrogen and ketene fed on the acetaldehyde production rate, using the process and catalyst of Pd on alumina described in Example 5. The data was obtained at a point in the history of the catalyst where changes in activity due to deactivation of the catalyst were minimal. The temperature of the catalyst was maintained at 98 ° C and the gas proportions were the same as those used in the Examples 1 and 5. The following samples were taken in the total time over the current? Or (TTOS) indicated in minutes in which both hydrogen and ketene were in 'z? - contact with the catalyst and the samples were collected over periods of 60 or 90 minutes.

Shows TTOS. min 8-A 1631-1721 8-B 1473-1563 8-C 1756-1846 8-D 1975-2035 The catalyst treatments with hydrogen overnight were performed as in Example 5. The gas velocity space per hour (GHSV) that was used and the space time production (STY), ketene conversion ( Conv), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time on the which samples 8-A-8-D were collected.

Sample GHSV STY Conv Acct Select 8-A 1400 106 49 99 99 8-B 2800 128 47 82 62 8-C 3700 153 37 87 63 8-D 4910 185 34 87 62 EXAMPLE 9 This example illustrates the use of a Pd catalyst on carbon. A physical mixture of 5% Pd was prepared on carbon powder (1.0026 g = 2.6 mL) and quartz chips as described in Example 1. As in Example 1, the same reactor, reactor loading sequence, was used. pretreatment with hydrogen, flow and temperature adjustments. The following samples were taken in the total time on the current (TTOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst and the samples were collected over periods of 60 or 90 minutes: 10 f ^^^ * Shows TTOS. min 9-A 336-426 9-B 435-495 9-C 710-800 9-D 1294-1384 9-E 1484-1574 The catalyst treatments with hydrogen overnight were performed after the TTOS times were 426, 800 and 1214 minutes. Below is shown the gas velocity space per hour (GHSV) that was used and the space time production (STY), ketene conversion (Conv), accounting # (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which samples 9-A-9-E were collected.

Sample GHSV STY Conv Acct Select 9-A 6420 585 100 58 58 9-B 6420 663 100 65 65 9-C 6420 607 100 60 60 9-D 6420 589 100 58 58 9-E 6420 552 81 74 67 The differences in the performance over time reflect the effects of # natural aging of the catalyst and the time elapsed following the treatments with hydrogen throughout the night.

EXAMPLE 10 This example illustrates the use of a Pd catalyst on titanium dioxide. A physical mixture of 1% Pd was prepared on titanium dioxide powder (5,001 g = 6 mL) and quartz chips as described in Example 1. As in Example 1, the same reactor was used, the loading sequence of reactor, pretreatment with hydrogen, flow and temperature adjustments. The following samples were taken in the total time fl oW over the current (TTOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst, and the samples were collected over periods of 60 or 90 minutes: Shows TTOS. min 10-A 262-352 10-B 615-705 10-C 775-865 10-D 1318-1408 15 Treatments to the catalyst with hydrogen overnight # performed after TTOS times were 352, 705 and 1055 minutes. Below is shown the space velocity of gas per hour (GHSV) that was used and the production of space time (STY), conversion of ketene (Conv), accounting 20 (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which samples 10-A-10-D were collected.

Sample GHSV STY Conv Acct Sele 10-A 2800 108 36 89 68 10-B 2800 1 12 42 83 61 10-C 2800 100 61 61 37 10-D 2800 108 49 76 51 EXAMPLE 11 This example illustrates the use of a catalyst Pd in bulk and free of supports. A physical mixture was prepared from palladium sponge powder (1.005 g = 0.4 mL) and quartz chips as described in Example 1. As in Example 1 the same reactor was used, reactor charge sequence, pretreatment with hydrogen, flow and temperature settings. The following samples were taken in the total time on the current (TTOS) indicated in minutes in which both hydrogen and ketene were in contact with the catalyst, and the samples were collected over periods of 60 or 90 minutes: Sample TTOS, min 11 -A 429-519 1 1 -B 784-874 11-C 1138-1228 Hydrogen overnight treatments were carried out after the TTOS times were 354, 709 and 1064 minutes. Below is shown the space gas velocity per hour (GHSV) that was used and the production of space time (STY), conversion of ketene (Conv), accounting (Acct) of ketene and selectivity of acetaldehyde (Select) reached for each period of the reaction time over which the samples 11A-11C were collected.

Sample GHSV STY Conv Acct Select 1 1-A 41800 1310 24 96 84 1 1-B 41800 1290 24 95 80 1 1-C 41800 1310 20 100 100 EXAMPLE 12 This example illustrates the use of an Rh catalyst on alumina. The reactor tube used in this example was a 25 mm quartz tube of o.d. containing an interior thermocouple of quartz. The reactor had notches near the base. The reactor was charged with quartz chips measuring 12 cm in height from the notches. The catalyst, 0.5% Rh, was added on 3 mm alumina granules (5.016 g = 5.1 mL). An additional layer of quartz slivers was placed measuring 6 cm high on top of the catalyst bed. The reactor was placed in a single-element electric furnace and had a heating zone 23 cm long, such that the catalyst was placed in the center of the heating zone of the furnace. The catalyst was treated overnight with hydrogen (44.8 SCCM) at 200 ° C and subsequently allowed to cool to room temperature. Ketene (1 mmol / minute), helium (25 SCCM), nitrogen (88 SCCM) and hydrogen (44.8 SCCM) were added to the reactor and the furnace was ignited. The temperature of the catalyst bed increased from room temperature to 30 ° C with the space velocity of gas per hour being 2350 and the product in steam was sampled over a period of 90 minutes. The space-time production of acetaldehyde was 56 to 1 1% ketene conversion. Accounting for ketene and the selectivity of acetaldehyde were 100% and 97%, respectively. The activity of this catalyst for the production of acetaldehyde decreased to zero during the next hour as the temperature of the catalytic bed dropped to 24 ° C. The catalyst once again became active for the production of acetaldehyde when the furnace was calibrated at 100 ° C with a velocity space of 3250 and the temperature 20 of the catalytic bed at 146 ° C. The sample was collected over a period of 90 minutes and the spacetime production of acetaldehyde was 31 to a ketene conversion of 73%. The ketene accounting and the acetaldehyde selectivity were 33% and 8%, respectively.

EXAMPLE 13 This example illustrates the use of a Pt catalyst on alumina. The procedure and the reactor used in Example 12 were repeated, except that the Rh-on-alumina catalyst was replaced with 0.5% Pt on 3-mm alumina granules (5.0 g = 6.1 mL). The pretreatment with hydrogen and the reaction conditions used in Example 12 were also repeated. Acetaldehyde was not detected with the oven at room temperature. The oven was then adjusted to 100 ° C. The temperature of the catalytic bed increased to 148 ° C with a velocity space of 2700. The sample was collected over a period of 90 minutes and the spacetime production of acetaldehyde was 45 at a 68% conversion of ketene. The accounting for ketene and the selectivity of acetaldehyde were 42% and 15%, respectively.

EXAMPLE 14 This example illustrates the process of the invention operated in a vapor / liquid / solid mode using a reactor with gas desorption. The reaction vessel consisted of a glass, cylindrical and reaction flask, which had a flanged and ground joint top, gas dispersion stirrer and a ground head flanged reactor head equipped with a precision stirring bearing, thermocouple and gas outlet hole. The dimensions of the cylindrical reaction bottle were 5 cm in internal diameter by 28 cm in height. Two bands of 5 notches equally spaced and 5 cm high were located with the lower part of the bands at 6 and 15 cm above the base of the reactor. The notched bands acted as baffles and the notches of the two bands were staggered. The gas dispersion agitator was a hollow glass tube of 1 cm OD, sealed at the top and open at the bottom and had two bands of stirring blades located at the bottom of the stirrer and 1 1 cm above the bottom. Each of the bands of the agitation sheets contained four sheets of 1.5 x 1.5 cm, and the sheets of the two bands were staggered. The agitator had a hole in each side that acted as an inlet hole for the reaction gases that were introduced through a side arm onto the precision agitator bearing. The reactor was loaded with 5% Pd on barium carbonate powder (1.0480 g = 0.94 mL) and dodecane (300 mL). The assembled reactor was heated at 95 ° C in a steam bath overnight with stirring and with hydrogen (44.8 SCCM) bubbling through the slurry. Ketene (1 mmol / minute), helium (50 SCCM) and nitrogen (88 SCCM) were added to the existing hydrogen stream. The products were analyzed from the methanol washing solutions as in the preceding examples, with the product in steam leaving the exit orifice of the reactor with gas desorption and coming into contact with the desorbing solution. The temperature of the slurry remained at 95 ° C with a space velocity of 17600 (based on the volume of catalyst), the sample was collected over a period of 60 minutes and the acetaldehyde space-time production was 365 (based on the volume of the catalyst) at 21% conversion of ketene. The accounting for ketene and the selectivity of acetaldehyde were 92% and 62%, respectively.

The invention has been described in detail and with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications may be made within the spirit and scope of the invention.

Claims (13)

1. Novelty of the Invention 1. A process for the preparation of acetaldehyde by the steps comprising (1) contacting hydrogen and ketene gases with a catalyst comprising a metal selected from the elements of Groups 9 and I0 of the periodic table in a hydrogenation zone, and (2) recovering acetaldehyde from the hydrogenation zone.
2. 2. The process according to claim 1, wherein the contact is carried out at a temperature of 50 to 200 ° C and a pressure of 0.1 to 20 absolute bars.
3. 3. The process according to claim 2, wherein a non-reactive diluent gas is also fed to the hydrogenation zone.
4. 4. The process according to claim 2, wherein the catalyst is a supported or unsupported palladium catalyst.
5. 5. The process according to claim 4, wherein the temperature is from 70 to 150 ° C and the pressure is from 0.25 to 10 absolute bars. 6. A continuous process for the production of acetaldehyde, which comprises the steps of: (1) continuously feeding a gas comprising ketene, hydrogen and, optionally, a non-reactive diluent gas to a zone of 25 hydrogenation containing one or more beds of a catalytically effective hydrogenation catalyst, comprising a metal selected from the elements of Groups 9 and 10 of the periodic table; and (2) continuously removing a product gas comprising acetaldehyde from the reaction zone.
6. Jft
7. 7. The continuous process according to claim 6, wherein the hydrogenation zone is at a temperature of 50 ° C to 200 ° C and a pressure of 0.1 to 20 bar absolute.
8. 8. The continuous process according to claim 7, wherein the catalyst is a supported or unsupported palladium catalyst.
9. 9. The continuous process according to claim 7, wherein the hydrogenation zone is at a temperature of 70 ° C to 150 ° C and an ion pressure of 0.25 to 10 bar absolute, and the catalyst is a supported palladium catalyst. '^^^ or not supported.
10. 10. The continuous process according to claim 6, wherein the step (1) is carried out in the presence of a non-reactive liquid.
11. 11. The continuous process according to claim 10, wherein the hydrogenation zone is at a temperature of 50 ° C to 200 ° C and a pressure of 0.1 to 20 absolute bars.
12. # 12. The continuous process according to claim 11, wherein the catalyst is a supported or unsupported palladium catalyst.
13. 13. The continuous process according to claim 11, wherein the hydrogenation zone is at a temperature of 70 ° C to 150 ° C, the pressure is from 0.25 to 10 bar absolute, and the catalyst is a supported palladium catalyst or not supported.