WO2020190550A1

WO2020190550A1 - Catalyst and process for vapor-phase aldehyde hydrogenation

Info

Publication number: WO2020190550A1
Application number: PCT/US2020/021646
Authority: WO
Inventors: Kathleen Barnes; Krishna M. JANMANCHI; David Gordon Barton; Howard VANCE JR.; Denise A. ANAYA; Vladimir V. PUSHKAREV; Jin Yang; Michael C. Becker
Original assignee: Dow Technology Investments Llc; Dow Silicones Corporation
Priority date: 2019-03-19
Filing date: 2020-03-09
Publication date: 2020-09-24

Abstract

Embodiments of the present invention are directed to processes for vapor-phase aldehyde hydrogenation. In some embodiments, a process for vapor-phase heterogeneous hydrogenation of aldehydes to produce alcohols comprises providing a mixture of a vapor stream comprising one or more aldehydes and a gas stream comprising hydrogen, and contacting the mixture with a solid catalyst comprising a copper-silicon alloy.

Description

CATALYST AND PROCESS FOR VAPOR-PHASE ALDEHYDE

HYDROGENATION

FIELD

The present invention relates to catalysts and processes for vapor-phase aldehyde hydrogenation.

BACKGROUND

The hydrogenation of aldehydes to produce alcohols has long been practiced. The reaction of an aldehyde with hydrogen generally is carried out in the presence of certain reduced metal compounds which act as hydrogenation catalysts. Commonly used commercial hydrogenation catalysts include cobalt compounds; nickel compounds, which may contain small amounts of chromium or other promoters; copper chromite; mixtures of reduced copper oxide with manganese oxide and/or chromium oxide; and mixtures of reduced copper oxide with zinc oxide (i.e., copper-zinc oxide), which may contain small amounts of nickel or other promoters.

Not surprisingly, such hydrogenation catalysts typically have one or more disadvantages when used for commercially hydrogenating aldehydes to alcohols. For example, most of these catalysts, such as cobalt compounds, the nickel compounds, copper chromite, the mixtures of reduced copper oxide with manganese oxide and/or chromium oxide, and the mixtures of reduced copper oxide with zinc oxide catalysts, exhibit a less than desired selectivity. Stated otherwise, when hydrogenating aldehydes using such catalysts, the quantity of by-products formed may be higher than desired. Such by-products reduce the desired aldehyde to alcohol conversion and generally must be removed from the hydrogenation product prior to a subsequent use of the alcohol. See, e.g., European Patent Publication Nos. 0 008 767 and 0 074 193.

Furthermore, copper chromite catalysts can be difficult to prepare, and the cobalt and nickel compounds are significantly more costly.

When using nickel catalysts, the principal by-products are ethers and hydrocarbons (paraffins) resulting from excessive hydrogenation. The amount of by-products formed in such processes may be anywhere from about 0.5 to about 3.0 weight percent and even higher, based on the total weight of the reaction product. For example, in the catalytic hydrogenation of butyraldehyde to butanol over a nickel catalyst, a small amount of butyl ether forms. The ethers form azeotropes with the alcohol hydrogenation products and water frequently present in the product from the feed streams. Thus, a substantial amount of capital and energy is required to separate by-product ethers from alcohols and significant losses of alcohol result from this activity. For example, separation of butyl ether from butanol is required for butanol to pass purity specifications. For making acrylates, such separation requires a series of costly distillation steps and because of the butyl ether-butanol azeotrope, four kilograms of butanol are lost for every kilogram of butyl ether formed. Such losses may render the use of an otherwise advantageous hydrogenation catalyst commercially unattractive.

The use of reduced copper oxide-zinc oxide catalysts yields esters as the principal by-product. For example, the catalytic hydrogenation of butyraldehyde to butanol over a a reduced copper oxide-zinc oxide catalyst yields n-butyl butyrate as a byproduct in minor amounts. While by-product esters may be easier to remove, the separation costs and associated losses are not inconsequential. Ester formation leads to a loss of alcohols via the ester stream purged from the bottom of the alcohol refining still in a typical recovery process. The approach used in European Patent Publication No. 0 074 193 seeks to avoid this loss by recovering and concentrating the esters and then converting them to additional alcohols by hydrogenolysis in another reactor containing reduced copper oxide-zinc oxide catalyst. This approach requires additional equipment. Furthermore, the amount of esters formed generally increases with increasing temperature in the catalytic hydrogenation reactor. Thus, to minimize by-product ester formation when using reduced copper oxide- zinc oxide catalysts, hydrogenation processes may need to be operated at relatively low temperatures. This is particularly true when an ester such as propyl propionate is the by product because of the difficulty of separating such esters from the desired alcohol using ordinary distillation techniques. Unfortunately, operation at lower temperatures results in a reduced rate of catalytic hydrogenation.

The tendency of the reduced copper oxide-zinc oxide catalysts to yield higher levels of esters at higher reaction temperatures also complicates the implementation of conventional catalytic techniques. Normally, to compensate for the gradual and unavoidable loss in hydrogenation catalytic activity with time, it is conventional practice to increase reaction temperature with time. When using reduced copper oxide-zinc oxide catalysts, however, such temperature increases lead to an increased formation of ester by products, thus further complicating subsequent product purification procedures or if the level of by-product ester formation increases above tolerable limits, necessitating an earlier change in the catalyst charge than dictated by hydrogenation rates.

The need to operate the reaction at lower temperatures also complicates the process by requiring either more costly reactors or an increase in the number of adiabatic reaction stages with intercoolers. Furthermore, less useful energy is recovered from the heat of reaction at lower temperatures.

As is evident from the foregoing, there remains a need in the area of catalytic hydrogenation of aldehydes to alcohols for a catalyst having improved product selectivity, particularly a catalyst which retains its high selectivity at the high temperatures needed to maximize reaction rates and energy efficiency. There also remains a need for chromium- free catalysts having such features, because of the apparent chromium toxicity and correspondingly increased costs due to special handling and disposal requirements for any chromium-contaning materials.

SUMMARY

The present invention relates to processes for vapor-phase hydrogenation of aldehyde to alcohols. In particular, the present invention utilizes a particular catalyst, copper-silicon alloys, to hydrogenate aldehydes to alcohols. Processes according to embodiments of the present invention can provide a significant improvement in selectivity as evidenced by a reduction in the production of undesired by-products. In addition, in some embodiments, the catalyst retains its strength (i.e., crush strength), and/or is resistant to leaching or other physical degradation effects.

In one aspect, a process for vapor-phase heterogeneous hydrogenation of aldehydes to produce alcohols comprises providing a mixture of a vapor stream comprising one or more aldehydes and a gas stream comprising hydrogen, and contacting the mixture with a solid catalyst comprising a copper-silicon alloy.

These and other embodiments are discussed in more detail in the Detailed

Description below. DETAILED DESCRIPTION

All references to the Periodic Table of the Elements and the various groups therein are to the version published in the CRC Handbook of Chemistry and Physics, 72nd Ed. (1991-1992) CRC Press, at page I- 11.

Unless stated to the contrary, or implicit from the context, all parts and percentages are based on weight and all test methods are current as of the filing date of this application. For purposes of United States patent practice, the contents of any referenced patent, patent application or publication are incorporated by reference in their entirety (or its equivalent U.S. version is so incorporated by reference).

As used herein,“a,”“an,”“the,”“at least one,” and“one or more” are used interchangeably. The terms“comprises,”“includes,” and variations thereof do not have a limiting meaning where these terms appear in the description and claims.

Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed in that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). For the purposes of the invention, it is to be understood, consistent with what one of ordinary skill in the art would understand, that a numerical range is intended to include and support all possible subranges that are included in that range. For example, the range from 1 to 100 is intended to convey from 1.01 to 100, from 1 to 99.99, from 1.01 to 99.99, from 40 to 60, from 1 to 55, etc.

As used herein, the term“ppmwt” means parts per million by weight.

The present invention relates to processes for vapor-phase hydrogenation of aldehydes to alcohols. In one aspect, a process for vapor-phase heterogeneous hydrogenation of aldehydes to produce alcohols comprises providing a mixture of a vapor stream comprising one or more aldehydes and a gas stream comprising hydrogen, and contacting the mixture with a solid catalyst comprising a copper- silicon alloy. In some embodiments, the weight ratio of copper-to-silicon in the catalyst is from 0.01:1 to 12:1. The weight ratio of copper to silicon in the catalyst, in some embodiments, is from 1 : 1 to 12:1. The weight ratio of copper to silicon in the catalyst is from 3:1 to 7:1 in some embodiments. Such ratios do not include any silicon that may be present as silica or silicate, provided as a catalyst support or catalyst binder in those embodiments where a catalyst support or catalyst binder is included. The catalyst is not limited to bulk copper-silicon alloy but can also be delivered via support that provides an inert structural matrix. Thus, in some embodiments, the solid catalyst further comprises a catalyst support. Examples of materials that provide an inert structural matrix that can be used as a catalyst support include alpha alumina and beta silicon carbide. In some embodiments, the total amount of support in the catalyst is from 0.1 to 90 weight percent based on the total weight of the catalyst.

In some embodiments, the solid catalyst does not include rare earth metals. In some embodiments, the solid catalyst does not include chromium.

In some embodiments, the aldehydes that are hydrogenated comprise C3 to C12 aldehydes.

Embodiments of processes of the present invention may be used to hydrogenate organic aldehydes to alcohols, for example C3 - C12 alcohols. Such processes maybe useful, for example, in the production of oxo- alcohols or glycols. Alcohols formed using processes of the present invention may include short chain alcohols (e.g., containing from 3 to 10 carbon atoms), and longer chain alcohols, such as fatty alcohols (e.g., containing up to 12 carbon atoms).

Such processes may be said to take place in the gas phase in that the aldehyde and hydrogen are introduced to the catalyst in the gas phase, although it is presumed that the actual reaction occurs at or near the surface of the solid catalyst. The process may take place in a batch reactor, such as an autoclave. Alternatively, the process may be a continuous process, wherein a gas phase feedstock containing the organic feedstock (e.g., the aldehydes) is caused to flow through a bed of catalyst particles. In some such embodiments, the gas hourly space velocity (GHSV) may be from 2,000 to 160,000 hr¹, from 2,000 to 80,000 hr ¹ in some embodiments, and from 2,000 to 12,000 hr¹.

Hydrogen is fed to the reactor as a gas, optionally mixed with at least one other gas such as nitrogen. Hydrogen may be dissolved in the gas-phase feed prior to, or during, the process of feeding the gas-phase aldehyde feedstock to the reactor. The hydrogen pressure may be in the range from 1 to 200 bar. Alternatively, a lower hydrogen pressure may be used, in the range 1 to 6 bar. The reaction conditions to be used depend upon the nature of the reaction and the starting materials used. The reaction may take place at a temperature of at least 100°C. When the process of the invention is a process for the hydrogenation of a C4 aldehyde, for example, a suitable temperature may be within the range from 120 to 300°C.

The aldehydes that can be hydrogenated according to embodiments of the present invention contain from 2 to 12 carbons, may be branched or contain cyclic moieties or other unsaturations. In other words, processes of the present invention can be used for hydrogenating a wide variety of straight or branched chain, saturated or unsaturated aldehydes containing from 2 to 12 carbon atoms. The aldehyde reactants also may contain other oxygenated groups except carboxylic acid groups. The feed stock is limited primarily, only by the practicability of vaporizing higher boiling aldehydes. Suitable aldehydes include saturated aldehydes like acetaldehyde, propionaldehyde, iso-butyraldehyde, n- butyraldehyde, isopentyl aldehyde, 2-methylpentaldehyde, 2-ethylhexaldehyde, 2- ethylbutyraldehyde, n-valeraldehyde, iso-valeraldehyde, caproaldehyde, methyl-n- propylacetaldehyde, iso-hexaldehyde, caprylaldehyde, n-nonylaldehyde, n-decanal, dodecanal, tridecanal, palmitic aldehyde, stearic aldehyde, and such unsaturated aldehydes as acrolein, methacrolein, ethacrolein, 2-ethyl-3-propylacrolein, crotonaldehyde and the like. The aldehyde may be in a substantially pure state or mixed with a component or components other than the aldehyde itself. Further, a mixture of aldehydes may be employed.

The aldehyde or mixture of aldehydes employed may be obtained by an oxo process in some embodiments. Persons of ordinary skill in the art will understand that an oxo process refers to the reaction of olefins with carbon monoxide and hydrogen in the presence of a catalyst to add a carbonyl group at one of the carbon atoms of the olefinic group. The aldehyde feed to hydrogenation processes of the present invention may comprise a portion or all of the product mixture of an oxo process, in various embodiments. Of course, the aldehyde or mixture of aldehydes can be obtained by processes other than an oxo process such as by oxidation of olefins or saturated hydrocarbons, or by an aldol condensation. The present invention is not limited to the source of any particular aldehyde.

The aldehyde in a vapor state is brought into contact with the hydrogenation catalyst in the presence of a hydrogen-containing gas. While substantially pure hydrogen alone can be used, it may be preferable in some cases to provide the hydrogen in admixture with other gases, desirably inert to the aldehyde and catalyst. Suitable inert gases for mixing with hydrogen include, without limitation, nitrogen and methane. As used herein, the term “hydrogen-containing gas” includes pure hydrogen gas, substantially pure hydrogen gas, and gaseous mixtures containing hydrogen and other gases inert to aldehydes and the specified catalyst.

While the concentration of hydrogen in the reaction zone is not critical, there generally should be an excess of hydrogen over the stoichiometric requirement relative to the aldehyde to be hydrogenated. Generally, the mol ratio of hydrogen to aldehyde will be from about 5 to 400 and preferably from about 10 to 200. For aldehydes containing from about 2 to 8 carbon atoms, the mol ratio of hydrogen to aldehyde preferably is in the range of about 10 to 30.

The process of the present invention is carried out in a continuous manner in some embodiments. In a continuous operation, the aldehyde, the mixture of aldehydes, or the oxo reaction products comprising aldehydes are vaporized as needed and brought together with the hydrogen-containing gas at the desired temperature and pressure over the catalyst specified for processes of the present invention. In some embodiments, the hydrogen gas can be introduced in multiple ports along the reactor. The catalyst advantageously may be used in a fixed catalyst bed reactor. For example, the reaction zone may be an elongated tubular reactor with the catalyst supported within the tubes. Adiabatic tank type reactors can also be used. In such reactors, the heat of reaction causes an increase in reaction temperature from reactor inlet to reactor outlet.

Alcohol product recovered from the hydrogenation reaction is separated from unreacted hydrogen by condensation and typically excess hydrogen is recompressed and recycled to the reaction zone. The crude alcohol product can be used as is, or can be further purified using conventional techniques such as fractional distillation. Unreacted aldehyde which may be recovered can also be recycled. In some embodiments, uncondensed alcohol and hydrocarbons present in the recycled hydrogen may comprise a portion of the hydrogen-containing gas fed to the catalyst.

Normally, the hydrogenation reaction is conducted at a temperature of at least about 100° C. Because of the high selectivity of the specified catalyst, the reaction can advantageously be conducted at a temperature as high as about 300°C in some

embodiments. In some embodiments, the reaction is carried out at a temperature in the range of about 120 to 260° C. Such a temperature range balances the competing factors of energy and reaction rate, while also keeping the temperature above the dew point of the aldehyde and alcohol at their respective concentrations in the gas stream.

The reaction can be conducted at any suitable pressure from atmospheric up to about 200 bar. In view of the need to maintain the aldehyde and alcohol products in the vaporous state above the dew point, reaction pressure is somewhat influenced by reaction

temperature, the aldehyde undergoing hydrogenation, and the quantity of hydrogen- containing gas.

Processes of the present invention utilize a solid catalyst comprising a copper-silicon alloy. In some embodiments, the catalyst comprises copper-silicide or a compound thereof. In the active form of the catalyst, the copper silicide is present as copper-silicon alloy. As known to persons of ordinary skill in the art, it is common to provide catalysts in which the active metal is present as a compound which is catalytically inactive or less active than the metal. Catalysts in that form may be activated by treatment to convert the less active compound to the active metal by reduction. The treatment typically involves contact with a hydrogen-containing gas at elevated temperature and may therefore be carried out in the reactor to be used for hydrogenation. After activation the catalyst contains active metallic copper-silicon alloy although there is usually also some unreduced copper present since the reduction process is rarely 100% efficient.

Catalysts may be supplied in a reduced form; however, such catalysts must be protected from contact with an oxygen-containing gas because they are pyrophoric. Typical protection methods include encapsulation (e.g., in a fat or wax material), and passivation. When the catalyst is passivated, a proportion of the active copper-silicon alloy is reacted to form passivating compounds such as an oxide or carbonate under controlled conditions.

The passivated catalyst can then be handled and the passivating compounds can be reduced on contact with hydrogen or other means. The catalyst used in some embodiments of the present invention therefore comprises copper-silicon alloy and/or a compound of copper- silicon alloy. Such compounds of the copper-silicon alloy can also include one or several transition metal components as promoters (other than copper), including nickel, cobalt, iron, manganese, chromium, vanadium, zinc, palladium, or others. In some embodiments, the catalyst comprises one or promoters in an amount from 0.01 to 10 percent by weight, based on the total weight of the catalyst.

The solid catalyst may comprise from 5 - 95% of copper, by weight as determined by neutron activation analysis, calculated as copper metal in some embodiments. In some embodiments, the solid catalyst may comprise 10 - 93% by weight of copper (calculated as copper metal) based on the total weight of the solid catalyst. In some embodiments, the solid catalyst may comprise 20 - 92% by weight of copper (calculated as copper metal) based on the total weight of the solid catalystln particular, the catalyst may contain 30 - 50 % by weight of copper (calculated as copper metal) based on the total weight of the solid catalyst.

The weight ratio of copper-to-silicon in the copper-silicon alloy catalyst ranges from 0.01:1 to 12:1 in some embodiments. In some embodiments, the weight ratio of copper-to- silicon in the copper-silicon alloy catalyst ranges from 0.2: 1 to 12: 1. The ratio of copper to silicon in the catalyst, in some embodiments, is from 3: 1 to 12: 1. The ratio of copper to silicon in the catalyst is from 5: 1 to 12: 1 in some embodiments. Such ratios do not include any silicon that may be present as silica provided as a catalyst support or catalyst binder in those embodiments where a catalyst support or catalyst binder is included. The weight of silicon in the solid catalyst may be measured by neutron activation analysis.

In some embodiments, the copper-silicon alloy is CusSi which contains 91.9 weight percent copper and 8.1 weight percent silicon, based on the total weight of the alloy. In some embodiments, the copper-silicon alloy is Cu3.i7Si which contains 87.8 weight percent copper and 12.2 weight percent silicon, based on the total weight of the alloy. In some embodiments, the copper-silicon alloy is CU7S13 which contains 84.1 weight percent copper and 15.9 weight percent silicon, based on the total weight of the alloy. In some embodiments, the copper-silicon alloy is CuSig which contains 20.1 weight percent copper and 79.9 weight percent silicon, based on the total weight of the alloy.

In some embodiments, the alloy is a copper-silicon-palladium-nickel alloy, having a structure of CuioSriPdo.iNio.i, which contains 89.6 weight percent copper, 8.1 weight percent silicon, 1.5 weight percent palladium, and 0.8 weight percent nickel, based on the total weight of the alloy. The solid catalyst may contain other materials such as catalyst supports or catalyst binder. In embodiments where the solid catalyst comprises a catalyst support, the catalyst support may comprise silica and/or alumina. A catalyst support is effective in improving the distribution and form of the catalytically active copper-silicon alloy component in the finished solid catalyst by providing the primary structure to the catalyst itself. A catalyst support containing silica and/or alumina may affect the catalytic properties of the catalyst such as crush strength, surface area, heat conduction, and the like. In some embodiments, the solid catalyst comprises a catalyst binder. A catalyst binder provides a structural bridging between the active catalyst particles, which affects, especially improves, the mechanical properties of the catalyst. The improvement in mechanical properties may have the effect of improving the activity of the catalyst in the reaction, through promotion of resistance of the catalyst to the feedstock, leading to retention of mechanical properties. Examples of catalyst binders that can be used in some embodiments include silica, MgO, MnCh, clay, and other binder materials known those of skill in the art based on the teachings herein.

The formation of a catalyst for use in the invention from a catalyst precursor may include the processes of calcination, reduction, and/or shaping. Shaping processes may include tabletting, extrusion, or granulation. The solid catalyst may also contain ingredients such as lubricants, pore-formers, pelleting aids etc.

The catalyst used in the invention may be made by conventional methods used in catalyst manufacturing. A copper-silicon alloy catalyst may, for example, be made by melting together precursor elements: copper and silicon, in an electrical arc furnace. The resulting bulk alloy material may then be reduced in size to a powder in a grinder. The alloy powder may then be separated into various particle size fractions using a set of shaker sieves with different mesh sizes. A desired particle size fraction of the copper-silicon alloy powder may then be used directly as catalyst in an aldehyde hydrogenation process.

Alternatively, a copper-silicon alloy powder, which is obtained using the method described above, may be mixed together with a binder material, and the resulting mixture may then be formed into tablet shapes using a tableting press. The tablets may then be heat-treated in an electrical tube furnace under a flow of reducing gas to yield a finished catalyst material. Alternatively, the synthesis steps of melting together the copper and silicon precursor elements to yield a copper-silicon alloy material, and then grinding the materials, as described in the paragraph above, may be omitted from the catalyst production process.

In such case, a mixture of copper and silicon precursor materials may be ground in a ball mill to produce a copper-silicon alloy powder by means of a mechanochemical synthesis. The resulting alloy powder material may be mixed together with a binder material, and the resulting mixture may then be formed into tablet shapes using a tableting press. The tablets may then be heat-treated in an electrical tube furnace under a flow of reducing gas to yield a finished catalyst material. Alternatively, the abovementioned mechanochemical synthesis step may be omitted and the copper metal and elemental silicon powders may be mixed directly with other catalyst precursor components, then the resulting mixture may be is pressed into catalyst precursor tablets. Then the tablets may be heat-treated to yield a finished catalyst product. Additional information regarding methods that can be used to prepare catalyst products useful in some embodiments of the present invention can be found in U.S. Patent No. 7,807,603 and Ahmadi et al.,“A simple granulation technique for preparing high-porosity nano copper oxide (P) catalyst beads,” Particuology 9 (2011), 480- 485.

Alternatively, a copper-silion alloys powder, as prepared by melting together the copper and silicon precursor elements, and by grinding the resulting alloy material into a fine powder, may be mixed with a liquid to yield a suspension of the alloy powder in the liquid. The resulting alloy suspension material may then be used to impregnate granules of a catalyst support material, which may be alpha-alumina, or beta-silicon carbide, or another type, using a method that is known in the art as the incipient wtness impregnation. The alloy suspension-impregnated granules may then be dried in air to evaporate the liquid, and then be heat-treated in an electrical tube furnace under a flow of reducing gas to yield a finished catalyst material.

The catalyst precursor tablets comprising the material containing a copper-silicon alloy powder, alumina catalyst support, or a catalyst binder, and/or any other desired precursor materials may be heat-treated for at least 30 minutes at a temperature of at least 300 °C. The heat-treatment temperature may be at least 500 °C. Alternatively, the heat treatment temperature may be at least 750 °C. The gas used to purge the catalyst precursor material volume during the heat treatement may be an inert gas, such as nitrogen, or argon, or another, and also contain 5% hydrogen. Alternatively, the purge gas used can be argon containing 50% hydrogen. Alternatively, the purge gas used can be pure hydrogen.

The catalyst catalyst particles suitable for use in a fixed catalyst bed may take the form of irregular shapes such as chunks of powder, or regular shapes such as spheres, cylinders, tablets, rings, wheels, saddles, lobed cylinders or irregular shapes such as granules. Such catalyst shapes may be prepared by various methods which are known to persons of ordinary skill in the art. The catalyst precursors mixture may be shaped into the desired shape, e.g. spheres, tablets, cylinders, lobed cylinders, rings or granules, before or after a heat-treatment step, if a heat-treatment step is carried out.

Some embodiments of the invention will now be described in more detail in the following Examples.

EXAMPLES

All parts and percentages in the following examples are by weight unless otherwise indicated. Pressures are given as absolute pressure unless otherwise indicated.

General Procedure

The effluent from the reactor is tested by in-line gas chromatography (GC) using a reference standard included in the raw materials feed at a known composition to provide accuracy. The GC detection limit is 80 ppm, when none of the products are detected (ND), the value should not be listed as zero, but rather less than 80 ppm. The conversion is defined as the percentage of aldehyde converted (the residual is unreacted aldehyde). Three current commercially available catalysts are tested for reference as Comparative Examples as well as two other Comparative Examples prepared by Applicant.

Comparative Example 1

A commercially-sourced catalyst consisting essentially of about 33 weight percent copper oxide and about 65 weight percent zinc oxide, and also about 3 percent by weight of nickel oxide (about 2.4 percent by weight of nickel), about 1 percent by weight of potassium carbonate (about 0.6 percent by weight of potassium), and about 2 percent by weight of graphite, is ground from the original form of tablets, having a diameter of 4.76 mm and a height of 4.76 mm, into a powder using a mortar and pestle. The catalyst powder is then separated into three particle size fractions using a set of two size mesh sieves. The cental fraction of the catalyst powder with a particle size beween 170 micron and 250 micron is selected and loaded into a tubular reactor, forming a catalyst bed with a 10 to 1 height- to- diameter ratio. The catalyst material in the bed is reduced first with a dilute hydrogen stream containing nitrogen as a diluent at a temperature near 220° C for 3 hours, then the hydrogen content in the gas flow is gradually increased to 100 volume percent in a course of 2 hours, and the catalyst is maintained at 220° C in a pure hydrogen flow for another 40 minutes.

Liquid mixed butyraldehyde containing one part iso-butyraldehyde and seventeen parts n-butyraldehyde, as produced in a low pressure oxo reaction of propylene over a rhodium-containing catalyst, is then fed at a space velocity of 0.65 hr ¹ (volumes of total liquid feed to total volume of catalyst per hour) into the reactor header where it evaporated and the aldehyde vapor mixed with the gas flow containing 66 percent hydrogen and 34 percent nitrogen by volume. The resulting buteraldehyde vapor gas mixture contains a mol ratio of hydrogen to aldehyde of 10 to one. A pressure of 115 psig is maintained at the outlet of the reactor. The vaporized aldehyde, hydrogen, and nitrogen mixture is fed to the reactor at 195° C, and the catalyst bed temperature is also maintained at 195° C along all its length, so the catalyst bed is isothermal.

The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by the flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. During the initial 100 hours of operation, the reaction temperature is varied between 140 °C and 220 °C to simulate the range of temperature conditions that the catalyst may be exposed in a production process, returning back to 195 °C at the end of the initial period. Averaging data for 18 hours from 3 chromatograms collected past the initial 100 hours of operation in the reaction, 98.7% of the aldehyde converted to products containing 0.54% by weight of mixed iso-and n-butyl butyrate esters and ether below the detection limits of 80 ppmwt.

Comparative Example 2

An experiment is run in the same reactor equipment described in Comparative Example 1 at similar reaction conditions except that the catalyst bed is made from another commercially-sourced catalyst consisting essentially of about 35 weight percent copper oxide and about 55 weight percent zinc oxide, and also about 3 percent by weight of nickel oxide (about 2.4 percent by weight of nickel), about 1 percent by weight of potassium carbonate (about 0.6 percent by weight of potassium), and about 10 percent by weight of clay. The catalyst is ground from the original form of extrudates having a diameter of 3.175 mm and a height of 7.5 mm into a powder fraction between 170 micron and 250 micron, making a catalyst bed with a 10 to 1 height-to-diameter ratio. The hydrogenation reaction is run isothermally at 195° C, and the effluent from the reactor is monitored by gas chromatography. After the initial 100 hours of operating the reaction, the product stream composition data from 18 hours of operation, obtained in 3 chromatograms, is averaged. 97.6 % of the aldehyde converted to products containing 0.89% by weight of mixed iso-and n-butyl butyrate esters and ether below the detection limits of 80 ppmwt.

Comparative Example 3

An experiment is run in the same reactor equipment described in Comparative Example 1 at similar reaction conditions except that the catalyst bed which, in the unreduced state, comprises 35% by weight of copper, calculated as Cu, 31% by weight of chromium, calculated as Cr, 2.0% by weight of barium, calculated as Ba, and 2.5% by weight of manganese, calculated as Mn. The catalyst is reduced to powder using the procedure described comparative example to Example 1. The catalyst bed has a 10 to 1 height-to-diameter ratio. The hydrogenation reaction is run isothermally at 195° C, and the effluent from the reactor is monitored by gas chromatography. After the initial 100 hours of operating the reaction, the product stream composition data from 18 hours of operation, obtained in 3 chromatograms, is averaged. 98.4 % of the aldehyde converted to products containing 6.97% by weight of mixed iso-and n-butyl butyrate esters and ether below the detection limits of 80 ppmwt.

Comparative Example 4

An commercially sourced copper powder of > 99.5 atomic percent purity is sifted to a narrow particle size range falling between 37 and 62 microns. The powder is loaded into a fixed bed reactor with a height to diameter ratio of 5.5, and is reduced by slowly increasing the hydrogen content in an inert gas stream while increasing temperature to a final reduction condition of 100% hydrogen held at 220 °C for 3 hours. A 195 °C feed mixture of hydrogen and butyraldehyde (95% butyraldehyde, 5% isobutyraldehyde) at a 10: 1 molar ratio is passed over the isothermal catalyst bed at a combined vapor (vaporized liquid and gas) space velocity of 4200 hr ¹ and 115 psig pressure. The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by the flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. During the initial 100 hours of operation, the reaction temperature is varied between 140 °C and 220 °C to simulate the range of temperature conditions that the catalyst may be exposed to a production process, returning back to 195 °C at the end of the initial period. After the initial 100 hours of operating the reaction, the product stream composition data from 18 hours of operation, obtained in 3 chromatograms, is averaged. 5.9 % of the aldehyde converted to products containing less than 0.03% by weight of butyl butyrate ester and ether below the detection limits of 80 ppmwt.

Comparative Example 5

An alloy of nickel and silicon is obtained by arc-melting of precursor elements in an atomic ratio of 3 nickel to 2 silicon, which corresponds to 75 percent of nickel and 25 percent of silicon by weight, referred to as Ni3Si2 nickel silicide. The alloy is ground in a ball mill using a milling vial that is lined with tungsten carbide, and sifted to a narrow particle size range falling between 37 and 62 microns. The alloy powder is loaded into a fixed bed reactor with a height to diameter ratio of 6.5, and is reduced by slowly increasing the hydrogen content in an inert gas stream while increasing temperature to a final reduction condition of 100% hydrogen held at 220 °C for 3 hours. A 195 °C feed mixture of hydrogen and butyraldehyde (95% butyraldehyde, 5% isobutyraldehyde) at a 10: 1 molar ratio is passed over the isothermal catalyst bed at a combined vapor (vaporized liquid and gas) space velocity of 4200 hr ¹ and 115 psig pressure. The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by a flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. During the initial 100 hours of operation, the reaction temperature is varied between 140 °C and 220 °C to simulate the range of temperature conditions that the catalyst may be exposed to in a production process, returning back to 195 °C at the end of the initial period. After the initial 100 hours of operating the reaction, the product stream composition data from 18 hours of operation, obtained in 3 chromatograms, is averaged. 99.4 % of the aldehyde converted to products containing 0.22% by weight of butyl butyrate ester and 3.31 % by weight of dibutyl ether.

Inventive Example 1

An alloy of copper and silicon obtained by arc-meting of elements in an atomic ratio of 5 copper to 1 silicon, which corresponds to 91.9 percent of copper and 8.1 percent of silicon by weight, referred to as CusSi copper silicide. The alloy is ground and sifted to a narrow particle size range falling between 180 and 250 microns. The alloy powder is loaded into a fixed bed reactor with a height to diameter ratio of 13.3, and is reduced by slowly increasing the hydrogen content in an inert gas stream while increasing temperature to a final reduction condition of 100% hydrogen held at 200 °C for 60 minutes. A 200 °C feed mixture of hydrogen gas and butyraldehyde (90% butyraldehyde, 10%

isobutyraldehyde) vapor at a 13: 1 molar ratio at 100 psig is passed over the isothermal catalyst bed at a combined vapor (vaporized liquid and gas) space velocity of 4620 hr¹.

The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by a flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. Averaging data from 8 chromatograms over 60 hours of reaction, 98.5% of the aldehyde converted to products containing less than 0.05% by weight of butyl butyrate ester and ether formation is below detection limits of 80 ppmwt.

Inventive Example 2

An alloy of copper and silicon is obtained by arc-melting of elements in an atomic ratio of 3.17 copper to 1 silicon, which corresponds to 87.8 percent of copper and 12.2 percent of silicon by weight, referred to CU3.17S1 copper silicide. The alloy is ground and sifted to a narrow particle size range falling below 180 microns. The alloy powder is loaded into a fixed bed reactor with a height to diameter ratio of 1.7 and is reduced by slowly increasing the hydrogen content in an inert gas stream while increasing temperature to a final reduction condition of 100% hydrogen held at 200 °C for 60 minutes. A 200 °C feed mixture of hydrogen gas and butyraldehyde (90% butyraldehyde, 10% isobutyraldehyde) vapor at a 13: 1 molar ratio is passed over the isothermal catalyst bed at a combined vapor (liquid and gas) space velocity of 617 hr¹ at 100 psig for 50 hours. The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by the flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components.

Averaging data over 50 hours of reaction showed 99.2% of the aldehyde converted to products with both ester and ether concentrations of less than 80 ppmwt (below the detection limit).

Inventive Example 3

Following the conditions of Inventive Example 2, the temperature is then increased to 250 °C at 100 psig for 17 hours. The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by the flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. Averaging data from over 17 hours of reaction showed 98.6% of the aldehyde converted to products containing less than 0.04% butyl butyrate ester and ether formation below the detection limits of 80 ppmwt.

Inventive Example 4

An alloy of copper and silicon is obtained by arc-melting of elements in an atomic ratio of 3 copper to 7 silicon, which corresponds to 49.2 percent of copper and 50.8 percent of silicon by weight, referred to CU3S17 copper silicide. The alloy is ground in a ball mill using a milling vial that is lined with tungsten carbide, and sifted to a narrow particle size range falling between 37 and 62 microns. The alloy powder is loaded into a fixed bed reactor with a height to diameter ratio of 6.5, and is reduced by slowly increasing the hydrogen content in an inert gas stream while increasing temperature to a final reduction condition of 100% hydrogen held at 220 °C for 3 hours. A 195 °C feed mixture of hydrogen and butyraldehyde (95% butyraldehyde, 5% isobutyraldehyde) at a 10:1 molar ratio is passed over the isothermal catalyst bed at a combined vapor (vaporized liquid and gas) space velocity of 4200 hr ¹ and 115 psig pressure. The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by a flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. During the initial 100 hours of operation, the reaction temperature is varied between 140 °C and 220 °C to simulate the range of temperature conditions that the catalyst may be exposed to a production process, returning back to 195 °C at the end of the initial period. After the initial 100 hours of operating the reaction, the product stream composition data from 18 hours of operation, obtained in 3 chromatograms, is averaged. 99.0 % of the aldehyde converted to products containing less than 0.20% by weight of butyl butyrate ester and ether formation below the detection limits of 80 ppmwt.

Inventive Example 5

An alloy of copper and silicon is obtained by arc-melting of elements in an atomic ratio of 1 copper to 9 silicon, which corresponds to 20.1 percent of copper and 79.9 percent of silicon by weight, referred to CuiSig copper silicide. The alloy is ground and sifted to a narrow particle size range falling between 37 and 62 microns. The alloy is loaded into a fixed bed reactor with a length to diameter ratio of 7.5 and is reduced by slowly increasing the hydrogen content in an inert gas stream while increasing temperature to a final reduction condition of 100% hydrogen held at 220 °C for 3 hours. A 195 °C feed mixture of hydrogen and butyraldehyde (90% butyraldehyde, 10% isobutyraldehyde) at a 10:1 molar ratio is passed over the isothermal catalyst bed at a combined vapor (vaporized liquid and gas) space velocity of 4200 hr ¹ and 115 psig pressure. The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by the flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. During the initial 100 hours of operation, the reaction temperature is varied between 140 °C and 220 °C to simulate the range of temperature conditions that the catalyst may be exposed to a production process, returning back to 195 °C at the end of the initial period. After the initial 100 hours of operating the reaction, the product stream composition data from 18 hours of operation, obtained in 3 chromatograms, is averaged. 98.7 % of the aldehyde converted to products containing less than 0.30% by weight of butyl butyrate ester and ether below the detection limits of 80 ppmwt.

Inventive Example 6

An alloy of copper, silicon, palladium and nickel is obtained by arc-melting of elements in an atomic ratio of 10:2:0.1:0.1 which corresponds to 89.6 percent of copper, 8.1 percent of silicon, 1.5 percent of palladium, and 0.8 percent of nickel by weight. The alloy is ground and sifted to a narrow particle size range falling between 180 and 250 microns. The alloy is loaded into a fixed bed reactor with a length to diameter ratio of 1.7 and is reduced by slowly increasing the hydrogen content in an inert gas stream while increasing temperature to a final reduction condition of 100% hydrogen held at 200 °C for 60 minutes. A 200 °C feed mixture of hydrogen and butyraldehyde (90% butyraldehyde, 10% isobutyraldehyde) at a 13: 1 molar ratio is passed over the isothermal catalyst bed at a combined vapor (liquid and gas) space velocity of 617 hr ¹ for 57 hours at 100 psig. The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by the flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. Averaging data over 57 hours of reaction showed 99.5% of the aldehyde converted to products containing less than 0.1% butyl butyrate ester by weight and ether below detection limits of 80 ppmwt.

Inventive Example 7

An alloy of copper and silicon is made in an atomic ratio of 7 copper to 3 silicon, which corresponds to 84.1 percent of copper and 15.9 percent of silicon by weight, referred to CU7S13 copper silicide. The alloy is ground and sifted to a narrow particle size range falling between 37 and 62 microns. The alloy powder is thoroughly mixed by hand in a glass vial with a commercially sourced pure copper powder of 10 micron particle size in a ratio containing 90 percent of the copper-silicon alloy powder and 10 percent of pure copper powder by weight), and the powder mixture is pressed into tablets having a diameter of 4.76 mm dimeter and a height of 3.71 mm using a tableting press. 5 grams of the tablets are loaded into a stainless steel 0.45” internal diameter fixed bed reactor with the catalyst bed length- to-diameter ratio of 8. The void between the tablets is filled with a commercial high purity silicon carbide powder particle size range falling between 300 and 450 microns. The catalyst bed is reduced by slowly increasing the hydrogen content in an inert gas stream while increasing temperature to a final reduction condition of 100% hydrogen held at 220 °C for 3 hours. A 195 °C feed mixture of hydrogen and butyraldehyde (95% butyraldehyde, 5% isobutyraldehyde) at a 10: 1 molar ratio is passed over the isothermal catalyst bed at a combined vapor (liquid and gas) space velocity of 4000 hr ¹ and 115 psig pressure for 100 hours. The effluent from the reactor is monitored by gas chromatography calibrated with an internal standard of decane and captured by the flame ionization detector. The collected information is adjusted to a normalized standard volume and appropriate response factors for the components. During the initial 100 hours of operation, the reaction temperature is varied between 140 °C and 220 °C to simulate the range of temperature conditions that the catalyst may be exposed to a production process, returning back to 195 °C at the end of the initial period. After the initial 100 hours of operating the reaction, the product stream composition data from 18 hours of operation, obtained in 3 chromatograms, is averaged. 96.9 % of the aldehyde converted to products containing less than 0.10% by weight of butyl butyrate ester and ether formation below the detection limits of 80 ppmwt.

The results of the Comparative Examples and Inventive Examples 1-7 are summarized in Table 1:

Table 1

Claims

WHAT IS CLAIMED IS:

1. A process for vapor-phase heterogeneous hydrogenation of aldehydes to produce alcohols comprising:

providing a mixture of a vapor stream comprising one or more aldehydes and a gas stream comprising hydrogen; and

contacting the mixture with a solid catalyst comprising a copper-silicon alloy.

2. The process of claim 1, wherein the weight ratio of copper-to- silicon in the catalyst is from 0.01:1 to 12:1.

3. The process of claim 1 or claim 2, wherein the solid catalyst comprises 30 to 50 weight percent copper based on the total weight of the catalyst.

4. The process of any of the preceding claims, wherein the solid catalyst further comprises a catalyst support.

5. The process of any of the preceding claims, wherein the solid catalyst further comprises a catalyst binder.

6. The process of any of the preceding claims, wherein the solid catalyst does not include rare earth metals.

7. The process of any of the preceding claims, wherein the aldehyde is a C3 to C12 aldehyde.