Patent Application
20250136535
The present invention concerns a novel heterogeneous bimetallic catalyst, method for preparing the same and use thereof in the synthesis of ethylene glycol from carbon monoxide.
Ethylene glycol is an important material in the chemical industry, enabling the production of textile fibres and polyester resins. One way of synthesizing ethylene glycol is to hydrogenate oxalates.
Oxalates are high value-added raw materials in the chemical industry. They are used on a large scale to produce various dyes, medicines, solvents, extraction agents and various intermediates in the fine chemicals industry.
A traditional production method for oxalates involves the esterification of oxalic acid with alcohols. This production technique is costly, energy-intensive, polluting and involves unreasonable use of raw materials.
In general, the carbonylation reaction from CO leading to the formation of oxalate, and the hydrogenation reaction from oxalate to ethylene glycol are catalysed by two quite different catalysts. For example, the carbonylation step is generally carried out with a heterogeneous palladium-based catalyst, while the hydrogenation step is carried out with a copper-based catalyst. However, copper does not catalyse the formation of oxalate, and palladium does not allow the hydrogenation of oxalic derivatives to ethylene glycol. The two steps therefore use very different catalysts with different transition metals, which can present a major challenge in a large-scale industrial process.
For many years, there has been a need for a low-cost, environmentally-friendly way of producing ethylene glycol.
Until now, it is looking for a heterogeneous catalyst that will enable the efficient synthesis of ethylene glycol in a way that is environmentally friendly, easy to industrialize and safe.
The use of a catalyst capable of both catalysing the reaction of carbonylation of alcohol to oxalate and also catalysing the reaction of hydrogenation of oxalate to ethylene glycol in a process for preparing ethylene glycol is of industrial interest and advantage in practical and material terms.
One of the aims of the invention is to propose a process for preparing ethylene glycol, in two catalysed reaction steps using a single catalyst of the same nature, the two reaction steps being the carbonylation of alcohol to oxalate and the hydrogenation of oxalate to ethylene glycol.
Another aim of the invention is a process for preparing ethylene glycol in two reaction steps of carbonylation and hydrogenation with efficient yields and high selectivity.
Another aim of the invention is to prepare ethylene glycol without using toxic reagents such as nitro-derivatives.
Another aim of the invention is the preparation of ethylene glycol, using recyclable or recycled reagents such as CO2 or CO and an efficient and reusable heterogeneous catalyst.
Another aim of the invention is to provide a new heterogeneous supported bimetallic catalyst.
Another aim of the invention is to provide a heterogeneous catalyst that can be used in a continuous flow process.
Another aim of the present invention is to propose a simple, suitable for industry and optimised preparation process for this catalyst.
A first object of the present invention is the use of a supported bimetallic catalyst of formula Pd-M/Support, comprising palladium and a metal M on a support, in which M represents Cu or Ag, in the implementation of a process for preparing ethylene glycol from an alcohol, comprising two reaction steps catalysed by the same bimetallic catalyst, in particular
For the purposes of this invention, “same catalyst” means a catalyst of the same nature, the characteristics of which are identical to those of the catalyst referred to, i.e. in particular the physical, chemical and surface characteristics, in particular the nature of the metals and the support, their proportions, the size and morphology of the particles.
The inventors have surprisingly observed the possibility of using supported bimetallic palladium-copper or palladium-silver catalysts to catalyse the reaction of carbonylation of alcohol to oxalate and the reaction of hydrogenation of oxalate to ethylene glycol. Both reactions can be carried out without prior treatment of the catalyst by a step of metal reduction under hydrogen. The combination of palladium with copper or silver (two metals in the same column as gold in the Periodic Table of the Elements) makes it possible to obtain catalysts capable of catalysing the carbonylation and hydrogenation reactions implemented in the process for preparing ethylene glycol from an alcohol.
According to a particular embodiment, the invention relates to the use of a supported bimetallic catalyst of formula Pd—Cu/Support, in the implementation of a method for preparing ethylene glycol from an alcohol, comprising two reaction steps catalysed by the same bimetallic catalyst, in particular:
The inventors also unexpectedly observed that the use of the bimetallic Pd—Cu/ZrO2 catalyst made it possible to obtain higher yields of the oxidative carbonylation and hydrogenation reaction steps in the preparation of ethylene glycol than those obtained with the corresponding monometallic Pd/ZrO2 and Cu/ZrO2 catalysts, demonstrating a synergistic effect of the bimetallic catalyst for carbonylation and hydrogenation.
According to a particular embodiment, the invention relates to the use of a supported bimetallic catalyst of formula Pd—Ag/Support, in the implementation of a process for the preparation of ethylene glycol from an alcohol, comprising two reaction steps catalysed by the same bimetallic catalyst, in particular:
The invention is based on the use of the same catalyst, i.e. a catalyst with the same characteristics, capable of catalysing two different reaction steps used in the ethylene glycol preparation process, in particular an oxidative carbonylation reaction step and a hydrogenation step.
For the purposes of this invention, “Pd-M bimetallic catalyst” means a catalyst in which the catalytic sites comprise palladium and a metal M, M being Cu or Ag. The palladium and the metal M combine to form the catalytic sites operating during the two catalysed reaction steps. Bimetallic catalysts according to the invention include catalysts in which the two metals are in the form of a core-shell structure, or in the form of a homogeneous alloy, or in the form of two distinct populations of particles of palladium and of metal M respectively, or in the form of a mixture of populations of these different forms.
It is understood that the Pd-M/Support catalyst is a heterogeneous catalyst.
The use of a heterogeneous catalyst has the advantage of facilitating the separation of the catalyst from the other species involved in the reaction, making it easy to recover and reuse the catalyst.
The use of a heterogeneous catalyst also has the advantage of making it possible, in the reactor, to fix the catalyst in an enclosure such as a cartridge when operating under continuous flow, and thus to obtain catalyst-free products at the reactor outlet.
For the purposes of this invention, “reaction step” means a synthesis step involving a chemical reaction using starting reagents to form end products. The chemical reaction leads to a transformation of the molecular structure of the starting reagents. Carbonylation and hydrogenation are understood to be reaction steps. On the other hand, product recovery, washing or purification steps are not considered reaction steps.
A reaction step is said to be catalysed when it requires a catalyst for its implementation.
For the purposes of this invention, “same catalyst” means a catalyst of the same nature, with the same characteristics such as the nature of the metals and the support, and their proportions.
Thus, one of the industrial advantages is that only one type of catalyst can be used or prepared, limiting the raw materials or catalyst preparation steps required for the ethylene glycol preparation process. Limiting the number of raw materials means that purchasing costs and waste management can be optimised. Limiting the number of industrial steps is advantageous from the point of view of costs and process implementation.
In a particular embodiment, the invention relates to the use as defined above, in which the catalyst support is an oxide.
Oxide supports are commonly used to prepare heterogeneous catalysts, partly because of the efficiency of the catalytic properties obtained and partly because they are readily available and easy to prepare. For example, they are advantageously less expensive than polymer supports.
In a particular embodiment, the invention relates to the use as defined above, in which the catalyst support is an oxide selected from zirconium dioxide ZrO2, alumina Al2O3, silica SiO2, cerium dioxide CeO2, titanium dioxide TiO2, magnesium oxide MgO, indium oxide In2O3, or a mixture of these oxides, preferably zirconium dioxide ZrO2.
In a particular embodiment, the invention relates to the use as defined above, in which the catalyst support is an oxide selected from zirconium dioxide ZrO2, alumina Al2O3 and silica SiO2.
In a particular embodiment, the invention relates to the use as defined above, wherein said supported bimetallic catalyst is a Pd—Cu/ZrO2 catalyst.
In a particular embodiment, the zirconium dioxide support ZrO2 has a melting temperature of 2700 to 2750° C., in particular 2715° C., and a density of 5 to 6 g/cm3.
The zirconium dioxide support can, for example, be obtained from STERM Chemicals (15 Rue de l'Atome, 67800 Bischheim).
The Pd—Cu bimetallic catalyst is preferably supported on zirconium dioxide ZrO2, but another type of support based on another oxide such as Al2O3, SiO2, CeO2, TiO2, MgO, In2O3 can also be implemented.
In a particular embodiment, the oxide support of said Pd-M bimetallic catalyst is in the form of a layer on the surface of another inert material, i.e. non-chemically active, such as ceramics or glasses.
In a particular embodiment, the invention relates to the use as defined above, in which the catalyst has a palladium content from 0.1 to 10%, in particular 2%, and a content of metal M from 0.1 to 40%, in particular 10% or 15%, by weight relative to the total weight of the catalyst. It is understood that the ratio between the total content of metals Pd-M and the support varies from 0.2 to 50% by weight in the catalysts of the invention. The weight of the metals represents up to half the total weight of the catalyst.
The expression “from 0.1 to 10%” corresponds to the following ranges: from 0.1 to 1%; from 1 to 2%; from 2 to 3%; from 3 to 4%; from 4 to 5%; from 5 to 6%; from 6 to 7%; from 7 to 8%; from 8 to 9%; from 9 to 10%.
The expression “from 0.1 to 40%” corresponds to the following ranges: from 0.1 to 5%; from 5 to 10%; from 10 to 15%; from 15 to 20%; from 20 to 25%; from 25 to 30%; from 30 to 35%; from 35 to 40%.
In a particular embodiment, the invention relates to the use as defined above, in which the weight ratio between Pd and M is from 1:1 to 1:20, preferably from 1:1 to 1:10, more preferably 1:5.
The expression “from 1:1 to 1:20” corresponds to the ranges: from 1:1 to 1:2; from 1:2 to 1:3; from 1:3 to 1:4; from 1:4 to 1:5; from 1:5 to 1:6; from 1:6 to 1:7; from 1:7 to 1:8; from 1:8 to 1:9; from 1:9 to 1:10; 1:10 to 1:11; from 1:11 to 1:12; from 1:12 to 1:13; from 1:13 to 1:14; from 1:14 to 1:15; from 1:15 to 1:16; from 1:16 to 1:17; from 1:17 to 1:18; from 1:18 to 1:19; from 1:19 to 1:20.
In a particular embodiment, the invention relates to the use as defined above, wherein the first catalysed reaction step is an oxidative carbonylation, from an alcohol, carbon monoxide and an oxidant, in particular molecular oxygen, optionally in the presence of a promoter, to form an oxalate compound as reaction intermediate, and wherein the second catalysed reaction step is a hydrogenation reaction of said oxalate compound by hydrogen to obtain ethylene glycol. The general diagram of a preparation process according to the invention can be represented as follows:
By “oxalate” it is meant the dialkyloxalate (DAO) corresponding to the alcohol used.
By “promoter” or “reaction promoter” it is meant a substance that can improve the properties of a catalyst, such as catalytic activity, selectivity, stability, lifetime or prevent deactivation of the catalyst.
In a particular embodiment, the promoter is an oxidant. The promoter can thus promote the oxidative carbonylation process.
According to a particular embodiment, the invention relates to the use as defined above, the implementation of the oxidative carbonylation reaction step comprising at least one additive.
By “additive” it is meant a substance which improves the yield of the reaction but which is not essential for it to take place. An additive does not intervene directly in the transformation of the substrate and consequently does not enter into the balance equation of the reaction.
According to a particular embodiment, the additive is a base, preferably selected from triethylamine (Et3N), 2,6-lutidine, caesium carbonate (Cs2CO3), or 1-methylimidazole.
Another object of the present invention relates to a method of preparation of ethylene glycol comprising:
The reaction step A, corresponding to the oxidative carbonylation reaction of an alcohol, is schematised as follows:
The reaction step B corresponding to the hydrogenation of an oxalate compound (DAO) is schematised as follows:
According to a particular embodiment, the invention relates to a method of preparation of ethylene glycol as defined above, in which:
According to a particular embodiment, the invention relates to a method as defined above, in which:
The method according to the present invention has the advantage of not requiring a solvent in reaction step A, the oxidative carbonylation of the alcohol. Advantageously, the alcohol can act both as reagent and solvent in reaction step A.
According to a particular embodiment, the invention relates to a method as defined above, in which:
Advantageously, oxidative carbonylation reaction step A of the process according to the invention can be carried out in the absence of solvent.
According to a particular embodiment, the invention relates to a method as defined above, in which:
Advantageously, oxidative carbonylation reaction step A of the method according to the invention can be carried out in the presence of a solvent.
According to a particular embodiment, the invention relates to a method as defined above, in which:
By “reaction medium” it is meant all the species brought together during a chemical reaction. It includes in particular the reagents in liquid or gaseous form, the catalyst, and optionally a solvent, additives or promoters.
The expression MPa corresponds to 106 Pascal and is equivalent to 10 bars.
The expression “from 0.1 to 15.0 MPa” corresponds to the ranges: from 0.1 to 0.5 MPa; from 0.5 to 1.0 MPa; from 1.0 to 1.5 MPa; from 1.5 to 2.0 MPa; from 2.0 to 2.5 MPa; from 2.5 to 3.0 MPa; from 3.0 to 3.5 MPa; from 3.5 to 4.0 MPa; from 4.0 to 4.5 MPa; from 4.5 to 5.0 MPa; from 5.0 to 5.5 MPa; from 5.5 to 6.0 MPa; from 6.0 to 6.5 MPa; from 6.5 to 7.0 MPa; from 7.0 to 7.5 MPa; from 7.5 to 8.0 MPa; from 8.0 to 8.5 MPa; from 8.5 to 9.0 MPa; from 9.0 to 9.5 MPa; from 9.5 to 10.0 MPa; from 10.0 to 10.5 MPa; from 10.5 to 11.0 MPa; from 11.0 to 11.5 MPa; from 11.5 to 12.0 MPa; from 12.0 to 12.5 MPa; from 12.5 to 13.0 MPa; from 13.0 to 13.5 MPa; from 13.5 to 14.0 MPa; from 14.0 to 14.5 MPa; from 14.5 to 15.0 MPa.
According to a particular embodiment, the invention relates to a method as defined above, in which the alcohol used in reaction step A is also used as solvent in reaction step B. Advantageously, it is thus not necessary to evaporate the alcohol in the oxalate product obtained in reaction step A before using it as a reagent in reaction step B.
The method according to the present invention has the advantage of not requiring a base in reaction step A, oxidative carbonylation of the alcohol. Indeed advantageously the base is an additive which promotes the efficiency of the reaction but which is not necessary for carrying out reaction step A.
According to a particular embodiment, the invention relates to a method as defined above, in which:
Advantageously, oxidative carbonylation reaction step A of the method according to the invention can be carried out without a base.
According to a particular embodiment, the invention relates to a method as defined above, in which:
According to a particular embodiment, the invention relates to a method as defined above, in which said catalyst comprises an oxide support selected from zirconium dioxide ZrO2, alumina Al2O3, silica SiO2, cerium dioxide CeO2, titanium dioxide TiO2, magnesium oxide MgO, indium oxide In2O3, or a mixture of these oxides, preferably zirconium dioxide ZrO2.
According to a particular embodiment, the invention relates to a method as defined above, in which said catalyst is of formula Pd—Cu/ZrO2.
According to a particular embodiment, the invention relates to a method as defined above, in which the catalyst has a palladium content from 0.1 to 10%, in particular 2%, and a content of metal M from 0.1 to 40%, in particular 10%, by weight relative to the total weight of the catalyst.
According to a particular embodiment, the invention relates to a method as defined above, in which the catalyst is used in reaction step A in a proportion from 0.01 to 10 mol % of palladium relative to the alcohol.
The expression “from 0.01 to 10%” corresponds to the following ranges: from 0.01 to 0.05%; from 0.05 to 0.1%; from 0.1 to 0.15%; from 0.15 to 0.2%; from 0.2 to 0.5%; from 0.5 to 1%; from 1 to 2%; from 2 to 3%; from 3 to 4%; from 4 to 5%; from 5 to 6%; from 6 to 7%; from 7 to 8%; from 8 to 9%; from 9 to 10%.
According to a particular embodiment, the invention relates to a method as defined above, in which carbon monoxide is used in reaction step A at a rate from 0.5 to 8.0 MPa, in particular 6.5 MPa.
The expression “from 0.5 to 8.0 MPa” corresponds to the ranges: from 0.5 to 1.0 MPa; from 1.0 to 1.5 MPa; from 1.5 to 2.0 MPa; from 2.0 to 2.5 MPa; from 2.5 to 3.0 MPa; from 3.0 to 3.5 MPa; from 3.5 to 4.0 MPa; from 4.0 to 4.5 MPa; from 4.5 to 5.0 MPa; from 5.0 to 5.5 MPa; from 5.5 to 6.0 MPa; from 6.0 to 6.5 MPa; from 6.5 to 7.0 MPa; from 7.0 to 7.5 MPa; from 7.5 to 8.0 MPa.
According to a particular embodiment, the invention relates to a method as defined above, in which the oxidant in reaction step A is oxygen, used at a rate from 0.5 to 2.5 MPa, in particular 1.5 MPa.
The expression “from 0.5 to 2.5 MPa” corresponds to the following ranges: from 0.5 to 1.0 MPa; from 1.0 to 1.5 MPa; from 1.5 to 2.0 MPa; from 2.0 to 2.5 MPa.
According to a particular embodiment, the invention concerns a method as defined above in which the oxidant is selected from: molecular oxygen (O2), air, a dione in particular 1,4-benzoquinone, 1,4-dichloro-2-butene and CuCl2.
It is understood that air containing 20% O2 can be used to carry out the process in which O2 is the oxidant.
According to a particular embodiment, the invention relates to a method as defined above, in which a promoter is used in reaction step A, in particular an iodine compound, in particular selected from tetramethylammonium iodide, potassium iodide or sodium iodide,
According to a particular embodiment, the invention relates to a method as defined above, in which the promoter is used in a proportion from 0.1 to 5 mol % relative to the alcohol, in particular in a proportion of 0.2 mol %.
The expression “from 0.1 to 5%” corresponds to the following ranges: from 0.1 to 0.15%; from 0.15 to 0.2%; from 0.2 to 0.3%; from 0.3 to 0.4%; from 0.4 to 0.5%; from 0.5 to 1%; from 1 to 2%; from 2 to 3%; from 3 to 4%; from 4 to 5%.
According to a particular embodiment, the invention relates to a method as defined above, in which a base is used in reaction step A, in particular triethylamine.
According to a particular embodiment, the invention relates to a method as defined above, in which the base is used in a proportion from 0.1 to 5 mol % relative to the alcohol, in particular in a proportion of 0.15 mol %.
The expression “from 0.1 to 5%” corresponds to the following ranges: from 0.1 to 0.15%; from 0.15 to 0.2%; from 0.2 to 0.3%; from 0.3 to 0.4%; from 0.4 to 0.5%; from 0.5 to 1%; from 1 to 2%; from 2 to 3%; from 3 to 4%; from 4 to 5%.
According to a particular embodiment, the invention relates to a method as defined above, in which a solvent is used in reaction step A, in particular selected from acetonitrile, tetrahydrofuran, dioxane and toluene, preferably acetonitrile.
According to a particular embodiment, the invention relates to a method as defined above, in which in reaction step A, the reaction medium 1 is pressurised from 0.1 to 15 MPa, preferably about 8 MPa.
According to a particular embodiment, the invention relates to a method as defined above, in which in reaction step A, the reaction medium 1 is heated to a temperature from 25 to 200° C., in particular from 60 to 110° C., preferably about 90° C., in particular during from 2 to 24 hours, preferably during 16 hours.
The expression “from 25 to 200° C.” corresponds to the following ranges: from 25 to 40° C.; from 40 to 60° C.; from 60 to 80° C.; from 80 to 100° C.; from 100 to 120° C.; from 120 to 140° C.; from 140 to 160° C.; from 160 to 180° C.; from 180 to 200° C.
The expression “from 60 to 110° C.” corresponds to the following ranges: from 60 to 70° C.; from 70 to 80° C.; from 80 to 90° C.; from 90 to 100° C.; from 100 to 110° C.
The expression “from 2 to 24 hours” corresponds to the following ranges: from 2 to 5 hours; from 5 to 8 hours; from 8 to 12 hours; from 12 to 16 hours; from 16 to 20 hours; from 20 to 24 hours.
In a particular embodiment, the invention relates to a method as defined above, wherein reaction step A comprises bringing into contact an alcohol of Formula 1 to prepare an oxalate compound of Formula 2:
For the purposes of this invention, by “C1 to C20 linear or branched alkyl group” it is meant a saturated, linear or branched, acyclic carbon chain comprising 1 to 20 carbon atoms. These groups are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, cetyl, heptadecyl, octadecyl, nonadecyl and eicosyl. The definition of alkyl includes all possible isomers. For example, the term butyl includes n-butyl, iso-butyl, sec-butyl and ter-butyl. One or more hydrogen atoms may be replaced in the alkyl chain.
By “C3 to C10 cycloalkyl” it is meant: a C3 cyclopropyl group, a C4 cyclobutyl group, a C5 cyclopentyl group, a C6 cyclohexyl group, a C7 cycloheptyl group, a C8 cyclooctyl group, a C9 cyclononyl group, or a C10 cyclodecyl group, and fused cycloalkane rings such as adamantyl.
By “C5 to C20 alkylaryl” it is meant a group consisting of a linear or branched alkyl chain linked to an aromatic group, the alkylaryl group comprising 5 to 20 carbon atoms. The aryl groups according to the present invention can also be substituted, in particular by one or more substituents chosen from a C1 to C10 linear or branched alkyl group.
Phenyl, toluyl, anisyl and naphthyl o-tolyl, m-tolyl, p-tolyl, o-xylyl, m-xylyl, p-xylyl, are examples of aryl groups.
The term “heteroaryl” refers to an aryl group as defined above, comprising atoms other than carbon atoms, in particular N, O or S within the aromatic ring. Pyridyl, imidazoyl, furfuryl or furanyl are examples of heteroaryl groups according to the present invention.
In a particular embodiment, the invention relates to a method as defined above, wherein reaction step A comprises bringing into contact an alcohol of Formula 1 to prepare an oxalate compound of Formula 2:
According to a particular embodiment, the invention relates to a method as defined above, in which a purification step of said oxalate compound is carried out between reaction step A and reaction step B, in particular by distillation.
Advantageously, the oxalate compound purification step is carried out by distillation, extraction or recrystallisation in the purification step.
According to a particular embodiment, the invention relates to a method as defined above, in which, in reaction step B, the catalyst is used in an amount from 0.5 to 10 mmol, in particular in an amount of 4 mmol of Cu or Ag.
The expression “from 0.5 to 10 mmol” corresponds to the following ranges: from 0.5 to 1 mmol; from 1 to 2 mmol; from 2 to 3 mmol; from 3 to 4 mmol; from 4 to 5 mmol; from 5 to 6 mmol; from 6 to 7 mmol; from 7 to 8 mmol; from 8 to 9 mmol; from 9 to 10 mmol.
According to a particular embodiment, the invention relates to a method as defined above, in which, in reaction step B, the oxalate compound is used in an amount from 2 to 40 molar equivalents, in particular in a proportion of 5 equivalents, relative to the metal M of the catalyst. The expression “2 to 40 equivalents” corresponds to the following ranges: 2 to 5 equivalents; 5 to 10 equivalents; 10 to 15 equivalents; 15 to 20 equivalents; 20 to 25 equivalents; 25 to 30 equivalents; 30 to 35 equivalents; 35 to 40 equivalents.
According to a particular embodiment, the invention relates to a method as defined above, in which, in reaction step B, dihydrogen is used under a pressure from 1.0 to 8.0 MPa, in particular 5.0 MPa.
The expression “from 1.0 to 8.0 MPa” corresponds to the ranges: from 1.0 to 1.5 MPa; from 1.5 to 2.0 MPa; from 2.0 to 2.5 MPa; from 2.5 to 3.0 MPa; from 3.0 to 3.5 MPa; from 3.5 to 4.0 MPa; from 4.0 to 4.5 MPa; from 4.5 to 5.0 MPa; from 5.0 to 5.5 MPa; from 5.5 to 6.0 MPa; from 6.0 to 6.5 MPa; from 6.5 to 7.0 MPa; from 7.0 to 7.5 MPa; from 7.5 to 8.0 MPa.
According to a particular embodiment, the invention relates to a method as defined above, in which, in reaction step B, the solvent is selected from ethanol, methanol and dioxane, preferably ethanol or methanol.
According to a particular embodiment, the invention relates to a method as defined above, in which, in reaction step B, the reaction medium 2 is pressurised from 1.0 to 8.0 MPa, in particular 5 MPa.
According to a particular embodiment, the invention relates to a method as defined above, in which in reaction step B, the reaction medium 2 is heated to a temperature from 100 to 250° C., in particular 200 or 220° C., preferably during from 5 to 24 hours, more preferably during 8 or 16 hours.
The expression “from 100 to 250° C.” corresponds to the following ranges: from 100 to 120° C.; from 120 to 140° C.; from 140 to 160° C.; from 160 to 180° C.; from 180 to 200° C.; from 200 to 220° C.; from 220 to 250° C.
The expression “from 5 to 24 hours” corresponds to the following ranges: from 5 to 8 hours; from 8 to 12 hours; from 12 to 16 hours; from 16 to 20 hours; from 20 to 24 hours.
Reaction step B of the method of the invention is advantageously carried out without additives in the reaction medium.
Advantageously, the catalyst recovered after reaction step B of the invention is not degraded and is stable and in particular free from additives. It can advantageously be reused in another catalysed reaction step as a catalyst. It is therefore possible to repeat reaction step B according to the invention several times with the recovered catalyst or to use the catalyst recovered in reaction step B to carry out a reaction step A.
According to a particular embodiment, the invention relates to a method of preparation of ethylene glycol, as defined above, in which the catalyst is recovered at the end of a reaction step B and is reused as catalyst in another catalysed reaction step.
According to a particular embodiment, the invention relates to a method of preparation of ethylene glycol, as defined above, in which the catalyst is recovered at the end of a reaction step B and is reused as catalyst in another subsequent reaction step B.
Advantageously, the catalyst recovered at the end of a reaction step B can be used during several successive cycles of reaction steps B.
According to a particular embodiment, the invention relates to a method of preparation of ethylene glycol, as defined above, in which the catalyst is recovered at the end of a reaction step B and is reused as catalyst in a reaction step A.
According to a particular embodiment, the invention relates to a method of preparation of ethylene glycol as defined above, in which the catalyst used in reaction step A is a catalyst recovered at the end of a reaction step B.
According to a particular embodiment, the invention relates to method of preparation of ethylene glycol as defined above, in which the catalyst is recovered at the end of reaction step A and is reused as catalyst in reaction step B.
According to a particular embodiment, the invention relates to a method of preparation of ethylene glycol as defined above, in which the catalyst used in reaction step B is a catalyst recovered at the end of the reaction step A.
According to a particular embodiment, the invention relates to a method of preparation of ethylene glycol, as defined above, in which the catalyst is recovered at the end of a reaction step A and is reused as catalyst in a subsequent reaction step A.
Advantageously, the catalyst recovered at the end of a first reaction step A can be used during several successive cycles of reaction steps A.
According to a particular embodiment, the invention relates to a method of preparation as defined above, in which at least one of the reaction steps of the method is carried out in continuous flow, the catalyst being a heterogeneous Pd-M/Support catalyst according to the invention.
According to a particular embodiment, the invention relates to a method of preparation of ethylene glycol as defined above, at least one of the reaction steps being carried out in continuous flow,
By way of a non-limiting example, the continuous flow process is carried out in a reactor of the following type:
By way of example, the process according to the invention can be implemented in a flow chemistry apparatus, for example in commercial reactors such as “H-Cube Pro®” or “Phoenix®” from ThalesNano INC. (7 Zahony Street, Graphisoft Park, Building D, H-1031 Budapest, Hungary) or such as the “E-Series” or “R-Series flow chemistry systems” from Vapourtec Ltd (Unit 21/Park Farm Business Centre/Fornham Pk, Bury Saint Edmunds IP28 6TS, United Kingdom).
Advantageously, the continuous flow process is carried out at a temperature of 25° C. to 200° C.
Advantageously, the continuous flow process is carried out at a pressure from 0.1 MPa to 15 MPa, in particular from 0.1 to 4 MPa.
The expression “from 0.1 to 4 MPa” corresponds to the following ranges: from 0.1 to 0.5 MPa; from 0.5 to 1.0 MPa; from 1.0 to 1.5 MPa; from 1.5 to 2.0 MPa; from 2.0 to 2.5 MPa; from 2.5 to 3.0 MPa; from 3.0 to 3.5 MPa; from 3.5 to 4.0 MPa.
In a particular embodiment, the continuous flow process is carried out in a reactor in which the gases represent from 10 to 90% of the reactor volume.
The expression “from 10 to 90%” corresponds to the following ranges: from 10 to 20%; from 20 to 30%; from 30 to 40%; from 40 to 50%; from 50 to 60%; from 60 to 70%; from 70 to 80%; from 80 to 90%.
According to a particular embodiment, the continuous flow process is carried out by means allowing a contact time between the reagents from 1 second to 2 hours, in particular from 1 second to 2 minutes.
The expression “from 1 second to 2 hours” corresponds to the following ranges: from 1 to 15 seconds; from 15 to 30 seconds; from 30 seconds to 1 minute; from 1 to 2 minutes; from 2 to 15 minutes; from 15 to 30 minutes; from 30 minutes to 1 hour; from 1 to 2 hours.
According to a particular embodiment, the carbonylation reaction step A of the method is carried out in continuous flow and comprises means for introducing into the reactor the flow of CO in contact with the substrate (the alcohol) and the flow of oxygen individually or as a mixture.
According to a particular embodiment, the hydrogenation reaction step B of the method is carried out in continuous flow and comprises means for introducing into the reactor the flow of hydrogen in contact with the substrate (oxalate).
According to a particular embodiment, the carbonylation reaction step A of the method and the hydrogenation reaction step B of the method according to the invention as defined above are carried out in continuous flow and comprise means for introducing the gas flow in contact with the substrate into the reactor.
According to a particular embodiment, the carbonylation reaction step A of the process and the hydrogenation reaction step B of the method according to the invention as defined above are carried out in the same reactor.
The activity of the catalyst according to the invention can be described in terms of “Number of Catalytic Cycles (NCC)”.
The “Number of Catalytic Cycles (NCC)” is defined as the ratio between the number of moles of product formed (nprod) and the number of moles of active catalyst species (ncat).
In the case of the carbonylation reaction, the NCC is defined as the ratio between the number of moles of product formed (nprod) and the number of moles of palladium in the catalyst (ncat).
In the case of the hydrogenation reaction, the NCC is defined as the ratio between the number of moles of product formed (nprod) and the number of moles of copper in the catalyst (ncat).
The NCC is calculated as follows:
Unlike the Turnover Number (TON), which represents the maximum number of catalytic cycles that a catalyst can achieve before its total and irreversible degradation, the Catalytic Cycle Number represents the total number of catalytic cycles achieved by the catalyst under given reaction conditions. At the end of the reaction, the catalyst used would not necessarily be degraded and could therefore be reused. The NCC is therefore not a measure of the lifetime of a catalyst, but a measure of the productivity of the catalyst under the given conditions of the catalysed reaction.
The chemical yield indicates the efficiency of the chemical reaction under study. The yield is the ratio between the quantity of product obtained and the maximum quantity that would be obtained if the reaction were complete.
The yield of reaction step B for hydrogenating oxalate to ethylene glycol according to the invention is determined as a percentage of moles of ethylene glycol obtained per mole of oxalate.
The yield of reaction step B for hydrogenating oxalate to ethylene glycol, can be determined using gas chromatography-mass spectrometry (GC-MS), in which mesitylene is used as an internal standard.
Yield can also be assessed by determining the quantity of product after purification to isolate the product.
According to a particular embodiment, the invention relates to the use as defined above, wherein said hydrogenation reaction step B has a yield of more than 70%, preferably more than 75%, preferentially more than 90%.
The selectivity of a chemical reaction specifies the quantity of the desired product formed in relation to the number of moles consumed of the limiting reagent. It indicates whether several reactions are occurring in parallel, leading to unwanted by-products, or whether the reaction being carried out is the only one to consume reagent.
In the case of reaction step B, the selectivity is defined as the quantity of ethylene glycol obtained relative to the total quantity of products obtained, comprising ethylene glycol and the secondary by-products resulting from the conversion of the oxalate compound.
According to a particular embodiment, the invention relates to a method as defined above, wherein said method for preparing ethylene glycol is selective, with a selectivity of more than 70%, preferably more than 75%, more preferably more than 90%.
The expression “selective method of preparation” refers to a method enabling the product in question, ethylene glycol, to be obtained with a selectivity of more than 50%.
The expression “more than 70%” corresponds to the following ranges: more than 70%; more than 80%; more than 90%.
The expression “more than 75%” corresponds to the following ranges: more than 75%; more than 80%; more than 85%; more than 90%; more than 95%.
The expression “more than 90%” corresponds to the following ranges: more than 90%; more than 91%; more than 92%; more than 93%; more than 94%; more than 95%; more than 96%; more than 97%; more than 98%; more than 99%.
According to a particular embodiment, the invention relates to a method as defined above, in which the first catalysed reaction step A of oxidative carbonylation, from an alcohol, carbon monoxide and an oxidant, in particular molecular oxygen, optionally in the presence of a promoter, to form an oxalate compound as reaction intermediate, is selective, with a selectivity of more than 70%, preferably more than 75%, more preferably more than 90%.
The expression “selective oxidative carbonylation reaction step” refers to a carbonylation reaction step that makes it possible to obtain the target product, the oxalate compound, with a selectivity of more than 70%.
According to a particular embodiment, the invention relates to the method as defined above, in which the second catalysed reaction step B of hydrogenation of the said oxalate compound by hydrogen to obtain ethylene glycol is selective, with a selectivity of more than 70%, preferably more than 75%, preferentially more than 90%.
The expression “selective hydrogenation reaction step” refers to a hydrogenation reaction step that makes it possible to obtain the target product, ethylene glycol, with a selectivity of more than 70%.
According to a particular embodiment, the invention relates to a method as defined above, in which the first catalysed reaction step A of oxidative carbonylation, starting from an alcohol, carbon monoxide and an oxidant, in particular molecular oxygen, optionally in the presence of a promoter, to form an oxalate compound as reaction intermediate, and the second catalysed reaction step B of hydrogenation of the said oxalate compound by hydrogen to obtain ethylene glycol, are selective, with a selectivity of more than 70%, preferably more than 75%, preferentially more than 90%.
The expression “selective reaction step” refers to a reaction step that makes it possible to obtain the target product, the oxalate compound or the ethylene glycol, with a selectivity of more than 70%.
According to a particular embodiment, the invention relates to a method as defined above, in which:
Another object of the invention concerns a bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula Pd—Cu/ZrO2, comprising:
The inventors have unexpectedly observed that bimetallic catalysts of palladium and copper on a zirconium dioxide support with a low specific surface area of approximately 5 m2/g are more efficient than a catalyst with a higher specific surface area of 63 m2/g or 81 m2/g. This efficiency applies to both the carbonylation reaction (step A) and the hydrogenation reaction (step B) for the preparation of ethylene glycol, making it possible in particular for the hydrogenation reaction to achieve a yield of 92% and a selectivity of 94%, as revealed in the results of example 24. In fact, it would be expected that a specific surface area greater than 50 m2/g would allow greater accessibility to the substrates and favour the yields of the catalyst.
In a particular embodiment, the invention relates to a bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula Pd—Cu/ZrO2, as defined above further comprising:
For the purposes of this invention, by “baddeleyite” it is meant a natural zirconium oxide of formula ZrO2, containing from 0.1% to 5% hafnium oxide, and crystallising in a monoclinic crystal system. The characteristics of baddeleyite, such as its composition and crystallographic structure, in particular the space group with the dimensions of the crystal lattice, are reported and available in the prior art and are known to those skilled in the art, such as Kudoh, Y. et al, (Phys Chem Minerals 13, 233-237 (1986)) or Mccullough J D. et al (Acta Crystallographica 12 (1959) 507-511).
In a particular embodiment, the crystalline phase of zirconium dioxide comprises impurities such as Hafnium (Hf) atoms.
From 20 to 100 nm refers to the following ranges: from 20 to 30 nm; from 30 to 40 nm; from 40 to 50 nm; from 50 to 60 nm; from 60 to 70 nm; from 70 to 80 nm; from 80 to 90 nm; from 90 to 100 nm.
In another particular embodiment, the invention concerns a bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula Pd—Cu/ZrO2, as defined above, in the form of two populations of particles:
For the purposes of this invention, by “polyhedral-type particles” it is meant particles with edges, corners or bevelled edges.
For the purposes of this invention, by “particles with a rounded morphology” it is meant particles that do not have an edge, corner or a bevelled edge.
For the purposes of this invention, “entangled particles” meant rounded particles agglomerated together or having a fused appearance, forming a visible surface of protuberances,
For the purposes of this invention, by “particle cluster” it is meant a set of entangled particles that are either visually or mechanically coherent with one another.
In a particular embodiment, the invention relates to a bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula Pd—Cu/ZrO2, as defined above, further comprising:
Advantageously, the molar quantity of copper atoms in an oxidation state (I) is greater than that of copper atoms in an oxidation state (II).
Pd—Ag/γ-Al2O3 Catalyst
Another object of the invention relates to a bimetallic catalyst of palladium and silver on an alumina support of formula Pd—Ag/γ-Al2O3, comprising:
For the purposes of this invention, “porous morphology with a honeycomb appearance” means a visible morphology of a set of craters with common edges in the form of ridges.
Pd—Cu/γ-Al2O3 catalyst
Another object of the invention relates to a bimetallic catalyst of palladium and copper on an alumina support of formula Pd—Cu/γ-Al2O3 catalyst, comprising:
Another object of the invention relates to a method of preparation of a catalyst of formula Pd-M/Support, comprising palladium and a metal M on an oxide support, in which M represents Cu or Ag, comprising:
Advantageously, the palladium salt is palladium nitrate and the copper or silver salt is copper or silver nitrate.
The inventors have surprisingly found that the method of preparation makes it possible to obtain active and effective catalysts for the two reactions of carbonylation of alcohol to oxalate and hydrogenation of oxalate to ethylene glycol in the ethylene glycol preparation process, without the need for a preliminary step of reducing the metal atoms Pd, Cu or Ag under a flow of hydrogen.
In a particular embodiment, the invention relates to a method of preparation of a Pd—Cu/ZrO2 catalyst according to the catalyst of the invention as defined above, comprising:
Advantageously, said support used to prepare the catalyst is a zirconium dioxide with a specific surface area from 1 to 50 m2/g, in particular from 1 to 10 m2/g, preferably from 5 to 7 m2/g.
Advantageously, said support used for preparing the catalyst is a zirconium dioxide crystallised in monoclinic baddeleyite and comprises a crystallite size from 20 to 100 nm, preferably from 20 to 50 nm, and a specific surface area from 1 to 50 m2/g, in particular from 1 to 10 m2/g, preferably from 5 to 7 m2/g, and optionally comprises hafnium atoms as impurities.
In a particular embodiment, the invention relates to a method of preparation of a Pd—Ag/γ-Al2O3 catalyst, comprising:
Another object of the invention relates to a supported bimetallic catalyst of formula Pd-M/Support, comprising palladium and a metal M on a support, in which M represents Cu or Ag, obtainable by a method of preparation of a catalyst as defined above.
In a particular embodiment, the invention relates to a bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula Pd—Cu/ZrO2, obtainable by a method of preparation of a catalyst as defined above.
According to one embodiment, the invention relates to a bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula Pd—Cu/ZrO2, obtainable by a preparation process comprising:
In a particular embodiment, the invention relates to a bimetallic catalyst of palladium and silver on an alumina support (γ-Al2O3) of formula Pd—Ag/γ-Al2O3, obtainable by a method of preparation of a catalyst as defined above.
Another object of the invention concerns a bimetallic catalyst of palladium and copper on a zirconium dioxide support of formula Pd—Cu/ZrO2, comprising:
The following examples and figures illustrate the invention, without limiting its scope.
The ZrO2 support, with a specific surface area of 5 to 7 m2/g, is supplied by Sterm Chemicals (15 Rue de l'Atome, 67800 Bischheim) (product number 93-4013. Without further clarification, hereafter the support named ZrO2 is that supplied by Sterm Chemicals.
The ZrO2 support (monoclinic phase), with a specific surface area greater than 85 m2/g is supplied by Alfa Aesar (Thermo Fisher Scientific) with product number AA4381522.
The γ-Al2O3 support is supplied by Sterm Chemicals (15 Rue de l′Atome, 67800 Bischheim) with reference number 13-2525.
The SiO2 support (40-63 μm) was supplied by VWR chemicals, reference number 151125P. Palladium nitrate (Pd(NO3)2·xH2O) and other metal salts such as Cu(NO3)2·3H2O, AgNO3 were supplied by Fischer.
The 450 mL and 1 L autoclaves are supplied by Parr Instrument Company.
Pd(NO3)2·xH2O was dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of zirconium dioxide support and the resulting paste of ZrO2 was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80° C. for 16 hours and calcined at 600° C. for 2 hours to obtain the catalyst.
Cu(NO3)2·3H2O was dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of zirconium dioxide support and the resulting paste of ZrO2 was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80° C. for 16 hours and calcined at 600° C. for 2 hours to obtain the catalyst.
Pd(NO3)2·xH2O and Cu(NO3)2·3H2O were dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of zirconium dioxide support and the resulting paste of ZrO2 was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80° C. for 16 hours and calcined at 600° C. for 2 hours to obtain the catalyst.
Table 1 below reports the preparation conditions for the Pd/ZrO2, Cu/ZrO2 and Pd—Cu/ZrO2 catalysts prepared according to examples 2, 3 and 4.
Pd(NO3)2·xH2O and Cu(NO3)2·3H2O were dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of γ-Al2O3 support and the paste obtained was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80° C. for 16 hours and calcined at 600° C. for 2 hours to obtain the catalyst.
Table 2 below reports the conditions for preparing a Pd—Cu/γ-Al2O3 catalyst prepared according to example 6.
AgNO3 was dissolved in a minimum volume of demineralised water, between 5 and 10 mL, to form a solution. This solution containing the metal precursors was added to the appropriate amount of γ-Al2O3 support and the paste obtained was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80° C. for 16 hours and calcined at 600° C. for 2 hours to obtain the catalyst.
Pd(NO3)2·xH2O and AgNO3 were dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of support γ-Al2O3 and the paste obtained was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80° C. for 16 hours and calcined at 600° C. for 2 hours to obtain the catalyst.
Table 3 below reports the preparation conditions for the Ag/γ-Al2O3 and Pd—Ag/γ-Al2O3 catalysts prepared according to examples 8 and 9.
Pd(NO3)2·xH2O and AgNO3 were dissolved in a minimum volume of demineralised water, between 5 and 10 mL, forming a solution. This solution containing the metal precursors was added to the appropriate amount of SiO2 support and the paste obtained was mixed at room temperature until a homogeneous material was obtained. The material was then dried at 80° C. for 16 hours and calcined at 600° C. for 2 hours to obtain the catalyst.
Table 4 below reports the conditions for preparing a Pd—Ag/SiO2 catalyst prepared according to example 10.
A heterogeneous palladium catalyst (0.24 mmol Pd), tetrabutylammonium iodide TBAI (554 mg, 1.5 mmol) as promoter, tri-ethylamine Et3N (0.14 mL, 1.0 mmol), acetonitrile (50 mL) and methanol (25 mL) were introduced into a 450 mL Parr autoclave equipped with a magnetic stirrer. The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bar) and twice with oxygen (5 bar).
The autoclave was then pressurised with 15 bars of oxygen and a further 65 bars of carbon monoxide (total pressure of 80 bars). The reaction medium was then stirred at 90° C. for 16 h.
Once the reaction was complete, the autoclave was brought to room temperature before being depressurised and purged three times with nitrogen (5 bar).
The final mixture obtained was then filtered and transferred to a 250 mL flask.
The reaction solvent and excess alcohol were separated by evaporation on a rotary evaporator.
The diethyloxalate was recovered after purification by recrystallisation in di-ethyl ether and the isolated yields were calculated.
For reactions in which the alcohol is used as a substrate in the presence of a solvent and also for reactions carried out in the absence of a solvent in which the alcohol plays the role of both substrate and solvent, the results are described in NCC in order to assess the catalytic efficiency, particularly due to the use in excess of alcohol as a substrate.
The NCC is calculated as follows:
NCC=number of moles of product formed/number of moles of Pd
A heterogeneous palladium catalyst (0.24 mmol Pd), tetrabutylammonium iodide TBAI (1.5 to 3.6 mmol), tri-ethylamine Et3N (1.0 to 4.75 mmol), optionally acetonitrile MeCN (0 to 50 mL) as solvent and ethanol (25 to 75 mL) were introduced into a 450 mL Parr autoclave equipped with a magnetic stirrer. The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bar) and twice with oxygen (5 bar).
The autoclave was then pressurised with 15 bars of oxygen and a further 65 bars of carbon monoxide (total pressure of 80 bars). The reaction medium was then stirred at 90° C. for 16 h.
Once the reaction was complete, the autoclave was brought to room temperature before being depressurised and purged three times with nitrogen (5 bar).
The final mixture obtained was then filtered and transferred to a 250 mL flask.
The reaction solvent and the excess alcohol were separated by evaporation on a rotary evaporator.
The diethyloxalate was recovered after purification by vacuum distillation at 120° C./50-20 mbar and the isolated yields were calculated.
A heterogeneous copper or silver catalyst (4 mmol Cu or Ag), dialkyloxalate (20 mmol) and ethanol (50 mL) were introduced into a 450 mL Parr autoclave equipped with a magnetic stirrer.
The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bar) and twice with hydrogen (5 bar).
The autoclave was then pressurised with 50 bars of hydrogen. The reaction medium was then stirred at 200° C. for 16 h or 220° C. for 8 h.
Once the reaction was complete, the autoclave was brought to room temperature before being depressurised and purged three times with nitrogen (5 bar).
The final mixture obtained was diluted in ethanol or methanol and then an internal standard was added (mesitylene) to calculate the yield by using GC-MS.
Tables 5 and 6 below report respectively the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with a Pd/ZrO2 catalyst.
Tables 7 and 8 below report respectively the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with a Cu/ZrO2 catalyst.
Tables 9 and 10 below respectively report the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with a Ag/γ-Al2O3 catalyst.
Tables 11 and 12 below report respectively the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with Pd—Cu catalysts on ZrO2 and on γ-Al2O3 supports.
Tables 13 and 14 below report respectively the test conditions of oxidative carbonylation (reaction step A) and of hydrogenation (reaction step B) with Pd—Ag/γ-Al2O3 or SiO2 catalyst.
After one hydrogenation reaction of dialkyl oxalates, the catalyst (Cu or Ag) is separated from the liquid reaction medium by filtration. The catalyst was then washed with 3×25 mL ethanol. The material was then dried at 80° C. for 4 h before being used again in a hydrogenation reaction of dialkyl oxalate.
Tables 15 and 16 below report respectively the test conditions of hydrogenation (reaction step B) and the recycling results according to example 19.
Table 17 below reports the results of oxidative carbonylation tests (reaction step A) with variations in the conditions (nature of the base, additive, O/CO2 pressure, reaction time, quantity of catalyst and substrate) compared with the general procedure according to example 12 with a Pd(2%)Cu(10%)/ZrO2 catalyst prepared according to example 5.
The carbonylation yield was calculated using GC-MS, with chlorobenzene used as an internal standard.
Tests were carried out in a one-litre reactor.
A heterogeneous catalyst based on palladium Pd(2%)Cu(10%)/ZrO2 (0.54 mmol Pd), NaI (0.252 g, 1.68 mmol), tri-ethylamine (0.630 mL, 4.5 mmol), and ethanol (225 mL) were introduced into a 1 L Parr autoclave equipped with a magnetic stirrer. The reactor was sealed and the reaction mixture was purged three times with nitrogen (5 bar), and twice with oxygen (5 bar). The autoclave was then pressurised with 15 bar of oxygen and a further 65 bar of carbon monoxide (total pressure 80 bar). The reaction mixture was then stirred at 90° C. for 16 h. Once the reaction was complete, the autoclave was allowed to return to room temperature before being depressurised and purged three times with nitrogen (5 bar). The reaction mixture was then filtered and the recovered solution transferred to a 500 mL flask. The reaction solvent and the excess alcohol were separated by evaporation on a rotary evaporator. The oxalate was recovered after purification (vacuum distillation at 120° C./50-20 mbar for the diethyloxalate) and the isolated yields were calculated.
Tests A7-1 and A7-3 were carried out with variations in the concentrations of the catalyst, base, additive or substrate (ethanol) compared with the preparation conditions for test A7-2 described above.
Table 18 below reports the conditions and results of oxidative carbonylation tests (reaction step A) in a one-litre Parr autoclave, using a Pd(2%)Cu(10%)/ZrO2 catalyst prepared according to example 5.
In order to determine the influence of the ZrO2 support and of the preparation of the catalysts, Cat B and Cat C catalysts were produced using another zirconium dioxide support, ZrO2, consisting of a monoclinic crystalline phase, called hereinafter ZrO2 (monoclinic phase) marketed by Alpha Aesar.
The ZrO2 support (monoclinic phase) is identical to that used by Yuqing et al (Chinese Journal of Catalysis, 36, 2015, 1552-1559).
The Pd(2%)Cu(10%)/ZrO2 catalyst, hereafter referred to as Cat A, prepared according to example 5 was compared with Cat B and Cat C catalysts of the same nature but using a support with different characteristics or a different preparation.
The Pd(2%)Cu(10%)/ZrO2 (monoclinic phase), hereinafter referred to as Cat B, was prepared according to example 5 using the ZrO2 support (monoclinic phase), supplied by Alfa Aesar (Thermo Fisher Scientific) with product number 43815, having a specific surface area greater than 85 m2/g.
The Pd(1%)Cu(3%)/ZrO2 catalyst (monoclinic phase), referred to hereafter as Cat C, was prepared with the ZrO2 support (monoclinic phase), supplied by Alfa Aesar, according to that described by the article Yuqing Jia et al. (Chinese Journal of Catalysis, 36, 2015, 1552-1559), namely in two successive steps:
Tables 19 and 20 below show respectively the conditions and yield results for the oxidative carbonylation (reaction step A) and hydrogenation (reaction step B) tests using Cat A, Cat B and Cat C catalysts.
These results indicate a higher yield of the carbonylation of ethanol to diethyloxalate (step A) with a yield of 5.7 g and of the hydrogenation of oxalate to ethylene glycol (step B) with a yield of 92% and a selectivity of 94% for catalyst Cat A of the invention. 10
Cat B and Cat C catalysts, prepared with a ZrO2 support from Alfa Aesar, are less efficient for carbonylation in terms of yield, but also for the hydrogenation step, with yields of 61% and 37% and selectivities of 70% and 35% respectively. In particular, Cat C catalyst prepared according to Yuqing Jia et al. is the least efficient in terms of carbonylation yield (step A) and in particular in terms of hydrogenation yield and selectivity (step B), which are 2.5 times lower than those of Cat A.
The specific surface area of Cat A, Cat B and Cat C catalysts was measured by BET. The results are shown in Table 21 below.
X-ray powder diffractograms of Cat A, Cat B and Cat C catalysts were carried out using a Rigaku MINIFLEX II diffractometer, which emits X-rays via a tube and a copper source (wavelength Kα 1.54 Å).
The results of the analysis of the various diffractograms obtained for Cat A, Cat B and Cat C catalysts are presented respectively in Tables 22, 23 and 24 below.
The diffractograms show the presence of crystallised phases.
The XRD analyses indicate that the same crystalline baddeleyite phase (ZrO2) is present in all three catalysts with the presence of a palladium oxide phase. In the case of Cat A and Cat B catalysts, copper monoxide and palladium phases in metallic state are observed.
The diffraction peaks of Cat A and Cat B catalysts can be distinguished from the peaks of the Baddeleyite phase of the support. Cat A peaks are narrower in width than Cat B peaks.
The crystallinity of materials is characterised by the size of the crystallites.
The crystallite size was qualitatively estimated in order to compare the different ZrO2 supports of Cat A and Cat B catalysts. As a reminder, Cat B and Cat C catalysts were prepared using ZrO2 support identical to that used in Yuqing Jia et al. (Chinese Journal of Catalysis, 36, 2015, 1552-1559) marketed by Alfa Aesar.
The size of the crystallites was evaluated using the following Scherrer formula:
The width at half-height was estimated using ImageJ processing software (developed by the National Institutes of Health).
The crystallite size calculations from Cat A and Cat B diffractograms are shown in Table 25 below:
The support used in Yuqing Jia et al. is a commercial ZrO2 oxide powder from Alfa Aesar, with a pore volume of 0.27 cc/g and a specific surface area more than 85 m2/g (BET).
The low value of the sizes, in particular less than 10 nanometres, is an indicator of a low crystallinity structure. The smaller the crystallites, the wider the diffraction peaks. This effect becomes visible for crystallites less than 1 μm in diameter.
The results indicate that the catalyst prepared with Sterm's ZrO2 support and the catalysts prepared with Alfa Aesar's ZrO2 support have crystallite sizes of 31 nm and 9 nm respectively. Cat A and Cat B catalysts are thus distinguished by the microstructure of ZrO2 support.
In addition to the characteristic related to the specific surface area, these results show that Cat A and Cat B catalyst supports are different in terms of their microstructure.
Thus, as shown in Examples 17, 21 and 24, catalysts prepared with a ZrO2 support having a crystallite size of about 30 nm used for steps A and B of ethylene glycol preparation are more efficient than PdCu/ZrO2 catalysts prepared with a more polycrystalline and lower crystallinity ZrO2 support having a crystallite size of about 9 nm.
The SEM images in
The sample was stabilised on carbon adhesive paper to enable SEM observation. It should therefore be noted that the content of the element carbon can be associated with the use of the latter.
Quantification was carried out by EDX spectrum analysis on sample areas of the catalysts. The results are expressed as a percentage by mass.
The results of the SEM observations and EDX analysis are summarised below.
SEM images are shown in
The EDX analysis of one zone of the sample is shown in Table 26. The particles are composed mainly of zirconium (Zr), oxygen (O) and copper (Cu) and to a lesser extent of palladium (Pd), hafnium (Hf) and carbon.
SEM observations of Pd(2%)/ZrO2 catalyst prepared with Sterm's ZrO2 support reveal a morphology similar to that of Cat A catalyst, namely entangled elongated particles of heterogeneous thickness less than one micrometre forming clusters.
The EDX analysis of two zones of the sample is shown in Table 27.
These particles are composed mainly of copper (Cu), zirconium (Zr), palladium (Pd) and oxygen (O), with a minority of carbon (C) and traces of hafnium (Hf) and rhenium (Re).
SEM observations reveal the presence of micrometric particles with a polyhedral morphology and nanometric particles.
The EDX analysis of one zone of the sample is shown in Table 28.
These particles are composed mainly of zirconium (Zr), oxygen (O) and copper (Cu), and to a lesser extent carbon (C), hafnium (Hf) and rhenium (Re), with traces of palladium (Pd).
Catalyst Pd(2%)Cu(10%)/γ-Al2O3
Catalyst Pd(2%)Ag(15%)/γ-Al2O3
Analyses are carried out using a PHI QUANTES photoemission spectrometer. This instrument is equipped with a monochromate X-ray source (aluminium Kα line) as well as a chromium X-ray source for Hard XPS, a charge neutralisation system for electrically insulating samples and a hemispherical electron analyser.
XPS analyses were carried out on:
Analysis of the XPS spectra over several zones reveals a variation of the satellite typical for CuO (around 940-945 eV), indicating the presence of a mixture of Cu+ and Cu2+.
The Cu+ concentration is higher because Auger signal is dominated by this component (916.8 eV). The presence of metallic Cu cannot be detected either on the Cu2p spectrum or on the Auger spectrum. If it is present, it is masked by the signals corresponding to Cu+.
Pd3d is interfered by Zr3p signal. A reference ZrO2 powder was measured in order to extract the Zr3p signal, i.e. Zr3p3 at 332.9 eV and Zr3p1 at 346.61 eV.
The presence of Pd2+ is confirmed by the corresponding Pd3d5/2 signal (located at 337.5 eV) which is visible.
The Zr3d spectra overlap, at least in energy. The width is slightly greater, which may be due to differential charging. This correspondence of binding energies should be found in the case of Pd3d.
Pd3d is interfered by Zr3p signal. The presence of Pd2+ is certain, as the corresponding Pd3d5/2 signal (located at 337 eV) is visible.
Pd(2%)Cu(10%)/γ-Al2O3 (See Spectrum in
Cu2p spectra mainly show the presence of Cu2+ in the form of oxide and hydroxide (based on the appearance of the satellite).
Pd3d spectra are identical for the two zones measured.
Pd3d5/2 component is located at 337.5 eV.
Pd(2%)Ag(15%)/γ-Al2O3 (See Spectrum in
Ag3d spectrum was difficult to interpret and required comparison with reference spectra (metallic Ag spectrum). An analysis of the Auger signals shows that it is a mixture of Ag oxides (I and II).
For Pd3d spectrum, the energy position is slightly lower at 337.2 eV, with an additional component at lower binding energy; Pd3d peaks for the sample are wider. There is therefore a difference of 0.3 eV in the position of Pd5/2 peak between the two samples.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2113380 | Dec 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/085704 | 12/13/2022 | WO |
