WO2020124433A1 - Process for preparing acetals or ketals - Google Patents

Process for preparing acetals or ketals Download PDF

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WO2020124433A1
WO2020124433A1 PCT/CN2018/122078 CN2018122078W WO2020124433A1 WO 2020124433 A1 WO2020124433 A1 WO 2020124433A1 CN 2018122078 W CN2018122078 W CN 2018122078W WO 2020124433 A1 WO2020124433 A1 WO 2020124433A1
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metal
alcohol
process according
organic framework
mof
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Songwei Zhang
Vitaly ORDOMSKY
Tao Li
Willinton Yesid HERNANDEZ ENCISO
Stéphane STREIFF
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Centre National de la Recherche Scientifique CNRS
Rhodia Operations SAS
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Rhodia Operations SAS
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D317/00—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms
    • C07D317/08—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3
    • C07D317/10—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings
    • C07D317/14—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings with substituted hydrocarbon radicals attached to ring carbon atoms
    • C07D317/18—Radicals substituted by singly bound oxygen or sulfur atoms
    • C07D317/22—Radicals substituted by singly bound oxygen or sulfur atoms etherified
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/46—Ruthenium, rhodium, osmium or iridium
    • B01J23/462—Ruthenium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/1691—Coordination polymers, e.g. metal-organic frameworks [MOF]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/22—Organic complexes
    • B01J31/2204—Organic complexes the ligands containing oxygen or sulfur as complexing atoms
    • B01J31/2208—Oxygen, e.g. acetylacetonates
    • B01J31/2226—Anionic ligands, i.e. the overall ligand carries at least one formal negative charge
    • B01J31/223—At least two oxygen atoms present in one at least bidentate or bridging ligand
    • B01J31/2239—Bridging ligands, e.g. OAc in Cr2(OAc)4, Pt4(OAc)8 or dicarboxylate ligands
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D319/00—Heterocyclic compounds containing six-membered rings having two oxygen atoms as the only ring hetero atoms
    • C07D319/04—1,3-Dioxanes; Hydrogenated 1,3-dioxanes
    • C07D319/06—1,3-Dioxanes; Hydrogenated 1,3-dioxanes not condensed with other rings
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D407/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00
    • C07D407/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00 containing two hetero rings
    • C07D407/04—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00 containing two hetero rings directly linked by a ring-member-to-ring-member bond
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D407/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00
    • C07D407/14—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen atoms as the only ring hetero atoms, not provided for by group C07D405/00 containing three or more hetero rings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
    • B01J2231/70—Oxidation reactions, e.g. epoxidation, (di)hydroxylation, dehydrogenation and analogues
    • B01J2231/76—Dehydrogenation
    • B01J2231/763—Dehydrogenation of -CH-XH (X= O, NH/N, S) to -C=X or -CX triple bond species
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
    • B01J2531/02—Compositional aspects of complexes used, e.g. polynuclearity
    • B01J2531/0213—Complexes without C-metal linkages
    • B01J2531/0216—Bi- or polynuclear complexes, i.e. comprising two or more metal coordination centres, without metal-metal bonds, e.g. Cp(Lx)Zr-imidazole-Zr(Lx)Cp
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
    • B01J2531/60—Complexes comprising metals of Group VI (VIA or VIB) as the central metal
    • B01J2531/62—Chromium

Definitions

  • the present invention relates to a process for the preparation of acetals or ketals.
  • Acetal/ketal the pivotal compounds in the manufacture of pharmaceutical products and detergent products and fuel additives etc., are commonly prepared through the acetalization reaction of aldehyde/ketone and alcohol.
  • J. AM. CHEM. SOC. 2009, 131, 3146–3147 reports direct dehydrogenation of alcohols to acetals and H 2 in neutral media by an acridine-based ruthenium pincer complex. Disadvantageously, this reaction needs high reaction temperature and long reaction time, which is more than 26 hours.
  • Cisokawa Patent Publication No. 103113347A discloses a method for preparing acetals or ketals under catalytic action of metal-organic frameworks (hereinafter MOFs) .
  • MOFs metal-organic frameworks
  • the metal-organic framework compound has a structure as follow:
  • the present invention therefore pertains to a process for preparing an acetal or ketal by reacting Alcohol I, Alcohol II and oxygen in the presence of a metal-organic framework (MOF) catalyst, wherein:
  • Alcohol I is an alcohol comprising one or more primary hydroxyl group (s) and/or one or more secondary hydroxyl group (s) ;
  • Alcohol II is an alcohol comprising two and only two hydroxyl groups
  • the metal-organic framework catalyst is a metal-organic framework, in which elemental metal and/or metal compound nanoparticles are embedded;
  • the metal of elemental metal or metal compound is selected from the group consisting of Ru, Pd, Pt, Ag, Au and Cu.
  • Fig. 1 is a TEM image of Ru@MIL 101 (Cr) of Example 2.
  • Fig. 2 is an image of enlargement view of Fig. 1. The nanoparticle is highlighted by a circle.
  • Fig. 3A-3D are TEM-EDX images of Ru@MIL 101 (Cr) of Example 2.
  • Fig. 4 is an image of N 2 adsorption-desorption isotherm curves of MIL 101 (Cr) and Ru@MIL 101 (Cr) of Example 2.
  • Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
  • Metal-organic frameworks are compounds consisting of metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures.
  • MOFs are crystalline structures comprising repeating metal building units connected by linking ligands via metal-ligands bonds.
  • the MOF materials exhibit analogous properties to that of conventional microporous and mesoporous materials such as large and accessible surface areas with interconnected intrinsic micropores or mesopores.
  • the MOFs of the invention have very high surface area per unit volume and very high porosities.
  • the pore size may be controlled with the choice of linking ligand. With a given topology, progressively increasing the length of the linking ligand usually results in larger pore size.
  • the aperture size and pore size of the MOF should be larger than the kinetic diameter of the reagents.
  • the pore size of the MOF used in the process according to the present invention is from 0.4 to 5 nm and preferably from 0.5 to 2 nm.
  • the method for analyzing the pore size can be gas adsorption analysis which uses N 2 as the adsorbate and 77.3K as sorption temperature. Specifically, Belsorb MAX II was used for the gas adsorption analysis. Sorption was measured down to 10 -8 bar. BelMASTER software was used for data processing. Grand Canonical Monte Carlo (GCMC) with no fitting assumption was used for pore size distribution analysis based on the experimental data. Cylindrical pore model should be used.
  • GCMC Grand Canonical Monte Carlo
  • the average particle size of elemental metal and/or metal compound nanoparticles embedded in MOF is from 0.5 to 20 nm and preferably from 0.5 to 2 nm, which is measured using transmission electron microscopy (TEM) .
  • TEM transmission electron microscopy
  • magnification factor had a range of '10,000 ⁇ '600,000. For 50 nm: magnification factor was 40,000 ⁇ 50,000; for 20 nm: 60,000 ⁇ 120,000; for 10 nm: 250,000; for 5 nm: 400,000; for 2 nm: 500,000 ⁇ 600,000. Samples of 0.1 wt. %nanoparticles in methanol suspension were measured. The obtained results were analyzed using the DigitalMicrograph software.
  • the average particle size of the MOF catalyst is from 10 nm to 100 ⁇ m and preferably from 100 nm to 1 ⁇ m, which is measured using transmission electron microscopy (TEM) .
  • TEM transmission electron microscopy
  • the methods for analyzing the MOF particle size is TEM.
  • the materials of use for the present invention include MOFs with metal building units which may be metal ions or metal cluster building units where the metal of the metal building units is selected from the transition metals or IIIA group metals.
  • the metal of the metal building units is selected from the group consisting of Al, Cr, Zr, Sc, Hf, Ti, Cu, Co, In, Fe, Ni, Zn and V, more preferably selected from the group consisting of Al, Cr, Zr, Sc, Hf, Ti and Fe, and most preferably Al or Cr.
  • metals of group IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB are often referred to as transition metals.
  • This group comprises the elements with atomic number 21 to 30 (Sc to Zn) , 39 to 48 (Y to Cd) , 72 to 80 (Hf to Hg) and 104 to 112 (Rf to Cn) .
  • linking ligands organic compounds known as linking ligands to form a porous crystalline structure.
  • a skilled person will recognize the compounds available for use as linking ligands are numerable, such as those described in Nature volume 423, pages 705–714 (12 June 2003) .
  • linking ligand is not particularly limited.
  • Preferred linking ligands for linking the adjacent metal building units is carboxylate-based ligands, which include 1, 3, 5-benzenetribenzoate (BTB) : 1, 4-benzenedicarboxylate (BDC) ; cyclobutyl 1, 4-benzenedicarboxylate (CB BDC) : 2-amino 1, 4 benzenedicarboxylate (H 2 N-BDC) ; 4, 5, 9, 10-tetrahydropyrene-2, 7-dicarboxylate (HPDC) ; terphenyl dicarboxylate (TPDC) ; 2, 6-naphthalene dicarboxylate (NDC) ; pyrene 2, 7-dicarboxylate (PDC) ; biphenyl dicarboxylate (BDC) ; or any di-, tri-, or tetracarboxylate containing phenyl rings.
  • BTB 4-benzenedicarboxylate
  • CB BDC 2-
  • the MOFs according to the present invention are MIL MOF, UiO-type MOF, MOF-808 etc.
  • MIL MOF examples include: MIL100, MIL101.
  • Preferred examples of MIL MOF are as follows:
  • UiO-type MOF Preferred example of UiO-type MOF is as follow:
  • MOF-808 Preferred example of MOF-808 is as follow:
  • MOFs Functionalization of the MOF to embed elemental metal and/or metal compound nanoparticles is performed after synthesis of the MOF.
  • the MOFs can be prepared by some well-known methods, such as hydrothermal, solvothermal, and microwave assisted techniques.
  • MOFs are also commercially available.
  • suitable commercially available metal-organic frameworks include: Basolite A100 (MIL-53 (Al) ) and Basolite F-300 (Fe-BTC) etc. produced by BASF.
  • the metal of elemental metal or metal compound is selected from the group consisting of Ru, Pd, Pt, Ag, Au, Cu and combinations thereof.
  • the metal is Ru.
  • Metal compound is preferably chosen in the group consisting of: metal oxides, salts of metal and any combination thereof.
  • Said salts can be selected from the group consisting of halide, nitrate, nitrite, carbonate, bicarbonate, sulphate, sulphite, thiosulfate, phosphate, phosphite, hypophosphite, formate, acetate and propionate.
  • the MOF catalyst according to the present invention comprises one elemental metal and its corresponding metal compound.
  • the weight ratio of metal compound is less than 0.5 wt%based on total weight of elemental metal and metal compound in this embodiment and preferably less than 0.2 wt%and more preferably less than 0.1 wt%.
  • Said metal compound in this embodiment is notably metal oxide.
  • the MOF catalyst according to the present invention comprises solely elemental metal (s) .
  • the weight ratio of elemental metal and/or metal compound nanoparticles based on total weight of MOF catalyst may be from 1%to 20%and preferably from 5%to 15%.
  • the method to embed the elemental metal and/or metal compound nanoparticles in the MOF can be a wet impregnation method.
  • a double solvent wet impregnation method as described in J. Am. Chem. Soc., 2012, 134, 13926–13929 is used in the preparation of present catalysts to achieve even distribution of catalytic metal nanoparticles in the MOF particles.
  • the method for preparing the MOF catalyst according to the present invention comprises the following steps:
  • the solution in step (i) is preferably an aqueous solution.
  • a mixture of water and organic solvent can also be used as solvent for metal salt in step (i) , with the proviso that such organic solvent can be miscible with water and the solvent introduced in step (iii) .
  • the solvents are ethanol, 1-propanol, 2-propanol, acetone, tetrahydrofuran, dioxane etc.
  • the volume ratio of water to organic solvent in this embodiment is from 1: 5-1: 20 andpreferably 1: 8-1: 12.
  • the solvent in step (iii) has polarity index ⁇ 3.0.
  • the skilled person knows the polarity index by referring to solvent properties (http: //www. finarchemicals. com/pdf/hplc_solvent_properties_solvent_miscibilit y_table. pdf) .
  • Such low polarity solvent is preferably selected from the group consisting of pentane, hexane, petroleum ether, benzene and cyclohexane.
  • the drying temperature in step (v) is preferably from 25 to 200°C.
  • the reduction reaction in step (vi) is preferably performed by using hydrogen atmosphere (H 2 ) under proper temperature, such as 150 to 200°C.
  • Alcohol I may be a compound represented by the general formula (I) as follow:
  • R 1 and R 2 independently from each other, represent hydrogen, or a straight, branched, cyclic hydrocarbon group, which is optionally interrupted by one or several heteroatoms and/or which is optionally substituted by one or several functional group.
  • n is an integer, ranging from 1-20. Preferably, m is an integer, ranging from 1-5.
  • the functional groups are selected from the group consisting of alkyl, alkenyl, alkynyl, alkoxy, alkylated amino, carboxyl, formyl, ester, cyano, nitro and halogen.
  • Said heteroatoms can be O, S, F, or N.
  • R 1 or R 2 is not interrupted by any heteroatom.
  • R 1 or R 2 is preferably selected from a group consisting of hydrogen, straight or branched alkyl, alkenyl and alkynyl.
  • Alcohol I can be a monoalcohol, such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1- undecanol and 1-dodecanol.
  • Preferred monoalcohol can be methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol and 1-heptanol.
  • Alcohol I can also be a diol, such as ethylene glycol, 1, 3-propanediol, 1, 4-butanediol and 1, 5-pentanediol.
  • Alcohol I can even be a triol, such as glycerol.
  • Alcohol I is a diol.
  • R 1 or R 2 may also be aryl, cycloalkyl or heterocyclic group, which is optionally substituted by one or several functional groups.
  • aryl refers to a monovalent aromatic hydrocarbon group, including bridged ring and/or fused ring systems, containing at least one aromatic ring. Examples of aryl groups include phenyl, naphthyl and the like.
  • cycloalkyl as used herein means cycloalkyl groups containing from 3 to 8 carbon atoms, such as cyclohexyl.
  • heterocyclic as used herein means heterocyclic groups containing up to 6 carbon atoms together with 1 or 2 heteroatoms which are usually selected from O, N and S, such as furyl.
  • Alcohol I can be 2, 5-dihydroxymethylfuran or hydroxymethylfurfural.
  • Alcohol I can be isosorbide.
  • Alcohol II may be a compound represented by the general formula (II) as follow:
  • R 3 and R 4 have the same meaning of R 1 and R 2 .
  • R 3 or R 4 is hydrogen.
  • n is an integer, ranging from 2-8. Preferably, n ranges from 2-5.
  • Alcohol II can be diol, such as ethylene glycol, 1, 3-propanediol, 1, 4-butanediol and 1, 5-pentanediol.
  • Alcohol II can be isosorbide.
  • Alcohol I and Alcohol II are same alcohols comprising two and only two primary or secondary hydroxyl groups, which are compounds represented by the general formula (III) :
  • p is an integer, ranging from 0-20. Preferably, p ranges from 0-5.
  • R 5 , R 6 , R 7 and R 8 have the same meaning as R 1 and R 2 .
  • R 5 , R 6 , R 7 or R 8 is hydrogen.
  • the compound represented by the general formula (III) in Scheme 2 is selected from a group consisting of ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 2, 5-dihydroxymethylfuran and more preferably ethylene glycol, 1, 3-propanediol and 1, 4-butanediol.
  • the weight ratio of alcohol to MOF catalyst is preferably from 20: 1 to 40: 1.
  • Alcohol I and Alcohol II are different alcohols comprising two and only two primary or secondary hydroxyl groups.
  • Alcohol I is the compound represented by the general formula (III) .
  • Alcohol II is a compound represented by the general formula (IV) as follow:
  • q is an integer, ranging from 0-20. Preferably, q ranges from 0-5.
  • R 9 , R 10 , R 11 and R 12 have the same meaning of R 5 , R 6 , R 7 and R 8 above mentioned.
  • Alcohol I and Alcohol II are different compounds in this embodiment.
  • the compound represented by the general formula (III) in Scheme 3 is selected from a group consisting of ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 2, 5-dihydroxymethylfuran and more preferably ethylene glycol, 1, 3-propanediol and 1, 4-butanediol.
  • the compound represented by the general formula (IV) in Scheme 3 is ethylene glycol or 1, 3-propanediol.
  • the molar ratio of the compound represented by the general formula (IV) to the compound represented by the general formula (III) is preferably from 1: 1 to 5: 1 and more preferably from 2: 1 to 3: 1.
  • the weight ratio of alcohol (s) to MOF catalyst is preferably from 20: 1 to 40: 1.
  • the reaction according to the present invention can be carried out in the absence of a solvent.
  • the reaction according to the present invention can also be carried out in the presence of a solvent.
  • the solvent may be toluene, cyclohexane or THF.
  • reaction in the process according to the present invention can be conducted under usual process parameters well known to a person skilled in the art.
  • the reaction temperature depends on the reactants.
  • the reaction temperature is advantageously in a range of 90 to100°Cwhen 1-butanol is the reactant.
  • the reaction time can be 15-20 hours and preferably 15-17 hours.
  • the oxygen can be introduced into the reaction vessel in the form of suitable oxygen containing gases, such as air, oxygen gas, and mixtures of oxygen gas with other gases such as nitrogen or argon.
  • suitable oxygen containing gases such as air, oxygen gas, and mixtures of oxygen gas with other gases such as nitrogen or argon.
  • the oxygen containing gas is a flowing oxygen containing gas.
  • the reaction vessel is charged with the oxygen containing gas. Pure oxygen gas is preferable.
  • the total gas pressure of during the reaction is not particularly limited and can be selected according to the requirements.
  • pure oxygen gas is used at a pressure in the range of 1 bar to 20 bar, preferably in the range of 5 bar to 20 bar, such as 10 bar to 20 bar.
  • chromium precursor chromium (II) nitrate nonahydrate (Cr (NO 3 ) 3 ⁇ 9H 2 O)
  • dicarboxylic acid ligand (1, 4-dicarboxybenzene (BDC)
  • BDC 4-dicarboxybenzene
  • MOF powder prepared by Example 1 200 mg was placed into a 250 ml round bottom flask. Then 49.5 mg Ruthenium (III) chloride hydrate (RuCl 3 ⁇ xH 2 O) was added and dissolved in distilled water/ethanol (200 ⁇ L: 2 mL) . 10 mL dichloromethane (DCM) was added to the mixture and sonicated for 5 min more to achieve clear solution. After adding 20 mL petroleum ether into the solution, the brown powder was collected through centrifugation. After brief drying in a 70°C oven, the samples were reduced into a U-type glass tube under 1 bar hydrogen atmosphere (H 2 ) , 200°Covernight.
  • H 2 1 bar hydrogen atmosphere
  • the metal content in the MOF was quantified through thermogravimetric analysis (TGA) . Specifically, a known amount of MOF sample (5-10mg) was gradually heated up to 800°Cunder O 2 atmosphere in a TGA furnace. The exact weight of the dry MOF was determined by the first plateau after solvent weight loss peak ( ⁇ at 200°C) . The exact metal content can be calculated based on the remaining metal oxide weight at 800°C (Cr 2 O 3 ) .
  • Ru nanoparticles are embedded in the pores of MOF.
  • TEM-EDX images show Cr and Ru elements are both uniformly distributed through MOF crystal which confirms that Ru nanoparticles are inside of MOF crystal.

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Abstract

Provided herein is a process for preparing acetals or ketals by reacting Alcohol I, Alcohol II and oxygen in the presence of a metal-organic framework (MOF) catalyst.

Description

A process for preparing acetals or ketals TECHNICAL FIELD
The present invention relates to a process for the preparation of acetals or ketals.
BACKGROUND
Acetal/ketal, the pivotal compounds in the manufacture of pharmaceutical products and detergent products and fuel additives etc., are commonly prepared through the acetalization reaction of aldehyde/ketone and alcohol.
J. AM. CHEM. SOC. 2009, 131, 3146–3147 reports direct dehydrogenation of alcohols to acetals and H 2 in neutral media by an acridine-based ruthenium pincer complex. Disadvantageously, this reaction needs high reaction temperature and long reaction time, which is more than 26 hours.
It is well-known to those skilled in the art to functionalize the MOFs by post-synthesis addition of different compounds, which can be used as active catalysts.
For example, Chinese Patent Publication No. 103113347A discloses a method for preparing acetals or ketals under catalytic action of metal-organic frameworks (hereinafter MOFs) . The metal-organic framework compound has a structure as follow:
Figure PCTCN2018122078-appb-000001
Yields and selectivities towards acetals and ketals are high by using such MOF catalyst. However, expensive aldehylde/acetone is inevitably used as starting material.
ACS Catalysis (2014) , 4 (10) , 3490-3497 suggests oxidation of benzyl alcohol and the subsequent acetalization with ethylene in the presence of a MOF catalyst, in which palladium nanoclusters are encapsulated. Disadvantageously, it is necessary to prepare the target product by two-step reaction.
There is still a need to provide a process to prepare acetals or ketals directly from monoalcohols with desired characteristics such as simplicity, inexpensiveness, energy saving and ease of handling which can overcome the drawbacks in prior arts.
SUMMARY OF THE INVENTION
The present invention therefore pertains to a process for preparing an acetal or ketal by reacting Alcohol I, Alcohol II and oxygen in the presence of a metal-organic framework (MOF) catalyst, wherein:
- Alcohol I is an alcohol comprising one or more primary hydroxyl group (s) and/or one or more secondary hydroxyl group (s) ;
- Alcohol II is an alcohol comprising two and only two hydroxyl groups;
- the metal-organic framework catalyst is a metal-organic framework, in which elemental metal and/or metal compound nanoparticles are embedded;
- the metal of elemental metal or metal compound is selected from the group consisting of Ru, Pd, Pt, Ag, Au and Cu.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a TEM image of Ru@MIL 101 (Cr) of Example 2.
Fig. 2 is an image of enlargement view of Fig. 1. The nanoparticle is highlighted by a circle.
Fig. 3A-3D are TEM-EDX images of Ru@MIL 101 (Cr) of Example 2.
Fig. 4 is an image of N 2 adsorption-desorption isotherm curves of MIL 101 (Cr) and Ru@MIL 101 (Cr) of Example 2.
DEFINITIONS
Throughout the description, including the claims, the term "comprising one" should be understood as being synonymous with the term "comprising at least one" , unless otherwise specified, and "between" should be understood as being inclusive of the limits.
As used herein, the terminology " (C n-C m) " in reference to an organic group, wherein n and m are each integers, indicates that the group may contain from n carbon atoms to m carbon atoms per group.
The articles “a” , “an” and “the” are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.
The term “and/or” includes the meanings “and” , “or” and also all the other possible combinations of the elements connected to this term.
It is specified that, in the continuation of the description, unless otherwise indicated, the values at the limits are included in the ranges of values which are given.
Ratios, concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
DETAILS OF THE INVENTION
Metal-organic frameworks (MOFs) are compounds consisting of metal ions or clusters coordinated to organic ligands to form one-, two-, or three-dimensional structures.
These MOFs are crystalline structures comprising repeating metal building units connected by linking ligands via metal-ligands bonds. The MOF materials exhibit analogous properties to that of conventional microporous and mesoporous materials such as large and accessible surface areas with interconnected intrinsic micropores or mesopores. As such, the MOFs of the invention have very high surface area per unit volume and very high porosities. The pore size may be controlled with the choice of linking ligand. With a given topology, progressively increasing the length of the linking ligand usually results in larger pore size.
In order to allow the reagents to freely diffuse in the MOF particles, the aperture size and pore size of the MOF should be larger than the kinetic diameter of the reagents.
The pore size of the MOF used in the process according to the present invention is from 0.4 to 5 nm and preferably from 0.5 to 2 nm. The method for analyzing the pore size can be gas adsorption analysis which uses N 2 as the adsorbate and 77.3K as sorption temperature. Specifically, Belsorb MAX II was used for the gas adsorption analysis. Sorption was measured down to 10 -8 bar. BelMASTER software was used for data processing. Grand Canonical Monte Carlo (GCMC) with no fitting assumption was used for pore size distribution analysis based on the experimental data. Cylindrical pore model should be used. 
The average particle size of elemental metal and/or metal compound nanoparticles embedded in MOF is from 0.5 to 20 nm and preferably from 0.5 to 2 nm, which is measured using transmission electron microscopy (TEM) .
For TEM analysis, a JEOL 2100 with Filament LaB6 having an acceleration voltage of 200 kV equipped with a camera Gatan 832 CCD was used. As support, square 230 mesh TEM support grids (copper) were used. The magnification factor had a range of '10,000～'600,000. For 50 nm: magnification factor was 40,000～50,000; for 20 nm: 60,000～120,000; for 10 nm: 250,000; for 5 nm: 400,000; for 2 nm: 500,000～600,000. Samples of 0.1 wt. %nanoparticles in methanol suspension were measured. The obtained results were analyzed using the DigitalMicrograph software. For each sample, two pictures were taken and a total of 100 nanoparticles were analyzed for obtaining the described size distribution. From this size distribution, the average particle size of the nanoparticles was obtained. The software used to measure the size of the nanoparticles was ImageJ thereby approximating the particles to be spherical. After setting the scale, the maximum diameter of the particles was manually measured one by one to a total number of particles measured of 100. Every particle has been measured 3 times to obtain an average size.
The average particle size of the MOF catalyst is from 10 nm to 100μm and preferably from 100 nm to 1μm, which is measured using transmission electron microscopy (TEM) . The methods for analyzing the MOF particle size is TEM.
The materials of use for the present invention include MOFs with metal building units which may be metal ions or metal cluster building units where the metal of the metal building units is selected from the transition metals or IIIA group metals. Preferably, the metal of the metal building units is selected from the group consisting of Al, Cr, Zr, Sc, Hf, Ti, Cu, Co, In, Fe, Ni, Zn and V, more preferably selected from the group consisting of Al, Cr, Zr, Sc, Hf, Ti and Fe, and most preferably Al or Cr.
As used herein, metals of group IB, IIB, IIIB, IVB, VB, VIB, VIIB and VIIIB are often referred to as transition metals. This group comprises the elements with atomic number 21 to 30 (Sc to Zn) , 39 to 48 (Y to Cd) , 72 to 80 (Hf to Hg) and 104 to 112 (Rf to Cn) .
The metal building units are connected by organic compounds known as linking ligands to form a porous crystalline structure. A skilled person will recognize the compounds available for use as linking ligands are numerable, such as those described in Nature volume 423, pages 705–714 (12 June 2003) .
The linking ligand is not particularly limited. Preferred linking ligands for linking the adjacent metal building units is carboxylate-based ligands, which include 1, 3, 5-benzenetribenzoate (BTB) : 1, 4-benzenedicarboxylate (BDC) ; cyclobutyl 1, 4-benzenedicarboxylate (CB BDC) : 2-amino 1, 4 benzenedicarboxylate (H 2N-BDC) ; 4, 5, 9, 10-tetrahydropyrene-2, 7-dicarboxylate (HPDC) ; terphenyl dicarboxylate (TPDC) ; 2, 6-naphthalene dicarboxylate (NDC) ; pyrene 2, 7-dicarboxylate (PDC) ; biphenyl dicarboxylate (BDC) ; or any di-, tri-, or tetracarboxylate containing phenyl rings.
Preferably, the MOFs according to the present invention are MIL MOF, UiO-type MOF, MOF-808 etc.
Examples of MIL MOF include: MIL100, MIL101. Preferred examples of MIL MOF are as follows:
- MIL100 (Al) , which has the formula unit as follow:
Al 3O (OH) (H 2O)  2 [C 6H 3 (CO 2)  3]  2. nH 2O (wherein n is～24, Chem. Mater. 2009, 21, 5695-5697)
- MIL101 (Cr) , which has the formula unit as follow:
Cr 3F (H 2O)  2O [ (O 2C) C 6H 4 (CO 2) ]  3. nH 2O (wherein n is～25, Science 2005, 309, 2040)
Preferred example of UiO-type MOF is as follow:
- UiO-66 (Zr) , which has the formula unit as follow:
Zr 6[ (O 2C) C 6H 4 (CO 2) ]  6O 4 (OH)  4 (J. Am. Chem. Soc. 2008, 130, 13850-13851)
Preferred example of MOF-808 is as follow:
- MOF-808 (Zr) , which has the formula unit as follow:
Zr 6O 4 (OH)  4 [C 6H 3 (CO 2)  3]  2 (HCOO)  6 (J. Am. Chem. Soc. 2014, 136, 4369-4381)
Functionalization of the MOF to embed elemental metal and/or metal compound nanoparticles is performed after synthesis of the MOF. The MOFs can be prepared by some well-known methods, such as hydrothermal, solvothermal, and microwave assisted techniques.
- MIL101 (Cr) hydrothermal and microwave method (Chem. Mater. 2012, 24, 1664-1675)
- MIL100 (Al) hydrothermal (Chem. Mater. 2009, 21, 5695–5697) and microwave method (Eur. J. Inorg. Chem. 2012, 5165–5174)
- MOF-808 (Zr) hydrothermal (J. Am. Chem. Soc. 2014, 136, 4369-4381) and microwave method (Materials Letters 160 (2015) 412–414)
- UiO-66 (Zr) hydrothermal (Chem. Asian J. 2013, 8, 69–72) and microwave method (Dalton Trans., 2015, 44, 14019-14026)
The MOFs are also commercially available. Examples of suitable commercially available metal-organic frameworks include: Basolite A100 (MIL-53 (Al) ) and Basolite F-300 (Fe-BTC) etc. produced by BASF.
The metal of elemental metal or metal compound is selected from the group consisting of Ru, Pd, Pt, Ag, Au, Cu and combinations thereof. Preferably, the metal is Ru.
Metal compound is preferably chosen in the group consisting of: metal oxides, salts of metal and any combination thereof. Said salts can be selected from the group consisting of halide, nitrate, nitrite, carbonate, bicarbonate, sulphate, sulphite, thiosulfate, phosphate, phosphite, hypophosphite, formate, acetate and propionate.
In a particular embodiment, the MOF catalyst according to the present invention comprises one elemental metal and its corresponding metal compound. The weight ratio of metal compound is less than 0.5 wt%based on total weight of elemental metal and metal compound in this embodiment and preferably less than 0.2 wt%and more preferably less than 0.1 wt%. Said metal compound in this embodiment is notably metal oxide.
Advantageously, the MOF catalyst according to the present invention comprises solely elemental metal (s) .
The weight ratio of elemental metal and/or metal compound nanoparticles based on total weight of MOF catalyst may be from 1%to 20%and preferably from 5%to 15%.
The method to embed the elemental metal and/or metal compound nanoparticles in the MOF can be a wet impregnation method. For example, a double solvent wet impregnation method as described in J. Am. Chem. Soc., 2012, 134, 13926–13929 is used in the preparation of present catalysts to achieve even distribution of catalytic metal nanoparticles in the MOF particles.
In one embodiment, the method for preparing the MOF catalyst according to the present invention comprises the following steps:
(i) Preparing a solution, in which a metal salt is dissolved;
(ii) Mixing the solution obtained at step (i) with MOF powder;
(iii) Adding a solvent having polarity index<3.0 to the mixture obtained at step (ii) to obtain MOF powder with the metal salt embedded in the pores;
(iv) Centrifugating MOF powder from the mixture obtained by step (iii) ;
(v) Optionally drying MOF powder obtained by step (iv) ;
(vi) Deducing MOF powder obtained by step (v) .
The solution in step (i) is preferably an aqueous solution.
In some embodiments, a mixture of water and organic solvent can also be used as solvent for metal salt in step (i) , with the proviso that such organic solvent can be miscible with water and the solvent introduced in step (iii) . Examples of the solvents are ethanol, 1-propanol, 2-propanol, acetone, tetrahydrofuran, dioxane etc. The volume ratio of water to organic solvent in this embodiment is from 1: 5-1: 20 andpreferably 1: 8-1: 12.
As expressed previously, the solvent in step (iii) has polarity index<3.0. The skilled person knows the polarity index by referring to solvent properties (http: //www. finarchemicals. com/pdf/hplc_solvent_properties_solvent_miscibilit y_table. pdf) . Such low polarity solvent is preferably selected from the group consisting of pentane, hexane, petroleum ether, benzene and cyclohexane.
The drying temperature in step (v) is preferably from 25 to 200℃.
The reduction reaction in step (vi) is preferably performed by using hydrogen atmosphere (H 2) under proper temperature, such as 150 to 200℃.
Alcohol I may be a compound represented by the general formula (I) as follow:
R 1 (CHR 2OH)  m (I)
R 1 and R 2, independently from each other, represent hydrogen, or a straight, branched, cyclic hydrocarbon group, which is optionally interrupted by one or several heteroatoms and/or which is optionally substituted by one or several functional group.
m is an integer, ranging from 1-20. Preferably, m is an integer, ranging from 1-5.
The functional groups are selected from the group consisting of alkyl, alkenyl, alkynyl, alkoxy, alkylated amino, carboxyl, formyl, ester, cyano, nitro and halogen.
Said heteroatoms can be O, S, F, or N.
Preferably, R 1 or R 2 is not interrupted by any heteroatom.
R 1 or R 2 is preferably selected from a group consisting of hydrogen, straight or branched alkyl, alkenyl and alkynyl.
Alcohol I can be a monoalcohol, such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1- undecanol and 1-dodecanol. Preferred monoalcohol can be methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol and 1-heptanol.
Alcohol I can also be a diol, such as ethylene glycol, 1, 3-propanediol, 1, 4-butanediol and 1, 5-pentanediol.
Alcohol I can even be a triol, such as glycerol.
Preferably, Alcohol I is a diol.
R 1 or R 2 may also be aryl, cycloalkyl or heterocyclic group, which is optionally substituted by one or several functional groups.
As used herein, the term "aryl" refers to a monovalent aromatic hydrocarbon group, including bridged ring and/or fused ring systems, containing at least one aromatic ring. Examples of aryl groups include phenyl, naphthyl and the like.
As used herein, the term "cycloalkyl" as used herein means cycloalkyl groups containing from 3 to 8 carbon atoms, such as cyclohexyl.
As used herein, the term “heterocyclic" as used herein means heterocyclic groups containing up to 6 carbon atoms together with 1 or 2 heteroatoms which are usually selected from O, N and S, such as furyl.
For example, Alcohol I can be 2, 5-dihydroxymethylfuran or hydroxymethylfurfural.
In some embodiments, Alcohol I can be isosorbide.
Alcohol II may be a compound represented by the general formula (II) as follow:
OH (CR 3R 4)  nOH (II)
R 3and R 4 have the same meaning of R 1 and R 2.
Preferably, R 3or R 4is hydrogen.
n is an integer, ranging from 2-8. Preferably, n ranges from 2-5.
For example, Alcohol II can be diol, such as ethylene glycol, 1, 3-propanediol, 1, 4-butanediol and 1, 5-pentanediol.
In some embodiments, Alcohol II can be isosorbide.
The reaction of Alcohol I, Alcohol II and oxygen in the presence of a MOF catalyst is exemplified by the following general reaction Scheme 1:
Figure PCTCN2018122078-appb-000002
Scheme 1
In one preferred embodiment, Alcohol I and Alcohol II are same alcohols comprising two and only two primary or secondary hydroxyl groups, which are compounds represented by the general formula (III) :
OHCHR 5 (CR 6R 7)  pCHR 8OH (III)
p is an integer, ranging from 0-20. Preferably, p ranges from 0-5.
R 5, R 6, R 7and R 8 have the same meaning as R 1 and R 2. Preferably, R 5, R 6, R 7or R 8 is hydrogen.
The reaction in this embodiment is exemplified by the following general reaction Scheme 2:
Figure PCTCN2018122078-appb-000003
Scheme 2
Preferably, the compound represented by the general formula (III) in Scheme 2 is selected from a group consisting of ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 2, 5-dihydroxymethylfuran and more preferably ethylene glycol, 1, 3-propanediol and 1, 4-butanediol.
In this embodiment, the weight ratio of alcohol to MOF catalyst is preferably from 20: 1 to 40: 1.
In another preferred embodiment, Alcohol I and Alcohol II are different alcohols comprising two and only two primary or secondary hydroxyl groups. Alcohol I is the compound represented by the general formula (III) . Alcohol II is a compound represented by the general formula (IV) as follow:
OHCHR 9 (CR 10R 11)  qCHR 12OH (IV)
q is an integer, ranging from 0-20. Preferably, q ranges from 0-5.
R 9, R 10, R 11 and R 12 have the same meaning of R 5, R 6, R 7 and R 8 above mentioned. However, Alcohol I and Alcohol II are different compounds in this embodiment.
The reaction in this embodiment is exemplified by the following general reaction Scheme 3:
Figure PCTCN2018122078-appb-000004
Scheme 3
Preferably, the compound represented by the general formula (III) in Scheme 3 is selected from a group consisting of ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 2, 5-dihydroxymethylfuran and more preferably ethylene glycol, 1, 3-propanediol and 1, 4-butanediol.
Preferably, the compound represented by the general formula (IV) in Scheme 3 is ethylene glycol or 1, 3-propanediol.
In this embodiment, the molar ratio of the compound represented by the general formula (IV) to the compound represented by the general formula (III) is preferably from 1: 1 to 5: 1 and more preferably from 2: 1 to 3: 1.
In this embodiment, the weight ratio of alcohol (s) to MOF catalyst is preferably from 20: 1 to 40: 1.
The reaction according to the present invention can be carried out in the absence of a solvent.
The reaction according to the present invention can also be carried out in the presence of a solvent. The solvent may be toluene, cyclohexane or THF.
The reaction in the process according to the present invention can be conducted under usual process parameters well known to a person skilled in the art. In view of yield and selectivity of the process it is, the reaction temperature depends on the reactants. For example, the reaction temperature is advantageously in a range of 90 to100℃when 1-butanol is the reactant.
The reaction time can be 15-20 hours and preferably 15-17 hours.
The oxygen can be introduced into the reaction vessel in the form of suitable oxygen containing gases, such as air, oxygen gas, and mixtures of oxygen gas with other gases such as nitrogen or argon. In some embodiments, the oxygen containing gas is a flowing oxygen containing gas. Alternatively, the reaction vessel is charged with the oxygen containing gas. Pure oxygen gas is preferable.
The total gas pressure of during the reaction is not particularly limited and can be selected according to the requirements. For example, pure oxygen gas is used at a pressure in the range of 1 bar to 20 bar, preferably in the range of 5 bar to 20 bar, such as 10 bar to 20 bar.
The following examples are included to illustrate embodiments of the invention. Needless to say, the invention is not limited to described examples.
EXPERIMENTAL PART
Materials
- Chromium (III) nitrate nonahydrate, CAS No. 7789-02-8 purity: AR, 99.0%from aladdin.
- Dicarboxybenzene, CAS No. 100-21-0 purity: 99%from aladdin
- N, N-Dimethylformamide (DMF) , CAS No. 68-12-2 purity: ≧99.8%from Greagent
- Aluminum nitrate nonahydrate, CAS No. 7784-27-2 purity: AR, 99.0%from aladdin
- Trimesic Acid, CAS No. 554-95-0 purity: 98%from Accela ChemBio
- Ruthenium (III) chloride hydrate, CAS No. 14898-67-0 purity: 99.9%from Accela ChemBio
- Deionized water
- Dichloromethane, CAS No. 75-09-2 purity: ≧99.5%, AR from Greagent
Example 1
Catalyst preparation MIL101 (Cr)
Generally, chromium precursor (chromium (II) nitrate nonahydrate (Cr (NO 3)  3·9H 2O) ) (1 g, 2.5 mmol) , dicarboxylic acid ligand (1, 4-dicarboxybenzene (BDC) ) (415 mg, 2.5 mmol) were dispersed in 10 mL distilled water at room temperature. The mixture was then transferred to a 25 mL Teflon-lined cap and heated in a 200℃oven for 7h. After cooling down to room temperature, the product was collected by centrifugation, washed with DMF and methanol multiple times and dried at room temperature by exposing to air.
Example 2
Catalyst preparation Ru@MIL 101 (Cr)
200 mg of MOF powder prepared by Example 1 was placed into a 250 ml round bottom flask. Then 49.5 mg Ruthenium (III) chloride hydrate (RuCl 3·xH 2O) was added and dissolved in distilled water/ethanol (200μL: 2 mL) . 10 mL dichloromethane (DCM) was added to the mixture and sonicated for 5 min more to achieve clear solution. After adding 20 mL petroleum ether into the solution,  the brown powder was collected through centrifugation. After brief drying in a 70℃ oven, the samples were reduced into a U-type glass tube under 1 bar hydrogen atmosphere (H 2) , 200℃overnight.
Quantification of the metal content in the MOF:
The metal content in the MOF was quantified through thermogravimetric analysis (TGA) . Specifically, a known amount of MOF sample (5-10mg) was gradually heated up to 800℃under O 2 atmosphere in a TGA furnace. The exact weight of the dry MOF was determined by the first plateau after solvent weight loss peak (～at 200℃) . The exact metal content can be calculated based on the remaining metal oxide weight at 800℃ (Cr 2O 3) .
Quantification of Ru
Ru@MIL 101 (Cr) samples were digested in concentrated nitric acid and then diluted to an exact volume in a volumetric flask. ICP-OES was used to determine the concentration of Ru and framework metal Cr. Ru loading was calculated by multiplying Ru/M weight ratio with the metal content in the MOF. In this example, the Cr content in MIL 101 (Cr) is 22%according to TGA. Ru/Cr weight ratio was identified as 0.245. Therefore, the Ru loading in MIL 101 (Cr) is 0.245x0.22=5.4wt%.
As shown by Fig. 1 and Fig. 2, Ru nanoparticles are embedded in the pores of MOF.
TEM-EDX images (Fig. 3A-3D) show Cr and Ru elements are both uniformly distributed through MOF crystal which confirms that Ru nanoparticles are inside of MOF crystal.
The internal volume of MOF then becomes small after it is embedded by nanoparticles in the pores as shown by Figure 4.
Example 3
1, 3-Propanediol oxidation over Ru@MIL 101 (Cr)
Put in 50 ml stainless steel reactor 3 g of 1, 3-propanediol and 100 mg of Ru@MIL 101 (Cr) catalyst. The reactor was sealed and pressurized with 10 bar of O 2. The reaction was heated to 130℃for 16 h under continuous stirring. After reaction the products were analyzed by GC and GC-MS. The conversion of 1, 3-propanediol is 65%and the selectivity to acetal is 88%. Traces of other compounds like hemiacetal and aldehyde were also observed.
Figure PCTCN2018122078-appb-000005
Ethylene glycol oxidation over Ru@MIL 101 (Cr)
Put in 50 ml stainless steel reactor 3 g of ethylene glycol and 100 mg of Ru@MIL 101 (Cr) catalyst. The reactor was sealed and pressurized with 10 bar of O 2. The reaction was heated to 130℃for 16 h under continuous stirring. After reaction the products were analyzed by GC and GC-MS. The conversion of ethylene glycol is 11%and the selectivity to acetal is 93%. Traces of other compounds like hemiacetal and aldehyde were also observed.
Increase of the reaction time to 24 h leads to increase of conversion to 29%at the selectivity to acetal 90%.
Figure PCTCN2018122078-appb-000006
Example 5
2, 5-hydroxymethylfurfural oxidation over Ru@MIL 101 (Cr) in the presence of ethyleneglycol
Put in 50 ml stainless steel reactor 1 g of HMF and 1.2 g of ethylene glycol with the molar ratio of HMF: glycol=1: 2.5 and 100 mg of Ru@MIL 101 (Cr) catalyst. The reactor was sealed and pressurized with 10 bar of O 2. The reaction was heated to 130℃for 5 h under continuous stirring. After reaction the products were analyzed by GC and GC-MS. The conversion of HMF is full and the selectivity to full acetal (3) is 22%, to hemiacetals (1 and 2) 78%. Traces of other compounds like hemiacetal and aldehyde were also observed.
Increase of the reaction time to 10 h leads to increase of the selectivity to full acetal (3) to 85%, to hemiacetals (1 and 2) 15%.
Figure PCTCN2018122078-appb-000007

Claims (13)

  1. A process for preparing an acetal or ketal by reacting Alcohol I, Alcohol II and oxygen in the presence of a metal-organic framework (MOF) catalyst, wherein:
    - Alcohol I is an alcohol comprising one or more primary hydroxyl group (s) and/or one or more secondary hydroxyl group (s) ;
    - Alcohol II is an alcohol comprising two and only two hydroxyl groups;
    - the metal-organic framework catalyst is a metal-organic framework, in which elemental metal and/or metal compound nanoparticles are embedded;
    - the metal of elemental metal or metal compound is selected from the group consisting of Ru, Pd, Pt, Ag, Au and Cu.
  2. The process according to claim 1, wherein Alcohol I is a compound represented by the general formula (I) as follow:
    R 1 (CHR 2OH)  m (I)
    wherein:
    - R 1 and R 2, independently from each other, represent hydrogen, or a straight, branched, cyclic hydrocarbon group,
    which is optionally interrupted by one or several heteroatoms and/or
    which is optionally substituted by one or several functional group.
    - m is an integer, ranging from 1-20.
  3. The process according to claim 1, wherein Alcohol II is a compound represented by the general formula (II) as follow:
    OH (CR 3R 4)  nOH (II)
    wherein:
    - R 3 and R 4, independently from each other, represent hydrogen, or a straight, branched, cyclic hydrocarbon group,
    which is optionally interrupted by one or several heteroatoms and/or
    which is optionally substituted by one or several functional group.
    - n is an integer, ranging from 2-8.
  4. The process according to claim 1, wherein Alcohol I and Alcohol II are same alcohols comprising two and only two primary or secondary hydroxyl groups, which are compounds represented by the general formula (III) and the reaction of Alcohol I and Alcohol II with oxygen in the presence of a metal-organic framework catalyst and the reaction proceeds in accordance with Scheme 2:
    Figure PCTCN2018122078-appb-100001
    wherein:
    - R 5, R 6, R 7 and R 8, independently from each other, represent hydrogen, or a straight, branched, cyclic hydrocarbon group,
    which is optionally interrupted by one or several heteroatoms and/or
    which is optionally substituted by one or several functional group.
    - p is an integer, ranging from 0-20.
  5. The process according to claim 1, wherein Alcohol I and Alcohol II are different alcohols comprising two and only two primary or secondary hydroxyl groups, which are compounds represented by the general formula (III) and (III) , and the reaction of Alcohol I and Alcohol II with oxygen in the presence of a metal-organic framework catalyst and the reaction proceeds in accordance with Scheme 3:
    Figure PCTCN2018122078-appb-100002
    wherein:
    - R 5, R 6, R 7, R 8, R 9, R 10, R 11 and R 12 independently from each other, represent hydrogen, or a straight, branched, cyclic hydrocarbon group,
    which is optionally interrupted by one or several heteroatoms and/or
    which is optionally substituted by one or several functional group.
    - p or q is an integer, ranging from 0-20.
  6. The process according to any one of claims 1 to 5, the pore size of the metal-organic framework is from 0.4 to 5 nm.
  7. The process according to any one of claims 1 to 6, wherein the average particle size of elemental metal or metal compound nanoparticles embedded in the metal-organic framework is from 0.5 to 20 nm.
  8. The process according to any one of claims 1 to 7, wherein the average particle size of the metal-organic framework catalyst is from 10 nm to 100μm and preferably from 100 nm to 1μm.
  9. The process according to any one of claims 1 to 8, wherein the metal-organic framework is selected from the group consisting of MIL MOF, UiO-type MOF and MOF-808.
  10. The process according to any one of claims 1 to 9, wherein the metal of the metal building units of metal-organic framework is selected from Al, Cr, Zr, Sc, Hf, Ti, Cu, Co, In, Fe, Ni, Zn and V.
  11. The process according to claim 10, whereinthe metal of the metal building units of metal-organic framework is Al or Cr.
  12. The process according to any one of claims 1 to 11, wherein the metal of elemental metal or metal compound is Ru.
  13. The process according to any one of claims 1 to 12, wherein the reaction is carried out in the absence of a solvent.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001081276A2 (en) * 2000-04-26 2001-11-01 Mitsubishi Chemical Corporation Method for producing ketal and/or acetal
WO2015051525A1 (en) * 2013-10-11 2015-04-16 Rhodia Operations Synthesis of acetal/ketal
CN106669842A (en) * 2016-12-06 2017-05-17 北京林业大学 Preparation method and application of HPA@MIL-100 (Cr) catalyst

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001081276A2 (en) * 2000-04-26 2001-11-01 Mitsubishi Chemical Corporation Method for producing ketal and/or acetal
WO2015051525A1 (en) * 2013-10-11 2015-04-16 Rhodia Operations Synthesis of acetal/ketal
CN106669842A (en) * 2016-12-06 2017-05-17 北京林业大学 Preparation method and application of HPA@MIL-100 (Cr) catalyst

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BUENO, ALINE C. ET AL.: "Palladium-catalyzed oxidation of primary alcohols:Highly selective direct synthesis of acetals", APPLIED CATALYSIS A: GENERAL, vol. 329, 15 June 2007 (2007-06-15), XP022200004 *
KETLEY， A. D. ET AL.: "THE REACTIONS OF ALKENEPALLADIUM CHLORIDE COMPLEXES WITH ALCOHOLS", J. ORGANOMETAL. CHEM., vol. 13, 31 July 1967 (1967-07-31), XP055715839 *

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