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    • 专利摘要:
    A catalyst having a mixture of zinc and alumina as a base having a spinel structure which is overstoichiometric with respect to zinc, in which some of the zinc atoms are in the octahedral position, a process for its preparation and its use in a process for the preparation of a compound non-linear monocarboxylic acid alcohol esters having 6 to 26 carbon atoms from a neutral or acidic, virgin or recycled vegetable or animal oil, with monoalcohols having 1 to 18 carbon atoms, enabling the direct obtaining of an ester which can be used as a motor propellant or a fuel for heating and a pure glycerin in one or more steps.
    公开号:SE1051059A1
    申请号:SE1051059
    申请日:2010-10-11
    公开日:2011-04-15
    发明作者:Delphine Bazer-Bachi；Vincent Coupard；Sylvie Maury；Veronique Pugnet；Isabelle Clemencon；Anne-Agathe Quoineaud
    申请人:IFP Energies Nouvelles；
    IPC主号:
    专利说明:

    With regard to diesel fuels, which currently constitute a significant use of fat esters, a number of specifications have been prepared which, together with limit values and procedures, are listed in the standard EN 14214 (2003) which is currently applicable in Europe. The ester must contain at least 96.5% by weight of esters, not more than 0.8% by weight of monoglycerides, not more than 0.2% by weight of diglycerides and not more than 0.2% by weight of triglycerides, a small amount of free fatty acids (<0.5 mg KOH per g), which can be corrosive, less than 0.25% by weight of free and bound glycerin and metals only in traceable amounts. A detailed procedure is therefore required to obtain the desired purity.
    When an ester is prepared from an oil or a fat and a monoalcohol is formed, depending on the properties of the oil used from the beginning, -15% by weight of a co-product, namely glycerin. This glycerin can be used well in various applications, but must first be purified (removal of metals, salts and water). To achieve this purity, bee distillation in vacuum is often required.
    The majority of commercial processes for the production of esters produce, to summarize, simple crude products (esters and glycerin), but these must be carefully purified by various treatments which ultimately increase the cost of conversion.
    Preparation of methyl esters using conventional methods of homogeneous catalysis with soluble catalysts such as sodium hydroxide or sodium methylate are known, by reaction between a neutral oil and an alcohol such as methanol (e.g. JAOCS Q, 343-348 (1984)). However, a pure product that can be used as a motor fuel and glycerin that follows the standards is obtained only after a large number of steps. The glycerin obtained is de facto contaminated by the alkaline salts or alcoholates, so that the glycerin purification unit is almost as expensive as that for the preparation of the ester.
    Heterogeneous catalyst processes provide the advantage of producing esters and glycerin which are catalyst free and thus easy to purify. However, it is often difficult to economically obtain a high purity ester and glycerin at the same time.
    Several metal oxides have been used to catalyze the transesterification reaction.
    This was recently the case with zinc oxide supplemented with lithium (Xie et al., Ind. Eng. Chem.
    Res., 2007, 10.1021 / ie070597s) or barium (Xie et al., Catalysis Letters (2007) 117, 159-165). Reddy et al. (Energy Fuels, 2006, 20, 1310) suggest the use of nanocrystalline calcium oxide which, due to the formation of Ca (Ol / le) 2 species in the presence of methanol, has the character of a substantially heterogeneous catalyst. A number of authors have also studied the nature of magnesium oxide (Dossin et al., Applied Catalysis B, 2006, 61, 33-45). These alkaline earth metal oxides have no solubility in methanol (Gryglewicz, Bioresour. Technol., 1999, 70, 249), which gives rise to problems with leaching and stability of the catalysts, which causes a significant reduction in the activity of the recovery step and contamination of the effluents from the reaction. , resulting in a need to purify these to meet the specifications of the claims.
    The solution proposed for zinc oxide-based catalysts, which consists in regenerating the catalyst by impregnation with lithium or barium nitrate, cannot be adapted for industrial use. The leached metal species are also found in the ester and glycerin products, which causes a deterioration in their quality and means that the specifications that are applicable to diesel are not followed. European patent EP-B-0 198 243 describes the preparation of methyl esters by transesterification of an oil with methanol, by using an aluminum species, or a mixture of an aluminum species and iron oxide, as catalyst.
    However, the space velocity per hour (volume of oil injected / volume of catalyst / hour) is low, which means that the amount of glycerin collected is much lower than the theoretical calculation and the purity of the esters obtained is relatively low (93.5-98 ° / 0). .
    Processes using a catalytic system based solely on metal oxides or metal oxides in association, by deposition on aluminum or not, have been described. The patent FR-B-2 752 242, which belongs to the present applicant, describes the use of solid and insoluble catalysts formed from zinc and aluminum precursors. The solid used in this patent has the general formula ZnAl 2 O 4, x ZnO, y AlgO 2, wherein x and y are between 0 and 2.
    This solid can be prepared by co-precipitation at a pH of 6-8.
    The solids obtained by co-precipitation can generally be of different types depending on the selected execution conditions (ratio between zinc and aluminum precursors, calcination temperature, pH, conditions under which reagents are added, etc.). When a molar ratio of Zn to Al of 0.5 is used, a direct spinel-type solid of the formula ZnAl 2 O 4 (gahnit) can be obtained. For higher Zn / Al ratios, it is possible to obtain solids that are overstoichiometric with respect to zinc. Rossi, P.F. et al. Surface basicity of Mixed oxides: Magnesium and Zinc Aluminates. Langmuir 7, 2677-2681 (1991) describes a mixture of ZnO and zinc aluminates, said mixture having an atomic ratio of Zn to Al exceeding 0.5. These solids have a high basicity in terms of strength but not in terms of number. The increased base strength of these solids can be attributed to the ZnO present in the solid.
    These solids are not used as catalysts in transesterification reactions.
    The structure of the direct spinels (or true spinels) generally consists of a compact cubic arrangement in lattice with centered surfaces of oxygen. The bivalent cations (Znæ) are located at the tetrahedral coordination sites and the trivalent cations (Ala) are located at the octahedral coordination sites. In the case of an inverted spinel structure, trivalent cations are present at the tetrahedral coordination sites and di- and trivalent cations are present at the octahedral coordination sites.
    The inventors have surprisingly discovered that the process of synthesis by co-precipitation of aluminum and zinc precursors and application of specific performance conditions, specifically a constant pH of 6.1-6.9, preferably 6.3-6.9 during the synthesis and a Zn / Al atomic ratio of 0.53-0.60, preferably 0.56-0.58, allows a single spinel phase that is overstoichiometric with respect to zinc to be obtained in which some of the zinc atoms are located at the octahedral sites. This overstoichiometry with respect to zinc gives the material a catalytic effect which is interesting in reactions with transesterification of fats and gives yields of the esters to be obtained which are much higher than those obtained with a stoichiometric solid (Zn / Al = 0.5 ). The fact that this zinc aluminate-based solid in particular is free of ZnO means that the problems of Zn leaching in the ester and glycerin products, which degrade them and prevent them from complying with the specifications required by the standard EN 14214 applicable to biodiesel, can be avoided. .
    Detailed Description of the Invention The present invention relates to a heterogeneous catalyst having a spinel-type zinc aluminate base which is overstoichiometric with respect to zinc, a process for its preparation and its use in a process for the preparation of monocarboxylic acid alcohol esters from fatty substances of vegetable or animal origin.
    The catalyst has a zinc aluminate base free of ZnO, aluminum or ZnAl 2 O 4, wherein the zinc aluminate phase consists of a single zinc aluminate of the spinel type which is overstoichiometric with respect to zinc, wherein the Zn / Al atomic ratio is 0.53-0.60, preferably to 0.56-0.58. At least a portion of the zinc is present in the octahedral position of the spinel structure.
    Said catalyst is prepared by co-precipitation of precursors of aluminum and zinc in a Zn / Al atomic ratio amounting to 0.53-0.60, preferably amounting to 0.56-0.58.
    Said catalyst with spinel structure is overstoichiometric with respect to zinc relative to ZnAl 2 O 4, but does not contain ZnO or aluminum phases; the excess of zinc relative to the stoichiometry is located in an octahedral position rather than the tetrahedral position which is the case for true spinels. Although it does not contain ZnO, these solids have other specific basic properties (large number of basic sites) which is consistent with their improved catalytic activity compared to a stoichiometric ZnAl2O4 phase. For a Zn / Al ratio amounting to 0.63, a ZnO phase is detected by XRD and in this case the strength of the basic sites increases.
    The catalyst used in the present invention is preferably prepared according to a process comprising: a co-precipitation step comprising mixing precursors of zinc II and aluminum III in the presence of a base, at a pH in the range of from 6.1 to 6.9, preferably from 6.3 to 6.9, and at a temperature of 30-50 ° C; a step of filtering the precipitate obtained; - an optional washing step to remove the remaining species; a step of drying at a temperature of from 80 to 175 ° C, preferably for a period of 12-24 hours; a calcination step in the presence of oxygen at a temperature of from 500 to 800 ° C, preferably for a stable period of 1-4 hours.
    The precursors can be selected from the salts of zinc and aluminum: for example nitrate, sulphate, acetate, chloride, from alkoxides of zinc and aluminum. Aluminum can also be introduced in the form of sodium aluminate. The precipitation can be carried out using an aqueous solution of sodium carbonate or of sodium bicarbonate, alone or in combination with a solution of ammonia or sodium hydroxide or any other base which allows the pH to be maintained during the synthesis. The synthesis can also be performed using only one base: sodium hydroxide, ammonia, or any other base that allows the pH to be adjusted or even a solution of sodium aluminate. The pH can be adjusted with an acid if basic precursors are used.
    Zinc cross-stoichiometry with respect to zinc associated with this synthesis process by co-precipitation allows a simple spinel phase to be obtained with zinc atoms in the octahedral position and gives the material an interesting catalytic effect.
    The mixed oxide obtained is characterized by X-ray diffraction (XRD), NMR, IR and CO 2 microcalometry.
    Characterization of the structure by XRD: The structure of these materials is characterized by X-ray diffraction on powder for the purpose of determining the lattice parameter and the stoichiometry of the spinel.
    The most intense positions of the instrumental rays observed for these solids are as follows: 31.2 ° 29, 36.8 ° 26, 44.7 ° 29, 49 ° 29, 55.6 ° 29, 59.3 ° 26 , 65.1 ° 26, 74 ° 29, 77.2 ° 26, 90.8 ° 26, and 93.9 ° 29. These correspond to the rays of a spinel.
    The lattice parameter and the stoichiometry of the solid can be determined by refining the X-ray diffraction diagrams using the Rietveld method, which is a conventional method known to those skilled in the art.
    This method consists of minimizing integrated intensity differences between an experimental diagram and the diagram calculated using crystallographic models of the present phases, by refining the beam profiles and the structural parameters, in particular the level of possession of the tetrahedral and octahedral sites on the lacunar. the structure of the spinel type. Two types of restrictions were introduced to obtain reasonable solutions: maintaining the elemental composition of the mixture and electron neutrality.
    The level of possession of Zn and Al at the octahedral and tetrahedral sites of the true spinel phase varies.
    The level of possession is the ratio between the number of atoms per site and the number of equivalents at the general position (192 for the spinel structure). It represents the electron density at each site (28 e 'for Znz * and 10 e' for Alæ).
    If the balance of the positive charges [(Zn2 * (tetra) + Al3 + (octa))] does not correspond to the balance of the negative charges provided by Ozlions, equilibrium between the charges will be re-established either by a contribution of Al 'ions in the tetrahedral position. if there is a deficit of positive charges, or by a contribution of Znzïjoner in the octahedral position in the opposite case.The constraints applied to the system are maintaining the electron density measured at each site and electron neutrality of the grating.
    The results of the XRD characterization give the stoichiometric composition which exhibits overstoichiometry with respect to zinc. The increase in the zinc content causes an increase in the lattice parameter.
    Characterization of the structure by NMR: The structure of the solid can also be subjected to nuclear magnetic resonance (NMR) characterization. The aluminum atoms present in the zinc aluminate catalysts are present in a tetrahedral (Alw) and octahedral (AIW) geometry. From a quantitative perspective, the proportions of the different aluminum species can be determined by breaking down 27Al MQMAS and MAS spectra to correct the intensity of their dependence on the quadripolar interaction. NMR for “Al performed using magnetic angular spin (MAS) and multi-quantum MAS (MQMAS) techniques shows a change in the local geometry and the electronic state of the aluminum sites. For catalysts that are understochiometric with respect to zinc, the zinc occupies the tetrahedral position and the relative amount of tetrahedral aluminum falls. The formed spinel is a direct spinel. For the zinc stoichiometric catalysts encompassed by this invention, zinc occupies the octahedral position which involves a change in quadripolar parameters of the octahedral aluminum species and a decrease in their relative proportion. These results are in perfect agreement with the X-ray diffraction assay.
    These solids that are overstoichiometric with respect to zinc have specific basic properties that are consistent with their improved catalytic activity over a stoichiometric ZnAl2O4 phase. The number and strength of the basic sites can be characterized by techniques well known to those skilled in the art, such as infrared spectrometry with probe molecules or microcalorimetry.
    Characterization of the base acid balance (number of sites) by absorption of probe molecules and IR spectroscopy: Acetonitrile is an amphoteric probe molecule with low basicity that is used for characterization of both basicity and acid strength. It provides access to a basic acid balance in the surface being studied. Thanks to its electron doublet on the nitrogen atom, the molecule behaves like a base or electron donor. The adsorption at room temperature of CH3CN is expressed as a disturbance of the vibration frequencies of the hydroxyl groups and of the CN bond. The adsorption of CHgCN also allows the characterization of a number of basic sites. Its adsorption at these sites leads to the formation of the CH 2 CN anion: O 2 '(surface) + CH 3 CN -r OH "(surface) + CH 2 CN' (adsorbed) The adsorption gives acid / base character of O 2 / OH 'and CH 3 CN / CH 2 CN pairs and a cationic site for stabilizing the CH 2 CN anion The wavelength v (CEN) of the carbonization characterizes the cationic center For ZnO the wavelength l / (CEN) now amounts to 2 121 Cm-ï This technique for characterizing spinel-type solids which is superior to stoichiometric with respect to zinc shows that the number of basic sites is much higher in spinel-type solids that are over-stoichiometric with respect to zinc compared to the number of sites in stoichiometric gait.
    Characterization of the strength of basic sites by CO 2 microcalorimetry: To measure the change in the strength of the basic sites as a function of the Zn content of the solids, measurements of the heat adsorption of CO 2 were performed by microcalorimetry on these materials. They show that the strength of the sites is maintained at approximately the same level for the solids that make up the invention.
    The texture (specific surface area) of the mixed oxide is characterized by nitrogen volumetric analysis. The material used in the present invention also has a Zn / Al atomic ratio of 0.53-0.6O and a specific surface area of 45-155 m 2 / g.
    Transesterification The present invention also describes a process for the preparation of a compound having linear monocarboxylic acid alcohol esters having 6 to 26 carbon atoms and glycerin wherein a fatty substance of animal or vegetable origin is reacted with an aliphatic monoalcohol containing 1 to 18 carbon atoms, in the presence of at least one zinc aluminate based catalyst. is free of ZnO, aluminum or ZnAl2O4, wherein the zinc aluminate phase consists of a simple spinel-type zinc aluminate phase which is overstoichiometric with respect to zinc wherein the Zn / Al atomic ratio is 0.53-0.6, preferably 0.56-0.58.
    The spinel containing zinc atoms in the octahedral position gives the material an interesting catalytic effect.
    Fats The fats used in the process of the invention correspond to natural or processed substances of animal or vegetable origin, which mainly contain triglycerides, which are commonly referred to as oils and fats.
    The oils that can be used include all the usual oils such as palm oil (hardened or olein), soybean oil, palm kernel oil, copra oil, babassu oil, rapeseed oil (old or new), sunflower seed oil (conventional or oily), barley or cotton seed oil, peanut oil ) oil, castor oil, flaxseed oil and cress oil and all oils obtained from, for example, sunflowers or rapeseed which have been genetically modified or hybridized or even obtained from algae.
    It is also possible to use frying oils, lubricating oils and various animal oils, such as fish oil, seal oil and lubricating oils, tallow, bacon and also fats obtained from wastewater treatment and also bird fats, because the esters prepared from various alcohols such as ethyl alcohol, isopropyl alcohol or butyl alcohol allows the pour point to be lowered by more than 10 ° C and the use of more saturated oils can consequently be used from the start.
    The oils used also include oils which have been partially modified by, for example, polymerization or oligomerization, such as, for example, stand oils from flaxseed and sunflower oils and blown vegetable oils.
    The oils used are neutral or acidic, virgin or recycled.
    The presence of fatty acid in the oils is not in itself harmful. However, in the case of oils with a very high acid index (closer to 10 mg KOH / g), it is possible to have the transesterification reaction preceded by a reaction with esterification of the present free fatty acids, either by using the same alcohol as that used in the transesterification process in the presence of a strong acid such as sulfuric acid or soluble sulfonic acid or sulfonic acid on support (of the Amberlyst 15® resin type) or preferably by using glycerin with the same catalytic system as that used for the transesterification reaction, to form a total or partial glycerol ester, at atmospheric pressure and preferably under vacuum and at a temperature of from 150 to 220 ° C.
    When frying oils are used, which are a very cheap starting material for the production of biodiesel, it is necessary to remove fatty acid polymers from the reaction mixture so that the ester mixture complies with the specifications in the standard EN 14214.
    Alcohol The type of alcohol used in the procedure plays a role in the activity of transestification.
    It is generally possible to use different aliphatic monoalcohols which contain, for example, 1-18 carbon atoms, preferably 1-12 carbon atoms.
    More preferably, the aliphatic monoalcohol contains 1-5 carbon atoms. 12 The most active is methyl alcohol. However, ethyl alcohol and isopropyl, propyl, butyl, isobutyl and even amyl alcohols can be used. It is also possible to use heavier alcohols, such as ethyl hexyl alcohol or lauryl alcohol.
    Methyl alcohol can also be advantageously added to the heavier alcohols to facilitate the reaction.
    Furthermore, when the ethyl ester is prepared, a mixture of ethyl and methyl alcohol can be used, which contains 1-50% by weight, preferably 1-10% by weight, of methyl alcohol to increase the conversion.
    Conditions for carrying out the transesterification reaction The process is carried out at temperatures in the range from 130 to 220 ° C, at an internal pressure of less than 10 MPa and with an excess of monoalcohol relative to the fat / alcohol stoichiometry. After the reaction, the excess alcohol is evaporated and the glycerin is separated, preferably by decantation.
    The reaction can generally be carried out using various methods of operation.
    If a non-continuous reaction is used, one or two steps may be used, i.e. an initial reaction is carried out up to 85-95 ° / 0 conversion to esters, cooling by evaporation of the excess alcohol, decantation of the glycerin and completion of the reaction by reheating to 130-220 ° C and addition of alcohol to obtain complete conversion.
    One can also aim for 98% conversion to esters by performing for a sufficiently long period of time in a single step under suitable conditions, for example by increasing the temperature and / or the ratio of alcohol to fat.
    If a continuous reaction is performed, a number of autoclaves and decanters can be used. In the first case, a partial conversion is usually carried out which amounts to less than 90% and generally about 85% followed by decantation of the alcohol 13 by evaporation and cooling; in a second reactor, the transesterification reaction is completed under the conditions indicated, adding a portion of the previously evaporated alcohol. The excess alcohol is finally evaporated in an evaporator and the glycerin and esters are separated by decantation.
    If a continuous fixed bed process is chosen, operation at temperatures from 130 to 220 ° C, preferably 150-180 ° C, and at pressures from 1 to 7 MPa is advantageous, with the space velocity of the liquid per hour preferably amounting to 1-3, , preferably 0.3-2, in the first step and the weight ratio of alcohol to oil varies from 3/1 to 0.1 / 1.
    At the end of these two steps, a biodiesel is thus obtained which meets the specifications. The degree of conversion is adjusted to obtain a motor fuel ester that meets the specifications and a high-purity glycerin, the operation taking place in one or two steps.
    The ester and glycerin obtained do not contain impurities from the catalyst.
    As a result, no purification treatment needs to be performed to remove the catalyst or residues thereof, unlike catalysts which operate according to a homogeneous process in which the catalyst or its residues after the reaction are located in the same phase as the ester and / or glycerin.
    The action and selectivity of this catalyst are not affected by the transesterification or esterification reaction: the catalyst is stable and can be recovered under the experimental conditions of the reaction. This type of catalyst is compatible with use in a continuous industrial process, for example in a fixed bed, and in which the charge of the catalyst can be used for a very long period of time without losing its effect. The catalyst used in the present invention can be implemented in the form of powders, pellets, extrudates or beads.
    The resistance to leaching of the catalyst is verified by measuring the content of dissolved trace metals from the catalyst, both in the ester formed and in the glycerin produced, of less than 1 ppm, and by the stable action of the catalyst over time. Examples The following examples describe the invention without limiting its scope, with Example 1 being provided by way of comparison.
    Example 1 relates to the preparation of a solid by mixing, wherein the Zn / Al ratio is in the range covered by the invention but wherein the crystalline phases differ from the solid according to the invention. In particular, it contains a ZnO phase.
    Example 2 describes, in a non-limiting manner, the preparation of a series of catalysts in accordance with the invention, which are prepared by co-precipitation, and the characterization thereof.
    Example 3 presents the catalytic tests and describes the catalytic interest of solids in accordance with the invention.
    The X-ray diffraction measurements are performed using a Bragg-Brentano type powder diffractometer in G-B configuration and equipped mainly with copper X-ray tubes (Ä = 1.5402 Å), a rear monochromator and a dot detector. The recording conditions are as follows: tube power of 35 kV and mA, sample height (sampling pitch) 0.04 ° 20, time for counting in 10 second steps. The angular area examined ranges from 2 to 100 ° 20.
    The sample was analyzed by N1 / IR MAS and aluminum MQMAS 27 using a Bruker Avance 400 MHz (9.4T) spectrometer in a 4 mm probe. The pulse sequences used are MAS-selective (low radio frequency field of the order of kHz and pulse angle 1T / 12) and MQMAS "z-filters" which are each synchronized to the rotational speed. The rotation speed is 14 kHz.
    The solids are characterized by IR in transmission mode using a Nexus-type ThermoFischer spectrometer equipped with a DTGS or MCT detector. Spectra are obtained after Fourier transformation of 69 interferograms that have accumulated between 4,000 and 90 cm "with a resolution of 4 cm".
    The characterization of the acido-basicity is carried out via adsorption of the acetonitrile (probe molecule). This is done by adding controlled quantities using a standard volume and a pressure gauge. Prior to adsorption, a sample activation step is performed. This is a heat treatment under secondary vacuum (10 hours at 500 ° C for 1006 Torr).
    The preparation of the sample before the IR characterization was carried out as follows: 20 mg of the solid is compressed at 150 kg / cm 2 in the form of a self-supporting pellet 16 mm in diameter.
    The basicity of the solids was also studied by adsorption of CO 2 by microcalorimetry. The device used was an instrument of the type SETARAM TG-DSC-111. The samples are first activated at 500 ° C under a helium flow and then returned to 100 ° C. A CO 2 stream is then contacted with the sample at 100 at 0.01 ° C and the variation in weight of the sample and the thermal events are measured simultaneously.
    Example 1 (Comparative): Preparation of a solid A1 as a reference by mixing The solid A1 is prepared by mixing boehmite and zinc oxide in the presence of 5.8% nitric acid in aqueous solution, to obtain a composition of the material whose elemental analysis is 37% Zn and 28.6% Al (Zn / Al = 0.54).
    The catalyst is extruded into a 3 mm diameter mold and undergoes heat treatment at 650 ° C for 2 hours.
    The surface area of the solid A1 is 149 m2 gf 16 The X-ray diffraction enables a quantitative determination of the different phases.
    Zinc oxide ZnO and two solid solutions are detected, one of which contains a lot of zinc and the other a lot of aluminum.
    The analysis by structural improvement allows the composition of each of these phases to be obtained: ZnWAIZOW (51%, lattice parameter 8.08 Å) and Zn0.33A | 2O3_33 (22%, lattice parameter 8.01 Å).
    Example 2: Preparation of the solids B1, B2, B3, B4 and B5 The solid is obtained by combined precipitation of the precursors of zinc and aluminum (aqueous solution of zinc nitrate and aluminum nitrate), in such a way that the Zn / Al ratio corresponds to the relationship you want in the resp. the final material (here 0.28, 0.50, 0.56, 0.58 and 0.63), the pH being kept constant at 6.5 for the materials with the names B1, B2, B3, B4 and B5. The pH is kept constant by adding a base (ammonia in aqueous solution 225 g / l) throughout the synthesis.
    The synthesis takes place as follows: A water blanket is introduced into a double-walled glass reactor of borosilicate which has been provided with a splash shot and is then heated to 40 ° C while being stirred with a mobile device with three inclined blades.
    The precursors and the base are introduced into the reactor via a pump system which enables control of the introduced quantities and the synthesis time. PH control is provided by the base additive pump: this is kept constant at 6.5 i- 0.2 throughout the co-precipitation.
    The contents of the reactor are then filtered on a Büchner funnel. The resulting cake is dried at 150 ° C for 16 hours in a ventilated oven and then calcined at 650 ° C (rising temperature of 5 ° C / minute and stable for 2 hours at 650 ° C) in a muffle furnace. An X-ray fluorescence (XRF) analysis was performed on the five materials. The contents obtained after correction for loss due to firing performed at 550 ° C for 4 hours resulted in the Zn / Al ratios presented in TabeH1.
    The X-ray diffraction allows a determination of their lattice parameters. All these data are shown in Table 1.
    Table 1: Main properties regarding structure and elemental composition of the solids Zn / Ål atomic ratio Designation (FX) improvement (Å) Production% ZnO process Lattice parameter after Mixed 0.54 8.08 A1 8.01 (non-conforming) 27, 5 Co-precipitated B1 (non-compliant) 0.28 8.066 0 Co-precipitated B2 (non-compliant) 0.50 8.089 0 Co-precipitated B3 (non-compliant) 0.56 8.095 0 Co-precipitated B4 (non-compliant) 0.58 8.097 0 Co-precipitated B5 (non-compliant) The solid A1 is prepared by mixing and contains ZnO. The solid B1 is a spinel-type zinc aluminate which is sub-stoichiometric with respect to zinc (not in accordance with the invention). The solid B2 is stoichiometric (not in accordance with the invention). The solids B3 and B4 are zinc aluminates of spinel type which are overstoichiometric with respect to zinc, in accordance with the invention. The solid B5 is a spinel-type zinc aluminate which is overstoichiometric with respect to zinc having an atomic ratio of 0.63 (not in accordance with the invention). In the case of B5, the presence of a ZnO phase is observed. The increase in the zinc content causes an increase in the lattice parameter. For a Zn / AI ratio of 0.56, the lattice parameter of the solid exceeds that of a stoichiometric spinel ZnAl2O4 (8.09 Å).
    The specific surface area of the five solids B1 to B5 was estimated by volumetric analysis with nitrogen at low temperature in accordance with the standards ASTM D 3663-84 or NFx 11-621: it ver155 m2 / g, 74 m2 / g, 76 mZ / g , 58 m 2 / g resp. 46 mz / g, for the solids B1, B2, BS, B4 and B5.
    The present surface locations (strength / number) of these solids were characterized by quantification of the acid / base balance by IR with acetonitrile adsorption and by microcalorimetry.
    IR with acetonitrile probe molecule shows an increase in the number of basic sites when moving from the direct spinel to the spinels in which some of the zinc atoms are located in the octahedral position. Fig. 1 shows the effect of the zinc content on the number of basic sites and the base / acid balance measured by acetonitrile as a function of the zinc content. The number of basic sites increased significantly (from 12 to 17 UA / mz) when changing from a Zn / AI amounting to 0.5 (B2) to 0.56 (B3).
    Fig. 2 shows the effect of the zinc content on the heat adsorption of CO 2 on the solids, which is measured by microcalorimetry. It is noted that the strength of the basic sites corresponds to each other for the solids B2 and B3.
    Finally, an increase in the number of basic sites can be seen without an increase in their strength coupled with the introduction of zinc atoms in the octahedral position, in the simple spinel type phase constituting the solid, the latter phenomenon occurring when the ratio of Zn to Al exceeds 0.5. (corresponding to the stoichiometry of the true spinel). Example 3: Testing of the catalysts: comparative catalytic activities of the different solids with varying Zn / Al, A1, B1, B2, B3, B4 and B5 The solids A1 and B1 to B5 were tested as catalysts in a reaction with transesterification of a fatty substance.
    These tests were performed in a batch reactor and thus in a single step. To obtain a biodiesel that meets the specifications, it would be necessary to proceed at the end of this first step with an evaporation of the alcohol followed by decantation and cooling of the medium, followed by separation of the glycerin and of the ester phase, after which it would be necessary to complete the transesterification reaction. by re-adding a portion of the evaporated alcohol to the ester fraction.
    The oil used in these examples is food grade rapeseed oil, the fatty acid composition of which is as follows: Table 2: Rapeseed oil composition Fatty acid glyceride Fatty chain nature Weight% Palmitic acid C16: 0 Palmitoleic acid C16: 1 <0.5 Stearic acid C18: 0 2 Oleic acid C18: 0 2 1 59 Linoleic acid C18: 2 21 Linolenic acid C18: 39 Arachidic acid C20: 0 <0.5 Gadoleic acid C20: 1 1 Behenic acid C22: 0 <0.5 Erucaic acid C22: 1 <1 However, any other oil of vegetable or animal origin could provide similar results.
    Analyzes of products by quantitative analysis of chlorides and esters in the ester phase: Samples are taken in the usual way during the test to monitor the progress of the reaction.
    The samples taken are washed in an aqueous solution saturated with NaCl and then, after decanting, the higher organic phase, which is diluted in THF, is analyzed by GPC (gel permeation chromatography - or steric exclusion chromatography). The steric exclusion chromatography enables the separation of the products according to their steric size / dimension.
    The equipment used is an HPLC equipment of the WATER type, which is equipped with 3 Waters control gel columns (THF) with a molar mass scale amounting to 0-1,000 g.mol-1. These columns are placed in a thermostatically controlled oven at 40 ° C. The detector is a Waters 2414 refractometer.
    Catalytic test: In a closed reactor at room temperature, 25 g of rapeseed oil, 25 g of methanol and 1 g of the catalyst prepared as described in Example 1 or Example 2 are introduced in powder form. The weight ratio between methanol and oil is thus 1, which corresponds to a molar ratio of 27.5. The reactor is then closed, stirred (200 rpm) and heated to 200 ° C using a magnetic stirrer with hot plate.
    The temperature of the reaction medium is stabilized at 200 ° C after 30 minutes of heating. The pressure is the gas pressure of the alcohol at the working temperature, which is about 40 bar. The reaction is started when the temperature of the reaction medium has reached the predetermined point, samples being taken after 1, 2 and 4 hours, and the samples being analyzed by GPC. The following table summarizes the results obtained for the samples after 1, 2 and 4 hours of reaction for A1 and B1 to B5. Table 3:% RME (rapeseed methyl ester) in the glyceride phase over time for the tests performed with the series of solids A1, B1, B2, B3, B4 and B5 Sampling time (h) 1 2 4 A1 (non-compliant) 11.8 .6 55.4 B1 (non-compliant) 9.9 16.3 28.1 B2 (non-compliant) 13.8 29.3 58.7 B3 (compliant) 26.3 58.6 85.4 B4 (compliant) 55.3 79.2 86.0 B5 (non-compliant) 74.5 81.4 86.2 For conversions far from the thermodynamic equilibrium (1 and 2 hour reaction), the exchange of RME with the solid B3 is double as high as the yield obtained with the solid B2. The solids B3 and B4 enable ester yields to be obtained which are significantly higher than those obtained with the stoichiometric solid B2. B5 exhibits a very high activity linked to the presence of a ZnO phase. Its catalytic activity is partly linked to these zinc species which leach into the reaction medium, and in addition the strength of these basic sites on ZnO is higher than that of direct spinels. The fact that the solids B3 and B4 are appreciably free of ZnO means that the problems of leaching of Zn can be avoided in the ester and glycerin products while a catalytic activity comparable to that of catalysts containing ZnO can be achieved.
    权利要求:
    Claims (15)
    [1]
    A catalyst with a zinc aluminate base, which is free from ZnO, aluminum or ZnAl2O4, wherein the zinc aluminate phase consists of a single spinel-type zinc aluminate phase that is overstochiometric with respect to zinc, wherein the Zn / Al atomic ratio is 0.53-0.60.
    [2]
    A catalyst according to claim 1, wherein the Zn / Al atomic ratio is 0.56-0.58.
    [3]
    Catalyst according to claims 1-2, wherein at least a part of the zinc occupies the octahedral position of the spinel structure.
    [4]
    A process for preparing the catalyst according to claims 1-3, comprising the following steps: a) a co-precipitation step comprising mixing precursors of zinc II and aluminum III in a Zn / Al atomic ratio amounting to 0, 53 -0, 60, preferably 0.56-0.58, in the presence of a base, at a pH of 6.1-6.9, preferably 6.3-6.9, and at a temperature of 30-50 ° C ; b) a step of filtering the precipitate obtained; c) an optional washing step to remove the remaining species; d) a step of drying at a temperature of 80-175 ° C, preferably for a period of 12-24 hours; e) a calcination step in the presence of oxygen at a temperature of 500-800 ° C, preferably for a stable period of 1-4 hours.
    [5]
    A production process according to claim 4, wherein said precursors of zinc II and aluminum III are selected from the group consisting of nitrate, sulphate, acetate and chloride salts of zinc and / or aluminum, zinc and / or aluminum alkoxides and sodium aluminate.
    [6]
    A production process according to claims 4 and 5 wherein said base is selected from the group consisting of an aqueous solution of sodium carbonate, an aqueous solution of sodium bicarbonate, a solution of ammonia, a solution of sodium hydroxide, a solution of sodium aluminate or mixtures of at least two of these solutions.
    [7]
    Process for the preparation of a compound of alcohol esters of a linear monocarboxylic acid having 6-26 carbon atoms and glycerin, wherein a fatty substance of vegetable or animal origin is reacted with an aliphatic alcohol containing 1-18 carbon atoms, in the presence of at least one catalyst according to claims 1-3 or prepared by the process according to claims 4-6.
    [8]
    The method of claim 7, wherein the aliphatic monoalcohol is methanol.
    [9]
    Process according to any one of claims 7-8, wherein a temperature of 130-220 ° C is used, at an internal pressure of less than 10 MPa and with an excess of aliphatic monoalcohol relative to the stoichiometry for fat / alcohol.
    [10]
    A process according to any one of claims 7-9, wherein the aliphatic monoalcohol is evaporated and the glycerin is separated, preferably by decantation, after the transesterification reaction.
    [11]
    A process according to any one of claims 7-10 wherein the reaction is carried out batchwise.
    [12]
    A process according to any one of claims 7-10 wherein the reaction is carried out continuously, on a fixed bed or with autoclaves and decanters in series.
    [13]
    A process according to claim 12, wherein the reaction is carried out on a fixed bed, at a temperature of 130-220 ° C, preferably 150-180 ° C, at a pressure of 1-7 MPa, and a space velocity per hour for the liquid amounting to 0, 1-3, preferably 0.3-2, with a weight ratio of alcohol to fat amounting to 3/1 to 0.1 / 1.
    [14]
    Process according to any one of claims 7-13, wherein the fatty substance is selected from palm oil (hardened or olein), soybean oil, palm kernel oil, copra oil, babassu oil, rapeseed oil (old or new), sunflower oil (conventional or oily), barley oil, cottonseed oil, peanut oil, , castor oil, flaxseed oil and cumin oil, algae and oils obtained from sunflowers or rapeseed by means of genetic modification or hybridization, oils partially modified by polymerisation or oligomerization, frying oils and lubricating oils, fish oil and seal oil, poultry fat, tallow, bacon and fat obtained wastewater treatment.
    [15]
    A process according to any one of claims 7-14, wherein the catalyst is in the form of a powder, extruded bead or pellet.
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    同族专利:
    公开号 | 公开日
    US9597659B2|2017-03-21|
    MY175808A|2020-07-09|
    BRPI1003931A2|2013-02-13|
    FR2951092B1|2013-03-08|
    US20110092730A1|2011-04-21|
    FR2951092A1|2011-04-15|
    ES2370700B1|2012-10-26|
    SE535407C2|2012-07-24|
    ES2370700A1|2011-12-21|
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    法律状态:
    2015-06-02| NUG| Patent has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    FR0904932A|FR2951092B1|2009-10-14|2009-10-14|ZINC SUPER-STOICHIOMETRIC ZINC ALUMINATE SPINEL HETEROGENEUS CATALYST AND USE THEREOF IN A PROCESS FOR THE PREPARATION OF ALCOHOL ESTERS FROM TRIGLYCERIDES AND ALCOHOLS|
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