Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/09—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid esters or lactones

Definitions

• the invention generally relates to the field of catalysis and, in particular, to mixed oxide catalysts for the preparation of 2,3-unsaturated carboxylic acids.
• the invention further relates to the preparation of 2,3- unsaturated carboxylic acids using a methylene dialkanoate feed with a mixed oxide catalyst.
• 2,3-Unsaturated carboxylic acids and esters can be prepared from the reaction of a formaldehyde (H 2 CO) source and a saturated carboxylic acid or ester containing one less carbon atom.
• a formaldehyde (H 2 CO) source and a saturated carboxylic acid or ester containing one less carbon atom.
• acrylic and methacrylic acid derivatives can be prepared from the condensation of a formaldehyde source with acetic or propionic acid derivatives, respectively. The reaction produces one equivalent of water for each equivalent of carboxylic acid derivative reacted.
• the conventional process for these aldol condensation reactions combines a formaldehyde source, such as trioxane, with a carboxylic acid to form water, the 2,3-unsaturated carboxylic acid, and formaldehyde.
• the formaldehyde can react with itself at any time during the reaction to form paraformaldehyde. This by-product formation of paraformaldehyde can contribute to yield losses and increased maintenance costs as the
• One solution is to introduce a methylene unit by an alternative feed that does not utilize or produce formaldehyde which can polymerize to paraformaldehyde.
• a methylene dialkanoate feed can be used as such an alternative feed.
• V-Ti-P catalysts of the present invention function with the presence of water, improved STY can be seen by attenuating the effects of water.
• One approach to reduce the presence of water in the feed is to replace aqueous formaldehyde with anhydrous formaldehyde (trioxane, C 3 H 6 O 3 ).
• trioxane C 3 H 6 O 3
• the molar addition of trioxane with acetic acid still includes one mole of a latent molecular water, thereby limiting the maximum attainable rate.
• methylene dialkanoates such as methylene diacetate (MDA) and methylene
• MDP dipropionate
• formaldehyde can be synthesized from formaldehyde and utilized as a feed towards the production of acrylic acid and methacrylic acid, respectively.
• methylene dialkanoates are molecularly equivalent to one mole of formaldehyde and two moles of the corresponding carboxylic acid but without the latent molecular water (i.e. one mole of latent water is not produced).
• MDA and MDP form acrylic acid and methacrylic acid, respectively, over the V-Ti-P catalyst at a surprisingly high reaction rate and yield.
• V-Ti-P Vanadium-titanium-phosphorus
• the present invention provides a catalyst
• the titanium component of the catalyst composition is derived from a water-soluble, redox-active organo-titanium compound.
• the present invention provides a method for preparing a catalyst composition comprising a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the method comprises the steps of :
• the present invention provides a process for preparing a 2,3-unsaturated carboxylic acid.
• the process comprises the step of contacting a formaldehyde source with a carboxylic acid in the presence of a condensation catalyst under vapor-phase condensation conditions to obtain the 2,3-unsaturated carboxylic acid.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the titanium component of the condensation catalyst is derived from a water-soluble, redox-active organo-titanium compound.
• the present invention provides a process for preparing a 2,3-unsaturated carboxylic acid.
• the process comprises the steps of contacting a methylene dialkanoate and a diluent gas with a condensation catalyst under vapor-phase condensation conditions to obtain the 2,3-unsaturated carboxylic acid.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• V vanadium
• Ti titanium
• P phosphorus
• R is selected from the group consisting of hydrogen and an alkyl group having 1 to 8 carbon atoms.
• the present invention provides a process for preparing a 2,3-unsaturated carboxylic acid.
• the process comprises the step of contacting a methylene dialkanoate and a diluent gas with a condensation catalyst under vapor-phase condensation conditions to obtain the 2,3- unsaturated carboxylic acid.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the titanium component is derived from a water-soluble, redox-active organo-titanium compound.
• the methylene dialkanoate has the general formula (I):
• R is selected from the group consisting of hydrogen, methyl, ethyl, propyl, and isopropyl.
• Figure 1 is a graph showing the X-ray diffraction pattern of the amorphous catalyst prepared via Method A in Example 1 .
• Figure 2 is a graph showing the X-ray diffraction pattern of the amorphous catalyst prepared via Method B in Comparative Example 1 .
• Figure 3 is a graph showing the X-ray diffraction pattern of the mixed amorphous-crystalline (TiO 2 ) catalyst prepared via Method C in Comparative Example 2.
• Figure 4 is a graph showing the X-ray diffraction pattern of the crystalline [VO(HPO 4 )(H 2 O) 0 5 ] catalyst prepared via Method D in Comparative Example 3.
• Figure 5 is a graph showing the X-ray diffraction pattern of the crystalline catalyst [(VO) 2 (P2O 7 )] prepared via Method E in Comparative Example 4.
• Figure 6 is a graph showing the X-ray diffraction pattern of the crystalline catalyst (TiO 2 ) prepared via Method F in Comparative Example 5.
• Figure 7 is a graph showing the X-ray diffraction pattern of the amorphous catalyst prepared via Method G in Example 2.
• Figure 8 is a graph showing the X-ray diffraction pattern of the crystalline catalyst [V(PO 3 )3 and Ti(P 2 O 7 )] prepared via Method H in
• Figure 9 is a graph showing the X-ray diffraction pattern of the amorphous catalyst prepared via Method I in Example 5.
• Figure 1 0 is a graph showing the X-ray diffraction pattern of the amorphous catalyst prepared via Method J in Example 6.
• V-Ti-P mixed oxide catalysts can be prepared from a water-soluble, redox-active organo-titanium source. Employing such a titanium source can provide an inherently safer, and more practical and rapid route to V-Ti-P materials.
• the resulting catalysts can have a higher surface area and acidity, and can be more active for acrylic acid formation when an aqueous formaldehyde source and acetic acid are used as the feed.
• the resulting catalyst can be even more active for the formation of acrylic acid and methacrylic acid from MDA and MDP, respectively.
• the present invention provides a catalyst composition comprising a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the titanium component of the catalyst composition is derived from a water-soluble, redox-active organo-titanium compound
• the term "and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed.
• the composition can contain A alone; B alone; C alone; A and B in combination ; A and C in combination; B and C in combination ; or A, B, and C in combination.
• water-soluble it is meant that the organo-titanium compound can dissolve in water at 20 Q C and 1 atm absolute (1 01 .325 kPa) to form a homogeneous solution of at least 1 weight percent of the organo-titanium compound.
• the compound can dissolve in water to form a homogeneous solution of at least 25 weight percent. More preferably, the compound can dissolve in water to form a homogeneous solution of at least 40 weight percent.
• redox-active it is meant that the organic ligand of the organo- titanium compound is capable of reducing the oxidation state of vanadium from +5 to +4, +5 to +3, or +4 to +3.
• the organo-titanium compound is "redox-active” if the derivative of the organo-titanium compound, in the aqueous mixture used to make the catalyst, is capable of reducing the oxidation state of vanadium from +5 to +4, +5 to +3, or +4 to +3.
• titanium lactates examples include titanium lactates, titanium alkanolamines, and titanium acetylacetonates.
• Such compounds are commercially available, such as from Dorf Ketal under the trade name TYZOR®.
• Practical examples of such compounds include titanium(IV) bis(ammonium lactate)di hydroxide
• the organo-titanium compound comprises titanium(IV) bis(ammonium lactate)di hydroxide.
• the catalyst composition of the invention can be supported on an oxide support.
• Suitable oxide supports include silica, alumina, titanium oxide, zirconium oxide, and titanium or zirconium pyrophosphates.
• Other oxide supports may be used provided that they are inert to the desired catalytic reaction.
• the supports should be physically robust and pre-shaped.
• the term "pre-shaped" is used in this context to mean that the shape of the final catalyst is essentially the same as the starting support.
• the pre-shaped oxides typically can have average particle diameter sizes ranging from about 0.1 millimeter (mm) to about 20 mm. They can be in any common form such as extrudates, compressed pellets, or bulk solid that has been pulverized to the desired mesh size. They may also be in a variety of shapes such as rods, stars, cylinders, spheres, or broken chunks.
• the catalyst composition according to the present invention can be primarily amorphous in structure.
• an amorphous catalyst composition can have a small amount of crystalline structure caused, for example, by impurities.
• amorphous or “primarily amorphous” it is meant that the catalyst composition contains less than 10 weight percent crystalline material. The percent crystallinity is calculated based on the integrated intensities of an X-Ray diffraction from the individual diffraction patterns with peaks of crystallite size greater than 30A defined as crystalline and peaks of crystallite size less than or equal to 30A defined as amorphous.
• the catalyst composition according to the present invention can be prepared using the following general steps:
• the compound may be obtained directly from commercial sources or may be made by dissolving the titanium compound in water.
• concentration of the aqueous titanium solution can vary over a wide range.
• the solution can have a titanium compound concentration in the range of 25 to 75 wt%, or 30 to 70 wt%, or 50 to 60 wt%.
• the mode of adding the vanadium compound and the phosphorus compound to the aqueous titanium solution is not particularly limiting.
• the vanadium compound and the phosphorus compound may be blended together to form a physical mixture or a reaction product, before being added to the aqueous titanium solution.
• the V and P compounds may be added sequentially in any order or simultaneously to the aqueous titanium solution.
• the expression "adding a vanadium compound and a phosphorus compound" can refer to the addition of the vanadium compound and the phosphorus compound separately or collectively as a physical mixture or as a reaction product of the two.
• the heat-treating step and the water-removing step may be conducted sequentially or simultaneously.
• the heat-treating step can take place during the distillation or evaporation.
• the heat-treating step may be conducted over a wide temperature range, such as from above ambient up to 200 Q C or higher.
• the purpose of the heat-treating step is to facilitate mixing and/or reaction among the catalyst precursors.
• the heat-treating step may be carried out from several minutes to hours or days.
• the water-removal step may be accomplished in a number of ways. For example, as mentioned above, water may be removed by distillation or evaporation. Alternatively, as discussed in more detail below, the catalyst components can be precipitated out of solution by adding an anti-solvent to the mixture to precipitate out the catalyst components and separating the precipitate from the liquid to obtain the solid residue. The water can then be removed by decanting or filtration.
• the resulting solid residue may be crushed and sieved to obtain a desired particle size.
• the sieved catalyst particles can then be calcined in one or more stages in air prior to use.
• the calcining temperature is normally in the range of 200 Q C to 800 Q C.
• the calcining temperature ranges from 300 Q C to 500 Q C.
• the calcining step is typically carried out for 1 to 1 0 hours, and preferably for 2 to 8 hours.
• the mixed oxide catalyst according to the invention is formed.
• the catalyst precursors may be ammonium salts, halides, oxyacids, oxyacid salts, hydroxides, or oxides of vanadium, titanium, and phosphorus.
• the catalyst composition is prepared with the organo-titanium compound comprising titanium(IV) bis(ammonium
• the vanadium compound is preferably water soluble.
• examples of such compounds include vanadium trichloride, vanadium(IV) sulfate oxide hydrate, and ammonium vanadate optionally treated with aqueous oxalic acid and/or lactic acid.
• Other water-soluble vanadium sources can also be used.
• the phosphorus compound is also preferably water soluble.
• the compound should be converted to phosphorus oxides when calcined.
• Such phosphorus compounds include phosphoric acid, phosphorous acid, and ammonium salts of these acids.
• a reducing compound can be added to the reaction mixture to impart additional surface area to the resulting catalyst composition.
• Lactic acid is preferred for this purpose, but other compounds bearing bifunctional groups (i.e., bifunctional compounds) such as citric acid, glycolic acid, oxalic acid, ethylene glycol, butane diol, hexane diol, or pentane diol may also be used. Use of these surface area reagents is optional, but is generally preferred.
• the bifunctional compound can be added to the mixture of catalyst components before the heat-treating step (c).
• the bifunctional compound comprises lactic acid.
• a practical example of a method for preparing the catalyst composition according to the invention includes mixing a 50 wt% aqueous solution of TBALDH with a solution of ammonium metavanadate and phosphoric acid in water and, optionally, lactic acid; heating the mixture at 1 30 Q C under agitation ; removing water from the heat-treated mixture by distillation ; and calcining the resulting residue at 300°C and then at 450°C in air.
• the catalyst composition may be prepared as described above except that a water-miscible non-solubilizing solvent, or "anti-solvent,” is added to the reaction/heat-treating vessel to precipitate out the majority of the catalyst components after the heat-treating step.
• a water-miscible non-solubilizing solvent or "anti-solvent”
• the anti-solvent may be polar compounds such as alcohols, ketones, aldehydes, ethers, or esters. Alcohols such as ethanol are preferred as the anti-solvent.
• the catalyst composition of the invention can be supported on an oxide support.
• Suitable oxide supports include silica, alumina, titanium oxide, zirconium oxide, and titanium or zirconium pyrophosphates. Other oxide supports may be used provided that they are inert to the desired catalytic reaction.
• the supports should be physically robust and pre-shaped.
• the term "pre-shaped" is used in this context to mean that the shape of the final catalyst is essentially the same as the starting support.
• the pre-shaped oxides typically can have average particle diameter sizes ranging from about 0.1 millimeter (mm) to about 20 mm. They can be in any common form such as extrudates, compressed pellets, or bulk solid that has been pulverized to the desired mesh size.
• the titanium and the vanadium components can be loaded onto the support separately or together.
• a preferred technique is to dissolve the desired amount of ammonium vanadate and oxalic acid or lactic acid in the aqueous TBALDH solution. This solution can be diluted if desired and then used to impregnate the oxide support using the incipient wetness technique. The impregnated support is then dried at about 1 1 0 °C. The resulting material likely contains a homogeneous dispersion of the two metals since drying the solution at 1 10 °C produces a homogeneous glass. The dried support containing the vanadium and titanium is then impregnated with the desired amount of the aqueous solution of the phosphorus compound.
• the catalyst can be calcined, for example, at about 450 °C.
• the ternary V-Ti-P catalyst composition disclosed herein is primarily amorphous, as determined by x-ray diffraction analysis.
• the invention V-Ti-P catalyst composition prepared with TBALDH for example, produces acrylic acid in significantly higher yield (>20%) than the V-Ti-P material prepared with tetrachlorotitanium when a 55 weight percent aqueous formaldehyde feed is used, even though both catalysts are amorphous materials.
• This result suggests that the microstructure or the homogeneity of the invention catalyst is considerably different than that of the prior art catalyst.
• titanium chloride offers several advantages over using titanium chloride. For example, the formation of gaseous hydrochloric acid can be avoided; the discrete titanium(IV) precursor is a solute in water rather than a cumbersome heterogeneous gel; and the resulting V-Ti-P catalyst is formed with an inherently higher specific surface area.
• V-Ti-P materials prepared with TBALDH for example, in the absence of lactic acid are amorphous and are considerably more active and selective. Avoiding lactic acid addition is appealing, since it minimizes the amount of steps in the catalyst synthesis and results in less organic material that must be combusted during air calcination.
• the present invention provides a process for preparing a 2,3-unsaturated carboxylic acid, such as acrylic acid or methacrylic acid.
• carboxylic acid in this context includes the corresponding carboxylic acid ester, such as acrylate and methacrylate.
• the process of the invention comprises the step of contacting a formaldehyde source with a carboxylic acid in the presence of a condensation catalyst under vapor-phase condensation conditions to obtain the 2,3- unsaturated carboxylic acid.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the titanium component of the condensation catalyst is derived from a water-soluble, redox-active organo-titanium compound, as described herein.
• the 2,3-unsaturated carboxylic acid can be prepared with good yield, conversion, and selectivity.
• yield it is meant the (moles of product)/(moles of reactant fed)*1 00.
• the % yield of acrylic acid from formaldehyde is the (moles of acrylic acid)/(moles of formaldehyde fed)*100.
• conversion it is meant the (moles of reactant fed - moles of unreacted reactant)/(moles of reactant fed)*1 00.
• the % formaldehyde conversion is (moles of formaldehyde fed - moles of unreacted formaldehyde)/(moles of formaldehyde fed)*100.
• selectivity it is meant (moles of product)/(moles of reactant fed - moles of unreacted reactant)*100.
• % selectivity to acrylic acid from formaldehyde is (moles of acrylic acid)/(moles of formaldehyde fed - moles of unreacted
• Example B has an 80% formaldehyde conversion and Example C has a 60% formaldehyde conversion, the formaldehyde conversion of Example B is said to be 20% higher than Example C.
• comparisons are simply the mathematical difference in the percentages from one example to another.
• the formaldehyde source for use in the present invention is not particularly limiting. It can be anhydrous formaldehyde itself, 1 ,3,5-trioxane (sometimes referred to herein as simply "trioxane”), dimethoxymethane.
• the formaldehyde source may be an aqueous solution of formaldehyde.
• the aqueous formaldehyde solution can contain, for example, from 30 to 65 weight percent formaldehyde. Examples of such solutions include formalin (37 wt% formaldehyde) and industrial grade aqueous formaldehyde (55 wt% formaldehyde).
• the aqueous formaldehyde solution may be obtained commercially, by oxidation of methanol, or by blending water with trioxane, for example, in a molar ratio of approximately 4:1 .
• the carboxylic acid should have at least 2 hydrogen atoms in the position alpha to the carboxylic acid group.
• the carboxylic acid is preferably an aliphatic carboxylic acid having 2 to 4 carbon atoms. Acetic and propionic acids are preferred carboxylic acids. The most preferred carboxylic acid is acetic acid.
• carboxylic acid in this context includes the
• carboxylic acid ester when formation of the 2,3-unsaturated carboxylic acid ester is desired.
• carboxylic acid esters include acetate and propionate.
• the molar ratio of the formaldehyde component to the carboxylic acid component may be from 0.1 to 10, preferably from 0.2 to 5, and more preferably from 0.2 to 2.
• the molar ratio of water to the formaldehyde component may be from 0 to 5, preferably from 0 to 3, and more preferably from 0 to 1 .5.
• the process can be operated at a temperature from 200 °C to 400 °C, preferably from 225 °C to 375 °C, and more preferably from 275 °C to 375 °C.
• the process can be run at a pressure from 0.1 to 1 0 bars absolute (bara), preferably from 0.5 to 5 bara, and more preferably from 1 to 1 .5 bara.
• the liquid feed rate can range from 1 .0 to 1000 mL/kg catalyst/minute, and preferably from 1 0 to 1 00 mL/kg catalyst/minute.
• the reactants can be fed to the condensation reactor with oxygen along with an inert carrier gas such as nitrogen or oxygen-depleted air. Gases recycled from the process can be used.
• the inert gas component can be present at
• concentrations ranging from 0 to 90 mole % of the total feed, preferably from 25 to 85 mole %, and more preferably from 30 to 80 mole %.
• concentration of the oxygen component can range from 0.5 to 6 mole %, preferably from 2 to 5 mole %, and more preferably from 3 to 4 mole %. Low levels of oxygen allow for coke to build up on the catalyst. On the other hand, high levels of oxygen can lead to excessive combustion of reactants and products.
• the space velocity should preferably range from 50 to 400 moles of feed/(kg catalyst-hr), more preferably from 1 00 to 300 moles of feed/(kg catalyst-hr), and most preferably from 1 25 and 200 moles of feed/(kg catalyst-hr).
• moles of feed is meant to be inclusive of all of the species being fed to the catalyst including organics, water, oxygen, and inerts.
• Inhibitors such as hydroquinone may be added to the 2,3- unsaturated carboxylic acid product to minimize polymerization.
• the present invention provides a process for preparing a 2,3-unsaturated carboxylic acid.
• the process comprises the steps of contacting a methylene dialkanoate and a diluent gas with a condensation catalyst under vapor-phase condensation conditions to obtain the 2,3-unsaturated carboxylic acid.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• V vanadium
• Ti titanium
• P phosphorus
• R is selected from the group consisting of hydrogen and an alkyl group having 1 to 8 carbon atoms.
• methylene dialkanoate it is meant that a -CH 2 -, methylene group, is bonded to two alkanoate, carboxylate, groups.
• the alkanoate group should have at least 2 hydrogen atoms bonded to a carbon atom in the position alpha to the carboxylate carbon. Acetate and propionate are preferred alkanoates.
• diatomuent gas it is meant a gas which is introduced so that this gas quantitatively lowers the concentration of the reactants in feed.
• the composition of the "diluent gas” can be an inert carrier gas and/or oxygen ; some examples of an inert gas include nitrogen, argon, oxygen depleted air, or air.
• condensation catalyst it is meant a homogeneous or heterogeneous catalyst that can combine reactant molecules with the concomitant elimination of water or other by-product molecules.
• an alkyl group with 1 to 8 carbon atoms it is meant any saturated hydrocarbon with 1 up to and including 8 carbons atoms.
• alkyl groups include methyl, ethyl, propyl, iso-propyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, and octyl.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• V vanadium
• Ti titanium
• P phosphorus
• These catalysts can be made by methods well known to one skilled in the art.
• the VTi a P b O c , catalyst can be the inventive catalyst wherein the titanium component is derived from a water- soluble, redox-active organo-titanium compound.
• water-soluble, redox-active organo-titanium compounds useful in the VTi a P b O c catalyst include titanium lactates, titanium alkanolamines, and titanium
• acetylacetonates Such compounds are commercially available, such as from Dorf Ketal under the trade name TYZOR®. Practical examples of such compounds include titanium(IV) bis(ammonium lactate)di hydroxide
• the organo-titanium compound comprises titanium(IV) bis(ammonium lactate)di hydroxide.
• the molar ratio of water to the methylene dialkanoate component may be between about 0 and 5, preferably between 0 and 1 , and most preferably at 0.
• the process for preparing 2,3-unsaturated carboxylic acids can be operated at a temperature between about 1 50°C and 400°C, preferably between 200 °C and 375 °C and most preferably between 220 °C and 320 °C.
• the process is normally operated at a pressure between about 0.1 and 10 bars absolute (bara), preferably between 0.5 and 5 bara and most preferably between about 1 and 1 .5 bara.
• the process for preparing 2,3-unsaturated carboxylic acids can be performed when the methylene dialkanoate is methylene dipropionate. This process can also be performed when the methylene dialkanoate is methylene diacetate. Experiments performed with methylene diacetate or methylene dipropionate produced no detectable paraformaldehyde in the process's reaction product and produced higher space time yields than conventional feeds.
• the methylene dialkanoate is contacted with the condensation catalyst in the presence of a diluent gas.
• This diluent gas can be an inert carrier gas and/or oxygen. Gases recycled from the process can be used.
• the diluent gas component can be present at concentrations between 1 and 90 mole percent based on the total moles of the methylene dialkanoate and diluent gas, preferably between about 25 and 75 mole percent, and most preferably between about 30 and 65 mole percent.
• the oxygen concentration can be between about 0.5 to 20 mole % based on the total moles of diluent gas, preferably between 2 and 1 0 mole %, and most preferably between about 4 and 6 mole %. Low levels of oxygen allow for coke to build up on the catalyst. High levels of oxygen can lead to excessive combustion of reactants and products.
• the space time yield is preferably between about .1 and 200 moles of 2,3 unsaturated carboxylic acid/(kg catalyst-hr), more preferably between about 1 and 50 moles of 2,3 unsaturated carboxylic acid /(kg catalyst-hr) and most preferably between about 2 and 10 moles of 2,3 unsaturated carboxylic acid /(kg catalyst-hr).
• the catalyst may be regenerated between reaction runs in air at 400 °C.
• the present invention provides a process for preparing a 2,3-unsaturated carboxylic acid.
• the process comprises the step of contacting a methylene dialkanoate and diluent gas with a condensation catalyst under vapor-phase condensation conditions to obtain the 2,3- unsaturated carboxylic acid.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the titanium component is derived from a water-soluble, redox-active organo-titanium compound.
• the methylene dialkanoate has the general formula (I):
• R is selected from the group consisting of hydrogen, methyl, ethyl, propyl, and isopropyl.
• compounds useful in the VTi a P b O c catalyst include titanium lactates, titanium alkanolamines, and titanium acetyl aceto nates. Such compounds are commercially available, such as from Dorf Ketal under the trade name
• the organo-titanium compound comprises titanium(IV) bis(ammonium lactate)di hydroxide (TBALDH), titanium diethanolamine, titanium triethanolamine, and titanium acetylacetonate.
• the organo-titanium compound comprises titanium(IV) bis(ammonium
• the molar ratio of water to the methylene dialkanoate component may be between about 0 and 5, preferably between 0 and 1 , and most preferably at 0.
• the process for preparing 2,3-unsaturated carboxylic acids can be operated at a temperature between about 1 50°C and 400°C, preferably between 200 °C and 375 °C and most preferably between 220 °C and 320 °C.
• the process is normally operated at a pressure between about 0.1 and 10 bars absolute (bara), preferably between 0.5 and 5 bara and most preferably between about 1 and 1 .5 bara.
• the process for preparing 2,3-unsaturated carboxylic acids can be performed when the methylene dialkanoate is methylene dipropionate. This process can also be performed when the methylene dialkanoate is methylene diacetate. Experiments performed with methylene diacetate or methylene dipropionate produced no detectable paraformaldehyde in the process's reaction product and produced higher space time yields than comparable conventional feeds.
• the methylene dialkanoate is fed with a diluent gas to achieve contact with the condensation catalyst.
• This diluent gas can be an inert carrier gas and/or oxygen. Gases recycled from the process can be used.
• the diluent gas component can be present at concentrations between 1 and 90 mole percent based on the total moles of the methylene dialkanoate and diluent gas, preferably between about 25 and 75 mole percent, and most preferably between about 30 and 65 mole percent.
• the oxygen concentration can be between about 0.5 to 20 mole % based on the total moles of diluent gas, preferably between 2 and 1 0 mole %, and most preferably between about 4 and 6 mole %. Low levels of oxygen allow for coke to build up on the catalyst. High levels of oxygen can lead to excessive combustion of reactants and products.
• the space time yield should preferably range between about .1 and 200 moles of 2,3 unsaturated carboxylic acid/(kg catalyst-hr), more preferably between about 1 and 50 moles of 2,3 unsaturated carboxylic acid /(kg catalyst-hr) and most preferably between about 2 and 1 0 moles of 2,3 unsaturated carboxylic acid /(kg catalyst-hr).
• the catalyst may be regenerated between reaction runs in air at 400 °C.
• Embodiment A is a catalyst composition comprising a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P), wherein the titanium component is derived from a water-soluble, redox-active organo-titanium compound.
• Embodiment A which has the general formula VTi a P b O c , wherein a is a number from 0.3 to 6.0, b is a number from 2.0 to 1 3.0, and c is the number of atoms required to satisfy the valences of V, Ti, and P; or wherein a ranges from 1 .0 to 4.0 and b ranges from 4.0 to 10.0.
• compound comprises titanium(IV) bis(ammonium lactate)dihydroxide.
• the catalyst composition of Embodiment A or Embodiment A with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support comprises silica, alumina, titanium oxide, titanium pyrophosphate, zirconium oxide, or zirconium pyrophosphate.
• the catalyst composition of Embodiment A or Embodiment A with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support has a particle size ranging from 0.1 mm to 20 mm.
• Embodiment B is a method for preparing a catalyst composition comprising a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P). The method comprises the steps of:
• Embodiment B wherein the water removing step (d) comprises distillation or evaporation.
• Embodiment B wherein the water removing step (d) comprises adding an anti-solvent to the mixture to precipitate out the catalyst components and separating the precipitate from the liquid to obtain the solid residue.
• Embodiment B wherein the water removing step (d) comprises adding an anti-solvent to the mixture to precipitate out the catalyst components and separating the precipitate from the liquid to obtain the solid residue, and wherein the precipitate is separated from the liquid by filtration.
• Embodiment B wherein the water removing step (d) comprises adding an anti-solvent to the mixture to precipitate out the catalyst components and separating the precipitate from the liquid to obtain the solid residue, wherein the precipitate is separated from the liquid by filtration, and wherein the anti-solvent is a polar compound selected from alcohols, ketones, aldehydes, ethers, and esters; or wherein the anti-solvent is an alcohol.
• the anti-solvent is a polar compound selected from alcohols, ketones, aldehydes, ethers, and esters; or wherein the anti-solvent is an alcohol.
• Embodiment B or Embodiment B with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support has a particle size ranging from 0.1 mm to 20 mm.
• Embodiment B or Embodiment B with one or more of the intervening features which further comprises adding a bifunctional compound to the mixture of catalyst components before the heat-treating step (c), wherein the bifunctional compound comprises citric acid, lactic acid, glycolic acid, oxalic acid, ethylene glycol, butane diol, pentane diol, or hexane diol ; or wherein the bifunctional compound comprises lactic acid.
• Embodiment C is a process for preparing a 2,3-unsaturated carboxylic acid. The process comprises the step of contacting a
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the titanium component of the condensation catalyst is derived from a water-soluble, redox-active organo-titanium compound.
• Embodiment C or Embodiment C with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support comprises silica, alumina, titanium oxide, titanium pyrophosphate, zirconium oxide, or zirconium pyrophosphate.
• Embodiment C or Embodiment C with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support has a particle size ranging from 0.1 mm to 20 mm.
• Embodiment C or Embodiment C with one or more of the intervening features wherein the condensation conditions comprise a total feed space velocity of 50 to 400 moles of feed / (kg catalyst ⁇ hr) ; or the total feed space velocity ranges from 1 00 to 300 moles of feed / (kg catalyst ⁇ hr); or the total feed space velocity ranges from 1 25 to 200 moles of feed / (kg catalyst ⁇ hr).
• Embodiment D is a process for preparing a 2,3-unsaturated carboxylic acid.
• the process comprises the step of contacting a methylene dialkanoate and a diluent gas with a condensation catalyst under vapor-phase condensation conditions to obtain the 2,3-unsaturated carboxylic acid.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the methylene dialkanoate has the general formula (I):
• R is selected from the group consisting of hydrogen and an alkyl group having 1 to 8 carbons.
• Embodiment D wherein the condensation catalyst has the formula VTi a P b O c , wherein a is a number from 0.3 to 6.0, b is a number from 2.0 to 1 3.0, and c is the number of atoms required to satisfy the valences of the components other than oxygen.
• Embodiment D or Embodiment D with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support comprises silica, alumina, titanium oxide, titanium pyrophosphate, zirconium oxide, or zirconium pyrophosphate.
• Embodiment D or Embodiment D with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support has a particle size ranging from 0.1 mm to 20 mm.
• Embodiment E is a process for preparing a 2,3-unsaturated carboxylic acid.
• the process comprises the step of contacting a methylene dialkanoate and a diluent gas with a condensation catalyst under vapor-phase condensation conditions to obtain the 2,3-unsaturated carboxylic acid.
• the condensation catalyst comprises a mixed oxide of vanadium (V), titanium (Ti), and phosphorus (P).
• the titanium component is derived from a water-soluble, redox-active organo-titanium compound.
• the methylene dialkanoate has the general formula (I) :
• R is selected from the group consisting of hydrogen, methyl, ethyl, propyl, and isopropyl.
• Embodiment E or Embodiment E with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support comprises silica, alumina, titanium oxide, titanium pyrophosphate, zirconium oxide, or zirconium pyrophosphate.
• Embodiment E or Embodiment E with one or more of the intervening features which further comprises a pre-shaped support, wherein the pre-shaped support has a particle size ranging from 0.1 mm to 20 mm.
• D/L-Lactic acid 90 wt%), ammonium metavanadate (99+ wt% NH 4 V0 3 ), phosphoric acid (85 wt% H 3 P0 4 ), titanium(IV) bis(ammonium lactate)di hydroxide (50 wt% solution in water), tetrachlorotitanium (>99 wt% TiCI 4 ), and titanium dioxide colloidal suspension in water (23.38 wt% Ti0 2 ) were purchased from commercial suppliers and used as received.
• XRD Powder X-ray Diffraction
• XRF X-ray Fluorescence Spectroscopy
• TPD Temperature Programmed Desorption
• SCCM Standard cubic centimeters per minute
• MeOAc methyl acetate
• MeOH methanol
• MA methyl acrylate
• H2CO formaldehyde
• HOAc acetic acid
• HOPr propionic acid
• mmol millimoles
• prod product
• AA acrylic acid
• BSTFA N,0-bis(trimethylsilyl)trifluoroacetamide
• TMSCI trimethylsilyl chloride.
• Crystallite size was calculated based on the measurement of the full width half maximum for peaks in the diffraction pattern and use of the Scherrer equation (P.N. Scherrer, Ges. Wiss. Gottingen, Math.- Phys. Kl. 2, 96-100 (1918)). Quantitative phase analysis was calculated using a refinement algorithm base on the Rietveld method (H.M. Rietveld, J. Applied Crystallography 21 , 86-91 (1988)). Percent crystallinity was calculated based on integrated intensities from the individual diffraction patterns with peaks of crystallite size greater than 30A defined as crystalline and peaks of crystallite size less than or equal to 30A defined as amorphous (N.S. Murthy et al., Polymers 31 , 996-1002 (1990)).
• TPD determinations were conducted using a Mass Spectrometer attached to the outlet of a Micrometrics Autochem II 2920 analyzer.
• the determination of total acidity and total basicity using isopropanol as the probe molecule is performed as follows. Approximately 0.05 grams of sample is weighed into a quartz U tube which is placed in a ceramic furnace. The sample is subjected to a programmed temperature cycle that consists of a heat cycle to 450 Q C under 10% oxygen in Helium, a cooling step to 40 Q C. Isopropanol is dosed on the sample using the vapor generator of the
• the vapor generator operates by bubbling helium through a flask containing isopropanol at room temperature. The resulting "vapor-saturated" helium is transferred through a heated sample loop and injected over the sample. After saturating the surface of the sample, dry helium is passed over the sample to remove any physisorbed vapor. Then a final heating to ⁇ 450 Q C at 20 Q C /min in a flowing stream of He at which time mass spectral data is collected from the gas flowing through the sample.
• Liquid product samples were collected over a measured time period, weighed, and analyzed by gas chromatography. Samples were weighed into a gas chromatography (GC) vial to a recorded weight of 0.1 XXX (where X is the actual number shown on the balance). Then, a LEAP unit was used to robotically add 200 ⁇ . of internal standard (0.7325g dodecane in 1 0OmL pyridine), followed by 1 .OmL of BSTFA (w/ TMSCI). The vials were then placed on a heat plate at 80 °C for 30 minutes.
• GC gas chromatography
• each sample was injected on two columns running in parallel on one instrument, a Shimadzu 201 0 gas chromatograph with an AOC-20 autosampler. Gas Chromatography measurements were used to quantify all components in the liquid product except formaldehyde.
• the quartz reactor had indentations 20 cm (8 inches) up from the base of the tube. The region of the reactor with the indentations was situated near the base of the heated section of the furnace. The reactor was also fitted with a thermowell that extended from the top of the reactor to about an inch below the indentations. The reactor was first loaded with quartz chips to about 2.5 inches in height above the indentations to allow the catalyst to be positioned in the middle of the furnace. The reactor was then loaded with a 5.0 g charge of catalyst. The thermocouple in the thermowell was placed near the center of the catalyst bed. Sufficient quartz chips (about 2.5 inches) were added to the region above the catalyst charge to reach the top of the heated region of the furnace. The performance of this catalyst is summarized in Table 3.
• the TBALDH compound is a suitable precursor for the synthesis of a catalytically active V-Ti-P material, providing acrylic acid in good yield and in high purity under standard screening conditions.
• the molar composition of the catalyst was nearly identical to that of the catalyst used in Comparative Example 1 below, however the catalyst in Comparative Example 1 has only 60 % of the surface area compared to the catalyst of Example 1 .
• the total acid sites were higher for the catalyst of Example 1 as compared to the catalyst of Comparative Example 1 ; 92.5 ( ⁇ /g) compared to 64.2 ( ⁇ /g), respectively.
• Powder x-ray diffraction analysis of the catalyst reveals that it is primarily amorphous ( Figure 1 ).
• the catalyst in this example was prepared according to the methods described in M. Ai, Applied Catalysis, Vol. 48, pp. 51 -61 (1 989) and JP 1 989-068335A.
• a 5-L three-necked round bottomed flask was charged with 300 ml_ of water ice and 300 ml_ of deionized water.
• the flask was fitted with a 1 25- ml_ addition funnel and vented to an aqueous saturated sodium bicarbonate solution.
• Tetrachlorotitanium (34.6 g) was then added slowly to the vigorously stirred water/ice mix.
• the reactor atmosphere was flushed into the scrubber solution with an air flow to remove gaseous HCI.
• the pH of the resulting colorless solution was between 0 and 1 .
• a V/P solution was prepared following the procedure of Example 1 , step 1 .
• the hydroxide gel from step 1 above was suspended in 200 ml_ of water in a 1 -L three-necked kettle reactor equipped with a condenser and mechanically stirred at 700 to 800 rpm long enough to obtain a homogeneous white suspension.
• the V/P solution from step 2 above was slowly poured into the gel suspension to give a blue suspension.
• the V/P flask was rinsed with 50 mL of water and the contents were added to the reaction flask. The mixture was then stirred at 700 to 800 rpm at 1 30°C for 1 6 hours to give a blue to blue-green suspension.
• the quartz reactor had indentations 30.5 cm (1 2 inches) up from the base of the tube.
• the region of the reactor with the indentations was situated near the base of the heated section of the furnace.
• the reactor was also fitted with a thermowell that extended from the top of the reactor to about an inch below the indentations.
• the reactor was first loaded with quartz chips to about 10 inches in height above the indentations to allow the catalyst to be positioned in the middle of the 3-element furnace.
• the reactor was then loaded with a 5.0 g charge of catalyst.
• the thermocouple in the thermowell was placed 1 .5 inches up from the base of the catalyst bed. Sufficient quartz chips were added to the region above the catalyst charge to reach the top of the heated region of the 3-element furnace.
• Table 3 The performance of the catalyst is summarized in Table 3.
• a V/P solution was prepared following the procedure of Example 1 , step 1 .
• the catalyst in this example was prepared according to the procedure described in J.K. Bartley et al., "Vanadium Phosphate Catalysts,"
• a 1 -L kettle reactor equipped with a mechanical stirrer, a condenser, and an addition funnel was charged with 100.08 g of vanadium pentoxide and 600 mL of isobutyl alcohol all under a nitrogen atmosphere.
• the contents were heated at reflux (oil bath set at 130°C) for 1 hour, then 139.44 g of 85% phosphoric acid was added slowly, and the reaction temperature was maintained at reflux for 22 hours.
• the resulting sky blue suspension contained small amounts of dark insoluble materials.
• Another 5.53 g of 85% phosphoric acid was then added along with an additional 150 mL of iso-butanol. The reflux was then continued for another seven hours.
• the blue suspension Upon cooling to room temperature, the blue suspension was poured on to a Buchner funnel with filter paper; the heavier insoluble impurities remained in the reaction flask. The blue solid was then isolated by vacuum filtration and washed with 200 mL of ethanol and dried at room temperature while pulling a vacuum. Water soluble impurities were removed by heating a suspension of the blue solid in water to reflux overnight under a nitrogen atmosphere. The mixture was then filtered while still hot, leaving a blue solid on the filter paper and a yellow filtrate in the filter flask. The blue solid was then dried at 1 10°C for 22 hours in air to give a blue-green cake. This material was then crushed and sieved through an 8x14 mesh.
• the catalyst in this example was prepared according to the procedure described in M. Abon et al., J. Catalysis, Vol. 156, pp. 28-36 (1995).
• the catalyst was prepared according to the procedure described in C D. Rodica et al., RO 1 14 084 B1 (1 999), except that graphite was not added to the catalyst.
• Vanadium(V) oxide (3.9 g) was mixed with titanium dioxide (6.65 g), molybdenum(VI) oxide (0.45 g), and 85% phosphoric acid (1 7 ml_) in a ceramic dish to give a thick paste. This material was then dried at 200°C in a muffle furnace in air for 3 hours to give a hard yellow solid. The solid was then crushed and sieved through an 8x14 mesh. The meshed particles were calcined in a muffle furnace in air at 300°C for 2 hours. XRD analysis ( Figure 6) of this material showed it to be crystalline titanium dioxide; vanadium and phosphorus components were not observed.
• Table 1 The surface properties and bulk composition of the catalyst prepared in this example are summarized in Table 1 .
• the catalyst in this example was first prepared by suspending ammonium metavanadate (19.54 g) in 218.41 g of a 50 wt% titanium(IV) bis(ammonium lactate)di hydroxide solution followed by addition of 200 ml_ of deionized water in a 1 -L three-neck kettle reactor equipped with a distillation head and a mechanical stirrer. The beige suspension was stirred at 700 rpm for 1 0 min at room temperature then 1 05.57 g of 85% phosphoric acid was added followed by a rinse with about 50 ml_ of water. There was an immediate color change to bright yellow and thickening of the mixture, then a change to green then pale green over 20 min.
• Example 1 except that a liquid feed composed of molar ratio 1 2 acetic acid/1 trioxane/4.09 water was used at 325 °C, 0.089 ml_ liquid feed/minute and the carrier gas, nitrogen, was set at 70 SCCM.
• the performance of the catalyst is summarized in Table 5.
• the resulting catalyst was amorphous by XRD and has a surface area very similar to the catalyst described in Example 1 and bulk composition very similar to those of the catalysts described in Example 1 and Comparative Example 1 .
• the catalyst in this example was prepared according to the procedure described in Comparative Example 1 , except that lactic acid was excluded from the procedure.
• XRD analysis ( Figure 8) of this material showed it to be a mixture of crystalline vanadium(l ll) catena-phosphate and titanium diphosphate.
• Table 1 The surface properties and bulk composition of the catalyst prepared in this example are summarized in Table 1 .
• the vapor- phase condensation reaction was carried out as described in Example 1 .
• the performance of the catalyst is summarized in performance Table 5.
• V-Ti-P material having low acidity and surface area is obtained when tetrachlorotitanium was used as the titanium precursor and lactic acid was excluded during the catalyst synthesis.
• the surface of the resulting solid was a mixture of crystalline compounds, which evidently displayed poor catalytic activity toward acrylic acid synthesis.
• the yield was less than 1 0%, and the selectivity less than 1 2%.
• This example also highlights the fact that TBALDH is a more attractive V-Ti-P precursor, since the lactate groups inherent in the salt are sufficient to reduce vanadium during catalyst synthesis, which assists in forming an amorphous surface and creating increased surface area upon calcination.
• V-Ti-P Catalyst (Method A at 2X Scale) Lifetime Study with an Anhydrous Liquid Feed
• the catalyst in this example was prepared via Method A (Example 1 ), but at twice the scale.
• the condensation reaction of acetic acid and trioxane (the formaldehyde source) in this example was performed as described in Example 1 , except that a liquid feed composed of molar ratio 1 2 acetic acid/1 trioxane was used at 325 °C, 0.083 mL liquid feed/minute, and the carrier gases were nitrogen (49 SCCM) and air (21 SCCM).
• the reaction was run for twenty-seven hours.
• Heat to the reactor was provided by an Applied Test Systems series 321 0 three- element electric furnace having a heated zone 50 cm (1 9.5 inches) in length. Liquid products were collected in a three-necked flask fitted with a glycol chilled (0°C) jacket. The third neck of the flask was connected to a water- cooled condenser, which was connected to a dry ice trap. The base of the receiver flask was fitted with a stopcock to allow for draining of the liquid products.
• the quartz reactor had indentations 13 cm (5 inches) up from the base of the tube.
• the region of the reactor with the indentations was situated near the base of the heated section of the furnace.
• the reactor was also fitted with a thermowell that extended from the top of the reactor to about an inch below the indentations.
• the reactor was first loaded with quartz chips to about 8 inches in height above the indentations to allow the catalyst to be positioned in the middle of the 3-element furnace.
• the reactor was then loaded with a 5.0 g charge of catalyst.
• the thermocouple in the thermowell was placed 1 .5 inches up from the base of the catalyst bed. Sufficient quartz chips were added to the region above the catalyst charge to reach the top of the heated region of the 3-element furnace.
• V-Ti-P catalyst prepared with TBALDH afforded acrylic acid in moderate yield and selectivity over a twenty-seven hour period.
• the presence of oxygen contributed to an extended catalyst lifetime.
• high coking rates are suspected to have caused the decreased yield observed in the last data point.
• V-Ti-P Catalyst (Method B at 2X Scale) Lifetime Study with an Anhydrous Liquid Feed
• V-Ti-P Catalyst (Method A at 2X Scale) Lifetime Studv with an Aqueous Liquid Feed
• the catalyst used in this example was the same catalyst charge used in Example 3, except that it was regenerated after that example by heating at 400°C under 6 vol% oxygen (94 vol% nitrogen) for 16 hours. The vapor-phase condensation reaction was then carried out according to
• Example 3 except that a liquid feed composed of molar ratio 1 2 acetic acid/1 trioxane/4.09 water was used at 325 °C, 0.089 mL liquid feed/minute.
• the carrier gases were nitrogen (49 SCCM) and air (21 SCCM). The reaction was run for twenty-seven hours.
• the performance of the catalyst is summarized in Table 8.
• V-Ti-P catalyst prepared with TBALDH maintained (1 ) a very high selectivity toward acrylic acid when an aqueous liquid feed was used and (2) a consistent moderate yield.
• the final yield of nearly 55% is comparatively higher than the same point in Example 3, presumably due to a lower rate of coking.
• V-Ti-P Catalyst (Method B at 2X Scale) Lifetime Studv with an Aqueous Liquid Feed
• the catalyst used in this example was the same catalyst charge used in Comparative Example 7, except that it was regenerated after that example by heating at 400°C under 6 vol% oxygen (94 vol% nitrogen) for 1 6 hours.
• the vapor-phase condensation reaction was then carried out according to Example 3, except that a liquid feed composed of molar ratio 1 2 acetic acid/1 trioxane/4.09 water was used at 325 °C, 0.089 mL liquid feed/minute.
• the carrier gases were nitrogen (49 SCCM) and air (21 SCCM). The reaction was run for twenty-seven hours.
• the performance of the catalyst is summarized in Table 9.
• V-Ti-P catalyst prepared according to the prior art did not afford acrylic acid in as high a yield as the invention catalyst when an aqueous liquid feed was used. Even though the selectivity toward acrylic acid was similarly high and the reaction lifetime was comparable, the formaldehyde conversion was consistently lower than observed in Example 4 by more than twenty percent. This is surprising given that both V-Ti-P catalysts demonstrated similar activity and selectivity when the anhydrous liquid feed was used.
• the catalyst used in this example was prepared by first suspending ammonium metavanadate (19.65 g) in 218.54 g of a 50 wt% titanium(IV) bis(ammonium lactate)di hydroxide solution followed by addition of 1 50 ml_ of deionized water in a 1 -L three-neck kettle reactor equipped with a reflux condenser and a mechanical stirrer. The beige suspension was stirred at 700 rpm for 1 0 min at room temperature. Then 1 05.06 g of 85% phosphoric acid were added slowly followed by a rinse with 50 ml_ of deionized water. There was an immediate color change to bright yellow, then a change to green then pale green over 20 min.
• the suspension was then heated to reflux for one hour, after which no further color change was observed.
• the reactor was cooled to about 6°C in an ice-water bath, and 700 to 800 ml_ of absolute ethanol was added, causing the mixture to thicken.
• the contents were stirred for 20 min at 6°C and the solids were collected on a medium porosity frit while pulling a vacuum.
• the emerald green filtrate (405.28 g) was collected and subjected to elemental analysis. [000199]
• the filtered solid was allowed to air dry while pulling a vacuum on the frit to give a pale green powder.
• the powder was calcined initially by heating at 300 °C for 1 6 h in a muffle furnace in air to give grey-green solids.
• the solids were then sieved through an 8x14 mesh.
• the 8x14 meshed pellets were then calcined at 450 °C in a quartz tube furnace for 6 h with a 60 SCCM air flow to give pale green irregularly shaped pellets.
• the catalyst maintained a formaldehyde conversion of around 78% after 27 hours and a product selectivity of approximately 80% after the same time period. Only 7 wt% of the vanadium components and 15.5 wt% of the phosphorus
• the catalyst used in this example was prepared by first suspending ammonium metavanadate (19.52 g) in 218.34 g of a 50 wt% titanium(IV) bis(ammonium lactate)di hydroxide solution followed by addition of 1 50 mL of deionized water in a 1 -L three-neck kettle reactor equipped with a reflux condenser and a mechanical stirrer. The beige suspension was stirred at 700 rpm for 1 0 min at room temperature. Then 1 05.32 g of 85% phosphoric acid were added slowly followed by a rinse with 50 ml_ of deionized water. There was an immediate color change to bright yellow, then a change to green then pale green over 20 min.
• the suspension was then heated to reflux for one hour, after which no further color change was observed.
• the reactor was cooled to about 6°C in an ice-water bath and 800 ml_ of deionized water were added. The contents were stirred for 20 min at 6°C and the solids were collected on a medium porosity frit while pulling a vacuum. The deep blue filtrate (459.9 g) was collected and subjected to elemental analysis.
• the filtered solid was allowed to air dry while pulling a vacuum on the frit to give a pale green powder that was calcined initially by heating at 300 °C for 1 6 h in a muffle furnace in air to give grey-green solids.
• the solids were then sieved through an 8x14 mesh.
• the 8x14 meshed pellets were then calcined at 450 °C in a quartz tube furnace for 6 h with a 60 SCCM air flow to give yellow irregularly shaped pellets.
• Example 1 Comp.
• Example 1 Comp.
• Example 2
• the catalyst used in these examples was a 5.0 g charge obtained from the invention catalyst batch described in Example 3.
• the vapor phase condensation reactions were carried out as described in Example 3.
• the space velocities were varied in Examples 7 and 8, but the molar ratios of the feed components remained constant.
• the high space velocity conditions of the invention produced less acetic acid destruction, higher space time yields, higher yields of acrylates from formaldehyde equivalents fed and a higher selectivity to acrylates from the formaldehyde reacted.
• This example illustrates that the preferred conditions of the invention allow for high selectivity and activity to be maintained over an extended period of time without the need for catalyst regeneration.
• the reactor set up for this example was similar to that of Examples 7-9, except for two differences. A different furnace was used, and the walls of this furnace were about 1 .5 inches (3.8 cm) from the reactor. This configuration resulted in lower catalyst bed temperatures than in the previous examples. The furnace was set at 320 °C, and the catalyst bed temperatures during the reaction ranged between about 327 and 332 °C. The second difference is that the receiver was kept at ambient temperature instead of 0 °C. The
• Examples 1 1 through 25 below exemplify the preparation of the supported catalysts of the invention.
• Examples 26 through 37 demonstrate the utility of the supported catalysts of the invention in the preparation of acrylic acid from acetic acid and a formaldehyde source.
• a solution was prepared from ammonium vanadate (0.97 g, 8.29 mmole), water (1 0 mL), and oxalic acid (2.09 g, 1 6.58 mmole).
• the ammonium vanadate dissolved without heating with the evolution of gas to form a blue solution.
• the soluble Ti source used in this example was titanium(IV) bis(ammonium lactate)di hydroxide, 50 wt% in water (TBALDH), certified to contain 1 3.4 wt% Ti0 2 . 9.886 g (0.0166 mole Ti) of the TBALDH solution were added to the aqueous V/oxalic acid solution. The solution remained clear blue with no precipitate.
• Example 1 1 behaved when dried and how the dried mass reacted with aqueous H 3 P0 4 . 1 .560 g of the solution of Example 1 1 was placed in an evaporating dish and heated on the steam bath. This produced a dark blue-green glass (0.440 g). This glass was treated with a solution prepared from 0.401 g 85% H 3 P0 4 (calculated amount 0.379 g) diluted to 1 .3 mL with water. At first, about 20% of the glass dissolved to form a clear green solution, but then the whole system set up as a thick light-green paste.
• a Ti0 2 supported catalyst precursor was prepared using a portion of the solution from Example 1 1 (4.08 g) and Ti0 2 1 /1 6-inch extrudates (5.0 g, Alfa Aesar lot # K21 S005). These conditions were about incipient wetness.
• the white Ti0 2 turned gray upon impregnation.
• the impregnated Ti0 2 was dried on the steam bath with occasional stirring.
• the steam bath-dried material was light gray. This material was dried in the muffle furnace overnight at 1 1 0 °C. The material was light gray-tan upon removal from the muffle furnace.
• the amount of solution required was calculated from the measured density of solution of Example 1 1 (1 .1 5 g/mL) that was used to prepare the original catalyst precursor such that the volume of the aqueous phosphoric acid solution was the same as that of the solution of Example 1 1 originally used.
• a solution was prepared from 0.996 g 85% H 3 P0 4 (calculated amount 0.992 g) diluted to 3.5 ml_ with water and used to impregnate the material recovered from the muffle furnace. The resulting impregnated material was very light green.
• the phosphoric acid impregnated sample appeared to be at incipient wetness and was stirred with a Teflon spatula in its evaporating dish on the steam bath until free flowing. The color remained green, but became a lighter shade as the water evaporated.
• the sample in its evaporating dish was placed in the muffle furnace and heated to 1 10 °C for 2 hours then heated to 450 °C for 6 hours.
• the resulting catalyst (5.91 2 g) was yellow.
• a Si0 2 supported catalyst precursor was prepared using a portion of the solution from Example 1 1 (6.82 g) and 8 mesh Davison grade 57 Si0 2 (5.0 g, lot 557). These conditions were about incipient wetness.
• the wet impregnated Si0 2 was dark blue. This material was dried on the steam bath with occasional stirring. The steam bath-dried material was light blue. This material was dried in the muffle furnace over night at 1 1 0 °C. The material was dark blue upon removal from the muffle furnace.
• the amount of solution required was calculated from the measured density of solution of Example 1 1 (1 .1 5 g/mL) that was used to prepare the original catalyst precursor such that the volume of the aqueous phosphoric acid solution was the same as that of the solution of Example 1 1 originally used.
• a solution was prepared from 1 .654 g 85% H 3 P0 4 (calculated amount 1 .658 g) diluted to 5.9 mL with water and used to impregnate the material recovered from the muffle furnace. The resulting impregnated material was very dark green.
• An alumina supported catalyst precursor was prepared using a portion of the solution from Example 1 1 (7.24 g) and high surface area aluminum oxide 1 /8-inch extrudates (5.0 g, Alfa Aesar lot no A22M20, stock no 43832, bimodal pore distribution, surface area approximately 255 m2/g). During the preparation, too much solution (9.094 g) was added, and a portion (discarded) was removed with a dropper to bring the amount of the solution remaining to 7.24 g. With this amount of solution, the catalyst was wet, but little solution was visible on the evaporating dish. The catalyst precursor was blue when initially impregnated. It was dried on the steam bath with occasional stirring. The steam bath-dried material was light gray. This material was dried in the muffle furnace over night at 1 1 0 °C. The material was light gray-tan upon removal from the muffle furnace.
• the amount of solution required was calculated from the measured density of solution of Example 1 1 (1 .1 5 g/mL) that was used to prepare the original catalyst precursor such that the volume of the aqueous phosphoric acid solution was the same as that of the solution of Example 1 1 originally used.
• a solution was prepared from 1 .761 g 85% H 3 P0 4 (calculated amount 1 .760 g) diluted to 6.3 ml_ with water and used to impregnate the material recovered from the muffle furnace. The resulting impregnated material was light green.
• An aqueous V/Ti solution was prepared as follows. Ammonium vanadate (0.97 g, 8.28 mmole) and oxalic acid dehydrate (2.09 g, 16.58 mmole) were dissolved in water with stirring at room temperature. The color of this solution changed over the course of an hour from orange to red to brown to brown/green (with the evolution of bubbles) to dark green to dark blue. After waiting about an additional hour, no gas evolution was seen from the blue solution. About 240 mg gas had evolved based on the weight loss of the solution. TBALDH solution (9.89 g, 1 6.6 mmole Ti) was added to yield a dark blue solution (22.62 g). Each gram of this solution contained 0.3665 mmole V (1 8.67 mg) and 0.7339 mmole Ti (35.1 5 mg).
• a zirconium oxide supported catalyst was prepared from a portion of this solution (2.355 g) and zirconium oxide catalyst support (5.0 g, Alfa Aesar lot # B21 T01 0) 1 /8-inch extrudates. This amount was close to incipient wetness and the wet catalyst in the evaporating dish had a light blue color.
• the impregnated material was dried with stirring on the steam bath to yield a material with very light blue color. This material was placed in the muffle furnace and dried overnight at 1 1 0 °C. The material recovered from the muffle furnace was light gray-tan colored.
• this catalyst contained 0.8631 eq V, so 5.5 times that amount (4.747 mmole) of phosphorus was required for the second
• the material recovered from the muffle furnace was gray-tan colored. It was kept in the same evaporating dish and calcined in the muffle furnace for 6 hours at 450 °C. The material recovered from the muffle furnace (5.45 g) was uniformly yellow.
• the catalyst precursor was 2.4 wt% V on Ti0 2 extrudates prepared from aqueous VCI 3 and 1 /1 6-inch Ti0 2 extrudates followed by calcinations at 500 °C for 2 hours.
• 5.0 grams of this catalyst were placed in an evaporating dish and impregnated with 2.81 g titanium(IV) bis(ammonium lactate)dihydroxide, 50 wt% in water (TBALDH), certified to contain 13.4 wt % Ti0 2 , while stirring. This amount of the TBALDH solution (ca.
• the starting charge of the V/Ti0 2 catalyst contained approximately 2.356 mmole V, and the TBALDH solution contained about twice this amount of Ti (about 4.71 mmole).
• the evaporating dish containing the Ti-impregnated V/Ti0 2 material was placed into a muffle furnace and heated at 1 1 0 °C overnight. The catalyst recovered from the muffle furnace has a gray color whereas the starting V/Ti0 2 catalyst was light tan.
• This material was impregnated with a mixture prepared from 85% H 3 P0 4 (1 .494 g, 1 2.96 mmole P) diluted to 2.3 ml_ with water. This amount of solution was also very close to incipient wetness, although the base of the evaporating dish was also wet.
• the evaporating dish was placed on the steam bath and heated with occasional stirring until the extrudates appeared dry.
• the evaporating dish was placed in the muffle furnace and dried at 1 1 0 °C for two hours, then at 500 °C for 6 hours.
• the material recovered from the muffle furnace (6.16) g was a darker tan than the starting V/Ti0 2 material (sort of a gray-tan).
• a solution was prepared from 85% phosphoric acid (3.245 g, 28.147 mmole) and diluted to 5.9 ml_ with water. This amount of P is a 5.5 molar excess over the amount of V already on the silica.
• the silica containing the V and Ti in the evaporating dish was impregnated with all of the aqueous phosphoric acid solution.
• the 5.9 ml_ charge was slightly in excess of the amount required for incipient wetness (perhaps by about 0.5 ml_). The catalyst immediately became dark green, and the residual liquid portion was green.
• a solution was prepared from ammonium vanadate (4.85 g, 41 .5 mmole), oxalic acid (10.45 g, 82.9 mmole), and water (50 ml_). The initial mass of this solution was 64.91 g, and the mass after the gas evolution had ceased was 63.31 g (loss of 1 .60 g).
• the aqueous TBALDH solution (49.43 g, 83.0 mmole Ti) was added to the ammonium vanadate solution. The mass of the resulting solution was 1 1 2.76 g. Each gram of this solution was calculated to contain 0.368 mmole V (1 8.74 mg) and 0.736 mmole Ti (35.26 mg).
• Silica chunks 50.02 g, 8 mesh, Davison Grade 57, Lot 557) were placed in an evaporating dish.
• the silica in the evaporating dish was impregnated to incipient wetness with a portion of the solution (76.43 g).
• the mixture was dried with occasional stirring on the steam bath until free flowing and light blue, then dried further in the muffle furnace at 1 10 °C overnight.
• 64.31 grams were recovered from the muffle furnace.
• the catalyst contained 28.13 mmole V. Each gram contained 0.4374 mmole V (22.28 mg).
• the catalyst was divided up into 6 gram portions for phosphorus loading, so a 6 g charge contained 2.2244 mmole V.
• One feature of the invention is that once the V and Ti are on the support, many different catalysts can be prepared by using different amounts of the phosphorus component to be loaded onto the catalyst as illustrated in Examples 20 through 23.
• This example illustrates the preparation of a molar ratio V/2Ti/3.5P oxide catalyst. 6.0 g of the Example 1 9 catalyst were placed in an
• This catalyst was impregnated with a solution prepared from 85% H 3 PO 4 (1 .06 g, 9.1 8 mmole P) diluted to 5.5 mL (the 5.5 mL dilution provided incipient wetness with this amount of catalyst precursor). The mixture was stirred on the steam bath until free flowing. The catalyst precursor sample was placed in the muffle furnace and dried at 1 1 0 °C for one hour. The dried catalyst was transferred to a clean evaporating dish, returned to the muffle furnace, and then calcined at 450 °C for 6 hours. 5.789 g were recovered.
• This catalyst was impregnated with a solution prepared from 85% H 3 PO 4 (1 .21 g, 1 0.50 mmole P) diluted to 5.5 mL. The mixture was stirred on the steam bath until free flowing. The catalyst precursor sample was placed in the muffle furnace and dried at 1 1 0 °C for one hour. The dried catalyst was transferred to a clean evaporating dish, returned to the muffle furnace, and then calcined at 450 °C for 6 hours. 5.855 g were recovered.
• This example illustrates the preparation of a molar ratio V/2Ti/4.5P oxide catalyst. 6.0 g of the Example 1 9 catalyst were placed in an
• This catalyst was impregnated with a solution prepared from 85% H 3 P0 4 (1 .36 g, 1 1 .81 mmole P) diluted to 5.5 mL. The mixture was stirred on the steam bath until free flowing. The catalyst precursor sample was placed in the muffle furnace and dried at 1 1 0 °C for one hour. The dried catalyst was transferred to a clean evaporating dish, returned to the muffle furnace, and then calcined at 450 °C for 6 hours. 5.999 g were recovered.
• This example illustrates the preparation of a molar ratio V/2Ti/5.0P oxide catalyst. 6.0 g of the Example 1 9 catalyst were placed in an
• This catalyst was impregnated with a solution prepared from 85% H 3 PO 4 (1 .51 g, 1 3.1 2 mmole P) diluted to 5.5 mL. The mixture was stirred on the steam bath until free flowing. The catalyst precursor sample was placed in the muffle furnace and dried at 1 1 0 °C for one hour. The dried catalyst was transferred to a clean evaporating dish, returned to the muffle furnace, and then calcined at 450 °C for 6 hours. 6.085 g were recovered.
• a supported catalyst comprising 5 mole% vanadium and 1 0 mole% phosphorus was prepared in the following way: A white crystalline titanium pyrophosphate (TiP 2 0 7 ) with a specific surface area of 1 00 m 2 /g was first prepared according to the procedure described in I.C. Marcu et al., J. Mol. Catal., Vol. 203, pp. 241 -250 (2003), then crushed and sieved through an 8x14 mesh.
• a solution was prepared from ammonium vanadate (0.1 64 g, 0.0014 mole), 85% H 3 P0 4 (0.326 g, 2.83 mmole), water (1 0 mL), and lactic acid (1 .1 3 g, 1 2.54 mmole).
• the ammonium vanadate dissolved without heating to form a green solution.
• the solution was then added to 6.21 g of the TiP 2 0 7 8X14 meshed material (0.028 mole) in a 1 00 mL single necked round bottomed flask.
• the flask was then placed on a roto-evaporator with a water bath set to 65 °C and rotated in the bath under ambient pressure for 20 minutes, the supernatant turned blue during this time.
• the flask contents were then dried under vacuum at 65 °C and calcined at 450 °C in air for 1 6 hours to give yellow-green irregular shaped particles.
• a supported catalyst comprising 5 mole% vanadium, 1 0 mole% titanium, and 1 0 mole% phosphorus was prepared in the following way: A white crystalline titanium pyrophosphate (TiP 2 0 7 ) with a specific surface area of 100 m 2 /g was first prepared according to the procedure described in I.C. Marcu et al., J. Mol. Catal., Vol. 203, pp. 241 -250 (2003), then crushed and sieved through an 8x14 mesh.
• a solution was prepared from ammonium vanadate (0.1 63 g, 0.0014 mole), TBALDH (1 .67 g, 2.84 mmole), water (1 0 mL), and lactic acid (1 .1 3 g, 1 2.54 mmole).
• the ammonium vanadate dissolved without heating to form an orange solution.
• the solution was then added to 6.21 g of the TiP 2 0 7 8X14 meshed material (0.028 mole) in a 1 00 mL single necked round bottomed flask. The flask was then placed on a roto- evaporator with a water bath set to 65 °C and rotated in the bath under ambient pressure for 20 minutes, the supernatant turned green during this time.
• the catalyst was prepared by suspending ammonium
• TBALDH titanium(IV) bis(ammonium lactato)di hydroxide
• the V/P solution was slowly poured into the TBALDH solution to give a pale green suspension.
• the V/P flask was rinsed with 30 ml_ of water and the contents added to the reaction flask. The mixture was then stirred at 700 to 800 rpm at 1 00 °C for 1 6 hours. The water was then removed via distillation over 4 to 6 h and the resulting damp pale green solid transferred to a ceramic dish and heated in air at 90 °C for 1 6 hours in a muffle furnace. The resulting solid was crushed to fine particles using a mortar and a pestle. This material was then calcined for 6 hours at 450 °C in air (60 SCCM) in a quartz tube to give pale green catalyst particles.
• This material had a BET surface area of 37.9 m 2 /g, was amorphous via X-ray diffraction and had a molar composition of 1 .0V-1 .9Ti-5.2P, as determined by X-ray Fluorescence Spectroscopy.
• the catalyst was regenerated in air (1 00 SCCM) at 400°C overnight after each experiment. Examples 39-44
• Example 43 water was added to the feed at a molar ratio of one mole of methylene diacetate to one mole of water.
• the diluent gas flow rate was lowered to maintain a contact time between reactants and the catalyst at approximately one second.
• the diluent for Examples 39-43 was nitrogen, whereas the diluent for Example 44 was 6% oxygen and 94% nitrogen. The results are summarized in Table 1 6.
• trioxane can be employed in the liquid feed in the absence of additional water. Although this increases the reaction conversion and acrylic acid yield, generally the yields and conversions are substantially lower than the values obtained when methylene diacetate is used as the feed. This is observed even when using trioxane (without water addition) and acetic acid because the net solution still contains one mole of latent molecular water. This underscores the primary advantage of using methylene diacetate, i.e., improvement in space time yields and conversions due to complete elimination of water in the feed.
• the space time yield of acrylic acid is 1 .43 (Comparative Example 1 7) when using a conventional feed (defined as a solution of acetic acid and trioxane) whereas at the same temperature the space time yield is more than double at 3.01 (Example 40) when using a methylene diacetate feed.
• V-Ti-P catalyst The ability of the V-Ti-P catalyst to be regenerated and yield the same reproducible experimental results is advantageous.
• the same catalyst that was used in Example 40 was regenerated overnight at 400°C in a continuous flow of 1 00 SCCM air.
• Example 45 demonstrate that the catalyst activity is reproducible after the regeneration step in air.
• the methylene diacetate conversion (57%) and the space time yield of acrylic acid (3.01 moles/kg catalyst/hr) are the same for each example.
• paraformaldehyde was not formed in either example observed from a lack of solids accumulated in the collection vessel.
• Examples 39-44 was repeated except the V-Ti-P catalyst powder was removed from the reaction tube and replaced with quartz chips. Just as the V-Ti-P catalyst is treated prior to the reaction, the quartz chips were calcined at 400°C overnight in air. The results are given in Table 19. Comparative Example 1 9 demonstrates that the thermal treatment of a quartz surface alone is insufficient for the equivalent production of acrylic acid from a V-Ti-P catalyst.
• the V-Ti-P catalyst powder was removed from the reaction tube and replaced with 1 0 g of tungsten oxide (W0 3 ). Tungsten oxide was chosen since it is a typical oxide used for catalyzing aldol chemistry. Just as the V-Ti-P catalyst is treated prior to the reaction, the tungsten oxide material was calcined at 400°C overnight in air. The same reactor and experimental procedure as used in Examples 39-44 was repeated. The results are given in Table 21 .
• Methylene dipropionate (MDP) was produced from a refluxing mixture of paraformaldehyde and propionic anhydride in the presence of a small amount of sulfuric acid. The reaction was followed by using gas chromatography. Upon completion of the reaction, sodium propionate was added to the mixture to neutralize the sulfuric acid. The mixture was distilled to give 99% pure methylene dipropionate.
• Examples 48 and 49 presented here demonstrate the ability of methylene dipropionate to be used for the production of methacrylic acid; the results are presented in Table 23.
• Examples 48 and 49 show that the V-Ti-P catalyst is highly active towards the production of methacrylic acid from methylene dipropionate (MDP) with 98 mole % and 63 mole % conversion and space time yields of 3.83 and 2.00, respectively, for the methacrylic acid product.
• MDP methylene dipropionate
• the results of Table 23 demonstrate that the STY of methacrylic acid from the conversion of methylene dipropionate decrease with temperature.
• Comparative Example 30 shows the STY of methacrylic acid at 250 °C is 0.1 8 when using a conventional feed of propionic acid and trioxane but a space time yield of 2.00 is obtained at the same temperature when using a feed of methylene dipropionate (Example 49). This more than eleven times higher STY is a benefit of using methylene dipropionate as the feed.
• Tables 23 and Table 24 underscore the differences in space time yields depending on whether the production of methacrylic acid uses a conventional feed comprising varying ratios of propionic acid to formaldehyde to water of 2/1 /3, 2/1 /1 and 2/1 /0 or the production of methacrylic acid with methylene dipropionate as the feed.
• the conventional feed (Table 24, Comparative Examples 23-28) the STY's ranged from 0.01 to 0.73 while when the methylene dipropionate feed is used (Table 23, Examples 48 and 49) the STY's ranged from 2.00 to 3.83. Comparative Example 29

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