Methods for using macroporous inert materials in monomer production

Abstract

The present invention provides methods for monomer production, for example, acrylic acid, wherein the methods comprise oxidizing one or more reactant gases, for example, propylene, in a fixed bed reactor, preferably, two fixed bed reactors, in the presence of oxygen and a mixed metal oxide catalyst to form an oxidized gaseous mixture and, at any point in the oxidizing, feeding or flowing the one or more reactant gases or the oxidized gaseous mixture through an inert macroporous material that has a pore volume of from 0.2 cm3/g to 2.0 cm3/g, a surface area of from 0.01 to 0.6 m2/g, and wherein from 30 to 98 wt. % of the total pore volume in the inert macroporous material has a pore diameter of at least 100 m.

Claims

1. A method for preparing monomers having an alpha, beta-unsaturated carboxylic acid comprising oxidizing one or more reactant gases selected from propylene, isobutylene, and tert-butanol in a fixed bed reactor in the presence of oxygen and a mixed metal oxide catalyst to form an oxidized gaseous mixture and, at any point in the oxidizing, feeding or flowing the one or more reactant gases or the oxidized gaseous mixture through an inert macroporous material that has a pore volume of from 0.2 cm.sup.3/g to 2.0 cm.sup.3/g, a surface area of from 0.01 to 0.6 m.sup.2/g, and wherein from 30 to 98 wt. % of the total pore volume in the inert macroporous material has a pore diameter of at least 100 m.

2. The method as claimed in claim 1, wherein the oxidizing is conducted in two stages starting with a first stage in a first reactor containing at least one bed containing in the bed a first mixed metal oxide catalyst R1 to generate a gaseous mixture and then a second stage in a second reactor containing at least one bed containing in the bed a second mixed metal oxide catalyst R2 to generate a product comprising a monomer.

3. The method as claimed in claim 2 wherein the bed temperature of the second stage catalyst bed is from 250 to 380 C.

4. The method as claimed in claim 1 wherein the oxidation process is vapor phase oxidation of propylene to acrolein and acrylic acid.

5. The method as claimed in claim 1 wherein the oxidation process is the vapor phase oxidation of isobutene and/or tert-butanol to methacrolein and methacrylic acid.

6. The method as claimed in claim 1 wherein the mixed metal oxide catalyst contains Mo and Bi.

7. The method as claimed in claim 1, wherein the macroporous material is chosen from a silicon oxide, an aluminum oxide, a zirconium oxide, a germanium oxide, mixtures thereof and combinations thereof.

8. The method as claimed in claim 1, wherein in the oxidizing the one or more reactant gas is propylene gas and is oxidized to an acrolein containing gaseous mixture by feeding the propylene gas from the upper stream of a first stage catalyst bed containing in the bed a solid first mixed metal oxide catalyst R1 at a first temperature, and then the resulting acrolein gaseous mixture is oxidized to an acrylic acid product by feeding the acrolein gaseous mixture from the upper stream of a second stage catalyst bed containing in the bed a solid second mixed metal oxide catalyst R2 at a second temperature, wherein the improvement comprises including the macroporous material in at least one of the upper stream of the first stage catalyst bed, the upper stream of the second stage catalyst bed, the bottom stream of the first stage catalyst bed, and the bottom stream of the second stage catalyst bed.

9. The method as claimed in claim 1, wherein the one or more reactant gases are oxidized in at least one first stage catalyst bed in a first tube reactor having a bed containing a solid first mixed metal oxide catalyst R1 at a first temperature, and then the resulting gaseous mixture is oxidized to a monomer product by feeding the gaseous mixture to the upper stream of a second tube reactor having at least one catalyst bed containing a solid second mixed metal oxide catalyst R2 at a second temperature, wherein the improvement comprises including the macroporous material in at the bottom of a first tube reactor, at the interstage region between the first tube reactor and the second tube reactor, top of the second tube reactor, or the bottom of second tube reactor.

10. The method as claimed in claim 1, wherein the alpha, beta-unsaturated carboxylic acid is selected from the group consisting of acrylic acid and methacrylic acid.

11. The method as claimed in claim 10, wherein the alpha, beta-unsaturated carboxylic acid is acrylic acid.

12. The method as claimed in claim 10, wherein the alpha, beta-unsaturated carboxylic acid is methacrylic acid.

Description

EXAMPLES

Comparative Synthesis Example 1

(1) Propylene oxidation to acrolein and acrylic acid was conducted in two stages. Oxidation of propylene is conducted in a first tube reactor to generate a gaseous mixture similar to the first step in a two-step propylene oxidation process to produce acrylic acid. Then, 15 ml of a mixed metal oxide catalyst R1 available from Nippon Kayaku Co. (Tokyo, Japan) was mixed with 15 ml of Denstone 57 material beads (Saint-Gobain Norpro, Stow, Ohio), before being loaded into a 2.54 cm (1) outer diameter (OD) stainless steel (SS) first stage tube reactor (0.834 ID). Denstone 57 material contains alumina in the range of from 19.0 to 26.0 wt. %, and silica in the range of 64.0 to 75.0 wt. %, with minor components from Fe.sub.2O.sub.3, TiO.sub.2, CaO, MgO, Na.sub.2O, and K.sub.2O. Denstone 57 material has surface area of less than 1.0 m.sup.2/g, and pore volume of less than 0.3 cc/g, with 90% of pore size less than 100 m. The tube was heated to 367 C. in a clam-shell electrical furnace. The feed to the first stage tube reactor is a mixture of 24.0 ml/min propylene, 211.6 ml/min air, 34.0 ml/min N.sub.2, and 1.44 gram/h deionized water. The values of all gas flow rates were adjusted to their would be flow rates under standard temperature (0 C.) and standard pressure (101.3 kPa) conditions. The water was injected by a syringe pump into a SS mixer vessel heated to 180 C. The other feed gases were controlled by mass flow controller. About 100-150 ml of the Denstone 57 material was loaded into a separate 2.54 cm OD45.7 cm long (1 OD18 long) SS tube, which serves as a second reactor tube residing in a clam-shell electrical furnace. The effluent from the first stage reactor, designated as P1, was fed directly to the inert bed of the second reactor via a 0.63 cm () SS transfer tube. Both reactors were vertically oriented and in a downflow configuration, i.e., the feed was fed to the top of each reactor.

(2) The product transfer tube between the reactors was heated by heating tape to 260 C. to prevent condensation of the reaction products, especially heavy by-products. The effluent from the first stage reactor or from the second reactor was collected and analyzed periodically. The effluent first flows through a first trap, designated T1, which was cooled by a recirculation chiller at 0-2 C. The gases escaping the first trap flow flowed through a second trap, designated T2, immersed in water/ice, and then through a third trap, designated T3, which was immersed in a dry ice/isopropanol mixture. The trap collection time was 3-4 hours. A 2 wt. % of hydroquinone solution in iso-propanol, or 1000 ppm of phenothiazine in iso-propanol, was used as inhibitor solution. A polymerization inhibitor solution of 6 to 12 grams was injected into each trap before sample collection to prevent polymer formation.

(3) The offgas from T3 was analyzed on-line by a gas chromatograph (GC) equipped with a thermal conductivity detector and a 5 molecular sieve/silica gel column. The main gas components in the off gas typically include nitrogen, oxygen, unreacted propylene, carbon monoxide, and carbon dioxide. The liquids collected from T1 and T2 were combined into one sample, labeled as TS-12, before off-line analysis. The liquid collected from T3 was labeled as TS-3. The TS-12 and TS-3 samples were sent for off-line analysis by a gas chromatogram (GC) equipped with flame ionization detector and a capillary column DB-FFAP 123-3232E (Agilent Technologies, USA). The amounts of major products, such as acrylic acid, acrolein, acetaldehyde, acetone, propionic acid, acetic acid were recorded in Table 2, below.

(4) The TS-12 and TS-3 samples were further analyzed for phthalic acid concentration using high performance liquid chromatography (HPLC). The HPLC instrument parameters are provided in Table 1, below.

(5) TABLE-US-00001 TABLE 1 HPLC Instrumental Parameters Instrument: Agilent 1200 Series Liquid Chromatograph Column: Hypersil GOLD PFP (Thermo Scientific) Dimensions: 4.6 250 mm, 5 m particle size Column Temperature: 25 C. Injection Volume: 2 L Column Flow Rate: 0.96 mL/min Solvent Composition Timetable: % A % B Solvent A = MilliQ 0.0 min 90 10 water with 0.1% 16.0 min 65 35 phosphoric acid 22.0 min 45 55 Solvent B = 22.1 min 90 10 acetonitrile 50.0 min 90 10 (ACN) 51.0 min 90 10 Detector: Diode Array Detector Monitor Signal: 235 nm Data Acquisition Agilent ChemStation, version B.03.01 and Data Analysis:

(6) The phthalic acid standard material was obtained from Sigma-Aldrich (St. louis, Mo.). The initial stock standard solution was prepared in dimethyl sulfoxide (DMSO) solvent at various concentrations between 10-1000 ppm. The working standard solution was prepared by diluting 0.2 g of stock standard in 2 ml of acetonitrile. The working standard solution was filtered with a 0.45 m syringe filter and delivered to a 2 ml autosampler vial for injection into the HPLC.

(7) The reactor temperature of the first stage reactor was maintained at 367 C. to obtain a gaseous mixture. The composition of the effluent was analyzed by GC and the main components are listed in Table 2, below. The concentration of individual components may vary due to variation in experimental control or catalyst performance.

(8) TABLE-US-00002 TABLE 2 Composition of the Comparative First stage reactor effluent P1 Component Mole % CO.sub.2 0.892 C.sub.3H.sub.6 0.217 O.sub.2 5.793 Argon 0.695 N.sub.2 67.368 CO 0.378 H.sub.2O 17.937 Acetaldehyde 0.073 Acetone 0.004 Acrolein 5.929 Acetic Acid 0.038 Propionic Acid 0.000 Acrylic Acid 0.676

(9) The propylene conversion, yield of acrolein and acrylic acid, and relative amount of pthalic acid are calculated according to the equations below.
Propylene conversion (%)=(moles of propylene fedmoles of propylene unreacted)/moles of propylene fed.
Yield of acrolein & Acrylic Acid (%)=(moles of acrolein formed+moles of AA formed)/moles of propylene fed.

(10) The relative total amount of phthalic acid from TS-12 and TS-3 samples verses the total amount of acrolein and AA formed is calculated according to the equations below:
PTA.sub.inert(ppm)=(mass of phthalic acid in TS-12 and TS-3 samples with inert loaded in second reactor tube)/(total mass of acrolein and AA in TS-12 and TS-3 samples with inert loaded in second reactor tube)*1,000,000.

Comparative Example 1A

Inertness of Denstone 57 Material in a Second Stage Reaction

(11) The off gas analysis from Comparative Synthesis Example 1, above, was conducted with 100 ml of Denstone 57 material 6.4 mm () spheres (Saint Gobain Norpro), loaded into a second stage reactor tube. The contact time of Denstone 57 material with the effluent from the first stage reactor in Comparative Synthesis Example 1 was 20 seconds. The effluents from the second stage reactor were collected as described above and analyzed. The temperature of the second stage reactor was controlled at from 270 to 320 C. The resulting propylene conversion, yield of acrolein and AA, and phthalic acid are listed in Table 3, below. The data at 320 C. was the average of two samples.

Example 2

Inertness of MacroTrap XPore 80 Macroporous Material

(12) The off gas analysis from Comparative Example 1, above, was conducted with 110 ml of MacroTrap XPore 80 media 10 mm rings (Saint Gobain Norpro), loaded in the top of a second stage reactor tube. MacroTrap XPore 80 material 10 mm rings contain alumina in the range of 60 to 100 wt. %, and silica in the range of 0 to 40 wt. %. MacroTrap XPore 80 media 10 mm rings have surface area less than 0.25 m.sup.2/g, and a 0.40 to 0.60 cc/g pore volume, with from 0.2 to 0.35 cc/g having with pore size larger than 100 m. The contact time of the MacroTrap XPore 80 material with the effluent from the first stage reactor in Comparative Synthesis Example 1, was 22 seconds. The effluents from the second stage reactor were collected as described above and analyzed. The second stage reactor was controlled at from 270 to 320 C. The propylene conversion, yield of acrolein and AA, and phthalic acid are listed in Table 3, below. The data at 320 C. is the average of three samples.

Comparative Example 3

Inertness of MacroTrap Media 1.5 Material

(13) The off gas analysis from the above Comparative Example 1 was conducted with 120 ml of MacroTrap Media 1.5 material as 6 mm spheres (Saint Gobain Norpro), loaded in the second stage reactor tube. MacroTrap Media 1.5 material contains alumina in the range of 90 to 100 wt. %, and silica in the range of 0 to 10 wt. %. MacroTrap Media 1.5 material has surface area more than 1.50 m.sup.2/g, and from 0.15 to 0.30 cc/g pore volume having a pore size larger than 100 m. The contact time of the MacroTrap Media 1.5 material with the effluent from the first stage reactor in Comparative Synthesis Example 1 was 24 seconds. The effluents from second stage reactor were collected as described above and analyzed. The temperature of the second stage reactor was controlled at 270 and 320 C. The propylene conversion, yield of acrolein and AA, and phthalic acid are listed in Table 3, below. The data at 320 C. is the average of two samples.

(14) TABLE-US-00003 TABLE 3 Change of Reactant Conversion, Product Yield, and Heavy By-product Formation with Various Inert Materials Tem- PTA per- (ppm vs. ature Yield of combined of 2.sup.nd PP acrolein acrolein reactor Conv. + and Example Material tested ( C.) (%) AA (%) AA) Comp. 1A Denstone 270 97.2 90.6 86 57 media 320 97.0 91.4 73.5 2 macroporous material 270 96.8 91.3 83 (MacroTrap 320 96.8 90.3 70 XPore 80) Comp. 3 MacroTrap 270 96.0 93.0 147 Media 1.5 material 320 96.3 92.0 111

(15) The results in Table 3, above, show that the combined yield of acrolein and AA is comparable among the three materials tested, when accounting for experimental error. Surprisingly, the inventive macroporous material of Example 2 MacroTrap XPore 80 yields a much lower amount of PTA (ppm) than the MacroTrap Media 1.5 material in Comparative Example 3.

Example 5

Evaluation Macroporous Material as Overlay on Second Stage Catalyst Bed

(16) The indicated materials were placed in a 30 cm (12) long pre-heating zone that sits right above a second stage catalyst bed in a tandem reactor in which propylene is oxidized into acrolein in the first stage reactor. The acrolein is oxidized into acrylic acid in the second stage reactor. Both the reactors are shell and tube tubular reactors with tubes packed into a cross-sectional area of the tubular reactor, and with catalyst packed in the tubes and heat transfer media circulating between the tubes.

(17) During the scheduled replacement of the overlay inert material bed placed on the top of second stage catalyst, a full row of the tubes with 2.4 cm (0.96) ID were filled with the macroporous material of Example 2 as 6 mm rings, or the media of Comparative Example 3 as 6 mm rings, with the majority of the tubes filled with the Denstone 57 material as 6.4 mm () spheres. The pressure drop (DP) of the catalyst bed both without the loading of the overlay bed was measured one tube at a time using an air pressure test wand to measure air pressure at the top of the tested tube and to measure the resistance flowing through each tube with a desired flow of air at 45 SLPM (Standard Liter per Minute) flowing into the top of the tested tube. A pressure transmitter measured the DP across a loaded reactor tube (with the other end of the reactor tube open to the atmosphere). The reaction was resumed after the overlay replacement was completed. The reaction was stopped about 5 months later. The reactor was opened and the pressure drop of the tubes after the tested overlay material was removed. The pressure drop data are summarized in Table 4, below.

(18) TABLE-US-00004 TABLE 4 Change of DP for the tubes packed with different overlay materials Number of Average Overlay material tubes with DP DP (psi) DP increase in the tube measured Initial Final (%) Example 2 93 10.09 10.69 5.95 C. Ex. 1A 88 10.06 10.85 7.85 C. Ex. 3 93 9.70 10.38 7.01

(19) All the packed tubes had a pressure increase over the 5 months of operation. However, the percentage of DP increase was the smallest in the tubes packed with an inert macroporous material of Example 2, while the highest in the tubes packed with non-porous Denstone57 media.

(20) The tubes packed with the media of Comparative Example 3 had relatively smaller DP increase compared to the tubes packed with the material of Comparative Example 1A.