DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claims 1-12 are rejected under 35 U.S.C. 103 as being unpatentable over Krill et al (US 2017/0305830 A1) in view of May (EP 3608305 A1 published 12-02-2020 =US 2021/0317064 A1 same family).
Applicants claimed invention is directed to a process for producing methacrylic acid comprising: a) producing methacrolein from propionaldehyde and formaldehyde;
b) producing methacrylic acid in an oxidative reaction from the methacrolein produced
in step a) and water; wherein: step b) is performed at a pressure above 1 bar;
step b) is performed in a reactor system in a liquid phase reaction in the presence of a
heterogeneous noble metal-containing catalyst, wherein the reactor system comprises an oxygen-containing gas; an average concentration of methacrolein in step b) is less than 40 wt% based on the total weight of water and methacrolein; and the reactor system of step b) has an average ratio of water to methacrolein less than 40:1 based
on an average amount of water and methacrolein entering and exiting the system.
Krill teaches a process for continuously preparing methacrylic acid, in which methacrolein is prepared in a first process step from formaldehyde and propionaldehyde with at least one acid and at least one organic base as catalysts in a reactor 1, then separated from the catalyst-containing or aqueous phase present and oxidized in a second process step to methacrylic acid with a heterogeneous catalyst in the presence of oxygen and water in a reactor 2, the overall reaction is a multi-stage reaction [0013] and abstract.
Krill teaches the water content of the crude methacrolein from the distillation can vary as a function of temperature. Preferably, the reaction mixture obtained after the reaction of formaldehyde with propanal is accordingly cooled to a temperature at which the water content in the methacrolein phase is established. Preferably, the temperature in the phase separator can be set between 0 and 50° C., preferably 5 to 30° C. and more preferably 10 to 25° C [0045].
Krill teaches the reaction in process step 1 at a temperature of 100 to 300° C., a residence time of the reaction mixture in reactor 1 between 1 and 30 s, more preferably between 5 and 15 s, and at a pressure of 5 to 100 bar. Preferably, the feed into reactor 1 has a ratio of propionaldehyde to formaldehyde between 1:1.2 mol and 1:0.8 mol [0039].
Krill teaches a process for preparing methacrylic acid on the basis of C2 units. In this process, for example, propionaldehyde is prepared in a precursor from ethylene [0002].
Analysis of the Difference
The present claim recites maintaining an average molar ratio of water to methacrolein of less than 40:1 in the reactor feed or reaction mixture.
The primary reference to Krill establishes the general oxidation of methacrolein in the presence of oxygen and water but does not explicitly quantify the specific molar ratio of water to methacrolein. Therefore, the present claim differs s from Krill by explicitly bounding the average ratio of water to methacrolein to a value less than 40:1.
It would have been obvious to a person having ordinary skill in the art, prior to the effective filing date of the claimed invention to modify the methacrolein oxidation process of Krill by utilizing the precise water-to-methacrolein taught by May, thereby arriving at an average water to methacrolein ratio of less than 40:1.
A PHOSITA would be motivated to look to May because May explicitly solves the problem of optimizing fluid composition during oxidative esterification of methacrolein over noble metal catalysts. May directly guide the artisan to minimize water content to at most 10% or 5% by weight of the reaction mixture [0068] to maintain reaction efficiency.
Furthermore, looking at May’s explicit reactor feed example, the gas mixture contains 17 vol% water vapor and 4 vol% methacrolein. Because volume percentages for gases correspond directly to molar ratios, May’s feed represents a strict water to methacrolein molar ratio of 4.25 to 1 (17/4). This value of 4.25:1 falls squarely and completely within the claimed range of less than 40:1.
Limiting the water ratio below 40:1 represents routine optimization of a result-effective variable (moisture control) to prevent catalyst flooding, minimize side reactions, and maximize the yield of methyl methacrylate. Because May provides an explicit layout operating well below the 40:1 maximum threshold, the claimed ratio is entirely predictable and lacks patentable distinction under 35 U.S.C. 103.
May teaches that the methacrolein is oxidized in the presence of an oxygen containing gas and optionally an alcohol to methacrylic acid or a methacrylic acid ester. Thereby, process step d) is preferably an oxidative esterification of Methacrolein which is carried out in a liquid phase at a pressure from 1 to 100 bar and in the presence of a heterogeneous noble-metal-comprising catalyst. In addition, it is preferred that said heterogeneous catalyst comprises a metal and/or a metal oxide [0058].
May teaches the water content of the reaction mixture used for the oxidative esterification in this embodiment of step d) is preferably at most 10% by weight and with preference at most 5% by weight [0068].
May teaches heterogeneous oxidation catalysts preferably comprise at least one noble metal and, in most cases, at least one metal oxide. Preference is given here to oxidation catalysts in which gold and/or palladium and/or ruthenium and/or rhodium and/or silver are present. Gold- and/or palladium-containing catalysts are particularly preferred [0064].
May teaches the amount of the catalyst to be used varies, depending on the composition of the feed mixture and of the catalyst, on the reaction conditions, and on the types of reaction and the like. If the catalyst used takes the form of a slurry, it is preferable that the amount used of the catalyst is from 0.01 to 0.5 kg/l of the reaction system solution [0069].
May discloses 9 g of the catalyst were charged into a glass micro-reactor having an inner diameter of 16 mm, and a starting gas composed of 4 vol % of methacrolein, 12 vol % of molecular oxygen, 17 vol % of water vapor and 67 vol % of nitrogen, prepared by mixing methacrolein, air, steam and nitrogen, was fed to the reactor. After carrying out the reaction for 1 hour from the re-start of the reaction, an exit gas (a gas after reaction) was sampled and analyzed by gas chromatography, and a conversion of methacrolein (percent), a selectivity of 80% to methacrylic acid (percent) and a yield of 77% methacrylic acid were obtained at 96% conversion [0112].
Regarding oxygen range limitations (1mol% to 7.5 mol%), May explicitly teaches a representative gas feed example of the oxidative esterification of methacrolein comprising 12 vol%.
It would have been obvious to a person having ordinary skill in the art, prior to the effective filing date of the claimed invention to lower and optimize the oxygen content to fall within the claimed 1 mol% to 7.5 mol% range. May teaches that the oxidative esterification reaction occurs over a heterogenous noble metal catalyst in the presence of oxygen. A PHOSITA would routinely balance the concentration of oxygen in the gas phase as a result-effective variable to achieve maximum conversion while strictly avoiding flammable or explosive gas-phase envelopes (which typically require keeping oxygen below safe structural limits). Adjusting a gas component’s percentage to optimize reaction kinetics and plant safety is a matter of routine optimization yielding entirely predictable results.
Regarding catalysts in the form of a slurry or fixed bed, May teaches charging 9 grams of catalyst into a glass micro reactor to process a starting gas feed [0112]. Krill generally teaches reacting components using a heterogeneous catalyst in a second reactor step [0013]. The dependent claim explicitly defines the structural form of the heterogenous catalyst as a slurry or a fixed bed.
It would have been obvious to PHOSITA to deploy the heterogenous catalyst of Kril and May in the form of a slurry or a fixed bed. In chemical engineering, fixed bed and slurry configurations are the two most standard choices for handling a solid-state heterogenous catalyst with fluid reactants. Choosing between a fixed bed (where fluid flows through packed solid catalyst beads) or a slurry bed (where fine catalyst particles are suspended in the liquid) is a routine design choice based entirely on known chemical trade-offs, such as pressure drop constraints or heat dissipation needs. The selection of these standard reactor formats provides no unexpected results and lacks patentable distinction.
The dependent claim specifies that the system comprises a multizone reactor and the second reactor (step b) is a single reactor.
It would have been obvious to a PHOSITA to configure the physical layout of Krill’s system so that the respective steps are housed within a multizone reactor framework or consolidated into a single standalone vessel for step b). Defining whether a reaction sequence takes structural shell (multizone reactor) or utilizes an individual detached vessel (single reactor) is a matter of routine mechanical layout and plant engineering. A PHOSITA would adapt these configurations based entirely on predictable goals, such as minimizing the plant’s footprint, managing thermal recycling, or simplifying fluid piping. Because this structural allocation produces entirely expected chemical outcomes, it fails to overcome the threshold of obviousness.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to JAFAR F PARSA whose telephone number is (571)272-0643. The examiner can normally be reached M-F 10:00 AM-6:30PM.
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/JAFAR F PARSA/ Primary Examiner, Art Unit 1692
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