Prior art

U.S. Patent 9363997 (hereinafter '997 patent) describes methods and compositions for generating non-equilibrium peroxyacetic acid (PAA) solutions on-site at the point-of-use. The methods involve introducing triacetin and aqueous hydrogen peroxide to water, mixing, and then adding an aqueous source of an alkali metal or earth alkali metal hydroxide. Triacetin is rapidly converted into PAA with a high conversion rate, producing solutions with high levels of PAA. The patent also discloses a solid bleaching and stain removal composition.

Here's an analysis of the prior art cited in the '997 patent:

1. U.S. Pat. No. 7,012,154 (Agnihotri et al.)

• Full Citation: US7012154B2
• Publication/Filing Date: The '997 patent cites it as a U.S. Patent. The earliest priority date listed for the '997 patent is March 24, 2011, making US'154 a prior art reference.
• Brief Description: This patent discloses a system for the continuous, on-site, and on-demand production of aqueous peracetic acid. It involves feeding acetic acid, hydrogen peroxide, water, and sulfuric acid to a jacketed reactor, followed by a wiped-film distillation column to condense and isolate pure PAA before introducing it to receiving water.
• Potential Anticipation (35 U.S.C. § 102): US'154 describes a system for generating PAA on-site at the point-of-use. While it utilizes different reagents (acetic acid and sulfuric acid catalyst) and a more complex distillation process, it discloses the core concept of on-site PAA generation. It could potentially anticipate claims relating to the general method of generating non-equilibrium PAA on-site, particularly method claims that are broad enough to encompass various chemical pathways for PAA formation, if not sufficiently distinguished by the specific reagents and reaction conditions (e.g., using triacetin and alkali metal hydroxide).

2. U.S. Pat. No. 6,171,551 and 6,387,236 (Deemer et al.)

• Full Citation: US6171551B1 (no snippet provided, but mentioned in '997 patent text), US6387236B1 (no snippet provided, but mentioned in '997 patent text)
• Publication/Filing Date: The '997 patent cites these as U.S. Patents, thus preceding its priority date.
• Brief Description: These patents disclose electrolytic processes for producing PAA and other oxidants in the anode compartment of a cell divided by an ion-exchange membrane, using an aqueous solution of acetic acid or acetate salt. [cite: 9363997B2]
• Potential Anticipation (35 U.S.C. § 102): These references describe methods for generating non-equilibrium PAA on-site using an electrolytic approach. They could potentially anticipate claims in the '997 patent that broadly cover on-site PAA generation, especially those focusing on the "non-equilibrium" aspect, unless the '997 patent's claims are specifically limited to chemical (non-electrolytic) generation, or the specific reagents (triacetin, hydrogen peroxide, alkali) and their combination.

3. WIPO International Publication Nos. WO 2004/0245116 and WO 2008/140988, and U.S. Patent Application Publication No. 2009/0314652

• Full Citation: WO20040245116A1 (no snippet provided, but mentioned in '997 patent text), WO2008140988A1 (no snippet provided, but mentioned in '997 patent text), US20090314652A1 (no snippet provided, but mentioned in '997 patent text)
• Publication/Filing Date: These publications precede the priority date of the '997 patent.
• Brief Description: These references disclose cation membrane-divided electrolysis cells and gas diffusion electrodes to reduce oxygen gas to hydrogen peroxide under alkaline conditions. The hydrogen peroxide then reacts with acetic acid or an acetyl precursor to form PAA in the bulk solution, which is then directed to the acidic anode compartment for stabilization. [cite: 9363997B2]
• Potential Anticipation (35 U.S.C. § 102): Similar to the previous electrolytic references, these disclose on-site PAA generation. The inclusion of an "acetyl precursor" and the reaction with hydrogen peroxide to form PAA could potentially anticipate claims in the '997 patent that are broadly directed to using an acetyl precursor and hydrogen peroxide, especially if the claims do not sufficiently define the specific liquid acetyl precursor (triacetin) or the non-electrolytic process.

4. U.S. Pat. No. 5,122,538 (Bowman et al.)

• Full Citation: US5122538A (no snippet provided, but mentioned in '997 patent text)
• Publication/Filing Date: This patent precedes the priority date of the '997 patent.
• Brief Description: This patent describes generating non-equilibrium PAA at the point-of-use by substituting traditional mineral acid catalysts with sulfonic acid ion-exchange resins. A solution of acetic acid to hydrogen peroxide is passed through a resin column to produce PAA. [cite: 9363997B2]
• Potential Anticipation (35 U.S.C. § 102): This reference teaches on-site PAA generation using a chemical reaction, specifically employing an ion-exchange resin. It could potentially anticipate claims relating to the chemical generation of PAA on-site if the claims are not specifically limited to the use of an alkali metal or earth alkali metal hydroxide as the catalyst, or the specific liquid acetyl precursor (triacetin).

5. U.S. Pat. No. 3,432,546 (McManus)

• Full Citation: US3432546A (no snippet provided, but mentioned in '997 patent text)
• Publication/Filing Date: This patent precedes the priority date of the '997 patent.
• Brief Description: This patent discloses a process where hydrogen peroxide, acetic anhydride, and an ammonium hydroxide catalyst are metered to a tubular reactor to continuously produce a PAA solution. [cite: 9363997B2]
• Potential Anticipation (35 U.S.C. § 102): This reference teaches the continuous on-site production of PAA from hydrogen peroxide and an acetylating agent (acetic anhydride) using a basic catalyst (ammonium hydroxide). It could potentially anticipate claims that broadly cover the continuous generation of PAA from hydrogen peroxide and an acetyl precursor in the presence of an alkaline source, unless the claims specifically distinguish the use of triacetin and/or the type of alkali metal hydroxide, and the absence of ammonium hydroxide.

6. U.S. Patent Application Publication No. 2009/0043132 (Harvey et al.)

• Full Citation: US20090043132A1 (no snippet provided, but mentioned in '997 patent text)
• Publication/Filing Date: This publication precedes the priority date of the '997 patent.
• Brief Description: This process involves introducing hydrogen peroxide into a sidestream of water, followed by introducing acetic anhydride, to generate PAA in-situ. [cite: 9363997B2]
• Potential Anticipation (35 U.S.C. § 102): This reference describes on-site PAA generation using hydrogen peroxide and acetic anhydride. Similar to US3432546A, it could potentially anticipate claims broadly covering the on-site generation of PAA from hydrogen peroxide and an acetyl precursor if the claims do not sufficiently define the specific acetyl precursor (triacetin) or the alkaline conditions used in the '997 patent.

7. WIPO International Publication No. WO 01/46519 A1 (Bodmer et al.)

• Full Citation: WO0146519A1 (no snippet provided, but mentioned in '997 patent text)
• Publication/Filing Date: This publication precedes the priority date of the '997 patent.
• Brief Description: This process involves metering an aqueous solution of hydrogen peroxide into an agitated tank and co-metering a solid dry source of tetraacetylethylenediamine (TAED) from a hopper. This mixture is then fed to an in-line static mixer where aqueous sodium hydroxide is introduced, followed by coiled tubing in a cooling tank to contain the exothermic reaction. [cite: 9363997B2]
• Potential Anticipation (35 U.S.C. § 102): This reference is highly relevant as it describes on-site PAA generation using hydrogen peroxide, a solid acetyl precursor (TAED), and aqueous sodium hydroxide, with subsequent mixing and reaction time. It clearly demonstrates a system for generating PAA on-site using an alkali. This could potentially anticipate claims of the '997 patent that broadly cover the method of introducing hydrogen peroxide and an acetyl precursor to water, mixing, and then adding an aqueous source of alkali metal hydroxide to form PAA. The '997 patent distinguishes itself by using a liquid acetyl precursor (triacetin) and potentially highlighting the advantages of its specific composition and method over TAED-based systems (e.g., solubility, odor). Therefore, claims specifically reciting "liquid acetyl precursor" or "triacetin" would be important for distinguishing this prior art.

8. U.S. Pat. No. 7,651,724 (Gordon et al.)

• Full Citation: US7651724B2 (no snippet provided, but mentioned in '997 patent text)
• Publication/Filing Date: This patent precedes the priority date of the '997 patent.
• Brief Description: The '997 patent refers to this patent for its "modified DPD method" of analysis, a colorimetric method for measuring total chlorine in drinking water and wastewater, adapted for measuring PAA and hydrogen peroxide. [cite: 9363997B2]
• Potential Anticipation (35 U.S.C. § 102): This patent describes an analytical technique and not a method or composition for generating PAA. Therefore, it is unlikely to anticipate any claims of the '997 patent related to the methods or compositions for PAA generation, but it could be relevant for any claims regarding methods of measuring PAA or hydrogen peroxide if such claims were present and broadly drafted.

It is important to note that the provided patent text for US9363997B2 itself discusses the limitations and problems of these prior art methods, indicating that the '997 patent aims to overcome these issues with its specific compositions and methods. The distinctiveness of the '997 patent likely lies in the use of triacetin as a liquid acetyl precursor, its unexpected solubility in hydrogen peroxide, the specific alkaline conditions for rapid and high conversion to PAA, and the absence of certain undesirable byproducts or complex equipment.