PTAB

IPR2015-00171

Daicel Corp v. Celanese Intl Corp

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Removal of Permanganate Reducing Compounds from Methanol Carbonylation Process Stream
  • Brief Description: The ’507 patent discloses an improved process for producing acetic acid via methanol carbonylation, a variation of the well-known Monsanto process. The invention is directed to reducing the loss of costly methyl iodide during the removal of permanganate reducing compounds (PRCs), such as acetaldehyde, by introducing dimethyl ether (DME) into an aqueous extraction step.

3. Grounds for Unpatentability

Ground 1: Anticipation over ’095 Patent - Claims 42-44, 47-51, 53, and 55-56 are anticipated under 35 U.S.C. §102 over the ’095 Patent.

  • Prior Art Relied Upon: ’095 patent (Patent 5,625,095).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the ’095 patent, which describes a process for producing high-purity acetic acid, expressly taught every element of the challenged claims. This included distilling a mixture containing PRCs and performing at least two consecutive aqueous extraction steps to separate acetaldehyde from methyl iodide. The only limitation not explicitly disclosed in the ’095 patent was the presence of DME in the PRC-enriched overhead stream.
    • Key Aspects: Petitioner contended that DME is inherently and necessarily produced under the Monsanto process conditions disclosed in the ’095 patent. This assertion of inherency formed the core of the argument and was supported by expert declarations and confirmatory experimental results designed to show that practicing the teachings of the ’095 patent inevitably results in the formation of DME.

Ground 2: Obviousness over ’171 Patent, ’095 Patent, and Akinori - Claims 42-44, 47-51, 53, and 55-56 are obvious over the ’171 Patent in view of the ’095 Patent and Akinori.

  • Prior Art Relied Upon: ’171 patent (Patent 6,339,171), ’095 patent (Patent 5,625,095), and Akinori (a 1977 journal article).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner asserted that the ’171 patent taught a virtually identical acetic acid production process, including the distillation of a PRC-containing stream and a subsequent aqueous extraction. However, the ’171 patent did not explicitly require multiple extraction stages. Petitioner relied on the ’095 patent to demonstrate that employing two or more extraction stages was a well-known and conventional technique for improving impurity removal in such processes. The presence of DME, while not explicitly mentioned in the primary references, was rendered obvious by Akinori, which explained that DME formation is a known equilibrium side reaction in the Monsanto process.
    • Motivation to Combine: A POSITA would combine the teachings of the ’171 and ’095 patents to enhance the efficiency of PRC removal, as applying a second extraction is a simple, known method for increasing purification. All references are directed to the same field of technology. A POSITA seeking to optimize the process would also consult literature like Akinori to understand the underlying chemistry, including known side reactions like DME formation, and would therefore expect its presence.
    • Expectation of Success: A POSITA would have a high expectation of success in combining the references, as it involved applying known purification techniques (multiple extractions) to a known process to achieve the predictable result of improved purity. The presence of DME was not an unexpected discovery but an understood consequence of the process chemistry.

  • Additional Grounds: Petitioner asserted an additional obviousness challenge against claims 42-44, 47-51, 53, and 55-57 based on the combination of the ’171 patent, ’095 patent, Akinori, and JP 2000-72712, which provided further evidence on the known benefits of recycling process streams to improve efficiency and reduce waste.

4. Key Claim Construction Positions

  • "PRC enriched overhead stream": Petitioner proposed this term be construed simply as "a stream containing PRC's," arguing this interpretation was consistent with its use throughout the specification.
  • "raffinate stream": As the term was not defined in the patent, Petitioner argued it should be given its standard industry meaning: the refined fraction remaining after impurities are removed by solvent extraction. In the context of the patent, this refers to the non-aqueous phase that retains the valuable methyl iodide.
  • "less than about 400 [or 250] parts per million": Petitioner contended that in the absence of a specific definition in the patent, the term "about" should be interpreted to encompass a range of at least +/- 10% of the stated value. This construction was critical to its argument that the 270 ppm of propionic acid disclosed in the ’095 patent anticipated the "less than about 250 ppm" limitation of claim 50.

5. Key Technical Contentions (Beyond Claim Construction)

  • Inherency of DME Formation: A central technical argument across multiple grounds was that dimethyl ether (DME) is an inherent and unavoidable byproduct of the Monsanto process under the conditions described in both the ’507 patent and the prior art. Petitioner argued that DME is formed through a well-understood equilibrium reaction involving methanol. Therefore, its presence was not a patentable distinction but a necessary and expected consequence of the prior art process chemistry, a position supported by expert testimony and experimental data.

6. Relief Requested

  • Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 42-44, 47-51, 53, and 55-57 of Patent 8,076,507 as unpatentable.