Daicel Corp v. Celanese Intl Corp

1. Case Identification

• Case #: IPR2014-01514
• Patent #: 8,076,507
• Filed: September 17, 2014
• Petitioner(s): Daicel Corporation
• Patent Owner(s): Celanese International Corporation
• Challenged Claims: 25-28, 31-35, 37, 39-41

2. Patent Overview

• Title: Removal of Permanganate Reducing Compounds from Methanol Carbonylation Process Stream
• Brief Description: The ’507 patent describes an improved process for producing high-purity acetic acid via methanol carbonylation (a variation of the Monsanto process). The invention focuses on removing impurities, known as permanganate reducing compounds (PRCs), while minimizing the loss of costly methyl iodide by using dimethyl ether (DME) in the extraction stage.

3. Grounds for Unpatentability

Ground 1: Anticipation over the ’095 patent - Claims 25-28, 31-35, 37, and 39-40 are anticipated by 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, discloses every element of the challenged claims. The core of the argument rested on inherency. Although the ’095 patent did not explicitly mention the presence of dimethyl ether (DME), Petitioner asserted that DME is necessarily and inherently formed under the distillation conditions described, which include the presence of water, methanol, and an acid catalyst. To support this, Petitioner submitted experimental evidence (the Miura Declaration) allegedly demonstrating that replicating the process of the ’095 patent inevitably produces DME in the overhead stream.
  • Key Aspects: The argument for this ground centered on the assertion that the presence of DME was not a novel inventive step but rather an inherent, previously unmentioned property of the established prior art process.

Ground 2: Anticipation over the ’171 patent - Claims 25-28 and 35 are anticipated by the ’171 patent.

• Prior Art Relied Upon: ’171 patent (Patent 6,339,171).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner contended that the ’171 patent, which is assigned to the Patent Owner and was cited as prior art during prosecution of the ’507 patent, also inherently anticipates the challenged claims. The process flow diagram in the ’171 patent is nearly identical to the admitted prior art diagram in the ’507 patent. Crucially, the ’171 patent explicitly teaches adding water to the distillation column to inhibit the formation of certain impurities. Petitioner argued that this deliberate addition of water into the distillation process, which contains methanol and methyl iodide (a precursor to an acid catalyst), creates the exact conditions that necessarily and inherently form DME. Therefore, the ’171 patent was alleged to teach all limitations of the claims, with the DME limitation being inherently met.

Ground 3: Obviousness over the ’171 patent, the ’095 patent, and Akinori - Claims 25-28, 31-35, 37, 39, and 40 are obvious over the combination of these references.

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

• Core Argument for this Ground:

  • Prior Art Mapping: As an alternative to anticipation, Petitioner argued obviousness. The ’095 and ’171 patents were asserted to disclose the fundamental process for removing PRCs from an acetic acid stream via distillation and extraction. The Akinori reference, a well-known scientific paper on the Monsanto process, was cited to show that the formation of DME via the dehydration of two methanol molecules was a known equilibrium side reaction in this exact chemical environment. Petitioner contended that a person of ordinary skill in the art (POSITA), when implementing the processes of the ’095 or ’171 patents, would have known from Akinori that DME would be formed.
  • Motivation to Combine: A POSITA would combine these references because they all pertain directly to the production of acetic acid via the Monsanto process. It would have been routine for a POSITA implementing the purification systems of the ’095 or ’171 patents to consult foundational literature like Akinori to understand the underlying chemistry and potential side reactions, including the formation of DME.
  • Expectation of Success: A POSITA would have had a high expectation of success because Akinori explicitly describes the chemical reaction that forms DME, and the necessary reactants (methanol, water, acid catalyst) were all present in the systems disclosed by the ’095 and ’171 patents.

• Additional Grounds: Petitioner asserted an additional obviousness challenge against claims 25-28, 31-35, 37, and 39-41 based on the combination of the ’171 patent, the ’095 patent, Akinori, and JP 2000-72712. This ground was presented to reinforce arguments for specific claim limitations, particularly the recycling of the raffinate stream.

4. Key Claim Construction Positions

• "PRC enriched overhead stream": Petitioner proposed this term should be construed broadly to mean "a stream containing PRC's," consistent with its use in the specification.
• "forming dimethyl ether" / "produce dimethyl ether": Petitioner argued these terms should be construed to mean that DME is formed or produced through the known equilibrium reactions that occur during the process, rather than requiring an active step of adding pre-formed DME. This construction was central to the inherency and obviousness arguments.
• "at least a portion of said raffinate stream is directly or indirectly back into said methanol carbonylation reactor": Petitioner proposed this phrase should be understood to mean the stream is "recycled," which is a standard practice in such chemical processes.

5. Key Technical Contentions (Beyond Claim Construction)

• The central technical contention of the petition was that the formation of DME is an inherent and unavoidable consequence of operating a methanol carbonylation purification process under the conditions disclosed in the primary prior art references (’095 and ’171 patents). Petitioner argued that the presence of water, methanol, and an acid catalyst (or its precursors) in a distillation column at elevated temperatures makes the formation of some amount of DME a scientific certainty, meaning its "presence" was not an invention but merely a later-observed phenomenon of a known process.

6. Relief Requested

• Petitioner requested the institution of an inter partes review and the cancellation of claims 25-28, 31-35, 37, and 39-41 of Patent 8,076,507 as unpatentable.