Obviousness

The obviousness analysis under 35 U.S.C. § 103 for US Patent 10,926,218 requires identifying combinations of prior art references that would have made the claimed invention obvious to a person having ordinary skill in the art (PHOSITA). A PHOSITA in this field would likely have a background in chemical engineering, environmental engineering, or a related discipline, with experience in pollution control, particularly mercury removal from gas streams. The PHOSITA would be aware of existing methods for mercury capture from flue gases, including the use of activated carbon and various sorbent technologies.

Here are potential combinations of prior art references that could render the claims of US 10,926,218 obvious:

Combination 1: US 4,889,698 + US 6,214,304 + Ghorishi et al. (1993)

• US 4,889,698 (and related patents like 4,956,162, 5,672,323, 5,827,352, 6,027,551, and 5,505,766): These patents generally describe the removal of chemisorbed mercury from gas streams using sorbent particles, which are then collected in a baghouse or electrostatic precipitator (ESP) along with ash particulates.
• US 6,214,304: This patent describes the use of metal oxide sorbents and sodium sulfide particles for mercury removal.
• Ghorishi, B.; Gullet, B. K. Waste Manage Res. 1993, 16, 582: This reference, along with "Lancia references," describes basic silicate or oxide sorbents.

Reasoning for Obviousness (Claims 1, 10, and 17):

A PHOSITA would be aware of the general concept of injecting sorbents into flue gas to capture mercury and collecting the sorbent/mercury in particulate control devices, as taught by US 4,889,698 et al.. While US 6,214,304 teaches sodium sulfide particles and Ghorishi et al. teach basic silicate or oxide sorbents, these references indicate the utility of various materials for mercury capture. The '218 patent claims a promoted activated carbon sorbent (Claim 1), a method of preparing it (Claim 10), and a method for reducing mercury using a sorbent with high capture efficiency and recovery (Claim 17).

The '218 patent explicitly states that "Fine-particle injection sorbents include activated carbon, metal oxide sorbent, sodium sulfide particles, and basic silicate or oxide sorbents." It also notes that "the sulfide and basic silicate and oxide particles are effective only for the oxidized mercury, and the metal oxide sorbents exhibit slower capture kinetics than the carbon particles." This suggests that a PHOSITA would recognize the advantages and limitations of different sorbent types.

Given the existing knowledge of using activated carbon for mercury removal, and the understanding that different additives can influence reactivity and capture, a PHOSITA would have been motivated to explore ways to enhance activated carbon's performance. The references to sulfide and basic silicate/oxide sorbents, while not activated carbon, highlight the ongoing efforts to develop effective mercury sorbents. The '218 patent's assertion that a "major problem with existing carbon injection systems is that the sorbent is initially unreactive" further points to a recognized need in the art for improved carbon sorbents. Therefore, combining the known practice of using activated carbon for mercury removal with the general understanding of promoting sorbent activity through chemical modification, as implicitly suggested by the varying effectiveness of different sorbent types, would have led a PHOSITA to investigate halide promotion of activated carbon.

Combination 2: US 5,891,324 + teachings of the '218 patent regarding known sorbent issues

• US 5,891,324: This patent describes an activated carbon containing an acid (HCl, H2SO4, or H3PO4) for removing mercury from a liquid phase.

Reasoning for Obviousness (Claims 1 and 10):

While US 5,891,324 specifically addresses mercury removal from a liquid phase, it teaches the concept of modifying activated carbon with an acid to enhance mercury adsorption. A PHOSITA would understand that the principles of chemical interaction between a sorbent and mercury could, in some cases, be extrapolated or adapted between liquid and gas phases, especially for the same pollutant. The '218 patent itself discusses the mechanism of oxidation, stating that "Reactions of halogens and acidic species with the basic binding sites on the activated carbon sorbent create sites for oxidizing mercury." This explicitly links acidic species with creating oxidation sites on activated carbon for mercury capture.

A PHOSITA, faced with the known problems of conventional activated carbon sorbents in flue gas (e.g., initial unreactivity and the need for high sorbent-to-mercury ratios), and knowing that acid-treated carbons can remove mercury in liquid phases, would have been motivated to explore whether halide-containing acids (like HBr or HCl, which are halogens/halides as broadly defined in the '218 patent) could be used to treat activated carbon for gas-phase mercury removal. The '218 patent states that "adding the bromine from the bromine reagent or a proton from a hydrogen halide acid to a basic carbene site on the carbon edge structure forms a carbocation that accepts electrons from the neutral mercury atom forming the oxidized mercury species that is bound to the sorbent surface." This highlights the mechanism that an acid, particularly a hydrohalide acid, could contribute to the activated carbon's reactivity.

Therefore, combining the teaching of acid-modified activated carbon for mercury removal from US 5,891,324 with the understanding of the chemical mechanisms involved, as explained in the '218 patent, would have made the use of a hydrohalide-promoted activated carbon for gas-phase mercury removal obvious to a PHOSITA.

Combination 3: General knowledge of halogens as oxidizing agents + existing activated carbon sorbents

• General knowledge: Halogens (like bromine and chlorine) are widely known in chemistry for their oxidizing properties.
• Existing activated carbon sorbents: The prior art clearly indicates the widespread use of activated carbon for mercury removal, albeit with recognized limitations.

Reasoning for Obviousness (Claims 1, 10, and 17):

A PHOSITA would have general chemical knowledge of halogens as oxidizing agents. Given that elemental mercury needs to be oxidized to be effectively captured by many sorbents, and given the known issues with the reactivity of untreated activated carbon, a PHOSITA would have been motivated to explore ways to enhance the oxidative capacity of activated carbon. The '218 patent acknowledges that "the atomic elemental halogen form, which includes the fluorine, chlorine, bromine, and iodine atoms, is about a million times more reactive to mercury." While it notes that the concentration of atomic forms is typically low, the inherent reactivity of halogens with mercury would suggest their potential as promoters.

The '218 patent specifically emphasizes the "halogen/halide promoted activated carbon sorbent" and the reaction of "bromine (or halide or other halogen) with the carbon" to produce a "reactive compound." This directly leverages the known oxidizing power of halogens. A PHOSITA would be motivated to combine the known adsorbent properties of activated carbon with the oxidizing properties of halogens to create a more effective mercury capture sorbent. The '218 patent's description of "in-flight" preparation also suggests an optimization of delivery for an already conceived concept, rather than an entirely novel idea.

Therefore, the combination of the known use of activated carbon for mercury adsorption and the well-understood oxidizing properties of halogens would have made the idea of treating activated carbon with halogens or halides to improve mercury oxidation and capture an obvious endeavor for a PHOSITA seeking to improve existing mercury removal technologies. The specific "new chemically modified carbon (or halocarbon) structure" described in the '218 patent, while detailed, would be the result of a motivated exploration in a known area.

Person Having Ordinary Skill in the Art (PHOSITA):

For this field, a PHOSITA would likely possess a Bachelor's or Master's degree in Chemical Engineering, Environmental Engineering, or Material Science, with several years of experience (e.g., 3-5 years) in industrial pollution control, particularly in flue gas treatment systems for power plants or similar facilities. Their expertise would include:

• Understanding of gas-solid adsorption principles.
• Familiarity with various types of sorbents, especially activated carbon and its applications in emissions control.
• Knowledge of mercury chemistry in flue gas, including its different species (elemental vs. oxidized).
• Awareness of existing mercury control technologies and their limitations (e.g., Powdered Activated Carbon injection, wet scrubbers).
• Basic understanding of chemical reaction mechanisms, including oxidation and catalytic effects.
• Familiarity with analytical techniques used to measure mercury concentrations in gas streams (e.g., CEMs).
• Knowledge of industrial equipment such as baghouses, ESPs, and pneumatic transport systems.

The PHOSITA is not an inventor, but rather a hypothetical person who thinks along conventional lines and is capable of combining known elements in predictable ways. They would be aware of all pertinent prior art.