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 .
Response to Amendment
Applicant’s amendment filed 27 March 2026 has been considered. It is acknowledged that claims 14 and 16-19 have been amended, claims 15 and 20 are canceled, and claims 21-22 are added by Applicant. Accordingly, claims 14, 16-19, and 21-22 are under full consideration.
Response to Arguments
Applicant's arguments filed 27 March 2026 have been fully considered but they are not persuasive. Specifically, Applicant argues that Gastec does not disclose or suggest an SRU having a reaction furnace in a thermal section and three distinct reactors in a catalytic section in which the second reactor has three prescribed catalyst layers. Applicant did not address the cited portions of Gastec that were used to reject the claimed limitations of claim 14. Examiner respectfully disagrees with Applicant’s argument, and kindly encourages Applicant to revisit the rejection of claim 14 where these limitations are addressed. Regarding newly added claim 22, Examiner did not indicate allowability in the interview, but stated that the newly added limitations would likely overcome the rejection as written, and would require further search and consideration, but did not state that the newly added limitations would overcome the prior art of record.
Claim Rejections - 35 USC § 103
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.
Claims 14-17 and 19-20 are rejected under 35 U.S.C. 103 as being unpatentable over Gastec (EP-1442781-A1) in view of Thellefsen et al. (US-20220177307-A1), hereinafter “Thellefsen”.
Regarding Claim 14, Gastec discloses a sulfur recovery unit (SRU) (recovering sulfur; see [0003]) comprising: a thermal section comprising a reaction furnace (a burner with a combustion chamber… the thermal stage; see [0005]) to receive feed comprising hydrogen sulfide (In the thermal stage, the incoming gas stream, which is rich in H2S; see [0006]) and perform an oxidation reaction that converts hydrogen sulfide into sulfur dioxide (on third of the H2S is fully combusted to form SO2; see [0006]) and a first Claus reaction that converts hydrogen sulfide and sulfur dioxide into elemental sulfur (react further to a considerable part, in accordance with the Claus reaction; see [0007] and (2a)); and a catalytic section (catalytic stages; see [0005]) configured to receive hydrogen sulfide and sulfur dioxide from the thermal section (The non-condensed gas, in which the molar ratio of H2S:SO2 is unchanged… are subsequently… passed through a first catalytic reactor; see [0010]) and perform a second Claus reaction (see equation (2)) that converts hydrogen sulfide and sulfur dioxide into elemental sulfur (see equation (2)), the catalytic section comprising: a first catalytic stage comprising a first catalytic reactor (The thermal stage, followed by a number of reactor stages, generally two or three. These reactor stages constitute the so-called catalytic stages; see [0005]) configured to directly receive the hydrogen sulfide and sulfur dioxide from the thermal section (The non-condensed gas, in which the molar ratio of H2S:SO2 is unchanged… are subsequently… passed through a first catalytic reactor; see [0010]); wherein the first catalytic reactor comprises a first catalyst reactor catalyst (reactor filled with catalyst; see [0005]), and wherein the first catalytic reactor is configured to perform the second Claus reaction via the first Claus catalyst (reactor filled with catalyst; see [0005] and equation (2)), a second catalytic stage (The thermal stage, followed by a number of reactor stages, generally two or three. These reactor stages constitute the so-called catalytic stages; see [0005]) comprising a second catalytic reactor (further treat the residual gas of the Claus installation, the so-called tail gas, in a so called tail gas treater; see [0013]); wherein the second catalytic reactor (process according to the present invention can very suitably be carried out in a single reactor; see [0086]) comprises a first catalyst layer comprising a Claus catalyst (gas stream is contacted with a Claus catalyst; see [0040]), a second catalyst layer comprising a hydrogenation catalyst (subsequently to the contacting with the Clause catalyst is contacted with a hydrogenation catalyst; see [0040]), and a third catalyst layer comprising a titania catalyst (subsequently to the contacting with the hydrogenation catalyst is contacted with a hydrolysing catalyst – preferably a titanium oxide containing catalyst; see [0040]), and a third catalytic stage (The thermal stage, followed by a number of reactor stages, generally two or three. These reactor stages constitute the so-called catalytic stages; see [0005]) wherein the first catalytic stage, the second catalytic stage, and the third catalytic stage are disposed operationally in series (The thermal stage, followed by a number of reactor stages, generally two or three. These reactor stages constitute the so-called catalytic stages; see [0005])
Gastec discloses the first catalytic reactor performing the Claus reaction (see above), so it is therefore understood that the first reactor is filled with a Claus catalyst. Gastec does not explicitly teach that alumina is used as the Claus catalyst. However, Thellefsen discloses the use of alumina as a Claus catalyst (material catalytically active in the Claus reaction comprises activated aluminum (III) oxide; see [0047]).
Gastec and Thellefsen are both considered to be analogous to the claimed invention because they are in the same field of sulfur recovery. Therefore, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify Gastec by incorporating the teachings of Thellefsen and using alumina as the Claus catalyst because it provides an efficient process for production of elemental sulfur.
Regarding Claim 15, Gastec and Thellefsen together disclose the SRU of claim 14. Gastec further discloses wherein the thermal section, the first catalytic stage, the second catalytic stage, and the third catalytic stage each have a condenser heat exchanger to condense elemental sulfur (burner with a combustion chamber and a condenser, the thermal stage, followed by a number of reactor stages, generally two or three. These reactor stages constitute the so-called catalytic stages and usually consist of… a sulfur condenser; see [0005]) and discharge the elemental sulfur to a sulfur pit (sulfur formed is condensed, which subsequently flows into a sulfur pit; see [0008]).
Regarding Claim 16, Gastec and Thellefsen together disclose the SRU of claim 14.
Gastec does not explicitly teach a thermal oxidizer. However, Thellefsen discloses a thermal oxidizer to receive tail gas (Claus tail gas combustor; see [0156]) of the SRU comprising hydrogen sulfide from the last catalytic stage (one to four further Claus stages, to provide a final Claus tail gas. The final Claus tail gas comprising H2S is directed to a Claus tail gas combustor; see [0158]) to incinerate the hydrogen sulfide into sulfur dioxide (providing an SO2 converter feed gas; see [0158]). Including a thermal oxidizer, incinerator, or combustor after the catalytic stages would have been obvious to a person of ordinary skill in the art because it would effectively convert the remaining H2S to SO2 (see Thellefsen [0158]) which is important because it is not allowed to discharge residual gas containing H2S to the atmosphere; see Gastec [0013]).
Regarding Claim 17, Gastec and Thellefsen together disclose the SRU of claim 14. Gastec further discloses wherein a catalytic reactor is not operationally disposed between the thermal section and the first catalytic reactor (The non-condensed gas, in which the molar ratio of H2S:SO2 is unchanged… are subsequently… passed through a first catalytic reactor; see [0010]), and wherein the thermal section does not comprise a catalytic reactor (a burner with a combustion chamber and a condenser, the thermal stage; see [0005]).
Regarding Claim 19, Gastec and Thellefsen together disclose the SRU of claim 14. Gastec further discloses wherein the first catalyst layer is disposed at an inlet portion of the second catalytic reactor, wherein the second catalytic reactor has the third catalyst layer disposed at an outlet portion of the second catalytic reactor, and wherein the second catalytic reactor has the second catalyst layer disposed between the first catalyst layer and the third catalyst layer (Modified Gastec discloses this in [0040] where the gas stream is described as first being contacted by the first layer of catalyst (Claus catalyst/alumina), then subsequently contacted with a hydrogenation catalyst, then subsequently contacted by a titania catalyst).
Regarding Claim 21, Gastec and Thellefsen together disclose the sulfur recovery unit of claim 14. Gastec further discloses wherein the third catalytic stage comprises a third catalytic reactor (The thermal stage, followed by a number of reactor stages, generally two or three. These reactor stages constitute the so-called catalytic stages; see [0005]).
Regarding Claim 22, the limitations of this claim do not exceed those of claim 14, except the limitations regarding condensers. Gastec further discloses wherein the thermal section, the first catalytic stage, the second catalytic stage, and the third catalytic stage each have a condenser heat exchanger to condense elemental sulfur (burner with a combustion chamber and a condenser, the thermal stage, followed by a number of reactor stages, generally two or three. These reactor stages constitute the so-called catalytic stages and usually consist of… a sulfur condenser; see [0005]) and discharge the elemental sulfur to a sulfur pit (sulfur formed is condensed, which subsequently flows into a sulfur pit; see [0008]). Gastec does not explicitly teach each and every sulfur condenser as discharging elemental sulfur into a sulfur pit. However, it would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention to modify each and every associated sulfur condenser to discharge to the sulfur to the same location, the sulfur pit, disclosed by Gastec. Since the reference already teaches use of the sulfur pit for collection of condensed sulfur, extending the same collection arrangement to the remaining condensers would have merely represented a predictable use/duplication of known sulfur collection functionality and an obvious matter of system design choice and piping configuration. See MPEP 2143 and 2144.04.
Claim 18 is rejected under 35 U.S.C. 103 as being unpatentable over Gastec (EP-1442781-A1) in view of Thellefsen et al. (US-20220177307-A1), hereinafter “Thellefsen”, further in view of Roisin et al. (US-20130303811-A1), hereinafter “Roisin”.
Regarding Claim 18, Gastec and Thellefsen together disclose the SRU of claim 14. Gastec further discloses wherein the second catalytic reactor is configured to convert carbonyl sulfide (COS) into hydrogen sulfide via the third catalyst layer (A hydrolysing catalyst as used herein is defined as a catalyst capable of hydrolysing COS; see [0043] and “hydrolysing catalyst – preferably a titanium oxide containing catalyst”; see [0040]), wherein the first catalytic reactor is a catalytic reactor that is disposed first in operational position of catalytic reactors in the SRU (The non-condensed gas, in which the molar ratio of H2S:SO2 is unchanged… are subsequently… passed through a first catalytic reactor; see [0010]).
Gastec does not explicitly teach that there is no catalytic reactor between the first and second catalytic reactors. However, Thellefsen does disclose wherein a catalytic reactor is not operationally disposed between the first catalytic reactor and the second catalytic reactor (see Fig. 1, first catalytic reactor (8) and second catalytic reactor (40)). These two reactors are analogous to the claimed first and second catalytic reactors as the Claus reactor of the prior art (8) is a catalytic reactor filled with Claus catalyst (see [0156]), i.e. alumina (see [0158]), and the second catalytic reactor of the prior art (40) is a single vessel wherein there are 3 layers of catalytic material disposed operationally in series (see [0156] and Fig. 1). Excluding a catalytic reactor between the first and second catalytic reactor would have been obvious to a person of ordinary skill in the art before the effective filing date of the claimed invention because the courts have held that omission of an element and its function is obvious if the function of the element is not desired. See In re Kuhle, 526 F.2d 553, 188 USPQ 7 (CCPA 1975) and In reLarson, 340 F.2d 965, 144 USPQ 347 (CCPA 1965). Thellefsen clearly discloses an embodiment wherein a catalytic reactor is not disposed between the first and second catalytic reactors, exemplifying that the system will still operate with this design.
Gastec does not explicitly mention CS2, however, it is known that titania catalyst, as disclosed by Gastec, is capable of converting carbon disulfide into hydrogen sulfide. This is exemplified by Roisin, who discloses the use of titania in the hydrolysis of COS and CS2 (“hydrolysis catalyst comprises titanium oxide… in an amount between 60% and 99.8%”; see [0045]-[0046] and [0070] which shows the hydrolysis reactions that occur in the presence of titanium oxide, including the hydrolysis of COS and CS2). Further, Roisin discloses that the temperature that the hydrolysis reactions are carried out at is preferably between 150oC and 250oC, which aligns with the operating conditions disclosed by Gastec (hydrolysing catalyst – preferably a titanium oxide containing catalyst – at a temperature below 270oC; see [0040]). Accordingly, Gastec does not require any modification to make the second catalytic reactor configured to convert carbon disulfide into hydrogen sulfide because it is already configured to do so by nature of the catalyst used and operating conditions, as taught by Roisin.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to ALYSSA LEE KUYKENDALL whose telephone number is (571)270-3806. The examiner can normally be reached Monday- Friday 9:00am-5:00pm.
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/A.L.K./Examiner, Art Unit 1774
/CLAIRE X WANG/Supervisory Patent Examiner, Art Unit 1774
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