Title of Invention


Abstract Novel catalysts Mn0.90Rh0.10O2 and Mno.93Rho.07O2 have been prepared providing conversion of CO into CO2 at room temperature with good stability for long period. Rhodium doped manganese dioxide catalysts have been prepared by dextrose assisted co-precipitation method and tested for CO oxidation reaction. Rhodium doped manganese dioxide catalysts show enhanced catalytic activity and complete conversion was obtained over Mn0.90Rh0.10O2 catalyst at room temperature. From time on stream experiments it is clear that catalysts are highly stable for CO oxidation reaction for longer period. The activity of the catalysts is stable under the influence of excess oxygen in the feed gas mixture. The XRD pattern authenticates the formation of MnO2 phase. The prepared catalysts are of nano-rod morphology.
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Room temperature oxidation of carbon monoxide to carbondioxide
(a) Name: Salker, Arun V.
Kunkalekar, Rohan k.
(b) Nationality: Indian
(c) Address: Department of chemistry, Goa University
Goa - 403 206., India.
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Title of invention
Room temperature oxidation of carbon monoxide to carbon dioxide
Field of invention
The invention relates to the chemical sciences.
Background of invention with regards to the drawback associated with known art
Carbon monoxide (CO) is one of the main toxic gaseous pollutants which is generally produced and released from industrial, transportation and domestic activities. It causes potential harmful effects on the environment and the public health. It attack haemoglobin more preferentially compared to oxygen, thus depriving the supply of oxygen to different parts of human body. There are reports of many deaths due to CO poisoning. CO is highly stable up to a temperature of 700 °C and remains in atmosphere for several weeks. In recent years many methods have been used to reduce the emissions of CO. The catalytic technologies are attractive because of their low cost and high efficiency. The various types of catalysts have been prepared and tested for CO oxidation reaction [1- 8]. Noble metals are highly active for CO conversions, they generally allow low operating temperatures and higher space velocities then the transition metal oxide based catalysts [1.2]. However due to the high cost of noble metals and their less availability as well as sublimation and sintering problems, considerable part of the research has been devoted to the development of suitable catalyst among the transition metal oxides. Combination of noble metals with transition metal oxides result in materials with high catalytic activity and stability.
Manganese dioxide (MnOz) is important material used widely as catalysts in different fields. It is a non-stoichiometric compound and has many crystalline forms. The properties of

MnO2 are influenced significantly by its structure, morphology and preparation method [3]. Great deal of attention has been paid to the preparation of MnO2 with different crystallographic structures and morphologies. It is known that structural factors, size and orientation of crystallites, dispersity of the material, presence of various kinds of defects and extent to which the composition of compounds deviates from the stoichiometry, determine its chemical properties. The catalytic activity of material is enhanced when its structure becomes distorted. From literature it is found that MnO2 is good catalyst for CO oxidation. The MnO2 in combination with transition metal and precious metal in different preparative form such as supported, doped and mixed oxides, exhibits excellent catalytic activity for CO oxidation reaction [3 - 6].
Object of Invention
The main object is to prepare catalyst which give total conversion of CO at room temperature with good stability and life.
Statement of invention
Mn0.90Rh0.10O2 catalyst showed complete conversion of CO at room temperature and activity of catalyst was stable for longer period indicating good stability of the catalyst.
Summary of invention
Nano-sized rhodium doped manganese dioxide catalysts have been prepared by dextrose assisted co-precipitation method. Prepared catalysts were tested for CO oxidation reaction. Rhodium doped manganese dioxide catalysts showed much better activity and stability for longer period for CO oxidation reaction
A brief description of the accompanying figures

FIG. 1 XRD patterns of MnO2.
FIG. 2 TEM images of catalysts (a) M11O2 and (b) Mno.90Rho.10O2.
FIG. 3 TG-DTA pattern of Mno.90Rho.10O2 catalyst.
FIG. 4 CO oxidation over different catalysts. Conditions: 5% CO, 5% O2 in nitrogen at the flowing rate of 5000 ml h"'.
Detailed description of the invention
Preparation of Catalysts
Rh doped MnO2 of the type Mn].xRhx02 (where X = 0, 0.07 and 0.10) were prepared by dextrose assisted co-precipitation method. Calculated amount of manganese acetate and rhodium chloride (Aldrich) were dissolved in distilled water. Both these solutions were added to 200 ml of 2 % dextrose solution at 100 °C with stirring. NaOH (10%) solution was added drop wise with stirring till complete precipitation (pH = 9). Precipitate was then subjected to oxidation by drop wise addition of 30% H2O2 solution. The suspension was then stirred continuously for next 4 h at temperature 80 - 100 °C. Further the precipitate was filtered, washed with water and ethanol and dried at 150 °C for 6 h. Finally the dried black powder was homogenized in pestle mortar and calcined at 400 °C for 10 h.
Catalyst characterization
The phase composition of the calcined samples was analyzed by X-ray diffraction (XRD) using RIGAKU Ultima IV diffractometer using Cu Ka radiation (λ = 1.5418 nm) with 26 scanning range 10 - 80°. The BET surfaces area was measured by nitrogen adsorption at

liquid Nitrogen temperature using a SMART SORB-91 surface area analyzer. Transmission Electron Microscope (TEM) images were recorded on a PHILIPS CM 200 electron microscope operating with an accelerating voltage of 200 KV and providing a resolution of 2.4 A0. Thermal analysis, i.e. thermogravimetry (TG) and differential thermal analysis (DTA) were carried out on a NETZCH STA 409 PC TG/DTA instrument in air at a heating rate of I0 K mm"1 and heated from ambient to 1100 °C.
Catalytic performance
The catalytic tests for CO oxidation by O2 in N2 were performed at atmospheric pressure in a continuous flow, fixed bed glass reactor. The catalyst powder of 0.9 g was supported between glass wool plugs in a glass reactor which was placed in an electric furnace. The reaction temperature was measured by inserting a thermo-couple in the middle of the catalyst bed. The catalytic activity was determined using a feed gas composition of 5% CO and 5% 02 in nitrogen. All these three gases were first mixed in a mixing bulb. The individual gas flow rates were controlled using flow meters and precision needle valves, previously calibrated for each specific gas. The mixture of gases was then allowed to pass over the catalyst at a flowing rate of 5000 ml h"1. The feed gases and the products were analyzed employing an online Gas Chromatograph with molecular sieve 13X and Porapak Q columns, H2 was used as a carrier gas. The CO was prepared in the laboratory by standard procedure of formic acid disproportionation and further purified by passing through alkali and molecular sieve traps. O2, H2 and H2 gases were used from commercial cylinders.
Influence of excess oxygen on activity of catalyst was carried out by increasing O2 concentration in feed gas composition. Stability of the catalyst for CO oxidation reaction was verified by performing time on stream experiments continuously for 12 h, by maintaining catalyst at constant temperature.

Results and Discussion
Catalyst Characterization
XRD pattern confirms the formation of MnC>2 phase. Fig. 1 shows XRD patterns of MnO2. The TEM images (Fig. 2) of the prepared samples shows that the particles are nano-rods with width of approx 10 nm. The specific BET surface area of all the catalysts has been summarized in Table 1. TG-DTA analysis of all the samples (Fig. 3) showed the initial weight loss at 80 - 140 °C regions due to loss of adsorbed water. The weight loss in the region 600 - 700 °C is attributed to the loss of oxygen and is due to the transformation of MnO2 to M112O3 phase. Further weight loss in the temperature range 920 - 1020 °C is due to the conversion of Mn2O3 to Mn3O4 phase.
Catalytic activity
The incorporation of rhodium in MnO2 greatly improved the catalytic activity of MnO2 for CO oxidation (Fig. 4). it is clear that Mno.90Rho.10O2 catalyst shows complete CO conversion at room temperature, Mno.93Rho.07O2 catalysts show 10% CO conversion whereas pristine M11O2 does not show any conversion at room temperature.
No decline in activity for CO conversion was observed under influence of excess oxygen in feed gas. This indicates that the catalysts are stable for CO oxidation even under higher concentration of oxygen. From time on stream studies which is carried out for 12 h, it is clear that these catalysts are stable for CO oxidation reaction for longer period. No decline in activity was accounted during this period signifying good stability of mese catalysts.


Table 1 Catalytic activity and BET surface area of the catalysts

Catalyst CO Conversion (%) BET surface area OnY')

Room Temperature 65 °C 100 °C

Mn02 0.0 9 17 61
Mno.93Rhoo702 10 100 100 60
100 100 100 91
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3. S. Liang, F. Teng, G. Bulgan, R, Zong, Y. Zhu, J. Phys. Chem. C 112 (2008) 5307.
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We claim,
1. The doped manganese dioxide catalysts which is suitable for CO oxidation at room temperature and containing rhodium as a dopent, wherein the composition of catalysts of the type Mni.xRhxCh-
2. The catalysts of claim 1 which are prepared by co-precipitation technique using dextrose solution.
3. The catalysts of claim 1 of different composition where the value of X = 0, 0.07 and 0.10 respectively.
4. The catalyst Mn0.90Rh0.10O2 gave complete CO oxidation at room temperature with good life.
















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Patent Number 259609
Indian Patent Application Number 2401/MUM/2010
PG Journal Number 12/2014
Publication Date 21-Mar-2014
Grant Date 20-Mar-2014
Date of Filing 27-Aug-2010
Name of Patentee SALKER ARUN V.
# Inventor's Name Inventor's Address
PCT International Classification Number B01J23/00
PCT International Application Number N/A
PCT International Filing date
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