Method and apparatus for reducing nitric oxide

A method and apparatus for reducing nitric oxide in a gas with ammonia in the presence of a base metal catalyst pretreated with sulfur, selenium or a sulfur compound positioned in a reactor. The catalyst is deposited on a substrate or confined between gas-permeable walls and arranged to form open channels through which the nitric oxide-containing gas thereby effects low pressure drop through the reactor.

BACKGROUND OF THE INVENTION 
This invention relates to a method and apparatus for catalytically reducing 
nitric oxide with ammonia in a reactor having channels arranged to provide 
a low pressure drop through the reactor. 
Nitrogen oxides, particularly nitric oxide, are undesirable products of 
reaction which result when carbonaceous fuels are burned such as in power 
plant operations. 
Various techniques have been proposed for removing nitric oxides from 
gaseous streams to prevent pollution of the atmosphere, such as 
absorption, scrubbing and catalytic conversion. 
Catalytic reduction of nitric oxides with ammonia or hydrogen in the 
presence of nickel and oxides of iron and chromium has been proposed (U.S. 
Pat. No. 2,381,696; U.S. Pat. No. 3,800,796; and German Pat. No. 
1,259,298). The reaction is exothermic and without control of the 
temperature in the catalyst bed, combustion of the ammonia is likely to 
occur. 
Removal of nitric oxides from tail gas streams of nitric acid plants has 
been attempted by reaction with ammonia, hydrogen or methane over a 
catalyst consisting of a supported metal of the platinum group. Anderson 
et al, Ind. Eng. Chem., Vol. 53, p. 199 (1961) and Adlhart et al, Chem. 
Eng. Prog., Vol. 67, pp. 73-78 (1971). With this method, there has been 
difficulty with control of the exothermic reaction, which results in 
pressure surges and overheating of the reactor. Also, in some instances, 
hydrogen cyanide is produced as a by-product. 
In power plant emissions, the gaseous effluent typically contains as the 
major source of pollutants sulfur oxides or sulfur dioxide and nitric 
oxides. It has been found possible to separate the sulfur dioxide from the 
effluent and to treat the sulfur dioxide separately or to control the fuel 
sulfur content. This results in an effluent primarily containing sulfur 
dioxide as less than 2000 ppm, nitric oxide, oxygen and nitrogen and water 
vapor. 
The prior art methods for catalytically reducing nitric oxide with ammonia 
as a reducing gas experience problems with the temperature of operation 
required to maintain the efficiency of the catalyst employed, 
deterioration of the catalyst, controlling exothermic reactions and 
preventing the formation of byproducts which are pollutants, particularly 
nitrous oxide. 
The use of a base metal catalyst to reduce nitric oxide to nitrogen with 
ammonia in the presence of oxygen and sulfur dioxide has been suggested, 
German Pat. No. 1,259,298. However, the catalyst life is limited and no 
controls are provided for the prevention of the formation of nitrous oxide 
and the exothermic reaction is difficult to control. Further, in similar 
component systems for the reduction of nitric oxide to nitrogen with 
ammonia, the use of a copper promoted catalyst on a catalytic support such 
as alumina, silica or diatomacous earth is suggested, U.S. Pat. No. 
3,008,796. The reaction rates are not such that such a process would be 
considered economically possible for the treatment of a gaseous stream 
such as from a power plant emission. The elimination or inhibition of the 
formation of undesirable by-products is not controlled. 
In addition, the presently employed catalytic processes for nitric oxide 
removal have utilized a fixed or fluid bed arrangement through which the 
gaseous stream is passed for conversion of nitric oxide. In these 
arrangements, two basic problems are encountered which seriously inhibit 
their commercial use. First, the pressure drop within the reactor caused 
by the catalyst bed provides substantial economic disadvantages, 
particularly in pollution control of nitric oxide-containing stack gases. 
Second, the ash and soot particles normally present in stack gases tend to 
accumulate on the surface of the catalyst which causes rapid catalyst 
deactivation. 
It would be desirable to provide a catalyst system which permits 
substantially complete conversion of nitric oxides to innocuous reaction 
products. In addition, it would be desirable to provide a means for 
utilizing such a catalytic process wherein pressure drop caused by the 
catalyst in the reactor can be minimized and wherein deposition of solid 
particles from the gas being treated to the catalyst also can be 
minimized. 
SUMMARY OF THE INVENTION 
The present invention is broadly directed to the catalytic reduction of 
nitric oxide to nitrogen with ammonia as a reductant. More particularly, 
the invention provides a high percent conversion of nitric oxide to 
nitrogen with ammonia while avoiding or minimizing the formation of 
undesirable byproducts such as nitrous oxide. The invention is directed to 
the pretreatment of a base metal catalyst selected from the group 
consisting essentially of copper, iron, chromium, nickel, molybdenum, 
cobalt, vanadium, the lanthanides and the antinides or any combinations 
thereof with a nonmetallic element selected from Group VI A of the 
periodic system. 
In a preferred embodiment, the base metal catalysts, copper, vanadium and 
iron either alone or any combination thereof are pretreated with a sulfur 
compound and/or selenium. The treated catalyst is then employed for the 
reduction of nitric oxide to nitrogen in a component system of ammonia, 
oxygen and an inert gas. 
In the catalytic reduction of nitric oxide to nitrogen in a multi-component 
system of nitric oxide, oxygen, ammonia and an inert gas several reactions 
are believed to occur. The more important reactions are: 
EQU 6NO+4NH.sub.3 .fwdarw.5N.sub.2 +6H.sub.2 O 
EQU 16NO+4NH.sub.3 .fwdarw.10N.sub.2 O+6H.sub.2 O 
EQU 3O.sub.2 +4NH.sub.3 .fwdarw.2N.sub.2 +6H.sub.2 O 
EQU 4O.sub.2 +4NH.sub.3 .fwdarw.2N.sub.2 O+6H.sub.2 O 
EQU 5O.sub.2 +4NH.sub.3 .fwdarw.4NO+6H.sub.2 O 
In a system of nitric oxide and oxygen with ammonia, to reduce the nitric 
oxide with or without sulfur dioxide added, using a noble metal catalyst, 
both nitrogen and nitrous oxide are formed. 
In a system of nitric oxide, oxygen and a controlled amount of sulfur 
dioxide using a base metal catalyst, the nitric oxide is reduced to 
nitrogen with substantially no nitrous oxide formation. Where the amount 
of sulfur dioxide in the system is unknown, either no sulfur dioxide or no 
controlled amount of sulfur dioxide, both nitrogen and nitrous oxide are 
formed. 
In the present invention, base metal catalysts are pretreated and for a 
system of nitric oxide and oxygen with ammonia using a base metal 
catalyst, substantially no nitrous oxide is formed. This pretreatment 
eliminates the necessity of controlling the amount of sulfur dioxide, if 
any, in the system to eliminate the undesirable by-product nitrous oxide 
when nitric oxide is reduced to nitrogen with ammonia using a base metal 
catalyst. 
The method of the invention broadly comprises pretreating a base metal 
catalyst from the group consisting essentially of ferric oxides, vanadium 
oxides and copper oxides by contacting the catalysts with a pretreatment 
stream comprising a vaporizable sulfur compound such as dimethyl sulfide, 
hydrogen sulfide, sulfur dioxide, carbon disulfide or elemental sulfur; or 
selenium to impregnate the catalyst. Ammonia is blended with a gaseous 
stream comprising nitric oxide and oxygen to form a blended stream which 
contacts the pretreated catalyst. The nitric oxide is reduced to nitrogen 
with substantially no nitrous oxide formation. To promote the formation of 
metal sulfides on the catalyst or the deposition of sulfur, the 
pretreatment stream preferably comprises H.sub.2 or NH.sub.3. The 
pretreatment step is preferably conducted at temperatures between about 
400.degree. F. to 900.degree. F. The time of pretreatment or exposure will 
depend upon the temperature used, and is generally between about 2 hours 
to 24 hours, preferably between 2 hours to 10 hours, the shorter duration 
at the higher temperatures. The composition of vaporizable sulfur compound 
or selenium compound in the pretreatment stream may be 0.1% to 10%, 
preferably 0.2% to 2%. The catalyst is arranged within the reactor in 
discrete segmented areas between which areas channels are provided for gas 
flow through the reactor. The size of the channels is controlled so that 
there is sufficient contact of gas and catalyst to substantially 
completely reduce the nitric oxide in the gas.

DESCRIPTION OF SPECIFIC EMBODIMENTS 
Referring to FIG. 1, a power plant, 800 mw capacity, is shown at 10, and 
emits a flue gas stream at between about 200.degree. F., preferably 
between 300.degree. F. to 800.degree. F., say for example at 700.degree. 
F. and at a rate of approximately 200.times.10.sup.6 cubic feet per hour. 
A representative composition of the flue gas is set forth below in Table 
I, it being understood that the composition will vary depending on 
operating conditions and the type of fuel being consumed. 
TABLE I 
______________________________________ 
Comp. of Flue Gas 
Comp. Vol. % lb/hr 
______________________________________ 
CO.sub.2 14.5 1.512 .times. 10.sup.6 
O.sub.2 3.0 2.275 .times. 10.sup.5 
SO.sub.2 0.2 3.039 .times. 10.sup.4 
NO.sub.x 0.075 5.329 .times. 10.sup.3 
Fly Ash 0.2 -- 
______________________________________ 
The remainder is comprised of N.sub.2 & H.sub.2 O 
The stream is discharged from the power plant 10 having the above 
composition and is introduced to a precipitator 12 where approximately 95% 
of the fly ash is removed. The stream is discharged from the precipitator 
12 less the removed fly ash, and ammonia from a source 14 is blended as a 
reductant gas with the stream to form a blended stream. This blended 
stream flows to a manifold 16 where it is introduced into a catalytic 
reactor 20 through a plurality of inlets 18a-d. The ammonia flow rate is 
dependent on the ammonia-nitric oxide ratio. For this example, Table II 
lists a range of mole ratios and the associated amount of ammonia 
available for the subsequent catalytic reaction. 
TABLE II 
______________________________________ 
NH.sub.3 /NO mole ratio 
lb NH.sub.3 /hr. 
______________________________________ 
0.7 2115.5 
0.8 2417.7 
0.9 2720.0 
1.0 3022.1 
______________________________________ 
The catalytic reactor comprises a plurality of catalytic arrangements 
22a-d. The streams introduced flow through the catalytic arrangements 
where the following reaction primarily occurs. 
EQU 6NO+4NH.sub.4 .fwdarw.5N.sub.2 +6H.sub.2 O 
The catalyst employed in this particular embodiment is 10% V.sub.2 O.sub.5 
on alumina such as available from Harshaw Chemical and designated VO301, 
which has been pretreated. The percent reduction of nitric oxide in the 
blended stream under the conditions set forth herein exceeds 80% and may 
be approximately 100% with no nitrous oxide formation. A representative 
composition discharged from the catalytic reactor 20 through outlets 24a-d 
and through manifold 26 is set forth in Table III. 
TABLE III 
______________________________________ 
Comp. of Reacter Exit Gas 
(after electrostatic precipitation) 
Comp. Vol. % 
______________________________________ 
CO.sub.2 14.5 
O.sub.2 2.9 
SO.sub.2 0.2 
NO.sub.x 0.020 
Fly Ash 0.01 
______________________________________ 
This reduced stream at between about 300.degree. F. to 800.degree. F., say 
for example 700.degree. F., is introduced into a heat exchanger 28 where 
it is cooled by incoming air to about 350.degree. F. It is then discharged 
to the stack by a conventional fan 30. 
The V.sub.2 O.sub.5 on alumina is pretreated to ensure that there is 
substantially no nitrous oxide formed, whether or not there is sulfur 
dioxide present in the stream. The catalyst is contacted with a stream of 
2% dimethyl sulfide and 2% hydrogen in helium at a temperature of between 
about 500.degree. F. and 700.degree. F., say for example 600.degree. F., 
for a period of between about 4 to 8 hours, say for example 6 hours. After 
pretreatment, the catalyst is placed on supports in a manner described 
below. 
Other base metal catalysts which may be similarly pretreated are copper, 
iron, chromium, nickel, molybdenum, cobalt, or appropriate combinations 
thereof, normally supported on a high surface area material such as 
alumina, silica alumina, or zeolites. In the pretreatment of the catalyst, 
other suitable compounds which may be used include hydrogen sulfide, 
sulfur dioxide, carbon disulfide or elemental sulfur; or selenium at 
operating conditions similar to those set forth above. 
In an alternative embodiment, the invention may be utilized for NO removal 
from the exhaust of a turbine generator employing equipment functionally 
equivalent to that shown in the drawing. A turbine generator with a 
capacity of about 20 MW discharges an exhaust of about 30.times.10.sup.5 
cubic feet per hour. A representative composition of the exhaust is set 
forth below in Table IV, it being understood that the composition will 
vary depending upon operating conditions and the type of fuel being 
consumed. 
TABLE IV 
______________________________________ 
Comp. of Exhaust Gas 
Composition Vol. Frac. lb/hr 
______________________________________ 
O.sub.2 .16 16.42 .times. 10.sup.6 
SO.sub.x 28 .times. 10.sup.-6 
57.30 
NO 114 .times. 10.sup.-6 
107.6 
CO 5 .times. 10.sup.-6 
4.397 
______________________________________ 
The stream discharged from the generator, having the above composition, is 
introduced into a catalytic reactor substantially identical to that shown 
in the drawing and described in reference to the preferred embodiment of 
the invention. A reductant gas, more particularly, ammonia, is blended 
with the exhaust gas stream and introduced through a manifold to a 
catalytic reactor at a temperature of between about 500.degree. F. to 
1100.degree. F., say for example 900.degree. F. The ammonia-nitric oxide 
molar ratio may vary between 0.7 to 1.0. The following Table V lists the 
mole ratios and required amount of ammonia necessary for the subsequent 
catalytic reaction. 
TABLE V 
______________________________________ 
NH.sub.3 /NO 
Mole Ratio lb. NH.sub.3 /hr 
______________________________________ 
0.7 42.72 
0.8 48.82 
0.9 54.93 
1.0 61.03 
______________________________________ 
The catalyst employed in this alternative embodiment is V.sub.2 O.sub.5 
supported on alumina, which is pretreated as described in the preferred 
embodiment. The percent reduction of nitric oxide under the conditions set 
forth herein can exceed 80% with substantially no nitrous oxide formation. 
A representative composition discharged from the catalytic reactor is set 
forth below in Table VI. 
TABLE VI 
______________________________________ 
Comp. of Reactor Exit Gas 
Composition Vol. Frac. 
______________________________________ 
O.sub.2 .15 
SO.sub.x 28 .times. 10.sup.-6 
NO 50 .times. 10.sup.-6 
CO 5 .times. 10.sup.-6 
______________________________________ 
The catalyst is confined within preselected areas of a reactor such that 
open channels are maintained within the reactor to permit gas flow through 
the reactor while minimizing an accompanying pressure drop within the 
reactor. The catalyst can be adhered to a solid formed substrate formed to 
attain the desired catalyst geometry such as tubes, rods, rigid screens, 
plates or the like. The material comprising the solid-formed substrate 
itself may or may not have catalytic activity for the reduction of nitric 
oxide with ammonia. Alternatively, the catalyst particles can be confined 
by an open mesh screen which compacts the particles into the desired 
geometric configuration while permitting the gas being treated to pass 
into cantact with the catalyst for reduction of nitric oxide. Generally, 
the screen is formed of metal wire and has a mesh size between about 0.002 
inch and 0.1 inch in order to provide gas-catalyst contact while retaining 
the catalyst within the screen. 
The catalyst particles can be used on the substrate or compacted either as 
the catalyst per se or supported in a matrix or other materials such as 
silica, alumina, zircon, magnesia, titania or the like. When utilized in 
compact form rather than being adhered to a formed substrate, the catalyst 
can be powdered, granular or molded such as spheres or pellets of finely 
divided particles having a particle size of about 60 mesh up to about 1/4 
inches. 
The reaction of nitric oxide and ammonia is effected on the catalyst 
surfaces whereby the reactants contact the catalyst by diffusion from the 
gas passing through the open channels in the reactor. The solid particles 
in the gas such as soot and ash are carried by the gas through the 
channels so that they are not deposited on the catalyst. To minimize solid 
particle deposition from the gas, it is preferred that the channels in the 
reactor be parallel to the overall flow of the gas. Also, parallel 
channels minimize pressure drop within the reactor. However, it is to be 
understood that the catalyst can be arranged within the reactor to form 
convoluted channels to improve gas-catalyst contact since even these 
arrangements provide substantially less solid particle deposition on the 
catalyst as compared to a fixed or fluidized bed of catalyst. In addition, 
even though a convoluted channel arrangement within the reactor effects a 
greater pressure drop within the reactor as compared to a parallel 
channel, these arrangements provide less pressure drop as compared to a 
fixed or fluidized bed of catalyst. 
The length and width of the channels are chosen in order to permit 
substantially complete reduction of nitric oxide. The gas is passed 
through the reactor at a linear velocity which assures turbulent gas flow 
so that adequate contact of gas and catalyst is obtained. Generally 
suitable linear gas velocities are within the range of between about 5 
ft/sec and 50 ft/sec, more usually between about 30 ft/sec and 50 ft/sec. 
The overall length of the channels, whether straight or convoluted is the 
adequate substantially complete reduction of nitric oxide while minimizing 
pressure drop in the reactor. Generally, the length of the channels are 
between about 2 ft and 40 ft, more usually between about 5 ft and 15 ft. 
The width of the channels generally is between about 0.1 inch and 1 inch, 
more usually between about 0.1 inch and 0.5 inch. 
The invention will now be described with reference to the accompanying 
FIGS., 2 through 9. The reactor shown in FIGS. 2 and 3 utilizes channels 
for gas which extend parallel to gas flow. The reactor 10 includes an 
inlet conduit 12 and a header 14. A plate 16 extends across the 
cross-sectional area of the reactor 10 and is secured to the reactor shell 
wall 18 of the reactor by any conventional means. The plate is provided 
with holes through which tubes 20 are fitted so that they are secured into 
the desired position. The tubes 20 are secured at their ends by two plates 
(one of which is not shown) and the reactor 10 is provided with a suitable 
outlet (not shown). The tubes 20 can be replaced by removal from the 
plates when desired and replaced with tubes containing fresh catalyst. 
As shown in FIG. 4, the tubes 20 comprise a wall 22, an adhesive layer 24 
such as commercially available Do All cement of Wonder-King Chem. Corp., 
Thermalox of the Dampney Co., or Cotronics 985 of the Cotronics Corp. and 
catalyst particles 26 adhered to the wall 22 by the adhesive 24. 
Referring to FIGS. 5 and 6, a reactor system is shown wherein the catalyst 
is coated on rods in a modular arrangement. The reactor 30 includes walls 
32 and a porous support plate 34 having a plurality of holes 36. The plate 
34 is secured to the walls 32 and provides support for the catalyst 
modules 36. The catalyst modules comprise end supporting members 38 and 
rods 40 extending between the supporting members and secured thereto. The 
rods 40 are coated with catalyst-containing particles by being adhered 
thereto in the manner described above. Incoming gas enters plenum chamber 
42 and passes through the modules 36 in either parallel or convoluted flow 
as desired and to plenum chamber 46. While in contact with the 
catalyst-coated rods 40, the nitric oxide is reduced with ammonia. After 
the catalyst on the rods 40 has become deactivated, the modules can be 
removed and replaced with new modules containing active catalyst. The 
reactor shown in FIGS. 2-6 can be formed integrally with existing stacks 
for flue gas or can be added to a stack so that the flue gas is removed 
from the stack, passed through the reactor and reintroduced into the 
stack. Furthermore, more than one reactor can be employed on a given 
stack. 
The catalyst modules shown in FIGS. 7 through 9 are alternative embodiments 
to the tubes and rods described above and can be substituted therefor if 
desired. The catalyst module 50 comprises catalyst particles 52 which are 
retained in a generally tubular or rod shape by mesh screen 54 and 
stoppers 56 and 58 which are attached to screen 54. As shown in FIGS. 8 
and 9, the particles 52 can be confined in a rod-like shape or in a 
tubular shape by screen 54 or screens 54 and 60. It is to be understood 
that the particles can be confined within a mesh screen in any shape 
desired such as a flat, plate-like structure, a circular plate, a 
spirally-wound plate or the like. 
The following examples illustrate the present invention and are not 
intended to limit the same. Examples I-III illustrate the improved 
activity of the catalysts per se. Example IV illustrates the use of the 
catalyst in the catalyst configuration of this invention. 
EXAMPLE I 
Samples of six commercially available catalysts were used as received to 
reduce nitric oxide by ammonia in the absence of sulfur dioxide, as set 
forth in Table VII below. 
TABLE VII 
______________________________________ 
Catalyst Type Manufacturer 
Identification 
______________________________________ 
10% CuO on alumina 
Harshaw CuO803 
Cr promoted iron oxide 
Girdler G3A 
Copper Chromite Girdler G13 
3% Pt on alumina Matthey Bishop 
MB30 
10% V.sub.2 O.sub.5 on alumina 
Harshaw VO301 
10% V.sub.2 O.sub.5 on silica alumina 
Harshaw VO701 
______________________________________ 
Approximately 3 grams of each catalyst was changed to individual 1/4 inch 
diameter aluminum reactors and placed in a Lindberg Heavi-Duty furnace. A 
feed mixture comprising approximately 520 ppm NH.sub.3, 600 ppm NO, 5000 
ppm O.sub.2 and the balance He was passed over these catalysts at a space 
velocity of 380 std. cc/gm-min. The results are set forth in Table VIII. 
TABLE VIII 
______________________________________ 
PPM 
Product Gas 
Composition 
Catalyst Type Temperature, .degree. F. 
NO N.sub.2 O 
______________________________________ 
3% Pt on alumina 
431 11 392 
3% Pt on alumina 457 10 405 
3% Pt on alumina 506 46 374 
3% Pt on alumina 557 79 353 
10% CuO on alumina 
430 79 119 
10% CuO on alumina 
457 81 153 
10% CuO on alumina 
507 119 252 
10% CuO on alumina 
556 139 331 
Copper chromite 430 181 108 
Copper chromite 458 149 131 
Copper chromite 507 187 194 
Copper chromite 557 258 275 
Cr promoted iron oxide 
433 175 153 
Cr promoted iron oxide 
460 203 267 
Cr promoted iron oxide 
509 219 297 
Cr promoted iron oxide 
559 220 301 
10% V.sub.2 O.sub.5 on alumina 
432 44 55 
10% V.sub.2 O.sub.5 on alumina 
459 59 86 
10% V.sub.2 O.sub.5 on alumina 
508 70 42 
10% V.sub.2 O.sub.5 on alumina 
559 222 322 
10% V.sub.2 O.sub.5 on silica alumina 
433 220 59 
10% V.sub.2 O.sub.5 on silica alumina 
460 140 106 
10% V.sub.2 O.sub.5 on silica alumina 
508 83 93 
10% V.sub.2 O.sub.5 on silica alumina 
560 197 279 
______________________________________ 
By comparison to the inlet NO level, it can be seen that substantial 
quantities of NO have been converted, but that the bulk of it has been 
converted to N.sub.2 O, an undesirable byproduct, rather than to N.sub.2, 
the desired product. 
EXAMPLE II 
The catalysts of Example I were tested in a similar fashion, except 
approximately 2000 ppm of sulfur dioxide was added to the feed mixture of 
Example I. The results obtained are set forth in Table IX. It can be seen 
from the table that the addition of sulfur dioxide to the feed of the 
non-noble metal catalysts has reduced the undesirable formation of N.sub.2 
O to zero, with N.sub.2 being the only reaction product in these cases. 
The addition of sulfur dioxide did not inhibit the formation of N.sub.2 O 
for the platinum catalyst however. 
TABLE IX 
______________________________________ 
Tempera- Concen- 
ture Downstream tration 
Catalyst Type .degree. F. 
NO N.sub.2 O 
______________________________________ 
3% Pt on alumina 
457 165 419 
3% Pt on alumina 
506 131 404 
3% Pt on alumina 
553 143 449 
10% CuO on alumina 
455 455 0 
10% CuO on alumina 
505 342 0 
10% CuO on alumina 
557 91 0 
Copper chromite 455 534 0 
Copper chromite 506 477 0 
Copper chromite 553 415 0 
Cr promoted iron oxide 
457 470 0 
Cr promoted iron oxide 
507 273 0 
Cr promoted iron oxide 
559 29 0 
10% V.sub.2 O.sub.5 on alumina 
458 63 0 
10% V.sub.2 O.sub.5 on alumina 
508 0 0 
10% V.sub.2 O.sub.5 on alumina 
560 0 0 
10% V.sub.2 O.sub.5 on silica alumina 
459 155 0 
10% V.sub.2 O.sub.5 on silica alumina 
510 19 0 
10% V.sub.2 O.sub.5 on silica alumina 
561 0 0 
______________________________________ 
EXAMPLE III 
The catalysts of Example I are exposed to a stream of 2% dimethyl sulfide 
and 2% H.sub.2 in helium for 6 hours at 600.degree. F., and were tested at 
the conditions of Example I with no sulfur dioxide added to the feed to 
the reactors. Substantially no production of N.sub.2 O is observed for the 
non-noble metal catalysts, with the only reaction product being N.sub.2 
and the downstream concentration of NO and N.sub.2 O being substantially 
the same as in Table IX. This pretreatment with dimethyl sulfide does not 
inhibit N.sub.2 O formation with the platinum catalyst. 
EXAMPLE IV 
An aluminum tube was coated on its interior surface with Harshaw VO301, 
Vanadium-alumina, catalyst pretreated by sulfur dioxide by the methods set 
forth in the table below utilizing a mixture of Saulreisen 33 cement 
manufactured by Saulreisen Cement Company, Pittsburgh, Pa., and water. The 
mixture was poured into a 3/8 inch diameter aluminum tube 12 inches long. 
The mixture was allowed to coat the inner wall with a layer about 1/16 
inch thick. The catalyst then was packed into the tube and the cement was 
allowed to dry. The loose catalyst was shaken out. 
A gas having the composition shown below was introduced into the tube at 
elevated temperatures and the extent of NO.sub.x conversion was 
determined. 
______________________________________ 
Gas Compositions and Operating Conditions 
______________________________________ 
O.sub.2 concentration 
13% 
CO.sub.2 concentration 
6% 
SO.sub.2 concentration 
50 ppm 
NO.sub.x concentration 
300-405 ppm 
H.sub.2 O concentration 
8% 
NH.sub.3 /NO mole ratio 
0.9 to 1.1 
______________________________________ 
The extent of conversion is as follows: 
TABLE X 
__________________________________________________________________________ 
1 2 3 4 5 
__________________________________________________________________________ 
Wt of Catalyst (g) 
1.17 
1.25 
&lt;0.05 2.5 1.4 
Wt of Cement (g) 
1.03 
0.25 
&lt;0.05 2.6 4.6 
Application Method 
A B C D E 
(1) Temp. 750 750 630 630 630 
(2) Space Vel..sup.1 
64.times.10.sup.3 
53.times.10.sup.3 
&gt;1.7.times.10.sup.6 
35.times.10.sup.3 
51.times.10.sup.3 
Reaction 
(3) Area Vel..sup.2 
130 93 240 242 195 
Conditions 
(4) NO.sub.in, PPM 
405 405 300 300 300 
(5) SO.sub.2in, PPM 
50 50 50 50 50 
(6) (NH.sub.3 /NO).sub.in 
1.5 1.5 1.2 1.2 1.2 
(7) % NO Conv. 
72 40 70 13 
__________________________________________________________________________ 
(1) Based on bulk density of Harshaw V0301 
(2) Based on the gas stream flow rate at STP conditions/area of uncoated 
tube. 
A, E: Fine mixture of catalyst, cement coated to tube. B: 20/30 mesh 
catalyst coated on top of cement layer. C: Coating mixture was "knocked" 
off tube leaving only a fine "adhesive owder" remaining. 
D: Smooth thick coating of a fine catalyst/cement mixture. 
EXAMPLE V 
To reduce nitric oxides with ammonia from a nitric oxide containing flue 
gas originating from a home heating furnace, a vertically placed reactor 
was used with a gas inlet at the top and a gas outlet at the bottom. The 
reactor comprised essentially two parallel screen bags, each of which was 
0.5 inch thick, 1.0 inch wide and 12.0 inches long. These bags contained 
1/8 inch pellets of vanadia on alumina and the screen had openings of 
0.0331 inch (20 mesh). The screen bags were placed inside a 2 inch Al 
pipe. 
Two tests were carried out with the catalyst in the same reactor. Some data 
are given in Table XI. 
TABLE XI 
______________________________________ 
Test I Test II 
______________________________________ 
Inlet NO.sub.x ppm 480 540 
Conversion of NO.sub.x 
31.25. /. 36.1 
Gas hourly space velocity 
std. Cft/Cft/hr 82000 64000 
Reactor Temp. .degree. F. 
700 700 
Packed Bed Comparative Test 
Inlet NO.sub.x ppm 500 
Conversion NO.sub.x 57. /. 
Space velocity hr.sup.-1 
std. conditions Cft/Cft/hr 
67000 
Flue Gas Analysis (V/V) 
CO.sub.2 7.9. /. 
O.sub.2 11.6. /. 
N.sub.2 72.5. /. 
H.sub.2 O 8.0. /. 
______________________________________ 
EXAMPLE VI 
An aluminum tube was coated on its interior surface with Harshaw VO301 
catalyst by utilizing Thermalox Protective Coating, manufactured by the 
Dampney Company, Everett, Mass. The Thermalox was poured into a 3/8 inch 
diameter aluminum tube six inches long. The Thermalox was allowed to coat 
the inner wall with a very thin layer. The Harshaw VO301 then was packed 
into the tube and the Thermalox was allowed to dry. The loose Harshaw 
VO301 was then shaken out. 
A gas having the composition shown below was introduced into the tube at 
elevated temperatures and the extent of NO.sub.x conversion was 
determined. 
TABLE XII 
______________________________________ 
O.sub.2 concentration: 13% 
CO.sub.2 concentration: 6% 
SO.sub.2 concentration: 50 ppm 
NO.sub.x concentration: 310-430 
H.sub.2 O concentration: 8% 
NH.sub.3 /NO mole ratio: 0.9-1.1 
Space Velocity, STP: 76,000 hr.sup.-1 
______________________________________ 
The extent of conversion is as follows: 
TABLE XIII 
__________________________________________________________________________ 
A B C D E F G H I J K L 
TEMP (.degree. F.) 
470 505 
530 
560 
595 
625 
650 
680 
705 
735 
770 
820 
__________________________________________________________________________ 
##STR1## 109 113 
116 
120 
124 
127 
130 
134 
137 
140 
144 
148 
NO.sub. in, (PPM) 
360 390 
390 
430 
400 
340 
320 
325 
318 
315 
310 
310 
(NH.sub.3 /NO).sub.in 
1.0 0.9 
0.9 
1.1 
1.0 
1.0 
1.1 
1.1 
1.1 
1.0 
1.0 
1.1 
NO.sub.out, (PPM) 
260 210 
180 
170 
130 
80 
60 
60 
50 
45 
30 
39 
% NO Conv. 28 46 
54 
60 
68 
76 
81 
82 
84 
86 
90 
87 
(AV).sup.2, STP 
1,510 cm/hr 
(SV).sup.1, STP 
76,000 
Catalyst at 
0.5 grams 
__________________________________________________________________________ 
.sup.1 (SV) is based on the bulk density of Harshaw VO103 1/8" pellets 
.sup.2 (AV) is defined as the gas flow rate divided by the surface area o 
the tube coating that is in contact with the flue gas 
EXAMPLE VII 
An aluminum tube was coated on its interior surface with Harshaw VO103 
catalyst by utilizing a mixture of Sauereisen #33 cement, manufactured by 
Sauereisen Cement Company, Pittsburgh, Pa., and water. The mixture, after 
first being mixed with a measured amount of catalyst, was poured into a 
3/8 inch diameter aluminum tube six inches long. A smooth channel, 1/8 
inch in diameter, was kept empty to be used as a channel. After the 
mixture was allowed to dry, loose particles were shaken from the tube. 
A gas having the composition shown below was introduced into the tube at 
elevated temperatures and the extent of NO.sub.x conversion was 
determined. 
TABLE XIV 
______________________________________ 
O.sub.2 concentration: 
13% 
CO.sub.2 concentration: 
6% 
SO.sub.2 concentration: 
50 ppm 
NO.sub.x concentration: 
340-380 
H.sub.2 O concentration: 
8% 
NH.sub.3 /NO mole ratio: 
0.9-1.1 
(S.V.), STP: 36,000 hr.sup.-1 
______________________________________ 
The extent of conversion is as follows: 
TABLE XV 
__________________________________________________________________________ 
A B C D E F G H 
TEMP (.degree. F.) 
430 510 
550 
590 
630 
680 
730 
770 
__________________________________________________________________________ 
##STR2## 48 52 
54 
56 
59 
61 
64 
66 
NO.sub.in, (PPM) 
370 370 
370 
370 
380 
370 
360 
340 
(NH.sub.3 /NO).sub.in 
0.9-1.1 
NO.sub.out, (PPM) 
250 210 
190 
170 
160 
140 
130 
130 
% NO Conv. 32 43 
49 
54 
58 
62 
64 
62 
(AV).sup.2, STP 
6,800 cm/hr 
(SV).sup.1, STP 
36,000 hr.sup.-1 
Catalyst at 
2.5 grams 
__________________________________________________________________________