SULFATE AND PARTICULATE EMISSIONS FROM AN OXIDATION CATALYST EQUIPPED ENGINE Ander Laresgoiti George S. Springer Department of Mechanical Engineering The University of Michigan, Ann Arbor, Michigan January 1976

ACKNOWLEDGMENTS This work was supported by the United States Environmental Protection Agency under Grant No. R801476-01.

ABSTRACT Particulate and sulfuric acid emissions were studied in the exhaust of a production Chevrolet V-8 engine. Tests were run without a catalyst in the exhaust system and with the engine equipped with a pelleted or a monolithic catalyst. Particles were collected at points along a specially constructed exhaust system. The weight and sulfuric acid content of the particulate matter, and the percent of fuel sulfur emitted as H2S04 were determined under different operating conditions. The effects of the following parameters were studied during the tests: a) engine speed (tests were performed at various constant speeds in the range 35-96 km h-1 and under the 7 mode Federal Test Procedure), b) catalyst temperature in the range 573-773 K, c) fuel sulfur content in the range 0.1-0.3%, d) flow rate through the catalyst, e) amount of secondary air, and f) air-fuel ratio. The results showed that the sulfuric acid and particulate emissions and the sulfur conversion depend mostly on the speed, catalyst temperature, and fuel sulfur content. Within the temperature range and secondary air range studied, the type of catalyst, the air-fuel ratio, and the amount of secondary air did not seem to affect the results significantly.

LIST OF FIGURES Figure Page 2.1 Experimental Apparatus............. 5 2.2 Schematic of Sampling Train................................. 2.3 Geometry of Probes Used............................8........ 8 2.4 Particle Collection Unit.............................. 10 2.5 Feedback Control Mechanism.............................. 12 2.6 Operational Amplifier Circuit................................. 13 4.1 Particulate Emission versus Exhaust Gas Temperature Without the Catalyst for 35 km h and 88 km h Cruise Conditions and for the 7 Mode Federal Test Frocedure..................... 21 4.2 Particulate Emission versus Exhaust Gas Temperature for 88 km h Cruise Condition, with and without Pelleted Catalyst. 23 4.3 Particulate and Sulfate Emissions and Sulfur Conversion as a Function of Speed, Temperature, and Fuel Sulfur Content for the Pelleted and Monolithic Catalysts..................... 24 4.4 Fuel Consumption versus Speed............................... 26 4.5 Particulate and Sulfate Emissions versus Fuel Sulfur Content -l for 35 km h Cruise Condition and for the 7 Mode Federal Test Procedure and 35 km h 1 (Pelleted Catalyst)........... 27 4.6 Particulate and Sulfate Emissions versus Fuel Sulfur Content for 35 km h Cruise Condition and for the 7 Mode Federal Test Procedure (Monolithic Catalyst)......................... 28 4.7 Sulfur Conversion versus Temperature with Speed as Parameter (Pelleted and Monolithic Catalysts)......................... 31

Figure Page 4.8 Effects of Flow Rate Through the Catalyst on Sulfur Conversion, H2S04 Emission and Particulate Emission (Pelleted Catalyst). 33 4.9 Effects of Flow Rate Through the Catalyst on Sulfur Conversion, H2SO4 Emission and Particulate Emission (Monolithic Catalyst)..... 34 234 4.10 Effects of Secondary Air on Sulfur Conversion, H2S04 Emission, and Particulate Emission (Pelleted Catalyst)................... 35 4.11 Effects of Secondary Air on Sulfur Conversion, H2SO4 Emission, and Particulate Emission (Monolithic Catalyst)................... 36 4.12 Effects of Air Fuel Ratio on Sulfur Conversion, H2SO4 Emission, and Particulate Emission (Monolithic Catalyst).................... 38 D.1 Plug Flow Reactor Model Used in the Calculation of SO2 Conversion. 45 D.2 Percent Conversion of SO2 into SO3 at Chemical Equilibrium........ 47 D.3 SO2 Concentrations at the Catalyst Inlet as a Function of Temperature and Fuel Sulfur Content.............................. 49 D.4 Relationship between Fractions of SO2 Converted into SO3 and SO Concentrations as a Function of Temperature................ 52 D.5 Rate Constant as a Function of Temperature for the Reaction SO2 + 1/2 2 SO3....................... 5

-1I. INTRODUCTION Gasolines contain a small amount of sulfur which, if the engine is not equipped with a catalyst, is emitted mostly in the form of sulfur dioxide. When the engine is equipped with an oxidizing catalyst some of the sulfur dioxide is converted into sulfur trioxide which, combining rapidly with water vapor in the exhaust, is emitted in the form of sulfuric acid. Thus, while oxidation catalysts reduce gaseous emissions they give rise to the emission of sulfuric acid [1-9]. In addition, the installation of oxidation catalysts in automobile exhaust systems cause an increase in the amount of particulate matter emitted [2,3,4,5]. Owing to the possible problems created by the increased sulfuric acid and particulate emissions from catalyst equipped engines, it would be desirable to understand the mechanisms and parameters which control such emissions, and to determine the amounts of sulfuric acid and particulates emitted. In recent years several investigations have been addressed to this problem. Nevertheless many aspects of the problem remain unresolved. Sulfuric acid and particulate emissions from actual engines operating at steady and cyclic speeds were reported in refs. [2-7]. These studies do not indicate fully the important role of the catalyst temperature because this temperature was either not reported [2,5], or was varied only over a limited range (793-939 K) [3-7]. Sulfate emissions in simulated catalyst-exhaust systems were studied by Mikkor et al [8]andHammerle and Mikkor [9]. The storage of sulfates in catalysts was investigatedby Hammerle-.and Mikkor [9]. Results are not yet available to indicate the full effects of engine variables, fuel sulfur content, and catalyst temperature on the sulfuric acid and particulate emissions from an actual spark ignition engine equipped with

-2oxidation catalysts. The overall objective of this investigation was, therefore, to study the influence of these parameters on emissions from a Chevrolet V-8 engine operating on a test stand' dynamometer. Specifically, the amount of particulate matter and sulfuric acid emitted and the percent of the fuel sulfur emitted as sulfuric acid (sulfur conversion) were measured as a function of a) engine speed (both steady and cyclic), b) fuel sulfur content, c) catalyst temperature, d) flow rate through the catalyst, e) amount of secondary air, and f) air fuel ratio. The tests were performed with both a pelleted and a monolithic oxidation catalyst.

-3II. EXPERIMENTAL APPARATUS The apparatus employed in this study wasessentially the same as the one used by Sampson and Springer [10] and by Ganley and Springer [11]. Therefore, only a brief summary will be given to indicate the changes made and to facilitate the reading of the report. The apparatus consisted of the engine, the simulated exhaust system, and the sampling train. These components are described in the following sections. 2.1 Engine and Fuel The engine used was a 350 CID 250 HP Chevrolet V-8 production engine. The engine specifications are given in Appendix A. The engine was mounted on a Midwest Dynamatic eddy current dynamometer test stand located in a test cell in the Automotive Engineering Laboratory at The University of Michigan. The engine and dynamometer were instrumented to monitor and control coolant temperature, oil temperature and pressure, manifold vacuum, exhaust pressure, and engine speed and load. The air flow rate to the engine was measured by a rounded approach air cart manufactured by General Motors Corporation, The fuel flow rate was measured with a Burette. Tests were conducted using Indolene HO 0 (clear) fuel. Di-T-Butyl-Disulfide was added to adjust the sulfur content of the fuel to the desired value. The physical and chemical properties of the fuel are given in Appendix B. The engine was lubricated with Valvoline 10 W 40 oil, which is typical of commercially available motor oils. The oil, oil filter, and PCV valve were changed at 40 hour intervals.

-42.2 Simulated Exhaust System Tests were first conducted under cyclic conditions without the catalysts. Then, in turn a pelleted and a monolithic catalytic reactor were installed in the exhaust system and tests were performed with each catalyst under steady and cyclic operating conditions. In the following paragraphs the basic exhaust system without the reactor is first described. The changes made to install the reactors are outlined subsequently. The exhaust system, connected to the engine, consisted of the standard exhaust manifolds and cross —over pipe, a surge tank, a 4.27 m long 50.8 mm diameter pipe, and a sharp edged orifice (Fig. 2.1). The surge tank was a 304 mm diameter 609 mm long steel cylinder, insulated with a wrapping of Kaowool. The surge tank was added to reduce the pressure and flow fluctuations in the exhaust (Sampson and Springer [10]). The simulated exhaust system consisted of three 609 mm long black pipe sections, a 1800 bend followed by 3 additional 609 mm sections of black iron pipe. There were six holes in each of the sections. Three 1/8 NPT holes were located along the top and three 1/4 NPT holes along the sides to allow for the installation of thermocouples and sampling probes, respectively. All holes were fitted with plugs when not in use. A 22.2 mm sharp edged orifice (Orifice A), made to ASME specifications, was placed at the end of the simulated exhaust system. The purpose of this orifice was to measure the exhaust flow rates during cyclic sampling, as described in the next section.

AIR PUMP ORIFICE D VA E SECONDARY AIR.= FLEXIBLE TUBING EXHAUST MANI FOLDS oN,,,,,/INSULATION SURGE TANK CHEVROLET V-8 ENGINE C ATALYTIC REACTOR SIMULATE 1 t EXHAUST SYSTEM ORIFICE A TO EXHAUST VENT.Fig. 2.. Cx,~erimental apparatus. Circles represent thermocouple and sampl:in locations.

-62.3 Catalysts Emissions with two catalysts were investigated. One was a pelleted catalyst supplied by General Motors Corporation, the other was a monolithic catalyst supplied by Engelhard Industries,(Appendix A). The catalytic reactors were installed in place of the first segment of the simulated exhaust system. No other modifications of the exhaust system were necessary. After the tests with the pelleted catalytic reactor were completed the reactor was removed and the monolithic catalytic reactor was installed in its place. The monolithic reactor was designed to process only half the volume of the exhaust gas. Therefore, for the monolithic reactor only four of the eight cylinders (the right bank of cylinders) were connected to the simulated exhaust. The other four cylinders were connected directly to the test cell exhaust vent. For both catalysts secondary air was injected into the simulated exhaust (before the surge tank) by an air pump driven by a V belt from the crankshaft pulley. The amount of secondary air was controlled by a valve and was measured by an 18 mm sharp edged orifice (Orifice D, Fig. 2.1) made to ASME specifications. 2.4 Sampling Train The sampling train consisted of a probe, a particle collection unit, a heat exchanger, a flow control mechanism, and two vacuum pumps (Fig. 2.2). Each of these components is described below. Two different size probes were utilized in the course of this study. They were constructed of 316 stainless steel tubing and had the dimensions given in Fig. 2.3. The larger probes were used when the sample was undiluted.

-7EXHAUST PIPE TO EXHAUST FROM ENGINE VEN VENT PROBE FLOW CONTROL MECHAN ISM PARTICLE COLLECTION UNIT BLEED VALVE I VALVE...TO EXHAUST VENT VACUUM PUMPS Fig. 2.2.,;aumplinpg train.

B R -tSv PROBE A B C D R I 3.98 6.35 114.2 160.3 24.6 II 2.66 4.99 51.5 56. 1 11.5 All Dimensions inmm Material: 316 Stainless Steel i?;. 2.:~;. (;eoC)et ry )['' r) I!rI); es;icl i 1r ilc sttluly.

-9The smaller ones were used when the sample was diluted with ambient air (during cyclic sampling the larger probes were used in both cases). The probes were located in the center of the exhaust pipe facing the direction of the flow. The particle collection unit consisted of a single filter (Fig. 2.4). The matter collected on the filter was analyzed to determine particulate and H2S04 emission. The filters used were Gelman 47 mm diameter type A glass fiber placed in a modified Gelman 2220 filter holder. The entire collection unit was surrounded with beaded heaters and enclosed in a 25 mm thick wrapping of kaowool held in a sheet metal shell. The current to the heaters was controlled by voltage controllers. The temperature of the gas sample was measured with chromel-alumel thermocouples inserted into the gas stream on both sides of the filter holders. The exhaust gases could be diluted with ambient air to lower the dew point of the gas mixture and thus avoid condensation of water in the filter. The flow rate of the dilution air was controlled by the mechanism described below. The flow rate through the probe and the amount of dilution air must be carefully regulated through the tests. The flow rate through the probe must be adjusted to the proper value for isokinetic sampling (Ganley and Springer [11]). The dilution air was kept constant at an 8:1 dilution ratio. At steady operating speeds flow rates of the dilution air and the total sample were measured by wet test meters installed in the system and the flow rates were set appropriately. Under cyclic operating conditions the flow rates through the probe and the dilution system were modified and adjusted

-1 -- FROM PROBE INSULATION.DILUTION AIR - Eu~ /HEATERS AIR CONTROL MECHAN ISM FILTER TO WET TEST METER Tic:,. 2.4. Schematic of the collection unit. Open circles represent, thermocouple locations.

-11continuously. To accomplish this a special flow control system was designed (Fig. 2.5). The flow rate through the probe was regulated as follows. A standard 1. 3 mm diameter sharp edged orifice (Orifice B) was installed in the sampling line (Fig. 2.5). The pressure drop across this orifice-was measured by a Ptran 0 - 0,1 psi differential pressure sensitive transistor immersed in a silicon oil bath to minimize temperature fluctuations. The pressure drop across the orifice in the exhaust system (Orifice A) was measured by a Rahm PT (C) 71 potentiometer type differential pressure transducer.. The signals from the two transducers were compared on an Analog Devices 118A Operational Amplifier. "A schematic of the amplifier circuit is given in Fig. 2.6. The difference in the two signals was amplified by an AST/SERVO Systems Model A-176 DC error signal servoamplifier (Fig. 2.6) and fed to a Kollsman 8090160650, 115 volt 2 phase, 2 pole motor generator. This motor generator was connected to a stainless steel Whitey 1RS4 type valve through a 50:1 ratio link "high-precision" gear box. The flow rate through the probe was regulated by the valve. The amount of dilution air was controlled by a similar control system (Fig. 2.5). The orifice in the dilution air line was 5.6 mm in diameter. The pressure transducer usedwasa Bourns Model 503 differential pressure transducer and the valve used to control the flow was a Whitey lRS8 brass valve. The voltage necessary for the pressure transducers was provided by a Kepko Model CK18-3 and a Thornton 201D type DC power supply while the servoamplifier and the motor generator were connected to the 117 volt AC line. The orifices were calibrated under steady state conditions. The orifice in the exhaust system (Orifice A) was calibrated with a rounded approach air cart manufactured by General Motors Corporation. The orifices in the sampling line (Orifice B) and in the dilution air line (Orifice C) were calibrated using the wet test meters.

PROBE ORIFICE A EXHAUST E [PRESSURE ~PRESSURE TRANSDUCER TRANSDUCER r/. OPERATIONAL ORIFICE B- r | AMPLIFIER CIRCUIT MOTOR GEAR GENERATOR | BOX VA~LVE SERVO-'~~~VALVE(~PLIFIER |VALVE ORIFICE C LVENT — AA TO EXHAUSTI RO N MOTOR PARTICLE GENERATOR COLLECTION OPERATIONAL - AMPLIFIER CIRCUIT Fig.?.S. Schematic of the automatic control syster~.

BIAS VOLTAGE 10 kQ +15 VOLTS. I0 k, O- IOVOLTS SERVOSAMPLING PROBE 10 k IER PRESSURE ~ - J OPERATIONAL AMPLIFI ER TRANSDUCER VOLTAGE _ AMPLIFIER BIAS VOLTAGE +15 VOLTS _P EXHAUST PRESSURE - TRANSDUCER VOLTAGE Fig. 2.6. Operational amplifier circuit. Circles with P represent potentiometers.

-14Two high vacuum pumps were used to provide the flow through the sampling train.

- 15III. EXPERIMENTAL PROCEDURE All tests were performed following the same sequence of steps: a) the engine and exhaust system were conditioned, b) particulate samples were collected, c) the weight of the collected particles was measured, and d) the samples were analyzed for sulfate content. 3.1 Test Conditions A summary of the test conditions under which the samples were taken is given in Table (3.1). In test series I and II samples were collected at different positions along the simulated exhaust system. In all other tests the samples were collected at one position 400 mm downstream of the catalytic reactor. Tests III through XX were performed first with the pelleted reactor. The tests were then repeated with the monolithic catalytic reactor. The last column in the table describes the various variables studied during each test. 3.2 Engine and Exhaust Conditioning Before taking any data the engine and exhaust system were operated at the test conditions to allow the emissions to stabilize. Prior to the present study the engine had been operating with Indolene HO 0 (clear) fuel. Therefore, before Test I the engine was conditioned for six hours only. The results obtained in these tests did not change with time indicating that the six hours conditioning time was sufficient. When a different catalytic reactor was installed, the system was conditioned the equivalent of 2500 km at 88 km h-l with fuel containing 0.1% sulfur (in addition, the pelleted catalyst had been previously conditioned the equivalent of 8,000 km at 88 km h-1 with fuel containing 0.017% sulfur). Before the start of each new series of tests, the engine and the exhaust system were conditioned for three hours.

Table 3.1 Test Conditions Test Catalyst Engine Engine A/F Initial Road Test Series Speed (RPM) Load BHP Ratio Spark Advance Speed Equivalent I None - - 4~ Cyclic II Pelleted 1800 24.5 14.6 40 88 kni h1 H2SO4 Condensation Cruise III Pelleted & 1800 24.5 15.0 40 88 km h1l Secondary Air Monolithic Cruise and 3pace Velocity IV Pelleted & 1800 24.5 15.0 40 88 km h-1 Fuel Sulfur Monolithic Cruise Content V Pelleted & 1800 24.5 15.0 -8' 88 km h-1 Spark Retard Monolithic Cruise VI Pelleted & 1800 24.5 13.5 40 88 km h A/F Ratio Monolithic Cruise VII Pelleted & 1800 24.5 16.7 40 88 km h-1 A/F Ratio Monolithic Cruise -1 VIII Pelleted & 2000 30.0 15.0 4~ 96 km h Secondary Air Monolithic Cruise IX Pelleted & 2000 30.0 15.0 4~ 96 km h Fuel Sulfur Monolithic Cruise Content X Pelleted & 2000 30.0 17.0 40 96 km h-1 A/F Ratio Monolithic Cruise XI Pelleted & 2000 30.0 15.0 4~ 96 km h-1 Space Velocity Monolithic Cruise XII Pelleted & 1300 11.7 15.0 40 64 km h Secondary Air Monolithic Cruise

Test Catalyst Engine Engine A/F Initial Road Test Series Speed (RPM) Load BHP Ratio Spark Advance Speed Equivalent XIII Pelleted & 1300 11.7 15.0 40 64 k-m h Fuel Sulfur Monolithic Cruise Content XIV Pelleted & 1300 11.7 13.7 40 64 km h- A/F Ratio Monolithic Cruise XV Pelleted & 1300 11.7 16.5 40 64 kim h1 A/F Ratio Monolithic Cruise XVI Pelleted & 1300 11.7 15.0 40 64 km Space Velocity Monolithic Cruise XVII Pelleted & 750 3.9 13.0 40 35 km h1 Secondary Air Monolithic Cruise XVIII Pelleted & 750 3.9 13.0 40 35 km h1 Fuel Sulfur Monolithic Cruise Content XIX Pelleted & 750 3.9 13.0 40 35 km h-1 Space Velocity Monolithic Cruise XX Pelleted - FTP Fuel Sulfur Monolithic Content

-183.3 Test Procedure A typical test, was performed in the following manner. The probe was placed in the location under study, the filters were weighed, placed in the collection unit, and the system was warmed up. For steady state sampling the engine was run at fast idle for 5 minutes. Then the speed was increased to the operating speed and the torque was increased until the desired load was reached. The engine was then run for about 80 minutes to allow for temperatures and particulate emissions to stabilize. This is particularly important for tests with catalytic reactors because the reactors tend to store H2S04 while cold and release it when they warm up [~]. For cyclic tests the system was warmed up through 10 cycles before sampling. After the engine warmed up, the temperature of the collection unit was adjusted to the appropriate value and sampling started.. When the sampling was not diluted its temperature was adjusted to the same value as that of the exhaust gas at the location of the probe. When the sample was diluted the temperature of the collection unit was kept at a temperature which was lower than the temperature of the exhaust at the location of the probe. During steady operation (test II through XIX) the temperatures of the sample and the catalyst were recorded every five minutes. During cyclic operation the temperatures were measured at the end of each cycle. It is noted that the catalyst temperature was measured with a thermocouple inserted into the reactor. In addition to these temperatures the following parameters were recorded throughout each test: a) temperature and pressure of the gas through the wet test meters, b) the engine speed and load, c) fuel flow rate d) air flow rate, e) manifold vacuum, f) atmospheric pressure, and g) room temperature.

-19After each test the filters were placed for 24 hours in an airtight container containing CaC12 as dessicant. After 24 hours the filters were weighed and prepared for chemical analysis. The weight of the filter indicated the amount of particulates in the exhaust. The chemical analysis provided the sulfate content of the particulate sample. 3.4 Measurement of Sulfuric Acid Content The surfuric acid content of the collected particulate sample was determined by the Barium-Thorin Titrimetric procedure [12,13]. The filter was placed in a covered Pyrex flask containing 50 ml of deionized water. After 12 hours, 25 ml of the liquid were taken from the flask, and placed in a centrifuge for 15 minutes to separate out filter fibers. Following the centrifuging 15 ml of the liquid were passed through a cation exchange. resin to remove all positive ion interferences. This liquid was then diluted with deionized water to give a total volume of 25 ml. Ten ml of this solution were mixed with 40 ml of isopropanol. Two drops of thorin indicator solution were added to this liquid. The liquid sample thus prepared was titrated with a 0.001 molar solution of Ba(C104)2 diluted in a mixture containing 20% deionized water and 80% isopropanol. The change in color of the liquid was monitored with a Baush and Lomb Spectronic 20 calorimeter by measuring the change in absorbance of the solution at a wavelength of 520 nm. The amount of titrant added up to the end of the titration was proportional to the H2S04 concentration in the sample. The titrant solution was calibrated against a solution of H2S04 of "known" concentration. This "known" solution was calibrated by titrating it with a NaHC03 solution using a glass electrode ph meter to monitor the titration.

-20IV. RESULTS The major objective of this investigation was to evaluate the parameters which affect the sulfate and particulate emissions from spark ignition engines equipped either with a monolithic or with a pelleted catalyst. Particular attention was focused on the effects of engine speed, catalyst temperature, fuel sulfur content, air fuel ratio, and amount of secondary air on the amount of particulate matter emitted, on the amount of sulfuric acid emitted, and on the sulfur conversion rate. It is important to note that in the following tests the effects of the various parameters were separated. This was accomplished by varying one parameter at a time. For example the temperatures of the catalysts were regulated by heating tapes and were thus unaffected by the engine speed or the secondary air. This must be borne in mind when evaluating the data and when comparing them to the results in the previous tests where generally several parameters were varied simultaneously. 4.1 Particulate Emission In order to establish the proper sampling conditions for the catalyst equipped engine, the particulate emission from the engine was measured both with and without the catalysts. For the engine operating on unleaded fuel and without the catalyst, particulate emission as a function of exhaust temperature is shown in Fig. 4.1 for 35 and 88 km h-1 cruise conditions (steady speeds) and for the 7 mode Federal Test Procedure. For exhaust gas temperatures above 390 K the particulate emission remains constant. Particulates collected above this temperature are mostly carbon formed in the combustion chamber due to the dehydrogenation of hydrocarbons [10,11,14]. Below 390 K there is a large increase in particulate emission due mostly to condensation of high molecular weight organic compounds present in the exhaust gas [15-18].

-21EE tr2 ~II I ir z o - 0.01 300 400 500 600 EXHAUST GAS TEMPERATURE K i.]'1. Parti culate emi ssion versus exhaust gas temperature during 7 Mode Federal Test Procedure, and 35 km h and 88 km -1 cruise condlitions. Indolene I ()0 fuel ( - - -) -!it to data.

-22It is noted that during the 7 mode Federal Test Procedure approximately twice the amount (by weight) of particulates are emitted than at 35 km h steady speed (35 km h corresponds to the average speed of the cycle). A similar trend was observed by Ter Haar et al [19]. Particulate emission as a function of exhaust gas temperature was also measured with fuel containing 0.017% sulfur (Fig. 4.2). These tests were performed both with and without the catalyst with the objective of determining the exhaust gas temperature at which most of the sulfuric acid condensed. Above ~ 390 K the results with and without the catalyst agree closely, suggesting that most particles collected are carbon directly emitted from the combustion chamber [10,11,14]. Deposition in the catalyst may account for the small difference in the results. There is a sharp increase in the amount of particulate matter emitted below 390 K. In the absence of the catalyst this increase is due to condensation of heavy hydrocarbons [15-18]. For the catalyst equipped engine the increase is most likely due to condensation of sul'furic acid. Below 350 K the amount of particulate matter emitted remained constant when using a catalyst, indicating that most of the sulfuric acid condensed out of the gas stream. Therefore, in all subsequent tests the collection unit was kept in the 305-315 K temperature range by diluting the sample with ambient air (dilution ratio 8:1). These temperatures are appropriate also when fuels with higher sulfur content (i.e. sulfur content higher than 0.017%) are used since in this case the condensation process is completed at even higher temperatures. For steady engine speeds the effects of speed, fuel sulfur content and catalyst temperature on the amount of particulate matter emitted are shown in Fig. 4.3. The lines shown in this figure were calculated by the following expression

-230.02 Et - \ No Coto/yst C r (I) W 0.01 - e With Pe//eted Catolyst I I I I 300 400 500 600 EXHAUST GAS TEMPERATURE K TFig. 4.2. p'articulate emission with and withollt a nelleted catalyst. 88 km h-1 cruise condition. Catalyst temperature 755K Indolene 110 0 fuel with O.017~, sulfur content. ( ) fit to data.

~ psa~ noO asaGM sGauI pTIoS ~ Vep 4SXI(Te 3 tivEIOUL * 0ep;sAICeD p4aGlla.I 0 (g() %S,)'%SZ = lTe ssaOxaG'O0SI = l/V'flanJ 0 OH aUaOTPUI'uoTssPUG sa~enz -e~d pue UOTSSTUla POSZH'uoTlsaAuo~ anjins uo;ua; -uoo anj ns Ianj puie' an:eaodua 3asXie;'pads jo s;Oa H jj* g 1-4 w Q033dS,- wM 0133dS 1-4 WM 033dS 021 001 08 09 Ob OZ 0 Z0 001 08 09 Ot 0 0 0ZI001 08 09 Ot OZ 0 SEE IZo I Eo zo t: ~ ~t"o-o -- I -b' V... zY \:ainloaduwl m 9'0 - 9,0 ISA//o0 C)0 m'90 9*0 8do 90,~ Uzz ~~~~~~~~~~~o 1.(O~~~~~~~~n. I I I 1 I i I,. 1 1-4 WI 33dS Or 33dS 1- WM d 14 WMI 03dS OZI 001 08 09 Ot O 0 001 08 09 07 OZ 0 001 08 09 0 03Z O _,,z9 I I -~19 ~/ O - -I~O -~ -'0 - - 90' -'0 |Im I-sE, \ %Eos I 1 \'~ I L xso s z -4, aW) 33dS,14 wM 033dS. 1,_ I w Q33dS OZI 00108 09 Ot OZ O 0 O 0108 09 Ot OZ 0O 0ZI00108 09 Ot OZ O0 0o ~ 0 o 0l o -'1 osI, ol, ots: 0.0 09800 019 "~1.~i~O.I~ ~ I I',~'~'Z9~ ~,~ t01~~~~~V ~'. ~~10. -'lZ -

-25en e~z~ rss ~/ onvi /no/ l~/~~Jo18~ I(4.1) where A is a constant which is obtained by matching eq. (4.1) to the data. The data give A in the 2.2-2.8 range. The lines in Fig. 4.3 were computed using the average value of A=2.4. C is the percent conversion of SO2 into S03 (see top of Fig. 4.3), F is the fuel consumption in g km1 (Fig. 4.4 and S is the fuel sulfur content (percent sulfur per weight in the fuel). Particulate emission under cyclic operation (7 mode Federal Test Procedure) are shown in Figs. 4.5 and 4.6. In these figures the ranges of particulate emissions at the steady speed corresponding to the average speed of the cycle (35 km h 1) are also shown. For the 7 mode Federal Test Procedure the amount of particulate matter emitted increased linearly with the fuel sulfur content. A similar increase in particulate matter with fuel sulfur content was observed with the pelleted catalyst'. With the monolithic catalyst at the steady 35 km h-1 speed the particulate emission seems to be insensitive to the fuel sulfur content. This can be explained by noting that the rate of reaction at which the SO2 to SO3 conversion occurs depends on the concentration of SO2 in the exhaust gas at the inlet to the catalyst and on the catalyst temperature [20]. At low SO2 concentrations and at high temperatures the mechanism limiting the formation of SO3 is the adsorption of S02 by the catalyst. Under these conditions the reaction rate varies nearly linearly with the SO2 concentration. At high SO2 concentrations or low temperatures the rate of reaction becomes constant. In this region the reaction is controlled by desorption of SO2 from the catalyst. In between the adsorption and desorption controlled regions the reaction is governed mostly by chemical reaction. The amount of particulate matter emitted is proportional

-2 6 - -26120 100 o 80 z D. Cf) 08 40 --'20 20 40 60 80 100 SPEED km h-l -;Figi:.,1.. Fulel consUmPtion vcr;s so, odtl ( ---. ) F it to (l.;ta.

.....I' I PELLETED 0.01 0.016 0.01 7mode FTP z oz~ 593-648K E o.= 0.008~~~~ 0.012C~ ~ ~kl 7mode FTP o....r o 593-648Kk ~~w -In~~~~ ~~n 0.006 w o r 0.008 _1 W"73 o.. 000.Q004 0 0.00-4423K 0.002 35 kroh-/ -________ 35 km h'/ 0 0.1 0.2 0.3 0,1 0.2. FUEL S CONTENT % FUEL S CONTENT % * ~ tiuate _nt e1S~ n;~i~sduji'odte F-cdeYl.i cst!'roccdii~ce;i~ km5 Ini 1- crui se': r,:rticul.a-te and ITS".;'1 emissionn' durin:o! t dc Fe7 c e!: 3. cru..s con'!i. tion.'Illcte'd catal..'-st. Tenperatures i.ndic'ated corresnoni t> cat' I'lst t.;cntlret. Indoleno II0 0c fuel.

I I MONOL/THI/C 0.01 E 0.016 7mode FTP T z 453-473K E 0.008 0. X0 u) 0.0.12 UI 1:~r~~ t~ 0.006 7modeTP FP ~~~w U)~~n 453-473K 0.008 o. oo-398K,,,,.1'o-'- ~ 0 QI 0.2 0.3 0 0.1 0.2 0.3 FUEL S CONTENT % FUEL S CONTENT % ig. 4.6. Particulate and H2S34 emissions during 7,ode Federal Test Procedure and 35 km h-l cruise condition.,lonolithic catalyst. Temperatures indicated correspond to catalyst temperature Indolene I10 0 fuel.

-29to the sulfuric acid (i.e. SO3 formed) in the exhaust (see next section), Thus, the fact that the amount of particulate matter emitted remained constant indicates that the reactions in the catalyst are in the desorption controlled region (high S02 concentration, low catalyst temperature) where the SO2 concentration at the catalyst inlet does not affect the reaction. Since the amount of SO2 is proportional to the fuel sulfur content, in this region the fuel sulfur content does not influence the results significantly. At higher catalyst temperatures the reactions are not in the desorption region and the amount of particulates emitted depends on the fuel sulfur content. 4.2 Sulfuric Acid Emission The effects of speed, fuel sulfur content, and catalyst temperature on the amount of sulfuric acid emitted are shown in Fig. 4.3. There is a distinct similarity between the amounts of sulfuric acid and particulate matter emitted, because the particulates are composed mostly of sulfuric acid and water. The solid lines in Fig. 4.3 were calculated by the expression ~/~slovZ -- ~ I o Hzvv2 r'Ssion o _ )*-(_iS q ) wt s i (4.2) The parameters C, F and S were defined in conjunction with eq. (4.1). Note that the sulfuric acid emission has a minimum at about 90 km h. As will be shown in the next section the sulfur conversion decreases continuously with speed. However, the fuel consumption decreases and then increases with speed (Fig. 4.4) giving rise to the minimum in the sulfuric acid emissions. The sulfuric acid emission for the 7 mode Federal Test Procedure is shown in Fig. 4.5 and 4.6. As expected the trend in the results is the same as for the particulate emission because of the relationship between the amounts of sulfuric acid and particulate matter emitted.

-304.3 Sulfur Conversion The sulfur conversion (percent weight of sulfur in fuel converted to sulfuric acid) as a function of speed, fuel sulfur content, and catalyst temperature are shown in Fig. 4.3. The data points are from the measurements. The lines were computed according to the procedure described in Appendix D. Note that for all the temperatures tested the sulfur conversion increases with temperature indicating that the catalytic reaction is kinetically limited (as opposed to being limited by chemical equilibrium) [20]. The results, crossplotted using temperature as the abcissa and speed as the variable parameter, are shown in Fig. 4.7. The conversions were extrapolated to higher temperatures by calculating the reaction rate constants for higher temperatures using Arrhenius equation (see Appendix D). The curves on the left side of the peaks correspond to reactions in the kinetically limited region, the ones on the right correspond to reactions in the regions limited by chemical equilibrium. The data of Creswick et al [3], Trayser et al [4], and Holt et al [7] obtained with a pelleted and monolithic catalyst are also included in Fig. 4.7. The data reported by these investigators were shifted 70 K to the right (as suggested by Dr. W.R. Pierson) to account for the fact that these investigators measured the catalyst temperature at the catalyst exit and not inside the catalyst. Mikkor et al [8] also measured sulfur conversion. Their data are not included here because instead of an engine they used a simulated exhaust system. Nevertheless, their results show a trend similar to the curves in Fig. 4.7. Figure 4.3 indicates that an increase in speed produces a decrease in sulfur conversion. The reason for this is that at higher speeds the flow rate through the catalyst increases decreasing the residence time inside the catalyst.

80 80o0resen tudy om;Tioyser etol[ (/975) A Cres wick etoll (/975) V) Cw VYHO//ef1 97(975) z 60 () 40. 64 km h ~ gwm 35kmh'fi 96 km h I 20 U) 0 550 600 700 800 900 1000 CATALYST TEMPERATURE K Fig. 4.7. Sulfur conversion as a function of temperature and speed. Indolene HO 0 fuel with 0.1% sulfur content. A/F 15.0. Excess air 25% (Pvr5% 02). Open and closed symbols represent pelleted and monolithic catalyst data, respectivty. Solid lines were calculated (Appendix D).

-32Note that at catalyst temperatures above t 900 K the reactions are in the chemical equilibrium region where the reactions are not affected by the flow rate, as observed by Holt et al [7]. Figure.4.3 also shows the effect of fuel sulfur content on the sulfur conversion. The conversion is insensitive to the fuel sulfur content above 573 K indicating that the catalytic oxidation of S02 is limited by adsorption of SO3 by the catalyst (see Section 4.1). Below' 573 K the conversion decreases with fuel sulfur content indicating that the limiting mechanism is desorption of SO3 from the catalyst. 4.4 Space Velocity The effects of space velocity (i.e. the velocity of the exhaust gas through the catalyst) on particulate and sulfuric acid emissions and on the sulfur conversion are shown in Figs. 4.8 and 4.9. In general, a reduction in space velocity and a corresponding increase in residence time result in an increase of sulfuric acid conversion and hence an increase in the amounts of sulfuric acid and particulate matter emitted. 4.5 Secondary Air and Air Fuel Ratio Sulfur conversion, sulfuric acid, and particulate emissions as a function of secondary air injected into the exhaust before the catalyst are given in Figs. 4.10 and 4.11. The amount of secondary air does not seem to affect the results suggesting that there is sufficient oxygen for the reaction to be completed. These results tend to agree with those reported by Mikkor et al [8]. At smaller amounts of secondary air, the secondary air might affect the results but the amounts needed to observe these effects could not be achieved in the present tests.

60 PELLETE D',0.14 50) E bi]tal Exhaust 0.12:0.3 TE 0.12 "' 40- O. Total Exhoust 0.i - I-W1:0.08 0.2,3 W 13~~~~~~~~~~~~~.whi hi~~~~W 0.06 V.~~~~~~~~~u W 20 U. 0.04- 0.1 to ~~~~~~~~~~~~~~~~~~'~ U) 01020 _z 10 II 002 IIM ~ ~ ~. m~ __ ____ 35km h' 64 km h'' 88km h' 96 km h' 35km h'-.64 km h' 88 km h' 96km h'- 35 km.h'1 64 kh'm h-'88 9km hm' 473K 613K 673K 723K 473K 613 K 673 K 723 K 473 K 613K 673 K 723K Fiv. 4..8. Effects of flow rate throug~h a pelleted catalyst on sul'fur convers.io n, II2S04 emission, and particulate emission..nen symbols are for the entire exhaust nassing. throu'h the catalyst S!laded symbols are.fo-r reduced flow rates Indolene 1!O 0 fuel with 0.1%' sulfur content. 25% excess air (i 5% 02). A/F = 15.0. Temperatures given are catalyst temperatures. 2.

60 MONOLIJHC 0.14 o0 )E M 50 - zrJ QTot/&/ l eousf TE 0.12 COQ3 M z 0 W 0 U) (0 0.08 w QZ'-'30 V 4 W w LLV 0.06 IL. 10 0 U) ffll0.02 35 kmhI' 64 kmhWI 88 kmh W 96 km hW 35 km h'64kmWh'I88 kmWh'I 96 km h`t_ 35 kmhW'64 km-h 8mh" 96 kmht' 398 K 573 K 623 K 673 K 398K 573K 623 K 673K 398 K 573 K 623K 673K F'ig. 4.9. Effects of flow rate through a monolithic catalyst on sulfur conversion, 112S04 emission, and particulate emission. Open symbols are for the entire exhaust passing through the catalyst. Shaded symbols are for reduced flow rates. Indolene 110 0 fuel with 0.1% sulfur content, 25% excess air (* 5% 02) A/F = 15.0. Temperatures given are catalyst temperatures.

-35 qom I I (n PELLETED Speed Catalyst Temp | ~o | a 96kmh' 773K,3 30 pto; o f | — o88 kmh' 723 K o64 kmhI 658 K.j 20 o35 kmh' 427 K LL Z~~~- le-Fit to Data O 10 20 30 0.14 _________ E 0.12 CA$ z E 0~4 1 a 0.1 ) < ^ —6, k -',.,. -- 20 3 10C k h ll ) i 0.o _ 0.04 c I[( (Fe ih01%slu otn~. I lo 20 30 10 20 30 EXCESS AR OVER STO CH I OMETR I I~~~~~~~~~~~i~~~~~.g.~,.I~ctofscnzr jro slu ovrin IL,~ msin ~~nJ Ic~~~~~~rticulat e cr~~~~~~~~~~~~:ission For a!iellctcct cata~~~~~~~~~~~~~~~~~~~~~~~~~~yst. Indolene~~~~~~~~;.

w.' ~~~~~~~W ~MONOLITHIC I — Speed Caotolyst Temp A/F w u) A96km h1 623 K 13.5._______ ~88 km h1 573 K 14.0 LL ~ 64 km h' 445K 15. 1 2 I * 35 km h' 398K 12.0 10 20 30 —'Fit to.Doto a 0.06 z cI)-O ~ ~ ~~~w G,E LU0 *l ~0.I'~u o 0.02 0 10 20 30 0 10 20. 3 EXCESS AIR OVER STOICHIOMETRIC % Fig. 4.11. Effect of secondary air on sulfur conversion, H2S04 emission, and particulate emission for a monolithic catalyst. Indolene HO 0 fuel with 0.1% sulfur content.

-37The air fuel ratio does not s.eem to influence the results provided the catalyst temperature is kept constant, and sufficient oxygen is supplied' (through secondary air injection) to the catalyst to oxidize the unburned hydrocarbons, carbon monoxide, and sulfur dioxide (Fig. 4.12). 4.6 Concluding Remarks The foregoing results indicate that the particulate emission, sulfuric acid emission, and sulfur conversion are nearly the same for both the monolithic and the pelleted catalyst provided the speed, the fuel sulfur content, and the catalyst temperature are the same for both catalysts, This implies that the emission is governed mostly: by the operating parameters and depends less on the type of catalyst (pelleted or monolithic). As noted before, in the present tests the operating conditions were set to indicate the effects of the various parameters individually on the emissions. In applying the results to actual operating conditions the appropriate combination of these parameters must be selected.

LI I0 MONO-'HIC To - ).. I. l. \O 13 14 15 16 17. """' (E g 0.03 E0.02:. $ I,,i.'l,..... 13 14 15 16 I? I,,.. 1 w T CP c,0.05 c: w 0.04;-3 —- I I4, I I II I l I II I"' I I 13 14 15 16 17 AIR FUEL RATIO ig. 1-.12.'Ffect of air Fuel ratio on sulfur conversion, 1I2SO emis.sion and narticulate cmnii.ssion for a monolithic catalyrst. P88 km 1cruise condition. Excess air 25% ( 5% 02) catalyst temperature 623 K, Indolene HO O fuel with 0.1% sulfur content. (-) fit to data.

-39APPENDIX A ENGINE SPECIFICATIONS AND OPERATING CONDITIONS A.1 Engine Specifications Displacement 350 cubic inches Horsepower (adv.) 250 at 4800 RPM Carburetor 2 barrel Rochester Compression ratio 9.0:1 Bore 4.00 inches Stroke 3.48 inches Spark plugs AC R455 Point dwell 30 degrees A.2 Steady Speeds All tests at steady speeds were performed at conditions corresponding to a full sized 1970 Chevrolet cruising under road load conditions. The engine speed was calculated from __ (A.1). Z r where S* is the car speed, R is the rear axle ratio, and r is the radius of the rear tires. For a standard Chevrolet R is 3.07 and r is 351 mm [21]. The load on the engine was calculated from B61P. iLoV (.0o27w+ L20053#9V2) (A.2) where V is the vehicle speed (km h-l), W is the total weight of the car (17796.8 N) and A is the projected area of the automobile (2.88 m2) [21].

-40A.3 Cyclic Operating Conditions The cycle under which the engine was run was an approximation to the 7 mode Federal Test Procedure, Table A.1 [22, 231. The cycle used in the tests is given in Table A.2. A.4 Catalysts Specifications Pelleted Catalyst: The pelleted catalyst was a General Motors extrudate catalyst with a 5 to 2 platinum-palladium ratio and a nominal loading of 0.332 troy oz/cu ft. Monolithic Catalyst: The monolithic catalyst was an Engelhard PTX, type IIB catalyst.

-41Table A. 1 Actual 7 Mode Federal Test Procedure (The load is to be kept constant at 14 HP) Mode. Speed Time, s Cumulative k h-1 time. s km h 0 (idling) 20 20 I. 0-48 14 34 II 48-48 15 49 III - 48-24 11 60' IV 24-24 15 75 V 24-80 29 104 VI 80-15 25 129 VII 10-0 (idling) 8 137 Table A.2 Approximation to the 7 Mode Federal Test Procedure (For every new mode the torque was set to the value necessary to produce 14;HP at the maximum rpm). Mode RPM Time, s Cumulative time, s. 700 (idling) 20 20 I 700-1150 14 34 II 1150-1150 15 49 III 1150-900 11 60 IV 900-900 15 75 V 900-1800 29 104 VI 1800.... 25 129.VII....700 8 137

-42APPENDIX B PHYSICAL AND CHEMICAL PROPERTIES OF INDOLENE HO 0 FUEL SUPPLIED BY AMOCO OIL COMPANY Test ASTM Method Specification Test Values Control Limit API Gravity D287 58.0-61.0 59.6-61.9 Distillation % F D86 Initial Boiling Point D86 75-95 86-93 10% Evap. D86 120-135 129-135 50% Evap. D86 200-230 220-221 90% Evap. D86 300-325 315-318 Maximum D86 NMT 415 398-406 10% Slope D86 NMT 3.2 2.9-3.9 Reid Vapor Pressure D323 8.7-9.2 8.9-9.0 Oxidation Stability Minutes D525 NMT 600 600+ Gum, mg/100 ml (after Heptane wash) D381 NMT 4.0 0.2-3.0 TMEL grm. lead/gal. D526 NMT 0.05 0.0-0.01 Sulfur-Weight, % D1266 NMT 0.10 0.01-0.017 Olefin, % D1319 NMT 10 3.9-7.4 Aromatic, % D1319 NMT 35 26.1-29.5 Saturates, % D1319 Remainder 63.1-71.1 Octane Research (Clear) D2699 95.0-98.5 96.'6-97.4 Octane Research (3cc TEL/gal) D2699 NLT 103.0 105.0-106.2 Phosphorus, gms./gal. D3231 NMT 0.005 0.000-0.003 Sensitivity (Clear) 7.0-10.5 8.3-9.4 Sensitivity (3cc TEL/gal) NMT 9.0 7.1-8.5

-43APPENDIX C ENGINE AIR FLOW RATE AND FUEL FLOW RATE C.1 Air Flow Rate The air flow rate was measured during each test using a rounded approach air cart manufactured by General Motors Corporation. The pressure drop across the orifice was measured with a micromanometer and was related to the air flow rate by the expression Ai'r = - VA P Y(~( ) (C.1) where K is a constant, Ap is the pressure drop across the nozzle (inches of water), Tair is the room temperature (deg K) and Pat is the atmospheric pressure (in Hg). C.2 Fuel Flow Rate The fuel volume flow rate was measured with a burette. In calculating -3 the mass flow rate the fuel density was taken to be 0.74 g cm

-44APPENDIX D CALCULATION OF THE CONVERSION OF SO2 TO SO3 SO3 is produced by the reaction SO 2 + X/, O~ _50~3 (D.1) In order to calculate the rate constant k it is assumed that the above reaction is a first order, reversible reaction. For such a reaction the rate con. stant (dm3/(h)x(catalyst mass in kg)) is given by [20] kw = Ss2 (D.2) cSct- (CSq)E. where (-rso2) is the rate of disappearance of SO2 (moles of SO2 reacted/ catalyst mass kg x h ), CSO2 is the concentration of SO2 (moles/dm3) at a given position inside the catalyst, (CSO2) is the chemical equilibrium conE centration of SO2 (mole/din3). rso2 and CSO2 are not known directly but must be determined from the information available which are the amount of SO2 entering the catalyst (reactor) and the amount of SO3 leaving the catalyst. In order to utilize the available information we assume that the reaction takes place in a plug flow type reactor shown in Fig. D.1. For a differenti element containing a dm mass of the catalyst an SO2 mass balance gives [20] (Oj.);, XS~T=- soz ds (D.3) Upon integration eq. (D.3) becomes (XSaa) 04t _rt = _ / d lut50,(D. 4) {r__~ -So~ir

CATALYTIC REACTOR dm lF ~2 1 0S dFS02L XSO2 XS02+dXS02 2(Xs~2)i L Fsl2 IS0o(l2)out ~~~~~~~2 i~~n ~S02 ut ig. I).1.'Plug'1lo rcacto-r in the calculation o' SO-2 conversion. X,2 denotes the fraction of SO2 transtformed to S03. Ftr)? denotes the molar flow rate of SO. (mol/sec). The subscripts in and out re:.resent theconditi.ons at the inlet and outlet of the catalyti:c reactor.

-46m is the mass of the catalyst in the reactor, (FSo2) is the molar flow of S02, (Xso2) is the fraction of SO2 converted into S02. The subscripts in and out represent the conditions at the inlet and outlet of the reactor, respectively, By assuming that (Xso2) = 0, and substituting eq. (D.2) into' (D.4) we obin tain WL (i xso1 (FsoL f( k | -c, (D. 6) With the definitions X50' Cso ) -- C S. (D.7a) CsOZ( + Sqf tC oz ) (C So_)t _ ___zl___-_ _) ~ (XsozlEC A C (' 2)EI)E YC- )- (D.7b) eq. (D.6) yields k r —" (Cso) = E- X2 (D. 8) The subscript E denotes chemical equilibrium. Integration of eq. (D.8) gives kl ((. sol)E k (_' _So_)_e "'so2 )ot (D. 9) (Fsozj'i The following calculations were performed for m = 1 kg. (XSO)F as a function of temperature was obtained by Hammerle et al [9]. Their result is reproduced here in Fig. D.2. (Xso2)n,,t was measured in

I100 C, w 80 c, 60 "''~ *,.40 8 o _ _ 20 500 0: 600 700:: 800 900 10.00 1100 TEMPERATURE K Fig. D.2. Conversion of S02 to SOg at chemical equilibrium (from Hammerle and Mikkor (9)) Fig.D.2 Coverson f S2 toS3

-48the present experiments. The results of the measurements are shown in the top three plots of Fig. 4.3. Note that S conversion is the same as 100 x (XS02)out, (Cs02).in was determined as follows. The catalyst was operated with 25 percent access over stoichiometric. This corresponds to an "air fuel ratio" of 19:1 through the catalyst. The "air fuel ratio" through the catalyst is defined as IeAI _ f f'- i /"~ ~ ~ t d - A _,q:f (D. 10) mass o/ Afe' hvneLq'4in he - en(e vn The amount of sulfur per kg of exhaust gas is LS_- ~ _ x _ (D.11) _ flt V +W 100 where S is the percent sulfur in the fuel by weight. The number of moles of SO2 per kg of exhaust gas is (CSOatj ~ _S_ k _g mo_ _ (D.12)' 3z kjg -has since one mole of S in the fuel gives rise to one mole of SO2. Equations (D.10), (D.11) and (D.12) give (Cs O)i = xS oe (D.13) (t2 o) (52() k3 O) exaws or ( C.)iL o)(3 )(,o).Y ea.(D.14) where e is the density of the exhaust gas. This density was calculated exh by assuming that the density of the exhaust gas is the same as the density of air at the temperature and pressure of the exhaust. The results are shown in Fig. D.3.

-49) 165 I:F FFUEL SULFUR 4 0.3% E l 0 0,% j. ),-,, 0 W. I-. I I I, 10 10 3 500 600 700 800 900 1000 1100 1200 TEMPERATURE K Fig. D.3. (:oncentration ofl S-;) at tilhe inlet oF the catal.yst' as a Function oF temperature and fuel sullfur content.

-50In eq. (D.9) (FSo2)in is the number of moles of SO2 entering the catalyst per hour (Fso ),~ _' zone Cre e ~ imo es (Fs oed _____ J 3 o(D.15) The results for (FSO)in are given in Table D.1. In order to obtain k,eq. (D.9) was plotted in Fig. D.4 for various temperatures. The slope of the lines gives the rate constant. The rate constant as a function of inverse temperature is represented in Fig. D.5. Arrhenius' equation gives the rate constant as [20] - E(D. 1.6) where A and E are two constants, R is the ideal gas constant (R = 8.28 joule/ gmol K) and T is the absolute temperature (degrees K). From the line in Fig. D.5 the values for A and E are E = 87.450 joule/gmol K, A = 3.97x 103. By knowing k the sulfur conversion can be readily calculated from eq. (D.9), i.e. < (Csc;4 0 - e S ) (D.17)'~~~~~ ZO.

-51Table D.1 Molar Flow of SO2 into the Catalyst Speed Fuel (FSO ) 2 in km h1 Consumption g moles h1 km h g moles h kg h 96 10.0 0.32 88 8.3 0.26 64 5.8 0.19 22 3.0 0.09

9.0 813 0.8 /773K o x _0.6 IIO~.c02 573K 0 2.0 4.0 6.0 80 90.0 lCSOP in 6 7 (Cso2)i Ff. D.,-I. Relationshil) bctween fractions of SO2 converted into 503 and the 509 concentrations as a function of- tenverature. rsol represents the molar flow rate of S02 (mole sl). The subscrirts in and out denote the nconditions of the inlet and outlet, or the catalytic reactors. Vicrure was calculated assuming one kg o- catalyst in the reactor.

I ~RATE CONSTANT kdin3 h' (kg catalyst) O O, Qn~~~~~~~~~~ 8 I1111 Z/ ~c-t -, fif c ~ -I " ~~i3 C, 30 n 0 CJ?~~~~~ I ii IIii

-54REFERENCES 1. Pierson, W.R.; "Sulfuric Acid Generation by Automotive Catalysts," Paper No. 42, Symposium on Auto Emission Catalysis, Division of Colloid and Surface Chemistry, ACS 170th National Meeting, Chicago (August 1975). 2. Pierson, W.R., Hammerle, R.H., and Kummer, J.T.; "Sulfuric Acid Aerosol Emissions from Catalyst-Equipped Engines," SAE Paper 740287 (1974). 3. Creswick, F.A., Blosser, E.R., Trayser, D.A., and Foster, J.F.; "Sulfuric Acid Emissions from an Oxidation-Catalyst Equipped Vehicle," SAE Paper 750411 (1975). 4. Trayser, D.A., Blosser, E.R., Creswick, F.A., and Pierson, W.R.;'Sulfuric Acid and Nitrate Emissions from Oxidation Catalysts," SAE Paper 750091 (1975). 5. Bradow, R.L., and Moran, J.B.; "Sulfate Emissions from Catalyst Cars: A Review," SAE Paper 750090 (1975). 6. Begeman, C.R., Jackson, M.W., and Nebel, G.J.; "Sulfate Emissions from Catalyst-Equipped Automobiles," SAE Paper 741060 (1974). 7. Holt, E.L., Bachman, K.C., Leppard, W.R., Wigg, E.E., and Somers, J.H.; "Control of Automotive Sulfate Emissions," SAE Paper 750683 (1975). 8. Mikkor, M., Hammerle, R.H., and Truex, T.; "Effects of Hydrocarbons, Carbon Monoxide and Oxygen on Sulfuric Acid Emission from an Automotive Catalyst," Paper No. 43, Symposium on Auto Emission Catalysts, Division of Colloid and Surface Chemistry, ACS 170th Annual Meeting, Chicago (August 1975). 9. Hammerle, R.H., and Mikkor, M.; "Some Phenomena which Control Sulfuric Acid Emission from Automotive Catalysts," SAE Paper 750097 (1975).

-5510. Sampson, R.E., and Springer, G.S.; "Effects of Temperature and Fuel Lead Content on Particulate Formation in Spark Ignition Engine Exhaust," Environmental Science and Technology, 7, 55-60 (1973). 11. Ganley, J.T., and Springer, G.S.; "Physical and Chemical Characteristics of Particulates in Spark Ignition Engine Exhaust," Environmental Science and Technology, 8, 340-347 (1974). 12. Fritz, J.S., and Yamamura, S.S.; "Rapid Microtitration of Sulfate," Analytical Chemistry, 27, 1461-1464 (1955). 13. Fielder, R.S., and Morgan, C.H.; "An Improved Titrimetric Method for Determining Sulfur Trioxide in Flue Gas," Analytica Chimica Acta, 23, 538-540 (1960). 14. Street, J.C., and Thomas, A.; "Carbon Formation in Premixed Flames," Fuel, 34, 4-36 (1955). 15. McKee, H.C., and McMahon,W.A., "Automobile Exhaust Particulates Source and Variation," Journal of the Air Pollution Control Association, 10, 456-462 (1960). 16. McKee, H.C., McMahon, W.A., and Roberts, L.R.; "A Study of Particulates in Automobile Exhaust," Proc. of the Semi-Annual Tech. Conf., Air Pollution Control Association, 208-227 (1957). 17. Dubois, L., Zdrojewski, A., Jennawar, P., and Monkman, J.L.; "The Identification of the Organic Fraction of Air Sample," Atmospheric Environment, 4, 199-207 (1970). 18. Cukor, P., Ciaccio, L.L., Lanning, E.W., and Rubino, R.L.; "Some Chemical and Physical Characteristics of Organic Fractions in Air-Borne Particulate Matter," Environmental Science and Technology, 6, 633-637 (1972).

-5619. Ter Haar, G.L., Lenane, D.L., Hu, J.N., and Brandt, M.; "Composition, Size and Control of Automotive Exhaust Particulates," Journal of the Air Pollution Control Association, 22, 39-46 (1972). 20. Levenspiel, O.; "Chemical Reaction Engineering," John Wiley and Sons, Inc., 1972, p. 460-524. 21. "Passenger Car Data," Ethyl Corporation, Petroleum Chemicals Division, 100 Park Avenue, New York, N.Y. (1970). 22. Control of Air Pollution from New Motor Vehicle Engines, Federal Register 31, Part II, 5170-5178 (March 1966). 23. Control of Air Pollution from New Motor Vehicles and New Motor Vehicle Engines, Federal Register 33, Part II, 8304-8324 (June 1968).

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