Effect of Different Parameters on GTL

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DOE/PC/89866--E5DE92 015592

DIRECT CONVERSION OF LIGHT HYDROCARBONGASES TO LIQUID FUEL

Report No. 19Quarterly Technical Status Reportfor

First Quarter F.Y. 1991

Project Manager' R. D. KaplanPrincipal Investigator' M. J. Foral

Work performed under Contract No. DE-AC22-89PC89866For

U. S. Department of EnergyPittsburgh Energy Technology Center

Pittsburgh, PennsylvaniaBy

Amoco Oil CompanyResearch & Development DepartmentPost Office Box 3011

Naperville, IL 605660

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees, makes any warranty, express or implied, or assumes any legal liability or responsi-bility for the accuracy, completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights. Refer-ence herein to any specific commercial product, process, o_ service by trade name, trademark,manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom-

mendation' r fayring bY the United State_ Gvernment r any agency thercxff' 'l'he views _/_\ _o_T _and opinionsof authorserpressedhereindo not necessarilystate or reflect those of the (_.$UnitedStatesGovernment.ranyagencythereof, _ _;,.._,,....

DISTRIBUTION OF THIS DOCUMENT ISUNLIMtTf-., ,';

j ' ,'


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FINAL QUARTERLY PROGRESS kEPORT SUBMITTED TO:I. George Cinquegrane (2 copies)

Contracting Officer's RepresentativeU.S. DOE/PETCP.O. Box 10940Pittsburgh, PA 15236

2. Dona G. SheehanContract SpecialistU.S. DOE/PETCP.O. Box 10940Pittsburgh, PA 15236

3. Robert M. HamiltonFE-231, E- 155/GTNU.S. Department of EnergyWashington, DC 20545

4. Gilbert V. McGurlProgram ManagerU.S. DOE/PETC, MS 922-HP.O. Box 10940Pittsburgh, PA 15236


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ADDITIONAL CIRCUlaTION FOR DRAFT REPORTS TO:Amoco CorporationSuite 600305 East Shuman BoulevardNaperville, IL 60563-8408T. H. FleischAmoco Oil CompanyP.O. Box 3011Naperville, IL 50566

R D Kaplan, H-4M J Foral, H-4A R LaPuma, H-4D W Washecheck, H-2D _ Lerman, H-IE G Wollaston, H-3A S Couper, H-IJ A Mahoney, F-7


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TABLE OF CONTENTSPa__&e

EXECUTIVE SUMMARY ....................................... 7BACKGROUND .............................................. 8PROGRAM OBJECTIVES ...................................... 9PROJECT DESCRIPTION ..................................... 9RESULTS AND DISCUSSION .................................. i0

Task 3.5' Reactor Geometry Effects ................ I0Effect of Temperature ................... IIEffect of Oxygen Concentration .......... II

Task 3.3' Effect of Feed Injection Systems ....... 12CONCLUSIONS ............................................. 12ACKNOWLEDG EMENT ......................................... 12


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LIST OF FIGURES

FIGURE I Effect of Reactor Diameter on Methanol Selectivity" TemperatureTrendsFIGURE 2 Effect of Reactor Diameter on Methanol Yield" Temperature TrendsFIGURE 3 Effect of Reactor Diameter on Methanol Selectivity' OxygenConcentration Trends

FIGURE 4 Effect of Reactor Diameter on Methane Conversion' OxygenConcentration TrendsFIGURE 5 Effect of Reactor Diameter on Hydrocarbon Conversion' OxygenConcentration Trends

FIGURE 6 Effect of Reactor Diameter on Methanol Yield' Oxygen ConcentrationTrends


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DISCLAIMER

This report was prepared as an account of work sponsored by the United StatesGovernment. Neither the United States nor any agency thereof, nor any oftheir employees, makes any warranty, expressed or implied, or assumes anylegal liability or responsibility for the accuracy_ completeness, orusefulness of any information, apparatus, product, or process disclosed, orrepresents that its use would not infringe privately owned rights. Referenceherein to any specific commercial product, process or service by trade name,mark, manufacturer, or otherwise, does not necessarily constitute or imp].y itsendorsement, recommendation, or favoring by the United States Government orany agency thereof. The views and opinions of the authors expressed herein donot necessarily state or reflect those of the United States Government or anyagency thereof.

TECHNICAL STATUS

This technical status report is being transmitted in advance of DOE review,and no further dissemination or publication will be made of this reportwithout prior approval of the DOE Project/Program Manager.


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7EXECUTIVE SUMMARYAmoco Oil Company, under a contract with the United States Department ofEnergy, is investigating the direct conversion of light hydrocarbon gases toliquid fuels via partial oxidation. This report describes work completed inthe fifth quarter of the two-year project. Work continued and progress wasmade on two other tasks during this quarter:

Task 3.3 (Studies of different reactant gas mixing and injectionsystems): Three different mixing systems have been designed and constructed.Two consist of different sizes of commercial in-line static mixers, and oneconsists of two partially-closed needle valves in series. This latterconfiguration is similar in principle to that used by Prof. Gesser at theUniversity of Manitoba. Prof. Gesser has reported exceptionally high methanolselectivities and yields with this system. The feed section of the pilotplant has been modified to allow rapid switching between these different mixerconfigurations. Experiments are currently underway to study the effects offeed mixing on methane conversion and methanol selectivity.

Task 3.5 (Studies to determine the effect of reactor geometry): ThreeA sizes of reactor have been studied, differing in diameter but not in length.

In this way the effects of reactor surface-to-vol_ne ratio on methanolselectivity and yield have been assessed. The higher surface-to-volume ratio(small diameter) reactor is much more sensitive to high reaction temperatures,showing a steep decrease in methanol selectivity with temperatures above900F. The larger diameter reactors showed a much more moderate decrease inmethanol selectivity with higher temperatures. These results can be explainedby increased high-temperature decomposition of methanol on the reactor wallsin the high surface-to-volume (small diameter) reactor, lt also appears thatthere is an interaction between reactor diameter (surface-to-volume ratio) andoxygen concentration effects. The smaller diameter reactors showed amonotonic increase in methanol selectivity with decreasing oxygenconcentration between 12.5 vol% to 1.0 vo1%, while the large diameter reactorexhibited a maximum in methanol selectivity at around 4-6 vol% oxygen. Thereason for this behavior is not known, but may involve third-body (wall)

, stabilization of!methanol-forming intermediates at lower oxygenconcentrations.

Because of previous operability problems with the pilot plant the projectremains about 3-4 weeks behind schedule. The total cost of the projectthrough December 1990 was $371M; this is $172M below the budget plan of $543M.About $35M of this difference is due to being behind schedule, the remainder(about $137M) is the true under-run. In the next quarter we will continuestudying the effect of feed mixing (Task 3.3). Work will also begin on theeffects of product quench (Task 3.4) and product recycle (Task 3.6).


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8BACKGROUND

Fischer-Tropsch synthesis, gasification processes like Lurgi dry bottom gas,direct coal liquefaction, and remote natural gas ali represent sources ofsubstantial quantities of light hydrocarbon gases. Methane is the major andmost stable component of ali these gases. Steam reforming methane to producesynthesis gas is capital-intensive because it is highly endothermic andrequires severe reaction conditions. A process for direct conversion of lightgases, especially methane, to methanol, gasoline, or other liquid fuels couldbe far superior.Steam reforming is the first stage in traditional commercial methods for theproduction of liquid fuels. This first step produces syntheses gas:

CH 4 + H20 --> CO + 3Hz AH - 49.3 kcal (I)The_synthesis gas is then converted into methanol via a catalytic process.

CO + 2H2 ----> CH_OH AH - -21.7 kcal (2)Reaction I produces more hydrogen than required by reaction 2. The excesscan either be utilized elsewhere in the case of a domestic refinery or, in thecase of a remote operation, is lost. A third step could be the catalyticcondensation of methanol to gasoline,A more efficient route of converting light hydrocarbons would be to directlyform methanol by partial oxidation.

CH4 + 02 --> CH30H _H - -30.7 kcal (3)Such a process could substantially reduce capital, and energy requirements formethanol production. The methanol could be used as a fuel or a fuel blendingcomponent, as in the case of MSO fuels (80% methanol, 20% gasoline), or elseconverted into gasoline through well-known processes, such as MTG. A plantbased on Reactions i and 2 followed by methanol condensation to gasoline hasbeen built and is operating in New Zealand. However, the process isuneconomical if it were not for the New Zealand Government support. If aprocess for the direct conversion of light hydrocarbons to methanol isfeasible, thereby eliminating the process steps shown by Reactions I and 2,then a gas-to-gasoline process could become economically viable.

A proposed process for converting light hydrocarbon gases directly to

hydrocarbon liquids, e.g., methanol or formaldehyde_ is not new. In 1932

Newitt and Haffner reported the formation of methanol, along with snlalleramounts of formaldehyde and formic acid, in the high-pressure oxidation ofmethane. (I) The reaction was carried out in a static system at 360-393C and r50-150 atm. The maximum methanol selectivity was ca. 22%; however, CH_conversion was only a few percent. More recently, Gesser, Hunter and co-workers have reported methanol selectivities up to 89% ar,dyields of around7%. (2) However, other workers have in general been unable to reproduce theseresults.


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9 900F) than themedium or large diameter reactors. Figure i shows that with the small reactormethanol selectivity dropped from 26_ to only 7_ as temperature increased from900 to II00F. With the medium and large diameter reactors methanolselectivity decreased to only 20_ from 27_ over the same temperature range.Hydrocarbon conversion was not affected by reactor diameter, so the change inmethanol selectivity is reflected in the methanol yield trends (Figure 2).This effect is probably due to increased decomposition of methanol on thewalls of the reactor at higher temperatures. The smaller diameter reactor hasa higher surface to volume ratio and therefore is more sensitive to these walleffects.

0vgen Concentration EffectsThe results of varying oxygen concentration are presented in Figures 3-6.The most significant difference between the various sized reactors is inmethanol selectivity (Figure 3). With both the "medium" and "small" diametertubes, selectivity to methanol increased monotonically with decreasing oxygenconcentration. With the "large" tube, however, there is a clear maximum inmethanol selectivity at around 4-6 vol_ oxygen. Preliminary analysisindicates that in the large tube more formaldehyde is produced at lower oxygenconcentrations than at higher oxygen concentrations. These trends arecurrently being compared to data from the small and medium tube runs. lt ispossible that formaldehyde decomposition on the walls is more significant inthe small and medium diameter tubes. Another possibility is_ that wallinteractions in some way stabilize methanol-forming intermediates at lowoxygen concentrations, leading to higher methanol selectivities in the smallerdiameter reactors.In ali three reactors, both methane and overall hydrocarbon conversionsincrease with increasing oxygen concentration, as shown in Figures 4 and 5

r _tnq .i


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Figure 1Effect of Reactor Diameter on MeOHSelectivity

Temperature Trends; P=1100-1300 psig; HC/O2=10Methanol Selectivity (%)35

O[]EJ '- I_ __ _ O Large,MediumTubes25 ...................................................................................................................................B..................................................................................

20 ...................... ...............................15 .......................................................................................................

10 .............. _ SmallTube5 .......

0 , _ _1_ 1 1 I J600 700 800 900 1000 1,100 1,200

Temperature (F)mal_'ube Medlu_Tube Larg%Tube

Figure 2Effect of Reactor Diameteron MethanolYieldTemperature Trends; P = 1100-1300psig; HC/O2= 10

MethanolYield (%)65 ........ O ....[]]

,/k _ __ [] Large, MediumTubes

............ Z_& _ ........3 ............ Z_&......

=

2 .............. SmallTube0 I 1 I I L600 700 800 900 1000 1,100 1,200

Temperature (F)SmallLTUbeMediul_TUbe Larg_Tube


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Figure 3Effect of Reactor Diameter on MeOH Selectivity

Trend with 02 Concentration; T=850F; P=1300 psigMethanol Selectivity (%)50 .......................................................................................

,_ _ Small, Medium Tubes40 .......... D .......

3o

20 L__10 i '. i i f i0 2 4 6 8 lo 12 4

Oxygen Concentration (vol%)SmalLube_ Mediu_Tube L.arg_Tube

Figure 4Effect of ReactorDiameter on CH4 ConversionTrend with 02 Concentration;T=850F', P--,1300 psig

Methane Conversion (%)8 .... Small Tube ,,.,"_Med

. __ . Tube

(2) , ,[ I I , l0 2 4 6 8 10 12 4Oxygen Concentration (voi%)SmalI.Tube_Mediumc_.jube LargeTube


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i _ LI II ',!!ll' , IIL _,i,ll _i' _i liillll,i, IlL LI, II ,, ,,_, ,hi_l 14 ._ ,I....... Li....................... '..L_...J.......... ' _ JL i" ' ,,

Figure 5Effectof ReactorDiameteron HC ConversionTrendwith02 Concentration;T=850F; P= 1300 psig

HydrocarbonConversion(%)20 ....................................................................................................................................mall _A........

__...__ Medium15 ......................................................... __ ............ Large

10 - ' _ ......

_

0 .... J ..... w ........ J....... ' 1 ! ......0 2 4 6 8 10 12 4Oxygen Concentration (vol%)SmalkTube Medium Tube Large_Tube[] _,,,

Figure 6Effect of Reactor Diameter on Methanol YieldTrend with 02 Concentration; T=850F; P= 1300 psig

Methanol Yield (%)7 .6 ...............Medium Tube5 ...... _-------.&7. @

Small Tub e O,/,i--_-------=,---__

_ Large Tube2 ,,1 l I L _ J J,0 2 4 6 8 10 12 14

O_gen Concentration (vol%)SmalLITube Mediul_ Tube Larog_)Tube


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respectively. The small differences in conversion between reactors suggestedby the lines on these plots are not considered to be significant. Because themethanol selectivity in the large diameter reactor exhibits a maximum whilehydrocarbon conversion changes monotonically, the methanol yield in the largereactor exhibits a maximum. Figure 6 shows that this maximum occurs around 8vol% oxygen and is slightly lower than the maximum yield with the medium tubebut slightly higher than the maximum yield with the small tube. Maximummethanol yield was between 4-5 mol% regardless of reactor diameter.

These results are interesting and require some further analysis. They mayhelp explain some inconsistencies apparent in the methane partial oxidationliterature. Most workers report a monotonic increase in methanol selectivitywith decreasing oxygen, but some have observed a maximum selectivity occurringaround 4-8 vol% oxygen, lt is possible that wall effects and/or wallreactivity could play a role in explaining these discrepancies.

Task 3.3: Feed In_ection Effects

The first investigations to be made under this task will study the effects oifeed mixing on methanol selectivity and methane conversion. The feed inletsection of the plant has been re-designed to allow rapid switching between oneof four mixing systems. These consist of two sizes of commercial in-linestatic mixers, a series of two partially-closed needle valves, and a packedbed mixer composed of a h-inch diameter tube filled with I/,-inch ceramic balls.Experiments are currently underway with the commercial static mixers and theneedle valves. Results will be presented in subsequent reports.CONCLUSIONS

The above results indicate that reactor geometry (irt particular reactorsurface-to-volume ratio) can have a significant effect on this system. Thehigher surface-to-volume ratio (small diameter) reactor was much moresensitive to high reaction temperatures, showing a steep decrease in methanolselectivity with temperatures above 900F. The larger diameter reactorsshowed a much more moderate decrease in methanol selectivity with. highertemperatures. These results can be explained by increased high-temperaturedecomposition of methanol on the reactor walls in the high surface-to-volume(small diameter) reactor. In addition, it appears that there is aninteraction between reactor diameter (surface-to-volume ratio) and oxygenconcentration effects. The smaller diameter reactors showed a monotonicincrease in methanol selectivity with decreasing oxygen concentration between12.5 and 1.0 vol%, while the large diameter reactor exhibited a maximum inmethanol selectivity at around 8 vol% oxygen. The reason for this behavior isnot known, but may involve third-body (wall) stabilization of methanol-formingintermediates at lower oxygen concentrations. P

ACKNOWLEDGEMENT

This work was supported by the United States Department of Energy underContract DE-AC22-89PC89866.


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13NOTICE

This report was prepared by the organization(s) named below as an account ofwork sponsored by the United States Department of Energy (DOE). Neither DOE,members of DOE, the organization(s) named below, nor any person acting onbehalf of any of them: (a) makes any warranty, express or implied, withrespect to the use of any information, apparatus, method, or process disclosedin this report or that such use may not infringe privately owned rights; or(b) assumes any liabilities with respect to the use of, or for damagesresulting from the use of, any information, apparatus, method, or processdisc].osed in this report.

Prepared byAmoco Oil Company (Amoco Corporation)Naperville, Illinois/MJ F/jmb/910 3


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Effect of Different Parameters on GTL

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