CA1163614A - Extruded bimodal alumina catalyst supports - Google Patents

Abstract

Abstract of the Disclosure A thermally stable, bimodal alumina extrudate suitable for use as a catalyst support for hydrogenative coal liquefaction. Most of the surface area is in a micropore region having pores of less than 600 Angstrom units and this region has a pore volume of 0.65 to 0.89 cm.3/g. The pore volume median pore diameter in this micropore region is within the range of 110-150 Angstrom units with a preferred range of 110-130. The macropore region, made of pores having diameters of 600-10,000 Angstrom units, has a pore volume of at least 0.08 cm.3/g.
and comprises greater than 8% of the total pore volume.

Description

~63614 EXTRUDED BIMODAL ALUMINA CATALYST SUPPORTS

Uackqround o the Invention 1. Field of the Invention This invention relates to extruded alumina particles having a controlled pore size distribution which are sui~able as catalyst supports especially for hydrogenative coal liquefaction and to a meehod of producing them.

2. Description o the Prior ~rt Recently there has been renewed interest in coal liquefaction and the various processes to produce coal liquids. One of these is the H-Coal process developed by Hydrocarbon Research Inc. which has a bench scale ~-Coal unit in Trenton, New Jersey, for catalyst evaluation. The catalyst being used in this process is the catalyst HDS-1442A made by American Cyanamid.
This material has an average pore diameter of 58 Angstrom units, a surface area of 323 m.2/g., a-pore volume of 0.64 cm.3/9. with the major pores in the range of 20-140 Angstrom units, and an apparant bulk density of 0.57 g./cm.3. These micropores have been measured by nitrogen desorption, since ~his giYes more accurate readings in the small pore range. When the entire pore range is measured by the mercury penetration method, the ~arger pores are measured.
Using this technique the large pore volume from pores greater than 1000 Angstrom units in diameter is about 28 percent of the pore volume.
One method of evaluating a catalyst for coal liquefaction is to measure the amount of benzene soluble oil produced. The larger the amount produced, the higher will be the quality of the liquefaction product.

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3. Objects of the Invention It is an object of the present invention to develop a catalyst support which, when converted into a metal containing catalyst for coal liquefaction, is able to achieve a higher benzene soluble conversion than the HDS-1442A catalyst.
It is a further object of this invention to obtain an alumina catalyst support characterized by having a large amount of surface area in the form of micropores where the pore volume median diameter as measured by nitrogen porosimetry is between 110 and 150 Angstrom units. In addition the support should also have a significant amount of macropore volume characterized by pore diameters greater than 600 Angstrom units.
It is a further object of this invention to provide a method to produce a bimodal alumina extrudate which has both micropore and macropore volumes.
These and further objects of the invention will be evident from the following discussion.
Summary of the Invention The present invention provides a bimodal pore size alumina extrudate suitable for use as a catalyst support having a substantial micropore volume made of relatively small pores having a pore diameter of less than about 200 Angstrom units and greater ~ than about 8 percent of the total pore volume being a macropore ; volume made of relatively large pores having a pore diameter greater than about 600 Angstrom units, said extrudate having ` a crush strength of greater than 1.5 pounds per millimeter when measured on extrudates having a diameter of 1/16 inch;

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1 163~ 14 a surface area of about 170-220 m.2/g as measured by nitrogen porosimetry;
a micropore volume, based on nitrogen porosimetry for pore diameters of 600 Angstrom units or less, of about 0.65 to 0.8g cm. /g.;
a macropore volume, based on mercury porosimetry for pore diameters greater than 600 Angstrom units, of greater than or equal to about 0.08 cm.3tg.; and a pore volume median pore diameter, based on nitrogen, of 110-150 Angstrom units.
The invention also relates to an improved method of producing a pure transition alumina extrudate suitable for use as a catalyst support for coal liquefaction, having a crush strength greater than 1.5 lb/mm when the extrudate is 1/16 inch in diameter, and a surface area in the range of about 170-220 m2/g when measured by nitrogen, porosimetry, and a substantial first volume made of relatively small pores having a pore diameter of less than about 600 Angstrom units, and a second macropore volume made of relatively large pores with a pore diameter greater than about 600 Angstrom units, wherein an alpha alumina monohydrate powder, which is an intermediate between boehmite and pseudoboehmite, is initially mixed with water to form a mixture having a solids content in the range of 36-42 weight percent to form a paste which is then extruded to form extrudates which are dried and calcined, in which the improvement comprises mixing said powder and water until the material forms a coherent ball when squeezed by hand, and calcining ~-:R ~ -2a-,, " ~

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~3614 the extrudates at a temperature in the narrow range of 900-1,200F
to obtain an alumina extrudate having a first pore volume, as measured by nitrogen porosimetry for pore diameters of 600 Angstrom units or less, of about 0.65 to 0.89 cm.3/g.;
a second pore volume, as measured by mercury porosimetry or by water adsorption for pore diameters above 600 Angstrom units, of greater than or equal to about 0.08 cm.3/g.; and a pore volume median pore diameter, based on nitrogen porosimetry measuring pore diameters of less than about 600 Angstrom units, of 110-150 Angstrom units.
A biomodal pore size alumina catalyst support has been developed which has substantial pore volume made of relatively small pores having a pore volume median pore diameter in the range of 110 to 150 Angstrom units while also having greater than about 8 percent of the total pore volume made of relatively large pores having pore diameters greater than about 600 Angstrom units.
This catalyst support is made of a pure transitional alumina and has a crush strength greater than 1.5 lb/mm when the material is in the form of 1/16 inch diameter extrudates. The crush strength is -2b-116361`~

measured by suhjecting the extrudates to a crushing force applied by two parallel plates of a testing machine su~h as the Pfizer ~ardness Tester Model ~M141-33, manufactured by Charles Pfizer and Co., Inc., 63~ Flushing Avenue, Brooklyn, New York. The plates are slowly brought together by hand pressure.
The amount of force required to crush the particle is registered on a dial which has been calibrated in pounds force. A sufficient number lfor example, 50) of particles is crushed in order to get a statistically significant estimate for the total population. The average is calculated from the individual results.
Most oE the surface area is contained in the micropores with the surface area being in the range of about 170-220 m.~/g. when measured by nitrogen porosimetry. The pore volume of this micropore component, when measured by nitrogen porosimetry ~or pore diameters of 600 Angstrom units or less, is in the range of about 0.65 to 0.89 cm.3/g. The pore volume median diameter for the micropore region, when measured by nitrogen-porosimetry for pore diameters of hOO Angstrom units or less, is in the range of 110-150 Angstrom units with a more preferred range of 110-130 25- and with the most preferred support having an average pore diameter of about 125 Angstrom units.
In the micropore volume, there are essentially no pores having a diameter smaller than 40 Angstrom units. That is to say, if there is any pore volume in pores less than 40 Angstrom units, then it is less than 0.05 cm.3/g. In fact, in the preferred embodiment this value is less than 0.03 cm.3/g.
The larger macropore volume, which is measured by mercury porosimetry for pore diameters greater than 1 16~6 1 ~

600 Angstrom units, is greater than or equal about 0.08 cm.3~g., which is greater than abo~t 8 percent of the total pore volume.
The catalyst support is preferably formed as an ext~udate which can have a length to diameter ratio in the range of about 1 to 1 to about 5 to 1, with a more preferred ratio in the range of ahout 2 to 1 to about 3 to 1. The diameter of the extrudates can be of any size smaller than about one-half inch, with a preferred diameter being about lJ16 inch.
These extrudates are prepared in the preferred embodiment by mixing a microcrystalline boehmite-pseudoboehmite intermediate in water so that the mixture contains from 36 to 42 percent A12O3 and subjecting this to a mulling procedure for a period of time until the material will form a coherent ba~l when sgueezed by hand. This mixture is then extruded in the desired diameter and the extrudate is chopped off in the desired length. The extrudates may be initially dried and then subjected to a calcination treatment at a temperature in the range o' 900 to 1200F ~482 to 649C) to obtain the desired micropore diameter range.
~rief Description of the Drawinqs Figure 1 illustrates the relative distribution of pore volumes for a cobalt-molybdenum catalyst usin~
the present support identified as Catalyst A as compared to the standard catalyst for the H-Coal process identified as HDS-1442A.
Figure 2 illustrates the performance in coal conversion over time for a catalyst using the present s~pport identified as Catalyst A as compared to the ~tandard catalyst for the H-Coal process identified as 116361~

HDS-1442A, and two other catalysts identified às Catalysts B and C.
Description of the Preferred Embodi~ents One o~ the characterizing features of the alumina substrates of this invention is the presence of both a -very substantial amount of micropore volume coupled with the required presence of a larger pore volume called the macropore volume. Although there is no intent to limit this invention to any specific mechanism~ the followi~g analogy may be helpful in visualizin~ the present novel product. The substantial micropore region serves to provide the large surface area for catalytic contact ~ith the coal liq~id material being treated. The large macropores, on the other hand, serve as conduits or highways to permit the large coal molecules to enter into the catalyst particle and contact the large interior s~rface area produced by the micropores. The large pores are also believed to be very helpful since they make it more difficult for coke ormation on the outside of the particle to block these large pores which serve as feeder pores for transporting materials into the catalyst interior. In other words, if there were only small pores, the pores on the outer surface would be blocked by the formation of coke during the early use of the catalyst. Since the macropores of the present particle have such large openings, they are not as easily blocked by any coke forming on the ~xtrudate surface.
DESCRIPTION OF l`HE STARTING PO-YDEI~
In making the alumina catalyst support, the preferred material i5 a microcrystalline pseudoboehmite-boehmite intermediate as disclosed in the Sanchez et al ~. S. Patent No. 4,154,812.

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As described therein, a partially dried, hydrous alumina produced by the controlled reaction of sodium aluminate and aluminum sulfate is an intermediate S between boehmite and pseudoboehmite. This form of alumina is alpha alumina monohydrate with extra water molecules occluded within the crystal structure and has the formula A12O3 x H20 where x is a value greater than 1 and less than 2. The boehmite -pseudoboehmite nature of the product, including itscrystalline str~cture, the degree of crystallinity and average size of the individual crystallites, may be determined by x-ray diffraction techniques.
This alumina exhibits an intermediate boehmite-pseudoboehmite structure characterized by a l020] d-spacing which ranges from about 6.2 to about 6.5 Angstrom units, preferably from about 6.3 to about 6.4 Angstrom units. The half maximum intensity wi~th of the l020] peak ranges from about 1.65 to about 1.85 Angstrom units, preferably from about 1.75 to about 1.80 Angstrom units.
In terms of relative crystallinity, the powder exhibits values from about 70 to about 85 weight percen~ of the total amount of A12O3 present in crystalline form. The boehmite-pseudoboehm~te product is further characterized by high crystalline purity, by small crystallite size - i~e., microcrystallinity, and by a high relative degree of crystallinity. In -these respects, this product is unique by virtue o the fact that it is prepared under conditions which give a high ratio of crystalline material to amorphous gel. ~his is in contrast with other aluminas in which the fraction of amorphous gel in the product is either quite high or essentially non-existent, such as in :
, boehmite. ~he intermediate nature of the crystallinity gives the powder uniquè and special properties when used to make extrudates.
F~RMING PROCESS
The alumina obtained above is next mixed with water to qive a total solids coneent of 36 to 42 percent.
This mixture can be mulled in a muller mixer or a su~ficient pe~iod of time to obtain the desired inal properties o the mixture.
An ~dvantage of the muller type mixing is that it permits aggregate breakdown, frictional anchorage of particles of one to another and densification of the final mix. The muller mixer generally is used for batch operations, although it is possible to have a continuous muller.
After the mixture has been mulled sufficiently so as to obtain the desired plastic prope~ties, it is then fed into an extruder. Various extruder machines 20 ~an be e~yloyed. One example is the Auxiliary Worm Extruder manufactured by Welding Engineers Inc. of Norristown, Pennsylvania. This device has a worm screw which pushes the mixture through the die holes to form a continuous extrudate. A cutting device can be positioned outside the die hole to cut off the material into the desired length. When operating the machine, the amount of energy the worm screw exerts on the mixture is measured by a torque meter. The torque is related to the speed at which you drive the worm gear, and the amount required will depend on how well the mixture has been previously mulled. If the applied torque is too high, then the macropores of the prod~ct will be destroyed. This mulled material behaves like modeling clay; if it is compressed too 1 1636~4 much the space between the particles is destroyed.
A~ter the extrudates have been formed a drying step can be added to seduce thermal cracking. This initial drying can be done at a temperature from 150F.-to 300~. (66C. to 149C.) to obtain a moisture content which is less than 25 percent. A further purpose of this drying step is to remove the added water, but not to remove the water of hydration. Thus the drying temperature is not conducted at a high temperature.
A fureher optional step that can be performed before drying is to tumble the exturdates to round the ends and reduce any edge irregularities so as to render the extrudates less susceptible to attrition.
The next step is the calcination step. Here the dried extrudates are heated at a temperature of about 900~. to 1200F. (482C. to 649C) until the moisture content reaches a level of less than 2 percent when subsequently measured b~ heating the calcined particles to 1750F. (954C.). The calcination time required will depend in part on the furnace configuration. It can vary from 0.1-20 hours, with a preferred calcination time being on the order of several hours.
This extruding procedure can be used to produce extrudates having properties in the following ranges.

116~514 Table 1 Property Typical Range Surface Area (m.2/g.) 170 - 220 Compacted Bulk Density ~g~/cm.3) 0.48 - 0.60 $otal Pore Volume (cm.3/g.) .73 - 1.19 Pore Size Distribution (cm.3/g.) Below 600 Angstroms .65 - .8~
~00-10,000 Angstroms 0.08 - 0.30 ~icropore Voiume Median 110 - 150 Pore Diameter ~A) Minimum Micropore Di~meter (~) 40 Minimum Crush Strength (lbs.-force/mm) 1.5 (for 1/16 inch extrudates) Example 1 Tn producing catalyst supports according to the preferred embodiment of this invention, there will be variances in the characterizing data for the batches produced. The following table sets forth generalized properties 9btained for a composite support composition made by mixing together a series of individual batches of the support that were formed.
T~ble 2 PHYSICAL PROPERTIES: SUPP~RT
Avg. diameter. inches 0.058 2S Avg. length, inches 0.168 Avg. crush strength, lb./mm. 1.5 Bulk density, q./cm.3 0.53 ,...

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SURFACE PROPERTIES: SUPPORT
Surface area, m.2/g. 206 Pore volume median micropore diameter, ~ 116 5 Min. ~icropore diameter, ~ 80 Total pore volume, cm.3/g. 0.88 % of total pore volume in pores greater than 600 ~ diameter 17 CHEMICAL AN~LYSIS: SUPPORT
10 CoO, wt. ~ _ MoO3, wt. 9~
Na20, wt. ~ O. 03 CaO, wt. % 0. 01 MICROPO~E ANALYSIS: SUPPORT
Pore volume in pores having diameters between 600 Angstrom units and 580 Angstrom units .0008 cm.3/g.
560 .0017 540 .0023 520 .0029 500 .0042 4B0 .0051 .0061 440 .0071 420 .0081 400 .0096 ~ 380 .0107 ; 360 .0119 340 .0131 320 .0152 ; 3D0 .0172 280 .019~
260 .0228 240 .0260 220 .~311 200 .0385 180 .0489 160 .0768 150 .1134 140 .1665 130 .2242 120 .3341 110 .4191 100 .5329 .6S25 .7291 Total micropore vol., cm.3~g. .73 ; ~inimum pore diameter, A 8 0 Pore volume median 116 micropore diameter, ~
20 ACROPORE ANALYSIS: SUPPO~T
Pore volume in pores having ; diameters between 10,000 Angstrom units and 9000 Angstrom units .0004 cm.3~g.
8000 . 0014 7000 .0111 6000 .0225 5000 .0478 4000 .0771 3000 .1035 2000 . 1285 lO00 .1455 , , . . . .

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~ ~ . ~ ' . . . . ` .

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700 .1499 600 .1502 Total macropore vol., ~m.3/g.- .15 Example 2 When the support material such as that in Example 1 is to be used in making a catalyst, metal compounds such as molybdenum and/or cobalt are dissolved in a solvent an~ the particles are impregnated with this solution.
Thereafter the solvent is removed by evaporation, and the deposited compounds are converted to the metal oxide form by heating the impregnated extrudates. Incorporation of the metal oxides will, of course, alter the ~icropore distribution resulting in a decrease in the surface area, a decrease in the pore volume in the micropore region and a decrease in the pore volume median micropore diameter.
To illustrate this possible change in micropore characteristics, the composite extrudates according to this invention described in Table 2, were impregnated with an aqueous solution containing am~onium molydate and cobalt nitrate. The resulting extrudates were then heated to a temperature of 220F. or a period-of 1 hour to dry the extrudates. The temperature was then raised to 350F. for about 3/4 hours, then to 450F. for about 1/2 hour, then to 700F. for about 1/2 hour and finally to 1,000F. for about 2 hours. The resulting catalyst has the following properties.

Table 3 P~IYSICAL PROPERTI~S: CATALYST
Avg. diameter, inches 0.058 30 Avg. length, inches 0.165 Avg. crush strength, lb./mm. 1.8 ~ulk density, g./cm. - 0.62 , ' ' ' ' . ~

SURFACE PROPER r IES: CATA~YST
Surface area, m`.2/g. 177 Pore volume median micropore diameter, R 112 5 Min. micropore d.iameter, R 60 Total pore v~lume, cm.3/g. 0.71 o total pore volume in pores 20 greater than 600 ~ diamèter CH~MICAL ANA~YSIS: CATALYST
-10 CoO, wt. ~ 2.g3 MoO3, wt~ % 16.25 Na2O, wt. % 0.03 CaO, wt. ~ 0.01 MICROPORE ANALYSIS: CATALYST
Pore volume in pores having diameters between 600 Angstrom units and 580 Angstrom units .0004 cm.3/g.
560 .0008 540 .0012 520 .0016 500 .0025 460 .0042 440 .0051 420 .0059 400 .0072 380 .0086 36~ .0099 340 .0112 320 .0120 300 .0153 280 .0176 260 .0211 ,~ . " . , ~ , 1163~

240 .0253 220 .0317 200 .0381 180 04~0 150 .1024 140 .1356 130 .1734 120 ~2400 110 .2959 100 .3696 .4458 .5173 ~0 .5675 .5716 Total micropore vol., cm.3/g. .57 Pore volume median 112 micropore diameter, A
Minimum pore diameter 60 20 MACROPORE ANALYSIS: CATALYST
Pore volume in pores having diameters between 10,000 Angstrom units and 9000 Angstrom units . .0000 cm.3/g.
8~00 . ,~ooo 257000 .0030 6000 .0159 5000 .0376 4009 .0665 3000 .0918 302000 .1090 1000 .1291 700 .1372 600 .1413 Total macropore vol., cm.3/g. .14 :

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Example 3 Extrudates were formed by placing 10.0 pounds of a pseudoboehmite-boehmite inte~rmediate, as disclosed in the Sanche2 et al Patent No. 4,154,812, into a Simpson Mix Muller made by the National Engineering Co. of Chicago, Illinois. The muller was started and during the first 10 minutes, 4,000 ml. of di~tilled water was added. The mixinq and mulling operation was continued for a total of 45 minutes. The collected material was then sent through an Auxiliary Worm Extruder made by the Welding Engineers Inc. of Norristown, Pennsylvania. The die had openings of 1/16 inch, and it was operated at a torque of 20-28 pounds. The material extruding fro~ the die holes was cut into lengths of about 3/16 inch, and these extrudates were oven dried overnight at a temperature of 220F 1104C). After oven drying, the ma~erials exhihited a moisture content QE 33 weight percent. The dried extrudates were then calcined at a temperature of l,100F (593C) for 4 hours. The final products obtained had the following properties:
Psre volume as measured by water ~cm.3/g.) 0.91 Total volatiles ~) 26.59 Crush strength tlb--force/mm.) 1.6 Bulk density (g./cm.3) 0.5359 5urface area ~m.2/g.) 187 Mercury pore volume above 600 ~ ~cm.3~g.) .155 Pore volume median micropore dimeter ~R) 123 Minimum pore diameter ~) 80 Tot~l micropore pore volume (cm.3/g.) .71 % oE total pore volume above 600 R 17. 9 1 1~3614 Example 4 Another batch of extrudates was made following the procedure in Example 1 above. In this case 9.5 pounds of the alumina powder was mixed for a total of 70 minutes in the Simpson Mix Muller with 4,150 ml. of distilled water. The torque was at 23-25 pounds and the product was dried and calcined as in the procedure of Examplè 1.
The product had an average length of .148 inch and the following properties:
10 Pore volume as measured by water (cm.3/g.) 0.83 Total volatiles 28.42 Crush strength (lb.) 1.7 Bulk density (g./cm.3) 0.5655 Surface area (m.2/g.) 192 15 Mercury pore volume above 600 ~ (cm.3/g.l .103 Pore volume median micropore dimeter (~) 126 Minimum pore diameter (~) 80 Total micropore pore volume (cm.3/g.) .708 % of total pore volume above 600 ~ 12.7 ExamPle 5 In this example the starting alumina was a mixture of aluminas as disclosed in the Sanchez et al Patent No.

4,154,812. From this mixture 10.0 pounds was added to the Simpson Mix Muller as in the procedure of Example 1, with the addition of 4,150 ml. of distilled water. The ~ulled material was very wet. It was extruded at a tor~ue of about 15 pounds to an average length of .148 inch and the particles were dried and calcined under the conditions set forth in Example 1 above. The calcined 3Q extrudates had the following properties:
Pore volume as measured by water ~cm.3/g.) 0.96 Total volatiles 26.8 Crush strength (lb.-force/mm.) 1.5 .~

11~361~
Bulk density (g.~cm.3) 0.4971 Surface area lm.2/9~) 215 Mercury pore volume above 600 ~ ~cm.3/g.) .187 Pore volume median micropore dimeter t~) 110

5 Minimum pore diameter (~) 60 Total micropore pore volume ~cm.3/g.) .711 % of total pore volume above 600 R 20. 8 ExamPle 6 ~he extrudates according to this invention have been made into a cobalt molybdenum catalyst identified as Amocat-lA, having the properties set forth below. This catalyst has been tested in liquifying Illinois No. 6 coal by ~ydrocarbon Research Incorporated (HRI) in their H-Coal Bench Scale Unit. A comparison was also made with the standard catalyst for the H-Coal Process, HDS-1442A, which is an American Cyanamid alumina catalyst in the form of a 1/16 inch extrudate.
The two catalysts have the following characterization.
Composition APD SA PV lOOOA+ ABD
wt. % - Pores 15 MoO3 CoO A m~2/g cm 3/9 total g~/cm.
PV
HDS-1442A 13.2 3.1 58 323 .64 28 .57 20 Amocat-lA 16 3.0 122 154 .60 11.1 .66 A comparison of the pore size distribution for HDS-1442A and Amocat-lA, designated Catalyst A,`is set forth in Fig. 1.
Preliminary test data is set forth in Table 4.

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Ta~le 4 HDS Amocat _ CatalYst -1442A -lA
Catalyst Age, g-coal/g-catalyst 141 138 Coal Conversion, Wt. % 93 7 94.0 524C~ Residuum -Yield on Dry Coal, Wt. % 26.0 21.8 Sulfur, Wt. ~ 0.46 0.`34 Nitrogen, Wt. % 1.71 1.51 524C+ Filtered Liauid Test Period 10 11 Viscosity at 232C, cps `~0,500 3,800 The Amocat-lA gave the most favorable product structure. The 524CI resid yield and sulfur content are the lowest with Amocat-lA. Note that the resid sulfur content is lower than that of HDS-1442A. For the desired 524C+ fraction of the filtered liquid, the viscosity data provides a measure of catalyst effectiveness in the conversion of higher molecular weight materials. The lower the viscosity value, the more the heavy coal molecules have been broken down into more easily flowable lower molecular weight hydrocarbon molecules. Here a significantly lower viscosity is achieved with the Amocat-lA catalyst.
ExamPle 7 In addition to evaluating the catalysts under the H-Coal Bench Scale Unit, they can also be evaluated in a batch screening unit which measures initial catalyst performance.
Since it is desired to convert coal to a high quality boiler fuel for power generation which has a }ow ~ulfur content, an improved catalyst should have a high liquefaction-desulfurization activity and good aging , ' .

1~6~6~4 characteristics. Aging behavior is an important consideration for coal liquefaction catalyst. High initial activity may rapidly decline under the relatively severe liquefaction conditions due to various deactivation mechanisms, such as coking, sintering, and ash deposition.
One aging test involves subjecting the catalysts to continuous flow for 150 hours in a pilot plant. The results are evaluated for the liquefaction conversion, particularly to benzene soluble materials, the amount of desulfurization, and the product hydrogen content as measured by the atomic H/C ratio.
In this test four cobalt molybdenum catalysts are compared in the form of lfl6 inch extrudates. Three have a bimodal distribution with a certain amount o macropores greater than 1000~. HDS-1442A is an American Cyanamid alumina catalyst having small pores. Catalyst A
is made from an extrudate according to the present invention with the median diameter of the micropore volume being 120 An~strom units. Catalyst B is a catalyst similar to Catalyst A but made from an extrudate where the median diameter of the micropore volume is 200 Angstrom units. The last catalyst, Catalyst C, is a monomodal alumina catalyst made from Xaiser alumina designated KSA Light . This Catalyst C is characterized as monomodal since it has only about 4 percent o ehe total pore volume in pores of 1000 Angstrom units or larger. This particular catalyst also has had phosphoric acid applied to aid in impregnating the extrudate with the catalyst metals.
The four catalysts are characterized below in Table 5.
~' . --19--1183~1~

Table 5 Major lo~OA~
APD SA PV Pores Pores ABD
Catalyst A m.7q. cm~3/~. A Vol.% g.~cm.3 HDS-1442A 58 323 .6420-140 28 0.57 Catalyst A111 162 .6270-200 17 0.68 Catalyst B183 91 .53lOS-350 18 0.73 Catalyst C105 195 .7050-250 4 0.59 where A~D - average pore diameter SA z surface area PV = total pore volume ABD = average ~ulk density Coal conversion to benzene solubles is plotted versus ti~e on stream in Figure 2 for the four CoMo-alumina catalysts which are differentiated by average pore diameters and pore size distribution, The c021 conversion is expressed in "% maf n which is on a moisture and ash free basis. Compared to the reference HDS-1442A which has about 60~ average pore diameter, both the bimodal Catalyst A and Catalyse B catalysts increased the benzene soluble conversion oE these two superior catalysts, the larger pore size bimodal Catalyst B bas lower conversion. Next in performance is the HDS-1442A
catalyst and last is Catalyst C, which starts out with a high conversiOn. but rapidly declines to the thermal level in spite of its large avera~e pore diametero ;

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Claims (13)

WHAT IS CLAIMED IS:

1. A bimodal pore size alumina extrudate suitable for use as a catalyst support having a substantial micropore volume made of relatively small pores having a pore diameter of less than about 200 Angstrom units and greater than about 8 percent of the total pore volume being a macropore volume made of relatively large pores having a pore diameter greater than about 600 Angstrom units, said extrudate having a crush strength of greater than 1.5 pounds per millimeter when measured on extrudates having a diameter of 1/16 inch.;
a surface area of about 170-220 m.2/g. as measured by nitrogen porosimetry;
a micropore volume, based on nitrogen porosimetry for pore diameters of 600 Angstrom units or less, of about 0.65 to 0.89 cm.3/g.;
a macropore volume, based on mercury porosimetry for pore diameters greater than 600 Angstrom units, of greater than or equal to about 0.08 cm.3/g.; and a pore volume median pore diameter, based on nitrogen, of 110-150 Angstrom units.

2. The alumina extrudate of Claim 1, wherein the article is in the form of an extrudate having a ratio of length to diameter in the range of about 1 to 1 to about 5 to 1.

3. The alumina extrudate of Claim 2, wherein the article is in the form of an extrudate having a ratio of length to diameter in the range of about 2 to 1 to about 3 to 1.

4. The alumina extrudate of Claim 2, wherein the diameter of the extrudate is about 1/16 inch.

5. The alumina extrudate of Claim 1, wherein the pore volume median pore diameter is in the range of 110 to 130 Angstrom units.

6. The alumina extrudate of Claim 1, wherein the pore volume median pore diameter is about 125 Angstrom units.

7. In a method of producing a pure transition alumina extrudate suitable for use as a catalyst support for coal liquefaction, having a crush strength greater than 1.5 lb/mm when the extrudate is 1/16 inch in diameter, and a surface area in the range of about 170-220 m2/g when measured by nitrogen, porosimetry, and a substantial first volume made of relatively small pores having a pore diameter of less than about 600 Angstrom units, and a second macropore volume made of relatively large pores with a pore diameter greater than about 600 Angstrom units, wherein an alpha alumina monohydrate powder, which is an intermediate between boehmite and pseudoboehmite, is initially mixed with water to form a mixture having a solids content in the range of 36-42 weight percent to form a paste which is then extruded to form extrudates which are dried and calcined, the improvement comprising mixing said powder and water until the material forms a coherent ball when squeezed by hand, and calcining the extrudates at a temperature in the narrow range of 900-1,200°F
to obtain an alumina extrudate having a first pore volume, as measured by nitrogen porosimetry for pore diameters of 600 Angstrom units or less, of about 0.65 to 0.89 cm.3/g.;

a second pore volume, as measured by mercury porosimetry or by water adsorption for pore diameters above 600 Angstrom units, of greater than or equal to about 0.08 cm.3/g.; and a pore volume median pore diameter, based on nitrogen porosimetry measuring pore diameters of less than about 600 Angstrom units, of 110-150 Angstrom units.

8. The method according to Claim 7, wherein the solids content of the mixture prior to extrusion is in the range of 36-40 weight percent.

9. The method according to Claim 7, further comprising tumbling the extrudates before drying to round the ends and reduce any edge irregularities so as to render the extrudates less susceptible to attrition.

10. The method according to Claim 7, wherein the length to diameter ratio of the extrudates is about 1 to 1 to about 5 to 1.

11. The method according to Claim 10, wherein the length to diameter ratio of the extrudates is about 2 to 1 to about 3 to 1.

12. The method according to Claim 7, wherein the extrudate is calcined to produce a pore volume median pore diameter which is in the range of 110-130 Angstrom units.

13. The alumina extrudate of Claim 12, wherein the pore volume median pore diameter is about 125 Angstrom units.