Catalytic activity of mineral matter from western Kentucky coals for hydro-desulphurization and hydrodenitrogenation

Catalytic activity of mineral matter from western Kentucky coals for hydrodesulphurization and hydrodenitrogenation Yusaku

Sakata*

and Charles

E. Hamrin,

Jr.

Department of Chemical Engineering and Institute for Mining University of Kentucky, Lexington, KY 40506, USA (Received 1 June 1982)

and Minerals

Research,

A pulse reactor was used to study the catalytic activity and selectivity of mineral matter from Kentucky No.9 and No.1 1 seam coalsand a low calorific value gasifier ash in the hydrodesulphurization (HDS) of thiopheneand hydrodenitrogenation (HDN) of pyrrole, pyrrolideneandn-butylamine. Mineral matter in its least altered state was obtained by low temperature ashing. Thiophene conversion correlated well with the iron and zirconium contents (R > 0.95) of the catalysts, and at 450°C all catalysts including a commercial Fe,O,/AI,O, gave similar distributions of the butenes and ~5% butane. Reactivities of Ncompounds catalysed by mineral matter from Kentucky Nos.9 and 11 coals were in the order: nbutylamine > pyrrolidine > pyrrole ~0. Nickel was found to be the important element in n-butylamine conversion and 1 -butene was the predominant product species for all the catalysts. Mineral acid treatment of the mineral matter from No.1 1 coal decreased its HDN activity but increased its HDS activity. Results of this study indicate that hydrogen consumption for removal of sulphur and nitrogen can be reduced by using dehydrogenation-type catalysts. (Keywords: coal; catalysis; mineral matter; hydrcdesulphurization;

It has been reported that low temperature ash (LTA) from coal, which represents coal mineral matter in its least altered state, exhibits fairly good catalytic activity for the hydrodesulphurization (HDS) of thiophene, a model coalsulphur compound’. Later the HDS of thiophene and hydrodenitrogenation (HDN) of pyrrole, pyrrolidine, and n-butylamine were carried out over six kinds of clays, which are typical of those in mineral matter, using a pulse reactor technique. Total conversion and selectivity of the five C4 products were determined by gas chromatography. A least-square fit of the conversion data against the relative X-ray fluorescence (XRF) spectra of each element in the clay showed that iron was responsible for HDS and the Al/Si ratio and titanium were most important for nbutylamine HDN2. In this Paper these procedures will be extended to LTAs from Western Kentucky No.9 and No. 11 coals, bottom ash from a low-CV gasifier, and a commercial Fe,O,/Al,O, catalyst. Also the relative activity of pyrite (FeS,) which occurs naturally in most coals and pyrrhotite (FeS) which is produced from pyrite in all liquefaction processes will be determined.

hydrodenitrogenation)

Basically the system consisted of a gas supply and metering system, a pulse reactor in a furnace, and a gas chromatograph’. Total conversion of S and N reactants to C, compounds and selectivity for each C, product were calculated from the chromatography peaks. Before each run, 500 mg of catalyst was loaded into the reactor and treated with 6.32% H,S-H, gas (1.17ml (s.t.p.) s -‘) at 400°C and 0.1 MPa for 3 h. Gas flow was then switched to pure hydrogen and the reactor exit was connected to a gas chromatograph (pressure = 0.24 MPa). After stabilization, 3 to 5 pulses (1 mm3 each) of thiophene, pyrrole, pyrrolidine, and n-butylamine were successively injected into the reactor at 400°C. Temperature was raised stepwise to 550°C (as indicated in the Figures), the sequence of pulses being repeated at each temperature. This first procedure will be called the first run. Then the reactor was cooled quickly to 4OO”C,and the procedure repeated (second run). Table 1 Densities of catalytic samples, ash yields, and surface areas after activity testing (Kentucky No. 9 and NO. 11 coals)

EXPERIMENTAL

Sample

Experimental

No. 9 coal No. 9 gasif ier ash No. 11 coal (-80 Tyler mesh) No. 11 LTA, watertreated No. 11 LTA, acidtreated Fe203-AI203

system and procedure

A hydrogen carrier, pulse reactor system used for clay catalysts was used with minor modifications; a tank containing a 6.32% H,S-H, mixture was used for catalyst pre-treatment in place of metering the individual gases. *

Present address: Department University, Okayama 700, Japan

of Synthetic

OOM-2361/83/050508-lOS3.00 @ 1983 Buttenvorth & Co. (Publishers) 508

FUEL,

1983, Vol62,

Ltd

May

Chemistry,

Okayama

Apparent packing density (kgdm-3)

LTA yield (%)

HTA yield f%)

E HTA

0.94 1.21

16.6 96.4

13.2 94.9

1.25 1.02

5.6 1.0

1 .ll

29.2

25.8

1.13

27.8

1.07

-

-

-

29.8

1.05 1 .ll

-

-

-

46.5 59.7

Surface area (m2 g-t)

Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamin Jr. Tab/e 2 XRF intensities of samples LTA No. 11

Non-treated

Water-treated

LTA No. 9 Acid-treated gasifier

Non-treated

Gasifier ash

Low energy Al

Ra D S

1.7 1.7 1.6

1.6

1.6

0.8

1.2

4.2

Si

A D S

9.5 9.0 8.4

9.2

10.2

5.7

7.3

0.2

s

R D S

3.3 0.9 2.2

1.4

1.3

11.7

1.5

0

K

R D S

5.5 5.2 5.1

4.8

4.6

1.4

3.4

0

R D S

0.3 1.1 1.1

0

R D S

4.3 4.4 4.0

4.1

R D S

0.6 0.5 0.5

0.5

R D S

0 0 0

0

R D S

39.3 43.4 40.6

37.0

ce

Ti

Cr

Mn

Fe

4.1

0.3

9.6

0 0

20.3

0

17.7

0 4.7

2.4

0

3.2

0 0.4

0.3

0.6

0.4

0.2 0

0

0.9

0

0.6 31.5

79.6

132.9

171.9 135.5

High energy 64.4

Fe

R D S

82.9 90.4 87.2

78.9

Ni

R D S

1.4 1.4 1.3

0.3

0

0.3

0

0.3

Cu

R D S

1.0 1 .o 1 .o

0.7

0.6

0.5

0.5

0.9

R D S

1.4 1.5 1.4

0.4

R D S

0.2 0.2 0.2

0.3

R D S

0 0 0

0

R D S

0.5 0.5 0.5

0.5

Rb

R D S

5.31 4.6 6.1

5.9

Sr

R D

Zn

Ga

Ge

As

Zr

190.3

328.9

431.0 328.6

0.3

0.8 0.3

2.0

0.6

1.8 1.8

0.2

0

0

0.2 0.1

0

0

0

0 0

0.5

0.8

0.5

0.6 0.4

5.2

1.8

2.0

0 0

1.8

S

13.6 2.9 4.0

R D S

5.6 4.5 6.5

6.5

1.3

2.9

2.7

5.3

3.5

3.9

0 0 0 0

a R, Before treatment; D, after decomposition in He; S, after treatment in 1% H2S-He

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Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamin Jr. Sample preparation

Samples of mineral matter in its least altered state from Kentucky Nos. 9 and 11 seam coals were obtained by low temperature ashing in an RF-generated oxygen plasma. For handling convenience the ash was die-pressed under 3.3 MPa for 2 min, crushed and sieved to -24 +42 Tyler mesh (average diameter =0.533 mm). Bottom ash from a low calorific value gasifier that had been converting Kentucky No. 9 coal was crushed to the same size. Low temperature ashing caused a weight loss of only 3.6%. Other physical and chemical properties of this material have been presented by Schrodt et ~1.~ A summary of apparent packing density, LTA yield, HTA yield (750°C for 3-4.5 h in air) and the LTA/HTA ratio is given in Table I. A commercial Fe,O,/Al,O, (Harshaw FE 0301Tj 0.125in cylinders) catalyst was used as a reference material after crushing and sieving to - 24 + 42 Tyler mesh. All samples were dried at 110°C in uacuo before activity testing. Dried samples of No.1 1 LTA (Z 10 g) were heated at 95-98°C under reflux for 3 h in both 5% HCl and water. The liquid-to-solid ratio was 2:l in both cases. After cooling in an ice bath to < 5O”C, the slurry was filtered,

the residue was washed in 500 ml of hot water for 15 min and the suspension was refiltered. Washed LTA was then dried at 110°C in uucuo. Weight losses by the acid and water treatments were 24.7 and 13.2%, respectively. X-rayfluorescence

(XRF) analysis

give absolute not calibrated to Although concentrations, the XRF data are quantitative indicators of the elements detectable*. A Finnigan Corp. Model 900 XRF analyser was used under the following conditions: atomic number 12 to 26-14 kV, 0.4 mA, vacuum path, 3 mm collimator, no filter, 1000 s counting time; atomic number 26 to 42-40 kV, 0.8 mA, air path, 3 mm collimator, Rh filter, 1000 s counting time. In addition to the XRF data for the samples before any treatment, designated in Table 2 by R, analyses after decomposition in flowing He for 15 h at 450°C are denoted by D and those after treatment in 1% H, S-He at 450°C for 3 h by S. Surface area determination

Surface areas of catalysts after activity testing were measured by low temperature nitrogen adsorption at five pressures using a Micromeritics Digisorb 2500. Samples

Kentucky

I

30 28 (degrees Figure I

510

I

I

40

50

No9

1

X-ray diffraction patterns of LTA No.9 and No.9 gasifier ash before and after HDS and HDN activity testing

FUEL, 1983, Vol 62, May

Gaslfierash

-_

60

Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamin Jr.

64

60

40

30 28 (degrees)

X-ray diffraction patterns of LTA No.1 1 in four states: (l), as prepared;(2), decomposed; (3). sulphided after decomposition; (4). after I-IDS and HDN testing

Figure 2

were outgassed at 523 K in uacuo (0.13 Pa or less) for 4 h before adsorption. Results are given in Table 2. X-ray diffraction

(XRD)

analysis

XRD analyses were made to determine the crystalline minerals present in the LTAs and the bottom ash and detect any changes occurring as a result of pretreatment and catalytic testing. Samples were spread in a thin layer on two-sided adhesive tape, which was attached to a glass slide. A General Electric Model XRD-5 instrument was used under the following conditions: CuKa, Ni filter, 50 kV, 15 mA, 200 counts s-l, time constant-4 s, and scanning speed 2”(28)min-‘. ASTM diffraction data4 were referred to for peak identification. RESULTS Mineral

AND DISCUSSION

matter in LTA

The XRD patterns given in Figures I and 2 indicate the presence of quartz (Q), calcite (C), pyrite (P), kaolinite (K)

and illite (I) in raw LTA of No. 9 seam coal, and Q, K; I and P in raw LTA of No. 11 seam coal. The major peaks are indicated by asterisks. The raw LTA of gasifier ash of No. 9 coal gave three sharp peaks, which are not positively identified, although the XRF results shown in Table 2 suggest compounds containing Fe, Ca and Si. After catalytic testing both LTAs and the gasifier ash show the presence of pyrrhotite (Ph) and the L’FAs also indicate the disappearance of kaolinite, which was reported earlier2. Decomposition

and sulphidation

LTA of No. 11 seam coal was treated in helium flow at 45O”C, for 15 h. By this treatment most of the pyrite was changed to pyrrhotite, and kaolinite peaks were eliminated. Subsequent treatment with 1% H,S-He mixture gas at 450°C for 3 h, however, showed pyrite peaks present again. These results are consistent with the significant changes of XRF sulphur spectra intensity shown in Table 2. The XRD patterns of Fe,O,/Al,O, catalyst showed pyrite formation from haematite clearly

FUEL,

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Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamin Jr.

same phenomenon is apparent for the Fe,O,/Al,O, catalyst as shown in Figure 4. Cracking to smaller hydrocarbons from C,-C, was negligible below 475°C so it cannot account for the decrease in conversion. A possible explanation might be the blocking effect of strongly chemisorbed NH, spcies, which was reported by Amenomiya’ for the isomerization of 1-butene. Since HDN by six clays was found proportional to aluminium contents and alumina was found to be an effective HDN catalyst2, this blockage of effective alumina sites by nitrogen compounds might be occurring. Reactivities of the N-compounds catalysed by LTA No. 9 and LTA No. 11 are in the same order found for the clays:

18-

D 126 3 5 is I ‘O-

C-C-C-C-NH2

E p 9P 2

8-

b

7-

$

6-

! 8

5-

qq-” H

This

order

agrees

with

the

order

of

increasing

7(

u” 4s 5

6(

3-

E $ ”

2-

E 0

lI

O-

350

1

I

400 Reaction

I

450 temperature

500 (“C)

1

550

C-C-C-C-N&

3 Total conversion for HDS and HDN reactions as a function of temperature. -, LTA No.9; ---, LTA No.1 1; 0, first run thiophene HDS; 0, second run thiophene HDS; 0, first run pyrrolidine HDN; A, first run n-butylamine; A, second run nbutylamine Figure

with the same 1% H,S-He treatment at 45O”C, but at 550°C with the same gas pyrrhotite (FeS) was identified. Catalytic

activityfor HDS and HDiV Total conversions to C, compounds for thiophene HDS and pyrrole, pyrrolidine and n-butylamine HDN catalysed by LTA of Nos. 9 and 11 coals are shown in Figure 3.

Conversion of thiophene increases with reaction temperature. For the first run with LTA No. 9 the value rises from 2.6% at 400°C to 17.4% at 550°C while the LTA No. 11 shows an increase from 2.8% to 12.6% over the same temperature range. At temperatures up to z 480°C LTA No.1 1 gives a slightly higher conversion than No.9 LTA but the opposite is true at 500 and 550°C. Another difference is noted on the second run. For LTA No.9 higher conversions were obtained at 400 and 450°C and about the same at 500 and 550°C for the second run. In contrast LTA No.11 yielded the same conversion at 400°C but significantly lower at the two higher temperatures. A consistent pattern of decreasing conversion for pyrrolidine and n-butylamine HDN with increasing temperature is apparent for both LTAs and the second run resulted in lower conversions for n-butylamine. The

512

FUEL, 1983, Vol62,

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I 400

,

l-l

I

I

450 500 Reaction tempemture

(“Cl

550

Figure 4 Conversion for HDS and HDN versus temperature for reference catalyst (presulphided Fe203/A1203). 0. A, first runs; 0, A, second runs. n , first run pyrrole; Cl, first run pyrrolidine

Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamin Jr.

indicate the presence of pyrrhotite after the catalytic runs with the LTAs. The effect is not found for LTA No. 11 because of the smaller amount of pyrite (see Fe content in Table 2) present in this ash. A comparison of all the catalysts used in this work is shown in Figure 5 for a temperature of 450°C. For the first HDS run the order of catalytic activity from the highest conversion to lowest is the following: Fe,O,/Al,O, > LTA No. 1l-WT > LTA No. 11 > LTA No. 9 > LTA No. 1l-AT > gasifier ash For n-butylamine HDN the order for catalytic activity on the first run was: LTA No. 11 > Fe,O,/Al,O,/Al,O, >> LTA No. 9 > LTA No. 1l-AT, LTA No. 1l-WT > gasifier ash An explanation for the order based on the second run results will be given later. It should be emphasized that catalysts were undergoing physical and chemical changes during the first runs as temperature was being increased so that the second run results were more representative of a stable state. Selectivity

Commercial HDS catalysts are basically good hydrogenation catalysts that are not poisoned quickly by sulphur. Wakabayashi and Orito’ reported the following order of HDS reactivity at 350°C for several metals: Ptz=-Pd,Mo>Ru,Cr,Co> Ni>Cu,V>Ag>Fe,W.As shown previously’ mineral matter species of clays are basically dehydrogenation catalysts and yield little butane. This is borne out for LTA No. 9 over the temperature range of 400 to 550°C for HDS as shown in Figure 6 and HDN as shown in Figure 7. At temperatures up to about 475°C the order of selectivity of HDS is: C = C-GC > trans-Zbutene c=c-C=c,c-C-C-C

z”

4ot-

F&m? 5 Summary of total conversion data for all catalysts at 45QC. 0, First run thiophene; 0, second run thiophene; A, first run pyrrole; A, second run pynole; V, first run pyrrolidine; v, second run pyrrolidine; 0, H, first and second runs n-butylamine

c= c-c-c

u

‘u H

equilibrim

constant

for {he reaction

a‘

C-C-C-C-NH2

2

C-C-C-C

+

‘*

--__

2

30

=,

~

<-

2 6

2

I?23 *-__

-_ c_pcc *---__*-- *

a 5

thermodynamic series6 :

> cis-Zbutene >>

c_!c’_c

i

NH3

A-----A---_

i-i

The higher conversion for the second HDS run with LTA No. 9 and the Fe,O,/Al,O, catalyst is attributed to the formation on the first run of pyrrhotite that persists on cool-down. It is a more active catalyst than pyrite, which is initially present at the beginning of the first run. Of course the closeness of the conversion at 500°C for the first and second runs indicates that the pyrite was already converted to pyrrhotite at this temperature on the first run. As noted earlier in Figures 1 and 2 the XRD results

Figure 5 HDS. -,

Selectivity of presulphided LTA No.9 for thiophene First run; ---, second run

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Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamin Jr.

Comparing the first and second runs particularly in Figure 6, one sees the increase in tram- and cis-2-butene, which indicates that pyrrhotite, formed by decomposition or reduction of pyrite, favours these compounds. At 450°C the striking similarity in selectivity for HDS by LTA No.9, LTA No.11, gasifier ash and Fe,O,/Al,O, is shown in Figure 8. In Figure 9 the preponderance of 1-butene for the same materials is the most obvious feature. Finally it is apparent from Figures 10 and II that pyrrolidine (hydrogen-saturated, five-membered ring containing N) and n-butylamine (hydrogen-saturated chain compound) give similar product distributions with 1-butene predominating, but these distributions differ from those from thiophene HDS. Such was not the case for the two clays, illite and montmorillonite2. To explain these results reaction schemes for HDN and HDS are shown in Figure 12. Two possibilities of nitrogen

20 -

10 -

o,

, 350

+!-*k./& 400

450

500

React Ion tempemture

I 20 Selectlwty

I 30 (%)

I

40

I

50

Figure 9 Comparison of selectivity of HDN for n-butylamine by four different catalysts, 450X, 0.24 MPa. 0, LTA No.9; A, gasifier ash; Cl, LTA No.1 1; W, Fe,O,/AI,O,

550

(“C)

Figure 7 Selectivity of C, components with presulphided LTA No.9 for the HDN of n-butalyamine. -, First run; ---,

c-c-c-c

second run

c=c-c-c

c-c:d-c

c-c-c-c

C-5=5-C C=C-C-C

c=c-c.c

C-$.C’-c

0

10

20 Selectlwty

40

30 (%)

50

Figure 70 Comparison of HDS and HDN selectivities for LTA No.9. 45o’C. 0.24 MPa. 0, Thiophene HDS; V, pyrrolidine HDN; Cl, n-butylamine HDN

c-,c=c,-c c.c-c=c

I

0

I 10

I

I

20 Sdectwlty

30

I

40

(%)

Figure 8

Comparison of selectivity for HDS of thiophene by four different catalysts. 45o’C, 0.24 MPa. 0, LTA No.9; a, gasifier ash; 0, LTA No.1 1; n , Fe203/A1203

For the temperature becomes :

range of 475 to 550°C the order

trans-Zbutene > C = CXX C=C~=C>C~~~

> cis-Zbutene >

From Figure 7 the selectivity for n-butylamine follows the order: C = C-C-C B- cis- and trans-2-butenes X= c-GC-C,c=c-C=c

514

FUEL, 1983, Vol62,

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I 0

HDN

I

10

I

20 Selectlvlty (%)

I

30

I

40

Comparison of HDS and HDN selectivities for LTA 11 No.1 1, 450°C. 0.24 MPa. 0, Thiophene HDS; 0, pyrrolidine HDN; 0, n-butylamine HDN

Figure

I

Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamrin Jr.

API reference clays, iron as an impurity was also found to be the most important element. The relation found in that study is shown in Figure 23 along with the correlation for the LTAs and gasifier ash. In addition data points for the acid and water-treated LTA No.1 1 and Fe,O,/Al,O, are shown. (The last point fits closely to an extrapolation of the LTA line: 13.7% at Fe = 172.) For the HDN of n-butylamine elements with positive coefficients and R >0.9 include Ni, Cu and Rb. It is suspected that at least one of these elements is responsible for the high conversion of LTA No. 11 when compared on the plot of Figure 14. Again the line was obtained for six clays. All the LTAs cluster within a narrow range of Al to Si. The sizeable decrease in HDN for the water- and acidtreated LTA No. 11 suggest that Ni is the active element

removal from n-butylamine are shown: hydrogenative denitrogenation to produce saturated butane (III-H) or dehydrogenative denitrogenation to produce butenes (III-D). It is proposed that the catalysts of this study (LTA No. 9, LTA No. 11, gasifier ash and Fe,O,/Al,O,) all promote the latter mechanism whereas CoMo/Al,O,, which showed an 88% butane selectivity for HDN (total conversion of 20%) and 37% for HDS (total conversion of 97x), operates according to 111-H’. Obviously further work with intermediates will be necessary to verify the existence of both these pathways or others for nbutylamine HDN. Ring saturation was found to be the most diflicult step in the overall sequence as reported by Satterfield et aL8. The HDS mechanism is that proposed by Owens and Amberg’. Many other investigators”-I2 have measured total conversion of HDS and HDN reactions but Beugeling et ~1.‘~ also measured product distributions. Correlation of conversion and element concentration

2

In addition to the minerals detected by X-ray diffraction minor constituents, impurities and substituted cations in the clays introduce many elements into the mineral matter. To test the correlation between HDS and HDN conversion and the elements detected by XRF, linear least-squares fitting was used for each element in Table 2 for LTA No. 9, LTA No. 11 and gasifier ash. The results are given in Table 3. For the HDS reaction most elements showed a negative coefficient except for Ca, Fe, Sr and Zr. Of these Fe and Zr both give values of R >0.95 indicating significance of these elements on conversion. In our previous work on six

14-

Fe,OJAI

45O”C, OWater

0

Figure I2

10

20

treated

,O,

1I+

239 kPa

No.11 (2nd)

40 50 60 70 80 90 100 110 120 Fe relatwe intensity by XRF(ccunts s-‘)

13C

Figure 13 HDS conversion versus iron content of the catalyata. 45VC, 0.24 MPa; A, R=O.995 for six clays, Ref.2; B, R=O.990 for LTA and gasifier ash

Reaction paths of HDS and HDN

Tab/e 3 Correlation between conversion and relative intensity of XRF spectra for LTAs and gasifier ash n-Butylamine HDN

Thiophene HDS Element

Coefficient

Constant

R

Coefficient

Constant

R

Al Si AIlSi K Ca Ti Cr Fe(L)’ FefHja Ni Cu Zn As Rb Sr Zr

- 3.33 - 0.751 -60.5 - 0.544 0.216 - 1.48 - 8.10 0.0766 0.0286 - 5.71 -18.7 - 0.876 - 4.30 - 2.71 4.62 13.2

11.4 13.0 17.0 9.19 4.58 12.3 10.9 0.805 1.62 10.2 18.1 8.25 9.85 13.8 4.60 40.5

0.426 0.393 0.350 0.308 0.647 0.385 0.335 0.990 0.988 0.881 0.847 0.201 0.219 0.632 0.549 0.995

22.6 5.37 467 4.59 -1.11 10.7 64.5 - 0.258 - 0.0973 23.1 78.6 - 4.60 -19.6 14.2 -26.5 -38.9

-11.9 -24.7 -58.8 0.0242 29.9 -20.0 -12.5 37.3 35.1 4.07 -29.4 20.5 27.2 -18.2 84.2 157

0.810 0.788 0.759 0.729 0.935 0.782 0.748 0.935 0.941 1 .oo 0.998 0.310 0.279 0.928 0.884 0.883

e L and H refer to low and high energy XRF analyses, respectively

FUEL, 1983, Vol82,

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Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamrin Jr.

30 -

0 LTA

No11

a 2 E x25E E _o >I 5 ? r

20-

h

0 0

l

0

0.1

LTA LTA

Gmfer

02 AI&

No 11 Water No 11 Acid

treated

treated

ash

03

04

f

by XRF

Figure 14 HDN conversion by LTAs and gasifier ash versus AI/S compared to clay correlation, 45(rC, 0.24 MPa. A, R=O.870 for six clays, Reference 2 I

I

I

I

400

450

500

550

Reactton

since only its concentration of the above three was lowered by these treatments. Dependence of HDS and HDN on the surface area was not found to be significant with R values of 0.18 and 0.54, respectively.

kmpzrature

(“C)

Figure15 HDS conversion versus temperature for non-, waterand acid-treated LTA No.1 1. A, A, first and second runs, nontreated; 0, 0, first and second runs, water-treated; 0, m, first and second runs, acid-treated

Treatment of LTAs

Mineral acid treatment has been widely used to increase the cracking activity of clays’4-‘6. Conditions used in this study were reported by Thomas, Hickey and Stecker l6 to remove Al, Mg, Ca and Fe from montmorillonite clays. From the XRF analyses given in Tabie 2 the reduction of sulphur is most dramatic for both treatments. Iron and nickel were reduced appreciably more by acid treatment than the water treatment. Calcium, zinc and strontium were reduced about equally by both treatments. None of these changes was detectable on the XRD patterns of the LTAs. The HDN activity after either treatment amounted to only 25% the original value as shown previously in Figure 5. More complex changes resulted in the HDS behaviour as shown in Figure 15. For the transient first run water-treated LTA gave a higher conversion at 450 and 500°C than the untreated or acid-treated LTA. The relatively constant conversion of x 3.3% by acidtreated LTA, which held over the temperature range of 400 to 550°C is certainly unexpected behaviour. For the second run a significant decrease in the activity of the water-treated samples is evident over the entire temperature range. In contrast the acid-treated samples show an increase in activity over the first run at 400 and

516

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450°C. In fact the highest conversions were obtained for these samples. Based on the stable second run results the LTA was activated by mineral acid treatment and deactivated by water treatment. In summary it may be concluded that the iron content of mineral matter in coal is the best predictor of thiophene HDS activity. The species responsible for the activity is FeS. HDN activity was highest for LTA No. 11 but decreased significantly for the water- and acid-treated samples. Of the three elements which gave good correlations for the untreated LTAs, Ni was reduced by both treatments thereby making it the most likely active element for HDN. Selectivity of the LTAs, gasifier ash and Fe,O,/Al,O, was similar for the HDS reaction with comparable amounts of the three butenes being produced. For n-butylamine HDN similarity of product distribution among the four was also found but the formation of 1-butene was predominant. Pyrrolidine HDN also favoured I-butene formation suggesting dehydrogenative denitrogenation by all the catalysts of this study in contrast to hydrogenative denitrogenation by a typical HDS catalyst such as CoMo/Al,O,. Finally mineral acid treatment of LTA No. 11 decreased the n-butylamine HDN activity but increased the thiophene HDS activity.

Catalytic activity of minerals from Kentucky coals: Y. Sakata and C. E. Hamrin Jr.

ACKNOWLEDGEMENTS The authors thank R. I. Barnhisel for helpful discussions and use of his XRD facilities, W. G. Lloyd and T. V. Rebagay for analytical work, B. Davis for surface area determinations, and K. Weaver and A. H. Johannes for experimental help. This work was supported by the US Energy Research and Development Administration (now US Department of Energy) under Contract No. EX-70-C-01-2233, which support is gratefully acknowledged.

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