10 The Thermal Cracking of Coal-Derived Materials R. S. BERNHARDT, W. R. LADNER, J. Ο. H. NEWMAN, and P. W. SAGE
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National Coal Board, Coal Research Establishment, Stoke Orchard, Cheltenham, Glos., GL52 4RZ, England
Many of the feedstocks for the chemical industry, espe cially aromatic hydrocarbons, were originally obtained as by-products from the carbonization of coal. (1,2) However, nowadays, most of these chemical feedstocks are derived from petroleum. Nevertheless, it is probable that, within the next few decades, the shortage of world reserves of petroleum will mean that BTX will once again have to be produced from coal, as will ethylene. It is, therefore, appropriate to examine ways in which these materials can be produced from coal; the present investigation was designed to study the formation of BTX and ethylene by the thermal cracking of coal-derived materials from the NCB coal liquefaction/hydrogenation processes. (3)
Experiemental Feedstocks - The vapors from the c a r b o n i z a t i o n of a b i t u minous, low-rank c o a l , an anthracene o i l , and a c o a l e x t r a c t i n anthracene o i l were d i l u t e d with n i t r o g e n and cracked; t h e i r product y i e l d s were compared with those from the c r a c k i n g of a p a r t i a l l y hydrogenated anthracene o i l and c o a l e x t r a c t s hydrogenated to various extents. The c o a l was Linby ( N a t i o n a l Coal
0097-6156/81/015 6-0225$05.00/ 0 Published 1981 American Chemical Society In Upgrading Coal Liquids; Sullivan, Richard F.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
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226
UPGRADING COAL LIQUIDS
Board, Coal Rank Code 802), and the e x t r a c t was prepared by d i g e s t i o n at 673°Κ and 8 bar i n anthracene o i l , f i l t r a t i o n to remove m i n e r a l matter and d i s s o l v e d c o a l , followed by d i s t i l l a t i o n under reduced pressure u n t i l the e x t r a c t contained about 70% c o a l . The two c o a l e x t r a c t hydrogenates were prepared by c a t a l y t i c a l l y reducing a d i l u t e e x t r a c t from Annesley (NCB, CRC 702) c o a l i n a t r i c k l e bed r e a c t o r and f r a c t i o n a t i n g the product. The f r a c t i o n s were f u r t h e r reduced i n a vapor phase r e a c t o r to give two h i g h l y hydrogenated l i q u i d s . Four model compounds, n-undecane, t e t r a l i n , c i s / t r a n s d e c a l i n and m e s i t y l e n e , and a n a t u r a l gas condensate from the North Sea were a l s o cracked. Analyses and the reference code key of the coal-based feedstocks and the gas condensate are given i n Table 1. P a r a f f i n , naphthene, and aromatic-type analyses were c a l c u l a t e d from gas chromatographic analyses of the p a r t i a l l y hydrogenated anthracene o i l and gas condensate; whereas, mass spectrometric a n a l y s i s was performed on the two c o a l e x t r a c t hydrogenates and t h e i r f u r t h e r hydrogenated products. Apparatus and Procedure - The experiments w i t h the s o l i d feedstocks and the i n i t i a l experiments on l i q u i d samples were c a r r i e d out i n the apparatus shown i n Figure 1A. The vapors from a s t a i n l e s s s t e e l , s t i r r e d - b e d c a r b o n i z e r / v a p o r i z e r at 873°K were cracked at atmospheric pressure i n a tube reactor heated i n a piatinurn-wound furnace. The r e a c t o r was 30 mm ID and had a 100 mm long hot zone w i t h i n 20°Κ of the maximum r e a c t o r temperature. S o l i d feedstocks were introduced at about 1 g min. * from a v i b r a t o r y t a b l e through a water-cooled port. L i q u i d s were i n j e c t e d at the same point from a mechanically d r i v e n syringe at 0.1-0.8 ml min. *. The amount fed was determined by weighing the feeders. L i q u i d products were c o l l e c t e d i n two glass traps at 258°K and i n a glass wool f i l t e r . The gas was measured i n a dry gas meter and sampled over mercury i n t o glass b o t t l e s . The r e a c t o r and c o l l e c t i o n t r a i n were weighed and the l i q u i d s removed w i t h a known amount of chloroform. The e f f e c t s of vapor residence time and c r a c k i n g temperature on the product y i e l d s from each feedstock were i n v e s t i g a t e d . The e f f e c t s of v a r i a b l e s such as r e a c t o r s u r f a c e , type and a r e a , feedstock vapor c o n c e n t r a t i o n , and the a d d i t i o n of steam was a l s o t e s t e d over a l i m i t e d range of c o n d i t i o n s w i t h a hydrogenated c o a l e x t r a c t . Gaseous and l i q u i d products were analyzed by chromatography.
In Upgrading Coal Liquids; Sullivan, Richard F.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
In Upgrading Coal Liquids; Sullivan, Richard F.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
N2
T/C
ο
s
T/C*
ο
γ
o
o
o
o
o
PRODUCT COLLECTION
ο ο
„CRACKER
N2
PRODUCT
^ SMALL CRACKCR
ZONE
.VAPORISATION
COLLECTION
T/C
Thermal cracking apparatus: a, carbonizer/vaporizer/cracker; b, small vaporizer/cracker
CARBONISER/ VAPORISER
ο-
Figure L
J
FEED INLET ^
Downloaded by UNIV OF PITTSBURGH on February 16, 2016 | http://pubs.acs.org Publication Date: June 20, 1981 | doi: 10.1021/bk-1981-0156.ch010
In Upgrading Coal Liquids; Sullivan, Richard F.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.
Β
Anthracene o i l extract of Linby coal
443 to 523
523 to 573
D
Ε
443 to 523
473 to 573
IBP to 623
Dl
El
F
Further hydrogenated coal extracts
Gas condensate
Hydrogenated coal extracts
IBP to 503
CI
573 to 673
C
0.3
6.0
ASH, a.d.
11.9
90.7
95.5
23.7
28.5
20.7
N.D.
NAPHTHENES
14.0
6.9
2.2
76.2
71.5
64.4
N.D.
AROMATICS + HYDROAROMATICS
18.1
2.4
2.3
0.1
0
13.2
N.D.
UNIDENTIFIED
50.5
39.1
V.M., d.a.f.
HYDROCARBON ANALYSIS, % W/W
N.D. = Not Determined
56.0
0
0
0
0
1.7
N.D.
PARAFFINS
DISTILLATION RANGE, Κ
Partially hydrogenated anthracene o i l
0.3
8.3
Analyses of Feedstocks
PROXIMATE ANALYSIS, % W/W MOISTURE, a.d.
210 to 350
210 to 350
SIZE, um
Anthracene o i l
LIQUID FEEDSTOCKS
A
KEY
Linby coal
SOLID FEEDSTOCKS
Table 1
85.1
86.9
86.4
89.6
89.4
88.2
90.6
88.7
82.4
C
14.4
13.0
13.2
9.4
10.1
10.7
6.9
4.8
5.3
Η
