mfety in the
edited by MALCOLM M. RENFREW University of l d a b Moscow. idab 83843
Group Contribution Method for Predicting the Potential of a Chemical Composition To Cause an Explosion William H. Seaton 1329 Belmeade Drive, Kingsport. TN 37664
As the chemical industry has grown both in volume of production and in complexity of operations, it has become increasingly important for practicing chemists and chemical engineers to recognize potential hazards in the processes they develop for commercial use. This means that teachers in our colleges and universities have an obligation in professional courses to develop an alertness for the unexpected and to provide bases for anticipating hazards. Here is an empirical method that will be helpful in the training of students to avoid physical disaster in their subsequent working experience. In the chemical processing industry, the view is widely held that if a chemical or mixture has the potential to cause q explosion, then swner or later the right conditions will come along. Since accidental explosions are often costly and dangerous, it is clearly desirable to know when a chemical or mixture has this potential. For the purposes of this article, let us call such a composition a "plosive" chemical or mixture. It follows that a composition that cannot be made to cause an explosion, even if it is subjected to a severe impact, is a "nonplosive" chemical or mixture. More than 50 years ago, it was recognized that certain groups of atoms are able to impart plosive character to molecules (I).Later, Lothrop and Handrick (2)gave the name "plosopbore" to a group of atoms that, on substitution into a hydrocarbon, is capable of forming a plosive compound. They termed "auxoplosive" that variety of suh-
stituent groups that do not by themselves produce plosive molecules hut that may be expected to alter explosive properties. Ex-
I
I
perience has shown that compositions that containplosophoricgroupscanbe dilutedto the point where the composition is no longer
Editor's note: We have received from Gary Allison, President of Desert Assembly, Inc.,ILd Eugene Road, I'almSpringa, CA 92'264, aslatement on eyewash stationsasa supplement to Walters, el al. on page A199 of our August 1988 issue. Allison's company provides a faucet-mounted eyewash station that reduces water flow to prevent a presauresuqe, thus countering an objection hy the authors tn such units (in addition countering the statement that they do not meet ANSI Requirements of 2358.1-1981. which he holds that they do). He also feels that the authors fail tn appreciate fully the benefit of locating the eyewash station a t a sink where victims of a solash can easilv locate it. MMR
I
I
(Continued on page 138)
graduated wim how Wllllm H. *.Ion ors hom lha University of Arkansas in 1950. After thee yssrs wim Monsamo, he returned to schwi and received his PllD -d in Chemical Engineering hwn The Ohio State Uniwslty in 1958. F a 25 years before his retirement in 1986, ha was the deparlmenl head of a design data service of me m t m n Chemicals Division. During *is time he helped found me Design institute tw Physical Woperty Data. He has bean a member of lha American Society fw Testing and Materiais for many years and ha continues 10 serve as an active membet of Committee E-27. On Hszard Pnenliai of Chemicals. Seaton is a Fellow of me American instihaw of Chamicai Engineers, and he is a Fellow of lb American Sociery tw Testing and Matwials. He and his wife. the f o r m WOW Lee Ward. reside In Kings+?&.Tennessee. Volume 66
Number 5
May 1989
A137
08ZC 18'PL
00'0
OO'LC CZ'SL 88'02 20'8s 6S'P EI'E28'61 CE'SC
PE'C OL'CZ
01'2 SL'L 6C'PCC'P60'26E'ILE'E ZSO-
Table 2.
Error Data for Several Classes of Compooillons
Class of CMllposiIion P I ~ ~ Compositions ~ V B with
Nio or Nium groups Nonpiosive Compositlans with Nib0 or Nitroso groups Plosive Compositions with Peroxide w Hydroperoxide
Total Number of Campilions
Percent of Compositions Classified Conectiy
124 69 37
95.2 95.6 94.6
26
96.0
5 16
100.0 93.7
Example Problem No. 2 Compute the classification ratio of a mixture that contains 1.00 mol of acetic anhydride, 1.04 mol of nitric acid, and 0.15 mol of water, and then compare it to R, to decide if the mixture issensitive to severe impact (see Tahles 4.. 5.. and 6). Since R. is less than RP. .. we conclude that this is a nonolosive comoosition. This conclusion is consistent with experimental results ohmined using the Egly test at the Eastman Chemicals Division.
coup Nonpiosive CMllpsitions with Peroxlde w Hydroperoxide
soups Piosive Cornpitions with aikyne struchres Nonpiosive Compositions with aikyne strucMes
and then compare it to R, to decide whether it is a plosive or a nonplosive compound (see Table 3). Since R, is greater than R,, we conclude that T N T is a plmive compound.
~~~
Table 3. 2nbOrder groups
in this moiecuie
2.4.8-Trlnltmtoluene. Molecular Welaht = 227.13
Number of this group in lk molecule
Plosophaic weight of this gmup
3 . 1 1
C.iC) C(CeXHk Sum of piosophoric auxapioslve weights Totel weight of composition & = 118.611227.13 = 0.522 classification ratio and designate it as R,. If
R, is greater than or equal 6 the minimum value for a plosive composition, R,,we will
classifv the comwsition as dosive. If R, is less t h k R,,we klclassify the composition as nonplosive. The activities of ASTM Subcommittee E27.07 include the development and standardization of computational methods for estimating the energy hazard potential of chemicals arising during their manufacture, transport, storage, or use. The results reported here are part of a continuing project todevelop one of eight energy hazard potential criteria that will be used by version 6 of ASTM computer program CHETAH (3). This program can be used, in advance of synthesis, to classify a chemical or mixture as plosive or nonplosive, and it can also be used t o estimate chemical thermodynamic data. Proeram CHETAH uses the method of ~enson"andBuss (4) ro estimatechemrcal thermodynamic dam, so for this reason the group contrihutiun method described here uses 2nd-order groups that are consistent with the 2nd-order groups defined by these authors. To enable its work, Subcommittee E27.07 has acquired a substantial database of chemicals and mixtures that have been classified as plosive or nonplosive according to experimental results from a severe impact test such as the zero Card Gap test (5)or the Egly test (6).For this project, a value of 40.0 was set arbitrarily for the plosophoric weight of the 2nd-order group, C d N O d . Compositions from the database were then used with essentially trial-and-error methods to determine that Rp = 0.265 and to determine the plosophoric and auxoplosive weights that are presented in Table 1. A prediction by this method that a composition is plosive will have a high prohahility of being true. On the other hand, a prediction that a composition is nonpolosive may only mean that no value was provided for a plosophoric or an auxoplosive group that happens to be present in the eomposition. Furthermore, it must he remembered that this method has no rigorous theoretical ba-
40.00 .... 0.00 0.00
Auxoplosive weight of this group
T m i P8A
weight of this group
Example Problem No. 3
120.00 0.00
-1.39
.
~
-1.39 118.61 227.13
sis so, even when all significant groups are available, it may still provide an erroneous condusion. Nevertheless, it is believed that in many cases this method can forewarn the user of the potential of a composition to cause an explosion. Error statistics are presented in Table 2. Three example problems are given below. Example Problem No. 1 Compute the classification ratio of T N T
Compute the classification ratio of a mixture that contains0.59 molof tert-butyl peracetate and 0.32 mol of benzene, and then use R, to decide if it is a plosive or a nonplosive mixture (see Tables 7 and 8). Since R, is greater than Rp, we conclude that this is a plosive composition. This conclusion is consistent with experimental results obtained using the Egly test at PPG Industries. Acknowledgment
The author gratefully acknowledges the encouragement and support provided by Trueman D. Parish (Eastman Chemicals Division), without which this project would not have been undertaken. The assistance of J. Edmund Hay (U.S. Bureau of Mines) with the identification of many important (Continued on page A140)
Volume 66
Number 5
May 1989
A139
Energi RelEvaluationProgram"; ASTM Date Scriea Publication DS 51: h e r i m Society for Testing and Material. 1916 Race Street, Philadelphia, PA 19103.1974.
plosive groups, was much appreciated.
.
3. Ssaton,W. H.; Freedman, E.;Treweek. D.N. THE-
TAI-The
ASTM Chemical Thedynamie and
Aceib Anhydride. Molecular Welght = 102.109
Table 4.
Number of this group In me molecule
2QWWS In this molecule
Ploaophorlc weight of this group
UCOXHh WCW)
2 0.00 2 0.00 Wmh 1 0.00 Sum of plosaphorlcand auxoploslve welghts for this molecule
Number of this ~ o u In p the molecule
PIosophorIc weight of this n o u ~
0.00 0.00 0.00
0.00 0.00 0.00 0.00
A~~optosi~e weighl of this WWD
Nltrlo Acid 1 32.80 S u n of ploaophaic and auxwloslve w e i m for this molecule
0.00
Total PBA weight of this OTOUD 32.80 32.80
Water, mplecular welghl = 18.02
Table 6. Number of this group In me molecule
Molecule
Total P&A weishl of this soup
NHrlc Acld, Molecular Welghl = 63.10
Table 5.
Molecule
Auxoploslve weight of this group
Ploaophorlc welght of this group
A~~oplosive weigm of this group
Total P&A weight of mi6 grwp
Water 1 0.00 -17.41 -17.41 Sum of .~ I o w. h o r I and c BUX~P w~ s i~m~for IV thisBmolecule -17.41 Total of plosophorlc and auxo&4ve wefghts = sum of (moles X welgMlmole) = l.Oo(O.00) 1.04(32.80) 0.15(-17.41) = 31.50 T m l welght of urmposhlon = sum of (moles X molecular weight) = 1.0q102.09) 1.04(63.10) 0.15(18.02) = 170.42 & = 31.501170.42 = 0.185
+
~
+
~~~
+
Table 7.
mdader groups h this molecule
t&Butyl
Peracetate, Molecular WelgM
Number of this group In me molecule
CiCNHh CWCNO) C-(COXHh cic)a(o)
~ioaophoric weight of this group
0.00 0.00 1 0.00 1 0.00 o-(com 1 38.02 o-(cNo) 1 19.82 Swn of plosaphorlcand auxoploslve weights f a thls molecule I
2nbOrdBr groups In this molecule
= 132.15
~uxoplosiwt weight of this soup
3
Table 8.
+
0.00 0.00 0.00 -0.52 0.00 0.00
Number of thls group In W.3 moleoule
Plosophorlc weight of this group
Auxopfoslve weight of this group
~
+
+
Journal of
0.00 0.00 0.00 -0.52 38.02 19.82 57.33
-
Benzene, Molecular Welght = 78.11
c&) 8 0.00 0.00 Sum of . plosophwlc and auxoploslve weights f a this molecule Total of ploaophwlc and auxo~loslvewelghts = sum of (moles X welght/mole) = OSS(57.33) 0.32(0.00) = 33.82 Total welgM of wmposltlon = sum of (moles X molecular weight) = 0.59(132.15) 0.32(78.11) = 102.98 & = 33.821102.98 = 0.328
A140
~ o t aPM l weight Ot this group
Chemical Education
Total P&A welght of this group
0.00 0.00
