The Importance of Analytical Techniques Illustrated by the Management of a Broad Catalyst-Testing Program E. E. STAHLY’, L. J. LOHR2, A N D H. E. JONES .Wellon Institute, Pittsburgh, Pa. Basic critical evaluation of available analytical tools is a necessary prerequisite to initiation of an industrial research program. Preliminary research into test and analytical procedures, as a logical approach to a field of investigation, is exemplified by the experiences introductory to a recent broad catalyst-testing program. The problems in the development of adequate routine methods prior to these studies in the “butadiene-from-ethyl alcohol” process demonstrate the prime importance of establishing a sound basic testing and analytical laboratory prior to launching a research pro,ject.
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led to establishment of a fellowship at Mellon Institute in 1944. (.kctual plant variations in yields were +=2Y0.) I t was requested that 1000 nevi catalytic combinations per year be tested as part of the program of studying methods for effecting improvement in the commercial yields of butadiene. h catalyst for which a 2% higher yield could be established would bring about a tremendous savings in a critical raw material-over 40,000,000 pounds of ethyl alcohol annually foi the three ethvl alcohol-butadiene plants.
EFORE any research project is undertaken, the aims of the sponsor, time limitations, and budget allotment must be viewed in the light of limitations of available tools. The adequacy of tools, both testing and analytical techniques, should be evaluated critically and if they are not compatible with the time and budget restrictions, the latter must be made more flexible or the responsibility for success should not be assumed. Stated conversely, testing and analytical techniques must be prime considerations in fixing the time and budget, never vice versa. Regardless of the urgency of the project-e.g., a problem pertaining to an operating commercial process-no sound and useful results are likely without adequate basic analytical procedures. Where the latter are inadequate, a more or less indefinite preliminary period of time must be stipulated for development of sufficiently accurate methods prior to initiation of the testing or development program. Although these statements are almost pedantic, it is the paramount purpose of this discussion to demonstrate their practicality and essentiality, for they are too often neglected. In many instances the analytical problems cannot be defined clearly in advance. In these cases the analytical needs crystallize as preliminary work proceeds. At some early stage a pause is required, preceding the initiation of a program of testing operatingvariable effects of the chemical reaction or process. The point which requires emphasis is that this pause, if for no other reason, is mandatory for establishing sound analytical methods. The ideal situation is that in which all preparatory analytical developments can he anticipated and solved beforehand. But, where this is not possible, there should be definite recess points where advance should cease until sound analytical data are certain. Often the development program is started under the assumption that analytical developments can be carried forward simultaneously. This too often leads to conflicting indefinite implications, misconceptions, and arguments, which in turn conduces t o expending excess effort and experimental work before harmful illfounded trends in thinking and doing can be eliminated. I t is indeed the exception when time is gained by not awaiting basic analytical development early in any research program, whether practical and fundamental. The number of possible interpretations of a mass of data from studies of operating variables is inversely proportional to the soundness of the analyses on which the data are based. An undertaking of a catalyst-testing program in the procesi for production of butadiene from ethyl alcohol is discussed herein t o exemplify the critical evaluation of test and analytical procedures which should precede acceptance of a project involving a large schedule of routines. Relatively low yields (about 63YO of theory) realized in operation of the Defense Corporation plants 1
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OUTLIYING NEW PROGRAM FOR BUTADIENE FROM ETHYL ALCOHOL PROCESS
The Carbide and Carbon process ( 3 ) for the manufacture of butadiene from ethyl alcohol was utilized to supply the major portion of the emergency requirements for this chief essential raw material in the production of synthetic rubber. In this process, part of the ethyl alcohol was dehydrogenated to acetaldehyde and subsequently ethyl alcohol-acetaldehyde mixtures were processed over tantala-silica catalyst at 350” C. a t about 7 seconds’ contact time. The over-all chemistry is represented as C2HjOH +C4Hs 2HjO (6, 8). Butafollows: CHsCHO diene was separated from the catalyzate and purified; unreacted ethyl alcohol and acetaldehyde were recovered and recycled. This process represents an achievement, because it was developed under stress and there was not sufficient time for development of analytical methods adequate for use in the usual routine laboratories. Relatively skilled technicians were required to obtain sound analytical data on which to base design considerations. For example, per-pass and ultimate yields of butadiene were established by quantitative formation and isolation of the solid tetrabromobutane; and the percentage of unconsumed ethyl alcohol and acetaldehyde depended on chemical analyses not specific for these constituents in the presence of certain by-products. These by-products in the converter effluents were not quantitatively separable by distillation, apparently because of azeotrope formations. The scope of the suggested catalyst testing program (1000 catalysts per year) together with budgetary considerations necessitated, first, an accelerated schedule of catalyst preparation and testing, and, secondly, analysis of materials by relatively untrained technicians because of the emergency shortage of technical personnel. Without good reproducibility of results, interpretations of activities of competitive catalysts might be misleading, Whether increases in yield of small percentages could be recognized had to be established by a preliminary critical examination of existing methods and procedures, in both testing and analytical work. The first step in evaluation of analytical methods was the establishing of quantities of materials to he handled. These quantities in turn were dependent on the equipment to be employed.
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Present address, Commercial Solvents Corporation, Terre Haute, Ind. Present address, General i n d i n e and Filin Corporation, Easton, Pa.
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V O L U M E 2 2 , N O . 2, F E B R U A R Y 1 9 5 0 Sr1vi.t ion of equipnicnt for the catalyst-testing portion of the program was based on practical considerations of time, personnel, nnd funds available; analytical requirements were then fixed by qu:intitiw of resultant materials and minimal ticc-urwies calcu1:itcvl :I< iircessary for precision of yield data.
273 on * lY0material balances leading t o the permissible or acceptable maximum of +2% reproducibility of the over-all test and analytical procedure. This *2% reproducibility represents the masiniuni limits of the variations in test data that would carry conviction in view of experienced variations in commercial monthly production figures.
SELECTION OF TEST EQUIPMENT AND PROCEDURE
Tli~ pi'iiiie considcixtions in the selection of equipment xvvi'e the volunie of new catalysts to 1)e prepared and the volume of liquefied r~fflue~irt available therefrom in :I run of practical duration a t the ci~nimei~cial feed rntes [0.1 to 0.6 liquid hourly space. vc,locity (1.h.s.v. I ] . Liter quantities of catalyst were feasible from t h r >t:indpoirit of prepitration and analysis of ten catalysts per week with eight t o ten persons. This permitted eight runs with 125 nil. of catalyst per test. From this amount (125 nil.) of catalyst, a 400-mI. volume of liquid products was obtainable in 8 hours a t a feed rate of 0.4 1.h.e.v. It was established that this volume of effluent was readily distilled with a laboratory column (12 to 18 platea) during one 8-hour n.0i.k period to give a practical separat ion of products into overlapping fractions containing, respect ivrly, butadiene, acetaltlchyle, and ethyl alcohol. Therrfcnre, 1:thoratory systems with a c:italyst capacity of 125 i d . were texns for preliminary critical r;elcc.ted from s c ~ e i o lavailable i,r~presentedI]>- the tlingrnm c~:~lculatioiis.Orie of t h ( w uiiit. slioivn in Figure 1. The test procedure, ( I ), is briefly as follon-s: Four hundred millilit alcohol-acetaldehyde feet1 are passed over 12 ing a period of 8 hours: tlirx t.ffluents are liquefied \I-ith &,I- ice: the uncondensable gas is ver a salinr solution: and the carbon deposition on the tleterminecl at'tc.i, thr en11 of the ruu. The material determined on tliv t)a& of these three values-i.e.j liquid, gas, and cai,lmi. E STAR L1 SH \I E \ 'I- 0 F K E 0CIR ED A CCUR i C I E S
Analyticnl procedurijs :tiid test methods employed in the origin a l development of this ht:itlirne process were made availahlc t o the fell(in-ship by the CIai,l)icl~:ind Carbon Chemicals Coi,poratiiin. .2lthough thwe methods had served for developing the through t h pilot-pl:cnt ~ stage, their adequacy ivas doubtf u l for the nem- projract xvherc I cle could not be utilized to niiriiniize effect of analytic.:il ( " ~ r s . It n-as calculated that their precision 1i:id t o l i r withixi * 1% if yield data were to be sound clnough t o indicate iriilirovctl c.at:ilysts. This + lyOis predieatcd
Figure 2.
Effect of \raterial Losses on Calculatiorls
For ;iccur:tte per-pass and ultimate yield dnta :i minimum of three components had t,o be known n i t h accur:ic>-. The per-pass yield was calculated as fi)lliJ\W: hlol(8 c; I)er-pass yield = -~ mulrs ~~~uf CJ16 for1necl x 200 ___ nioles of ('rHsO€I fed niolrs of ('H.,CFIO fed ~
Tlio u1tini:itc !.ic,ld Molca
c;
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n - : siinilnrly ~
ultimate yirlcl
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c-:ilculntetl:
=
1lli)lesCJf C~EIG f(>rliied X 200 (moles of C2H&11 feed 1 moles of C,H,OH out) . moles of CH$.?HO feed - moles of CHICHO ___ out -~~~ 0.92
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Figure 1. A. B.
Flow Diagram of Laboratory Apparatus
Feed reservoir Pump iit aii:ilyse~~ (:iii:il!-ses of C, fractioii, :icc.t:ilrlc~hydefr:tctioii. ('tliyl :ilcohol fr:ic,tioii for ac~etaldt~hytloarid:or aretal) and 41)ility of t h r total iiltlr.hydc~is thc poorest e. iiivolvr~d l'c~rtiiirnt points considereil cntions had to IFest:il)liahtd: end point an(1 inilic*ator,trmpcwiturr of analysis, con~~entratioiis of hydrosyl: i n i i t i v ~ i ~ t i i ~ o c . h l otinti i ~ i effrrt ~ I ~ ~ ,of other :iltlrhydes ( 6 , ?, !)). :I
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O \ 6H-t LI. REPROUU
