3 C nterpret The Editors... 3EB valuate CS omment
• C h e m i c a l s t r u c t u r e of c o a l i s a r i d d l e t h a t h a s l o n g d e f i e d s o l v i n g . I n the last few years an im pressive array of chemical and physical methods has been applied to the problem, building u p d a t a bit by bit. These pieces have been put together by G. R. Hill and L. B. Lyon of the University of U t a h , to build a model of high-volatile bituminous coals. T h e model features large heterocyclic nuclei mono mers, with alkyl side chains. These are held together by three-dimensional G—C groups, functional oxygen groups, and ether bonds. Sulfur is interchangeable with oxygen in some structures, and m a y be present with oxygen in the linking units. Nitrogen occurs only in the ring structures. P a r a f f i n s a r e m u c h m o r e i m p o r t a n t than previously thought. Surprisingly, they do not postulate a large n u m b e r of isomers—in this model the large condensed nuclei have the same simple aliphatic side chains. T h e y feel that considering the large n u m b e r of theoretically possible isomers has only confused other investigations. Al though coals from different sources may vary, it ap pears that long-chain, simple aliphatic and alicyclic hydrocarbon groups predominate in many high volatile bituminous coals. Multiple polynuclear ring struc tures are apparently absent. Although coals were once thought to be a chicken-wire of 50 to 60 of these ring structures tied together, it now seems that only.five or six combine into each aggregate. This new concept may change the direction of coal utilization.
• W h y n o t α c o a l r e f i n e r y ? Although total hydro génation of coal is certainly uneconomic, techniques developed for the petroleum industry could perhaps be economically applied to improve yield and value of coal liquids. T h e trend in petroleum refining to increased hydrogen processing has resulted in well-developed techniques for hydrocracking, hydrogénation, and cleavage of nonhydrocarbon bonds by hydrotreating. Now, more complete knowledge of chemical structure of coal shows how these processes can upgrade coal. Such a refinery would include these units : • Hydrocatalytic coker—heating with a catalyst such as cobalt-molybdenum under controlled conditions would greatly increase the coal-liquids production, with lower liquid molecular weight. • Coke treater—controlled polymerization, condensation, and calcining reactions would yield metallurgical grade coke. • Hydrogen treater—the hydrogen rich portion of the liquid would undergo a mild secondary treatment, to produce aromatic a n d isoparaffin rich liquids 16 A
INDUSTRIAL AND ENGINEERING CHEMISTRY
new and unusual ideas and challenging developments on the research & technology front
• Hydrocracker—heavier liquids would require hydrocracking to upgrade them • By-product recovery—ammonia and sulfur recovery would improve economics. • Sulfur m a y l o s e its punch a s a c a t a l y s t p o i s o n now that r h e n i u m and its compounds are commercially available. I n several processes, compounds of rhenium have as high activity as nickel and precious metal catalysts but are as resistant to poisoning as cobalt and molybdenum. In specific cases they show unusually high selectivity. Several compounds are effective catalysts, most of t h e m easily prepared by standard methods. Add to this list of advantages
α price roughly half that of precious metals, and it is certain that American industry will soon be come interested. Russian interest in r h e n i u m is already apparent—straight-run naphthas are being reformed with these catalysts in East Germany. Compounds of rhenium should be considered for: • Selective hydrogénation • Selective dehydrochlorination • Oxidation in either liquid or vapor phase • Dehydrogenation, especially of alcohols to aldehydes and ketones, and of cyclohexanes to aromatics • Dehydroisomerization of alkyl cyclopentanes to aromatics • Dehydrocyclization of paraffins to aromatics • Isotope exchange • Are t h e n e w high t e m p e r a t u r e process m e t h o d s using large amounts of electric power entirely impractical? T h e y m a y be used sooner t h a n we think, if present trends continue. T h e cost of electric power has remained relatively stable, but material and labor costs have been increasing rapidly. Economics may soon favor such reactions, if heat-resistant materials of construction are forthcoming. Meanwhile, fundamental high temperature reaction data, especially on free radial mechanisms, must be developed. Such data are almost nonexistant. • The c h e m i c a l e q u i l i b r i u m barrier c a n b e a p p a r e n t l y b r o k e n . I n high temperature gas reactors, quenching a stream containing free radicals can result in product concentrations substantially above equilibrium values. T a k e the production of acetylene from the elements, for example. R. F. Baddour and J. M . Iwasyk of M I T have achieved yields m u c h higher t h a n previously predicted. T o do this, they used temperatures in excess of 2500° C , with rapid quenching of the product gases. A high intensity arc reactor was necessary—plasma jets and induction-heated reactors failed to give the desired
reaction conditions. This reactor uses a consumable anode—above a critical current density the anode va porizes rapidly. Anode vapor streaming from the sur face at high velocity gives a flame extending several inches from the anode. Further superheating of the anode vapor would provide even higher temperatures— perhaps as high as 10,000° C.
Formidable problems remain to be solved, especially in materials of construction and in the quenching method. Quenching must be rapid, and is wasteful of high temperature heat. But the technique is applica ble to many reactions, especially where a solid which is difficult to vaporize reacts with a gas. {For more long range trends turn to page 79 A)
on technical trends in this issue of
I/EC
/
is Upjohn's countercurrent crystallization process. This method doubles the yield of stigmasterol and reduces the cost of making progesterone, a very useful intermediate in a variety of steroid agents. For a complete picture of how countercurrent crystallization is used to make steroids, including thoroughly descriptive material balance charts, turn to page 949.
^ Cyanogen, a highly reactive chemical intermediate, is used mostly in the preparation of insecticides. But because of its reactivity, it is being investigated as a possible starting material in the preparation of metallic cyanides. Purity and volume of recoverable material have been the chief drawbacks to widespread use. Now there is a c o n t i n u o u s , c a t a l y t i c , v a p o r - p h a s e process on the boards that gives greater yield and higher purity product than can currently be obtained. Commercialization of this technique cotild open the door to widespread use of cyanogen as a starting mate rial (page 985).
• Need for increased and improved automatic control systems of distillation columns is becoming more im portant. Demand for higher purity products, emphasis on economic optimization of new plant designs, and operation forces this need. On page 963 you will find an analysis of h o w a u t o m a t i c controls r e g u l a t e column h e a t input as a means for controlling a distillation column. This discussion represents some of the latest thinking in using this type of control on distillation columns.
t» There has been a great surge in the construction of naphthalene processing units. Target for the product is, of course, phthalic anhydride and the huge and still growing plastics market. The better the naphthalene, the better the phthalic anhydride, the better the plastic material. How o n e c o m p a n y purifies n a p h t h a l e n e is the story beginning on page 993. Since the material is from coal, this technique could give a great boost to naphthalene from coal in particular and coal chemicals in general.
• Control of continuous solids feed is a major headache in many processes today. Not that some of the systems are not functioning well but from the standpoint that they could function better. Result is that you get a
^ Interest in rare gases has been increasing at a rapid rate, due in part to the fact that fission products are made up of gaseous materials. And rare gases are ex cellent tracer materials. Yet many of the useful and unique properties of rare gas nuclides have not been exploited, mostly because they are gases under normal conditions. When they are made with clathrates, in clusion type compounds that prevent their escape, the r a n g e of u s e f u l n e s s of t h e rare g a s e s can b e e x t e n d e d . You will find much food for thought in the article beginning on page 1007.
• Steroids rank second in dollar volume among ethical pharmaceuticals. Biggest share of the steroid market is taken up by cortisone. But other steroidal compounds are likely to show up equally well in the future. K e y f Ο
newer and better anti-inflammatory
agents
more uniform reaction, fewer process swings, and more uniform products. On page 970 you will find some suggestions on solving the problem of delivering solids from a common feed source con tinuously and uniformly to a series of parallel beds. As an example, there is an empirical design equation for moving ground oil shale to several points. • How to make the most money possible is the prime concern of every chemical producer. When he must do it in existing equipment he often turns to long and tedious mathematical equations to optimize his process. On page 979 you will find α s i m u l a t i o n p r o g r a m discussed which reflects the effect of uncontrollable variables in o p t i m i z i n g conditions in a contact sul furic acid plant. Our authors have constructed a mathe matical model of the plant in the form of a computer program which can actually be "run". The approach described here may help you optimize your process.
^ Don't miss this month's Annual R e v i e w s . There have been many significant advances in H a l o g e n a t i o n you will not want to miss. And the reported finding under Combustion fits well with the trends and developments in H e a t Transfer (page 1015). ^ Want to find a particular subject? Author? Or trend?. Then turn to our Annual Subject a n d A u thor I n d e x e s . Here you will find a rundown on all that I / E C has published in the past year. And be sure to keep this index for your future reference (page 1033). V O L . 53, NO. 12
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DECEMBER 1961
17 A
