Hydrogenation is key part of coal liquefaction process Recycle gas
Hydrogen
Hot separator
Fixed-bed unit
Intermediate Fixed-bed separator unit
Cold separator
in KM V7 Vacuum flash
Refined syncrude
Catalyst • Coal*
removed. Elimination of the purge water requirement means there is less wastewater to treat. IGOR has been scaled up to a large semiworks plant at Bottrop. In the scaleup, it was determined that the slurry preheater is no longer needed because the slurry preparation can be accomplished by heat exchange with the products. Test periods of up to 330 days have been achieved with no signs of catalyst deactivation. The only problem anticipated now is the possibility of feed coals with unusually high oxygen contents, which might provide more carbon oxides than can be conveniently handled. Joseph Haggin
Recycle oil Residuum (to gasification)
The processes are largely modifications of conventional high-pressure hydrogenation processes. They all share a number of common features—for example, method of slurry preparation, solvent recycle, indirect preheating, and asphaltenes and solids separation. Unfortunately, they all also share the common problem of producing oils with unacceptably high nitrogen and oxygen contents. Before the products can be sold, they must be further refined at considerable cost. Because hydrogenation is also the process by which polynuclear aromatics, aromatic nitrogen bases, and phenols are removed from raw synthetic crude oils the same problem is encountered. Development of a new scheme for hydrogenation is one way to address the need for further refinement. However, Strobel and his associates claim to have found a better way. Integrating the hydrogenation with existing processing, he says, offers a preferable alternative. Strobel's reference method is his company's DT-process, which, like other methods, produces products that require further refining because of high levels of nitrogen, oxygen, and fused-ring aromatics. All must be reduced. Because of the essentially cyclic nature of the coal-derived oils, rather severe hydrofining conditions are required. In the DMT alternative, hydrofining and saturation stages are integrated into the steps at the refining
plant rather than being done separately in another plant. The integration is achieved by inserting fixed-bed hydrogenation reactors downstream from the intermediate separator to hydrotreat product oils before they are condensed. This saves energy by utilizing the high pressure, hydrogen-rich gas, and heat from the separator. Further integration is accomplished by arranging the fixed-bed reactors to hydrotreat both net product and recycle oil for slurry preparation. The heavy distillate fraction is injected into the system before it reaches the reactor. The final version of the process now includes two smaller reactors, one for the product oils and one for recycle. This process variation has been named IGOR for integrated gross oil refining. Because of IGOR, any potential for product toxicity has been removed. Coal conversion temperatures in IGOR are somewhat lower than in the parent DT-process. This results in reduced gas production and a lower hydrogen demand. However, extra hydrogen is consumed in methanation of carbon oxides, which inevitably occurs on the very active catalysts. Fortunately the methanation is minimal. Elimination of the carbon oxides has an overall advantage, however. Since there are no carbon oxides to purge from the products, there is no requirement for water injection as is the case with most liquefaction processes. At the same time, phenols are completely
Groups of molecules behave uniquely
Groups of molecules act differently from single molecules. In some cases, there is a spontaneous assembly of molecules for purposes that cannot be accomplished by single atoms or molecules. This phenomenon has led to development of chemical systems that can, for example, deliver drugs to cancer cells or destroy chemical warfare agents. According to Frederic M. Menger, a professor of chemistry at Emory University and a principal investigator of the phenomenon of chemical collectivism, the key to this type of chemistry is an organized assembly of molecules he calls the molecular system. One example of such a system, an unusually complex one, he told the Division of Colloid & Surface Chemistry, is the living cell. Simpler examples are micelles, vesicles, films, and emulsions. Menger's research group has assembled several systems to demonstrate the potential of thinking "collectively" about chemistry. One possibility involves a cancer cell moving through the blood stream exuding a particular enzyme. The cell collides with a shell carrying an anticancer drug. The shell breaks open as it interacts with the enzyme and releases the drug precisely APRIL 20,1992 C&EN 25
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where it is needed—at the cancer cell. It is the molecular-system shell that provides the selectivity. Normal cells that exude smaller amounts of the en zyme should leave the drug-shell sys tem untouched. The particular system developed by Menger's group consists of about 5000 molecules. Such an enzyme-sensitive system is now working in a test tube. When acetylcholinesterase, an enzyme produced by some cancers of nerve tis sue, is added, the molecular container breaks open and releases its contents. Another system under investigation is intended to destroy mustard gas, a chemical warfare agent that damages eyes, skin, and lungs and is often fatal. Because this poisonous gas will proba bly remain in production somewhere regardless of chemical weapons trea ties, Menger says, the next best thing to banning production might be a method to combat its effects. Menger's group is working on a sys tem that will do just that. It is a microemulsion of oil, water, surfactant, and alcohol. The emulsion looks like clear water. But when an oxidizing agent, such as household bleach, is added to the microemulsion, the system will dissolve mustard gas and oxidize it to a harmless product in 15 seconds or less. Menger has previously reported on several examples of micellar catalysts that neutralize phosphate esters, specif ically such nerve agents as soman, also known as GD. One of the catalysts used in the hydrolysis of the phosphate ester caused the reaction to proceed 1800 times faster than that of the uncatalyzed system. However, this rate is still much too slow. It would be desir able to increase the rate of hydrolysis by at least 105. To this end, Menger's group devel oped another catalyst that utilizes cop per-coated micelles. This system accel erated the rate of hydrolysis by 106 and reduced the half-life of the nerve agent from 60 hours to 50 seconds. The implications of this study of ca talysis may have great impact in more robust systems of interest in industry. The reaction rates of several examples under study by Menger are extremely high. Such systems might be superior to most industrial catalysts, if they could be made to survive in the indus trial environment. Joseph Haggin
