Catalysis Gains Widening Role In Environmental Protection - C&EN

Sponsored by the Catalysis Society, it brought together a sizable delegation of chemists from the Boreskov Institute of Catalysis in Novosibirsk and f...
1 downloads 0 Views 2MB Size
Download PDF
SCIENCE/TECHNOLOGY

Catalysis Gains Widening Role In Environmental Protection etal reasons. Both Zamaraev and Bell emphasized the virtues of collaborative research and more frequent contacts in the future. As in the U.S., environmental catalysis in Russia involves much more than cleaning up sulfur and nitrogen oxides and controlling vehicle emissions. In a plenary address, Zamaraev outlined an array of theoretical and applied projects currently under way in Russia, many, if not most, at the Boreskov institute. For example, Russian basic research in catalysis ranges from investigations into the detailed structure of vanadium catalysts for the control of sulfur dioxide emissions to the design of composite semiconductor catalysts, including one with a heterojunction. A growing area of catalytic research, Zamaraev says, is biomimetic catalysis— the attempt to simulate the catalytic ac-

tion of natural organisms. Russian researchers are investigating the immobilization of organisms on inorganic supports such as silica and carbon. In this work, micelles or vesicles, about 300 A in diameter, are the vehicles for the catalysts. Some are being considered for oxidative coupling of methane to methanol and to C3 and C4 hydrocarbons. A key problem is enhancing the micellular membrane's Joseph Haggin, C&EN Chicago ability to conduct oxygen. A s a discipline, catalysis is an eclectic Two unusual areas being probed by / % one. That characteristic is particuRussian researchers, according to ZamaJ L J L l a r l y apparent when the field raev, are heterogeneous catalysis in the under consideration is the environment. troposphere and redox catalysis in natuSuch was the case last month in Wilral water. Tropospheric dust from Earth mington, Del., at the U.S.-Russia Workcontains solid aerosols with such semishop on Environmental Catalysis. Sponconductors as titanium dioxide, zinc oxsored by the Catalysis Society, it brought ide, and iron oxides. These agents are together a sizable delegation of chemists present in high enough concentrations to from the Boreskov Institute of Catalysis promote photocatalytic processes under in Novosibirsk and from elsewhere in the action of visible light. And some of Russia to meet with U.S. counterthe particles are coated with water, parts from academia and industry. § which provides a medium for chem£ istry. Furthermore, Zamaraev says, Xhe role of catalysis in environ| "the chemistry we see in the region mental improvement is crucial. Cat^ closer to Earth is no less important alytic approaches infuse both basic than the chemistry in the upper layresearch and applied research, as ers of the atmosphere/' chemists and engineers seek to better understand the mechanisms opIn natural waters, Zamaraev says, erating in the environment itself, if s known that Fe(II) species can r e probe the application of catalytic act with oxygen and any organic techniques to cleaning up a wide present. This, he says, suggests variety of existing problems, and apmeans for promoting natural cleanply catalysis in the design of benign ing processes for groundwater. processes that will eliminate or miniRussian applied research in catalmize pollution in the first place. ysis, according to Zamaraev, is dis"Finding a theme for the worktributed among numerous projects, shop was not difficult because there such as producing ozone-friendly is no more important or noticed ischlorofluorocarbon (CFC) replacesue these days than protecting the ments for refrigerants and blowing environment," said Alexis T. Bell, a agents. Russian researchers are also professor of chemical engineering at active in developing catalytic comthe University of California, Berkebustion processes that emit no nitroley, and chairman of the workshop. gen oxides, in devising efficient fuel cells for producing power, and in Kirill I. Zamaraev, director of the designing chemical processes to Boreskov institute and head of the combine endo- and exothermic steps Russian delegation, added that it to minimize energy requirements. A was of critical importance that catamajor interest in the Boreskov instilytic chemists develop stronger relations, for professional and for soci- Bell, Zamaraev, Manzer (from left); catalysis crucialtute, Zamaraev adds, is the elabora-

• Workshop spotlights new catalytic approaches that together provide multifaceted attack on environmental problems

22

FEBRUARY 14,1994 C&EN

tion of unsteady-state processing as a means to increase catalytic selectivity and Dehalogenation approach links bacteria, membrane minimize energy consumption. Cytoplasm Membrane Periplasm A U.S. view at the workshop came (sulfate-reducing bacteria) (with immobilized enzymes) from Leo E. Manzer, manager of the corLow molecular weight porate catalysis center at DuPont. IndusR-CI cytochromic enzyme CH 3 COC0 2 try, he said in a plenary address, faces two major challenges: cleaning up the efHematin fects of past manufacturing problems and minimizing the waste from current processing. "In the future, we will have CH 3 C0 2 to develop zero-waste processes, minimize the use and transportation of hazHR + C r ardous materials, and develop inherently safer products. We also have to satisfy Flavin-enzyme Fast Hydrogenase catalyst H+ H2 the stockholders/' Chlorinated hydrocarbons present Anaerobic fermentation one cleanup problem. A promising technique, Manzer says, is biocatalytic remediation, which couples naturally occur- tion purification is necessary. The com- ics. Manzer says the effort will require ring biological processes with catalytic pany can simply load tankers from the greater global cooperation, and he beenhancement. Cellular redox coupled to process output and ship directly. lieves that greater networking among extracellular catalysis, which provides a Elimination of CFCs, which have been various professional communities will biological source of electrons for the ca- implicated in atmospheric ozone deple- be needed. talysis, is one example. tion, was mandated by the Montreal ProAnother example of new high-yield, Reductive dehalogenation combining tocol on Substances That Deplete the low-waste process technology cited by membrane catalysis and sulfate-reduc- Ozone Layer and the Environmental Pro- Manzer is the manufacture of nylon 66, in ing bacteria might also be used. In this tection Agency. The replacements were which adipic acid and hexamethylenediinstance, the cytoplasm functions as an developed by researchers after they had amine react to produce the nylon. Current electron-transfer shuttle agent to the waded through a lot of complex chemis- annual global capacity for nylon 66—used surface of the membrane. At the sur- try and had devised some new catalysts. as an engineering resin and as a polymer face, several detoxification possibilities DuPont considers hydrofluorocarbon- for textile fibers—is about 5 billion lb, and would exist, including anaerobic fer- 134a (CH2FCF3) the refrigerant of the fu- one of the environmental difficulties lies mentation. Dechlorination of carbon tet- ture, Manzer says, and most new autos in the production of adipic acid. rachloride by proteins might be one ap- are already using it in their air conditionThe classic reaction of cyclohexane with plication of the technique. Another ers. The development effort required two oxygen to form cyclohexanone and cyclomighf be the dehalogenation of lindane, years from the first experiment in the lab- hexanol with further reaction to adipic an insecticide whose principal ingredi- oratory to the operation of the first plant. acid also forms undesirable dibasic acids. ent is hexachlorocyclohexane. The deha- In fact, six plants are now ready to operate These constitute pollutants if dumped in logenation would be carried out by por- but, Manzer notes, the public seems the environment. They can also be conphyrins, with the most active being Co- loathe to use the products—a rather iron- verted catalytically to adipic, glutaric, and protoporphyrin, which could convert ic situation, he says, considering the clam- succinic acids, which can be reacted with 130 nanomoles of lindane per minute or to find alternatives for CFCs. The total methanol to form the corresponding esper mg of the porphyrin. For all the cas- CFC phaseout is about two years away, ters. The dibasic esters can be employed es, DuPont anticipates commercial sys- although under the international treaty in several markets such as coatings, soltems for such reductive dehalogenations developing countries are allowed to con- vent replacement, paint stripping, and in the future. tinue making CFCs for 10 years beyond cleaning agents. In particular, they might replace toxic methylene dichloride. A Manzer cites DuPont's process for that deadline. producing a CFC replacement as an exSince the HCFCs were developed by high-purity glutaric acid, for which a ample of an environmentally safer prod- the judicious use of catalysis, Manzer market exists, could be made by hydrouct. The product, hydrochlorofluorocar- used them as an example of what he sees lyzing the appropriate dibasic ester. bon-141b (HCFC-141b, CH3CC12B, is as "tremendous opportunities emerging Under extreme conditions, any chemimade according to the reaction: for catalysis and new kinds of process re- cal might be hazardous. However, some search based on catalysis/7 Environmental materials are always so. An unfortunate CH2=CC12 + HF-^ catalysis is inherently multidisciplinary, example is methyl isocyanate. This was CH3CC12F + CH3CC1F2 + CH3CF3 he points out, and it extends beyond the the chemical released in the Bhopal, InThe reaction is run in two stages, the traditional boundaries of chemistry and dia, disaster 10 years ago. The classical first between 25 and 150 °C at 0 to 160 chemical engineering. With the drive to synthesis, originally developed at Union psig and the second between 5 and proceed toward zero waste and zero Carbide, is: 75 °C at 0 to 80 psig. The yield is 99.5% emission of pollutants, the environment CH3NH2 + 2COCl2 -> CH3NCO + 2HC1 HCFC-141b. Manzer says the nice thing may be a first consideration, but equally about this process is that no postreac- important are industrial process economThis synthesis requires the storage

i

FEBRUARY 14, 1994 C&EN

23

SCIENCE/TECHNOLOGY and transport of large quantities of the hazardous material. Manzer cites an improved process, developed by DuPont in 1985, based on the reactions: CH3NH2 + CO -> CH3NHCOH -> CH3NCO + H2O with the final reaction being catalytic. The virtue of this process, says Manzer, is that there is a very low inventory at any time—specifically, less than 1 kg residing in the process. Manzer notes further that this process illustrates the industry's trend toward producing hazardous materials at the point of consumption, on demand. Hydrogen cyanide, from which methyl isocyanate is made, is also a largevolume hazardous material. Within DuPont alone, the annual demand for the chemical is about 500 million lb per year, most of which is used in making adiponitrile. External sales add up to about 1 million lb per year. It is usually shipped in gas cylinders and that could mean up to 4,000 cylinders being shipped per year, which DuPont considers a bad risk. If the economics were favorable, it would be desirable to have a small skidmounted plant for on-site production of hydrogen cyanide to eliminate the shipping hazards. Obviously, the environment would also benefit. The two major competing processes for hydrogen cyanide are the Degussa and the Andrussow processes. DuPont has been attracted to the Degussa process, says Manzer, because of the high yields. However, it also requires a large financial investment. Therefore, DuPont is developing its own process, which directly and cata-

lytically converts methane to hydrogen cyanide as in the Degussa process: CH4 + NH 3 -> HCN + 3H2 The catalysts used include platinum, rhodium, and palladium on alumina. The reaction proceeds at 1,200 °C. Advantages of this new approach include quick startup and shutdown, which are realized by using microwave heating for the catalysts. On-site production and consumption reduce the chance of accidental exposure. Yield is high (957c), and there are virtually no waste streams. The process requires no ammonia scrubbing, the ammonia being removed by adsorption. The microwave reactor is still being evaluated. It is very expensive and hence might offset some of the otherwise inherent economy of the system. However, the idea does illustrate the trend toward intrinsically safer chemical processing.

Pollution control Other speakers at the workshop elaborated on and added examples to the areas of environmental catalysis outlined by Zamaraev and Manzer. Both Russian and U.S. researchers are working on projects related to pollution mechanisms and pollutants in the environment as well as new process technology. For example, an area of growing interest concerning environmental mechanisms is photocatalysis. At the Boreskov institute, Valentin N. Parmon is investigating the heterogeneous catalytic processes that can occur in the atmosphere near Earth's surface on dust particles under the action of near-ultraviolet, visible, and even near-infrared solar light. Indications are that, though usually neglected, these reactions are as important as the better known photochemical reactions pro-

Catalytic hydrochlorofluorocarbon process has high yield CH2=CCI2+HF

•

1,1-Dichloroethene

1,1-DJchloroethene + HF

OHsOC«#

HCFC-14tfc

H

Stage 1

25-150 °C 0-160 psig >92% conversion

24

FEBRUARY 14,1994 C&EN

+ CH3CCIF2

+ CH3CF3

HCFC-142b

Stage 2 5-75 °C 0-80 psig Liquid phase

HCFC-143a

•I

L

HCFC-141& jJCTI -oo oo- i =tod 99.5% CH3CCI2F 0.5% CH3CCIF2 500 ppm CH2CCI2

ceeding in the upper atmosphere under the influence of UV light. Hie greatest effects come from oxides of iron, titanium, and zinc, which are present in natural aerosols. Even though quantum yields of the photocatalytic processes in the actual atmosphere may be lower than those studied artificially, they most likely have considerable influence on atmospheric pollutants. However, research is needed to prove or disprove the estimates. In a related investigation, Evgenii N. Savinov of the Boreskov institute is trying to show that processes involving dispersed semiconductor catalysts and admixtures of hydrogen peroxide or ozone may be the most adaptive systems in deep oxidation of all types of organic compounds in natural waters. This, however, is highly speculative at present. Aleksandr Ya. Rozovskii of the A. V. Topchiev Institute of Petrochemical Synthesis in Moscow is concerned with limiting carbon dioxide released to the atmosphere. Processing C0 2 requires reducing agents and energy. Hydrogen would be the ideal reducing agent, and one concept touched on by Rozovskii would involve the reaction of C0 2 and hydrogen to form methanol and other products that could then be converted to petrochemicals and fuels. Rozovskii is concerned with FischerTropsch chemistry and the synthesis of carbohydrates by catalysis and irradiation as alternate pathways. At the workshop, he reported on new results of work carried out in cooperation with Valerii V. Lunin of Moscow State University. They have been studying new intermetallic compounds with a high activity in CO/C0 2 hydrogenation. One of the catalysts is a zirconium-copper hydride composite, which exhibits some new solvent effects. Results were also reported for two iron-based catalysts for Fischer-Tropsch chemistry. The first, also designed by Lunin, has a high space-time yield, greater than 0.5 metric ton of C2 hydrocarbons and alcohols per cubic meter of catalyst per hour. This value is five times faster than the yields with conventional catalysts. Still another Fischer-Tropsch catalyst being studied is unusual because of a product distribution having a maximum corresponding to C10 to C12 hydrocarbons, rather than the more usual C6 to C10 range. Oleg V. Krylov of the Institute of Chemical Physics in Moscow has been interested in the catalytic reaction of

Catalytic conversion of dibasic acids can avert adipic acid process pollution O

OH *

+

H0 2 C-(CH 2 ) 4 -C0 2 H

Direct sales

, Catalyst

DBE-2 CH3OH

Dibasic acids

Dibasic esters I

Fractionate

Catalyst

MNtt I1BMI

Purify DAGS (distilled adipic, glutaric, succinic acids)

Hydrolyze A

Glutaric acid (high grade)i

methane and carbon dioxide. To date, he says, only one catalytic reaction of this type has been studied in detail—that yielding synthesis gas (mixtures of CO and H2). Catalyst deactivation in this reaction has been a major problem. Krylov's group has developed what is, in effect, a family of catalysts for the oxidative reaction of C0 2 . This work includes studies of the oxidation of C0 2 with hydrocarbons and alcohols on the transition-metal oxides. Catalysts based on MnO were the most active and selective and did not coke. Over MnO/Si0 2 catalysts, methane and C0 2 produce syngas. Hydrocarbons in the C2 to C7 range are converted to olefins and syngas on K-Cr-Mn/Al203 catalysts. The interaction of C0 2 with isobutane yields an equimolar mixture of isobutylene, carbon monoxide, and hydrogen. The isobutylene can be further processed to methyl ferf-butyl ether. Finally, the reduction of C0 2 with ethylene gives butadiene, and with methanol gives formaldehyde. Nitrous oxide is of concern to the Boreskov institute's Genadii I. Panov, who has been considering it as a possible oxidant in inorganic synthesis. N 2 0 is a problem with respect to the greenhouse effect and the ozone layer. Hence, because a number of chemical processes produce N 2 0, it would be beneficial to use it for something. Panov suggests using N 2 0 in the hydroxylation of aromatics over iron-containing ZSM-5 zeolites. The simplest reaction is direct oxidation of benzene to phenol with nearly 100% selectivity:

Limiting concentrations of nitrogen oxides in the atmosphere is also a matter of considerable concern in the U.S. Reviewing the problem for the workshop, W. Keith Hall, a chemistry professor at the University of Pittsburgh, noted that a major problem with exhaust gasses from combustion processes is the presence of up to 10% by volume of

water and residual amounts of oxygen. An interesting possibility for curbing nitrogen oxides emissions, he says, is catalysis by ZSM-5 containing metal cations. For fixed sources of emissions, reduction of the nitrogen oxides using methane over Co-ZSM-5 looks promising, and other possibilities are looming ahead for diesel engines, fixed or mobile.

Hoechst offers out of R+D:

1,3-Difluorobenzene now available in lab quantities in pilot plant quantities

another example of Hoechst High Chem

Hoechst Ceianese Corp. Fine Chemicals Division P.O. Box 1026 Charlotte, NC 28 201-1026 USA Fax 704-559-6153 Tet 800-242-6222 Hoechst AG Marketing Feinchemikalien D-65926 Frankfurt am Main Germany Fax: (69)31 2021/31 66 77

C6H6 + N 2 0 -> QH5OH + N 2 Panov suggests this as an alternate route to the current cumene process, which requires three stages to complete.

Hoechst Ceianese Hoechst

E

CIRCLE 3 ON READER SERVICE CARD

FEBRUARY 14, 1994 C&EN

25

SCIENCE/TECHNOLOGY However, catalyst poisoning and hence maintenance of the catalyst's integrity under real-world conditions is a major problem in each case. John N. Armor, head of catalysis and adsorbents research at Air Products & Chemicals, reported on a new family of metal-loaded zeolites that have high activity and selectivity for the decomposition of N 2 0 into nitrogen and oxygen. The most active catalysts are copper- and cobalt-exchanged ZSM-5, mordenite, zeolite beta, ZSM-11, and ferrierite. These catalysts readily destroy N 2 0 at low and high concentrations in the presence of 2% water vapor. They also possess remarkable stability and prolonged activity over a broad temperature range. At Brigham Young University, Provo, Utah, professor of chemical engineering Calvin H. Bartholomew is investigating the use of Cu-exchanged X- and Y-faujasites, mordenite, and ZSM-5 zeolites with propane as the reductant to deal with nitrogen oxides. The best conversions were obtained with Cu-ZSM-5, and the data indicate that this catalyst has commercial

potential for applications where it is not desirable to reduce all the constituents of a gas, what is termed selective catalytic reduction (SCR). Also at Brigham Young, chemical engineering professor William C. Hecker has been investigating the effects of adding cerium and molybdenum to supported rhodium catalysts for auto converters. The most active catalyst was 1% Rh/4% Mo on a silica support prepared by impregnation and calcination. There was no transient decay, and the turnover rates were twice that for 1% Rh on a silica support. Indications are that nitric oxide dissociation is the rate-determining step in the reaction. The mechanism of nitric oxide decomposition has always been assumed to be a redox process involving Cu2+ and Cu+ cations. UC Berkeley's Bell has data suggesting that the Cu ions in air-exposed Cu-ZSM-5 undergo autoreduction by a free-radical mechanism on heating. The Cu+ ions thus formed are oxidized by water or mixtures of hydrogen and oxygen but not simply by oxygen, even at 500 °C.

COUNT THEWVYS

Do you know how many ways there are to fulfill your giving wishes—and at savings that may surprise you? As you make plans that will influence your tax picture next April 15, request a copy of our helpful booklet, "Your Guide to Effective Giving in 1994." American Chemical Society Development Office 1155 16th Street, NW Washington, DC 20036 Q Please send me a free copy of "Your Guide to Effective Giving in 1994." Name Address City State

26

FEBRUARY 14,1994 C&EN

Zip

Adsorption of nitric oxide on the CuZSM-5 yields numerous species including mono- and dinitrosyls, nitrato, nitrito, and nitroso groups. At nitric oxide decomposition temperatures, only the latter three species are observed. These results indicate that nitric oxide decomposition may occur via bimolecular processes involving reactions in adsorbed and gas phases. Further insights into the mechanism of SCR were described by Umit Ozkan, associate professor of chemical engineering, Ohio State University, Columbus. She has been investigating SCR of nitric oxide using ammonia at high temperatures. Most of the results were obtained from isotopic tracer studies labeling either nitrogen or oxygen or both. The tracer studies reinforce evidence that vanadia catalysts exhibit structural specificity. There was no observed scrambling of the oxygen atoms between the gaseous phase and the vanadia lattice, although oxygen did interact strongly with the catalyst surface through a four-atom complex. Another approach to nitrogen oxides reduction is being investigated by John Stencel of the Center for Energy Research at the University of Kentucky, Lexington. He is interested in the application of activated carbons with high-surface areas made from natural substances, such as coal or wood. At temperatures between 100 and 300 °C, he finds both surface oxides and gaseous oxygen are required for high activity without the carbon being consumed. Activated carbon can also be used for selective adsorption of nitric oxide from flue gas streams also containing carbon dioxide, water, nitrogen, and oxygen. The presence of oxygen, however, is crucial for this to occur. At the Boreskov institute, Vladislav A. Sadykov has studied reduction of nitric oxide using hydrocarbons on three types of catalysts: modified ZrO systems, cation-exchanged ZSM-5 zeolites, and complex oxide systems using T-alumina. They all display high activity in the temperature range of 450 to 650 °C and in oxygen concentrations of up to 10%. They are not sensitive to poisoning, and in mixtures containing up to 6% water and up to 500-ppm sulfur dioxide, the maximum conversion can be as high as 80% at space velocities of 10,000 h -t . The mechanisms of the reactions are still unknown, but it appears that activation of the hydrocarbons on these active centers via the generation of radicals does occur. Also, R—NOx(NCO) species form by interaction of the radicals with nitrate-

Process for on-site production of HCN HCN, N2, NH3, CH4, H 2

Catalyst (Pt/Al203, 1,200 °C)

NH. + CH4

• . . offers advantages, some from microwave heating • Quick startup and shutdown (rapid heating) • On-site production and consumption • Reduced potential for exposure • High yield (more than 95%) • Essentially no waste streams

nitrite complexes, followed by decomposition of these species under the action of nitrogen oxides and oxygen. The Boreskov institute is currently considering the manufacture of these catalysts.

New technologies In the U.S., an environmental problem of great concern has been waste plastics, and technology for their conversion to useful products would thus have widespread appeal. Such a process is the goal of C. Andrew Jones, research chemist at Arco Chemical, Newtown Square, Pa. Jones has been developing a method to catalytically crack mixed, composite plastic waste to basic chemicals, demonstrate the process in a fluid bed, and deduce the operating characteristics of a solid-acid catalyst such as HZSM-5. More specifically, he has been developing a robust catalyst that tolerates steam and feedstocks that may contain chlorine and other possible catalyst poisons. About 807c of municipal waste in the U.S. consists of polyethylene, polypropylene, polystyrene, and polyethylene terephthalate. All of these can be recycled in the process under development at Arco. A conceptual process has been devised by Arco in which wastes are collected from an area within a 50-mile radius of the processing plant. The collectible

amount is considered to be about 307 of the waste plastic from a population of about 10 million people. Products containing about 407 benzene/toluene/xylene and higher materials from the processing would be suitable for making gasoline as well as considerable amounts of low molecular weight hydrocarbons. Economic analyses indicated that if an operating plant could process a billion pounds of recycled plastic per year, the cost of producing the gasoline would be about 57 cents per gal, making it an interesting proposition. The biggest problem is collecting that much plastic. At present, the collection and transport infrastructure to do this is not in place. However, the technology seems to be available if and when collection becomes reliable. New ways to deal with oil or chemical slicks on water is another area of concern. John G. Ekerdt, a chemical engineering professor at the University of Texas, Austin, is looking at the oxidation of organics on water, as would be encountered in oil slicks on the sea or organics generated by bacterial action in

holding ponds. More specifically, he is investigating the oxidation of 3-octanol, octane, and crude oil over nanocrystalline titanium dioxide films bound to buoyant, hollow, 80- to 150-um diameter glass microbubbles. The catalyst is overcoated with alkyl-terminated open silicate networks to make it float at the airhydrocarbon interface rather than at the water-hydrocarbon interface. In a typical experiment, the catalysts readily strip organic films from water and then catalytically oxidize the sorbed organics. Ekerdt was surprised that the dominant oxidation products were carbon dioxide and water, even in the early stages of the reaction when the organic concentration exceeded the dissolved oxygen concentration. Ekerdt proposes that the oxidation is initiated by a photoelectrochemical reaction and is propagated by a sequence of known, combustionlike, radical-propagated reactions. In holes photogenerated in the Ti0 2 particles, adsorbed water is oxidized to OH - radicals and protons while the electrons reduce O^ to adsorbed

It's who you know in industrial gases. Argon Helium Hydrogen

%np

/ IN*'

Njtrogen

h *NIT CCA /^ ^

^#I7 **

PRfiff»')

Oxygen ' Rare gases Semiconductor gases §

From pipelines, transport trailers, tank cars, cylinders, on-site cryogenic and non-cryogenic systems. Call 1-800-PRAXAIR, or write to 39 Old Ridgebury Road, K2-466, Danbury, CT 06810-5113.

PRAXAIR is the producer of LINDE® gases.

PRAXAIR CIRCLE 5 ON READER SERVICE CARD

FEBRUARY 14, 1994 C&EN

27

PRODUCT PROSPECTUS Wf

PEGs

SCIENCE/TECHNOLOGY

and PEG Derivatives for Pharmaceutical and Biotechnical Applications PEG-phospholipid

OTHER GLYCOLS COULD STUNT YOUR GROWTH

PEG-0-CH2CH2—C-O-N

•tresylate •aerylate •aldehyde •succinimidyl succinate •hydroxyl acid •hydroxyl amine •thiol •amine

MPDiol® is a fast-reacting, liquid diol with unique properties for traditional Neopentyl Glycol, 1,3 BG, 1,6 Hexanediol and Trimethyl Pentanediol applications. ARCO Chemical MPDiol for the manufacture of ... • • • • •

PERSONAL CARE POWDER COATINGS HIGH SOLIDS COATINGS URETHANES ADHESIVES

MPDiol

2-Methyl-1,3-Propanediol 1-800-ARCOTEC (U.S. Only) 610-359-2000

ARCO Chemical 3801 West Chester Pike, Newtown Square, PA 19073

ALSO AVAILABLE: PEG and M-PEG from NOF, Japan PEG (1500-20,000 MW) M-PEG (up to 25,000 MW) Call for full product listing

Shearwater Polymers, Inc. ^ ^ ( 8 0 0 ) 457-1806 ^ ^ (205) 533-4805 (fax) J r

2130 Memorial Pkwy Huntsville, AL 35801 CIRCLE 6 ON READER SERVICE CARD

3IRCLE 1 ON READER SERVICE CARD

SEPARATION AND ENRICHMENT OF STABLE ISOTOPES Isotec offers fcy£B& of the c ls

i ^ nm« •JikW^ '

ar est

' 9

I ^ ^ J H "^lelections of PWitiB™ , stable isotopes I V l l and labelled • jW compounds. • Ajpfoo Acids & Derivatives • Carbohydrates • Intermediates • Agricultural Compounds • Custom Synthesis Quality Products • Excellent Service Competitive Prices

V f.iï 4-4

ESIUM

L «

s

To meet your chemistry needs.

ι

CIRCLE 4 ON READER SERVICE CARD

I

Call us for purity, pricing and delivery information. Cesium Acetate • Cesium Bromide Cesium Carbonate • Cesium Chloride Cesium Cbromate • Cesium Fluoride Cesium Formate • Cesium Hydroxide Cesium Iodide • Cesium Metal Cesium Nitrate • Cesium Oxide Cesium Perchlorate • Cesium Sulfate Other compounds available upon request. Also producers of Rubidium, Germanium and Tellurium products. Manufactured in Revere, Pennsylvania by:

WW*Ê.

3858 Benner Road, Miamisburg, OH 45342 (513)859-1808(800)448-9760 Telex: 288278 FAX: (513) 859-4878

W

(800)445-8521 (610)847-8407 Beaver Run Road Revere, PA 18953

. )^T Performance

p

Materials RVICE CARP

I1

02~. The site for this activity has not been determined. In the realm of new chemical processes, Valerie K. Duplyakin of the Boreskov institute is developing a combined process for desulfurization and dearomatization of crude oil fractions. The same Ni-W/Al 2 0 3 catalyst both hydrogenates aromatics and helps hydrolyze hetero compounds such as organic-sulfur materials. By using unsteady-state processing, Duplyakin claims that the process is energy efficient and the hydrogenation yield is from 60 to 70% of the theoretical yields at pressures of less than 50 atm. The catalyst is a mixture of dispersed halide salts on a metal support. These are good alkylation catalysts and isomerization catalysts and are useful in phenol alkylation with chloroparaffins. Also at the Boreskov institute, Oleg M. Hinich has been looking into membrane catalysis in connection with the oxidative coupling of methane. The original intent was to separate mixtures of ethane and ethene. Several complex polymers and polymer composites had permeabilities and high selectivities for such separation. They could also be used for the separation of propene and propane. The high diffusivities of the alkenes have been found to be responsible for their higher permeabilities in the membranes. The polymers used in the membranes have interconnected ultramicropores with characteristic dimensions of about 4 A. Thus, the separation of the gas mixtures in these membranes is largely due to a molecular sieving effect inherent in the structure. The best polymers were homopolymers of poly-2,6-dimethyl-l,4phenyleneoxide (PPO) and copolymers of PPO with poly-2,6-diphenyl-l,4phenyleneoxide. Sergei R. Khairulin of the Boreskov institute believes that a promising process lies in the direct selective catalytic oxidation of hydrogen sulfide with oxygen: H2S + V202->S + H 2 0 Because the reaction produces sulfur directly, it can be carried out at lower temperatures and pressures. The reaction also happens to be exothermic, and it can be conducted in a fluidized bed. New honeycomb monolith catalysts are used. Khairulin claims that his new process will convert 99% of the hydrogen sulfide to elemental sulfur with a selectivity of 97 to 99%. The process has been tested in a refinery. At the Institute of Organo-Element

The American Chemical Society Presents Compounds in Moscow, Vladimir B. Shur has been developing a new ammo­ nia synthesis based on supported potas­ sium derivatives of anionic iron, rutheni­ um, and osmium carbonyl clusters. The catalysts are prepared by depositing K2[Fe6(CO)8] and similar entities on ac­ tive carbon followed by thermal decom­ position of the supported carbonylate and treatment with metallic potassium. The best catalysts show high activity, even at temperatures as low as 150 °C, but the highest activity is at 300 to 350 °G They are about five times more active than the conventional iron and rho­ dium catalysts. The carbonyls totally de­ compose in the reaction, but the catalyst is fairly stable, lasting about 10 to 12 hours. A key issue in developing unsteadystate processes for alkane oxidation is finding active catalytic materials and iden­ tifying the optimum catalyst states togeth­ er with the operating conditions that max­ imize selectivity. Chemical engineering professor John T. Gleaves of Washington University, St. Louis, has adapted a com­ mercial catalyst used for making maleic anhydride to the oxidation of C5 alkanes and alkenes in unsteady-state operation and has achieved dramatic improve­ ments in selectivity. The catalyst, (VO)2P207, has a unique storage-supply system capable of storing oxygen and efficiently channeling it to the active catalytic site. Gleaves propos­ es that the storage occurs via the trans­ formation of the catalyst into V5+ phases and that the supply mechanism involves the reverse reaction. Unsteady-state pro­ cessing is the medium to achieve this transformation. How generally applica­ ble the idea may be remains to be seen. Gleaves has conducted most of the experiments in this study in the sec­ ond-generation TAP (temporal analysis of products) reactor that he originally helped develop at Monsanto. The new TAP reactor is specially equipped for unsteady-state operation. And in the area of cleaning up vehicle emissions, Iselin, N.J.-based Engelhard Co. researcher Robert J. Farrauto de­ scribed for the first time a new catalytic technology for lowering particulates in diesel emissions to EPA requirements. Diesel emissions are more complex than those from the conventional gasoline en­ gine, Farrauto explains, because the die­ sel emissions contain solids (dry carbon, inorganic sulfate, and ash) and liquids (unburned fuel and lube oil), in addition to the usual gases (unburned fuel, car-

A

vital course for scientific professionals who need to know how to establish and maintain a quality program for laboratory safety and health and how to provide appropriate training

Enroll Today in One of These 1994 Sessions: April 11-13 Raleigh, NC

May 25-27 San Francisco, CA

Here's What You'll Learn About: Effective chemical storage systems Codes and standards governing safety and health in laboratories

How to store, handle, and control flammable hazards Ways to establish hazard identification and control measures

PLUS...

Major Causes of Accidents... Health Hazards of Chemicals... Protective Equipment... Measures to take to prevent Fires, Personal Injury, Health Impairment, or Interference with Laboratory Operations... AND MUCH MORE!

About the

Instructors

Norman V. Steere is a laboratory safety and design consultant who presents in-house safety and health courses for research organizations and consults on the design of laboratory and storage facilities. Maurice Golden is a chemical engineer who worked on the design and construction of specialized laboratory and production facilities before he retired from Eastman Kodak. Roger R. Conrad is a chemist who is Principal Safety Specialist for Corpo­ rate Research Services at Air Products and Chemicals, Inc. Gari T. Gatwood is a laboratory safety and design consultant who for many years served as manager of safety engineering and environmental sciences at Harvard University.

Register Today! Call the Continuing Education Short Course Office at (800) 227-5558 (Toll Free) or at (202) 872-4508. Or use the coupon below to request a free descriptive brochure on this unique course. Yes! Please send me information on the Laboratory Safety and Health Short Course to be held April 11-13, 1994, in Raleigh, NC, and May 25-27, 1994, in San Francisco, CA.

Ί

Name. Title— Organization _ Address City, State, Zip_ Mail or FAX to: American Chemical Society Dept. of Continuing Education Meeting Code LSH94 1155 Sixteenth Street, N.W. Washington, DC 20036 FAX: (202)872-6336

FEBRUARY 14,1994 C&EN 29

SCIENCE/TECHNOLOGY bon monoxide, and nitrogen oxides). Also, the sulfur in diesel fuel can be easily converted to sulfates in the combustion, adding the particulate emissions. Results from the Engelhard research indicate that a base metal oxide can dominate catalytic conversion of the volatile organic fraction (VOF) of the particulates to the level required by EPA. Such catalysts have two major requirements: They must reduce the VOF portion of the particulates, and they must not further oxidize significant quantities of the sulfur dioxide generated in combustion of the fuel. The precious-metal catalysts are active for both reactions, and a more selective catalyst is needed. Farrauto told the workshop that Engelhard had developed such base metal

catalysts, but because of proprietary reasons he refused to identify them further, except to say that they are nontoxic. These catalysts have been evaluated in heavyduty diesel service in flow-through honeycomb substrates, and several have been judged suitable for service. A second joint workshop is being considered for 1995 in Russia, according to Bell, Zamaraev, and Manzer. No date or venue has been determined but the hope is that it will be held in Moscow. The three were unanimous in their enthusiasm for the idea and there is further interest in integrating the workshop within the various catalysis communities in Europe, possibly in cooperation with the European Federation of Catalysis Societies.

First transgenic bull sires transgenic calves A major step in development of transgenic animals—animals genetically engineered to bear human genes—has been achieved by GenPharm International, a small Mountain View, Calif.-based biotechnology company. GenPharm's Herman, the world's first transgenic bull, has sired his first transgenic offspring. Like Herman, each calf carries a gene for production in cow milk of human lactoferrin (HLF). Lactoferrin, an orally active protein produced naturally in human milk, has antibacterial, iron transport, and other important properties. Herman was born in December 1990, and his birth was announced in August 1991 (C&EN, Sept. 2, 1991, page 7). A

team of scientists led by Gene Pharming Europe in Leiden, the Netherlands, a GenPharm subsidiary, produced the transgenic dairy calf by a novel in-vitro process. GenPharm is seeking patent protection on the gene construct, the method of introducing it into cows, the transgenic cows themselves, the use of proteins and milk from the cows, and other related technologies. Now, GenPharm's transgenic breeding program in Leiden has generated 55 bovine pregnancies by artificially inseminating heifers with semen from Herman. So far, 36 calves have been born, with the rest due by early April. Half of the calves produced by mating

Transgenic bull Herman poses with five of his transgenic offspring. 30

FEBRUARY 14, 1994 C&EN

Herman with nontransgenic heifers would be expected to be transgenic. GenPharm finds that 15 of the 36—almost half—are transgenic. About half of the 15 are females. "The birth of these transgenic calves demonstrates that the human gene carried by Herman has been stably transmitted," notes Jonathan J. MacQuitty, GenPharm's chief executive officer. 'Tierman and his offspring embody the first scientific proof that transgenesis in dairy cattle is feasible." During the next couple of years, MacQuitty tells C&EN, GenPharm plans to build up a herd of several hundred transgenic cows to enable large-scale production of HLF—thousands of kilograms a year. Milk from these cows likely will contain several grams of HLF per liter, and each cow is expected to produce 8,000 to 10,000 L of milk a year. Simple removal of water and milk fat will yield milk powder containing HLF for use as an ingredient in oral formulations. Eventually, GenPharm hopes to subcontract milk production to farmers or dairy co-ops. The market for HLF, MacQuitty explains, lies in providing protection to populations particularly at risk for bacterial infections of the gastrointestinal tract. This includes cancer patients whose immunity is lowered by chemotherapy, AIDS patients, and premature infants. The infant formula market alone totals $5 billion worldwide, he points out. GenPharm views transgenic dairy cattle as the only commercially viable route to making sufficient HLF quantities for therapeutic use. GenPharm scientists also have introduced HLF gene constructs into transgenic mice. They find that the mice's milk contains HLF identical to that from humans, and that the genes are passed on to the next generation. MacQuitty expects "a very limited set of regulatory problems" with HLF, considering that "it's nature's way in milk," and that there is a long history of research on milk proteins. However, GenPharm was prevented from starting the clinical trials it planned in 1993 on HLF from Herman's female offspring. Herman was not allowed to breed until the Dutch Parliament finished debating the ethics of such activity. Only in January 1993 was Herman given a green light to breed. Thus, GenPharm now expects to have enough HLF to start trials only at the end of 1994. Richard Seltzer