Exxon's Patrick Grimes tests shunt current protection in zinc-bromine battery
dead," Grimes says about the effect of protective currents for the zinc-bro mine battery. "With it we are doing very nicely. We now have no problems with shunt current. Each cell now acts as if it were independent of its neighbors. We could, in principle, stack as many plates as we wanted into a single series." Exxon's zinc-bromine battery uses a system of bipolar electrodes con nected in series with a common elec trolyte flowing past them. This con-
figuration was chosen for a number of reasons. One important one is that it gives a low current and high volt age—a combination that allows the electrodes to be made from light weight and low-cost carbon plastic rather than highly conducting metals such as silver or titanium, Bellows explains. However, the configuration leads to shunt currents that increase in importance as the number of cells in the series increases. Relatively long series of cells will be needed to make batteries with enough storage capac ity to be practical in cars. Similar cost considerations make series batteries and flowing electro lytes attractive for many other elec trochemical processes, Grimes says. These include chlor-alkali produc tion, production of metals such as aluminum or magnesium, many or ganic and inorganic chemical syn theses, fuel cells, and electrodialysis. In all these systems, shunt currents cause problems, he says, that protec tive currents may help to solve. At least Exxon hopes so. The com pany recently has patented the pro tective current approach to elimi nating shunt current effects [U.S. Patent 4,197,169 (Zahn)] and hopes to license it broadly. Rebecca Rawls, Washington
Soviet underground coal gasification on the rocks The latest look at Soviet underground coal gasification indicates that the Soviet program has all but ceased. Appraisers at Lawrence Livermore Laboratory note that in the early 1950's the Soviets had developed highly successful operational tech niques for both flat-seam and steeply dipping-seam gasification. The orig inal plans had called for a major effort to supply up to 41 Χ 109 eu m per year of fuel gas with a typical heating value of 1000 kcal per eu m by 1958. This was considered a full-scale commer cial development plan that would consume up to 300,000 tons per year of coal, mostly in fields located near Moscow, Tashkent, the Donets Basin, and Siberia. In fact, gas production peaked out in 1966 at about 2 billion eu m per year and has dwindled ever since. One reason for declining gas pro duction from underground coal gas ification in the Soviet Union is be lieved to be poor performance from · several test burns at Angren near Tashkent. Most of the problems ap pear to center on lack of proper spacing of the holes drilled into the coal seams, according to the Lawrence Livermore experts. Bores spaced on 30- to 40-m grid spacings are consid ered commercially attractive, but the
evidence suggests that the Soviets used much closer spacing, meaning greater drilling costs. The expense may have foredoomed the project. The heating value from the Angren tests and elsewhere does not appear to have achieved predicted values by any more than 20%. This adds to the economic penalties. One of the most crucial problems cited by the Lawrence Livermore appraisers may have been caused by unfavorable geology in the test fields. Gas losses through a porous over burden have been as much as 26% when calculated by non-Soviet methods. If true, this would add an other 33% to the cost of the product fuel gas. Most data on Soviet experience with underground coal gasification come from a few Soviet publications and from reports by western techni cians who have visited the Soviet test sites on a reciprocal basis. The Soviets told Canadians in 1975 that under ground gasification in the Soviet Union was having trouble competing economically with natural gas and with open-pit lignite mining. Likewise the low heating value of the fuel gas did not permit its being transported very far away from the burn site. Since most of the burn sites were in
remote areas, this could make serious commercialization impossible. The Lawrence Livermore analysts calculate that in the U.S., an under ground burn conducted under favor able circumstances could provide a fuel gas with a heating value of 125 Btu per scf at a cost about 35% less than that from a conventional Lurgi gasifier, which is more or less a ruleof-thumb standard for such calcula tions. Though admittedly optimistic, such values generally have been re alized in the U.S. trials conducted so far. Applying the same calculations to the available Soviet data indicates that the Soviet gas products cost as much as 132% of the standard Lurgi value. The Soviets are saying nothing about all of this, and the Lawrence Livermore analysts admit to consid erable speculation. But the fact re mains that anticipated Soviet activity has failed to materialize. The demise of the Soviet effort is doubly sur prising considering the many major technical contributions from Soviet workers over the past 20 or 30 years. Other reasons offered for this de mise are a lack of good underground diagnostics before and during a burn, and lack of a good laboratory support program. Lack of good diagnostics is usually manifested in erratic results from the field, where gas quality varies greatly. This has been the case in some of the Soviet trials. Likewise, laboratory support in instrumenta tion and control permits optimization of the field layout as well as control of combustion below ground. D
Catalysts allow CO, C0 2 comethanation Catalysis chemists at Japan's Kyoto University have developed a series of composite catalysts that permit si multaneous methanation of carbon monoxide and carbon dioxide in mixtures with hydrogen. Aside from the considerable simplifications that this development may provide for Fischer-Tropsch syntheses, it also may indicate a long-sought route toward direct use of carbon dioxide as a recyclable material in industrial processes. The methanation of carbon mon oxide with hydrogen classically takes place over stable nickel catalysts at high temperatures, and the reaction is highly exothermic. This reaction is basic to many reaction sequences using synthesis gas. It also has func tioned in applications such as purifi cation of reactant gases for ammonia synthesis, in which carbon monoxide has been shown to inhibit some amOct. 13, 1980 C&EN
21
Derivatives of Isophthalonitrile (IPN) like /77-xylylenediamine (MXDA) CH 2 NH 2
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N H
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C&ENOct. 13, 1980
monia conversion catalysts and must be removed from the feed gases. Carbon dioxide is usually an unwanted diluent in most industrial reactant gases and is vented to the atmosphere as a nontoxic effluent. In several important syntheses, such as the shift reaction in methanation, carbon dioxide sometimes is even considered a rate suppressant and must be removed. It has been considered economically important to find a simpler way to accommodate the presence of carbon dioxide. The best way probably would be to use carbon dioxide as a reactant, which also would provide a possible route to the recycle of carbon resources without so much environmental impact. The trials conducted at Kyoto indicate that the best comethanation catalysts are small amounts of lanthanide oxides on iron group substrates with platinum group metals as promoters. A typical composition would be 5% Ni, 2.7% La 2 0 3 , and 0.6% Ru. This would be supported on spherical silica pellets with a diameter of 3 mm and having pores with a bimodal size distribution between 5 and 600 nm. Catalyst development and comethanation process design were carried out at atmospheric pressure in a conventional tubular reactor having pellets arranged in single file in the tube. Temperature was controlled between the extremes of 160° and 400° C and the space velocities of the gases were controlled between 10,000 h " 1 and 220,000 h." 1 The reactant gas mixtures were composed of 6% carbon monoxide, 6% carbon dioxide, and 88% hydrogen. At low temperatures the methanation rate of carbon monoxide alone is greater than that for carbon monoxide. However, the Kyoto researchers found that in mixtures of the two oxides the reverse is true. There is considerable variation with temperature and a very complex adsorption sequence involved. However, complete conversion of both oxides has been achieved at temperatures as low as 270° C. One observer, noting that it appears that the absorption of monoxide is much stronger than dioxide, suggests that the active catalyst might be some kind of adsorbate-surface metal intermediate. Just why the comethanation rate is so greatly enhanced has not been explained fully yet, but evidence obtained so far suggests that the presence of carbon dioxide somehow enhances carbon monoxide methanation at higher temperatures. Neither the presence of water vapor nor a water-carbon monoxide shift effect seems to have any bearing on the reaction. •
Fill a Staff Position on Capitol Hill Two ACS Congressional Fellowships Available To Begin Fall 1981 The objectives of the fellowship program are: • To provide an opportunity for scientists to gain firsthand knowledge of the operations of the legislative branch of the federal government, • To make available to the government an increasing amount of scientific and technical expertise, and • To broaden the perspective of both the scientific and governmental communities regarding the value of such scientific-governmental interaction.
Applications should be submitted by January 30, 1981 to: Dr. Annette T. Rosenblum Department of Public Affairs American Chemical Society 1155—16th St., N.W. Washington, D.C. 20036
Applications consist of a letter of intent, resume, and two letters of reference. The letter of intent should include a description of the applicant's experience in publicoriented projects in which scientific or technical knowledge was used as a basis for interaction and a statement that tells why they have applied for the Fellowship and what they hope to accomplish as an ACS Congressional Fellow. The resume should describe the candidate's education and professional experience and include other pertinent personal information. Letters of reference should be solicited from people who can discuss not only the candidate's competence but also the applicant's experience in publicoriented projects. Arrangements should be made to send the letters of reference directly to ACS. For further information call (202) 872-4383.
