TECHNOLOGY
Dow Develops Catalytic Method To Produce Higher Mixed Alcohols Process provides a way to use synthesis gas from natural gas sources to make higher mixed alcohols—a potential blending stock for gasoline Dow Chemical has developed a new catalytic process for the coproduc tion of methanol and higher mixed alcohols. The higher alcohols are predominantly straight-chain termi nal alcohols in the C2-C5 range. By manipulating the composition of the catalyst and such reaction conditions as pressure and temperature, it is possible to vary within wide limits the ratio of methanol to higher alco hols produced. Michael J. Mintz, director of re search and development in Dow's organic chemicals department, de scribed the new process as an out growth of a long-term development project in Fischer-Tropsch chemistry. Although there is no need at present to increase world methanol capacity, the availability of the coproduct, higher alcohols, does offer chemical producers and refiners an attractive way to use synthesis gas, particular ly that produced from isolated natu ral gas sources. The principal use foreseen for the alcohol mixtures is as a high-octane blending stock for gasoline. In the Dow process, the methanol concentration can be varied from zero to 90% and the octane number for the mixed alcohols can be as high as 120. Dow believes that the increased octane ratings from its mixed alcohols will cost 30 to 50% less than comparable increases from other processes. The new process is keyed to two specific developments. The first is
the development of rugged, selec tive catalysts. The catalysts of choice are agglomerated molybdenum sul fides made by thermal decomposi tion of thiomolybdates. These cata lysts can be used alone or in combi nation with other catalysts. One of the leaders in the catalyst develop ment is Craig B. Murchison, asso ciate scientist at Dow's Michigan laboratories. He notes that because the catalyst is already // sulfided, // it is extremely resistant to poisoning by residual sulfur in the synthesis gas. Sulfur poisoning is a major problem in a number of other pro cesses and usually requires a zinc oxide guard bed to reduce sulfur levels in the synthesis gas before it can be admitted to the reactor. The Dow process requires no guard beds. Murchison says that extensive test ing of the catalysts for up to nine months has shown no significant deterioration of activity or change in selectivity. Furthermore, unlike conventional Fischer-Tropsch cata lysts, the Dow catalysts are not prone to carbon buildup. This reduced coking tendency permits the use of synthesis gases with hydrogen to carbon monoxide ratios as low as 0.7 to 1. In some installations, the low ratios often would eliminate the need for water-gas shift reactions. The catalysts have been studied in both fluid-bed and fixed-bed pi lot-plant reactors capable of process ing up to 1 ton per day of synthesis gas. Both types of reactors have been thoroughly modeled. Although the fluid-bed reactor provides better heat transfer and closer tempera ture control, the rugged nature of the catalyst does not require the fluid bed. Fixed beds are simpler to operate and can produce the mixed alcohol product in a stable manner. The second key development is a low-energy method of drying the
finished alcohols. According to George J. Quarderer, associate scien tist in process research for Dow, the process yields a product with an unusually low water content. The Dow technique removes most of the water that remains in the finished alcohols with a system of zeolite units that greatly reduces the cost of drying over that of the more con ventional technology. In a typical mixed alcohol producer, as much as 8% of the product is water, which is usually removed by distillation. Be cause the usual product mix con tains up to three potential binary azeotropes, drying by distillation can
Dow's reactor works in standard mixed-alcohol plant Oxygen plant
jr o 2 Methane—•
Partial oxidations
^r C0 2 scrubber
—•Net C02
τ> Reactor recycle
Synthesis reactor
•
Reactor purge
r
Vapor/liquid separation r
Alcohol drying
1
Dry alcohols November 12, 1984 C&EN
29
ORGANIC INTERMEDIATES FROMSWITZERLANDI for • pharmaceuticals • agrochemicals • dyestuffs
· · ·
flavors fragrances photochemicals
3,4-Methylenedioxyanlllne and N-Ethyl3,4-methylenedioxyaniline
CHO
3-Nitrobenzaldehyde rfg^
Nitroterephthalic acid C00CH dimethyl ester (fa*0* C00CH3
2-Ethylaniline
NH2 C2H5
Technology be very expensive. Typically, says Quarderer, up to 7 lb of steam per lb of mixed alcohols is required to reduce the water content to below 1%. Without loss of alcohols, the Dow process provides a product with as little as 0.2% water. Two scaled-up designs have been prepared for the synthesis of mixed alcohols. One is for a 10 ton-perday prototype plant and the other for a 1.3 billion lb-per-year (1900 ton-per-day) commercial plant. Mintz says that each assumes that the synthesis gas is obtained from the partial combustion of natural gas, a feedstock that is generally available and has readily assessed, commercial value. The prototype plant design can be used as the basis for actual construction. Dow doesn't plan on getting into the mixed alcohol business, however. It would prefer to license the technology and is negotiating with licensing firms to that end. Much of the acceptance of the technology depends on the future incorpora-
tion of high-octane mixed alcohols in motor fuels. In turn, that depends on the results of a current petition to the Environmental Protection Agency by Du Pont, requesting permission to blend more alcohol into unleaded gasoline (C&EN, July 16, page 9). In August, EPA stated that it intended to cut lead use in gasoline 91% by Jan. 1, 1986, and totally ban its use by 1995. If this schedule holds up, it more or less defines the time limits for introducing large quantities of new octane boosters for gasoline. Most new octane boosters can be produced in refineries. The Dow process offers an independent source that, in addition, is potentially applicable to nearly all sources of synthesis gas. Not the least of these may be the remote natural gas wells that currently are being flared either because the gas has no local value or because there are no means of transporting it to a processing plant. Joseph Haggin, Chicago
Aminomalonic acid diethyl ester Acetylaminomalonic acid diethyl e 8 t e r
3,5-DiCHLOROANiUNE
COOC2H5 CHNH2 HCI COOC2H5
OH
f^]..phloroglucinol
Ν - Hydroxyphthalimide co„;NOH
0 Js \^>^0H
CO
Isosorbide dinitrate (ISDN) mixtures with lactose, etc. USP XX Our traditional processes: • nitration • catalytic hydrogénation and other reactions
US Agents: HENLEY + CO., INC. 750 THIRD AVENUE NEW YORK, NY 10017 Phone (212) 986-5544
SSF= DOITIKOIM Swiss Explosives Works Ltd. CH-5605 Dottikon/Switzerland Phone 057/26 11 55 Telex 52 694 ssf ch A privately owned Swiss enterprise 30
November 12, 1984 C&EN
The other organic intermediates f r o m us:
N02
(1,3,5-trihydroxybenzene)
OP
2,4-dichloronitrobenzene
[ O ; · meta-dichlorobenzene Ο Cl
JO;
ISK
3,5-diaminochlorobenzene
Η2ΝΛν^>^ΝΗ2
1,3,5-trichlorobenzene ISHIHARA SANGYO KAISHA, LTD. 10-30, Fujimi 2-Chome, Chiyoda-ku, Tokyo, Japan T e l e x : 2 3 2 4 3 0 6 ISK J ISHIHARA CORPORATION (U.S.A.)
Trans
america Pyramid 41st Floor 600 Montgomery St., San Fran cisco, Ca.94111 Tel:41 5-421-8207 Telex : 278010 ICUSA UR I S K ( E U R O P E ) S . A . / 3 3 31 Rue Montoyer. Box 8 1040 Bruxelles T e l : ( 0 2 ) 5 1 2 - 5 4 - 5 0 - 5 1 2 - 7 2 - 7 8 Telex:23362 ITDD Β
