50 Years of Catalysis

1st DECADE: 1949 — 1958

  • Late 1940s to Ear­ly 1950s — Robert M. Mil­ton and Don­ald W. Breck, Union Car­bide, devel­op com­mer­cial syn­the­sis for zeo­lites — A, X, and Y types.
  • Late 1940s — Eugene Houdry devel­ops mono­lith­ic plat­inum cat­a­lyst sys­tem for
  • Ear­ly 1950s — Treat­ing exhaust gas­es from inter­nal com­bus­tion engines, founds — and begins com­mer­cial oper­a­tions at Yard­ley, Penn­syl­va­nia. Houdry is lat­er induct­ed into the Inventor’s Hall of Fame.
  • June 11, 1949 — First meet­ing of orga­ni­za­tion that became the Catal­y­sis Club of Philadel­phia was held at the Uni­ver­si­ty of Penn­syl­va­nia. Paper were pre­sent­ed by R. C. Hans­ford (Mobil), A. G. Oblad (Houdry), A. V. Grosse (Tem­ple U), T. I. Tay­lor (Colum­bia U.) and K. A. Krieger (U. Penn­syl­va­nia). A. Farkas, orga­niz­er of this sym­po­sium, was select­ed chair­man of a com­mit­tee to form a per­ma­nent orga­ni­za­tion.
  • Decem­ber 1949 — Prof. Paul Emmett pre­sent­ed a lec­ture at Tem­ple Uni­ver­si­ty and after­wards the Catal­y­sis Club of Philadel­phia was offi­cial­ly formed, elect­ing A. Farkas chair­man and A. Oblad as Sec­re­tary-Trea­sur­er. Almost one hun­dred signed up as mem­bers.
  • 1949 — First com­mer­cial oper­a­tion of UOP’s Plat­form­ing Process for naph­tha reform­ing, Old Dutch Refin­ing, Muskegon, Michi­gan; patents for Pt-Cl-Al2O2 cat­a­lysts to Vladimir Haensel.
  • 1949 — P. W. Sel­wood pub­lished his first paper on nuclear induc­tion and begins a series of clas­sic pub­li­ca­tions on the appli­ca­tion of mag­net­ic tech­niques in catal­y­sis. The results are sum­ma­rized in his book [P. W. Sel­wood, “Adsorp­tion and Col­lec­tive Para­mag­net­ism,” Aca­d­e­m­ic Press, 1962.]
  • March 2, 1950 — The Bylaws of the Catal­y­sis Club of Philadel­phia, as writ­ten by Grace Kennedy (wife of Robert Kennedy, promi­nent catal­y­sis sci­en­tist at Sun Oil), were adopt­ed and still serve as the mod­el for lat­er formed clubs/societies.
  • 1950 — MILESTONE MEETING: The Dis­cus­sions of the Fara­day Soci­ety, Het­ero­ge­neous Catal­y­sis, No. 8, 1950. Top­ics includ­ed:
    • O. Beeck, Relates % d-char­ac­ter of met­al and cat­alyt­ic activ­i­ty for eth­yl­ene hydro­gena­tion.
    • D. D. Eley, Cal­cu­lates the heat of adsorp­tion of hydro­gen on met­als.
    • G. M. Schwab, Alloy cat­a­lysts for dehy­dro­gena­tion.
    • D. D. Dow­den and P. W. Reynolds, Elec­tron­ic effects in catal­y­sis by met­al alloys.
    • P. W. Sel­wood and L. Lyon, Mag­net­ic sus­cep­ti­bil­i­ty and cat­a­lyst struc­ture.
    • M. W. Tamele, Sur­face chem­istry and cat­alyt­ic activ­i­ty of sil­i­ca-alu­mi­na cat­a­lysts.
  • John Turke­vich, H. H. Hubbell and James Hilli­er, Elec­tron microscopy and small angle X-ray scat­ter­ing.
  • 1950 — Lin­ear rela­tion­ship between quino­line chemisorp­tion and cat­alyt­ic activ­i­ty for gasoil crack­ing — G. A. Mills, E. R. Boedek­er and A. G. Oblad, JACS, 72, 1554 (1950).
  • 1950 — Hydro­formy­la­tion cat­alyt­ic species iden­ti­fied as HCo(CO)4 — I. Wen­der, M. Orchin and H. H. Storch, JACS, 72, 4842 (1950).
  • 1951 — A. Wheel­er defines role of dif­fu­sion in deter­min­ing reac­tion rates and cat­alyt­ic selec­tiv­i­ty — Advan. Catal., 3, 250–326 (1951).
  • 1951 — Paul Emmett uti­lizes 14C radioiso­tope in Fis­ch­er-Trop­sch mech­a­nism stud­ies — New York Times reports that “Gulf Oil sci­en­tist makes radioac­tive gaso­line.”
  • 1953 — Naph­tha reform­ing involves dual func­tion­al cat­a­lysts — mech­a­nism for reform­ing with these cat­a­lysts — G. A. Mills, H. Heine­mann, T. H. Mil­liken and A. G. Oblad, Ind. Eng. Chem., 45, 124 (1953).
  • 1953 — Karl Ziegler dis­cov­ers a cat­a­lyst sys­tem for poly­mer­iz­ing eth­yl­ene at low tem­per­a­ture and pres­sure to pro­duce lin­ear, crys­talline poly­eth­yl­ene- Nobel Prize award­ed to Ziegler in 1963.
  • 1954 — Gue­lio Nat­ta invents stere­ospe­cif­ic poly­mer­iza­tion of propy­lene to pro­duce crys­talline polypropy­lene- Nobel Prize award­ed to Nat­ta in 1963.
  • 1954 — “Begin­ning” of cat­a­lyst char­ac­ter­i­za­tions using instru­ments with i.r. spec­tra for CO adsorp­tion on cop­per (R. P. Eis­chens, W. A. Pliskin and S. A. Fran­cis, J. Chem. Phys., 22, 1786 (1954)). This pio­neer­ing work soon includ­ed approach­es to char­ac­ter­ize active sites for adsorp­tion on met­al, met­al oxide and acidic sites as well as dis­tin­guish­ing Brøn­st­ed and Lewis acid sites.
  • 1954 — John P. Hogan and R. L. Banks, Phillips Petro­le­um, dis­cov­ers chro­mia cat­a­lyst for poly­eth­yl­ene pro­duc­tion.
  • 1954 — B.F. Goodrich (S. E. Horne) and Gulf Oil announce use of Ziegler cat­a­lyst to poly­mer­ize iso­prene to dupli­cate nat­ur­al rub­ber.
  • 1955 — Sasol begins com­mer­cial oper­a­tion of Fis­ch­er-Trop­sch cir­cu­lat­ing flu­id bed reac­tors.
  • 1956 — Phillips Process — high pres­sure (500 psi) in hot sol­vent with sup­port­ed chro­mia cat­a­lyst did not, on the sur­face, look attrac­tive com­pared to Ziegler-Nat­ta; how­ev­er, engi­neer­ing advances, cheap and high activ­i­ty cat­a­lyst, and ever increas­ing scale made the Phillips Process the world’s lead­ing source of poly­eth­yl­ene.
  • 1956 — First Inter­na­tion­al Con­gress on Catal­y­sis held in Philadel­phia — more than 600 atten­dees. Orga­niz­ing the Inter­na­tion­al Con­gress on catal­y­sis was con­ceived by the Catal­y­sis Club of Philadel­phia and received endorse­ment from the Catal­y­sis Club of Chica­go, the Uni­ver­si­ty of Penn­syl­va­nia, and the Nation­al Sci­ence Foun­da­tion. [At the end of the acknowl­edg­ments it is not­ed the the orga­ni­za­tion of the Con­gress was planned by RL Bur­well, Jr, A Farkas, AV Grosse, H Heine­man, WR Kirn­er, KA Krieger, JM Mav­i­ty, AG Oblad and CL Thomas. The orga­niz­ers includ­ed peo­ple from Chica­go.]
  • 1957 — On June 18, Her­cules opens the first Zigler cat­a­lyst based plant in the U.S.
  • 1958 — Merox Mer­cap­tan Oxi­da­tion Process _ UOP.
  • 1953 to 1959 — Patents grant­ed in these years led to the com­mer­cial pro­duc­tion of three sig­nif­i­cant lin­ear poly­olefins: high-den­si­ty poly­eth­yl­ene (1955- 56 by Hoechst, W.R. Grace, Her­cules and Phillips), polypropy­lene (1957–8 by Her­cules, Mon­te­can­ti­ni and Hoechst) and stereo-spe­cif­ic rub­bers (1958–9 by Goodrich-Gulf, Phillips and Shell).

 

2nd DECADE: 1959 — 1968

  • 1960’s — Major advances in het­ero­ge­neous pho­to­catal­y­sis
  • 1960’s — Cat­alyt­ic advances to allow low-tem­per­a­ture water-gas shift
  • 1960s — Sci­en­tif­ic Design devel­oped process­es to make chlo­ri­nat­ed sol­vents and male­ic anhy­dride. A major break­through was the devel­op­ment of a cat­a­lyst to oxi­dize p-xylene into puri­fied ter­phthal­ic acid.
  • 1960s — Devel­op­ment of the con­cepts of demand­ing and facile met­al cat­alyzed reac­tions — intro­duced by Boudart and cowork­ers. M. Boudart, Adv. Catal., 20, 153 (1969)
  • 1959 — Obser­va­tion of olefin metathe­sis at Phillips Petro­le­um — R. L. Banks and G. C. Bai­ley, Ind. Eng. Chem. Prod. Res. Dev., 3, 170 (1964); R. L. Banks, “Dis­cov­ery and Devel­op­ment of Olefin Dis­pro­por­tion­a­tion (Metathe­sis)” in “Het­ero­ge­neous Catal­y­sis: Select­ed Amer­i­can His­to­ries,” (B. H. Davis and W. P. Het­tinger, Jr., Eds.), ACS Symp. Series, 222, 403 (1983)).
  • 1959 — Dab­co (trimeth­yl­ene diamine) was intro­duced by Houdry Corp. as a cat­a­lyst for the pro­duc­tion of ure­thane foams from iso­cyanates and alco­hols.
  • 1959 — Nal­co intro­duces 1/16″, and lat­er 1/32,” extru­date CoMo- alu­mi­na hydrotreat­ing cat­a­lysts and intro­duced in Exxon Bay­town refin­ery.
  • 1960 — Eth­yl­ene to acetalde­hyde — Wack­er Chem­istry
  • 1960 — UOP intro­duces Hydrar Process for con­vert­ing ben­zene to cyclo­hex­ene.
  • 1960 — Com­ple­tion of Sohio’s acry­loni­trile plant at Lima, Ohio, based upon cat­a­lyst dis­cov­ered by J. D. Idol.
  • 1961 — Par­ing reac­tion in hydro­c­rack­ing, R. F. Sul­li­van, C. J. Egan, G. E. Lan­glois and R. P. Sieg, JACS, 83, 1156 (1961).
  • 1962 — Steam reform­ing with NiK2Al2O3
  • 1962 — Obser­va­tion of reversible bind­ing of H2 and C2H4 by Vaska’s Com­plex, IrCl(CO)(PPh3)2, L. Vas­ka and J.W. DiLuzio, JACS, 84, 679 (1962).
  • 1962 — Jour­nal of Catal­y­sis, the first sci­en­tif­ic jour­nal devot­ed sole­ly to catal­y­sis, begins pub­li­ca­tion with J. H. de Boer and P. W. Sel­wood as edi­tors.
  • 1962 — Descrip­tion of “Vaska’s Com­plex,” the first to show reversible bond­ing of hydro­gen and ethene with­in the coor­di­na­tion sphere (L. Vas­ka and J. W. D. Luzio, JACS, 84, 679 (1962)).
  • 1963 — Sachtler proves, using 14C-labeled propene, that a p-allyl com­plex is formed dur­ing propene oxi­da­tion (W. M. H. Sachtler, Rec. Trav. Chim., 82, 243 (1963)).
  • 1963 — Ammox­i­da­tion of propene to acry­loni­trile.
  • 1963 — The­o­ret­i­cal mod­el for describ­ing ele­men­tary redox reac­tions for elec­trodes (R. A. Mar­cus, J. Phys. Chem., 43, 679 (1963)).
  • 1964 — Intro­duc­tion of rare earth met­al sta­bi­lized X-zeo­lite for cat­alyt­ic crack­ing by Mobil Oil — C. J. Plank, E. J. Rosin­s­ki and W. P. Hawthoren, 3, 165, (1964). Plank and Rosin­s­ki in the Inven­tors Hall of Fame.
  • 1964 — Olah announces “Mag­ic Acid,” a mix­ture of HF and SbF5 reacts with hydro­car­bons to pro­duce sta­ble car­bo­ca­tions that are observ­able using NMR. G. Olah award­ed the 1994 Nobel Prize in Chem­istry.
  • 1964 — Olefin metathe­sis announced [R. L. Banks and G. C. Bai­ley, Ind. Eng. Chem, Prod Res. Dev., 3 170 (1964)] com­mer­cial­ized in 1966.
  • 1964 — Mech­a­nism for hydro­c­rack­ing — H. L. Coon­radt and W. E. Gar­wood, Ind. Eng. Chem., Process Design Dev., 3, 38 (1964).
  • 1964 — K. Tamaru sum­ma­rizes tran­sient cat­alyt­ic stud­ies empha­siz­ing IR tech­niques (Adv. Catal., 15, 65 (1964)).
  • 1964 — Spillover of Hydro­gen from Pt/Al2O3 to WO3 (S. Khoobiar, J. Phys. Chem., 68, 411 (1964)).
  • 1964 — Bly­hold­er (J. Phys. Chem., 68, 2772 (1964)) sug­gest­ed that CO adsorp­tion on tran­si­tion met­als can be described by a mol­e­c­u­lar orbital pic­ture of two con­tri­bu­tions to bond­ing, par­tial dona­tion of CO-5s charge to met­al ds orbitals and back dona­tion from met­al dp to CO 2p* anti­bond­ing orbitals.
  • 1964 — Start­up by Mon­san­to of the world’s first biodegrad­able deter­gents plant based upon C10-C14 lin­ear olefins obtained by selec­tive cat­alyt­ic dehy­dro­gena­tion of n-paraf­fins.
  • 1965 — Wilkinson’s homo­ge­neous hydro­gena­tion cat­a­lyst, J.F. Young, J.A. Osborn, F.H. Jar­dine and G. Wilkin­son, Chem. Com­mun., (1965) 131. G. Wilkin­son is the 1973 Nobel Lau­re­ate in Chem­istry.
  • 1966 — ICI devel­oped a mod­er­ate-pres­sure, low-tem­per­a­ture methanol syn­the­sis process employ­ing a Cu-ZnO/Al2O3 cat­a­lyst in a gas-recy­cle reac­tor.
  • 1966 — Intro­duc­tion of con­cept of hard and soft acids and bases to catal­y­sis (R. G. Pear­son, Sci­ence, 151, 172 (1966)).
  • 1966 — Devel­op­ment of a method to cal­cu­late the coor­di­na­tion num­bers of sur­face atoms in the sta­ble forms of small met­al par­ti­cles (R. van Hard­e­veld and A. van Mont­foort, Sur­face Sci., 4, 396 (1966)).
  • 1967 — Intro­duc­tion of first bimetal­lic naph­tha reform­ing cat­a­lyst — Pt-Re-Al2O3 — need for pre­sul­fi­da­tion of a naph­tha reform­ing cat­a­lyst.
  • 1967 — Catal­y­sis Reviews begins pub­li­ca­tion with H. Heine­mann as edi­tor.
  • 1967 — Atlantic Rich­field and Hal­con (for­mer­ly Sci­en­tif­ic Design) formed a joint ven­ture, Oxi­rane, to pro­duce styrene, propy­lene oxide and tert-butyl alco­hol.
  • 1967 — Sum­maries of Lin­ear Free Ener­gy Rela­tion­ships (LFER) in Het­ero­ge­neous Catal­y­sis (M. Kraus, Adv. Catal., 17, 75 (1967); I. Mochi­da and Y. Yone­da, J. Catal., 7, 386 (1967)).
  • 1968 — Shape selec­tive catal­y­sis — Selecto­form­ing with eri­on­ite.

 

3rd DECADE: 1979 — 1988

  • 1970’s — Rh-cat­alyzed hydro­formy­la­tion of propene.
  • 1970’s — Improved selec­tiv­i­ty for oxi­da­tion of ethene to eth­yl­ene oxide using Cs (or Cl) pro­mot­ed Ag cat­a­lysts.
  • 1970’s — Intro­duc­tion of use of con­trolled atmos­pher­ic trans­mis­sion elec­tron microscopy for cat­a­lyst char­ac­ter­i­za­tion and kinet­ics of catal­y­sis.
  • 1972 — Exten­sive stud­ies of met­al alloy cat­a­lysts by Sin­felt and cowork­ers results in demon­stra­tion of dif­fer­ent activ­i­ty pat­terns as alloy com­po­si­tion changes for the hydrogenol­y­sis of ethane to methane and dehy­dro­gena­tion of cyclo­hexa­ne to ben­zene (J. H. Sin­felt, J. L. Carter and D. J. C. Yates, J. Catal., 24, 283 (1972)).
  • 1974 to 1975 — UOP Purzaust Auto Exhaust Treat­ment sys­tem accept­ed by Chrysler and is installed on 1975 mod­els.
  • 1974 — F. Sher­wood Roland and M. Moli­na dis­cov­er chlo­rine-cat­alyzed ozone deple­tion in the atmos­phere.
  • 1975 — B. Del­mon orga­nizes the first meet­ing for the Sci­en­tif­ic Basis for the Prepa­ra­tion of Het­erog­neous Cat­a­lysts.
  • 1975 — State of dis­per­sion of small Pt and Pd met­al par­ti­cles in zeo­lites (P. Gal­ley­ot et. al., J.Catal., 39, 334 (1975)).
  • 1975 — Demon­stra­tion that poi­sons of metal­lic cat­a­lysts are selec­tive, decreas­ing rates of struc­ture-sen­si­tive and struc­ture-insen­si­tive reac­tions dif­fer­ent­ly (R. Mau­rel, G. Lecler­cq and J. Bar­bi­er, J. Catal., 37, 324 (1975)).
  • 1976 — Mobil Oil man­age­ment announces the dis­cov­ery of methanol-to-gaso­line con­ver­sion using their ZSM-5 zeo­lite cat­a­lyst (Chemtech, 6, 86–9 (1976)).
  • 1978 — Dis­cov­ery of the strong met­al sup­port inter­ac­tion (SMSI) and its role in alter­ing the adsorp­tive prop­er­ties of the met­al func­tion. (S. J. Tauster, S. C. Fung and R. L. Garten, JACS, 100, 170 (1978)).
  • 1979 — Ten­nessee East­man selects rhodi­um as cat­a­lyst for pro­duc­ing acetic anhy­dride from coal.

 

4th DECADE: 1979 — 1988

  • 1980’s — Intro­duc­tion of SCR (Selec­tive Cat­alyt­ic Reduc­tion) for NOx con­trol on sta­tion­ary pow­er gen­er­a­tors.
  • 1980’s — New cat­alyt­ic tech­nol­o­gy com­mer­cial­ized in the U.S. dur­ing the 1980’s (J. Armor, Appl. Catal., 78, 141 (1991)).
  • 1980’s — Union Car­bide and Shell devel­op the UNIPOL process for lin­ear low-den­si­ty poly­eth­yl­ene, which allows pre­cise con­trol over the product’s mate­r­i­al prop­er­ties. The process was extend­ed to polypropy­lene in 1985.
  • 1980’s — Demon­stra­tion that strong­ly elec­troneg­a­tive ele­ments rel­a­tive to nick­el mod­i­fy chemisorp­tive behav­ior far more strong­ly than a sim­ple site- block­ing mech­a­nism would allow, sup­port­ing an elec­tron­ic effect (D. W. Good­man, “Chem. Phys. Sol­id Surf.,” Springer-Ver­lag, 1986, pp. 169–195.
  • 1980’s — Exper­i­men­tal evi­dence demon­strat­ing the restruc­tur­ing of sur­faces dur­ing cat­alyt­ic reac­tions — e.g., the con­ver­sion of eth­yl­ene to eth­yli­dyne with expan­sion of the met­al atoms around the car­bon atom (R.J. Koest­ner, M. A. Van Hove and G. A. Somor­jai, Surf. Sci., 121, 321 (1982) and show­ing the par­al­lel restruc­tur­ing of Pt and oscil­la­tion in CO oxi­da­tion (G. Ertl, Ber. Buns. Phys. Chem., 90, 284 (1986)).
  • 1980 — Very rapid ethene poly­mer­iza­tion by homo­ge­neous cat­a­lyst (CP2 Zr (CH3)2 acti­vat­ed with cocat­a­lyst alu­mi­nox­ane) (H Sinn et. al., Angew. Chem., 92, 396 (1980)).
  • 1981 — Applied Catal­y­sis begins pub­li­ca­tion with B. Del­mon as Edi­tor-in-Chief.
  • 1981 — Adsor­bate induced restruc­tur­ing of sur­face (M.A. van Hore et.al., Surf. Sci., 103, 190, 218 (1981)).
  • 1981 — Intro­duc­tion of con­straint index as a diag­nos­tic test for shape selec­tiv­i­ty using crack­ing rate con­stants for n-hexa­ne and 3-methylpen­tane (V. J. Frilette, W. O. Haag and R. M. Lago, J. Catal., 67, 218 (1981)).
  • 1982 — Def­i­n­i­tion of Ener­gy Pro­file for Ammo­nia Syn­the­sis (G. Ertl in “Sol­id State and Mate­r­i­al Sci.”, CRC Press, 1982, 349).
  • 1982 — The first of a series of sil­i­caa­lu­minophos­phate mol­e­c­u­lar sieves pre­pared by Union Car­bide (now part of UOP).
  • 1982 — The con­cept of tran­si­tion state selec­tiv­i­ty for zeo­lite catal­y­sis intro­duced (W. O. Haag, R. M. Lago and P. B. Weisz, J. Chem. Soc., Farad. Disc., 72, 317 (1982)).
  • 1983 — Ash­land Petro­le­um intro­duces RCC (Reduced Crude Crack­ing) with 40,000 blb/day plant.
  • 1983 — Enichen sci­en­tists report the use of tita­ni­um sil­i­calite (TS-1) as a cat­a­lyst for selec­tive oxi­da­tions with aque­ous hydro­gen per­ox­ide, includ­ing olefin epox­i­da­tion (M. Tara­mas­so, G. Pereyo and B. Natari, U.S. 4,410,501).

 

5th DECADE: 1989 — 1999

  • 1990’s — Fis­ch­er-Trop­sch as a source of alpha-olefins.
  • 1990’s — Com­bi­na­to­r­i­al approach­es to cat­a­lyst screen­ing and new cat­a­lyst dis­cov­ery (e.g., K. D. Shimizu et al., Chem. Eur. J., 4, 1885 (1998)).
  • 1990’s — Selec­tive oxi­da­tion of ben­zene to phe­nol using (Fe) ZSM-5 cat­a­lyst.
  • 1992 — Com­mer­cial use of non-iron cat­a­lyst for ammo­nia syn­the­sis.
  • 1992 — Syn­the­sis of MCM-41, the first uni­form­ly struc­tured meso­porous alu­mi­nosil­i­cate, announced by Mobil Oil (J. S. Beck, et al., JACS, 114, 10834 (1992).
  • 1994 — Top­ics in Catal­y­sis begins pub­li­ca­tion with Gabor Somor­jai and Sir John Thomas as Co-Edi­tors.
  • 1995 — Intro­duc­tion of oxone cat­alyt­ic con­vert­er for air­plane air purifi­ca­tion.
  • 1996 — Cat­alyt­ic con­vert­er select­ed by Fel­lows of the Soci­ety of Auto­mo­tive Engi­neers as one of the top ten achieve­ments in the auto indus­try dur­ing the past 100 years.
  • 1996 — Glob­al Overview of Catal­y­sis — A Series of Reports for many coun­tries begins to appear in Applied Catal­y­sis A: Gen­er­al.
  • 1996 — MagnaCat Process for sep­a­ra­tion and remov­ing aged FCC cat­a­lyst oper­ates at a com­mer­cial scale.
  • 1996 — Mem­bers of orig­i­nal acry­loni­trile research team (l to r; J. L. Calla­han, G. C. Cross, E. C. Mil­berg­er, E. C. Hugh­es and J. D. Idol (F. Veatch, deceased)) at ded­i­ca­tion of plant site as Nation­al His­tor­i­cal Land­mark by the ACS.
  • 1999 — UOP Cyclar Process for the pro­duc­tion of aro­mat­ics for LPG.

 
Con­tributed by Burt Davis
Uni­ver­si­ty of Ken­tucky Cen­ter for Applied Ener­gy Research
2540 Research Park Dri­ve, Lex­ing­ton, KY 40511–8410
For more details and PDF files go to http://crtc.caer.uky.edu/history.htm.