John Sinfelt: Removal of lead from gasoline with bimetallics

John Sinfelt

John Sin­felt

Use of lead alkyls, pri­mar­ily in the form of tetraethyl­lead, to enhance the octane num­ber and per­for­mance of U.S. motor gaso­lines nearly dou­bled from 235,000 tons in 1955 to 445,000 in 1975. As the harm­ful health effects of tailpipe-exhausted lead com­pounds became increas­ingly appar­ent, leg­isla­tive ini­tia­tives, begin­ning in 1975, man­dated the com­plete removal of lead addi­tives from U.S. motor fuels by year-end 1991. Dr. Sinfelt’s research on alter­nate petro­leum con­ver­sion chemistries allowed refin­ers to remove lead alkyls from gaso­line years before the man­dated dead­line. Appli­ca­tion of novel, highly active and selec­tive bimetal­lic clus­ter cat­a­lyst sys­tems he invented and cham­pi­oned made it pos­si­ble to pro­duce high-octane motor gaso­line with­out the use of lead additives.

Dr. Sinfelt’s dis­tinc­tive research method­ol­ogy empha­sized entirely new con­cepts in the under­stand­ing and use of cat­a­lyst mate­ri­als con­tain­ing bimetal­lic clus­ters. Ear­lier work on metal alloys empha­sized the rela­tion between cat­alytic per­for­mance of a metal and its elec­tron band struc­ture. How­ever, lit­tle atten­tion had been paid to the pos­si­bil­ity of cat­alyt­i­cally influ­enc­ing the selec­tiv­ity of chem­i­cal trans­for­ma­tions (prod­uct selec­tiv­i­ties). One of Dr. Sinfelt’s most impor­tant dis­cov­er­ies, achieved through in-depth stud­ies on bimetal­lic cat­a­lysts, con­cerns con­trol of chem­i­cal reac­tion selec­tiv­ity. He dis­cov­ered that it is, in fact, pos­si­ble to cat­alyze one type of chem­i­cal reac­tion in pref­er­ence to other reac­tions that are them­selves ther­mo­dy­nam­i­cally favor­able. He clearly showed that bimetal­lic cat­a­lysts could be tai­lored to effec­tively reduce unde­sir­able com­pet­ing reac­tions, and thus con­trol the kinetic speci­ficity of sur­face reac­tions. This made pos­si­ble the eco­nom­i­cal con­ver­sion of low octane num­ber mol­e­cules to ones with high octane num­bers. The pub­lic ben­e­fited greatly from the envi­ron­men­tal improve­ments due to lead-free gaso­line, and motorists did not pay a hugh price for it.

While Dr. Sinfelt’s research has made far-reaching con­tri­bu­tions to our under­stand­ing of hydro­car­bon con­ver­sion processes, the prac­ti­cal ben­e­fits of his research are equally pro­found. The appli­ca­tion of bimetal­lic cat­a­lysts in petro­leum refin­ing was cru­cial to mak­ing high-octane “lead-free” motor fuels widely avail­able. Today, bimetal­lic cat­a­lysts have replaced tra­di­tional cat­a­lysts in cat­alytic reform­ing (the major com­mer­cial process used in increas­ing the octane rat­ing of motor fuels) allow­ing thereby elim­i­na­tion of lead-based, octane improv­ing addi­tives. Dr. Sin­felt is the inven­tor both of a Pt-Ir cat­a­lyst that has been widely used in cat­alytic reform­ing and of a staged reform­ing process that has also found wide appli­ca­tion. The lat­ter uses two dif­fer­ent bimetal­lic cat­a­lysts in sep­a­rate reac­tors to opti­mize per­for­mance. The clas­sic work of Sin­felt on the kinet­ics of cat­alytic reform­ing reac­tions in the late 1950’s and early 1960’s pro­vided the foun­da­tion for these impor­tant indus­trial advances.

In addi­tion to elim­i­nat­ing the haz­ard of lead in gaso­line, Sinfelt’s work enabled the devel­op­ment and appli­ca­tion of multi-metallic cat­a­lysts for the exhaust sys­tems of auto­mo­biles to decrease the emis­sion of pol­lu­tants such as car­bon monox­ide, unburned hydro­car­bons and nitro­gen oxides. The cat­a­lysts com­monly used today con­tain a com­bi­na­tion of met­als; i.e., they are bi-metallic or tri-metallic. These cat­a­lysts, like reform­ing cat­a­lysts, per­form bet­ter when more than one metal­lic ele­ment is present. Cur­rent exhaust cat­a­lyst sys­tems are based on Sinfelt’s ground break­ing dis­cov­er­ies. Finally, since these cat­a­lysts are poi­soned by lead, its removal from gaso­line made the appli­ca­tion of auto exhaust cat­a­lysts tech­ni­cally feasible.

The basic stud­ies of Dr. Sin­felt on bimetal­lic cat­a­lysts gen­er­ated much inter­est in the field and called atten­tion to their impor­tance for cat­alytic reform­ing and for the pro­duc­tion of lead-free gaso­line. The dis­cov­ery was first reported in two U. S. Patents to Sin­felt et al. (3,442,973, which issued in 1969 and 3,617,518, which issued in 1971) and in two papers in the Jour­nal of Catal­y­sis 24, 283 (1972) and 29, 308 (1973). These early pub­li­ca­tions stim­u­lated much inter­est in bimetal­lic cat­a­lysts as a major area of research that is still flour­ish­ing. For these con­tri­bu­tions to the lead phase-down in the United States, Dr. Sin­felt was awarded the National Medal of Sci­ence by the Pres­i­dent of the United States in 1979 and the pres­ti­gious Perkin Medal in 1984. His is among the most impor­tant con­tri­bu­tions enabling the world­wide reduc­tion of envi­ron­men­tal lead and the elim­i­na­tion of the asso­ci­ated risks to human health.

In a trib­ute to John Sin­felt in I&EC, 42 (2003) 1537, Pro­fes­sor Michel Boudart com­ments, “His impact has been uniquely impor­tant because John com­bined the inven­tive­ness required for sci­en­tific dis­cov­ery with the abil­ity to engi­neer his work to many suc­cess­ful appli­ca­tions in indus­try. John suc­ceeded though repeated sci­en­tific dis­cov­er­ies and engi­neer­ing appli­ca­tions, with­out ever preach­ing … John man­aged to become a role model to those who prac­tice cat­alytic sci­ence, not only in the secre­tive indus­trial envi­ron­ment but also in uni­ver­si­ties world­wide … The legacy of John Sin­felt is his unshak­able belief in chem­i­cal kinet­ics to advance cat­alytic sci­ence and engi­neer­ing. John’s impact on the field exceeds by much the impact of his own sci­en­tific and engi­neer­ing con­tri­bu­tions.“
 
Con­tributed by Gary McVicker and John Armor