Identification of Active Sites for Methyl Lactate Dehydration on Faujasites

Meeting Program — March 2016

Bingjun Xu
Bingjun Xu
Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing
Uni­ver­si­ty of Delaware

Abstract — The dwin­dling reserve of crude oil and surge in nat­ur­al gas pro­duc­tion is rapid­ly chang­ing the mix of the car­bon source pool for the pro­duc­tion of fuels and chem­i­cal feed­stocks, and in turn cre­at­ing short­ages of sev­er­al key com­mod­i­ty chem­i­cals, e.g., propy­lene and buta­di­ene. The short­age of cer­tain com­mod­i­ty chem­i­cals, such as propy­lene, dri­ves up their prices, which in turn rais­es the cost of the down­stream chem­i­cals, such as acrylic acid. In this regard, lig­no­cel­lu­losic bio­mass derived feed­stocks, e.g., lac­tic acid and its esters, can poten­tial­ly bridge the gap. Cur­rent­ly, the com­mer­cial fer­men­ta­tion process using bio­mass-derived sug­ars can achieve a lac­tic acid (or its esters) yield of up to 90%. The absence of effi­cient and selec­tive cat­a­lyst for lac­tic acid dehy­dra­tion is the main miss­ing link in the pro­duc­tion of renew­able acrylic acid. The pri­ma­ry road­block for the ratio­nal design of cat­a­lysts for lac­tic acid dehy­dra­tion is the lack of the mech­a­nis­tic under­stand­ing of the nature of active sites and mech­a­nis­tic steps lead­ing to the selec­tive removal of the α-hydrox­yl group by dehy­dra­tion. Through kinet­ic and in-situ spec­tro­scop­ic inves­ti­ga­tions, we iden­ti­fy the dehy­dra­tion reac­tion pro­ceeds through dis­so­cia­tive adsorp­tion, acid-medi­at­ed dehy­dra­tion, and asso­cia­tive des­orp­tion steps. These mech­a­nis­tic insights will guide the design of selec­tive cat­a­lysts for this reac­tion.
Biog­ra­phy — Bingjun Xu is cur­rent­ly an Assis­tant Pro­fes­sor in the Depart­ment of Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing at Uni­ver­si­ty of Delaware. Dr. Xu received his Ph.D. in Phys­i­cal Chem­istry, advised by Prof. Friend, from Har­vard Uni­ver­si­ty in 2011. His the­sis estab­lished a mech­a­nis­tic frame­work for oxida­tive cou­pling reac­tions on Au sur­face through sur­face sci­ence stud­ies. Dr. Xu worked with Prof. Davis at Cal­tech on the devel­op­ment of a low tem­per­a­ture, man­ganese oxide based ther­mo­chem­i­cal cycle for water split­ting. Upon fin­ish­ing his post­doc, he joined Uni­ver­si­ty of Delaware in the fall of 2013. The cur­rent research inter­est of the Xu lab spans het­ero­ge­neous catal­y­sis, elec­tro­catal­y­sis and in-situ spec­troscopy.