Supplementary Information for
Catalytic Dehydration of Methyl Lactate: Reaction Mechanism and Selectivity
Control
Brian M. Murphy, Michael P. Letterio, and Bingjun Xu*
Center for Catalytic Science and Technology, Department of Chemical and Biomolecular
Engineering, University of Delaware, 150 Academy Street, Newark DE, 19716
Mears Criterion for External Diffusion (Fogler, p841; Mears, 1971)
If , then external mass transfer effects can be neglected.
= reaction rate, mol/L · s
n = reaction order
R = catalyst particle radius, m
CAb = bulk gas concentration of A, mol/L
kc = mass transfer coefficient, m/s
=[5.99 x 10-3 mol L-1 s-1] × [1 x 10-6 m] × [1] / (2.136 x 10-3 m s-1] × [0.0199
mol/L])=1.41 x 10-4<0.15 {Mears Criterion for External Diffusion}
The reaction order is unknown but any number between 0 and 2 gives a non-transport
limited result. Given that it is a unimolecular reaction, the order is likely close to 1.
Weisz-Prater Criterion for Internal Diffusion (Weisz, Prater, 1954)
If , then internal mass transfer effects can be neglected.
-r’A(obs) = observed reaction rate, mol/L · s
R = catalyst particle radius, m
Deff = effective gas-phase diffusivity, m2/s [Knudsen regime due to small pore radius]
=
where dpore = 7.35 Å
CAs = gas concentration of A at the catalyst surface, mol/L
=[5.99 x 10-3 mol L-1 s-1] × [5 x 10-6 m]2 / ([8.512 x 10-8 m2 s-1] × [00199
mol L-1]) = 3.5 x 10-6 < 1 {Weisz-Prater Criterion for Internal Diffusion}
'Ar
Mears Criterion for External (Interphase) Heat Transfer (Mears, 1971)
E = Activation energy (unknown, but estimated at 10-300 kJ/mol)
-[116.9 kJ/mol × 5.99 × 10-3 mol/L × 1 × 10-6 m × 100 kJ/mol] / [6.98 × 10-7
kJ/m2.K.s × 6032 K2 × 8.314 × 10-3 kJ/mol.K]=
If E = 10 kJ/mol, = |-3.32 × 10-3| < 0.15
If E = 300 kJ/mol, = |-0.010| < 0.15
{Mears Criterion for External (Interphase) Heat Transfer}
References(1) Fogler, H. S. Elements of Chemical Reaction Engineering, 4th Ed. (2005)
15.0)'(
2
gbt
bAr
RThRErH
Figure S1. XRD Spectra of zeolite samples studied in this work.
Figure S2. Activity and selectivity of 30 wt% methyl lactate in H2O at 350 ºC over NaY (50 mg loading)
Figure S3. FTIR spectra of isopropanol on NaY from 200°C to 300°C: (a) 3800 cm-1 – 3000 cm-1, (b) 2000 cm-1 – 1300 cm-1. We see no evidence of a Brønsted acid site (3645 cm-1) or isopropanoate, indicating that ion exchange is not proceeding.th22
Figure S4. In situ FTIR spectra of the Sn-*BEA sample at 200ºC and pyridine adsorbed on the sample at 200ºC from 1600 cm-1 to 1400 cm-1.
Table S1. Product distribution for ML reacted at 330ºC over NaY at 20 m TOS. AA = acrylic acid, MA = methyl acrylate, AD = acetaldehyde, MeOH = methanol, PA = propionic acid, PD = 2,3-pentanedione
Table S2. Activity and selectivity of isopropanol dehydration over NaY and HY(3.6) at 150 ºC. Conversion was limited to < 20% to avoid any transport limitations. Propylene, acetone, and coke were the major products of the reaction, with HY showing significantly higher selectivity to propylene.
Table S3. Acrylic acid conversion over Lewis acidic catalysts and NaY at 330ºC.
Reaction conditions: 30 wt% AA in H2O, 1 mL/hr solution flow rate, 50 mL/min N2 flow.
Scheme S1. General mechanism for the dehydration of methyl lactate over NaY, which outlines the possible hydrolysis pathway of ML via the formation of an ortho ester intermediate.
