Engineering topics
Publications and source records attributed to Dumesic, James A..
Synthetic platform for production of biomass-derived monomers and performance-advantaged polymers with renewability, upgradability, and economic viability.
Catalytic hydrodechlorination is a promising strategy for treating industrial 1,2-dichloroethane wastes, for which Pt and Pt-based alloy catalysts are widely used. Here, we performed a detailed mechanistic study for 1,2-dichloroethane hydrodechlorination on Pt using a synergistic approach combining density functional theory (DFT) calculations, reaction kinetics experiments, and microkinetic modeling. Using planewave DFT calculations, we evaluated the reaction energy and activation energy barrier of each elementary step involved in the reaction network on Pt(111). The calculated energetics were then incorporated into a comprehensive mean-field microkinetic model accounting for a total of 65 elementary steps. The model-predicted reaction rates were compared with the results from our reaction kinetics experiments on SiO2-supported Pt catalysts. Our results indicated that the hydrodechlorination of 1,2-dichloroethane on Pt(111) starts with a H-removal step; then, it proceeds through a sequence of alternating dechlorination and dehydrogenation steps until vinylidene (CH 2 C*) is formed; finally, CH 2 C* is hydrogenated to the final product, ethane, sequentially via vinyl (CH 2 CH*), ethylene, and ethyl (CH 3 CH 2 *) intermediates. After model parameter adjustments, we achieved good agreement between our theoretical model and experimental results; the adjustments to the calculated parameters are consistent with the typically anticipated coverage effects. Furthermore, our study offers valuable mechanistic insights, which are useful for improving catalysts for this chemistry.
In this work, base catalysts were studied for the dehydration of fatty alcohols to linear alpha olefins (LAOs). For the dehydration of 1-octanol to 1-octene, 15%Cs/SiO 2 catalyst was 56% selective at 10% conversion. Diluting a feed of C 8 , C 10 , and C 14 fatty alcohols to 50% in undecane increased the selectivity to alpha olefins to 77-99%. 15%Cs/SiO 2 was further investigated for the dehydration of a 4.2 g/L mixed C 8 -C 14 fatty alcohol in tridecane feed and showed linear alpha olefin selectivities of 78-100% at initial conversions of 51-91% with the conversion lowering to 32-77% over 30 h. Catalytic activity was totally regenerated through calcination. A feed of biologically derived alcohols was produced with E. coli strain CM24 transformed with three plasmids (pBTRCk – pVHb – maACR, pACYC – pVHb – seFadBA, pTRC99A – pVHb – tdTER – fdh) which yielded a 5.5 g/L of C 8 -C 14 fatty alcohol in tridecane. This biologically-derived feed was successfully dehydrated to linear alpha olefins over 15%Cs/SiO 2 at selectivities of 60-100% with initial conversions of 35-75% which decreased to 22-55% over 30 h. Techno-economic analysis (TEA) of the integrated process for fatty alcohol production and subsequent dehydration to alpha olefins was conducted across the potential fermentation TRY (titer, rate, yield) landscape. Baseline fermentation performance resulted in a minimum product selling price (MPSP) double the market price for LAOs due to low titers and high costs associated with managing water and tridecane solvent flows through the system. However, targeted improvements in fermentation performance (e.g., achieving 40 g/L titer, 0.5 g/L/h productivity, 80% theoretical yield) can enable financially viable production of biologically derived LAOs.
5-Hydroxymethyl furfural (HMF) is a platform chemical, which can be derived from lignocellulosic biomass, and used for production of liquid fuels and polymers. We demonstrate a process for production of HMF using sequential enzymatic and catalytic reactions of glucose to synthesize HMF, and simulated-moving-bed (SMB) separation to purify HMF. The adsorption thermodynamic parameters of glucose, fructose, and HMF on a commercial chromatography resin are experimentally determined for modeling the SMB-based HMF production process. The experimental data are used to develop a rigorous process model and then estimate the cost of production. Chromatographic separation of HMF has 16% lower operating costs compared to an extraction-based process and has a minimum selling price of approximately $1478 per ton. We demonstrate that the HMF process can be integrated with the high fructose corn syrup (HFCS) process, and we performed analyses considering two systems including construction of a new integrated facility and retrofitting an existing HFCS facility to produce HMF. Our analyses suggest that the latter approach is a promising short-term low-risk strategy to advance the HMF production technology to commercial scale.
We employed an approach combining reaction kinetics measurements at steady state conditions, electronic structure calculations employing density functional theory, and microkinetic modeling for acetone hydrogenation to provide insights into the effects of water on metal catalyst surfaces for the hydrogenation of oxygenates over a wide range of reaction conditions. Elucidation of the repulsive interactions due to adsorbed water molecules at various reaction conditions provides a basis to formulate rate expressions for heterogeneous catalytic processes of biomass oxygenates. Reaction kinetics experiments were carried out at partial pressures of H 2 , acetone, water and helium in the range of 0.51-0.79, 0.02-0.13, 0.08-0.23, 0-0.28 atm, respectively. We show that the addition of water enhances the hydrogenation rate at 353 K and 1 atm on oxophilic metal catalysts such as Ru/C, whereas the same promotional effect of water is not observed for Pt-based catalysts. Microkinetic model predictions for the hydrogenation of acetone on Ru in the absence and presence of water, using enthalpies and entropies obtained from DFT calculations, were in agreement with the experimentally observed reaction orders and activation barriers. The model shows that a water-assisted hydroxypropyl path is expected to be the favored path on Ru with a rate-determining step of H-OH-mediated hydrogenation of C 3 H 6 OH (i.e., the hydroxypropyl intermediate formed by H 2 O-mediated initial hydrogenation of acetone) to produce isopropyl alcohol (IPA). Furthermore, hydrogen, acetone, hydroxypropyl intermediate and hydroxyl species were predicted to be abundant on the Ru surface with a high coverage of nearly 85%. Lastly, the combined studies of computational and experimental catalysis on hydrogenation reactions help to elucidate the mechanistic role of water on metal catalyzed reactions for producing chemical building blocks from biomass-derived oxygenates.
Thermochemical pretreatment is one of the key steps to process lignocellulosic biomass for production of biofuels and biomaterials. γ-valerolactone (GVL) has been used as a green and renewable solvent to efficiently dissolve lignin under acidic conditions and enhance subsequent enzyme digestibility. Further improvement is still required to lower the pretreatment temperature in order to reduce sugar degradation and irreversible lignin condensation, as well as the capital cost. In this study, we compared the use of HCl and H 2 SO 4 as catalysts during GVL pretreatment, and found the performance of GVL-HCl at 100 °C was comparable to that of GVL-H 2 SO 4 at 120 °C in terms of xylan and lignin removal and enzyme digestibility. We further monitored the lignin removal and cellulose accessibility in the cell walls at different pretreatment time points by imaging the changes in lignin auto-fluorescence and in CtCBM3-GFP binding with confocal laser scanning microscopy (CLSM), respectively. We found GVL-HCl pretreatment at a relative low temperature (100 °C) could rapidly remove lignin in the compound middle lamella and cell corner areas, which concurred with the increase of CtCBM3-GFP binding in these areas. Real-time imaging of cell wall degradation by cellulases further revealed that the secondary cell walls could be digested from both cell lumen and CML sides, and eventually fully deconstructed within 24 h. Furthermore, our results provide new insight into the effects of chloride anions on plant cell wall structure during GVL pretreatment, and offer potential routes to further optimize and enhance the efficiency of GVL-based pretreatment.
Many plastic packaging materials manufactured today are composites made of distinct polymer layers (i.e., multilayer films). Billions of pounds of these multilayer films are produced annually, but manufacturing inefficiencies result in large, corresponding postindustrial waste streams. Although relatively clean (as opposed to municipal wastes) and of near-constant composition, no commercially practiced technologies exist to fully deconstruct postindustrial multilayer film wastes into pure, recyclable polymers. Here, we demonstrate a unique strategy we call solvent-targeted recovery and precipitation (STRAP) to deconstruct multilayer films into their constituent resins using a series of solvent washes that are guided by thermodynamic calculations of polymer solubility. We show that the STRAP process is able to separate three representative polymers (polyethylene, ethylene vinyl alcohol, and polyethylene terephthalate) from a commercially available multilayer film with nearly 100% material efficiency, affording recyclable resins that are cost-competitive with the corresponding virgin materials.
The design of heterogeneous catalysts relies on understanding the fundamental surface kinetics that controls catalyst performance, and microkinetic modeling is a tool that can help the researcher in streamlining the process of catalyst design. Microkinetic modeling is used to identify critical reaction intermediates and rate-determining elementary reactions, thereby providing vital information for designing an improved catalyst. In this review, we summarize general procedures for developing microkinetic models using reaction kinetics parameters obtained from experimental data, theoretical correlations, and quantum chemical calculations. We examine the methods required to ensure the thermodynamic consistency of the microkinetic model. We describe procedures required for parameter adjustments to account for the heterogeneity of the catalyst and the inherent errors in parameter estimation. We discuss the analysis of microkinetic models to determine the rate determining reactions using the degree of rate control and reversibility of each elementary reaction. We introduce incorporation of Brønsted–Evans–Polanyi relations and scaling relations in microkinetic models and the effects of these relations on catalytic performance and formation of volcano curves. We review the analysis of reaction schemes in terms of the maximum rate of elementary reactions, and we outline a procedure to identify kinetically significant transition states and adsorbed intermediates. Here, we explore the application of generalized rate expressions for the prediction of optimal binding energies of important surface intermediates and to estimate the extent of potential rate improvement. We also explore the application of microkinetic modeling in homogeneous catalysis, electro-catalysis, and transient reaction kinetics. We conclude by highlighting the challenges and opportunities in the application of microkinetic modeling for catalyst design.
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Biomass conversion to alcohols using supercritical methanol depolymerization and hydrodeoxygenation (SCM-DHO) with CuMgAl mixed metal oxide is a promising process for biofuel production. Here, we demonstrate how maple wood can be converted at high weight loadings and product concentrations in a batch and a semi-continuous reactor to a mixture of C 2 –C 10 linear and cyclic alcohols. Maple wood was solubilized semi-continuously in supercritical methanol and then converted to a mixture of C 2 –C 9 alcohols and aromatics over a packed bed of CuMgAlO x catalyst. Up to 95 wt% of maple wood can be solubilized in the methanol by using four temperature holds at 190, 230, 300, and 330 °C. Lignin was solubilized at 190 and 230 °C to a mixture of monomers, dimers, and trimers while hemicellulose and cellulose solubilized at 300 and 330 °C to a mixture of oligomeric sugars and liquefaction products. The hemicellulose, cellulose, and lignin were converted to C 2 –C 10 alcohol fuel precursors over a packed bed of CuMgAlO x catalyst with 70–80% carbon yield of the entire maple wood. The methanol reforming activity of the catalyst decreased by 25% over four beds of biomass, which corresponds to 5 turnovers for the catalyst, but was regenerable after calcination and reduction. In batch reactions, maple wood was converted at 10 wt% in methanol with 93% carbon yield to liquid products. The product concentration can be increased to 20 wt% by partially replacing the methanol with liquid products. The yield of alcohols in the semi-continuous reactor was approximately 30% lower than in batch reactions likely due to degradation of lignin and cellulose during solubilization. These results show that solubilization of whole biomass can be separated from catalytic conversion of the intermediates while still achieving a high yield of products. However, close contact of the catalyst and the biomass during solubilization is critical to achieve the highest yields and concentration of products.
Here, a molecular understanding of the conversion of biorenewable threo- and erythro-levoglucosanol (LGOL) to 3,4-dideoxysugars in aqueous medium is provided based on first-principles simulations. The synthetic importance of this transformation is that these intermediates can be quantitatively hydrogenated to (S,S)/(S,R) hexane-1,2,5,6-tetrol (tetrol), whose stereochemistry depends on which dideoxy sugar intermediates are formed during LGOL conversion. The thermodynamic and kinetic feasibility of the acetal (R 2 C(OR) 2 ) hydrolysis in LGOL is investigated via computing the free energy profile. In aqueous medium, the rate-determining step of LGOL hydrolysis is the protonation of the anhydro-bridge oxygen atom of LGOL concurrent with ring opening, yielding the cyclic forms of 3,4-dideoxymannose (DDM) and 3,4-dideoxyglucose (DDG) from threo- and erythro-LGOL, respectively. The measured activation energies of LGOL hydrolysis are 20.5 and 23.6 kcal/mol for DDM and DDG formation, respectively. These values are in agreement with the computed protonation free energies of 17.1 and 18.2 kcal/mol, respectively. Based on the simulations, a Bronsted base-catalyzed isomerization from DDG or DDM to 3,4-dideoxy fructose (DDF) is preferred with lower apparent activation free energy barriers compared to the acid-catalyzed isomerization. In summary, this study provides mechanistic information about the conversion of the biomass-derived anhydro-sugar LGOL to 3,4-dideoxy sugars, which are precursors to renewable high-value chemicals.
A method to produce 5-hydroxymethylfurfural (HMF) from C6 carbohydrates. The method includes the steps of reacting a reactant comprising at least one C6 carbohydrate, in a reaction mixture comprising at least about 5% (v/v) water, a polar, aprotic solvent, and an acid, for a time, at a temperature, and at a hydrogen ion concentration wherein at least a portion of the C6 carbohydrate present in the reactant is converted to 5-hydroxymethyl furfural (“HMF”).
Abstract not provided
Catalytic strategies were developed to synthesize and release chemicals for applications in fine chemicals, such as drugs and polymers, from a biomass-derived chemical, 5-hydroxymethyl furfural (HMF). The combination of the diene and aldehyde functionalities in HMF enabled catalytic production of acetalized HMF derivatives with diol or epoxy reactants to allow reversible synthesis of norcantharimide derivatives upon Diels-Alder reaction with maleimides. Reverse-conversion of the acetal group to an aldehyde yielded mismatches of the molecular orbitals in norcantharimides to trigger retro Diels-Alder reaction at ambient temperatures and released reactants from the coupled molecules under acidic conditions. In conclusion, these strategies provide for the facile synthesis and controlled release of high-value chemicals.
We illustrate a process to produce a versatile platform chemical from biomass-derived fructose for organic dye, polymer, and liquid fuel industries. An aldol-condensed chemical (HAH) is synthesized as a platform chemical from fructose by catalytic reactions in acetone/water solvent with non-noble metal catalysts (e.g., HCl, NaOH). Then, selective reactions (e.g., etherification, reduction, dimerization) of the functional groups, such as enone and hydroxyl groups, in the HAH molecule enable applications in organic dyes and polyether precursors. High yields of target products, such as 5-(hydroxymethyl) furfural (HMF) (85.9% from fructose) and HAH (86.3% from HMF) are achieved by sequential dehydration and aldol-condensation with a simple purification process (>99% HAH purity). The use of non-noble metal catalysts, the high yield of each reaction, and the simple purification of the target product allow for beneficial economics of the process. Techno-economic analysis indicates that the process produces HAH at minimum selling price (MSP) of $1958 per ton. The MSP of HAH product allows the economic viability of applications in organic dye and polyether markets by replacing its counterparts, such as anthraquinone ($3200-$3900 per ton) and bisphenol-A ($1360-$1720 per ton).
Nanoscale coatings of AlO x were deposited onto SiO 2 using atomic layer deposition (ALD) to synthesize amorphous silica-alumina (SiAl) catalysts, and these catalysts were investigated for levoglucosanol (Lgol) hydrogenolysis. With decreasing Al 2 O 3 loading, the ratio of Brønsted to Lewis acid sites, measured by NH 3 -TPD and pyridine-FTIR, systematically increases, while the Al coordination, measured by solid state 27 Al NMR, decreases. These structural changes correspond to an increasing mass-normalized rate of Lgol hydrogenolysis. We model the mass-normalized reaction rate as the sum of independent contributions from Brønsted and Lewis sites, showing that Brønsted acid sites on ALD-AlO x /SiO 2 catalysts have a 6-times higher turnover frequency (TOF) than Lewis acid sites on these catalysts. Additionally, Lewis acid sites on ALD-AlO x /SiO 2 catalysts (potentially related to Al(V) species) have a 4-times higher TOF than Lewis acid sites on bulk γ-Al 2 O 3 . The overall mass-normalized reactivity of ALD-AlO x /SiO 2 catalysts is due to Lewis acid sites at the highest Al 2 O 3 loading, while it is predominantly due to Brønsted acid sites at the lowest Al 2 O 3 loadings. In conclusion, this work provides a new approach to synthesize amorphous SiAls with tunable Brønsted/Lewis acid site ratio and reveals differences in the reactivity of Brønsted and Lewis acid sites on these materials.