Raul F. Lobo

Porous silica via colloidal crystallization

Microstructured porous silicas have potential applications in catalysis, separations, coatings, microelectronics and electro-optics, but methods for producing materials with uniform submicrometre pores have not been available. We have now developed a method in which modified colloidal crystals are used as templates for silica polymerization. This method yields products with highly uniform and structured pores of tuneable size in the submicrometre region.

Metalloenzyme-like catalyzed isomerizations of sugars by Lewis acid zeolites

Isomerization of sugars is used in a variety of industrially relevant processes and in glycolysis. Here, we show that hydrophobic zeolite beta with framework tin or titanium Lewis acid centers isomerizes sugars, e.g., glucose, via reaction pathways that are analogous to those of metalloenzymes. Specifically, experimental and theoretical investigations reveal that glucose partitions into the zeolite in the pyranose form, ring opens to the acyclic form in the presence of the Lewis acid center, isomerizes into the acyclic form of fructose, and finally ring closes to yield the furanose product. The zeolite catalysts provide processing advantages over metalloenzymes such as an ability to work at higher temperatures and in acidic conditions that allow for the isomerization reaction to be coupled with other important conversions.

Unconventional, highly selective CO2 adsorption in zeolite SSZ-13.

Low-pressure adsorption of carbon dioxide and nitrogen was studied in both acidic and copper-exchanged forms of SSZ-13, a zeolite containing an 8-ring window. Under ideal conditions for industrial separations of CO(2) from N(2), the ideal adsorbed solution theory selectivity is >70 in each compound. For low gas coverage, the isosteric heat of adsorption for CO(2) was found to be 33.1 and 34.0 kJ/mol for Cu- and H-SSZ-13, respectively. From in situ neutron powder diffraction measurements, we ascribe the CO(2) over N(2) selectivity to differences in binding sites for the two gases, where the primary CO(2) binding site is located in the center of the 8-membered-ring pore window. This CO(2) binding mode, which has important implications for use of zeolites in separations, has not been observed before and is rationalized and discussed relative to the high selectivity for CO(2) over N(2) in SSZ-13 and other zeolites containing 8-ring windows.

Production of renewable jet fuel range alkanes and commodity chemicals from integrated catalytic processing of biomass

This article presents results from experimental studies and techno-economic analysis of a catalytic process for the conversion of whole biomass into drop-in aviation fuels with maximal carbon yields. The combined research areas highlighted include biomass pretreatment, carbohydrate hydrolysis and dehydration, and catalytic upgrading of platform chemicals. The technology centers on first producing furfural and levulinic acid from five- and six-carbon sugars present in hardwoods and subsequently upgrading these two platforms into a mixture of branched, linear, and cyclic alkanes of molecular weight ranges appropriate for use in the aviation sector. Maximum selectivities observed in laboratory studies suggest that, with efficient interstage separations and product recovery, hemicellulose sugars can be incorporated into aviation fuels at roughly 80% carbon yield, while carbon yields to aviation fuels from cellulose-based sugars are on the order of 50%. The use of lignocellulose-derived feedstocks rather than commercially sourced model compounds in process integration provided important insights into the effects of impurity carryover and additionally highlights the need for stable catalytic materials for aqueous phase processing, efficient interstage separations, and intensified processing strategies. In its current state, the proposed technology is expected to deliver jet fuel-range liquid hydrocarbons for a minimum selling price of

SSZ-26 and SSZ-33: Two molecular sieves with intersecting 10- and 12-ring pores

4.75 per gallon assuming nth commercial plant that produces 38 million gallons liquid fuels per year with a net present value of the 20 year biorefinery set to zero. Future improvements in this technology, including replacing precious metal catalysts by base metal catalysts and improving the recyclability of water streams, can reduce this cost to

Characterization and catalytic properties of MCM-56 and MCM-22 zeolites

2.88 per gallon.

The Role of Ru and RuO2 in the Catalytic Transfer Hydrogenation of 5-Hydroxymethylfurfural for the Production of 2,5-Dimethylfuran

The framework structures of two closely related molecular sieves, SSZ-26 and SSZ-33, are described. These materials possess a previously missing but desired structural feature in a group of industrially significant zeolites. They contain a three-dimensional pore system that provides access to the crystal interior through both 10- and 12-rings. This property is a consequence of the organic structure—directing agents used in the synthesis of these materials. These materials are examples of the purposeful design of a micropore architecture. Both SSZ-26 and SSZ-33 contain the 4=4–1 building unit that had been previously found only in natural zeolites.

Bimetallic effects in the hydrodeoxygenation of meta-cresol on γ-Al2O3 supported Pt–Ni and Pt–Co catalysts

Abstract We present an investigation of the structure and properties of MCM-56 and MCM-22. These materials have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N2 adsorption isotherms. DIFFaX was used to simulate pronounced peak broadening in the X-ray diffraction patterns of MCM-56. Toluene disproportionation is used as a test reaction to compare the catalytic activity of MCM-22 and MCM-56. We have found that MCM-56 is made of very thin MWW-type layers. The layers are typically one unit cell along the c direction (with a few of them having two or three unit cells). These very thin layers of MCM-56 become tightly curled upon calcination. The structures thus formed pack very efficiently, and this phenomenon prevents access of organic molecules like toluene to most of the 12 MR cups on the crystal exterior. Although MCM-56 is active for the disproportionation of toluene, its activity is lower than that of MCM-22. A calcination procedure that prevents the curling up of the MCM-56 layers is needed to make MCM-56 a useful catalyst for large organic molecules.

Comparison of Homogeneous and Heterogeneous Catalysts for Glucose‐to‐Fructose Isomerization in Aqueous Media

We have previously shown that 2,5‐dimethylfuran (DMF) can be produced selectively from 5‐hydroxymethylfurfural in up to 80 % yield via catalytic transfer hydrogenation with 2‐propanol as a hydrogen donor and Ru/C as a catalyst. Herein, we investigate the active phase of the Ru/C catalyst by using extended X‐ray absorption fine structure, X‐ray photoelectron spectroscopy, and high‐resolution TEM analyses. The results reveal that RuO2 is the dominant phase in the fresh (active) catalyst and is reduced to metallic Ru during the reaction with the hydrogen produced in situ from 2‐propanol. The deactivation of the catalyst is correlated with the reduction of the surface of RuO2. Reactivity studies of individual phases (bulk RuO2 and reduced Ru/C catalysts) indicate that RuO2 mainly catalyzes the Meerwein–Ponndorf–Verley reaction of 5‐hydroxymethylfurfural that produces 2,5‐bis(hydroxymethyl)furan and the etherification of 2,5‐bis(hydroxymethyl)furan or other intermediates with 2‐propanol and that the reduced Ru/C catalyst has moderate hydrogenolysis activity for the production of DMF (30 % selectivity) and other intermediates (20 %). In contrast, a physical mixture of the two phases increases the DMF selectivity up to 70 %, which suggests that both metallic Ru and RuO2 are active phases for the selective production of DMF. The oxidation of the reduced Ru/C catalyst at different temperatures and the in situ hydrogen titration of the oxidized Ru/C catalysts were performed to quantify the bifunctional role of Ru and RuO2 phases. The mild oxidation treatment of the Ru/C catalyst at 403 K could activate the catalyst for the selective production of DMF in up to 72 % yield by generating a partially oxidized Ru catalyst.

Carbon Dioxide and Nitrogen Adsorption on Cation-Exchanged SSZ-13 Zeolites

The hydrodeoxygenation (HDO) of meta-cresol, a typical phenolic compound in bio-oils, is investigated in the vapor-phase on γ-Al2O3-supported Pt catalysts at near atmospheric hydrogen pressure. The HDO reaction yields two major hydrocarbons: toluene and methylcyclohexane. The deoxygenation of meta-cresol proceeds through two consecutive steps: hydrogenation of the aromatic ring on the Pt metal followed by dehydration reactions of the produced alcohol intermediates on the alumina support. Phenolic ring saturation is proposed to be slower than its sequential dehydration steps on Pt/γ-Al2O3. This is in a good agreement with the higher selectivity of toluene compared to that of the hydrogenated cyclic hydrocarbon, methylcyclohexane, because toluene formation requires fewer ring hydrogenation steps than its counterpart. The additions of Co and Ni into Pt not only improve the overall HDO conversion, but also modify the product distribution. The enhancement in the overall HDO activity is related to the better hydrogenation activity of bimetallic Pt–Co and Pt–Ni catalysts and the generation of additional sites for alcohol dehydration. Consequently, more saturated cyclic hydrocarbon product, methylcyclohexane, is observed on bimetallic catalysts with respect to the monometallic Pt catalyst.