Hydroxyalkylation/alkylation Research Articles

Samarium-doped cobalt metal–organic framework as a versatile catalyst for the conversion of furfural and 2-methylfuran to high-value-added biofuel precursors

Fabrication of a samarium-doped cobalt metal–organic framework (Sm/Co-TTA MOF) for catalysing the conversion of furfural and 2-methylfuran to a biofuel precursor 5,5′-(furan-2-ylmethylene)bis(2-methylfuran) (FMBMF) via hydroxyalkylation-alkylation (HAA).

Solventless autothermic production of energy-intensive furanic biofuels expedited by photothermal effect

Driving C-C coupling reactions to produce biofuels is usually energy-consuming and requires well-tailored catalysts. Herein, a novel photothermal catalytic strategy was developed to be highly efficient for cascade hydroxyalkylation-alkylation (HAA) of various biomass-derived aldehydes/ketones with 2-methylfuran or acetalization of different bioalcohols with furfural to exclusively afford furanic biofuel molecules (up to 94.8 % yield). The developed bio-based SO3H-functionalized graphene-like catalyst (GLB-SO3H-700) could complete the HAA and acetalization reactions in 10 min under solvent-free and room-temperature conditions. Infrared thermal imaging revealed that the local photothermal effect of interfacial solar heating could in-situ remove water co-product, thereby improving the reaction selectivity and rate as evidenced by kinetic study. Moreover, the GLB-SO3H-700 catalyst exhibited good stability and recyclability. The developed SO3H-functionalized graphene-like photothermal materials hold great potential for catalytic upgrading of biomass into high-quality biofuels under mild conditions.

MOF-catalyzed hydroxyalkylation-alkylation reaction for the controlled synthesis of furan oligomers

Hydroxyalkylation-alkylation (HAA) reaction is a type of C-C coupling technique utilized in the production of furan oligomers, which are potential biofuel precursors. In this study, we present the first application of an acidic MOF, Sulfated MOF-808, in catalyzing the HAA reactions of a series of furan oligomers with high yield and selectivity. Specifically, we focused on the optimization of the HAA between 5-methylfurfural (5-MFUR) and 2-methylfuran (2-MF) by varying different reaction conditions, which afforded a quantitative yield reaching 97% while preventing the self-condensation of 2-MF. The catalyst was also found to be recyclable and can be reused without significant loss in its activity. Lastly, we extended the substrate scope to include benzene-based electrophiles, thereby further proving the versatility of the Sulfated MOF-808 catalyst in the HAA reactions of a variety of starting materials.

Production of a high molecular weight jet-fuel precursor from biomass derived furfural and 2-methylfuran using propyl sulfonic SBA-15 catalysts

An effective catalyst for the production of branched chain fuel precursors with 15 carbon atoms (C15) from low carbon number, biomass-derived molecules is reported in this work. It shows that SBA-15 silica with the incorporation of sulfonic groups (S15) is highly active and selective for C-C coupling at low temperature, without solvent and under simple reaction conditions, giving a C15 condensation product with high selectivity, greater than 95 %, via hydroxyalkylation/alkylation (HAA) of 2-methylfuran (2-MF) with furfural (FAL). As water was determined to have a great negative influence on the stability of these catalysts, synthesis modifications and various post-synthesis treatments were tested to improve yield of C15. As a result, it was possible to improve up to 12 % the efficiency of the reaction by incorporating hydrophobic groups in the synthesis of sulfonic SBA-15 by co-condensation. This catalyst can be recovered and recycled, preserving its stability over multiple reaction cycles.

Synthesis of renewable diesel and jet fuels from bio-based furanics via hydroxyalkylation/alkylation (HAA) over SO42-/TiO2 and hydrodeoxygenation (HDO) reactions

Upgrading biomass to renewable diesel and jet fuels is essential to achieve carbon neutrality. Herein, diesel and jet fuels range alkanes were produced by HAA of 2-methylfuran and furfural over solid acid SO42-/TiO2 and subsequent HDO over Pd/NbOPO4. A series of SO42-/TiO2 catalysts were synthesized by wetness impregnation to produce C15 fuel precursors. S/Ti-450 with a calcination temperature of 450 °C exhibited the highest activity, affording 97.9 % yield of C15 fuel precursor. Sufficient Brønsted acid sites and moderate Brønsted acid strength are responsible for the super catalytic performance of S/Ti-450. Stability studies demonstrated that S/Ti-450 could be regenerated. Furthermore, the application of S/Ti-450 in the HAA reaction was extended to other carbonyl compounds (e.g., butanal, cyclohexanone and acetone) and high yields of desired fuel precursors were obtained. Finally, C15 fuel precursor was further converted to long-chain alkanes via HDO over Pd/NbOPO4, yielding 85.0 % diesel and jet fuels range alkanes.

Nanoarchitectonics of niobium (V) oxide with grafted sulfonic acid groups for solventless conversion of biomass derivatives to high carbon biofuel precursors

We report the development of sulfonic acid functionalized niobium pentoxide (Nb2O5) for the synthesis of high dense carbon biofuel precursors from low dense biomass derivatives. Specifically, we have used a Lewis acid catalyst in the form of niobium pentoxide and combination of Lewis and Brønsted acid catalysts in the form of sulfonic acid functionalized catalyst (S-Nb2O5). The structural modification of Nb2O5 after treatment with different amounts of sulfuric acid has been discussed with the help of various techniques. Both Nb2O5 and S-Nb2O5 have been used for the solventless hydroxyalkylation-alkylation (HAA) reaction between 2-methylfuran and furfural (biomass derivatives) to form C-15 product, which can be used as a precursor for the synthesis of biofuels. Variation in the amount of sulfonic group functionalization on the surface of Nb2O5 was performed and it turns out that S3-Nb2O5 having 5.87% atomic percent of S shows the best catalytic activity with a maximum yield of 87% for C-15 product at relatively low temperature (50 °C) under neat conditions. Green metrics calculations have been performed to compare the sustainability and greenness of the reaction with various other catalysts. This work is expected to pave way for the development of acid functionalized metal oxide-based catalysts for biomass conversion reactions aimed towards bioenergy.

Rapid Synthesis of Diesel Precursors from Biomass-Derived Furanics Over Aluminum-Doped Mesoporous Silica Sphere Catalysts.

The condensation of biomass-derived molecules has been increasingly utilized as a sustainable strategy for the preparation of high-carbon precursors for high-density fuels, thus stimulating the demand for more efficient catalysts. This study concerns the synthesis of an aluminum-doped mesoporous silica sphere (Al-MSS) catalyst for the conversion of biobased furfural and 2-methylfuran into a C15 diesel precursor through a hydroxyalkylation/alkylation (HAA) reaction. A series of Al-MSS catalysts with different Si/Al ratios and calcination temperatures is prepared and extensively characterized, among which Al-MSS20-450 (Si/Al=20 : 1, calcined at 450 °C) exhibits unprecedentedly high reaction efficiency in catalyzing HAA reaction, offering a 94 % product yield at 140 °C in 20 min. The catalyst also gives high product yields across a broad temperature range from 80 °C to 140 °C with varied reaction time. Reaction kinetics reveal that both competitive substrate adsorption and temperature-dependent system viscosity affect the reaction efficiencies. Correlations between the catalytic activity and surface acid sites disclose that moderate and strong acid sites are primarily responsible for catalysis. Brønsted and Lewis acid sites are found by poisoning assays to work synergistically to catalyze the reaction, with the former being the primary sites. Finally, the catalyst displays good recycling performance, which further highlights its potential for industrial application.

Production of green jet fuel from furanics via hydroxyalkylation-alkylation over mesoporous MoO3-ZrO2 and hydrodeoxygenation over Co/γ-Al2O3: Role of calcination temperature and MoO3 content in MoO3-ZrO2

Green biofuels are equivalent to hydrocarbon-based motor fuels and compatible with existing refinery infrastructures and combustion engines. Therefore, sustainable production of green biofuels is essential to circumvent the construction of expensive biorefinery infrastructures. This study thus presents the production of green jet fuel from biomass-derived furanic compounds via hydroxyalkylation-alkylation (HAA) reaction coupled with hydrodeoxygenation (HDO) of the C15 biofuel precursor. MoO3-promoted ZrO2 is a promising solid acid catalyst with excellent thermal stability. The HAA reaction of 2-methylfuran with furfural was thus investigated over a novel MoO3-promoted mesoporous ZrO2 catalyst. This work elucidated the role of calcination temperature and MoO3 loading on the structural variation of MoO3-promoted mesoporous ZrO2 and the evolution of acid sites. The highest acid density and consequently best catalytic performance was observed at 873 K calcination temperature with 20 wt% MoO3 loading. About 85 % 2-methylfuran conversion was achieved over 1.25 g of this optimum catalyst at 2:1 2-methylfuran/furfural mole ratio, 323 K, and 5 h. The HAA reaction was further investigated at various reaction temperatures, catalyst loadings, and 2-methylfuran/furfural mole ratios to obtain optimum reaction conditions. HDO of biofuel precursor was examined over Co/γ-Al2O3 catalyst at various reaction temperatures, initial hydrogen pressure, and Co metal loading on γ-Al2O3 to understand the reaction mechanism and identify the optimum reaction conditions. HDO of biofuel precursor progressed through successive furan ring saturation and opening reactions, followed by a combination of HDO, decarbonylation, and cleavage of tertiary-carbon bonds. C9-C15 alkanes were observed as products, with C11 and C14 hydrocarbons being dominant at 573 K and 30 bar. The elevated hydrogen pressure and reaction temperature boosted the conversion of oxygen-containing intermediate compounds at the cost of CC cracking reactions. The conversion of oxygen-containing intermediate compounds was enhanced with rising Co metal loading on γ-Al2O3 up to 20 wt% due to the enhancement of metal dispersion.

Highly dispersed NbOPO4/SBA-15 as a versatile acid catalyst upon production of renewable jet-fuel from bio-based furanics via hydroxyalkylation-alkylation (HAA) and hydrodeoxygenation (HDO) reactions

Herein, we report the synthesis of a highly active and mesoporous Brønsted acidic NbOPO4/SBA-15 catalyst. The prepared catalysts were thoroughly characterized by means of analytical techniques such as XRD, FT-IR, XPS, NH3-TPD, SEM-EDS, TEM, TGA, 31P-MAS-NMR and N2-physisorption. The H3PO4 free deposition method was found to be effective for preserving the structure of Silica based carrier. In terms of catalytic performance, these materials demonstrated high activity upon C-C coupling of 2-methyl furan with carbonyl compounds and outperforming bulk NbOPO4, Nb2O5/SBA-15 and traditional solid acid catalysts (Al-MCM-41, Si/Al and H-ZSM-5). The NbOPO4/SBA-15 catalysts were stable and maintained high activity upon reuse and continuous operation (∼65 h). Furthermore, the Pd loaded counterparts (Pd/NbOPO4/SBA-15 and Pd/Nb2O5/SBA-15) also functioned as bifunctional catalysts and exhibited excellent activity upon subsequent hydrodeoxygenation of C-C coupling products. Most importantly, in terms of jet-fuel range hydrocarbons selectivity, these catalysts outperformed monofunctional Pd/carbon and aluminosilicate based bifunctional catalysts.

Catalytic One-Pot Conversion of Renewable Platform Chemicals to Hydrocarbon and Ether Biofuels through Tandem Hf(OTf)4 +Pd/C Catalysis.

Efficient conversion of renewable biomass platform chemicals into high-quality fuels remains challenging. A one-pot catalytic approach has been developed to synthesize various structurally defined biofuels by using Hf(OTf)4 and Pd/C for selective tandem catalysis and 2-methylfuran (2-MF) as a renewable feedstock. 2-MF first undergoes Lewis acid-catalyzed hydroxyalkylation/alkylation (HAA) condensation with carbonyl compounds to afford intermediates containing the targeted carbon skeletons of hydrocarbon or ether products, and these intermediates then undergo hydrogenation or hydrodeoxygenation to afford the target products, catalyzed by metal triflate+Pd/C in the same pot. The present process can produce structurally defined alkanes and cyclic ethers under mild conditions.

Renewable lubricants with tailored molecular architecture.

We present a strategy to synthesize three types of renewable lubricant base oils with up to 90% yield using 2-alkylfurans, derived from nonfood biomass, and aldehydes, produced from natural oils or biomass through three chemistries: hydroxyalkylation/alkylation (HAA), HAA followed by hydrogenation, and HAA followed by hydrodeoxygenation. These molecules consist of (i) furan rings, (ii) saturated furan rings, and (iii) deoxygenated branched alkanes. The structures of these molecules can be tailored in terms of carbon number, branching length, distance between branches, and functional groups. The site-specific, energy-efficient C-C coupling chemistry in oxygenated biomass compounds, unmatched in current refineries, provides tailored structure and tunable properties. Molecular simulation demonstrates the ability to predict properties in agreement with experiments, proving the potential for molecular design.

A New Lewis Acidic Zr Catalyst for the Synthesis of Furanic Diesel Precursor from Biomass Derived Furfural and 2-Methylfuran

Herein, we reported the first time to use Lewis type acidic Zr/SBA-15 catalyst for the hydroxyalkylation/alkylation (HAA) reaction of biomass derived furfural and 2-methylfuran (2-MF) to produce diesel precursors. Characterizations such as XRD, XPS, SEM and TEM, were used to provide detailed structure features of mesoporous catalysts of varied Si/Zr ratios. Among the catalysts, Zr/SBA-15(20) (Si/Zr ratio(mol:mol) = 20:1) possessed the highest catalytic activity in the HAA reaction, providing 93.9% yield of the target product at 140 °C under neat condition. Lewis acid was revealed as the dominant active sites for the HAA reaction. Reaction parameters including reaction temperature, catalyst loading and furfural/2-MF ratio were investigated and found to affect the reaction efficiency and product yields. Besides, the optimal Zr/SBA-15(20) catalyst maintained outstanding recyclability in the recycling test, offering almost comparable reaction yields as freshly prepared catalyst. This work not only opens up a new concept by using Lewis catalyst for HAA reaction to synthesize diesel precursors from biomass, but also enriches the catalyst inventory of HAA reaction by providing a pH-neutral, recyclable and stable catalyst.

Solventless C–C Coupling of Low Carbon Furanics to High Carbon Fuel Precursors Using an Improved Graphene Oxide Carbocatalyst

Graphene oxide, decorated with surface oxygen functionalities, has emerged as an alternative to precious-metal catalysts for many reactions. Herein, we report that graphene oxide becomes superactive for C–C coupling upon incorporation of a highly oxidized surface associated with Bronsted acidic oxygen functionality and defect sites along the surface and edges. The resulting improved graphene oxide (IGO) demonstrates significantly higher activity over commonly used framework zeolites for the upgrade of low-carbon biomass furanics to high-carbon fuel precursors. A maximum 95% yield of C15 fuel precursor with high selectivity is obtained at low temperature (60 °C) and neat conditions via hydroxyalkylation/alkylation (HAA) of 2-methylfuran (2-MF) and furfural. Coupling of 2-MF with carbonyl compounds ranging from C3 to C6 produces precursors of carbon numbers 12 to 21 with a high yield. The catalyst regains nearly full activity upon regeneration. Extensive microscopic and spectroscopic characterization of the...

Selective One-Pot Production of High-Grade Diesel-Range Alkanes from Furfural and 2-Methylfuran over Pd/NbOPO4.

A one-pot method for the selective production of high-grade diesel-range alkanes from biomass-derived furfural and 2-methylfuran (2-MF) was developed by combining the hydroxyalkylation/alkylation (HAA) condensation of furfural with 2-MF and the subsequent hydrodeoxygenation (HDO) over a multifunctional Pd/NbOPO4 catalyst. The effects of various reaction conditions as well as a variety of solid-acid catalysts and metal-loaded NbOPO4 catalysts were systematically investigated to optimize the reaction conditions for both reactions. Under the optimal reaction conditions up to 89.1 % total yield of diesel-range alkanes was obtained from furfural and 2-MF by this one-pot method.

Synthesis of renewable diesel with 2-methylfuran and angelica lactone derived from carbohydrates

Diesel and jet fuel range branched alkanes were first synthesized by the combination of hydroxyalkylation/alkylation (HAA) of 2-methylfuran with angelica lactone (AL) and subsequent hydrodeoxygenation.

Protonated titanate nanotubes as a highly active catalyst for the synthesis of renewable diesel and jet fuel range alkanes

Protonated titanate nanotube (PTNT) was first reported as a good catalyst for the hydroxyalkylation/alkylation (HAA) of 2-methylfuran (2-MF) and n-butanal from lignocellulose. Compared with other inorganic solid acids, PTNT has higher catalytic activity and efficiency. Over it, high yield of HAA product (77%) was achieved under mild reaction conditions. PTNT is also effective for the HAA (or alkylation) reactions between 2-MF and other lignocellulosic carbonyl compounds. According to the characterization results, the hydrothermal treatment of TiO2 P25 with NaOH solution and subsequent acidification significantly increases its BET surface area and the amount of acid sites on the surface of catalyst. Moreover, these pretreatments also lead to the generation of strong acid sites and Brönsted acid sites on the surface of catalyst. All of these changes are responsible for the excellent performance of PTNT. As the final aim of this work, the HAA product of 2-MF and n-butanal was converted to diesel and jet fuel range brached alkanes by the hydrodeoxygenation (HDO) over zeolite loaded Ni catalysts. Among them, Ni/H-ZSM-5 demonstrated the best catalytic performance and good stability, which makes it a promising catalyst in future application.

Lignosulfonate-based acidic resin for the synthesis of renewable diesel and jet fuel range alkanes with 2-methylfuran and furfural

Lignosulfonate-based acidic resins were reported as promising catalysts for the hydroxyalkylation/alkylation (HAA) of 2-methylfuran and furfural from lignocellulose.

Synthesis of Diesel or Jet Fuel Range Cycloalkanes with 2-Methylfuran and Cyclopentanone from Lignocellulose

2-Methylfuran (2-MF) and cyclopentanone (CPO) are the selective hydrogenation products of furfural, which can be produced in industrial scale with lignocellulose. In this work, renewable diesel or jet fuel range branched alkanes and cycloalkanes were first synthesized simultaneously by the solvent-free hydroxyalkylation/alkylation (HAA) of 2-MF and CPO followed by hydrodeoxygenation (HDO). Among the solid acid catalysts used in this work, Nafion-212 resin exhibited the best activity and selectivity for the HAA of 2-MF and CPO. The excellent performance of Nafion-212 resin can be attributed to the high acid strength of this catalyst. After the HDO of the HAA products of 2-MF and CPO over several nickel catalysts, a mixture of jet fuel range branched alkanes and cycloalkanes with relatively higher density was obtained at high carbon yield. Compared with Ni/SiO2, acidic support loaded nickel catalysts are more active in the HDO process, which may be attributed to the promotion effect of acid sites in dehydra...

Synthesis of renewable diesel with hydroxyacetone and 2-methyl-furan

Diesel or jet fuel range branched alkanes were synthesized for the first time by the combination of hydroxyalkylation-alkylation (HAA) of 2-methylfuran with hydroxyacetone and subsequent hydrodeoxygenation. Due to the electron-withdrawing effect of the hydroxyl group, the hydroxyacetone route exhibited evident advantages (higher HAA reactivity and diesel yield) over the previous acetone route.

Synthesis of High‐Quality Diesel with Furfural and 2‐Methylfuran from Hemicellulose

Hydroxyalkylation-alkylation (HAA) coupled with hydrodeoxygenation is a promising route for the synthesis of renewable high-quality diesel or jet fuel. In this work, a series of solid-acid catalysts were firstly used for HAA between lignocellulose-derived furan and carbonyl compounds. Among the investigated catalysts, Nafion-212 resin demonstrated the highest activity and stability. Owing to the high activity of the reactants and the advantage in industrial integration, the HAA of 2-methylfuran (2-MF) and furfural can be considered as a prospective route in future applications. Catalyst loading, reaction temperature, and time had evident effects on the HAA of 2-MF and furfural over Nafion-212 resin. Finally, the HAA product of 2-MF and furfural was hydrogenated over a Pd/C catalyst and hydrodeoxygenated over Pt-loaded solid-acid catalysts. Pt/zirconium phosphate (Pt/ZrP) was found to be the best catalyst for hydrodeoxygenation. Over the 4 % Pt/ZrP catalyst, a 94 % carbon yield of diesel and 75 % carbon yield of C15 hydrocarbons (with 6-butylundecane as the major component) was achieved.