Tandem Conversion Research Articles

Characterization of the NiSO4 site on a NiSO4-ReOx/γ-Al2O3 catalyst for tandem conversion of ethylene to propylene

A series of NiSO4-ReOx/Al2O3 catalysts were synthesized by a co-impregnation method, tested in the conversion of ethylene to propylene at mild conditions, and thoroughly characterized by different spectroscopy techniques. In particular, the attention was focused on the NiSO4 function, which is directly involved in ethylene conversion to 2-butylene, but also drives the catalyst deactivation. Results shows that the sulfate anions increase the surface acidity of alumina, and simultaneously influence the electronic properties of the Ni sites. Indeed, thermal activation of the catalyst promotes the formation of covalent bonds between the sulfate anions and the Ni2+ or Al3+ cations, while keeping constant the + 2 oxidation state of the Ni sites. Studying the initial steps of the ETP reaction reveals the primary acid-catalyzed formation of branched oligomers. Catalyst deactivation could be due to formation and adsorption of long-chain oligomers, or less interaction of sulfate anions with Ni ions.

Water-involved tandem conversion of aryl ethers to alcohols over metal phosphide catalyst

Lignin-derived compounds provide a platform for the production of value-added chemicals. Herein, we reported metal phosphide (Pd-Ni-P) catalyzed the conversion of diphenyl ether (DPE) via a restricted pathway involving partial hydrogenation-hydrolysis-hydrogenation. Cyclohexanol, an important raw material for the polymer industry, was therefore obtained as the main product in 87% mole yield with a high production rate of 14.65 mol·g−1Pd·h−1. The results of X-ray diffraction, X-ray absorption spectroscopy and X-ray photoelectron spectroscopy confirmed that Ni and P atoms were inserted into the face-centred cubic Pd lattices, leading to the expanded Ni-Ni lattices and Pd-P covalent bonds. The electronic deficient Pd contributes to the partial hydrogenation of DPE to cyclohexyl phenyl ether (CHPE), and the inserted Ni facilitates the hydrolysis of CHPE to monocycles. Various control experiments including deuterium experiment and reaction kinetic study revealed the strong hydrolysis ability of Pd-Ni-P catalyst accounting for the high production rate of cyclohexanol. Besides, several lignin-derived aryl ethers could undergo the same reaction pathway to produce alcohol chemicals with high yields ranging from 50% to 94%.

Elucidating the roles of acid site nature and strength in the direct conversion of levulinic acid into ethyl valerate: the case of Zr-modified beta zeolite-supported Pd catalysts

The strong Brønsted and Lewis acid sites are active in the tandem conversion of levulinic acid into ethyl valerate. The intrinsic activity of the former is more significant and the Pd/HBEA catalyst deactivation is partially reversible by calcination.

Influence of the Insertion of Zirconium Ion on the Catalytic Performance of Montmorillonite for One-Pot Tandem Conversion of Furfural to Γ-Valerolactone Under Mild Conditions

Influence of the Insertion of Zirconium Ion on the Catalytic Performance of Montmorillonite for One-Pot Tandem Conversion of Furfural to Γ-Valerolactone Under Mild Conditions

Oxidative Dehydrogenation of Propane with Carbon Dioxide Catalyzed by ZnxZr1–xO2–x Solid Solutions

Although the oxidative dehydrogenation of propane with CO2 (CO2-ODP) is a sustainable route for producing propylene with the tandem conversion of CO2 to the value-added CO, its industrialization is still challenged by the lack of an efficient catalyst, which originates from the insufficient understanding of the catalytic nature and reaction mechanism. In this work, ZnO-ZrO2 composites were probed as catalysts for CO2-ODP. A pure ZnxZr1–xO2–x solid solution was formed over ZnO-ZrO2 composites with 5–20 mol % ZnO, and the content of oxygen defects was almost directly proportional to the fraction of the solid solution. The amount and the mobility of lattice oxygen over ZnxZr1–xO2–x solid solutions were revealed as key factors in determining the catalytic performance. The CO2-ODP reaction over the best 20 mol %ZnO-ZrO2 catalyst occurred almost stoichiometrically via the redox mechanism, which can be an important guideline for further developing a high-performance catalyst for CO2-ODP.

Synthesis and consequence of Zn modified ZSM-5 zeolite supported Ni catalyst for catalytic aromatization of olefin/paraffin

Zn modified ZSM-5 zeolite supported Ni bifunctional catalysts were prepared by in-situ hydrothermal synthesis (Zn-Ni-ZSM-5), co-impregnation method (Zn-Ni/ZSM-5) as well as combining in-situ hydrothermal synthesis of Zn-ZSM-5 and sequential impregnation of Ni (Ni/Zn-ZSM-5) and used for the selective converting olefin to aromatics applicable for FCC gasoline hydro-upgrading. The Lewis (L) acid sites generated by ZnOH+ species and hydrogenation active sites from Ni0 species were varied with preparation method, in which their locations at the external surface or micropores of zeolite changed the acid properties of catalysts. Comparing to the Zn-Ni/ZSM-5 from the co-impregnation method, direct in-situ hydrothermal method could incorporate Zn and Ni species within zeolite, which makes the strong interaction between the metal species and the framework Al to form medium-strong L acids (ZnOH+/NiOH+). This leads to the decrease of ratio of Brønsted acid sites to L acid sites (B/L) from 0.40 to 0.12 and the difficulty in reducing of Ni cations to Ni0 from 57% to 30% Ni0 percent. Ni/Zn-ZSM-5 sample prepared by incorporating Zn species into micropores and sequential depositing Ni species at the external surface of zeolite possesses a low B/L ratio similar to Zn-Ni-ZSM-5 (0.20 versus 0.12) but a much higher Ni0 percent (52% versus 30%). Zn-Ni-ZSM-5 shows closer intimacy between Zn and Ni species comparing to Zn-Ni/ZSM-5 and Ni/Zn-ZSM-5. For the 1-hexene aromatization, the formed iso-alkene at acid sites was quickly saturated to iso-alkanes by the adjacent Ni0 particles over Ni-Zn-ZSM-5 catalyst in hydrogen steam. However, the location of aromatization active sites (ZnOH+, L acid sites) in micropores and hydrogenation active sites (Ni0 species) on external surface of Ni/Zn-ZSM-5 makes the tandem conversion of n-alkene → iso-alkene → aromatics, rather than the n-alkene → iso-alkene → iso-alkane. Thus, Zn-Ni-ZSM-5 with close intimacy of ZnOH+ and Ni0 particles shows a high iso-alkane selectivity (27.9% iC4+), while Ni/Zn-ZSM-5 exhibits a high aromatics selectivity (39.6 %) in the conversion of 1-hexene in hydrogen steam. Similar results have also found in the conversion of n-heptane. Here, the control of the intimacy of Zn and Ni in ZSM-5 zeolites has been realized to be a good protocol to adjust the selective conversion of olefins/alkanes to aromatics versus iso-alkanes.

Versatile One-Pot Tandem Conversion of Biomass-Derived Light Oxygenates into High-Yield Jet Fuel Range Aromatics

Valorization of biomass-derived oxygenates to jet fuel range aromatics harbors tremendous practical value due to growing concerns about the sustainable production of fuels and chemicals. Herein, bioderived C3 oxygenates with different functional groups including aldehydes, ketones, and alcohols were converted to jet fuel range hydrocarbons with high yield (maximum 86.1%) and purity (maximum 98.2%) and remarkably enhanced stability in a single continuous-flow reactor using nonprecious dual-bed catalysts. Instead of the conventional pathway (i.e., olefin generation following oligomerization), our strategy first transforms pronanal, propanol, and acetone into C9–C12 oxygenates via aldol condensation and ring closure reactions on the upstream Cu/SiO2 + TiO2 catalyst and subsequently converts the aldol-derived oxygenates through hydrogenation–dehydration–aromatization reactions on the downstream Ni/HZSM-5 catalyst at a relatively moderate temperature (573 K) and atmospheric pressure. This versatile and atom-economic strategy opens new opportunities for the efficient upgradation of bio-oil-derived oxygenates to renewable jet fuel range aromatics.

Chemically functionalized MIL-101-NH2 with cobalt(II) tetrasulfophthalocyanine: an efficient catalyst for the aerobic oxidation of alcohols and one-pot tandem conversion of alcohols to propargylamines

In this investigation, MIL-101-NH2 chemically functionalized with cobalt(II) tetrasulfophthalocyanine (CoTSPc) through a superior electrostatic interaction reaction. The configuration of the synthesized composite was characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscope (SEM), and inductively coupled plasma optical emission spectrometer (ICP-OES). This spongy composite showed excellent catalytic activity in the aerobic oxidation reaction of primary and secondary benzylic alcohols. The generated catalyst's behavior was examined to synthesize propargylamines via tandem oxidative A3 coupling process to illustrate the maximum potential of the synthesized catalyst. Utilizing air as an oxidant, operational simplicity, easy preparation, apt yielding, non‐hazardous nature of the catalyst, and reusability are the essential advantages of this catalyst.

Tandem Synthesis of ϵ‐Caprolactam from Cyclohexanone by an Acidified Metal‐organic Framework

AbstractTandem synthesis of ϵ‐caprolactam, one of the largest scaled commercial chemicals, is highly desired from the viewpoint of cost, energy, and environment. However, relevant studies have remained largely underexplored. By using a one‐pot strategy, we encapsulated phosphotungstic acid (PTA) into a chromium terephthalate metal‐organic framework (MOF), MIL‐101, for the efficient tandem conversion of cyclohexanone to ϵ‐caprolactam. The highly dispersed PTA in the MOF matrix showed a high yield of ϵ‐caprolactam through a tandem oximation‐Beckmann rearrangement reaction at 100 °C for 12 h. Moreover, MIL‐101‐PTA was recycled three times, with only a slight loss in their catalytic performance. To the best of our knowledge, this represents the first report using acidified MOF for a tandem oximation‐Beckmann rearrangement reaction.

A cobalt coordination polymer from bulk to nanoscale crystals as heterogeneous catalysts for tandem reactions

Constructing nanoscale coordination polymers (CPs) with different micro- or nanoscale morphologies and sizes is crucial for the functionalization of CPs-based heterogeneous catalysts. Herein, surfactant polyvinylpyrrolidone (PVP), surface-supported frameworks (filter paper or Ni foam), and Co-based CPs (1), [Co2(pdpa)(py)4(H2O)]n (H4pdpa ​= ​5,5’-(pentane-1,2-diyl)-bis(oxy)diisophthalic; py ​= ​pyridine)) were employed to develop highly ordered micro- or nanoscale CPs, achieving microscale 1a (without surface-supported framework) and nanoscale 1b-c (filter paper and Ni foam as surface-supported frameworks for 1b and 1c, respectively). Furthermore, the catalytic performance of nanoscale 1c with spheric particles for the tandem conversion reactions of aromatic nitriles and diamines into imidazoline or tetrahydropyrimidine frameworks was much more prominent than that of large scale 1, microscale 1a, and nanoscale 1b because of the easily accessible catalytic active sites in the nanoscale spheric particles, which offered a functionalizable platform for the tandem reactions by minimizing the diffusion distance but did little for their activity.

Efficient Conversion of Glucose to 5-Hydroxymethylfurfural over a Sn-Modified SAPO-34 Zeolite Catalyst

Efficient and one-pot conversion of biomass-derived carbohydrate into highly value-added 5-hydroxymethylfurfural (HMF) is a crucial reaction step for the valorization of biomass resources toward bio-based chemicals and fuels. In this work, a series of Sn/SAPO-34 catalysts were prepared through impregnation and evaluated in glucose conversion to HMF. The physicochemical properties of Sn/SAPO-34 catalysts were systematically characterized by SEM, XRD, N2 physisorption, XPS, solid-state 119Sn, 29Si, and 31P NMR, XRF, UV–vis, NH3-TPD, and pyridine-FTIR techniques. It was demonstrated that controlling the Sn loading amount could facilely adjust the acid strength and acid amount of the SAPO-34 zeolite. The incorporation of Sn species could induce the formation of a tetrahedrally coordinated Sn4+ site and Sn-OH site to improve the amounts of Bronsted and Lewis acid sites of the catalyst. However, modification with sufficiently high Sn loading could decrease the acid strength and performance of the catalyst owing to its structure damage. The 5%Sn/SAPO-34 catalyst (i.e., Sn loading calculated based on the mass ratio of SnCl4·5H2O as a precursor to the parent SAPO-34) was found to exhibit the superior catalytic performance under mild conditions and could afford an HMF yield of 64.4% at 98.5% glucose conversion in a biphasic 35 wt % NaCl-H2O/tetrahydrofuran (THF) system at 150 °C within 1.5 h. Additionally, a catalytic reaction pathway was proposed, involving the adsorption of glucose molecules by the −Cl group on the catalyst via a hydrogen bond, followed by glucose isomerization to fructose over the Lewis acid Sn4+ and Al3+ sites and, finally, fructose dehydration to HMF catalyzed by the Bronsted acid Sn-OH and Si-OH-Al sites. The activity of the catalyst decreased due to the leaching of the active site Sn after several consecutive cycles. This work provides insights into the improvement in the Sn-containing zeolite catalyst for tandem conversion of glucose to HMF.

Tandem Lewis acid catalysis for the conversion of alkenes to 1,2-diols in the confined space of bifunctional TiSn-Beta zeolite

The generation of multifunctional isolated active sites in zeolite supports is an attractive method for integrating multistep sequential reactions into a single-pass tandem catalytic reaction. In this study, bifunctional TiSn-Beta zeolite was prepared by a simple and scalable post-synthesis approach, and it was utilized as an efficient heterogeneous catalyst for the tandem conversion of alkenes to 1,2-diols. The isolated Ti and Sn Lewis acid sites within the TiSn-Beta zeolite can efficiently integrate alkene epoxidation and epoxide hydration in tandem in a zeolite microreactor to achieve one-step conversion of alkenes to 1,2-diols with a high selectivity of >90%. Zeolite confinement effects result in high tandem rates of alkene epoxidation and epoxide hydration as well as high selectivity toward the desired product. Further, the novel method demonstrated herein can be employed to other tandem catalytic reactions for sustainable chemical production.

Unusual C3-acetylation of quinoxalin-2(1H)-one via oxidative C-C and C-O bond cleavages of PEG-400.

Aerobic oxidative tandem conversion of PEG-400 to acetyl radical via C-C and C-O bond cleavages followed by silver-catalyzed menisci-type addition to the C3 position of quinoxalin-2(1H)-one is described. This reaction involves the in situ formation of the acetyl radical from PEG-400 via a sequence of acetaldehyde, 2-oxopropanal and, 2-oxopropanoic acid formation and successive oxidative cleavage to form the acetyl radical. This protocol uses cheap, readily available and environmentally-friendly PEG-400 as the acetyl source and solvent. The in situ generated acetyl radicals from PEG-400 have been coupled to a broad range of electron-deficient quinoxalin-2(1H)-one compounds in a menisci-type reaction.

Tandem conversion of lignin to catechols via demethylation and catalytic hydrogenolysis

Lignin is regarded as a potential source of various aromatic compounds and chemicals, replacing petrochemicals. Catechol and its derivatives are important platform chemicals in many industrial sectors, including agrochemicals and pharmaceuticals. The global market of catechols is expected to increase with emerging demand in end-use industries. Considering that the current production of catechols relies on fossil fuels, it is critical to seek alternative renewable sources to respond to sustainability challenges. In this respect, lignin is viewed as a promising material due to its abundance and renewable character. Also, the structural similarity to catechols has made lignin a potential feedstock for the production of bio-catechols. However, the lignin-to-catechols conversion approach is still in an early stage because the intractable nature of lignin and the complex mixture of the depolymerized products make its valorization less feasible. Herein, we report a selective production of catechols via tandem conversion of lignin, namely, demethylation followed by catalytic hydrogenolysis (DFCH). The DFCH of lignin resulted in catechol- and catechol derivatives-rich liquid, accounting for 80 % in the identified products. The reaction mechanisms were also studied by quantum calculations to provide a fundamental understanding of the conversion. The result proves that selective modification of lignin structure is a promising approach to produce specific platform chemicals, providing insights toward an efficient strategy for lignin valorization.

Tertiary Amine-Ethylene Glycol Based Tandem CO2 Capture and Hydrogenation to Methanol: Direct Utilization of Post-Combustion CO2.

Carbon dioxide capture using tertiary amines in ethylene glycol solvent was performed under ambient conditions. Subsequently, the CO2 captured as alkyl carbonate salts was successfully hydrogenated to methanol, in the presence of H2 gas and Ru-Macho-BH catalyst. A comprehensive series of tertiary amines were selected for the integrated capture and conversion process. While most of these amines were effective for CO2 capture, tetramethylethylenediamine (TMEDA) and tetramethylbutanediamine (TMBDA) provided the best CH3 OH yields. Deactivation of the base due to side reactions was significantly minimized and substantial base regeneration was observed. The proposed system was also highly efficient for CO2 capture from a gas mixture containing 10 % CO2 , as found in flue gases, followed by tandem conversion to CH3 OH. We postulate that such high boiling tertiary amine-glycol systems as dual capture and hydrogenation solvents are promising for the realization of a sustainable and carbon-neutral methanol economy in a scalable process.

An Effective Hybrid Strategy for Conversion of Biomass into Furfurylamine by Tandem Pretreatment and Biotransamination.

In this work, an effective hybrid strategy was developed for tandem conversion of biomass to furfurylamine with tin-based solid acid Sn-Maifanitum stone and recombinant Escherichia coli whole cells harboring ω-transaminase. 90.3mM furfural was obtained from corncob (75g/L) at 170°C for 0.5h over Sn-Maifanitum stone catalyst (3.5wt%) in the aqueous media (pH 1.0), which could be further bioconverted into furfurylamine at 74.0% yield (based on biomass-derived furfural) within 20.5h. Finally, an efficient recycling and reuse of Sn-Maifanitum stone catalyst and immobilized Escherichia coli AT2018 whole-cell biocatalyst was developed for the synthesis of furfurylamine from biomass in the one-pot reaction system.

Dimethyl Sulfoxide as an Oxygen Atom Source Enabled Tandem Conversion of 2‐Alkynyl Carbonyls to 1,2‐Dicarbonyls

AbstractA tandem transformation of 2‐alkynyl carbonyl compounds by means of a CuBr2/I2/DMSO/water system is developed, enabling the fromation of various functionalized 1,2‐dicarbonyl compounds, including 1,2‐diketones, α‐keto amides and α‐keto ester. This Cu‐promoted iodine‐mediated tandem procedure employs DMSO as the oxygen atom source of the formed carbonyl group through iodonium ion formation, nucleophilic DMSO addition and C−C bond cleavage cascades.magnified image

Synthesis of a Sustainable Cellulose-Derived Biofuel Through a 1-Pot, 2-Catalyst Tandem Reaction

The preparation, characterisation and application of two catalysts active in selective hydrogenation (Pt/TiO2) and esterification (mesoporous SiO2 material modified with tethered sulfonic acid groups) reactions is described. The catalysts are characterised using a range of spectroscopic, microscopic and adsorption techniques. Pt/TiO2 catalysts promote valeric acid (a cellulose derived platform molecule) hydrogenation to pentanol, while –SO3H modified mesoporous SiO2 catalysts convert valeric acid/pentanol mixtures to pentyl valerate (a 10-C molecule which can be used as a diesel fuel substitute). Admixtures of the two catalysts catalyse the tandem conversion of valeric acid/hydrogen mixtures to form pentyl valerate in a single reaction. A rationale for the observed reactivity, selectivity and carbon balance is proposed.

Nickel salt of phosphomolybdic acid as a bi-functional homogeneous recyclable catalyst for base free transformation of aldehyde into ester.

A Ni salt of phosphomolybdic acid (NiHPMA) was synthesized and characterized by various physico-chemical techniques such as EDX, UV-Visible spectroscopy, FT-IR, Raman spectroscopy and XPS. FT-IR and Raman spectroscopy confirm the presence of Ni as a counter cation while UV-Visible and XPS studies to confirm the presence of Ni(ii) in the catalyst. The catalyst was evaluated for its bi-functional activity towards the tandem conversion of benzaldehyde to ethyl benzoate and it was found that very small amounts of Ni (2.64 × 10−3 mmol) enhance the selectivity towards benzoate. A detailed mechanistic study was carried out by UV-Visible and Raman spectroscopy to confirm that both intermediate species, Mo–peroxo and Ni–oxo, are responsible for higher selectivity towards esters. Further, a study to determine the effect of addenda atoms (heteropoly acid) was also carried out. The catalyst was also found to be viable for a number of aldehydes under optimized conditions.

One-pot construction of dispirocyclohexanes via K2CO3-mediated desulfonylative Michael-Michael-aldol (2 + 2 + 2) annulation of sulfonyl 2-pyridyl flavanones and methylketones.

K2CO3-mediated one-pot tandem conversion from sulfonyl 2-pyridyl flavanones to dipyridyl dispirocyclohexanes with contiguous multiple stereogenic centers was accomplished in good yields via an intramolecular desulfonylative ring-contraction of sulfonyl 2-pyridyl flavanones followed by an intermolecular Michael-Michael-aldol (2 + 2 + 2) annulation of the resulting pyridyl aurone intermediate with methyl ketones under facile, open-vessel, inexpensive and environmentally friendly reaction conditions. A plausible mechanism is proposed and discussed herein. This protocol provides a highly effective ring-closure via three carbon-carbon (C-C) bond formation.