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Publication YXY 2012

Accelerating research into bio-based FDCA-polyesters by using small scale parallel film reactors

G.-J. M. Gruter, L. Sipos, M. A. Dam, Comb. Chem. High Throughput Screening 2012, 15, 180.



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High Throughput experimentation was well established as a tool in early stage catalyst development and catalyst and process scale-up today. One of the more challenging areas of catalytic research is polymer catalysis. The main difference with most non-polymer catalytic conversions is the fact that the product is not a well defined mol. and the catalytic performance cannot be easily expressed only in terms of catalyst activity and selectivity.

In polymn. reactions, polymer chains are formed that can have various lengths (resulting in a mol. wt. distribution rather than a defined mol. wt.), that can have different compns. (when random or block co-polymers are produced), that can have crosslinking (often significantly affecting phys. properties), that can have different end-groups (often affecting subsequent processing steps) and several other variations. In addn., for polyolefins, mass and heat transfer, oxygen and moisture sensitivity, stereoregularity and many other intrinsic features make relevant high throughput screening in this field an incredible challenge.

For polycondensation reactions performed in the melt often the viscosity becomes already high at modest mol. wts., which greatly influences mass transfer of the condensation product (often water or methanol). When reactions become mass transfer limited, catalyst performance comparison is often no longer relevant. This however does not mean that relevant expts. for these application areas cannot be performed on small scale.

Relevant catalyst screening expts. for polycondensation reactions can be performed in efficient small scale parallel equipment. Both transesterification and polycondensation and post condensation through solid-stating in parallel equipment were developed. Next to polymer synthesis, polymer characterization also needs to be accelerated without making concessions to quality to draw relevant conclusions.

Publication Catalysis 2012

Au/Mo2N as a new catalyst formulation for the hydrogenation of p-chloronitrobenzene in both liquid and gas phases

F. Cardenas-Lizana, D. Lamey, N. Perret, S. Gomez-Quero, L. Kiwi-Minsker, M. A. Keane, Catal. Commun. 2012, 21, 46.

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The batch liq. phase hydrogenation of p-chloronitrobenzene over Mo2N resulted in the sole formation of p-chloroaniline (I). Incorporation of Au nanoparticles (mean size = 8 nm) enhanced hydrogen uptake with a four-fold increase in rate, retention of ultraselectivity with stability over repeated reaction cycles. Reaction exclusivity to I extended to continuous gas-phase operation where Au/Mo2N outperformed Au/Al2O3 as a benchmark. Under the same conditions, Pd/Mo2N was nonselective, generating nitrobenzene and aniline via combined hydrodechlorination and hydrogenation. These results demonstrate the viability of Au/Mo2N as a new catalyst formulation in selective substituted nitroarene hydrogenation.

Publication Catalysis 2012

High selectivity production of propylene from 2-butene: non-degenerate pathways to convert symmetric olefins via olefin metathesis

E. Mazoyer, K. C. Szeto, J.-M. Basset, C. P. Nicholas, M. Taoufik, Chem. Commun. (Cambridge, U. K.) 2012, 48, 3611.

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The first example of propylene prodn. from 2-butene in promising yield is described by reacting trans-2-butene over tungsten hydrides precursor W-H/Al2O3 at 150 °C and different pressures in a continuous flow reactor. The tungsten carbene-hydride active site operates as a "bi-functional catalyst" through the disfavored 2-butene isomerisation on W-hydride and 2-butenes/1-butene cross-metathesis on W-carbene.





Publication Catalysis 2011

Photo-catalytic oxidation of cyclohexane over TiO2: A novel interpretation of temperature dependent performance

A. R. Almeida, R. Berger, J. A. Moulijn, G. Mul, Phys. Chem. Chem. Phys. 2011, 13, 1345.

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The rate of cyclohexane photo-catalytic oxidn. to cyclohexanone over anatase TiO2 was studied at 23-60 °C by in situ ATR-FTIR spectroscopy, and the kinetic parameters were estd. using a microkinetic model. At low temps., surface cyclohexanone formation is limited by cyclohexane adsorption due to unfavorable desorption of H2O, rather than previously proposed slow desorption of the product cyclohexanone. Up to 50 °C, the activation energy for photocatalytic cyclohexanone formation is zero, while carboxylates are formed with an activation energy of 18.4 ± 3.3 kJ mol-1. Above 50 °C, significant (thermal) oxidn. of cyclohexanone contributes to carboxylate formation.

The irreversibly adsorbed carboxylates lead to deactivation of the catalyst, and are most likely the predominant cause of the non-Arrhenius behavior at relatively high reaction temps., rather than cyclohexane adsorption limitations. The results imply that elevating the reaction temp. of photocatalytic cyclohexane oxidn. reduces selectivity, and is not a means to suppress catalyst deactivation.



Publication Catalysis 2011

Combined ATR-FTIR and DFT Study of Cyclohexanone Adsorption on Hydrated TiO2 Anatase Surfaces

A. R. Almeida, M. Calatayud, F. Tielens, J. A. Moulijn, G. Mul, J. Phys. Chem. C 2011, 115, 14164.

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The adsorption of cyclohexanone on different planes ((100), (101), and (001)) of anatase TiO2, with variable level of hydration, was evaluated by d. functional theory (DFT) calcns. Surface hydration was found to affect the cyclohexanone adsorption enthalpy and the calcd. IR absorption frequencies of the preferred adsorbed configurations considerably. A good correlation was found between two exptl. obsd. absorption frequencies at 1694 and at 1681 cm-1 of cyclohexanone adsorbed on TiO2, detd. by attenuated total reflection FTIR (ATR-FTIR), and frequencies calcd. for conformations of cyclohexanone interacting with the (101) surface with low and intermediate levels of hydration, resp.

The corresponding adsorption enthalpies of these adsorbed conformations amt. to -23.5 and -37.0 kJ/mol, resp. DFT calcns. show that cyclohexanone physisorption on hydrated (100) yields an adsorption enthalpy of -89.4 kJ/mol. This might be a conformation contributing to irreversible adsorption of cyclohexanone known to occur exptl. after photocatalytic activation of TiO2. Other phenomena of relevance to irreversible adsorption are also briefly discussed.



Publication Catalysis 2011

Heterogeneously Catalyzed Continuous-Flow Hydrogenation Using Segmented Flow in Capillary Columns

J. J. W. Bakker, M. M. P. Zieverink, R. W. E. G. Reintjens, F. Kapteijn, J. A. Moulijn, M. T. Kreutzer, ChemCatChem 2011, 3, 1155.

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This paper explores how the visible features of segmented-flow, under reaction conditions, can be used in lab.-scale multi-phase heterogeneous catalysis. Segmented-flow accelerates optimization of continuous-flow hydrogenations using heterogeneous catalysis. Conversion can be monitored visually, which gives hands-on control over the activity and deactivation of the catalyst. Reagents exchange rapidly with the catalyst and without axial dispersion, yields are the same as in batch. It is shown that continuous-flow anal. allows a fast optimization of various aspects of heterogeneous catalysis and synthesis routes, such as solvent effects, competitive adsorption and irreversible poisoning.



Publication Catalysis 2011

Gold catalysis at the gas-solid interface: role of the support in determining activity and selectivity in the hydrogenation of m-dinitrobenzene

F. Cardenas-Lizana, S. Gomez-Quero, N. Perret, M. A. Keane, Catal. Sci. Technol. 2011, 1, 652.

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The catalytic gas phase hydrogenation of m-dinitrobenzene (1 atm, 423 K) over lab. synthesized (1 mol.%) Au supported on Al2O3, TiO2, Fe2O3, and CeO2 and a ref. Au/TiO2 (World Gold Council) has been investigated. The catalysts were prepd. by deposition-pptn. (DP) and impregnation (IMP), where the former route generated smaller (surface area weighted) mean Au particle sizes (1.5-2.8 nm) compared with the IMP synthesis (3.5-9.0 nm).

The catalysts have been characterized in terms of temp. programmed redn. (TPR), H2 chemisorption/temp. programmed desorption (TPD), BET area, powder x-ray diffraction, and high resoln. TEM (HRTEM) analyses. Hydrogen consumption over the T range 371-457 K during activation of Au on TiO2, Al2O3, and CeO2 can be assocd. with Au3+ Au0 redn. X-ray diffraction anal. demonstrated the presence of metallic gold in Au/Fe2O3pre-TPR. A partial and complete redn. of the hematite support to magnetite (Fe2O3 Fe3O4) was obsd. post-TPR to 423 and 673 K, resp.; H2-TPD results suggest the participation of spillover hydrogen in this step. Exclusive -NO2 group redn. and time invariant conversions were obsd. for all the catalysts considered in this study. An increase in the specific hydrogenation rate with a decrease in the mean Au size (from 9 to 3 nm) was obsd.

M-Nitroaniline was generated as the sole product over Au/TiO2 and Au/Fe2O3 whereas Au/CeO2 promoted the exclusive formation of m-phenylenediamine and a mixt. of both products was obtained over Au/Al2O3. Our findings establish a basis for the development of a sustainable (clean and continuous) process for the hydrogenation of m-dinitrobenzene where product compn. can be controlled through the choice of the oxide support.



Publication Catalysis 2011

Beta-Molybdenum nitride: synthesis mechanism and catalytic response in the gas phase hydrogenation of p-chloronitrobenzene

F. Cardenas-Lizana, S. Gomez-Quero, N. Perret, L. Kiwi-Minsker, M. A. Keane, Catal. Sci. Technol. 2011, 1, 118.

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A temp. programmed treatment of MoO3 in flowing N2 + H2 has been employed to prep. β-phase molybdenum nitride (β-Mo2N) which has been used to promote, for the first time, the catalytic hydrogenation of p-chloronitrobenzene. The redn./nitridation synthesis steps have been monitored in situ and the starting oxide, reaction intermediates and nitride product have been identified and characterized by powder X-ray diffraction (XRD), diffuse reflectance UV-vis (DRS UV-Vis), elemental anal., SEM, and BET/pore vol. measurements.

Our results demonstrate that MoO3 β-Mo2N is a kinetically controlled process where an initial redn. stage generates (sequentially) MoO2 and Mo as reaction intermediates with a subsequent incorporation of N to produce β-Mo2N. SEM anal. has established that the transformation is non-topotactic with a disruption to the platelet morphol. that characterizes MoO3 and an increase in BET area (from 1 m2/g-1 to 17 m2/g-1). Moreover, temp. programmed desorption measurements have revealed a significant hydrogen uptake (0.71 μmol m-2) on β-Mo2N.

This has been exploited in the hydrogenation of p-chloronitrobenzene where p-chloroaniline was generated as the sole product with an assocd. rate const. (k = 2.0 min-1) that is higher than values recorded for supported transition metals. Our study establishes the reaction mechanism involved in the synthesis of β-Mo2N and demonstrates its viability to promote selective -NO2 group redn. as an alternative sustainable, high throughput route to com. important haloamines.



Publication YXY 2011

Promising results with YXY Diesel components in an ESC test cycle using a PACCAR Diesel engine

E. de Jong, T. Vijlbrief, R. Hijkoop, G.-J. M. Gruter, J. C. van der Waal, Biomass Bioenergy 2011, 36, 151.

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A new process to produce YXY fuel components from carbohydrates is under development by Avantium. YXY fuel components are furan-based mono- and diethers with good fuel blending properties and a relatively high energy d. In this paper the engine performance of a wide range of Diesel-YXY mixts. was tested using an ESC test with a 6 cylinder PACCAR heavy duty engine. At all conditions tested (different blendings and different steps in the ESC cycle) no difference in the engine operation was obsd. Ethoxymethyl THF Ether (ETE) gave the best results with substantial redns. in particulate matter (%) and smoke (%) at up to 30% (vol./vol.) blending ratios while NOx and max. cylinder pressure were only marginally changed. Furfuryl Et Ether (FEE) also caused substantial redns. of soot however, at the cost of higher NOx formation and a stronger oscillating effect in the max cylinder pressure.

Applying a 1:1 mixt. of the ETE/FEE YXY mols. quenched the effect seen with FEE alone indicating the strength of producing mixts. of different YXY mols. as the ideal fuel component. Further research will address the elastomer compatibility of the different YXY mols. and if higher alcs. (e.g. n-butanol, t-butanol) for the etherification will make the fuels even better fitting the Diesel fuel range (improved energy content, higher flashpoint, b.p.).



Publication YXY 2011

Catalyst behavior for 1-pentene and 4-methyl-1-pentene polymerization for C2-, Cs- and C1-symmetric zirconocenes

C. Descour, R. Duchateau, M. R. Mosia, G.-J. M. Gruter, J. R. Severn, S. Rastogi, Polym. Chem. 2011, 2, 2261.

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1-Pentene and 4-methyl-1-pentene (4M1P) have been polymd. using several C2-sym. ansa-zirconocene catalysts rac-X(2-R1,4-R2-Ind)2ZrCl2 X = C2H4, R1 = R2 = H (I); X = SiMe2, R1 = R2 = H (II); X = SiMe2, R1 = Me, R2 = H (III); X = SiMe2, R1 = H, R2 = Ph (IV); X = SiMe2, R1 = Me, R2 = Ph (V) with MAO as cocatalyst. The effects of polymn. conditions as well as substituents on the indenyl ligand were studied. Except for the poly-1-pentenes synthesized with III and V at low temps., low mol. wt. isotactic polymers were generally obtained.

Compared to their behavior in propylene polymn., the relative activity and selectivity of catalysts I, II, III, IV, and V are considerably different for 1-pentene and 4M1P polymn. Of the five catalysts, I and IV showed the highest activities for both 1-pentene and 4M1P polymn., while V resulted in the lowest activities, esp. for 4M1P polymn. Subsequently, a Cs- and several C1-sym. zirconocenes, (R1)2C(3-R2-Cp)(2,7,-R3-Flu)ZrCl2 R1 = Me, R2 = R3 = H; R1 = R2 = Me, R3 = H; R1 = Me, R2 = tert-Bu, R3 = H; R1 = Me, R2 = R3 = tert-Bu; R1 = Ph, R2 = tert-Bu, R3 = H; and R1 = Ph, R2 = R3 = tert-Bu, were tested in 1-pentene and 4M1P polymn. with MAO as cocatalyst.

The effect of substituents on the bridge and the cyclopentadienyl (Cp) and fluorenyl (Flu) ligands was studied relative to the polymn. temp. and type of monomer. The mol. wts. of the polymers were considerably higher than those of the poly-1-pentenes and P4M1Ps obtained with the C2-sym. zirconocenes. The catalytic activities and polymer mol. wts. strongly depend on the fluorenyl substituent and the bridge, while the type of substituent on the Cp ligand has a strong influence on the tacticity of the polymers.



Publication YXY 2011

Lignin depolymerisation in supercritical carbon dioxide/acetone/water fluid for the production of aromatic chemicals

R. J. A. Gosselink, W. Teunissen, J. E. G. van Dam, E. de Jong, G. Gellerstedt, E. L. Scott, J. P. M. Sanders, Bioresour. Technol. 2011, 106, 173.

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Valorisation of lignin plays a key role in further development of lignocellulosic biorefinery processes the prodn. of biofuels and bio-based materials. In the present study, organosolv hardwood and wheat straw lignins were converted in a supercrit. fluid consisting of carbon dioxide/acetone/water (300-370 °C, 100 bar) to a phenolic oil consisting of oligomeric fragments and monomeric arom. compds. with a total yield of 10-12% based on lignin.

These yields are similar to the state-of-the-art technologies such as base-catalyzed thermal processes applied for lignin depolymn. Addn. of formic acid increases the yield of monomeric arom. species by stabilizing arom. radicals. Supercrit. depolymn. of wheat straw and hardwood lignin yielded monomeric compds. in different compns. with a max. yield of 2.0% for syringic acid and 3.6% for syringol, resp. The results of the present study showed that under the applied conditions competition occurred between lignin depolymn. and recondensation of fragments.



Publication Catalysis 2011

Production of Propylene from 1-Butene on Highly Active "Bi-Functional Single Active Site" Catalyst: Tungsten Carbene-Hydride Supported on Alumina

E. Mazoyer, K. C. Szeto, S. Norsic, A. Garron, J.-M. Basset, C. P. Nicholas, M. Taoufik, ACS Catal. 2011, 1, 1643.

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1-Butene is transformed in a continuous flow reactor over tungsten hydride precursor W-H/Al2O3, giving a promising yield of propylene at 150 °C and different pressures. The tungsten carbene-hydride single active site operates as a bifunctional catalyst through 1-butene isomerization on W-hydride and 1-butene/2-butenes cross-metathesis on W-carbene. This active moiety is generated in situ in the initiation steps by insertion of 1-butene on tungsten hydride precursor W-H/Al2O3, followed by α-H and β-H abstraction.



Publication Catalysis 2011

Novel and Effective Copper-Aluminum Propane Dehydrogenation Catalysts

J. Schaeferhans, S. Gomez-Quero, D. V. Andreeva, G. Rothenberg, Chem.--Eur. J. 2011, 17, 12254.

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We report here a new effective Cu-Al catalyst for dehydrogenation of propane at low temp. The catalyst is oxidized porous alloy with the structure similar to that of Raney-type catalyst. High power ultrasound was used for the creation of porous structure. A series of catalysts with various Cu content was prepd. The catalysts were activated under different conditions. Due to high activity and absence of noble metals, these catalysts open exciting opportunities for low-temp. dehydrogenation catalysts.



Publication YXY 2011

The high-throughput research approach to biorefineries - a powerful tool for studying the complexity of catalytic processes

J. C. Van der Waal, R.-J. Van Putten, E.-J. Ras, M. Lok, G.-J. Gruter, M. Brasz, E. De Jong, Cellul. Chem. Technol. 2011, 45, 461.

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The integration of complex catalytic reactions in biorefineries will require a considerable research effort. Up-front new catalysts will have to be developed and the ever changing feed compn. and impurity profiles of biomass will require fast const. adjustments of the process. The capabilities of High-throughput methodologies to simultaneously perform several reactions will offer advantages for the development of the new processes required and in the daily operation of the new biorefinery concepts.

Publication Catalysis 2011

High-throughput experimentation in syngas based research

J. K. van der Waal, G. Klaus, M. Smit, C. M. Lok, Catal. Today 2011, 171, 207.

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The potential of high-throughput technol. in studying catalysts and processes in syngas R&D was demonstrated through a series of Fischer-Tropsch studies. The results show that the exothermal nature of the processes is an important consideration in catalyst evaluations. In order to discriminate on the intrinsic catalytic properties, small reactor diams. are preferred. A three-month life-time study, performed on a 64-reactor high-throughput nanoflow unit, showed a reactor-to-reactor reproducibility within 95% for catalyst activity. The ageing behavior as function of catalyst compn., GHSV and temp. variation could be studied simultaneously, saving over 98% in exptl. time compared to conventional 1-reactor systems.

The consistent correlation between gas and liq. phase selectivity allows for measuring just the gas phase, simplifying reactor set up and reducing operational efforts, at least when no carbon chain-length dependent selectivity is expected. A study into prepn. variables for Ru catalysts showed that silica supports promote the formation of ethanol. This is possibly formed by hydration of ethylene catalyzed by the acidic silica support.



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