Publications
186 results found
Peng S, Chadwick D, 2023, Selective oxidation of cyclohexane over nanostructured manganese tungstate: Contribution of Mn and W related sites, Catalysis Communications, Vol: 185, ISSN: 1566-7367
Nanostructured MnWO4 catalysts prepared with different initial pH exhibited systematic variation in the activity in the selective oxidation of cyclohexane. 2-propanol TPD showed that the ratio of Mn to W related sites increased with the initial synthesis pH. W sites were found to be mainly active in the formation of CHHP and dehydrogenation of cyclohexanol, while Mn sites appeared to be more active in decomposition of CHHP and deep oxidation, giving a significant selectivity to adipic acid. The high yield of KA oil at intermediate synthesis pH suggests an optimum balance of Mn and W surface sites.
Bernardi A, Bello F, Valente A, et al., 2022, Enviro-economic assessment of DME synthesis using carbon capture and hydrogen from methane pyrolysis, Computer Aided Chemical Engineering, Pages: 1003-1008
The catalytic conversion of captured CO2 and H2 into fuels is recognised as an interesting option to decarbonise the transport sector in the short-midterm future. DME has been identified as an ideal diesel-substitute for heavy-duty vehicles due to its high cetane number and excellent combustion properties, but to be competitive with diesel a low-cost and low-carbon H2 production route is a key enabler. Recent developments indicate that methane pyrolysis has the potential to produce H2 at a similar cost compared to steam methane reforming, the main H2 production route nowadays, yet with no direct CO2 emissions. This paper presents an enviro-economic assessment of 12 life-cycle pathways for DME production. Our results show that DME produced using H2 from methane pyrolysis could be competitive with diesel, both economically and environmentally, but is highly dependent upon the utilisation of the carbon by-product.
Zhang R, Chutia A, Sokol AA, et al., 2021, A computational investigation of the adsorption of small copper clusters on the CeO<sub>2</sub>(110) surface, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 23, Pages: 19329-19342, ISSN: 1463-9076
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- Citations: 4
Khawaji M, Graça I, Ware E, et al., 2021, Catalytic oxidation of glucose over highly stable AuxPdy NPs immobilised on ceria nanorods, Catalysis Today, Vol: 365, Pages: 257-264, ISSN: 0920-5861
The catalytic performance of AuxPdy nanoparticles prepared by colloidal synthesis and immobilised on ceria nanorods (Ce-NR) in the selective oxidation of glucose has been studied under initially basic and relatively mild conditions. Activity was found to be strongly dependent on the bimetallic composition with Au-rich catalysts being more active in glucose oxidation. Catalyst recycling revealed negligible deactivation or metal loss from leaching, and continuing high selectivity to gluconic acid (≥97.7%). Defects on the Ce-NR surface appear to serve as anchoring sites for Au-Pd NPs giving rise to small and very stable NPs.
Al-Shihri S, Richard CJ, Al-Megren H, et al., 2020, Insights into the direct selective oxidation of methane to methanol over ZSM-5 zeolytes in aqueous hydrogen peroxide, CATALYSIS TODAY, Vol: 353, Pages: 269-278, ISSN: 0920-5861
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- Citations: 9
Graca I, Chadwick D, 2020, NH<sub>4</sub>-exchanged zeolites: Unexpected catalysts for cyclohexane selective oxidation, MICROPOROUS AND MESOPOROUS MATERIALS, Vol: 294, ISSN: 1387-1811
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- Citations: 12
Iruretagoyena D, Bikane K, Sunny N, et al., 2020, Enhanced selective adsorption desulfurization on CO2 and steam treated activated carbons: Equilibria and kinetics, Chemical Engineering Journal, Vol: 379, Pages: 1-11, ISSN: 1385-8947
Activated carbons (ACs) show great potential for selective adsorption removal of sulfur (SARS) from hydrocarbon fuels but require improvements in uptake and selectivity. Moreover, systematic equilibria and kinetic analyses of ACs for desulfurization are still lacking. This work examines the influence of modifying a commercial-grade activated carbon (AC) by CO2 and steam treatment for the selective adsorption removal of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) at 323 K. An untreated AC and a charcoal Norit carbon (CN) were used for comparative purposes. Physicochemical characterization of the samples was carried out by combining N2-physisorption, X-ray diffractometry, microscopy, thermogravimetric and infrared analyses. The steam and CO2 treated ACs exhibited higher sulfur uptakes than the untreated AC and CN samples. The steam treated AC appears to be especially effective to remove sulfur, showing a remarkable sulfur uptake (~24 mgS·gads−1 from a mixture of 1500 ppmw of DBT and 1500 ppm 4,6-DMDBT) due to an increased surface area and microporosity. The modified ACs showed similar capacities for both DBT and the sterically hindered 4,6-DMDBT molecules. In addition, they were found to be selective in the presence of sulfur-free aromatics and showed good multicycle stability. Compared to other adsorbents, the modified ACs exhibited relatively high adsorption capacities. The combination of batch and fixed bed measurements revealed that the adsorption sites of the samples are characterized as heterogeneous due to the better fit to the Freundlich isotherm. The kinetic breakthrough profiles were described by the linear driving force (LDF) model.
Thaore VB, Armstrong RD, Hutchings GJ, et al., 2020, Sustainable production of glucaric acid from corn stover via glucose oxidation: An assessment of homogeneous and heterogeneous catalytic oxidation production routes, Chemical Engineering Research and Design, Vol: 153, Pages: 337-349, ISSN: 0263-8762
Glucaric acid is being used increasingly as a food additive, corrosion inhibitor, in deicing, and in detergents, and is also a potential starting material for the production of adipic acid, the key monomer for nylon-66. This work describes a techno-economic analysis of a potential bio-based process for the production of pure glucaric acid from corn stover (biomass). Two alternative routes for oxidation of glucose to glucaric acid are considered: via heterogeneous catalytic oxidation with air, and by homogeneous glucose oxidation using nitric acid. Techno-economic and lifecycle assessments (TEA, LCA) are made for both oxidation routes and cover the entire process from biomass to pure crystalline glucaric acid that can be used as a starting material for the production of valuable chemicals. This is the first TEA of pure glucaric acid production incorporating ion exchange and azeotropic evaporation below 50 °C to avoid lactone formation. The developed process models were simulated in Aspen Plus V9. The techno-economic assessment shows that both production routes are economically viable leading to minimum selling prices of glucaric acid of ∼$2.53/kg and ∼$2.91/kg for the heterogeneous catalytic route and the homogeneous glucose oxidation route respectively. It is shown that the heterogeneous catalytic oxidation route is capable of achieving a 22% lower environmental impact than the homogeneous glucose oxidation route. Opportunities for further improvement in sustainable glucaric acid production at industrial scale are identified and discussed.
Bernardi A, Chen Y, Chadwick D, et al., 2020, Direct DME Synthesis from Syngas: a Technoeconomic Model-based Investigation, Editors: Pierucci, Manenti, Bozzano, Manca, Publisher: ELSEVIER SCIENCE BV, Pages: 655-660
Narvaez A, Chadwick D, Kershenbaum L, 2019, Performance of small-medium scale polygeneration systems for dimethyl ether and power production, Energy, Vol: 188, Pages: 116058-116058, ISSN: 0360-5442
Khawaji M, Zhang Y, Loh M, et al., 2019, Composition dependent selectivity of bimetallic Au-Pd NPs immobilised on titanate nanotubes in catalytic oxidation of glucose, Applied Catalysis B: Environmental, Vol: 256, ISSN: 0926-3373
The catalytic performance of Au-Pd nanoparticles (NP) prepared by colloidal synthesis and immobilised on titanate nanotubes(Ti-NT) in the selective oxidation of glucose to gluconic and glucaric acids has been studied under initially basic and relativelymild conditions. Catalysts with varying compositions displayed quite different product selectivity especially in relation to deeperoxidation. The yield of glucaric acid was found to be proportional to the atomic content of Au in the Au-Pd NPs: Au/Ti-NTexhibited the highest selectivity to glucaric acid, while Au15Pd85/Ti-NT displayed the highest selectivity to gluconic acid, SGLO >98%. Catalyst recycling revealed deactivation, which appears to be due to a combination of metal leaching, particle size changesand product adsorption, and is associated with the gradual fall in pH of the reaction mixture. Results suggest that the leached Auspecies play a significant role in the oxidation of gluconic to glucaric acid.
Khawaji M, Chadwick D, 2019, Selective oxidation using Au-Pd catalysts: Role of the support in the stabilization of colloidal Au-Pd NPs, Catalysis Today, ISSN: 0920-5861
Khawaji M, Zhang Y, Graca I, et al., 2019, Selective oxidation of glucose using Au-Pd NPs NPs immobilized on nanostructured ceria and titania: Influence of bimetallic composition and support morphology, ACS Fall National Meeting and Exposition, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Khawaji M, Chadwick D, 2019, Selective catalytic oxidation over Au-Pd/titanate nanotubes and the influence of the catalyst preparation method on the activity, Catalysis Today, Vol: 334, Pages: 122-130, ISSN: 0920-5861
The dependence of the selective oxidation catalytic activity of Au-Pd supported on titanate nanotubes on the catalyst preparation method has been investigated. The most active Au-Pd/Ti-NT catalyst for the selective oxidation of benzyl alcohol is shown to be that prepared using colloidal synthesis and immobilization with PVA as a stabilizer, which has markedly superior catalytic activity compared to catalysts prepared by deposition-precipitation, adsorption, and dry impregnation methods. Au-Pd NPs stabilized by graphene oxide sheets and immobilized on Ti-NT has also been studied and while not optimum shows promising catalytic activity. The superior catalytic activity of the catalysts prepared by colloidal synthesis is attributed to the high metal dispersion on the external surfaces of Ti-NT, the narrow particle size distribution, and the high degree of Au-Pd alloying. This work also demonstrates that in the adsorption method of preparation using HAuCl4.3H2O and PdCl2 precursors, the uptake of Pd ions in solution by Ti-NT is proportional to the sodium content in Ti-NT, which implies that Na is involved in an ion-exchange reaction with Pd ions.
Bernardi A, Gomoescu L, Wang J, et al., 2019, Kinetic Model Discrimination for Methanol and DME Synthesis using Bayesian Estimation, 12th International-Federation-of-Automatic-Control (IFAC) Symposium on Dynamics and Control of Process Systems including Biosystems (DYCOPS), Publisher: ELSEVIER SCIENCE BV, Pages: 335-340, ISSN: 2405-8963
Antunes MM, Lima S, Fernandes A, et al., 2019, One-pot hydrogen production and cascade reaction of furfural to bioproducts over bimetallic Pd-Ni TUD-1 type mesoporous catalysts (vol 237, pg 521, 2018), APPLIED CATALYSIS B-ENVIRONMENTAL, Vol: 243, Pages: 801-801, ISSN: 0926-3373
Antunes MM, Lima S, Fernandes A, et al., 2018, One-pot hydrogen production and cascade reaction of furfural to bioproducts over bimetallic Pd-Ni TUD-1 type mesoporous catalysts, APPLIED CATALYSIS B-ENVIRONMENTAL, Vol: 237, Pages: 521-537, ISSN: 0926-3373
Graça I, Al-Shihri S, Chadwick D, 2018, Selective oxidation of cyclohexane: Ce promotion of nanostructured manganese tungstate, Applied Catalysis A: General, Vol: 568, Pages: 95-104, ISSN: 0926-860X
Cyclohexane selective oxidation over nanostructured MnWO4promoted with increasing amounts of Ce (1–5 wt%) has been investigated at mild conditions using molecular oxygen as oxidant. MnWO4nanorods were found to be an active catalyst for cyclohexane selective oxidation with selectivity to KA oil (cyclohexanol + cyclohexanone) of approximately 85%. The catalytic performance was improved by impregnation with 1 wt% Ce while the textural properties and crystallinity were preserved and Ce was well-dispersed on the surface. XPS analysis of 1%Ce-MnWO4showed Ce to be present mainly as Ce3+, which is known to promote oxygen adsorption, activation, and mobility. At higher Ce content, the proportion of Ce4+increased to be the main Ce species and large, heterogeneously-dispersed Ce oxide particles are formed on the catalyst surface. The lower Ce3+content reduces the promoting effect while the large Ce oxide particles block access to the active sites on the surface of the MnWO4nanorod. MnWO4and 1%Ce-MnWO4nanorods were shown to retain their selective oxidation performance in consecutive reaction runs. Surprisingly, physical mixtures of nanostructured MnWO4and a CeO2nanopowder showed enhanced selective oxidation activity compared to MnWO4alone reaching a plateau at 25–50 wt% CeO2, whereas CeO2nanopowder itself was found to be inactive at the reaction conditions. Ce promoted MnWO4shows promise as a catalyst for selective oxidation of cyclohexane and performs at least as well as the most active non-metallic heterogeneous catalysts reported in the literature.
Iruretagoyena Ferrer D, Sunny N, Chadwick D, et al., 2018, Towards a low carbon economy via sorption enhanced water gas shift and alcohol reforming
Thaore VB, Chadwick D, Shah N, 2018, Sustainable production of chemical intermediates for nylon manufacture: a techno-economic analysis for renewable production of caprolactone, Chemical Engineering Research and Design, Vol: 135, Pages: 140-152, ISSN: 1744-3598
Caprolactone is a precursor for the synthesis of caprolactam, the key monomer for nylon-6 which is produced globally at a scale of 4 million tonnes per annum. This work describes and assesses a bio-based production route to caprolactone from an agricultural residue, specifically corn stover, via glucose, fructose, 5-hydroxymethyl furfural (HMF) and 1,6-hexanediol. The material and energy balances, the cost efficiency, as well as on the potential reduction of greenhouse gas (GHG) emissions are reported and discussed. The developed process model was simulated in Aspen Plus™ with the optimization and energy integration performed for the entire process from corn stover to caprolactone. A sensitivity analysis was performed with consideration of various economic factors to explore the process economics. The results of the techno-economic and environmental assessment show that a bio-based caprolactone production process via glucose and HMF could be competitive with conventional hydrocarbon-based processes when major by-products are valorised and has a lower environmental impact. Areas where further investigation is needed to improve sustainable caprolactone production are identified and discussed.
Khawaji M, Chadwick D, 2018, Au–Pd NPs immobilised on nanostructured ceriaand titania: impact of support morphology on the catalytic activity for selective oxidation, Catalysis Science and Technology, Vol: 8, Pages: 2529-2539, ISSN: 2044-4753
Bimetallic Au–Pd nanoparticles supported on different ceria and titania nanostructures have been prepared by sol-immobilisation, and evaluated in the solvent-less selective oxidation of benzyl alcohol. The catalysts were characterised by TEM, STEM, XRD, XPS, ICP-AES, and nitrogen adsorption–desorption measurements. The activity of the catalysts was found to be strongly related to the morphology, structure and physiochemical properties of the supports. Au–Pd/ceria nanorods exhibited remarkably high catalytic activity (TOF > 35 900 h−1), and was found to be considerably more active than Au–Pd/titanate nanotubes, and Au–Pd catalysts supported on conventional ceria and titania nanopowders. The outstanding catalytic performance of Au–Pd/ceria nanorods is attributed to the unique surface chemistry of ceria nanorods, and the ability of catalyst preparation method (i.e. sol-immobilisation) to control the metal particle size and the bimetallic alloy formation. The presence of surface defects and high concentration of oxygen vacancies and Ce3+ in ceria nanorods is likely responsible for the stabilisation of Au–Pd NPs during sol-immobilisation, which led to a very small mean particle size (2.1 nm) corresponding to a dispersion of approximately 52%, and a high surface metal concentration.
Iruretagoyena Ferrer D, Hellgardt K, Chadwick D, 2018, Towards autothermal hydrogen production by sorption-enhanced water gas shift and methanol reforming: a thermodynamic analysis, International Journal of Hydrogen Energy, Vol: 43, Pages: 4211-4222, ISSN: 0360-3199
Hydrogen production by the water gas shift reaction (WGS) is equilibrium limited. In the current study, we demonstrate that the overall efficiency of the WGS can be improved by co-feeding methanol and removing CO2 in situ. The thermodynamics of the water gas shift and methanol reforming/WGS (methanol-to-shift, MtoS) reactions for H2 production alone and with simultaneous CO2 adsorption (sorption-enhanced, SEWGS and SEMtoS) were studied using a non-stoichiometric approach based on the minimisation of the Gibbs free energy. A typical composition of the effluent from a steam methane reformer was used for the shift section. The effects of temperature (450–750 K), pressure (5–30 barg), steam and methanol addition, fraction of CO2 adsorption (0–95%) and energy efficiency of the shift systems have been investigated. Adding methanol to the feed facilitates autothermal operation of the shift unit, with and without CO2 removal, and enhances significantly the amount of H2 produced. For a set methanol and CO input, the MtoS and SEMtoS systems show a maximum productivity of H2 between 523 and 593 K due to the increasing limitation of the exothermic shift reaction while the endothermic methanol steam reforming is no longer limited above 593 K. The heat of adsorption of CO2 was found to make only a small difference to the H2 production or the autothermal conditions.
Shin SB, Chadwick D, 2018, Comparison of a monolith and a confined Taylor flow (CTF) reactor for propene epoxidation, Chemical Engineering and Processing: Process Intensification, Vol: 125, Pages: 173-182, ISSN: 0255-2701
Heterogeneous catalytic epoxidation of propene to propene oxide with hydrogen peroxide was investigated in a monolith and a confined Taylor flow (CTF) reactor in which titanium silicalite (TS-1) catalyst was coated on the walls. The influence of gas and liquid superficial velocity on the hydrodynamic characteristics of the monolith and CTF reactor was also investigated under Taylor flow regime at atmospheric and high pressure. The reactors showed distinctly different hydrodynamic properties which in turn led to different performance for propene epoxidation. The production rate of propene oxide was higher in the monolith reactor due to its larger catalyst coating area, larger mass-transfer surface area and more frequent recycling of liquid flow. A variation of reactor column structures confirmed that the propene oxide production was highly dependent on the catalyst coating area and cross-sectional area of the reactor column. High operating pressure made a significant impact on the length of Taylor bubbles and the propene oxide production rate was found to increase in proportion to the operating pressure.
Peng J, Iruretagoyena Ferrer D, Chadwick D, 2017, Hydrotalcite/SBA15 composites for pre-combustion CO2 capture: CO2, Journal of Co2 Utilization, Vol: 24, Pages: 73-80, ISSN: 2212-9820
Hydrotalcite-like compounds (HT) show potential as CO2 adsorbent materials for pre-combustion CO2 capture applications, but require improvements in stability, adsorption capacity and kinetics. In this study, HT/SBA15 hybrids (with different Mg/Al ratios varying from 0.3 to 3) have been synthesised using a two-stage grafting method to coat a mesoporous SBA15 with hydrotalcite layers. The HT/SBA15 hybrids showed significant improvement in intrinsic CO2 uptake (per mass of HT), initial uptake rate, and multicycle stability compared to unsupported HT. Compared to previously reported nanostructured carbon supports (e.g. CNF, MWCNTs), the HT/SBA15 hybrids were found to be more thermally stable and exhibit comparable adsorption uptake and rates. In particular, the use of SBA15 as a support is shown to prevent the gradual loss in weight from thermal decomposition observed for HT/MWCNT or HT/GO composites over extended cycling.
Khawaji M, Chadwick D, 2017, Au-Pd bimetallic nanoparticles immobilised on titanate nanotubes: a highly active catalyst for selective oxidation, ChemCatChem, Vol: 9, Pages: 4353-4363, ISSN: 1867-3880
In this work, a highly active Au-Pd/Ti-NT catalyst has been produced by using colloidal synthesis and immobilisation on essentially sodium-free Ti-nanotubes (NTs). The new catalyst has markedly superior catalytic activity (turnover frequency>19 000 h−1) for the selective oxidation of benzyl alcohol compared with similar catalysts reported in the literature, and to Au-Pd catalysts supported on Ti-NTs prepared by adsorption, as well as conventional Au-Pd/TiO2 prepared by impregnation. The superior catalytic activity of the catalyst is shown to be a result of the high metal dispersion on the external surfaces of Ti-NTs, the narrow particle size distribution and the consistent formation of Au-Pd mixed alloy nanoparticles in close to a 1:1 weight ratio. In repeated use, the Au-Pd/Ti-NT catalyst showed only a modest fall in activity, which is shown by FTIR to be associated mainly with the irreversible adsorption of benzoic acid and benzyl benzoate by the catalyst.
Biscaya Semedo Pereira Da Graca IS, Bacariza MC, Fernandes A, et al., 2017, Desilicated NaY zeolites impregnated with magnesium as catalysts for glucose isomerisation into fructose, Applied Catalysis B: Environmental, Vol: 224, Pages: 660-670, ISSN: 0926-3373
The impact of desilication on the performance of a series of alkali-treated NaY zeolites impregnated with 5 wt.% of magnesium for glucose isomerisation into fructose has been studied. Desilication at different NaOH concentrations increases the mesoporous volume and external surface area, without compromising microporosity and crystallinity. The observed reduction of the microporous volume due to magnesium impregnation was found to decrease for the alkali-treated zeolites. Higher density and strength of basic sites and stronger magnesium-support interaction were also achieved with the treatment. These improved properties resulted in a significant increase of both glucose conversion and fructose yield on the magnesium-doped desilicated zeolites. Glucose conversion continuously increases with desilication (28–51%), whereas fructose yield passes through a maximum (35%) at low desilication levels. Among the prepared desilicated samples, low-severity alkali-treated zeolites also show lower deactivation in consecutive reaction runs, as well as superior regeneration behaviour. Thus, hierarchical NaY zeolites impregnated with magnesium could be favourably used for glucose isomerisation into fructose if suitable alkaline treatment conditions are selected, with low-severity treated NaY zeolites being the best choice. Higher fructose productivities were achieved for the low-severity desilicated zeolites than for higher magnesium content NaY zeolites reported previously, leading to a lower Mg requirement.
Antunes MM, Lima S, Fernandes A, et al., 2017, MFI Acid Catalysts with Different Crystal Sizes and Porosity for the Conversion of Furanic Compounds in Alcohol Media, CHEMCATCHEM, Vol: 9, Pages: 2747-2759, ISSN: 1867-3880
Graça I, Bacariza MC, Chadwick D, 2017, Glucose isomerisation into fructose over Mg-impregnated Na-zeolites: Influence of zeolite structure, Microporous and Mesoporous Materials, Vol: 255, Pages: 130-139, ISSN: 1387-1811
Magnesium-impregnated NaY, NaMOR, NaBEA, NaZSM-5 and NaFER zeolites have been prepared and investigated for glucose isomerisation into fructose. It was shown that better magnesium dispersion and smaller reduction of textural properties were obtained with three-dimensional rather than with mono- and two-dimensional zeolites. MgO particle size was also observed to be dependent on the zeolite structure. Various contributions were found to affect the final catalyst performances: availability of MgO, the strength of basic sites, location where the reaction takes place, and the extent of homogeneous reaction due to Na and Mg leaching. Higher glucose conversions were achieved over the MOR, BEA and ZSM-5 zeolites (37–39%), while Y and FER zeolites presented a relatively moderate performance (28 and 27%). In general, lower fructose selectivities were reached for the most active samples, except for the ZSM-5 zeolite. For this catalyst, the reaction appeared to take place mostly on the external surface due to the smaller pore size. Among the various structures investigated, 5%MgNaY zeolite revealed the most resistance to MgO particle size agglomeration during consecutive reaction runs. In addition, 5%MgNaY was found to be the only catalyst capable of recovering its initial activity when regenerated at high temperature. Thus, the type of zeolite structure selected as support for MgO appears to have a significant effect on the catalyst performance for the glucose isomerisation into fructose, with Y zeolite being the most attractive choice for this application.
Thaore V, Graca I, Chadwick D, et al., 2017, Renewable production routes for Nylon-6 precursor: techno-economic analysis for caprolactam, Bio-resources: feeding a sustainable chemical industry: Faraday Discussion
Caprolactam, the intermediate chemical used for the synthesis of Nylon-6 polymer, is produced globally in large quantities, approximately 4.4106 ton per annum, mainly using petroleum-derived feedstocks. These traditional caprolactam production processes are responsible for important N2O, CO2, SO2 and NMVOCs emissions, the largest contributor being N2O with ~10-15 MtCO2 eq/yr. In recent years. Lignocellulosic biomass (LBM) has been considered as an ideal starting material for commercial application owing to its high content of polysaccharides. Approximately 140 billion ton/yr of LBM is available, including plant residues and agricultural waste. Thus, the production of caprolactam from biomass has become desirable due to the depletion of fossil hydrocarbons and to reduce greenhouse gas (GHG) emissions. In this study, a renewable production route for caprolactam was investigated using corn stover biomass, an agricultural residue, as the main feedstock. The process involves the conversion of C6 sugar obtained from biomass into 5-hydoxymethylfurfural (HMF), which is further used for the synthesis of caprolactam1. In the process design model, it was considered that first the corn stover is hydrolysed into sugar by acid hydrolysis, then its enzymatic saccharification and isomerisation to HMF takes place, and finally HMF is converted into caprolactone by a two-step catalytic hydrogenation. The simulation of the overall process comprising production and separation steps was performed in ASPEN plus. This demonstrated that provided major by-products are valorised, the investigated bio-based caprolactam production process could be competitive when compared to the traditional production route, in terms of economy and environmental impact factors, such as water resources and GHG emissions. The production of HMF from sugars is identified as an important intermediate step for further improvement of the process. In this respect, efficient glucose isomerisation to fructose is essent
Martins Lima S, Klaus Hellgardt KH, David Chadwick DC, 2017, Towards sustainable hydrogenation of 5-(hydroxymethyl)furfural: a two-stage continuous process in aqueous media over Raney catalysts, RSC Advances, Vol: 7, Pages: 31401-31407, ISSN: 2046-2069
The hydrogenation of 5-(hydroxymethyl)furfural (HMF) to 2,5-bis(hydroxymethyl)tetrahydrofuran (DHMTHF) in aqueous media under relatively mild reaction conditions has been investigated over heterogeneous RANEY® Cu and Ni catalysts using a continuous-flow hydrogenation reactor. These RANEY® catalysts were selected following a screening of several catalysts including precious metals supported on carbon for the hydrogenation of HMF. A single-stage versus a two-stage process for the hydrogenation of HMF into DHMTHF, i.e. via 2,5-dihydroxymethylfuran (DHMF) has been evaluated. The best result with an average selectivity of 98% for DHMTHF was obtained using a two-stage process; RANEY® Cu was used as a catalyst for the highly selective hydrogenation of HMF to DHMF (92 mol%) in the first stage and this product was used without further purification for in a second-stage selective hydrogenation of DHMF into DHMTHF using RANEY® Ni as a catalyst. The influence of the HMF concentration in the feeding solution (1–3 wt%), flow rate (0.05–0.25 mL min−1) and total pressure (20–90 bar) were investigated for the first-stage hydrogenation of HMF into DHMF over RANEY® Cu. HMF was found to exert an inhibiting effect on the conversion due to strong adsorption. The RANEY® Ni catalyst used in the second stage gradually deactivated. A procedure for in situ regeneration of the partially deactivated RANEY® Ni catalyst using acetic acid washing was investigated with limited success.
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