187 results found
Patzschke CF, Parkinson B, Willis JJ, et al., 2021, Co-Mn catalysts for H<inf>2</inf> production via methane pyrolysis in molten salts, Chemical Engineering Journal, Vol: 414, ISSN: 1385-8947
© 2021 Elsevier B.V. A promising production route for near CO2-free H2 from natural gas is methane pyrolysis in molten salts. During a screening of catalysts (containing La, Ni, Co and Mn) as particle suspensions in molten NaBr-KBr at 850 °C – 1000 °C, mixed Co-Mn catalysts were identified as being highly promising owing to their stability at pyrolysis conditions and fast kinetics. The catalysts, which contained Co-Mn nanocrystals (~8–9 ± 1 nm) that were prepared by colloidal chemistry were further tested in-depth, and their performance with varying molar Co:Mn ratios, particle sizes and temperatures were examined. The increase of the molar Co:Mn ratio from zero to two increased the CH4 conversion at 1000 °C from 4.8% to 10.4% for the smallest catalyst size range. Furthermore, we observed for all tested Co-Mn catalysts a stable performance over ca. 24 h of methane pyrolysis at 1000 °C and product selectivities for H2 near unity. While the Co-lean particles coked, the surface of the Co-rich particles remained largely carbon-free, and an increase in the Co-content was found to inhibit interactions between the support and the active phase (e.g. inhibited CoAl2O4 and MnAl2O4 formation). The rigorous procedure for the catalyst testing presented in this work enables the field to further investigate the use of catalysts for this process, and the insights gained from experiments with particle suspensions can be applied to the design of structured packings for an industrial-scale process.
Agbede OO, Kelsall GH, Hellgardt K, 2021, A novel molten tin reformer: Kinetics of oxygen dissolution in molten tin, CHEMICAL ENGINEERING SCIENCE, Vol: 231, ISSN: 0009-2509
Wichmann J, Lauersen KJ, Biondi N, et al., 2021, Engineering Biocatalytic Solar Fuel Production: The PHOTOFUEL Consortium., Trends Biotechnol
The EU Horizon2020 consortium PHOTOFUEL joined academic and industrial partners from biology, chemistry, engineering, engine design, and lifecycle assessment, making tremendous progress towards engine-ready fuels from CO2 via engineered photosynthetic microbes. Technical, environmental, economic, and societal opportunities and challenges were explored to frame future technology realization at scale.
Parkinson B, Patzschke CF, Nikolis D, et al., 2021, Methane pyrolysis in monovalent alkali halide salts: Kinetics and pyrolytic carbon properties, International Journal of Hydrogen Energy, Vol: 46, Pages: 6225-6238, ISSN: 0360-3199
© 2020 Hydrogen Energy Publications LLC Methane pyrolysis in molten salts has the potential to provide low-cost, low-CO2 emission H2 on an industrial scale. The alkali halides (NaBr, KBr, KCl, NaCl, (Na,K)Br) are inexpensive and environmental benign salts, which may facilitate sequestration or sales of the produced carbon even if low-to-moderate amounts of salt remain trapped in the carbon. In this novel work, alkali halides have been tested as the liquid reaction media, and the results of kinetic measurements and carbon characterisation are reported. The observed activation energies were found to be in the range 223.5–277.6 kJ mol−1, which is significantly lower than those measured during gas-phase methane pyrolysis (~422 kJ mol−1). After washing procedures with deionised water, the purity of the produced carbon was in the range 91.7–97.4 atom% or 55.0–91.6 wt%, with the carbon purities correlating well with the salt compounds size and salt-carbon wettability. The carbon samples generated in each salt are all low density (<1 g cm−3), highly porous (30.1–75.2%), low surface area (1.84–3.14 m2 g−1) and have relatively low-levels of structural order. The suggested relationships between the salt selection and the carbon purity, the mass fraction and degree of well-ordered carbon as well as surface and pore morphologies can be used to optimise process designs. Furthermore, the relationships could be used to tune the carbon properties to tailor it to the carbon market needs if the carbon is considered as a co-product.
Yusuf M, Farooqi AS, Keong LK, et al., 2021, Contemporary trends in composite Ni-based catalysts for CO2 reforming of methane, CHEMICAL ENGINEERING SCIENCE, Vol: 229, ISSN: 0009-2509
Al-Qahtani A, Parkinson B, Hellgardt K, et al., 2021, Uncovering the true cost of hydrogen production routes using life cycle monetisation, Applied Energy, Vol: 281, Pages: 115958-115958, ISSN: 0306-2619
Hydrogen has been identified as a potential energy vector to decarbonise the transport and chemical sectors and achieve global greenhouse gas reduction targets. Despite ongoing efforts, hydrogen technologies are often assessed focusing on their global warming potential while overlooking other impacts, or at most including additional metrics that are not easily interpretable. Herein, a wide range of alternative technologies have been assessed to determine the total cost of hydrogen production by coupling life-cycle assessments with an economic evaluation of the environmental externalities of production. By including monetised values of environmental impacts on human health, ecosystem quality, and resources on top of the levelised cost of hydrogen production, an estimation of the “real” total cost of hydrogen was obtained to transparently rank the alternative technologies. The study herein covers steam methane reforming (SMR), coal and biomass gasification, methane pyrolysis, and electrolysis from renewable and nuclear technologies. Monetised externalities are found to represent a significant percentage of the total cost, ultimately altering the standard ranking of technologies. SMR coupled with carbon capture and storage emerges as the cheapest option, followed by methane pyrolysis, and water electrolysis from wind and nuclear. The obtained results identify the “real” ranges for the cost of hydrogen compared to SMR (business as usual) by including environmental externalities, thereby helping to pinpoint critical barriers for emerging and competing technologies to SMR.
Daud ARM, Berrueco C, Hellgardt K, et al., 2021, Oxidative cracking of three to five-member ring polycyclic aromatic hydrocarbons in subcritical and supercritical water, The Journal of Supercritical Fluids, Vol: 167, Pages: 105050-105050, ISSN: 0896-8446
Polycyclic aromatic hydrocarbons (PAH) are refractory structures common in heavy hydrocarbons. Thermal cracking in supercritical water (SCW) is limited but PAH can be completely oxidised if an oxidant is added. By restricting oxidant supply to substoichiometric amounts, this study aims to achieve partial oxidation as a route to useful chemicals, such as mono- and bi-aromatics. Oxidative cracking reactions of anthracene, pyrene and benzo[a]pyrene in subcritical and SCW were studied. PAH conversions well above 90 % were achieved along a fast heating ramp in a batch reactor. This quick initial oxidation took place predominantly in inner rings, weakening the aromatic structure and increasing cracking reactivity. This oxidation-cracking pathway became dominant in the SCW region, producing mostly oxygenated compounds with fewer aromatic rings. On the other hand, competing reactions leading to polymerization were favoured in the subcritical water region. PAH reactivity was found to follow the order anthracene > benzo[a]pyrene > pyrene.
Yusuf M, Farooqi AS, Keong LK, et al., 2020, Latest trends in Syngas production employing compound catalysts for methane dry reforming, ISSN: 1757-8981
© 2020 Institute of Physics Publishing. All rights reserved. The rise in the global population has ultimately steered to increase in global energy consumptions. This masqueraded several challenges worldwide. The most troublesome being the accumulation of greenhouse gases (GHGs) that induced a global climatic change. The utilization of fossil fuels like petroleum, coal and natural gas on the copious scale has led to the elevated levels of carbon dioxide (CO2) and methane (CH4) in the global environment. Dry reforming of methane (DRM) is a highly favorable technique as it utilizes two of the prominent GHGs, CH4 and CO2 to generate a useful and valuable product viz. syngas. However, the deactivation, coking and sintering of catalysts are still the main hurdles in the commercialization of the process. The compound metal catalysts have shown enhanced activity and prolonged durability when compared with monometallic catalysts due to enhanced morphology, improved and stable catalytic structure, i.e., both coke and sintering resistant at high temperatures. This brief review spotlights the recent developments in DRM by emphasizing parameters such as the effects of catalyst support, bimetallic catalyst, promoters and strong metal-support interaction (SMSI) in the last decade.
Agbede OO, Kelsall GH, Hellgardt K, 2020, A solid oxide fuel cell with molten tin anode for electricity generation and methane reforming, JOURNAL OF POWER SOURCES, Vol: 474, ISSN: 0378-7753
Chadha D, Kogelbauer A, Campbell J, et al., 2020, Are the kids alright? Exploring students’ experiences of support mechanisms to enhance wellbeing on an engineering programme in the UK, European Journal of Engineering Education, Pages: 1-16, ISSN: 0304-3797
In this paper, we aim to explore students’ experiences of support mechanisms that support their wellbeing on an engineering degree programme at a research-intensive higher education institution and understand how theory relates to practice. This study was conducted using a mixed-methods approach involving student survey responses (N = 173), interviews with 16 students and focus groups. Kahu and Nelson’s conceptual framework was used as a lens through which to explore student support mechanisms. Preliminary data analysis indicates that the intense workload adversely affects students as do some of the interactions they have with personal tutors and their peers. Our findings suggest that workload needs to be reduced, personal tutors need to fill gaps in their skills set, especially associated with student support, and institutional and departmental protocols be continually updated to support student wellbeing. Additionally, student wellbeing officers and professional, dedicated wellbeing advisors could be part of a long-term solution.
Ibadurrohman M, Hellgardt K, 2020, Importance of surface roughness of TiO<inf>2</inf> photoanodes in promoting photoelectrochemical activities with and without sacrificial agent, Thin Solid Films, Vol: 705, ISSN: 0040-6090
© 2020 Elsevier B.V. This paper is intended to highlight the importance of surface roughness of TiO2 photoanodes in a photoelectrochemical (PEC) cell with and without sacrificial agents. TiO2 films were synthesized via a spray pyrolysis method in the presence of PEG200 as a surface-roughening agent. The rough-surface photoanode led to excellent photo-voltammetric output by doubling the limiting photocurrent of its smooth-surface counterpart (from 0.11 mA/cm2 to 0.23 mA/cm2 at 0.8 V vs HgO|Hg). The function of glycerol as an anodic sacrificial agent is also exploited more effectively in the use of rough-surface TiO2. When the smooth-surface TiO2 is used, the presence of glycerol promotes additional photocurrent densities of as low as 0.037 mA/cm2 and 0.043 mA/cm2 at −0.7 V vs HgO|Hg and at 0.8 V vs HgO|Hg, respectively. At the same respective potentials, the use of rough-surface TiO2 gives rise to remarkably higher additional photocurrent density of 0.16 mA/cm2 and 0.11 mA/cm2 – favoring less anodic potential, that is. Hence, we conclude that surface roughening of the photoanode is an effective, albeit simple, strategy to significantly improve PEC responses and make the most use of anodic sacrificial agents.
Agbede OO, Hellgardt K, Kelsall GH, 2020, Electrical conductivities and microstructures of LSM, LSM-YSZ and LSM-YSZ/LSM cathodes fabricated on YSZ electrolyte hollow fibres by dip-coating, MATERIALS TODAY CHEMISTRY, Vol: 16, ISSN: 2468-5194
Feng Y, Morgan M, Fraser PD, et al., 2020, Crystal structure of geranylgeranyl pyrophosphate synthase (CrtE) involved in cyanobacterial terpenoid biosynthesis, Frontiers in Plant Science, Vol: 11, ISSN: 1664-462X
Cyanobacteria are photosynthetic prokaryotes that perform oxygenic photosynthesis. Due to their ability to use the photon energy of sunlight to fix carbon dioxide into biomass, cyanobacteria are promising hosts for the sustainable production of terpenoids, also known as isoprenoids, a diverse class of natural products with potential as advanced biofuels and high-value chemicals. However, the cyanobacterial enzymes involved in the biosynthesis of the terpene precursors needed to make more complicated terpenoids are poorly characterized. Here we show that the predicted type II prenyltransferase CrtE encoded by the model cyanobacterium Synechococcus sp. PCC 7002 is homodimeric and able to synthesize C20-geranylgeranyl pyrophosphate (GGPP) from C5-isopentenyl pyrophosphate (IPP) and C5-dimethylallyl pyrophosphate (DMAPP). The crystal structure of CrtE solved to a resolution of 2.7 Å revealed a strong structural similarity to the large subunit of the heterodimeric geranylgeranyl pyrophosphate synthase 1 from Arabidopsis thaliana with each subunit containing 14 helices. Using mutagenesis, we confirmed that the fourth and fifth amino acids (Met-87 and Ser-88) before the first conserved aspartate-rich motif (FARM) play important roles in controlling chain elongation. While the WT enzyme specifically produced GGPP, variants M87F and S88Y could only generate C15-farnesyl pyrophosphate (FPP), indicating that residues with large side chains obstruct product elongation. In contrast, replacement of M87 with the smaller Ala residue allowed the formation of the longer C25-geranylfarnesyl pyrophosphate (GFPP) product. Overall, our results provide new structural and functional information on the cyanobacterial CrtE enzyme that could lead to the development of improved cyanobacterial platforms for terpenoid production.
Sun Z, Parkinson B, Agbede OO, et al., 2020, Noninvasive Differential Pressure Technique for Bubble Characterization in High-Temperature Opaque Systems, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 59, Pages: 6236-6246, ISSN: 0888-5885
Zhu K, Bos R, Hellgardt K, 2020, Activation of catalysts in commercial scale fixed-bed reactors: Dynamic modelling and guidelines for avoiding undesired temperature excursions, CHEMICAL ENGINEERING JOURNAL, Vol: 382, ISSN: 1385-8947
Kalogeropoulos N, Walker P, Hale C, et al., 2020, Facilitating Independent Learning: Student Perspectives on the Value of Student-Led Maker Spaces in Engineering Education, INTERNATIONAL JOURNAL OF ENGINEERING EDUCATION, Vol: 36, Pages: 1220-1233, ISSN: 0949-149X
Evans AD, Cummings MS, Luebke R, et al., 2019, Screening metal–organic frameworks for dynamic CO/N2 separation using complementary adsorption measurement techniques, Industrial & Engineering Chemistry Research, Vol: 58, Pages: 18336-18344, ISSN: 0888-5885
Carbon monoxide (CO)/nitrogen (N2) separation is a particularly challenging separation, yet it is the one with great industrial relevance for its use in petrochemical synthesis. Although an expensive cryogenic step can be used to perform such separation, it remains ineffective in purifying CO from syngas streams with a significant N2 content. Taking advantage of the lower energy requirement of adsorption processes, we have explored the use of metal–organic frameworks (MOFs) as adsorbents for this difficult separation. We have screened a range of MOF candidates for CO/N2 separation covering a range of chemical and textural features, using the flux response technology to evaluate their dynamic performance for throughput testing alongside equilibrium uptake measurements. We have identified Ni-MOF-74 and Co-MOF-74 as the most promising candidates because of their high metal density and strong metal–CO interactions. We have investigated further the effect of N2 impurity concentrations upon CO/N2 separation using breakthrough adsorption testing and cyclic testing (up to 20 cycles). Overall, using multiple adsorption measurement techniques, this study demonstrates the CO/N2 dynamic separation performance of M-MOF-74 and its ability to be applied for an industrially relevant separation.
González-Garay A, Pozo C, Galán-Martín Á, et al., 2019, Assessing the performance of UK universities in the field of chemical engineering using data envelopment analysis, Education for Chemical Engineers, Vol: 29, Pages: 29-41, ISSN: 1749-7728
University rankings have become an important tool to compare academic institutions within and across countries. Yet, they rely on aggregated scores based on subjective weights which render them sensitive to experts’ preferences and not fully transparent to final users. To overcome this limitation, we apply Data Envelopment Analysis (DEA) to evaluate UK universities in the field of chemical engineering as a case study, using data retrieved from two national rankings. DEA is a non-parametric approach developed for the multi-criteria assessment of entities that avoids the use of subjective weightings and aggregated scores; this is accomplished by calculating an efficiency index, on the basis of which universities can be classified as either ‘efficient’ or ‘inefficient’. Our analysis shows that the Higher Education Institutions (HEI) occupying the highest positions in the chemical engineering rankings might not be the most efficient ones, and vice versa, which highlights the need to complement the use of rankings with other analytical tools. Overall, DEA provides further insight into the assessment of HEIs, allowing institutions to better understand their weaknesses and strengths, while pinpointing sources of inefficiencies where improvement efforts must be directed.
Kojo G, Wei X, Matsuzaki Y, et al., 2019, Fabrication and electrochemical performance of anode-supported solid oxide fuel cells based on proton-conducting lanthanum tungstate thin electrolyte, SOLID STATE IONICS, Vol: 337, Pages: 132-139, ISSN: 0167-2738
Ali H, Solsvik J, Wagner JL, et al., 2019, CFD and kinetic-based modeling to optimize the sparger design of a large-scale photobioreactor for scaling up of biofuel production, BIOTECHNOLOGY AND BIOENGINEERING, Vol: 116, Pages: 2200-2211, ISSN: 0006-3592
Maraj M, Hale CP, Kogelbauer A, et al., 2019, Teaming with confidence: How peer connections in problem-based learning impact the team and academic self-efficacies of engineering students
© American Society for Engineering Education, 2019. Engineers will routinely work in teams to solve complex problems. Team-working and collaboration are therefore an integral part of engineering education as they offer enhanced opportunities of acquiring both transferable and subject-specific skills. This paper examines the experiences of third-year engineering students studying a design-based module which uses problem-based learning (PBL) as the main pedagogical approach where students work in teams of 5 or 6 to achieve the associated learning outcomes. PBL allows students to not only play an active role in their own learning but also affords the added opportunity of learning with and from each other (peer learning). The success of this experience can however, be impacted by the team efficacy which exists or ensues as part of the process. These interactions can influence academic self-efficacy and a key aim of this paper is to use the students' perceptions of their experiences with PBL to examine the relationships which exist among academic self-efficacy, peer learning and team efficacy within the module. Findings show that a large percentage of students (85%) felt they learned from each other and that this collaborative experience strongly improved their understanding of mechanical design principles. Self-efficacy scales ranging from 0 (cannot do at all) to 100 (highly certain can do) showed that 65% of students rated their average academic self-efficacy across all learning outcomes as high (above 75). This efficacy was positively related to the support received from peers. Only 6% of respondents indicated that they would be confident undertaking the module by themselves and that while peer-to-peer interactions helped with sharing the workload and producing deliverables, they would have been able to successfully tackle the module alone had the time allotted been increased proportionally. This information is valuable as it can inform and direct future module d
Chadha D, Maraj M, Kogelbauer A, et al., 2019, Hearing you loud and clear: The student voice as a driver for curriculum change in a chemical engineering degree course (WIP), ASEE Annual Conference and Exposition 2019, Publisher: ASEE
A curriculum review can be an intricate and arduous process, made more complex due to a myriad of interwoven threads that inform the curriculum. This is often the case in chemical engineering due in part to the accommodation of employer expectations, requirements from accreditation bodies and the multidisciplinary, integrative nature of an engineering degree which depends on students acquiring a wide range of attributes, and which focuses on application and relevancy , . In this paper, we present our efforts to review the chemical engineering curricula at a research-intensive higher education institution (HEI)in the UK. This review is being orchestrated by institutional managers to ensure that programmes of study throughout the HEI better reflect student needs and expectations and adhere to a recently revised institutional teaching and learning strategy. This review is also driven by a recognition that the student body has changed with traditional modes of teaching seemingly outdated and ineffective. For example, it has previously been suggested that one of the greatest obstacles to overcome with respect to creating the right type of education for chemical engineers, does not arise from external drivers, but in recognising and responding to internal factors –amounting to fundamental pedagogical shifts in learner behaviour and expectation.
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
del Rio Chanona EA, Wagner JL, Ali H, et al., 2019, Deep learning-based surrogate modeling and optimization for microalgal biofuel production and photobioreactor design, AIChE Journal, Vol: 65, Pages: 915-923, ISSN: 0001-1541
Identifying optimal photobioreactor configurations and process operating conditions is critical to industrialize microalgae‐derived biorenewables. Traditionally, this was addressed by testing numerous design scenarios from integrated physical models coupling computational fluid dynamics and kinetic modeling. However, this approach presents computational intractability and numerical instabilities when simulating large‐scale systems, causing time‐intensive computing efforts and infeasibility in mathematical optimization. Therefore, we propose an innovative data‐driven surrogate modeling framework, which considerably reduces computing time from months to days by exploiting state‐of‐the‐art deep learning technology. The framework built upon a few simulated results from the physical model to learn the sophisticated hydrodynamic and biochemical kinetic mechanisms; then adopts a hybrid stochastic optimization algorithm to explore untested processes and find optimal solutions. Through verification, this framework was demonstrated to have comparable accuracy to the physical model. Moreover, multi‐objective optimization was incorporated to generate a Pareto‐frontier for decision‐making, advancing its applications in complex biosystems modeling and optimization.
Holmes-Gentle I, Bedoya-Lora F, Alhersh F, et al., 2019, Optical Losses at Gas Evolving Photoelectrodes: Implications for Photoelectrochemical Water Splitting, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 123, Pages: 17-28, ISSN: 1932-7447
Parkinson B, Balcombe P, Speirs JF, et al., 2019, Levelized cost of CO2 mitigation from hydrogen production routes, Energy and Environmental Science, Vol: 12, Pages: 19-40, ISSN: 1754-5692
Different technologies produce hydrogen with varying cost and carbon footprints over the entire resource supply chain and manufacturing steps. This paper examines the relative costs of carbon mitigation from a life cycle perspective for 12 different hydrogen production techniques using fossil fuels, nuclear energy and renewable sources by technology substitution. Production costs and life cycle emissions are parameterized and re-estimated from currently available assessments to produce robust ranges to describe uncertainties for each technology. Hydrogen production routes are then compared using a combination of metrics, levelized cost of carbon mitigation and the proportional decarbonization benchmarked against steam methane reforming, to provide a clearer picture of the relative merits of various hydrogen production pathways, the limitations of technologies and the research challenges that need to be addressed for cost-effective decarbonization pathways. The results show that there is a trade-off between the cost of mitigation and the proportion of decarbonization achieved. The most cost-effective methods of decarbonization still utilize fossil feedstocks due to their low cost of extraction and processing, but only offer moderate decarbonisation levels due to previous underestimations of supply chain emissions contributions. Methane pyrolysis may be the most cost-effective short-term abatement solution, but its emissions reduction performance is heavily dependent on managing supply chain emissions whilst cost effectiveness is governed by the price of solid carbon. Renewable electrolytic routes offer significantly higher emissions reductions, but production routes are more complex than those that utilise naturally-occurring energy-dense fuels and hydrogen costs are high at modest renewable energy capacity factors. Nuclear routes are highly cost-effective mitigation options, but could suffer from regionally varied perceptions of safety and concerns regarding prolife
Wagner JL, Lee-Lane D, Monaghan M, et al., 2019, Recovery of excreted n-butanol from genetically engineered cyanobacteria cultures: Process modelling to quantify energy and economic costs of different separation technologies, ALGAL RESEARCH-BIOMASS BIOFUELS AND BIOPRODUCTS, Vol: 37, Pages: 92-102, ISSN: 2211-9264
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
Roberts F, Richard C, Zemichael F, et al., 2018, Base-free, tunable, Au-catalyzed oxidative esterification of alcohols in continuous flow, Reaction Chemistry and Engineering, Vol: 3, Pages: 942-948, ISSN: 2058-9883
Under continuous flow conditions, hydrogen peroxide oxidizes primary alcohols (cinnamyl alcohol, decenol, decanol and benzyl alcohol) in methanol over Au/TiO2, without the need for added base. While the allylic alcohols afforded conjugated aldehydes, aliphatic and benzylic alcohols afforded acids or esters. Selectivity for either product can be achieved by adjusting the reaction parameters. Kinetic studies revealed that the formation of the easter is faster than that of the acid, due to a greater pre-organization (larger ln A) attributed to the more favourable formation of the hemiacetal intermediate.
Cardoso A, Ramirez Reina T, Suelves I, et al., 2018, Effect of carbon-based materials and CeO<inf>2</inf>on Ni catalysts for Kraft lignin liquefaction in supercritical water, Green Chemistry, Vol: 20, Pages: 4308-4318, ISSN: 1463-9262
© The Royal Society of Chemistry 2018. Kraft lignin (KL) is a by-product from cellulose production typically treated as a waste or used as a low-value fuel in heat and power generation in the pulp and paper industry. This study explores KL upgrading to monoaromatic compounds using supercritical water (SCW) as reaction medium. The effect of Ni-CeO2catalysts supported on carbon nanofibers (CNF) and activated carbon (AC) on the product distribution was investigated. These catalysts were prepared by a wet-impregnation method with acetone, and reduced Ni was observed without the use of H2. CNF presented a high degree of stability in SCW. Ni in its reduced state was still present in all spent catalysts, mainly when CNF were the support. While catalysts supported in AC led to high yields of char and gas, a 56 wt% yield of a light liquid fraction, recovered as dichloromethane (DCM)-soluble product and consisting mainly of (methoxy)phenols (>80 mol%), was obtained in a batch reactor at 400 °C, 230 bar, with Ni-CeO2/CNF as a catalyst. A short reaction time was key to avoid the formation of gas and char. This study demonstrates that high yields of DCM-soluble products from KL and low char formation can be obtained by using only SCW and catalysts, an alternative to widely reported approaches like the addition of organic co-solvents (e.g., phenol) and/or H2.
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