Adsorption selectivity of CO2 over CH4, N2 and H2 in melamine-resorcinol-formaldehyde xerogels

Sorptive selectivity of melamine-resorcinol-formaldehyde xerogels, towards CO2, CH4, N2 and H2, is reported, where all systems demonstrate potential for selective adsorption of CO2 from corresponding binary gas mixtures. Selected gas mixtures represent important gas separation applications found in industry, i.e. CO2 removal from power plant flue gases (CO2-N2), sour gas sweetening (CO2-CH4), and separation of species in the water-gas shift reaction (CO2-H2). All materials tested exhibit microporous character, enhancing adsorption of small molecules, however, it is the inclusion of a nitrogen-rich material into the gel matrix that results in enhanced selectivities for these systems. Despite the porous character of the gels, under the test conditions used to simulate industrial parameters, all three balance gases, i.e. H2, N2 and CH4, showed low affinities for the xerogels, while CO2 adsorption was notably higher and increased with the inclusion and increased concentration of melamine. Ideal Adsorbed Solution Theory was used to demonstrate significant differences in adsorption uptake, especially for CO2-CH4, and high selectivities for CO2 over N2. In all cases, selected xerogels exhibited industrially relevant adsorption timescales for CO2 over competitor gases, demonstrating the potential of these materials for the selective adsorption of CO2 from process streams

Effects of secondary metal carbonate addition on the porous character of resorcinol-formaldehyde xerogels

A deeper understanding of the chemistry and physics of growth, aggregation and gelation processes involved in the formation of xerogels is key to providing greater control of the porous characteristics of such materials, increasing the range of applications for which they may be utilised. Time-resolved dynamic light scattering has been used to study the formation of resorcinol-formaldehyde gels in the presence of combinations of Group I (Na and Cs) and Group II (Ca and Ba) metal carbonates. It was found that the combined catalyst composition, including species and times of addition, is crucial in determining the end properties of the xerogels, via its effect on growth of clusters involved in formation of the gel network. Combination materials have textural characteristics within the full gamut offered by each catalyst alone; however, in addition, combination materials which retain the small pores associated with sodium carbonate catalysed xerogels exhibit a narrowing of the pore size distribution, providing an increased pore volume within an application-specific range of pore sizes. We also show evidence of pore size tunability while maintaining ionic strength, which significantly increases the potential of such systems for biological applications

Using the perceptions of chemical engineering students and graduates to develop employability skills

Recent years have seen increased global industry sector demand for chemical engineers, subsequent growth of Chemical Engineering (CE) degrees, producing additional qualified graduates. The Confederation of Business Industry have regularly indicated that employers are dissatisfied with skills sets offered by graduates; a 2004 World Chemical Engineering Council (WCEC) survey of experienced and newly employed chemical engineers’ perceptions of their own work skills indicated highest importance for general transferrable skills, with technical knowledge ranked considerably lower. A decade later, we investigate whether chemical engineers, both employed and in education, have similar skills perceptions, by surveying CE undergraduates in penultimate and final years of study, and CE alumni employed in CE roles; all from the University of Strathclyde. Again, transferrable skills were perceived as most important to respondents; as undergraduates gained industrial experience, a shift in perceived relative importance of technical knowledge occurred, again similar to the WCEC survey, otherwise, alumni and students had similar opinions regarding perceived degree of learning of various skills. Alumni were more critical of the quality of education with regards to management and transferrable skills, while female participants perceived business skills as undertaught, feeling considerably overexposed to the potential of research compared to male colleagues. Focus groups showed that male undergraduates valued ‘technical knowledge’ and ‘communicating professionally’; by contrast, female graduates highlighted ‘initiative’ and ‘business skills’. Consequently, training sessions were developed, focussing on transferable skills identified as important by all groups, to be delivered during academic year inductions, aligning skills to year curricula

Design of Experiments study on Scottish wood biochars and process parameter influence on final biochar characteristics

Native Scottish wood samples were investigated as potential, locally sourced, raw materials for biochar production. Screening experiments identified pure softwood as the preferable feedstock. Influence of operational parameters, i.e., activating gas flow rate (CO2), heating ramp rate and contact time on final biochar characteristics, was investigated using design of experiments. Surface area and biochar yield were selected as response variables. Minitab was used to define experimental run conditions and suggested an optimal output at 60 min contact time and 15 °C/min ramp rate for maximum responses. The highest surface area (764 m2/g) was achieved at 850 °C from softwood, albeit with a low yield of 15 %. Under optimised conditions, the observed surface area was 613 m2/g with ~ 18 % yield. Pareto charts suggested no influence of gas flow rate on chosen responses, which correlated well with experimental data. Pore structure was a combination of micro- and mesopores with average pore widths of 3-5 nm and an average point of zero charge of 7.40 ± 0.02. Proximate analysis showed an increase in fixed carbon content from 20 %, in the feedstock, to 80 %, in the optimised biochar. Morphological analysis showed a layered carbon structure in the biochars. The results show the significance of the selected feedstock as a potential source of biochar material, and the relevance of interplay of operational variables in biochar development and their final characteristics

Parametric study of factors affecting melamine-resorcinol-formaldehyde xerogels properties

Resorcinol-formaldehyde (RF) xerogels are organic materials have been widely studied due to their industrially relevant characteristics, through which, RF gels have significant potential to be tailored to specific applications. Xerogel properties have been tailored, within this study, by altering the synthesis procedure with a focus on monomer concentrations, catalyst to monomer ratio, and the introduction of a nitrogen-rich precursor, thereby incorporating nitrogen into the structure to additionally affect the chemical properties of the final gel. Melamine (M) is used as the source of nitrogen, partially replacing the resorcinol (R) typically used, and resulting in a melamine-resorcinol-formaldehyde (MRF) gel; synthesis was facilitated by a sodium carbonate catalyst (C), as often used in RF gel production. R/C and R/F molar ratios, and M concentration ([M]), were chosen as parameters to study in-depth, as they have previously been shown to markedly influence sol-gel formation. The MRF gels produced were subsequently characterized to determine porous structure and chemical functionality. The results indicate that, texturally, increasing [M] produces a similar effect as increasing R/C values: increasing pore size, while decreasing surface area. Pore volume tends to increase when R/C or M increase individually but pore volume and surface area decrease drastically when both variables increase concurrently. Microporosity also tends to increase as R/C decreases, and as the concentration of M is decreased. Altering the gel matrix, by replacing M for R, results in a weakening of the gel structure, as the bridges formed during curing are reduced in quantity, which indicates a maximum level of substitution that can occur within these materials. Combined, these results suggest that nitrogen can be successfully incorporated into organic gel structures but that the interplay between process variables is crucial in determining final gel characteristics for specific applications

The manufacture and characterisation of rosid angiosperm-derived biochars applied to water treatment

Marabu (Dichrostachys cinerea) from Cuba and aspen (Populus tremula) from Britain are two rosid angiosperms that grow easily, as a weed and as a phytoremediator, respectively. As part of scientific efforts to valorise these species, their barks and woods were pyrolysed at 350, 450, 550 and 650 °C, and the resulting biochars were characterised to determine the potential of the products for particular applications. Percentage carbon composition of the biochars generally increased with pyrolysis temperature, giving biochars with highest carbon contents at 650 °C. Biochars produced from the core marabu and aspen wood sections had higher carbon contents (up to 85%) and BET surface areas (up to 381 m 2 g −1) than those produced from the barks. The biochar porous structures were predominantly mesoporous, while micropores were developed in marabu biochars produced at 650 °C and aspen biochars produced above 550 °C. Chemical and thermal activation of marabu carbon greatly enhanced its adsorption capacity for metaldehyde, a molluscicide that has been detected frequently in UK natural waters above the recommended EU limit

Upskilling student engineers : the role of design in meeting employers' needs

Integrated learning makes use of group work to develop students’ professional competencies in tandem with their transferable skills. This paper looks at the skills required to undertake a fourth year chemical engineering “capstone design project” (Design) and the skills developed therein. Staff and students were surveyed about their perceived skills abilities, both before and after the project; the results of which showed agreement as to the skills necessary to undertake Design: these were grouped under personal effectiveness skills, communication skills or research skills. Students described a number of extra-curricular activities that contributed to skills development but sometimes failed to appreciate their transference to academic arenas. The surveyed students indicated that their confidence in all skills areas was increased by Design but there were instances where some individual sub-set devaluing occurred. There is a link between experiential practice, predominantly as a result of producing assessed components, and high skills confidence; hence, it is recommended that students are encouraged to reflect on their project experience and that integrated learning be promoted to develop all skills effectively

A family of nitrogen enriched metal organic frameworks with CCS potential

Materials with enhanced carbon capture capacities are required to advance post-combustive amelioration methods; these are necessary to reduce atmospheric carbon dioxide emissions and the associated rate of global temperature increase. Current technologies tend to be very energy intensive processes with high levels of waste produced; this work presents three new metal organic framework materials with embedded Lewis base functionalities, imparted by the nitrogen-rich ligand, demonstrating an affinity for carbon dioxide. Thus , we report the synthesis and characterization of a series of metal organic framework materials using a range of metal centers (Co, Ni, and Zn) with the 1,4-bis(pyridin-4-yl)-1,2,4,5-tetrazine organic linker, in the presence of ammonium hexafluorosilicate. Three distinct crystal structures are reported for Zn-pytz(hydro) 1D chains, and Ni-pytz and Co-pytz isostructural 1D Ladders. Co-pytz shows an uptake of 47.53mg CO2/g of sorbent, which equates to 15 wt % based on available nitrogen sites within the structure, demonstrating potential for carbon capture applications

Miniature nitro and peroxide vapor sensors using nanoporous thin films

With the increased and continuous threat of terrorist attacks in public areas, new sensors are required to safeguard the public from home-made explosive devices. Current commercial sensors for explosive vapors are high-cost, bulky equipment not amenable to mass production, thus limiting their widespread deployment within society. We are conducting research on polymer-based microsensors that can overcome these limitations. Our devices offer an approach to the realization of low-cost sensors that can readily be placed as a network of electronic sentinels that can be permanently located in areas of public access. The polymers are chemically tailored to have a high affinity for nitro and peroxide vapors and are grown electrochemically on microelectrodes. Novel nanoporous polymer-based sensors are demonstrated with a detection level of 200 ppb of nitro vapors. In addition, a prototype reversible sensor for peroxide vapors is demonstrated to low ppm concentrations