Spreading the word (about chemical engineering)

The current situation regarding falling undergraduate admissions to chemical engineering departments in the UK is analyzed with reference to the structure of secondary education. A collaboration is proposed between departments of chemical engineering, local schools, and industry for introducing the concepts of chemical engineering to school-aged children. The proposed scheme integrates a design exercise within the teaching of organic chemistry and is aimed at increasing awareness of the discipline and ultimately increasing the number of admissions to university departments. The proposal is intended for widespread application both within the UK and elsewhere

Recovery of excreted n-butanol from genetically engineered cyanobacteria cultures: Process modelling to quantify energy and economic costs of different separation technologies

The photoautotrophic production of excreted biofuels from genetically engineered cyanobacteria and microalgae represents a new and promising alternative to conventional algal fuel technologies. N-butanol is a particularly promising fuel product, as it can be directly used in petroleum engines, and has been successfully expressed in species of Synechococcus elongates 7942 and Synechocystis sp. PCC 6803. However, the high energy requirements of recovering butanol from dilute mixtures can easily outweigh the energy content of the fuel and must be carefully assessed and optimized. Consequently, the recovery of butanol was modelled using four of the most promising butanol separation technologies (distillation, gas stripping, pervaporation and ionic liquid extraction) to calculate the minimum butanol culture concentrations required to render the process energy-positive. With a breakeven concentration of only 3.7 g L -1 , ionic liquid extraction proved much more efficient than the distillation base-case scenario (9.3 g L -1 ), whilst neither pervaporation (10.3 g L -1 ) nor gas stripping (16.9 g L -1 ) could compete on an energy basis with distillation. Despite this, due to the high costs of the ionic liquid solvent, the lowest capital costs are obtained for distillation (pilot plant scale, butanol culture concentrations of 10 g L -1 ), whilst pervaporation carries the lowest utility costs, as a result of its low electrical energy demand. Although currently achieved maximum n-butanol culture concentrations are significantly below the calculated break-even values for all four technologies, the present work provides an important threshold for future strain development. Moreover, the recovery of side-products from purged biomass could help to reduce the costs associated with biofuel production

Photocatalytic production of bisabolene from green microalgae mutant: process analysis and kinetic modeling

Currently, algal fuel research has commenced to shift toward genetically engineered mutants able to express and excrete desired products directly into the culture. In this study, a mutant strain of Chlamydomonas reinhardtii, engineered for bisabolene (alternative biodiesel) excretion, was cultivated at different illumination and temperatures to investigate their effects on cell growth and bisabolene production. Moreover, a kinetic model was constructed to identify the desirable conditions for biofuel synthesis. Three original contributions were concluded. First, this work confirmed that bisabolene was partially synthesized independently of biomass growth, indicating its feasibility for continuous production. Second, it was found that while bisabolene synthesis was independent of light intensity, it was strongly affected by temperature, resulting in conflicting desirable conditions for cell growth and product synthesis. Finally, through model prediction, optimal operating conditions were identified for mutant growth and bisabolene synthesis. This study therefore paves the way toward chemostat production and process scale-up

Deep learning based surrogate modeling and optimization for Microalgal biofuel production and photobioreactor design

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 modelling. 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 modelling 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 modelling and optimization

Controlled multiphase oxidations for continuous manufacturing of fine chemicals

The feasibility of an integrated continuous biphasic oxidation process was studied, incorporating (i) electrochemical generation of an oxidant, (ii) membrane emulsification and an Oscillatory Flow Reactor (OFR) to facilitate mass-transfer in a biphasic reaction system and (iii) product extraction to enable regeneration of the oxidant. The biphasic, organic solvent-free dihydroxylation of styrene by ammonium peroxodisulfate solutions (including electrochemically generated peroxodisulfate) was investigated as a model reaction, both in batch and in an OFR. Heating of peroxodisulfate in a strongly acidic solution was demonstrated to be essential to generate the active oxidant (Caro’s acid). Membrane emulsification allowed mass-transfer limitations to be overcome, reducing the time scale of styrene oxidation from several hours in a conventional stirred tank reactor to less than 50 min in a dispersion cell. The influence of droplet size on overall reaction rate in emulsions was studied in detail using fast image capturing technology. Generation of unstable emulsions was also demonstrated during the oxidation in OFR and product yields >70% were obtained. However, the high-frequency/high-displacement oscillations necessary for generation of fine droplets violated the plug flow regime. Membrane emulsification was successfully integrated with the OFR to perform biphasic oxidations. It was possible to operate the OFR/cross-flow membrane assembly in plug flow regime at some oscillatory conditions with comparable overall oxidation rates. No mass-transfer limitations were observed for droplets <60 lm. Finally, the continuous post-reaction separation was demonstrated in a single OFR extraction unit to enable continuous regeneration of the oxidant

Catalysis in Flow: Nickel-Catalyzed Synthesis of Primary Amines from Alcohols and NH₃

A highly selective synthesis of primary amines from alcohols and NH₃ was achieved on using a commercially available Ni catalyst, without adding H₂. Using a continuous flow reaction platform, the amination of aliphatic alcohols can be achieved in good yields and selectivities, as the accumulation of water byproduct can be removed. Competitive formation of the nitrile side-product was suppressed when the catalyst was prereduced. Modes of catalyst deactivation were also briefly examined

CFD and kinetic‐based modeling to optimize the sparger design of a large‐scale photobioreactor for scaling up of biofuel production

Microalgal biofuels have not yet achieved wide‐spread commercialization, partially as a result of the complexities involved with designing and scaling up of their biosystems. The sparger design of a pilot‐scale photobioreactor (120 L) was optimized to enable the scale‐up of biofuel production. An integrated model coupling computational fluid dynamics and microalgal biofuel synthesis kinetics was used to simulate the biomass growth and novel biofuel production (i.e., bisabolene) in the photobioreactor. Bisabolene production from Chlamydomonas reinhardtii mutant was used as an example to test the proposed model. To select the optimal sparger configuration, a rigorous procedure was followed by examining the effects of sparger design parameters (number and diameter of sparger holes and gas flow rates) on spatially averaged bubble volume fraction, light intensity, friction velocity, power input, biomass concentration, and bisabolene production. The optimized sparger design increases the final biomass concentration by 18%, thereby facilitating the scaling up of biofuel production

LiquizaldThermally Stable <i>N</i>‑Nitrosamine Precursor for Diazomethane

N-Methyl-N-nitroso-p-toluenesulfonamide (Diazald) and N-nitroso-β-methylaminoisobutyl methyl ketone (Liquizald) were compared in this study as diazomethane precursors for process scale-up. Thermal assessment flagged Diazald for explosion propagation and impact sensitivity using the Yoshida methodology, while Liquizald only indicated potential for impact sensitivity under more conservative Pfizer correlations. A higher onset temperature of Liquizald at 170 °C was determined. Compared to the onset temperature for Diazald (80 °C), Liquizald made a favorable candidate for exploitation of increased reaction rates at high temperatures using microreactor technologies. New kinetic parameters of decomposition were further used to study the potential for process intensification and identify the microreactor channel sizing for thermally stable and near-isothermal reactor operation

Experimental study of DI diesel engine performance using three different biodiesel fuels

Methyl esters derived from vegetable oils by the process of transesterification (commonly referred as ‘biodiesel’), can be used as an alternative fuel in compression ignition engines. In this study, three different vegetable oils (rape, soy and waste oil) were used to produce biodiesel fuels that were then tested in a four cylinder direct injection engine, typically used in small diesel genset applications. Engine performance and emissions were recorded at five load conditions and at two different speeds. This paper presents the results obtained for measurements of NOx and smoke opacity at the different speed and load conditions for the three biodiesels, and their blends (5 and 50% v/v) with mineral diesel. A simple combustion analysis was also performed where ignition delay, position and magnitude of peak cylinder pressure and heat release rate were examined to asses how the variation of chemical structure and blend percentage affects engine performance. Engine performance and emissions for all of the 5% biodiesel blends were indistinguishable from mineral diesel. However, at higher blends, the rape fuel exhibited better emission and performance characteristics than either the soy or waste fuels. Furthermore; whilst emissions trends varied for each blend and fuel, emissions of smoke were significantly reduced at all speed and load conditions, and NOx was reduced by up to 50% at low loads. It will also be shown that while engine performance was not significantly deteriorated by biodiesel, there was evidence of increased ignition delay with higher blends, and a possible two stage ignition process where mineral diesel ignited earlier than the biodiesel

From Organometallic Zinc and Copper Complexes to Highly Active Colloidal Catalysts for the Conversion of CO₂ to Methanol

A series of zinc oxide and copper(0) colloidal nanocatalysts, produced by a one-pot synthesis, are shown to catalyze the hydrogenation of carbon dioxide to methanol. The catalysts are produced by the reaction between diethyl zinc and bis­(carboxylato/phosphinato)­copper­(II) precursors. The reaction leads to the formation of a precatalyst solution, characterized using various spectroscopic (NMR, UV–vis spectroscopy) and X-ray diffraction/absorption (powder XRD, EXAFS, XANES) techniques. The combined characterization methods indicate that the precatalyst solution contains copper(0) nanoparticles and a mixture of diethyl zinc and an ethyl zinc stearate cluster compound [Et₄Zn₅(stearate)₆]. The catalysts are applied, at 523 K with a 50 bar total pressure of a 3:1 mixture of H₂/CO₂, in the solution phase, quasi-homogeneous, hydrogenation of carbon dioxide, and they show high activities (>55 mmol/g_ZnOCu/h of methanol). The postreaction catalyst solution is characterized using a range of spectroscopies, X-ray diffraction techniques, and transmission electron microscopy (TEM). These analyses show the formation of a mixture of zinc oxide nanoparticles, of size 2–7 nm and small copper nanoparticles. The catalyst composition can be easily adjusted, and the influence of the relative loadings of ZnO/Cu, the precursor complexes and the total catalyst concentration on the catalytic activity are all investigated. The optimum system, comprising a 55:45 loading of ZnO/Cu, shows equivalent activity to a commercial, activated methanol synthesis catalyst. These findings indicate that using diethyl zinc to reduce copper precursors in situ leads to catalysts with excellent activities for the production of methanol from carbon dioxide