Synthesis of n-hexyl acetate in batch and chromatographic reactors

Petrochemical and fine chemical industries face a daunting problem in recovering acetic acid from its aqueous solutions. The recovery of acetic acid could be done through esterification reaction. However, esterification is an equilibrium limited reaction. Multi-functional reactors such as chromatographic reactor (CR) and reactive distillation column (RDC) are promising technologies mainly for equilibrium limited reactions wherein reaction and separation of products are carried out in a single equipment that tends to shift the equilibrium towards the desired direction which is not possible in a classical batch reactor. Physical and chemical characterisation of ion exchange resin catalysts such as scanning electron microscopy, Brunauer-Emmett-Teller (BET) surface area measurement, pore size distribution, elemental analysis, true density and particle size distribution were carried out to access the catalysts performance for n-hexyl acetate synthesis. Esterification of acetic acid with n-hexanol was studied with both dilute and concentrated acid in the presence of cation exchange resins (macroporous and gelular) in a jacketed stirred batch reactor to synthesise a value added ester, namely n-hexyl acetate and also to study the recovery of acetic acid from the waste aqueous streams. The effect of various parameters such as speed of agitation, catalyst particle size, feed mole ratio of n-hexanol to acetic acid, reaction temperature, catalyst loading and reusability of catalysts was studied for the optimisation of the reaction condition in a batch reactor. The non-ideality of each component in the reacting mixture was accounted for by using the activity coefficient via the use of the UNIFAC group contribution method. The kinetic data were correlated with both pseudo-homogeneous (PH) and adsorption based heterogeneous reaction rate models, e.g., Eley-Rideal (ER), Langmuir-Hinshelwood-Hougen-Watson (LHHW), and the modified LHHW (ML). Pseudo-homogeneous (PH) model gave the best representation of the kinetic data found experimentally. The feasibility of reactive distillation for the recovery of acetic acid using n-hexanol was evaluated through residue curve map (RCM) determination experiments. RCM provides information to a design engineer of the existence of separation boundaries imposed by the singular points corresponding to the reactive/non-reactive azeotropes, thus provides an insight into the feasibility of reactive distillation for this purpose. A laboratory scale batch chromatographic reactor was designed and constructed. Batch chromatographic reactor experiments were carried out using different parameters such as feed flow rate, feed mole ratio of n-hexanol to acetic acid, desorbent (n-hexanol) flow rate and reaction step to maximise the formation of n-hexyl acetate as well to achieve complete conversion of acetic acid. Continuous chromatographic reactor was designed, constructed and commissioned on the basis of the results obtained from the batch chromatographic reactor experiments. The experiments carried out in continuous chromatographic reactor correlated very well with the results from the batch chromatographic reactor for the optimised condition

Kinetic studies of liquid phase ethyl tert-butyl ether (ETBE) synthesis using macroporous and gelular ion exchange resin catalysts

Ethyl tert-butyl ether (ETBE) synthesis from ethanol (EtOH) and tert-butyl alcohol (TBA) was studied with different macroporous and gelular ion exchange resin catalysts. Purolite® (CT-124, CT-145H, CT-151, CT-175 and CT-275) and Amberlyst® (15 and 35) ion exchange resins were used for the present work. Effect of various parameters such as catalyst type, temperature, reactants feed molar ratio and catalyst loading were studied for the optimisation of reaction condition. Among the catalysts studied, Purolite CT-124 gave better results for TBA conversion and selectivity towards ETBE. Kinetic modelling was performed with this catalyst and activation energy and water inhibition coefficient were determined. Heterogeneous kinetic models [e.g., Eley-Rideal (ER), Langmuir-Hinshelwood-Hougen-Watson (LHHW)] were unable to predict the behaviour of this etherification reaction, whilst the quasi-homogeneous (QH) model represented the system very well over wide range of reaction conditions

Association between SGLT2 inhibitor treatment and diabetic ketoacidosis and mortality in people with type 2 diabetes admitted to hospital with COVID-19

   Objective  To determine the association between prescription of SGLT2 inhibitors and diabetic ketoacidosis (DKA) incidence or mortality in people with type 2 diabetes hospitalized with COVID-19.  Research Design and Methods  This was a retrospective cohort study based on secondary analysis of data from a large nationwide audit from a network of 40 centres in United Kingdom with data collection up to December 2020 that was originally designed to describe risk factors associated with adverse outcomes among people with diabetes who were admitted to hospital with COVID-19.. The primary outcome for this analysis was DKA on or during hospital admission. The secondary outcome was mortality. Crude, age-sex adjusted and multivariable logistic regression models, were used to generate odds ratios and 95% confidence intervals for people prescribed SGLT2 inhibitor compared to those not prescribed SGLT2 inhibitor.   Results  The original national audit included 3067 people with type 2 diabetes who were admitted to hospital with COVID-19, of whom 230 (7.5%) were prescribed SGLT2 inhibitors prior to hospital admission. Mean (SD) age of the overall cohort was 72 years, 62.3% were men and 34.9% were prescribed insulin. Overall, 2.8% of the total population had DKA and 35.6% people died. The adjusted odds of DKA were not significantly different between those prescribed SGLT2 inhibitors and those not (OR 0.56, 0.16-1.97). The adjusted odds of mortality associated with SGLT2 inhibitors were similar in the total study population (OR 1.13, 0.78-1.63 ), in the sub-group prescribed insulin (OR 1.02, 0.59-1.77), and in the sub-group that developed DKA (OR 0.21, 0.01-8.76).  Conclusions We demonstrate a low risk of DKA and high mortality rate in people with type 2 diabetes admitted to hospital with COVID-19 and limited power but no evidence of increased risk of DKA or in-hospital mortality associated with prescription of SGLT2 inhibitors. </p

Esterification of Acetic Acid with <i>n</i>‑Hexanol in Batch and Continuous Chromatographic Reactors Using a Gelular Ion-Exchange Resin as a Catalyst

Heterogeneously catalyzed esterification reactions of acetic acid and <i>n</i>-hexanol were studied in batch and continuous chromatographic reactors in the presence of a gelular ion-exchange resin catalyst (Purolite CT-124) to synthesize a value added ester, namely <i>n</i>-hexyl acetate. A laboratory scale batch chromatographic reactor column (BCRC) was designed and constructed. BCRC experiments were carried out using different parameters such as feed flow rate, feed mole ratio (FMR) of <i>n</i>-hexanol to acetic acid, desorbent (<i>n</i>-hexanol) flow rate, and reaction step time to maximize the formation of <i>n</i>-hexyl acetate as well as to achieve complete conversion of acetic acid. Samples were collected from the chromatographic reactor column (CRC) outlet at regular intervals and were analyzed by gas chromatography (GC). The continuous chromatographic reactor column (CCRC) was designed, constructed, and commissioned on the basis of the results obtained from the BCRC experiments. The experiments carried out in a CCRC correlate very well with the results obtained from the optimized reaction condition in a BCRC for maximum formation of <i>n</i>-hexyl acetate and complete conversion of acetic acid

On the wake of an isolated rotating wheel: An experimental and numerical investigation

The wake of an isolated, rotating wheel of a geometry typical of those used in open-wheel motorsport, is investigated. The CFD is validated by comparing the wake data gathered from this method with the data from the PIV wind tunnel experiments, where analysis of the data showed a good agreement between the two methods. A comparison of the mean and instantaneous flow-fields obtained from the CFD shows significant differences in the wake topology. The time-averaged illustration of the flow shows an inverted “T” shape, and consists of a pair of upper and lower counter-rotating vortices that merge downstream, with the upper being dominant. The instantaneous wake follows the same fundamental shape, but consists of incoherent macro-scale eddies, together with these counter-rotating vortices in a deformed state. Analysis of the unsteadiness of the wake via proper orthogonal decomposition reveals significant transverse and vertical velocity fluctuations. The transverse velocity fluctuations are driven by both the contraction and expansion of the contact patch wake and the instability of the merged counter-rotating vortex pair that eventually lead to a transverse flapping motion of the bulk wake. The instability of these vortices also leads to vertical velocity fluctuations in the vortex-induced downwash region.</p

ABCD position statement on risk stratification of adult patients with diabetes during COVID-19 pandemic

At the time of submission of this manuscript, the COVID-19 pandemic had cost nearly 60,000 lives in the UK. This number currently stands at over 120,000 deaths. A high proportion (one third) of these lived with diabetes. The huge acute and emergency medicine effort to support people with COVID-19 has had a major knock-on impact on the delivery of routine clinical care, especially for long-term conditions like diabetes.Challenges to the delivery of diabetes services during this period include a reduction in medical and nursing staff, limitations placed by social distancing on physical clinical space, and balancing virtual vs face-to-face care. There is a need to re-group and re-organise how we deliver routine out-patient adult diabetes services during the ongoing COVID-19 pandemic. We offer some suggestions for how patients can be stratified into red (urgent), amber (priority) and green (routine) follow up with suggestions of how often people should be seen. We also offer recommendation on how we can identify those at highest risk and try and minimise the long- term impact of COVID on diabetes careDuring the COVID pandemic we have seen things happen in days that previously took years. The restart of diabetes services has triggered a more widespread use of virtual consultations and data management systems, but also offers an opportunity for more joined-up and cohesive working between primary and specialist care. While we do our best to keep our patients and colleagues safe, this pandemic is already proving to be a catalyst for change, accelerating the appropriate use of technology in diabetes care and implementing innovative solutions. To achieve this aspiration, further work – currently led by the Association of British Clinical Diabetologists in collaboration with Diabetes UK and the Primary Care Diabetes Society – to make recommendations on future proofing diabetes care in UK is in progress