Techno-Economic Assessment and Sensitivity Analysis of Glycerol Valorization to Biofuel Additives via Esterification

Glycerol is a valuablefeedstock, produced in biorefineries asa byproduct of biodiesel production. Esterification of glycerol withacetic acid yields a mixture of mono-, di-, and triacetins. The acetinsare commercially important value-added products with a wide rangeof industrial applications as fuel additives and fine chemicals. Esterificationof glycerol to acetins substantially increases the environmental sustainabilityand economic viability of the biorefinery concept. Among the acetins,diacetin (DA) and triacetin (TA) are considered high-energy-densityfuel additives. Herein, we have studied the economic feasibility ofa facility producing DA and TA by a two-stage process using 100,000tons of glycerol per year using Aspen Plus. The capital costs wereestimated by Aspen Process Economic Analyzer software. The analysisindicates that the capital costs are 71 M$, while the operating costsare 303 M$/year. The gross profit is 60.5 M$/year, while the NPV ofthe project is 235 M$ with a payback period of 1.7 years. Sensitivityanalysis has indicated that the product price has the most impacton the NPV

Use of Short Time-on-Stream Attenuated Total Internal Reflection Infrared Spectroscopy To Probe Changes in Adsorption Geometry for Determination of Selectivity in the Hydrogenation of Citral

A new experimental procedure based on attenuated total reflection infrared spectroscopy has been developed to investigate surface species under liquid phase reaction conditions. The technique has been tested by investigating the enhanced selectivity in the hydrogenation of α,β-unsaturated aldehyde citral over a 5% Pt/SiO₂ catalyst toward unsaturated alcohols geraniol/nerol, which occurs when citronellal is added to the reaction. The change in selectivity is proposed to be the result of a change in the citral adsorption mode in the presence of citronellal. Short time on stream attenuated total internal reflection infrared spectroscopy has allowed identification of the adsorption modes of citral. With no citronellal, citral adsorbs through both the CC and CO groups; however, in the presence of citronellal, citral adsorption occurs through the CO group only, which is proposed to be the cause of the altered reaction selectivity

Structure and dynamics of aqueous 2 propanol mixtures: a THz TDS, NMR and neutron diffraction study

Aqueous liquid mixtures, in particular, those involving amphiphilic species, play an important role in many physical, chemical and biological processes. Of particular interest are alcohol/water mixtures; however, the structural dynamics of such systems are still not fully understood. Herein, a combination of terahertz time-domain spectroscopy (THz-TDS) and NMR relaxation time analysis has been applied to investigate 2-propanol/water mixtures across the entire composition range; while neutron diffraction studies have been carried out at two specific concentrations. Excellent agreement is seen between the techniques with a maximum in both the relative absorption coefficient and the activation energy to molecular motion occurring at ∼90 mol% H2O. Furthermore, this is the same value at which well-established excess thermodynamic functions exhibit a maximum/minimum. Additionally, both neutron diffraction and THz-TDS have been used to provide estimates of the size of the hydration shell around 2-propanol in solution. Both methods determine that between 4 and 5 H2O molecules per 2-propanol are found in the 2-propanol/water clusters at 90 mol% H2O. Based on the acquired data, a description of the structure of 2-propanol/water across the composition range is presented