The synthesis of maleic anhydride: study of a new process and improvement of the industrial catalyst

Maleic anhydride is an important chemical intermediate mainly produced by the selective oxidation of n-butane, an industrial process catalyzed by vanadyl pyrophosphate-based materials, (VO)2P2O7. The first topic was investigated in collaboration with a company specialized in the production of organic anhydrides (Polynt SpA), with the aim of improving the performance of the process for the selective oxidation of n-butane to maleic anhydride, comparing the behavior of an industrial vanadyl pyrophosphate catalysts when utilized either in the industrial plant or in lab-scale reactor. The study was focused on how the catalyst characteristics and reactivity are affected by the reaction conditions and how the addition of a dopant can enhance the catalytic performance. Moreover, the ageing of the catalyst was studied, in order to correlate the deactivation process with the modifications occurring in the catalyst. The second topic was produced within the Seventh Framework (FP7) European Project “EuroBioRef”. The study was focused on a new route for the synthesis of maleic anhydride starting from an alternative reactant produced by fermentation of biomass:“bio-1-butanol”. In this field, the different possible catalytic configurations were investigated: the process was divided into two main reactions, the dehydration of 1-butanol to butenes and the selective oxidation of butenes to maleic anhydride. The features needed to catalyze the two steps were analyzed and different materials were proposed as catalysts, namely Keggin-type polyoxometalates, VOPO4∙2H2O and (VO)2P2O7. The reactivity of 1-butanol was tested under different conditions, in order to optimize the performance and understand the nature of the interaction between the alcohol and the catalyst surface. Then, the key intermediates in the mechanism of 1-butanol oxidehydration to MA were studied, with the aim of understanding the possible reaction mechanism. Lastly, the reactivity of the chemically sourced 1-butanol was compared with that one of different types of bio-butanols produced by biomass fermentation

Uncertainty in cell confluency measurements

Pharmaceutical industries have declared their need of metrology in the cellular field, to improve new drugs developing time and costs by high-content screening technologies. Cell viability and proliferation tests largely use confluency of cells on a bi-dimensional (2D) surface as a biological measurand. The confluency is measured from images of 2D surface acquired via microscopy techniques. The plethora of algorithms already in use aims at recognizing objects from images and identifies a threshold to distinguish objects from the background. The reference method is the visual assessment from an operator and any objective uncertainty estimation is not yet available. A method to estimate the image analysis contribution to confluency uncertainty is here proposed. A maximum and a minimum threshold are identified from a visual assessment of the free edge of the cells. An application to a fluorescence microscopy image of 2D of PT-45 cell cultures is reported. Results shows that the method can be a promising solution to associate an uncertainty to cell confluency measurements to enhance reliability and efficiency of high-content screening technologies

PRODUCTION OF GASEOUS CERTIFIED REFERENCE MATERIALS AT INRiM FOR AMOUNT OF SUBSTANCE FRACTION OF CO2

Due to the involvement of carbon dioxide (CO2) in the global warming effects, INRiM is developing certified reference materials (CRMs) of CO2 in synthetic air. The mixtures are prepared by gravimetry, a primary method, and verified by NonDispersive Infrared spectroscopy. The CO2 amount fraction in the mixtures and its associated uncertainty are the certified properties of the CRMs. A corresponding stability study of the amount fraction of CO2 is also ongoing. Further work foresees the development of CRMs for the isotopic composition of CO2 in air, after the participation in specific international comparisons

Stability study and uncertainty evaluation of CO2 certified reference materials for greenhouse gases monitoring

The continuous rising in the concentration of carbon dioxide (CO2) in the atmosphere is one of the main causes of the increase in the greenhouse effect and global warming. To monitor the alarming scenario and to provide Governments and decision makers with reliable emission data, gaseous certified reference materials (CRMs) at atmospheric CO2 amount fraction are needed. This paper describes two independent metrological traceability paths established at INRiM for the preparation of this kind of CRMs. The aim of this publication is to show a method for evaluating the uncertainty associated with CRM stability and to demonstrate that there is no significant trend in the results over time. Such CRMs are produced as an intermediate step towards the development of novel generation CRMs certified also for the isotopic composition

Realisation of primary mixtures of CO2 in air at known isotopic composition

The monitoring of the increasing levels of CO2 in atmosphere, together with the discrimination between the natural and anthropogenic sources of CO2, is of utmost importance to support climate change studies and the reduction of the CO2 emissions from human activities in the close future. The involvement of the metrological community is essential to achieve the comparability of results over space and time, to assure accuracy and metrological traceability, linking all the individual measurement results to common and stable reference standards. The availability of sound and affordable reference materials for the measurement of the isotopic composition of CO2 at ambient amount fraction is foreseen to support the researchers operating in the isotope measurement field, by means of spectroscopic techniques, to assure the metrological traceability for the determination of the isotopic composition of CO2 in air. Reference gas mixtures at known isotopic composition produced by means of primary methods, such as gravimetry, represent a good opportunity for this purpose. At INRiM, the Italian National Metrology Institute, the realization of gaseous reference materials of CO2 in air at known δ13C-CO2 started within the European Joint Research Project (JRP) 16ENV06 SIRS, and continued with the JRP 19ENV05 STELLAR. The reference mixtures are realized by the gravimetric method, following the ISO standard 6142-1, in high-pressure cylinders of aluminum alloy, obtaining low preparation uncertainties of 0.33 % for the CO2 amount fraction at atmospheric level. These mixtures are prepared from parent mixtures at higher amount fraction, realized at INRiM from different pure CO2 sources. Non Dispersive Infrared Spectroscopy (NDIR ABB URAS 14, Switzerland) is used to verify the mixtures for their amount fraction values while Fourier Transform Infrared Spectroscopy (FTIR Thermo Scientific Nicolet iS50, USA) is used for the δ13C-CO2 value assignment. The δ13C-CO2 values of the gravimetric mixtures span in the range from +1.3 ‰ to -42 ‰. Recently, a Cavity Ring-Down Spectrometer (CRDS G2131i Picarro, USA) was acquired to double-check the isotopic composition of the prepared mixtures. Preliminary tests were carried out for the metrological characterization of the instrument, followed by the set-up of the analytical methodology for the confirmation of the isotopic composition of some mixtures prepared within the STELLAR project and sent to other project partners for analysis in the past two years. The results of the tests carried out are presented in this work, together with some future perspectives for the realization of primary reference mixtures of CO2 in air at know isotopic composition on a larger scale

Toward the realization of reproducible AFM measurements of elastic modulus in biological samples

partially_open6The validation of the AFM method for elastic modulus E measurement in soft materials (E <5 MPa) is still missing. The interest of measurements in materials with E <5 MPa is mainly biological, including soft tissues and single cells. For the diagnosis of malignant human tumors, a change in cell elasticity, within tissues, has recently been recognized as a marker of metastatic potential. To measure a cell elasticity difference, reproducible E measurements in biological samples are needed. In this work a robust method for a metrological validation of E measurements in the range 500–5000 kPa was developed, based on the realization of thick E standard samples and on the study of the interactions between the measurement process and the sample at micro- and nano-scale. E measurement reproducibility limit of 4% has been reached. This allows designing a very sensitive and reproducible measurement of E in biological samples representing thus a powerful diagnostic tool for cancer detection.partially_openA. Demichelis; C. Divieto; L. Mortati; S. Pavarelli; G. Sassi; M. SassiDemichelis, A.; Divieto, C.; Mortati, L.; Pavarelli, S.; Sassi, G.; Sassi, M

Metrological challenges for the monitoring of the partial pressure of CO2 in the marine environment

The observed rising levels of carbon dioxide (CO2) in atmosphere, highly caused by anthropogenic emissions, are responsible for fundamental changes occurring also in seawater carbonate chemistry. The oceans are absorbing more CO2 from the atmosphere, which is decreasing seawater pH and leading to the acidification of marine waters, with important consequences for the global ecosystem. At present, the partial pressure of CO2 (pCO2) is one of the few variables of the marine carbon cycle directly measurable in situ. In order to achieve meaningful and significant measurement results, it is necessary to reach uncertainties small enough to discriminate observed variations due to natural fluctuations, from those due to real trends. In this framework, the development and validation of proper analytical methods and measurement standards is of utmost importance. Despite the availability of a variety of in situ sensors, currently used to monitor pCO2 in marine environment, there are several problems to be faced, such as the differences in adopted calibration methodologies and non-validated procedures, or the lack of metrological traceability and of operational harmonization for field measurements. In addition, the scarcity and expensiveness of suitable reference materials to calibrate instrumentation used for pCO2 monitoring represents an issue. A promising approach could be the provision, on a larger scale, of appropriate reference standards in gas phase to be used to calibrate pCO2 sensors, due to the stability of the CO2 in the gas mixtures. In addition, intermediate-level standards and working standards, could represent a more affordable and widespread traceability source. Concerning the analytical methods for pCO2 monitoring, Non Dispersive Infrared (NDIR) photometry is quite used, but its application could be potentiated. At INRiM, the Italian Metrology Institute, gaseous reference standards of CO2 at known amount fraction in synthetic air or nitrogen are produced by the gravimetric method. In the framework of the H2020 Project “MINKE - Metrology for Integrated Marine Management and Knowledge-Transfer Network”, feasibility studies are ongoing to extend the use of these primary mixtures to the calibration of sensors for pCO2 in seawater, in cooperation with the National Institute of Oceanography and Applied Geophysics (OGS). In the present work, some preliminary results of this activity will be presented

1-Butanol dehydration and oxidation over vanadium phosphate catalysts

The transformation of 1-butanol into either butenes or maleic anhydride was carried out both with and without oxygen, using V/P/O catalysts. With vanadyl pyrophosphate prepared by coprecipitation, at temperature lower than 240 ◦C and without oxygen, selectivity to butenes was higher than 90%, but a slow deactivation took place. At temperature higher than 300 ◦C and in the presence of air, maleic and phthalic anhydrides were the prevailing products, with selectivity of 60% and 14%, respectively. Catalytic performance was affected by crystallinity and acidity. αI-VOPO4 showed a poor performance in the absence of air, with a quick deactivation due to coke accumulation; but it displayed an excellent selectivity to butenes (close to 98%) at temperatures lower than 320 ◦C in the presence of air, with stable performance. At temperature higher than 360 ◦C, α I-VOPO4 was reduced to vanadyl pyrophosphate and catalyzed the direct oxidation of 1-butanol into maleic anhydride, but with 35% selectivit

Generation of CO2 gas mixtures by dynamic dilution for the development of gaseous certified reference materials

The use of Certified Reference Materials (CRMs) is of utmost importance to achieve the comparability and traceability of data, which are essential features of measurement results in environmental and climate fields. The present paper focuses on the generation of gas mixtures at known composition of carbon dioxide at atmospheric amount-of-substance fraction in synthetic air by means of a dynamic dilution system, designed and implemented at the Istituto Nazionale di Ricerca Metrologica (INRiM). The validation of the dynamic system in terms of amount-of-substance fraction is presented. The system was also used to verify the carbon dioxide amount-ofsubstance fraction of a suite of gas mixtures gravimetrically prepared at INRiM in the framework of the EMPIR Joint Research Project 19ENV05 – STELLAR. Dynamic dilution proved to be an effective tool for the preparation and certification of CRMs for gaseous pollutants (i.e. carbon dioxide, nitrogen oxides) relevant for monitoring environmental pollution and climate changes

Optical emission of strained direct-band-gap Ge quantum well embedded inside InGaAs alloy layers

We studied the optical properties of a strain-induced direct-band-gap Ge quantum well embedded in InGaAs. We showed that the band offsets depend on the electronegativity of the layer in contact with Ge, leading to different types of optical transitions in the heterostructure. When group-V atoms compose the interfaces, only electrons are confined in Ge, whereas both carriers are confined when the interface consists of group-III atoms. The different carrier confinement results in different emission dynamics behavior. This study provides a solution to obtain efficient light emission from Ge