Propene oxide is a very important chemical whose production technology has changed a lot during the last 30 years. Nowadays, the most promising technology is the HPPO process in which the propene ...oxide is produced by oxidizing propene with hydrogen peroxide, via titanium silicalite-1 (TS-1) catalysis. Even if this technology has been patented in the early 1980s and some chemical plants are already in production, only few papers have been published until now dealing with the catalytic and kinetic aspects of the process. In this paper, the state of the art of the scientific knowledge and technical aspects related to propene oxide synthesis in the presence of TS-1 catalyst have been reviewed.
Biodiesel production has increased greatly in recent years, because of the less-detrimental effects of this fuel on the environment, compared to a conventional diesel obtained from petroleum. This ...work investigates the possibility of using MgO and calcined hydrotalcites as catalysts for the transesterification of soybean oil with methanol. The achieved experimental data show a correlation not only with the catalysts basicity, but also with its structural texture. However, the structural texture of the examined catalysts is dependent on both the precursor and the preparation method. At least four different types of basic sites have been individuated on the surface of MgO and calcined hydrotalcite catalysts. The strongest basic sites (super-basic) promote the transesterification reaction also at very low temperature (100 °C), while the basic sites of medium strength require higher temperatures to promote the same reaction. Ultimately, all the tested catalysts are resistant to the presence of moisture in the reaction environment.
► Some commercial copper chromite catalysts have been tested in ethanol dehydrogenation. ► A satisfactory activity and very high selectivity and good stability to sintering has been obtained for one ...of the proven catalysts. ► The best catalyst is a dispersed Cu catalyst, supported on alumina containing Cu chromite and BaCrO
4. ► Optimal conditions for high selectivities are:
T
=
240
°C,
P
=
20 bars and ethanol contact time (100
g
h
mol
−1). ► Pure hydrogen (exempt of CO) is obtained as by-product.
In the recent years, the interest in the ethanol production from renewable natural sources, as a possible alternative energy vector, has strongly grown in the world. The low-cost ethanol availability has also favored the study of the production of different chemicals such as ethylene, ethyl ether, acetaldehyde and ethyl acetate starting from ethanol as raw material. In this paper, ethanol dehydrogenation to ethyl acetate, in one step reaction, has been studied by using three different commercial copper based catalysts. The reaction has been conducted in a conventional packed bed tubular reactor, by exploring a temperature range of 200–260
°C and a pressure range of 10–30 bars. The best results have been found by using a commercial copper/copper chromite catalyst, supported on alumina and containing barium chromite as promoter, operating at 220–240
°C, 20 bars and 98
g
h
mol
−1 of ethanol contact time. In these conditions, a conversion of 65% with a selectivity to ethyl acetate of 98–99% has been obtained. However, the effect of temperature, pressure and ethanol contact time on both conversion and selectivity to ethyl acetate has been investigated. Moreover, the best catalyst has also shown a good stability to deactivation. For these reasons, the behavior of this catalyst has been subjected to a deeper investigation. The obtained results have been discussed on the basis of a reliable reaction scheme and mechanism. At last, a simplified scheme of a possible process is reported.
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► A review of the main technologies studied for producing biodiesel at lower cost is reported. ► The possibility of using new feedstock cheaper and not competing with food is ...mentioned. ► The possibility of intensify the traditional process catalyzed by homogeneous alkaline catalyst is reviewed. ► The main heterogeneous basic and acid catalysts studied in the literature are discussed and compared. ► New uses for the by-product glycerol reported in the literature are examined and discussed.
Biodiesel is a fuel safe, renewable, non-toxic, biodegradable and much less contaminant for the environment than conventional diesel. Moreover, it represents a strategic source of energy especially for the countries that have not oilfields. For these reasons, even if the cost of biodiesel is still greater than diesel from petroleum, many governments sustain this production. The cost of biodiesel is mainly affected by the cost of the feedstock but also an improvement of the adopted technology can contribute in reducing the costs. Therefore, it is imperative: to employ less expensive feedstock, that is, unrefined or waste oils; to use not edible oil coming from alternative sources as, for example, algae or Jathropa Curcas; to improve the actual technology based on the use of homogeneous alkaline catalysts through a better understanding of the reaction mechanism, to develop new biphasic kinetic models; to adopt techniques of process intensification; to introduce the use of heterogeneous catalysts, possibly finding a catalyst promoting in one step both esterification of free fatty acids and transesterification of tri-glycerides; to find new remunerative uses for the by-product glycerol. In this paper, all the mentioned aspects will be considered by reporting some of the most relevant results obtained in the last years.
Dispersion and deformation of cratonic fragments within orogens require weakening of the craton margins in a process of decratonization. The orogenic Borborema Province, in NE Brazil, is one of ...several Brasiliano/Pan-African late Neoproterozoic orogens that led to the amalgamation of Gondwana. A common feature of these orogens is that a period of extension and opening of narrow oceans preceded inversion and collision. For the case of the Borborema Province, the São Francisco Craton was pulled away from its other half, the Benino-Nigerian Shield, during an intermittent extension event between 1.0-0.92 and 0.9-0.82 Ga. This was followed by inversion of an embryonic and confined oceanic basin at ca. 0.60 Ga and transpressional orogeny from ca. 0.59 Ga onwards. Here we investigate the boundary region between the north São Francisco Craton and the Borborema Province and demonstrate how cratonic blocks became physically involved in the orogeny. We combine these results with a wide compilation of U-Pb and Nd-isotopic model ages to show that the Borborema Province consists of up to 65% of strongly sheared ancient rocks affiliated with the São Francisco/Benino-Nigerian Craton, separated by major transcurrent shear zones, with only ≈ 15% addition of juvenile material during the Neoproterozoic orogeny. This evolution is repeated across a number of Brasiliano/Pan-African orogens, with significant local variations, and indicate that extension weakened cratonic regions in a process of decratonization that prepared them for involvement in the orogenies, that led to the amalgamation of Gondwana.
Abstract
Background
Publications suggest immunomodulation co-therapy improves responder rates in uncontrolled/refractory gout patients undergoing pegloticase treatment. The MIRROR open-label trial ...showed a 6-month pegloticase + methotrexate co-therapy responder rate of 79%, compared to an established 42% pegloticase monotherapy responder rate. Longer-term efficacy/safety data are presented here.
Methods
Uncontrolled gout patients (serum urate SU ≥ 6 mg/dL and SU ≥ 6 mg/dL despite urate-lowering therapy ULT, ULT intolerance, or functionally-limiting tophi) were included. Patients with immunocompromised status, G6PD deficiency, severe kidney disease, or methotrexate contraindication were excluded. Oral methotrexate (15 mg/week) and folic acid (1 mg/day) were administered 4 weeks before and during pegloticase therapy. Twelve-month responder rate (SU < 6 mg/dL for ≥ 80% during month 12), 52-week change from baseline in SU, and extended safety were examined. Efficacy analyses were performed for patients receiving ≥ 1 pegloticase infusion. Pharmacokinetics (PK)/anti-drug antibodies (ADAs) were examined and related to efficacy/safety findings.
Results
Fourteen patients were included (all male, 49.3 ± 8.7 years, 13.8 ± 7.4-year gout history, pre-therapy SU 9.2 ± 2.5 mg/dL). Three patients were non-responders and discontinued study treatment before 24 weeks, one patient exited the study per protocol at 24 weeks (enrolled prior to treatment extension amendment), and 10 remained in the study through week 52. Of the 10, 8 completed 52 weeks of pegloticase + methotrexate and were 12-month responders. The remaining two discontinued pegloticase + methotrexate at week 24 (met treatment goals) and stayed in the study under observation (allopurinol prescribed at physicians’ discretion); one remained a responder at 12 months. At 52 weeks, change from baseline in SU was − 8.2 ± 4.1 mg/dL (SU 1.1 ± 2.4 mg/dL,
n
= 10). Gout flares were common early in treatment but progressively decreased while on therapy (weeks 1–12, 13/14 92.9%; weeks 36–52, 2/8 25.0%). One patient recovered from sepsis (serious AE). Two non-responders developed high ADA titers; fewer patients had trough concentrations (
C
min
) below the quantitation limit (BQL), and the median
C
min
was higher (1.03 µg/mL vs. BQL) than pegloticase monotherapy trials.
Conclusions
Pegloticase + methotrexate co-therapy was well-tolerated over 12 months, with sustained SU lowering, progressive gout flare reduction, and no new safety concerns. Antibody/PK findings suggest methotrexate attenuates ADA formation, coincident with higher treatment response rates.
Trial registration
ClinicalTrials.gov,
NCT03635957
. Registered on 17 August 2018.
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•Transient intraparticle model for fluid–solid adsorption kinetics.•The PDEs system solved with method of lines.•Methylene blue adsorption over silica used as a model system.•Physical ...parameters fitted on the batch experimental data.•Adsorption columns can be strictly simulated.
Scale-up processes are a central feature of chemical engineering science and technology. In this field, researchers’ efforts focus on the development of mathematical models that could be able to interpret physical and chemical phenomena on several dimension scales. Adsorption systems are typical operation units that fall in the mentioned category. In fact, moving from the particle to the fixed bed scale, a further dimension represented by the column axial coordinate is added to the system (and, for larger columns, also the column radial coordinate). In a previous work, an Adsorption Dynamic Intraparticle Model (ADIM) has been proposed and validated by the authors for adsorption batch systems. In the present paper, an attempt to implement the model equations for continuous systems has been made. For validation purposes, an adequate experimental investigation has been obtained by carrying out adsorption experiments both on batch and in continuous devices by using a model system that is represented by aqueous methylene blue over silica. Starting from batch experiments, where some fundamental mass transfer parameters, such as the surface diffusivity (DS), the tortuosity factor (τ) and the mass transfer coefficient (km), have been determined, the ADIM model has been extended to the prediction of the breakthrough curves obtained in continuous system, obtaining good agreements with the collected experimental data. In this way, it has been demonstrated that the ADIM model is a powerful, flexible tool for adsorption modeling over increasing dimension scales.
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► A kinetic study of the ethanol dehydrogenation to ethyl acetate. ► Cu/CuCr2O4 as catalyst supported on Al2O3 promoted with BaO–Cr2O3. ► A Langmuir–Hinshelwood–Hougen–Watson kinetic ...model resulted the best to interpret all the performed kinetic runs. ► A reliable mechanism is suggested and discussed.
A kinetic study of the ethanol dehydrogenation to ethyl acetate on a copper/copper-chromite catalyst has been performed. The used catalyst, in cylindrical pellets, contained also alumina as a support and barium chromate as a promoter. Support and promoter have the effect of increasing the activity, the selectivity and the stability of the catalyst, as shown in a previous work. The kinetic runs were carried out in a packed bed tubular reactor, alternatively filled with 2 or 50g of catalyst, approximately isothermal, by feeding pure ethanol together with a mixture of nitrogen and hydrogen as carrier gas. Kinetic runs have been made by changing the temperature, in the range of 200–260°C, the pressure between 10 and 30bar and the space time from 1 to 100ghmol−1. We have verified, at first, that inter-phase and intra-phase mass transfer limitations were negligible in the adopted conditions. Then, a Langmuir–Hinshelwood–Hougen–Watson kinetic model has been used for interpreting all the experimental data collected. This model corresponds to a mechanism in which the first step is the dissociative adsorption of ethanol on the surface, giving an adsorbed ethoxy group. Then, two other consecutive steps give place to respectively acetaldehyde as intermediate and ethyl acetate. This kinetic model allows a satisfactory fitting of all the performed experimental runs with a standard error below 15% for the runs performed with 2g of catalyst and less than 12% for the runs made with 50g of catalyst.
The strong growth of biodiesel production occurring in the last years has determined the availability of a great amount of the byproduct glycerol. Many researches in the world are therefore oriented ...to find new possible uses for glycerol also with the aim of reducing the cost of biodiesel. In this paper the chlorination of glycerol with gaseous hydrochloric acid to obtain 1,3-dichlorohydrin and then epichlorohydrin will be described. All the advantages of this process will be examined and discussed. The behavior of the different proposed catalysts (normally compounds containing carboxylic acid groups), the reaction kinetics, the effect of the catalyst concentration, the effect of HCl pressure, the vapor−liquid phase equilibria of the reaction products in the reaction environment, and the most convenient operative conditions have been studied, concluding with useful suggestions for the design of the industrial plants.
Biodiesel, a renewable fuel of vegetal origin, has been an object of a rapidly growing interest, in the latest years, both as a pure fuel and as blending component to reduce exhaust pollutants of ...traditional diesel fuel. Biodiesel is conventionally produced through a well-established technology that involves the use of alkaline catalysts and is, therefore, not compatible with the presence of free fatty acids (FFAs) in the feedstock due to the formation of soaps. Also the presence of FFA in small amounts is detrimental, because, formed soaps strongly affect the successive glycerol separation giving place to a long settling time. Normally, highly refined vegetable oils are used as raw materials for biodiesel production. A preliminary stage of acidity reduction is necessary, when the starting material is characterized by a high free acidity (higher than 0.5% by weight). This pre-treatment can be pursued, as example, by means of an esterification reaction of the FFAs with methanol, catalyzed by sulphonic ionic exchange resins. In the present work, a batch reactor has been used for the study of the above-mentioned reaction and different acid ionic exchange resins have been tested as heterogeneous catalysts. Two kinds of substrates have been submitted for esterification with methanol: a model mixture of soybean oil artificially acidified with oleic acid and a commercial high-acidity mixture of waste fatty acids (oleins). A detailed kinetic model has been developed and tested in which the following key phenomena, characterizing the system, have been introduced: (i) the physical phase equilibrium (partitioning equilibrium) of the components between the resin-absorbed phase and the external liquid phase; (ii) the ionic exchange equilibria; (iii) an Eley–Rideal surface reaction mechanism. The developed kinetic model was able to correctly interpret all the experimental data collected, both as a function of the temperature and of the catalyst concentration.
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