The present paper is an overview of the recent progress in the development of various CaO-based catalysts suitable for biodiesel production. The mechanism, kinetics and optimization of ...transesterification reaction over these catalysts are first considered. Then, the practical application of CaO-based catalysts is discussed with a special stress on leaching and reusability of these catalysts. Also, various continuous reactor systems currently in use for biodiesel production are appraised. In addition to it, purification of crude biodiesel and the ecological aspects of using CaO-based catalysts are considered. Finally, the potentials of CaO-based catalysts for heterogeneous catalysis for biodiesel production are emphasized to assess the future perspectives of their use. This review might help in selecting suitable CaO-based catalysts and the optimum reaction conditions for biodiesel production.
•Synthesis of vishnevite-type zeolite-like material (ZM) from waste fly ash (FA).•Use of waste chicken eggshell as an active component in the CaO/FA-ZM catalyst.•Methanol/oil molar ratio of 6:1 was ...found optimal in methanolysis over CaO/FA-ZM.•FAME content of 97.5% was achieved for 1 h under moderate reaction conditions.•Kinetics based on changing mechanism and TAG mass transfer limitation was proven.
The present paper is focused on the development of a new environment-friendly methanolysis catalyst completely based on waste materials: lignite coal fly ash and chicken eggshells. A novel catalyst based on CaO supported on a fly ash-based zeolitic material (CaO/FA-ZM) was obtained from a cancrinite-sodalite group zeolite-like material (vishnevite type) and active CaO by alkali activation in a new miniature autoclave reactor system and hydration-dehydration. Agitation by rotation of the entire reaction mixture led to a more homogeneous zeolitic product and saved both time and energy. The obtained catalyst structure corresponds to gismondine and the crystallographic modification of calcium silicate (α’-dicalcium silicate) with deposited CaO. The characteristics of the synthesized catalyst were determined using ED-XRF, XRD, FT-IR, SEM, Hg-porosimetry, N2-physisorption, LDPSA, and Hammett indicators. The CaO/FA-ZM catalyst exhibited a high activity (97.8% of FAME for only 30 min) and stability (a negligible drop in activity in five consecutive cycles) in the methanolysis reaction under the optimal reaction conditions (temperature of 60 °C, methanol/oil molar ratio of 6:1, and catalyst concentration of 6 wt%). A kinetic study was performed using two different mechanisms: the irreversible pseudo-first-order reaction mechanism in two regimes (heterogeneous and homogeneous) and the changing mechanism combined with the triacylglycerol mass transfer limitation. Both models showed a satisfactory agreement between the experimental and predicted values of conversion degree (R2 > 0.93), confirming their validity for the CaO-based heterogeneously catalyzed methanolysis. The values of the activation energy calculated for both mechanisms were 67.17 and 58.03 kJ mol−1, respectively.
A
bstract
We present results for the leading hadronic contribution to the muon anomalous magnetic moment due to strange quark-connected vacuum polarisation effects. Simulations were performed using ...RBC-UKQCD’s
N
f
= 2 + 1 domain wall fermion ensembles with physical light sea quark masses at two lattice spacings. We consider a large number of analysis scenarios in order to obtain solid estimates for residual systematic effects. Our final result in the continuum limit is
a
μ
(2)had,
s
= 53.1(9)(
− 3
+ 1
) × 10
− 10
.
Considering the current world crisis and definite future energy challenges,
biomass-to-fuel transformation is increasingly becoming important both to
the policy makers and to the industry. In this ...perspective, the valorisation
of oils and fats via transesterification/esterification reaction is an
attractive method for producing biodiesel with qualities suitable for diesel
engines. The recent interest indicated a significant shift to industrial
waste valorisation as another approach for achieving process eco-efficiency.
In this respect, the use of zeolite-based catalysts for the production of
biofuels is reviewed here, with a special emphasis on the utilization of
waste raw materials following the principles of green chemistry and
sustainable development. Zeolites are interesting due to their outstanding
catalytic properties, including the presence of intrinsic acid sites, simple
loading of base sites, shape-selectivity, and high thermal stability. Neat
zeolites or modified by the loading of active species are classified into
several groups following their origin. For each group, the most relevant
recent results reported in the literature are reviewed together with some
critical considerations on the catalyst effectiveness, stability,
reusability, and economy of synthesis. As an important part required for
understanding and optimization of the biodiesel production process, the
mechanisms of the reaction were discussed in detail. Finally, key
perspective directions for further research studies were carefully
identified and elaborated.
Display omitted
•Fly ash (FA) was converted into cancrinite zeolite (ZMFA) in a new rotating reactor.•Ultrasound-dispersion of eggshell CaO led to a uniform distribution over ZMFA.•Activation over ...550 °C led to the formation of non-active Ca-silicate.•Optimal CaO content was 20 wt% and corresponded to the highest catalyst basicity.•FAME content of 96.5% was achieved for 2 h under moderate methanolysis conditions.
Lignite coal fly ash (FA) from a domestic thermal power plant was converted into a pure cancrinite zeolitic material (ZMFA) using a novel, custom-made, rotating autoclave reactor system by a short-term alkali activation process. The obtained ZMFA was used as catalyst support of calcium oxide as an active component derived from waste chicken eggshells (ES). The ZMFA supported calcium oxide catalyst (xCaO/ZMFA) was synthesized by means of the ultrasound-assisted method. The influence of different concentrations of dispersed calcium oxide (x = 5–20 wt%) over ZMFA and thermal treatment at different temperatures (450–600 °C) were studied. The structural and morphological characterization showed that the original cancrinite structure was preserved. The basicity and textural properties indicated the presence of strong active sites in a well-defined pore network suitable for the reactions of bulky organic compounds such as triacylglycerols (TAGs). The highest activity (96.5% of fatty acid methyl esters) in the methanolysis of sunflower oil was achieved with the 20CaO/ZMFA catalyst under reaction conditions: temperature of 60 °C, methanol/oil molar ratio of 12:1, catalyst concentration of 4 wt%, and reaction time of 2 h. It was found that the optimal calcination temperature of the catalyst precursor was 550 °C. At calcination temperatures above 550 °C, the melting of the glassy phase became more intense whereby the molten phase partially reacted with calcium oxide forming the catalytically inactive calcium silicate compounds (wollastonite, larnite, etc.). The rate constants of the two tested kinetic models were correlated with the concentrations of active calcium oxide. The MRPD of both models was low indicating their reliability.
Introduction
Non functional parathyroid carcinoma (PC) is one of the rarest malignant neoplasms. Due to the lack of symptoms and laboratory findings, it is mostly diagnosed in late AQ2 stages, when ...local invasion and dissemination are already present. However, our case is an exception, because it was detected in early stage, with no local invasion present. We present a case of the smallest non-functional PC yet reported and review of the literature.
Case presentation
A 47-year-old woman was admitted to outpatient Clinic where fine-needle aspiration biopsy (FNAB) of bilateral thyroid nodules (slide 1) and central neck mass (slide 2), which was suspected to be an enlarged lymphatic nodule or parathyroid gland was performed. Results came back as Bethesda I-colloid (slide 1), and Bethesda IV (slide 2), stating that it is hard to distinguish thyroid gland oxyphil lesions from parathyroid cells. Total thyroidectomy was performed as well as excision of the left central neck mass, without any involvement of surrounding structures. Pathological examination revealed bilateral thyroid follicular nodular disease, papillary microcarcinoma, and parathyroid carcinoma with vascular and capsular invasion, measuring 10 × 8 × 7 mm. The immunohistochemical profile included positive PTH, Chromogranin A, and negative TTF1.
Conclusion
Non-functional PC is usually diagnosed in advanced stages, already involving adjacent structures; however, this case presents a rare example. It is important not to exclude PC as a differential diagnosis in the absence of elevated Ca and PTH serum levels. Follow-up will be difficult, since there are no prognostic parameters to rely on.
To research potential replacements for LiMn
2
O
4
, this work carries out a synthesis of ZnMn
2
O
4
(ZMO) through the glycine-nitrate combustion. XRPD validates its phase characterization; electron ...micro-scopy confirmed the presence of single phase ZMO in the form of curvy and rod-shaped sub-micron sized particles at an average of 113 nm. This work is novel for its electrochemical measurements of ZMO as a cathodic material for alkali-ion batteries, performed by cyclic voltammetry in aqueous solutions of ZnCl
2
and NaNO
3
ranging from 5 to 100 mV s
–1
polarization rates, yielding stable capacities for both electrolytes. The highest capacities were obtained for the polarization speed of 5 mV s
–1
for both electrolytes. Their cathode capacities were 11.3 and 27.2 mA h g
–1
for ZnCl
2
and NaNO
3
, respectively. Concerning Na-ions batteries, the surface storage is the deciding factor due to the adsorption of Na
+
ions on the λ-MnO
2
phase. Unlike Zn-ions, Na
+
ions cannot intercalate into the spinel structured materials.
Social networks constitute an intrinsic part of our lives, not only in private aspects, but also professional and academic ones. Digitalisation in various professional and scientific fields, web 2.0, ...universal mobility and the growing use of multimedia tools in the classroom have led to the use of social networks as teaching material and tools. In this work, the main social networks suitable for language teaching will be illustrated and various possibilities for their use will be indicated to derive maximum benefit from them in the classroom or during the student's independent study. Activities that may include the use of digital applications and the ways in which these platforms can be inserted into the different phases of the lesson will be indicated. Finally, various practical examples of the inclusion of social networks in the classroom will be given, accompanied by intentional reflections to encourage language teachers to include web 2.0 tools among their working methods.
A
bstract
We report on an exploratory study of domain wall fermions (DWF) as a lattice regularisation for heavy quarks. Within the framework of quenched QCD with the tree-level improved Symanzik ...gauge action we identify the DWF parameters which minimise discretisation effects. We find the corresponding effective 4
d
overlap operator to be exponentially local, independent of the quark mass. We determine a maximum bare heavy quark mass of
am
h
≈ 0
.
4, below which the approximate chiral symmetry and O(a)-improvement of DWF are sustained. This threshold appears to be largely independent of the lattice spacing. Based on these findings, we carried out a detailed scaling study for the heavy-strange meson dispersion relation and decay constant on four ensembles with lattice spacings in the range 2
.
0-5
.
7 GeV. We observe very mild
a
2
scaling towards the continuum limit. Our findings establish a sound basis for heavy DWF in dynamical simulations of lattice QCD with relevance to Standard Model phenomenology.
Background Rhythm control may improve functional capacity in patients with atrial fibrillation (AF). Long-term exercise tolerance improvement and its prognostic implications following ...catheter-ablation (CA) of paroxysmal and nonparoxysmal AF are underreported. Methods and Results Consecutive patients underwent cardiopulmonary exercise testing just before and 12 months after their index CA of AF. Follow-up 24-hour Holter recordings were obtained at 6-month intervals post-CA, and any atrial arrhythmia >30 seconds detected after 3 months postprocedure was considered AF recurrence. Of 110 patients (mean age 57.5±10.6 years, 77.2% males) with paroxysmal AF (n=66) or nonparoxysmal AF (n=44), the 12-month exercise tolerance improved significantly in those who maintained sinus rhythm during the first 12 months post-CA (n=96), but not in patients with AF recurrence (n=14). After CA, the 12-month respiratory exchange ratio at maximal workload significantly increased in patients with paroxysmal AF, whereas those with nonparoxysmal AF significantly reduced their heart rate during the 12-month cardiopulmonary exercise testing (all
≤0.001). During the follow-up of 42.8±7.8 months, a total of 29 patients (26.3%) experienced recurrent AF. On multivariate analysis including patients without recurrent AF at 12 months after CA, the extent of work time improvement at follow-up cardiopulmonary exercise testing was independently associated with the rhythm outcome beyond 12 months postprocedure (hazard ratio of 0.936 95% CI, 0.894-0.979 for each 10 seconds increase in the work time following ablation,
=0.004). Conclusions CA of AF was associated with recovery of exercise intolerance in patients with paroxysmal AF or nonparoxysmal AF. Inability to improve exercise capacity at 12 months post-CA was an independent risk factor for later AF recurrence.
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