scholarly journals Cobalt-lanthanum catalyst precursors for ammonia synthesis: determination of calcination temperature and storage conditions

2017 ◽  
Vol 19 (2) ◽  
pp. 61-66 ◽  
Author(s):  
Magdalena Zybert ◽  
Aleksandra Tarka ◽  
Bogusław Mierzwa ◽  
Wioletta Raróg-Pilecka

Abstract A thermal decomposition of a cobalt-lanthanum catalyst precursor containing a mixture of cobalt and lanthanum compounds obtained by co-precipitation were studied using thermal analysis coupled with mass spectrometry (TG-MS). Studies revealed that the calcination in air at 500°C is sufficient to transform the obtained cobalt precipitate into Co3O4, but it leads to only partial decomposition of lanthanum precipitate. In order to obtain Co/La catalyst precursor containing La2O3 the calcination in air at the temperature about 800°C is required. However, it is unfavorable from the point of view of textural properties of the catalyst precursor. A strong effect of storage conditions on the phase composition of the studied cobalt-lanthanum catalyst precursor, caused by the formation of lanthanum hydroxide and lanthanum carbonates from La2O3 when contacting with air, was observed.

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Alice F. Charteris ◽  
Karina A. Marsden ◽  
Jess R. Evans ◽  
Harry A. Barrat ◽  
Nadine Loick ◽  
...  

AbstractIn grazing systems, urine patches deposited by livestock are hotspots of nutrient cycling and the most important source of nitrous oxide (N2O) emissions. Studies of the effects of urine deposition, including, for example, the determination of country-specific N2O emission factors, require natural urine for use in experiments and face challenges obtaining urine of the same composition, but of differing concentrations. Yet, few studies have explored the importance of storage conditions and processing of ruminant urine for use in subsequent gaseous emission experiments. We conducted three experiments with sheep urine to determine optimal storage conditions and whether partial freeze-drying could be used to concentrate the urine, while maintaining the constituent profile and the subsequent urine-derived gaseous emission response once applied to soil. We concluded that filtering of urine prior to storage, and storage at − 20 °C best maintains the nitrogen-containing constituent profile of sheep urine samples. In addition, based on the 14 urine chemical components determined in this study, partial lyophilisation of sheep urine to a concentrate represents a suitable approach to maintain the constituent profile at a higher overall concentration and does not alter sheep urine-derived soil gaseous emissions.


2015 ◽  
Vol 4 (3) ◽  
pp. 56 ◽  
Author(s):  
Alexandr Ya Yashin ◽  
Boris V. Nemzer ◽  
Emilie Combet ◽  
Yakov I. Yashin

<p>Despite the fact that mankind has been drinking tea for more than 5000 years, its chemical composition has been studied only in recent decades. These studies are primarily carried out using chromatographic methods. This review summarizes the latest information regarding the chemical composition of different tea grades by different chromatographic methods, which has not previously been reviewed in the same scope. Over the last 40 years, the qualitative and quantitative analyses of high volatile compounds were determined by GC and GC/MS. The main components responsible for aroma of green and black tea were revealed, and the low volatile compounds basically were determined by HPLC and LC/MS methods. Most studies focusing on the determination of catechins and caffeine in various teas (green, oolong, black and pu-erh) involved HPLC analysis.</p> <p>Knowledge of tea chemical composition helps in assessing its quality on the one hand, and helps to monitor and manage its growing, processing, and storage conditions on the other. In particular, this knowledge has enabled to establish the relationships between the chemical composition of tea and its properties by identifying the tea constituents which determine its aroma and taste. Therefore, assessment of tea quality does not only rely on subjective organoleptic evaluation, but also on objective physical and chemical methods, with extra determination of tea components most beneficial to human health. With this knowledge, the nutritional value of tea may be increased, and tea quality improved by providing via optimization of the growing, processing, and storage conditions.</p>


2010 ◽  
Vol 46 (Special Issue) ◽  
pp. S90-S95 ◽  
Author(s):  
V. Dvořáček ◽  
D. Janovská ◽  
L. Papoušková ◽  
E. Bicanová

A triennial evaluation of the content of titratable acids (TA) in grain was carried out on 12 varieties of proso millet (<I>Panicum miliaceum </I>L.). The model variety, Mironovskoe 94, harvested in 2004, was used for the monitoring of sensory changes in TA content, in relationship to different storage conditions and the application of different grain processing methods. The Czech state norm (CSN 56 0512-9 1995) Determination of Titratable Acids, with a slight modification, was used as the standard method. The TA contents in dry matter varied between 39 and 78 mmol/kg of grain dry matter, and significant differences between varieties and experimental years were found. The method of proso millet processing had a key role in the final sensitivity to rancidity. The storage conditions had a much lower influence on TA content than the processing technology. The clearly detected sensory changes found in scoured grains corresponded with TA contents within the range of 90 to106 mmol/kg. The monitoring of the TA content can be considered as a suitable tool for the prediction of rancidity processes in millet grains.


2019 ◽  
Vol 62 (3) ◽  
pp. 661-671 ◽  
Author(s):  
Jia Wu ◽  
Xiangyang Lin ◽  
Shengnan Lin ◽  
Paul Chen ◽  
Guangwei Huang ◽  
...  

Abstract. The effects of packaging and storage conditions on the moisture content and instrumental and sensory textural properties of raw and salty light roasted (SLR) California almonds were studied under different storage conditions. The controlled combinations included low, medium, and high temperatures and low and high relative humidity (RH). Almond samples were packaged in cartons or polyethylene (PE) bags with and without vacuum. Both absorption and desorption of moisture by almonds were observed during storage and were dependent on the packaging and storage conditions. In general, gradual changes were observed for samples with PE and vacuum PE packaging in most of the storage conditions, while the samples packed in cartons showed more dramatic changes because these unprotected samples were more vulnerable to seasonal changes in humidity. The SLR almonds showed consistent moisture gains, while the raw almonds tended to lose moisture content in most of the storage conditions. This may be attributed to the low initial moisture content of the SLR samples. All raw samples packed in cartons became softer over time. The softening tended to be enhanced by high storage humidity and temperature. The raw almonds packaged in PE bags were firmer than those packed in cartons but also became softer over time. The firmness of the SLR samples was generally lower than that of raw samples, probably because roasting reduced the density and mechanical strength of the kernels. The firmness of PE packaged SLR samples increased in uncontrolled storage conditions and in higher storage temperature and humidity conditions but decreased slightly in lower temperature and humidity conditions. Vacuum packaging did not affect the firmness much. Using PE packaging and maintaining the RH below 50% and the temperature below 25°C are effective in stabilizing both raw and processed almonds. Keywords: Almond, Firmness, Nonpareil, Packaging, Relative humidity, Sensory, Storage, Temperature, Texture.


2019 ◽  
Vol 30 (2) ◽  
pp. 219-226
Author(s):  
S Arefin ◽  
MHR Bhuiyan ◽  
N Yeasmen ◽  
MA Islam ◽  
M Shams Ud Din

This paper attempts to show the effect of preservatives and storage on the chemical, sensorial and microbial aspect of ready to use (RtU) onion paste, stored at two conditions i.e. ambient temperature (AT: 30±30C) and refrigerated temperature (RT: 5±10C) over a period of 180 days after treating with preservatives i.e. Potassium metabisulphites (KMS), Sodium benzoate (SB) and Citric acid (CA) at two levels i.e. 750 and 1000 ppm respectively. In the context of chemical aspect, a throughout observations over 180 days with 60 days interval showed negligible changes in chemical constituents of RtU onion paste both at AT and RT conditions with a little exception. Over the period pH slightly increased for both the storage conditions. Towards the sensorial point of view, use of preservatives in RtU onion paste resulted in the acceptance of color, flavor and texture up to 60 and 120 days of storage at AT and RT, respectively. To improve the effect of preservatives, mixture of them (KMS & CA; SB & CA) was also applied into to the sample (onion paste) besides the individual application. As a consequence, sensorial quality was better sustained by the addition of CA (0.8%) with other preservatives in comparison to the samples without CA. Onion paste, in specific, treated with 1000 ppm KMS & 0.8% citric acid stored both at AT and RT condition retained the most acceptable quality attributes compared to other treatments. However, onion paste without any preservative (control) was found acceptable only up to 20 days of storage at RT while storage at AT condition resulted in the more worse situation (acceptable up to 5 days). Total bacterial count was found in the lowest amount in RtU onion paste treated with the combination of KMS (1000 ppm) and CA (0.8%). Progressive Agriculture 30 (2): 219-226, 2019


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