Mechanisms of hydrodesulphurization catalyst aging

U ovom radu izvršena su ispitivanja deaktivacije katalizatora za hidrodesulfurizaciju (HDS), uz simulaciju starenja u laboratorijskim uslovima i paralelna ispitivanja katalizatora iz realnog industrijskog postrojenja. Širok interval uslova u laboratorijskoj simulaciji (temperatura, vreme tretmana, oksidacione i inertne atmosfere) pružio je osnov za ocenu uticaja različitih parametara na brzinu starenja katalizatora i definisanje kritičnih uslova, posebno pri regeneraciji katalizatora. Ispitivanja dva tipa HDS katalizatora, NiO-MoO3/y-Al2O3 i CoO- MoO3/y-Al2O3 i binarnih modelnih sistema NiO/ Al2O3, uz primenu komplementamih metoda za ispitivanje stukture i teksture čvrstih poroznih materijala, omogućila su uvid u mehanizme starenja u ovim složenim katalitičkim sistemima. Utvrđeno je da je oksidaciona atmosfera, posebno vodena para, kritičan faktor u kinetici stukturnih i teksturalnih promena u katalitičkom sistemu. Segregacija aktivne faze, interakcija sa nosačem, sinterovanje i gubitak aktivne faze iz sistema simultani su procesi koji dovode do trajne deaktivacije katalizatora. Visina radne temperature i moguća lokalna pregrevanja u sloju katalizatora, podstaknuta promenama difuzionih karakteristika kataličkog zrna, ključni su za destrukciju aktivne faze katalizatora, uz segregaciju prekursora oksidne faze molibdena, čiji je uticaj izrazit u fazi regeneracije. Intermedijarno prisustvo tečne faze oksida molidena, koja obliva površinu nosača, uslovljavajući intenzivno sinterovanje i ubrzanu interakciju izmedju ostalih faza u sistemu, predstavlja osnovni mehanizam u starenju katalizatora za HDS.Deactivation studies of hydrodesulphurization catalysts were performed, based on both aging simulation in laboratory conditions and investigation of catalysts from an industrial HDS plant. Broad interval of conditions applied in laboratory simulation (temperature, treatment duration, oxidation and inert atmospheres) was the basis for evaluating the effect of different parameters on catalyst aging kinetics and defining critical conditions, with emphasis on regeneration procedure. The investigations of two catalyst types, NiO-MoO3/y-Al2O3 and C0O-MoO3/y-Al2O3, and NiO/Al2O3 binary model systems, using complementary methods for structural and textural investigations of porous solid systems, enabled the insight in aging mechanisms of these complex catalytic systems. The oxidation atmosphere, especially water vapor, is critical for the rate of structural and textural changes in the catalysts. Segregation in active phase, interaction with the support, sintering and loss of active component from the catalyst are the simultaneous processes bringing about the irreversible deactivation of the catalyst. The temperature gradient in working conditions and possible formation of hot spots in catalyst reactor bed, affected also by changes of diffusion characteristics of catalyst grain, are crucial factors for segregation of molybdenum oxide precursor, which effect is pronounced during regeneration. The mechanism of HDS catalyst aging is based on intermediary presence of moIybdenum oxide liquid phase on the support surface, facilitating intensive sintering and interactions of other phases of catalytic system

Influence of detected NO2 and O3 on air quality of the city of Novi Sad

Within regular legislation of the Republic of Serbia, air quality monitoring is done on a daily basis, which we compared with the indicative measurement on a location which is in the vicinity of the measuring station “Novi Sad – Liman”. Location of the conducted indicative measurement is in the city park called “Liman park”. Mean values of the measured pollutant concentrations of O3 and NO2 were taken into account (the indicative measurements were done in a period of one hour). Both measuring points are located near the biggest boulevards which have a lot of traffic activity. Indicative measurements were done using the Aeroqual monitor with a GSE (gas sensitive electrochemical) sensor, while the comparative measurements were took by automatic measuring stations put out by the state. Such a comparison of the measured NO2 and O3 concentrations in the air of city of Novi Sad was not done before and it can give us insight into a possible harmful impact on the public health of the citizens of Novi Sad as well as the harmful impact on the environment. Results of the measurements pointed out the variations of air pollutant values; for O3 a 27.78% and for NO2 92.78% difference between the two locations that are 450 m apart from one another. The measurements were performed at the same time on the same day, temperature and relative humidity were nearly identical

Model assessment for groundwater quality with elevated arsenic content with application of fuzzy logic

Doktorska disertacija “Model procene kvaliteta podzemne vode sa povećanim sadržajem arsena primenom fazi logike” urađena je kao rezultat potrebe za istraživanjem mogućnosti primene fazi logike u savremenom pristupu procene kvaliteta podzemnih voda. Imajući u vidu da ova tematika nije dovoljno istražena u našem okruženju i da joj nije dat odgovarajući akcenat i težina, osnovni cilj disertacije je da se razrade optimalni modeli za procenu kvaliteta podzemnih voda sa povećanim sadržajem arsena. Disertacija pored teorijske dimenzije prezentuje i primenu evaluiranih fazi modela na primeru eksperimenatlno odabranog lokaliteta grada Zrenjanina. Razvijene modele je moguće transponovati na urbanim i ruralnim područjima uz odgovarajuće iteracije.PhD Thesis “Model assessment for groundwater quality with elevated arsenic content with application of fuzzy logic” was elaborated as a result of the need to explore the possibilities of application of fuzzy logic in the modern approach of assessing the groundwater quality. Because this issue has not been sufficiently explored and it was not given proper emphasis and weight, the main aim of the dissertation is to develop optimal models for assessing the groundwater quality with elevated arsenic content. Dissertation, besides theoretical dimensions, presente and evaluate the implementation of the created models to the experimentaly selected locality of the city of Zrenjanin. The developed models can be transposed to the urban and rural areas with appropriate iteration

Principle of opportunity of prosecution

Предмет рада је начело опортунитета кривичног гоњења и могућност његове примене у пракси. Ово начело је први пут уведено у Законик о кривичном поступку из 2001, који је ступио на снагу 28. марта 2002. гдоине, и у то време је представљао једну од најзначајнијих новина нашег кривичног процесног права. Уводећи начело опортунитета, законодавац је пре свега био мотивисан рационализацијом кривичног правосуђа и растерећењем судова, следећи тако општи светски тренд у кривичном процесном праву, обележен могућношћу договора између учесника у кривичном поступку и идејом рестораторне правде.The subject of this study is the principle of opportunity of prosecution and the possibilities of its application in practise. This principle was introduced for the first time in the Code of Criminal Procedure from 2001 that came into force as of March 28th 2002, and, at the time, it was one of the most significant novelties of our Criminal Procedural Law. The main lawmakers' motive for the introduction of the principle of opportunity was to rationalise the criminal justice and reduce the case overload in courts, at the same time following the general world trend in criminal procedural law marked by the idea of restorative justice

Air pollution in city parks during the Covid-19 pandemic

The degree of coverage of the urban greenspace area and the factors which affect the concentration of particles in the air in those limited greenspace areas are rarely studied, especially during the Covid-19 pandemic. This paper is based on researching the effects and different impacts of the microclimate parameters on the concentration of particulate matter (PM2.5 and PM10) in the studied city parks and their multidisciplinary impact on the most important aspect – The Public Health. In Novi Sad, Serbia, three parks of different sizes and locations have been chosen, depending on the traffic frequency. The measurement results of particle pollution (PM) pointed out the variations of levels of concentration of the PM pollutants, PM2.5 particles were in range from 2 to 10 μg/m3 and PM10 were in range from 3 to 12 μg/m3 . Some of the measured values are exceptionally low so it can be concluded that the air was clean. The time of the measurements of the PM pollutants in the parks was in a period from 11a.m to 2 p.m., with temperature oscillation between 15o -24.3oC and air humidity from 41-50%

Formaldehyde in screen printing indoor

The presence of formaldehyde in air samples has been detected in five screen printing facilities in Novi Sad, Serbia. Air samples were sampled continuously during 4 hours, and concentration levels of formaldehyde was determined by UV-VIS spectrometry at 580 nm. The range of formaldehyde concentrations was from 0.413 to 0.836 ppm. Comparison of the detected concentration levels with the permissible exposure limit of 0.75 ppm (the OSHA standard) indicated that the formaldehyde concentration in facility 5 was 1.11 times higher than prescribed value

Cadmium in industrial wastewater

The concentration of cadmium in the industrial wastewater discharged from the aluminium and copper metal processing industry was analysed. The samples of water and sediment were taken from the Dragića Stream and the river Đetinja, downstream from the place where the wastewater from the metalworking industry flows into the Dragića Stream. According to the measured metal concentrations in the water and pursuant to the Regulations on Hazardous Substances in Water, issued by the Republic of Serbia, the water from the Dragića Stream belongs to the II class. Based on the obtained results, it was determined that the amount of metals in the water samples taken during the spring/summer season was relatively low, and that cadmium was dominantly present in the sediment

Analysis of consumers' willingness to pay for organic and local honey in Serbia

In times of increased concern for human health and care for the environment, it is important to investigate the consumer behavior models in order to better manage the product supply. From the perspective of our research, it is important to learn about consumer attitudes, of a specific product, such as honey, so as to potentially strengthen the economic position of honey producers. The purpose of this article was to explore the consumers' perceptions of organic and local honey in the Republic of Serbia and identify factors that contribute to predicting consumers' willingness to pay (WTP) for organic and local honey. The ordinal regression was used to determine which factors influence the WTP for organic and local honey, and the findings show that the consumers were WTP more for organic honey than for local honey. Socio-economic characteristics of respondents and honey attributes affect consumers' WTP. The higher monthly household income positively influences the WTP for organic honey, while on the other hand, the higher level of education has a positive influence on the WTP for local honey. The WTP for organic honey positively affected by the perceived importance of honey attributes, such as food safety and support for the local community. The frequency of the purchase of the local honey, the recommendations for the local honey purchase and the perceived importance of attributes, such as the care for the environment and nutritional properties, have a positive influence on the consumers' WTP for local honey. From this, we can conclude that our understanding of all the factors that influence a consumer's decision to allocate budget expenses for honey can help all stakeholders in creating an adequate pricing and promotional strategy for honey products

Wastewater characterisation of screen printing

The paper presents a preliminary investigation of wastewater quality in screen printing facilities in Novi Sad. The experimental research includes two selected parameters: pH value and BOD. The measured pH values were in the range of maximum allowed values, but very high BOD values indicate dominant organic pollution. Determined BOD values of collected samples were in the range from 36 - 206 mg/1. These BOD values show great organic pollution of wastewater from screen printing facilities with biodegradable organic matter

Rural Revival Financing in Serbia: Kikinda Municipality Case Study

In Serbia, similar to other European countries, towns grow, while villages lose population and fertile land disappears. Identification of potential resources for rural revival financing represents a research challenge. The aim of this paper is to evaluate Kikinda municipal budget increase as potential financial resource for revival of villages around Kikinda. New communal company in Kikinda, formed recently by five old communal companies merging, not only provides good services, but also enlarges municipal budget. In this paper, following Serbia rural features review, Kikinda Town and surrounding villages are briefly described. Prosperous village of Mokrin, once train station for the Orient Express, is presented in more detail. Then Kikinda Municipality budget is analyzed. Conclusion is that if the municipal budget surplus exists, small farming holdings can be financially supported to start modern food production. In Kikinda Municipality case, however, existing budget surplus is not sufficient for generous financial support yet