scholarly journals The guiding role of pre-coking on the coke deposition over ZSM-5 in methanol to propylene

2019 ◽  
Vol 6 (9) ◽  
pp. 190218 ◽  
Author(s):  
Lin Wang ◽  
Jing Qi ◽  
Hongqiao Jiao ◽  
Liangcheng An ◽  
Chong Guan ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermogravimetric Analysis ◽  
Methanol Conversion ◽  
Acid Sites ◽  
Coke Deposition ◽  
Steam Treatment ◽  
Elementary Analysis ◽  
Before And After ◽  
Propylene Selectivity

Deposition of carbonaceous compounds was used to improve the propylene selectivity of ZSM-5 by deactivating some acid sites meanwhile maintaining the high activity for methanol conversion. The carbonaceous species of pre-coked samples before and after MTP reactions were investigated by elementary analysis and thermogravimetric analysis (TGA). The results showed that pre-coke formed at low temperature (250°C) was unstable and easy to transform into polyaromatics species at the high reacting temperature, while combining 5% pre-coking process with 95% steam treatment at high temperature (480°C) was effective in inhibiting the formation of coke deposits and presented a significant improvement in the propylene selectivity.

scholarly journals Oxidation of Ethanol in Cu-Faujasites Studied by IR Spectroscopy

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2669
Author(s):  
Łukasz Kuterasiński ◽  
Jerzy Podobiński ◽  
Jerzy Datka
Keyword(s):  
Ethanol Oxidation ◽  
Produced Water ◽  
Acid Sites ◽  
No Adsorption ◽  
Ir Studies ◽  
Oxygen Donor ◽  
Before And After ◽  
Acetate Formation ◽  
Back Donation

In this study, IR studies of the coadsorption of ethanol and CO on Cu+ cations evidenced the transfer of electrons from ethanol to Cu+, which caused the lowering of the frequency of the band attributed to CO bonded to the same Cu+ cation due to the more effective π back donation of d electrons of Cu to antibonding π* orbitals of CO. The reaction of ethanol with acid sites in zeolite HFAU above 370 K produced water and ethane, polymerizing to polyethylene. Ethanol adsorbed on zeolite Cu(2)HFAU containing acid sites and Cu+exch also produced ethene, but in this case, the ethene was bonded to Cu+ and did not polymerize. C=C stretching, which is IR non-active in the free ethene molecule, became IR active, and a weak IR band at 1538 cm−1 was present. The reaction of ethanol above 370 K in Cu(5)NaFAU zeolite (containing small amounts of Cu+exch and bigger amounts of Cu+ox, Cu2+exch and CuO) produced acetaldehyde, which was further oxidized to the acetate species (CH3COO-). As oxygen was not supplied, the donors of oxygen were the Cu species present in our zeolite. The CO and NO adsorption experiments performed in Cu-zeolite before and after ethanol reaction evidenced that both Cu+ox and Cu2+ (Cu2+exch and CuO) were consumed by the ethanol oxidation reaction. The studies of the considered reaction of bulk CuO and Cu2O as well as zeolites, in which the contribution of Cu+ox species was reduced by various treatments, suggest that ethanol was oxidized to acetaldehyde by Cu2+ox (the role of Cu+ox could not be elucidated), but Cu+ox was the oxygen donor in the acetate formation.

scholarly journals Influence of PPA on the Short-Term Antiaging Performance of Asphalt

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Lining Gao ◽  
Nana Cai ◽  
Xiaohong Fu ◽  
Rui He ◽  
Honggang Zhang ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
High Temperature ◽  
High Performance ◽  
Main Function ◽  
Short Term ◽  
Temperature Resistance ◽  
Modified Asphalt ◽  
High Temperature Resistance ◽  
Before And After

It has been confirmed that polyphosphoric acid (PPA) can significantly improve the high-temperature resistance, storage stability, and aging resistance of asphalt. The low price of PPA is conducive to the development of modified asphalt with high performance and excellent economy, suggesting its great application prospects. At present, there is little research on the role of PPA in delaying the aging process of PPA-modified asphalt, and a consensus has not yet been reached. Therefore, PPA-modified asphalt with different blending amounts (0 wt%, 0.4 wt%, 0.8 wt%, and 1.2 wt%) was prepared in this study. On the basis of variable performance, the role of PPA in the short-term antiaging process of asphalt is analyzed through Fourier transform infrared spectroscopy (FTIR) analysis of PPA-modified asphalt before and after aging, combined with the analysis of the change in components. The results showed that after PPA addition, the high-temperature resistance and the thermal stability of asphalt were improved and the temperature sensitivity was weakened. Both curves of ductility and G ∗ indicate the potential saturation effect of PPA addition; together with infrared spectroscopy, we proved that there are both chemical reactions and physical mixing in the PPA-modified asphalt. The component fractions show that PPA will cause the asphalt to transform from sol to gel and the main function of PPA in retarding asphalt aging is the dispersion of the agglomerates of asphaltene micelles by PPA.

Synthesis and Modification of SAPO-34 Nanoparticles by Incorporation of Metal Ions Using Rapid High Temperature Method

2013 ◽  
Vol 829 ◽  
pp. 627-631 ◽  
Author(s):  
Mohammad Hasan Dadjoo ◽  
Rouein Halladj ◽  
Sima Askari ◽  
Shadi Jalili
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
High Temperature ◽  
Synthesis Method ◽  
Diffusion Path ◽  
Methanol Conversion ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Strength Distribution ◽  
Synthesis Time

Considering studies done on the result of methanol conversion over SAP-34 molecular sieve, it is understood that increase of selectivity is ascribed to the increase of acidity in acid sites which is a result of incorporation of metal in crystal structure and decrease of crystal size. In this study, metal incorporation in the SAPO-34 structure leaded to increase of acid sites concentration but did not affect the acid strength distribution. The catalytic performance of the SAPO-34 nanoparticles in the MTO reaction varied according to their crystallite size. Decreasing particle size results in larger increase of external surface area and shorter diffusion path, both cause reduction in mass and heat transfer resistances in catalysis and sorption. In this work a rapid high-temperature synthesis method was developed to synthesis uniform nanoparticles of SAPO 34 zeolite with high crystallinity and metal was successfully incorporated in crystal structure. In order to investigate the effects of temperature and synthesis time on purity and crystallinity of the synthesized samples, the crystallization temperature was increased from 350 to 550 K while the synthesis time was decreased from 24 h to 45 min. The samples were characterized by XRD, BET and SEM analysis techniques. It was found that by using high temperature and short synthesis time the particle size decreased and the metal was properly incorporated into the crystal structure.

The Role of MoO3 and Fe2O3 in the Thermal Decomposition of Ammonium Perchlorate

1994 ◽  
Vol 59 (10) ◽  
pp. 2253-2261 ◽  
Author(s):  
Samih A. Halawy ◽  
Mohamed A. Mohamed
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
High Temperature ◽  
Thermogravimetric Analysis ◽  
Surface Area ◽  
Ammonium Perchlorate ◽  
Bet Method ◽  
Xrd Techniques

The effect of addition of MoO3 and Fe2O3 as well as mixtures of the two oxides (calcined in air at 500 °C) on the thermal decomposition of ammonium perchlorate (AP) was studied using thermogravimetry (TGA) and derivative thermogravimetric analysis (DTG). The catalysts calcined at 500 °C were characterized using TPR, XPS and XRD techniques. The surface area of the catalysts was determined by means of the conventional BET method. The results are discussed in terms of the recently published mechanism in which nitryl perchlorate is supposed as an intermediate in the thermal decomposition of pure AP. The correlation between the surface area and activity of the catalysts in the thermal decomposition of AP has been done. The activation energy (∆E) for non-catalyzed and catalyzed high-temperature thermal decomposition of AP were calculated from the TGA results using the Coats-Redfern equation.

Modelling of catalysts and its relation to experimental problems

1992 ◽  
Vol 341 (1661) ◽  
pp. 255-268 ◽  
Keyword(s):  
Small Molecules ◽  
Active Sites ◽  
Thermal Activation ◽  
Porous Metal ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Before And After ◽  
Porous Metal Oxides ◽  
And Diffusion

We illustrate the role of both computer simulation and the evaluation of electronic structure in the study of solid heterogeneous catalysis by reference to recent work in this laboratory on ( a ) microporous materials (that have a spatially uniform distribution of accessible active sites) and ( b ) non-porous metal oxides. Computational methodologies may be used to model, first, the structure of the uniform catalysts both before and after thermal activation, second, the docking and diffusion of molecules in solids and on their surfaces; and, third, the reaction pathways of molecules at the active site. We highlight recent successes in modelling (i) the structures of zeolitic solids, (ii) the sorption of hydrocarbons within them, (iii) the protonation of small molecules at the Bronsted acid sites in uniform solid acid (zeolite) catalysts, and (iv) the reactions of small molecules on CeO 2 and MgO surfaces.

scholarly journals A Supramolecular View on the Cooperative Role of Brønsted and Lewis Acid Sites in Zeolites for Methanol Conversion

2019 ◽  
Vol 141 (37) ◽  
pp. 14823-14842 ◽  
Author(s):  
Simon Bailleul ◽  
Irina Yarulina ◽  
Alexander E. J. Hoffman ◽  
Abhay Dokania ◽  
Edy Abou-Hamad ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Methanol Conversion ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Brønsted And Lewis Acid

Child and Adolescent Suicides in Bosnia and Herzegovina Before and After the War (1992–1995)

Crisis ◽  
2010 ◽  
Vol 31 (3) ◽  
pp. 160-164 ◽  
Author(s):  
Almir Fajkic ◽  
Orhan Lepara ◽  
Martin Voracek ◽  
Nestor D. Kapusta ◽  
Thomas Niederkrotenthaler ◽  
...  
Keyword(s):  
Bosnia And Herzegovina ◽  
Age Differences ◽  
Suicide Risk ◽  
Child And Adolescent ◽  
Youth Suicide ◽  
Southeastern Europe ◽  
Suicide Rates ◽  
Before And After ◽  
Sex And Age Differences

Background: Evidence on youth suicides from Southeastern Europe is scarce. We are not aware of previous reports from Bosnia and Herzegovina, which experienced war from 1992 to 1995. Durkheim’s theory of suicide predicts decreased suicide rates in wartime and increased rates afterward. Aims: To compare child and adolescent suicides in Bosnia and Herzegovina before and after the war. Methods: Data on youth suicide for prewar (1986–90) and postwar (2002–06) periods were analyzed with respect to prevalence, sex and age differences, and suicide methods. Suicide data from 1991 through 2001 were not available. Results: Overall youth suicide rates were one-third lower in the postwar than in the prewar period. This effect was most pronounced for girls, whose postwar suicide rates almost halved, and for 15–19-year-old boys, whose rates decreased by about a one-fourth. Suicides increased among boys aged 14 or younger. Firearm suicides almost doubled proportionally and were the predominant postwar method, while the most common prewar method had been hanging. Conclusions: The findings from this study indicate the need for public education in Bosnia and Herzegovina on the role of firearm accessibility in youth suicide and for instructions on safe storage in households. Moreover, raising societal awareness about suicide risk factors and suicide prevention is needed.

Strategic Role of Zakat in Multidimensional Quality of Life in Sijunjung, Indonesia

2018 ◽  
Vol 15 (1) ◽  
pp. 55-72
Author(s):  
Herlin Hamimi ◽  
Abdul Ghafar Ismail ◽  
Muhammad Hasbi Zaenal
Keyword(s):  
Quality Of Life ◽  
Positive Impact ◽  
Wealth Distribution ◽  
Absolute Poverty ◽  
Before And After ◽  
The Status ◽  
Being There ◽  
The Impact

Zakat is one of the five pillars of Islam which has a function of faith, social and economic functions. Muslims who can pay zakat are required to give at least 2.5 per cent of their wealth. The problem of poverty prevalent in disadvantaged regions because of the difficulty of access to information and communication led to a gap that is so high in wealth and resources. The instrument of zakat provides a paradigm in the achievement of equitable wealth distribution and healthy circulation. Zakat potentially offers a better life and improves the quality of human being. There is a human quality improvement not only in economic terms but also in spiritual terms such as improving religiousity. This study aims to examine the role of zakat to alleviate humanitarian issues in disadvantaged regions such as Sijunjung, one of zakat beneficiaries and impoverished areas in Indonesia. The researcher attempted a Cibest method to capture the impact of zakat beneficiaries before and after becoming a member of Zakat Community Development (ZCD) Program in material and spiritual value. The overall analysis shows that zakat has a positive impact on disadvantaged regions development and enhance the quality of life of the community. There is an improvement in the average of mustahik household incomes after becoming a member of ZCD Program. Cibest model demonstrates that material, spiritual, and absolute poverty index decreased by 10, 5, and 6 per cent. Meanwhile, the welfare index is increased by 21 per cent. These findings have significant implications for developing the quality of life in disadvantaged regions in Sijunjung. Therefore, zakat is one of the instruments to change the status of disadvantaged areas to be equivalent to other areas.

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