base strength
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Author(s):  
Mohammad N. Karimi ◽  
Tobias Richter

AbstractWhen pursuing a controversial socio-scientific issue, readers are expected to construct balanced representations that include overlapping and opposing information. However, readers’ mental representations are often biased towards their prior beliefs. Previous research on such text-belief consistency effects have been conducted mostly in monolingual contexts. The present study investigated whether document language, as a source characteristic, moderates text-belief consistency effects at the situation-model and text-base representation levels. Eighty-seven bilingual readers—selected from a larger initial sample—read two documents on the global spread of English. The documents were either presented in participants’ first (Persian) and second (English) languages, or one was presented in Persian and the other one in English. A recognition task was used to assess situation-model strength and text-base strength. Overall, participants built stronger situation models for the belief-consistent information as opposed to belief-inconsistent information. However, document language moderated the text-belief consistency effect. When both texts were presented in English, the text-belief consistency effect was smaller than when both texts were presented in Persian. For the combination of English and Persian texts, the text-belief consistency effect was enlarged when the belief-consistent text was presented in English and the belief-inconsistent text in Persian but disappeared when the text-belief consistent text was presented in Persian and the belief-inconsistent text in English. These results suggest that document language can serve as a strong credibility cue that can eliminate belief effects, at least when the document language and the controversial issue are inherently related.


Synlett ◽  
2021 ◽  
Author(s):  
Reut Fallek ◽  
Natali Ashush ◽  
Amit Fallek ◽  
Moshe Portnoy

Two series of competitive acylation experiments with a polar and an apolar alcohol substrates, imitating two parts of amphiphilic diols, examined the influence of bases of varying strength on the substrate selectivity. While weakly basic 2,4,6-collidine only mildly accelerates the acylation of the polar substrate without affecting that of the apolar one, the acylation of both substrates is drastically hastened by strongly basic DBU. In both cases there is a notable, though not overwhelming, shift of the substrate selectivity towards the polar substrate, compared to the base-free acylation, which strongly favors that of the apolar one. The extraordinarily strong change in the substrate selectivity in favor of the polar substrate was induced, however, by aliphatic tertiary amine bases, DIPEA and TEA, of “Goldilocks” moderate base strength, which strongly accelerate the acylation of the polar substrate, while almost not affecting that of the apolar one. These effects of the bases on the substrate selectivity are reflected in the site selectivity trends observed in the acylation of a model diol amphiphile.


2021 ◽  
Author(s):  
Lulu Edwards ◽  
Haley Bell ◽  
Marcus Opperman

Research was conducted at the U.S. Army Engineer Research and Development Center (ERDC) in Vicksburg, MS, to identify alternative repair methods and materials for large crater repairs using Rapid Set Concrete Mix®. This report presents the technical evaluation of the field performance of full-depth slab replacement methods conducted using Rapid Set Concrete Mix® over varying strength foundations. The performance of each large crater repair was determined by using a load cart representing one-half of the full gear of a C-17 aircraft. Results indicate that using rapid-setting concrete is a viable material for large crater repairs, and the performance is dependent on surface thickness and base strength.


2021 ◽  
Vol 317 ◽  
pp. 251-256
Author(s):  
Lim Hong Hua ◽  
Fei Ling Pua ◽  
Rohaya Othman ◽  
Taufiq Yap Yun Hin ◽  
Sharifah Nabihah

Carbide lime is a result of acetylene production. Carbide lime made out of calcium hydroxide with minor amount of calcium carbonate. In this study, carbide lime was used as the raw material to synthesize a new base catalyst with high base strength. A strong base catalyst was prepared through calcination and impregnation with potassium fluoride. The structure and morphology of catalyst were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) The base strength was determined by Hammett Indicator test, temperature-programmed desorption of carbon dioxide (TPD-CO2). The surface area of the catalyst was determined by Brunauer-Emmet-Teller isotherm (BET). The catalytic performance was examined through transesterification reaction. Fatty acid methyl ester (FAME) was successfully synthesized with the presence of carbide lime derived catalyst. The highest biodiesel conversion rate for sunflower oil was 95.83% with 6 wt% of catalyst loading while palm oil was 88.07% with 3 wt% of catalyst loading. The presence of the ester functional group was determined by Fourier Transform Infrared Spectroscopy (FTIR) analysis.


2021 ◽  
Author(s):  
Helgard G. Raubenheimer ◽  
Selwyn F. Mapolie

Recent experimental and theoretical results for the title compounds are critically examined by means of interlinked thermodynamic cycles and observed trends in acid and base strength rationalized by using changes in simple chemical concepts.


Catalysts ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 707 ◽  
Author(s):  
Zhaobing Shen ◽  
Yejun Han ◽  
Yue Liu ◽  
Yejun Qin ◽  
Ping Xing ◽  
...  

The production of vinyl chloride (VCM) by pyrolysis of 1,2-dichloroethane (DCE) is an important process in the ethylene-based poly(vinyl chloride) industry. The pyrolysis is performed at temperatures above 500 °C, gives low conversions, and has high energy consumption. We have shown that N-doped carbon catalysts give excellent performances in DCE dehydrochlorination at 280 °C. The current understanding of the active sites, mechanism, and kinetics of DCE dehydrochlorination over N-doped carbon catalysts is limited. Here, we showed that pyridinic-N on a N-doped carbon catalyst is the active site for catalytic production of vinyl chloride monomer from DCE. The results of CO2 and DCE temperature-programmed desorption experiments showed that the pyridinic-N catalytic sites are basic, and the mechanism of dehydrochlorination on a N-doped carbon catalyst involves a carbanion. A kinetic study of dehydrochlorination showed that the surface reaction rate on the N-doped carbon catalyst was the limiting step in the catalytic dehydrochlorination of DCE. This result enabled clarification of the dehydrochlorination mechanism and optimization of the reaction process. These findings will stimulate further studies to increase our understanding of the relationship between the base strength and catalytic performance. The results of this study provide a method for catalyst optimization, namely modification of the amount of pyridinic-N and the base strength of the catalyst, to increase the surface reaction rate of DCE dehydrochlorination on N-doped carbon catalysts.


2020 ◽  
Vol 6 (19) ◽  
pp. eaax5331 ◽  
Author(s):  
Manuel F. Wagenhofer ◽  
Hui Shi ◽  
Oliver Y. Gutiérrez ◽  
Andreas Jentys ◽  
Johannes A. Lercher

Unsupported Ni-Mo sulfides have been hydrothermally synthesized and purified by HCl leaching to remove Ni sulfides. Unblocking of active sites by leaching significantly increases the catalytic activity for dibenzothiophene hydrodesulfurization. The site-specific rates of both direct (hydrogenolytic) and hydrogenative desulfurization routes on these active sites that consist of coordinatively unsaturated Ni and sulfhydryl groups were identical for all unsupported sulfides. The hydrogenative desulfurization rates were more than an order of magnitude higher on unsupported Ni-Mo sulfides than on Al2O3-supported catalysts, while they were similar for the direct (hydrogenolytic) desulfurization. The higher activity is concluded to be caused by the lower average electronegativity, i.e., higher base strength and polarity, of Ni-Mo sulfides in the absence of the alumina support and the modified adsorption of reactants enabled by multilayer stacking. Beyond the specific catalytic reaction, the synthesis strategy points to promising scalable routes to sulfide materials broadly applied in hydrogenation and hydrotreating.


METANA ◽  
2019 ◽  
Vol 15 (2) ◽  
pp. 57-64
Author(s):  
Setiarto Pratigto ◽  
Istadi Istadi ◽  
Dyah Hesti Wardhani

Penelitian ini akan mengkaji kinetika reaksi transesterifikasi minyak kedelai dengan metanol menggunakan katalis CaO dengan parameter rasio mol reaktan terhadap konversi metil ester yang digunakan untuk menentukan persamaan kecepatan reaksi. Katalis CaO digunakan untuk reaksi transesterifikasi karena memiliki kekuatan basa yang tinggi, ramah lingkungan, kelarutan yang rendah dalam metanol. Kinetika reaksi untuk reaktor batch dihitung saat reaksi berlangsung berdasarkan rejim surface area limited yang menentukan. Tujuan penelitian ini untuk mengetahui bentuk persamaan kecepatan reaksi transesterifikasi minyak kedelai dan metanol menggunakan katalis CaO menurut metode differential reactor. Penelitian dilakukan dengan reaksi transesterifikasi minyak kedelai dan metanol dengan katalis CaO dengan variabel bebas perbandingan mol reaktan. Hasil penelitian mengemukakan metanol teradsorpsi di permukaan katalis dan trigliserida tidak teradsorpsi di permukaan katalis menunjukkan mekanisme reaksi katalitik Eley-Rideal. Persamaan kecepatan reaksi dapat digunakan dalam perancangan reaktor, sehingga hubungan antara konversi trigliserida menjadi biodiesel dengan kebutuhan berat katalis dan volume reaktor yang diperlukan dapat diprediksi. This study will examine the kinetics of the transesterification reaction of soybean oil with methanol using a CaO catalyst with the parameters of the mole ratio of reactants to the conversion of methyl esters used to determine the reaction velocity equation. CaO catalyst is used for transesterification reaction because it has high base strength, environmentally friendly, low solubility in methanol. The reaction kinetics for a batch reactor are calculated when the reaction takes place based on a decisive surface area limited regime. The purpose of this study was to determine the shape of the speed equation for the transesterification of soybean oil and methanol using a CaO catalyst according to the differential reactor method. The research was carried out with the transesterification reaction of soybean oil and methanol with a CaO catalyst with a free variable ratio of reactant moles. The results of the study revealed that methanol adsorbed on the surface of the catalyst and triglycerides not adsorbed on the surface of the catalyst showed an Eley-Rideal catalytic reaction mechanism. The reaction speed equation can be used in reactor design, so the relationship between the conversion of triglycerides to biodiesel with the required catalyst weight and the reactor volume required can be predicted.


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