Thermal and structural analysis of the reaction pathways of α-spodumene with NH4HF2

Resentera, Alexander C.; Rosales, Gustavo D.; Esquivel, M.R.; Rodríguez, M. H.

doi:10.1016/j.tca.2020.178609

Cited by 28 publications

(17 citation statements)

References 37 publications

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“…This value was calculated as 18.12 % in the case of NiOxal, and then gradually increased from 19.19 up to 27.77 % due to the addition of 1-10 % F À as AHDF to NiOxal. These gradual increments could be associated with the complete decomposition of AHDF in the temperature range of 90-222°C, [26] as represented by Equation [2]: NH 4 F:HF ! NH 3 " þ2 HF "…”

Section: Thermal Analysesmentioning

confidence: 99%

“…60.4 m 2 .g À 1 ) followed by a gradual increase to 74.1 and 87.1 m 2 .g À 1 , with the addition of 5 and 10 wt % F À , respectively. This could be related to the evolution of both HF and NH 3 [26] as presented by Equation [2] during the calcination process of these samples. On the contrary, a significant contraction of the surface area had resulted with the consequence additions of 1-10 wt % K 2 O to NiO, see Table 3, where the smallest S BET value was measured for NiO-10 wt % K 2 O (ca.…”

Section: S Bet Measurement and Morphologymentioning

confidence: 99%

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Boosting NiO Catalytic Activity by x wt % F‐ions and K₂O for the Production of Methyl Ethyl Ketone (MEK) via Catalytic Dehydrogenation of 2‐Butanol

et al. 2021

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Herein, the synthesis of pure and modified mesoporous nanocrystalline NiO is reported. The catalyst was modified with different wt % F-ions or K 2 O and used to produce Methyl ethyl ketone (MEK) as a potential fuel/solvent. XRD analysis of the promoted catalysts confirmed the formation of Ni-metal covered by the host oxide, compared with pure NiO, especially for the promoted catalysts with x wt % F-ions. CO 2 -TPD results demonstrated the existence of different basic sites over these catalysts with varying strength. The catalytic conversion of sec-butanol (SB) into MEK over the parent NiO catalyst showed 52 % and 76.8 % conversion of SB at 250 and 275°C, respectively, with higher selectivity to MEK > 96 %. Among the promoted catalysts, NiO-10 wt % F À and NiO-1 wt % K 2 O catalysts showed 99 and 95 % conversion, respectively, with retaining the MEK selectivity of � 96 %. The catalytic activity, of the most active catalysts, was correlated with the presence of Ni/NiO interfaces, different types of basic sites, especially strong basic sites, and the surface area and porosity measurements.

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Section: Thermal Analysesmentioning

confidence: 99%

Section: S Bet Measurement and Morphologymentioning

confidence: 99%

Boosting NiO Catalytic Activity by x wt % F‐ions and K₂O for the Production of Methyl Ethyl Ketone (MEK) via Catalytic Dehydrogenation of 2‐Butanol

et al. 2021

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“… 52 The calculated values of the surface area ( S BET ) and the corresponding values of the external surface area of samples calcined at 400 °C, as shown in Table 1 , were approximately 1.4–1.5 times higher than those calcined at 500 °C, except for samples containing 50% F, which experienced a clear reduction in the surface area. The gradual decrease of the surface area of all samples with the increase in the added amounts of ( x )% F as NH 4 F·HF is probably due to the melting of this fluorinating agent 41 at an early stage in the calcination process of these mixtures. This phenomenon has caused the surface area of all samples calcined for 3 h at 400 and 500 °C to decrease.…”

Section: Resultsmentioning

confidence: 95%

“…Due to the liberation of physically adsorbed water molecules associated with Mg(OH) 2 , these values exceeded the theoretical value − for the conversion of anhydrous Mg(OH) 2 to MgO (ca. 30.86%), as presented in eq : normalM normalg false( OH false) 2 → normalM normalg normalO + normalH 2 normalO on the other hand, NH 4 F·HF undergoes melting at 125 °C, followed by a subsequent fast step due to its decomposition around 150 °C, as shown in eq : normalN normalH 4 normalF · normalH normalF → normalN normalH 3 + 2 normalH normalF the TG profiles of the mixed samples can be divided into four temperature zones, as shown in Figure . The first zone in the temperature range RT–150 °C, includes both melting and decomposition of AHDF (see eq ).…”

Section: Resultsmentioning

confidence: 99%

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Mg–O–F Nanocomposite Catalysts Defend against Global Warming via the Efficient, Dynamic, and Rapid Capture of CO₂ at Different Temperatures under Ambient Pressure

et al. 2022

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The utilization of Mg−O−F prepared from Mg(OH) 2 mixed with different wt % of F in the form of (NH 4 F•HF), calcined at 400 and 500 °C, for efficient capture of CO 2 is studied herein in a dynamic mode. Two different temperatures were applied using a slow rate of 20 mL•min −1 (100%) of CO 2 passing through each sample for only 1 h. Using the thermogravimetry (TG)-temperature-programed desorption (TPD) technique, the captured amounts of CO 2 at 5 °C were determined to be in the range of (39.6−103.9) and (28.9−82.1) mg COd 2 •g −1 for samples of Mg(OH) 2 mixed with 20−50% F and calcined at 400 and 500 °C, respectively, whereas, at 30 °C, the capacity of CO 2 captured is slightly decreased to be in the range of (32.2−89.4) and (20.9− 55.5) mg COd 2 •g −1 , respectively. The thermal decomposition of all prepared mixtures herein was examined by TG analysis. The obtained samples calcined at 400 and 500 °C were characterized by X-ray diffraction and surface area and porosity measurements. The total number of surface basic sites and their distribution over all samples was demonstrated using TG-and differential scanning calorimetry-TPD techniques using pyrrole as a probe molecule. Values of (ΔH) enthalpy changes corresponding to the desorption steps of CO 2 were calculated for the most active adsorbent in this study, that is, Mg(OH) 2 + 20% F, at 400 and 500 °C. This study's findings will inspire the simple preparation and economical design of nanocomposite CO 2 sorbents for climate change mitigation under ambient conditions.

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A novel low‐energy approach to leucoxene concentrate desiliconization by ammonium bifluoride solutions

Смороков

Kantaev

Bryankin

et al. 2022

J of Chemical Tech & Biotech

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BACKGROUND: Despite the large reserves of titanium ores, their treatment by basic approaches to obtain titanium products is not always economically feasible due to various factors. One of these problems is the high content of silicon in the ores. RESULTS:The paper considers the desiliconization of a leucoxene concentrate with an aqueous solution of ammonium bifluoride. It was found that at 80 °C the main impurities, such as silicon and iron, pass into solution in the form of corresponding ammonium-fluorine complex compounds.CONCLUSIONS: The degree of desiliconization was up to 99%. Aluminium reacts with ammonium bifluoride, but is almost not leached into solution due to its low solubility. Titanium does not react due to its relatively higher reaction Gibbs energy among other metals in reaction with ammonium bifluoride. The content of titanium oxide in the calcined leaching residue was 85.52 wt%. The resulting residue corresponds to the raw material used in industry for the production of titanium dioxide pigment or titanium metal by the chlorine method. Iron and silicon can be precipitated from the leaching solution. Furthermore, the resulting filtrate can be evaporated in order to regenerate and reuse ammonium bifluoride.

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Thermal and structural analysis of the reaction pathways of α-spodumene with NH4HF2

Cited by 28 publications

References 37 publications

Boosting NiO Catalytic Activity by x wt % F‐ions and K₂O for the Production of Methyl Ethyl Ketone (MEK) via Catalytic Dehydrogenation of 2‐Butanol

Boosting NiO Catalytic Activity by x wt % F‐ions and K₂O for the Production of Methyl Ethyl Ketone (MEK) via Catalytic Dehydrogenation of 2‐Butanol

Mg–O–F Nanocomposite Catalysts Defend against Global Warming via the Efficient, Dynamic, and Rapid Capture of CO₂ at Different Temperatures under Ambient Pressure

A novel low‐energy approach to leucoxene concentrate desiliconization by ammonium bifluoride solutions

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Thermal and structural analysis of the reaction pathways of α-spodumene with NH4HF2

Cited by 28 publications

References 37 publications

Boosting NiO Catalytic Activity by x wt % F‐ions and K2O for the Production of Methyl Ethyl Ketone (MEK) via Catalytic Dehydrogenation of 2‐Butanol

Boosting NiO Catalytic Activity by x wt % F‐ions and K2O for the Production of Methyl Ethyl Ketone (MEK) via Catalytic Dehydrogenation of 2‐Butanol

Mg–O–F Nanocomposite Catalysts Defend against Global Warming via the Efficient, Dynamic, and Rapid Capture of CO2 at Different Temperatures under Ambient Pressure

A novel low‐energy approach to leucoxene concentrate desiliconization by ammonium bifluoride solutions

Contact Info

Product

Resources

About

Boosting NiO Catalytic Activity by x wt % F‐ions and K₂O for the Production of Methyl Ethyl Ketone (MEK) via Catalytic Dehydrogenation of 2‐Butanol

Boosting NiO Catalytic Activity by x wt % F‐ions and K₂O for the Production of Methyl Ethyl Ketone (MEK) via Catalytic Dehydrogenation of 2‐Butanol

Mg–O–F Nanocomposite Catalysts Defend against Global Warming via the Efficient, Dynamic, and Rapid Capture of CO₂ at Different Temperatures under Ambient Pressure