Role of Crystal Seed in Aluminum Hydroxide Crystallization from Ammonia System with Added NH_(4)Al(SO_(4))_(2)·12H_(2)O

A method to promote aluminum hydroxide crystal growth through pickling Al(OH)_(3)as seed in the ammonia system was proposed to overcome these defects.The experimental results show that,under the conditions of pickling time of 15 min,the acid concentration of 10%,the addition of 70 g/L pickling-Al(OH)_(3)seed,and the coarse granular Al(OH)_(3)products(d0.5=85.667)can be obtained.The characterization results show that the phase of the product is gibbsite,consistent with the seed.Moreover,the steps and ledges can be formed on pickling Al(OH)_(3)seed surface under the ammonia system,effectively promoting crystal growth.During crystal growth,the roughness of the crystal surface was first increased and then decreased,and the lamellar structure was deposited on the crystal seed surface.The final particles are approximately round,the surface is compact and dense.The growth of the product is surface reaction controlled.In addition,the content of the AlO_(6)unit is increased and contributed to Al(OH)_(3)crystal growth.

Synergetic effect of secondary nucleation and growth on the lithium carbonate particle size in the gas-liquid reactive crystallization of LiCl-NH3·H2O-CO2

In this study,the gas-liquid reactive crystallization of LiCl-NH3·H2O-CO2 was adopted to produce Li2CO3.The weakly alkaline nature of NH3·H2O in the absence of any recarbonation process resulted in a unimodal and easily controllable particle size distribution(PSD)of the obtained Li2CO3.The reaction temperature significantly influenced both the Li2CO3 particle size and PSD.By increasing the temperature from 25 to 60℃,the volume weighted mean particle size increased from 50.5 to 100.5μm,respectively.The Li2CO3 secondary nucleation rate and growth rate were obtained by focused beam reflectance measurements and a laser particle size analyzer,respectively.The secondary nucleation rate of Li2CO3 reduced as a function of temperature,whereas the growth rate increased.In addition to improving the surface energy of the crystals to enhance the growth process,higher temperatures also reduced the supersolubility of Li2CO3,which also plays a role to decrease the secondary nucleation rate.At a constant temperature,supersaturation affects the Li2CO3 particle size through the synergistic effect of secondary nucleation and growth.Hence,with improved supersaturation,the mean particle size of Li2CO3 decreased.The results provide a meaningful way to evaluate the crystallization process and to regulate the particle size.

Control of the agglomeration of crystals in the reactive crystallization of 5-（difluoromethoxy）-2-mercapto-lH- benzimidazole

5-（Difluoromethoxy）-2-mercapto- 1H-benzimi- dazole （DMB） was precipitated by adding acetic acid to the DMB sodium salt solution. The spherical agglomeration of DMB during the reactive crystallization in a batch crystallizer was monitored by real-time Particle Video Microscope （PVM）. We found that the low feeding rate of acetic acid, high crystallization temperature, low agitation rate or adding seed crystal can facilitate the formation of spherical agglomerates. By using a simple model, the mean crystal agglomerate size of DMB thus predicted is generally in agreement with the experimental data. In addition, the crystallization process of DMB was optimized by a new control strategy of supersaturation to avoid disadvantages brought by agglomeration.

Advances in reactive co-precipitation technology for preparing high-performance cathodes

Reactive crystallization plays an essential role in the synthesis of high-quality precursors with a narrow particle size distribution,dense packing,and high sphericity.These features are beneficial in the fabrication of high-specific-capacity and long-cycle-life cathodes for lithium-ion and sodium-ion batteries.However,in industrial production,designing and scaling-up crystallizers involves the use of semi-empirical approaches,making it challenging to satisfactorily meet techno-economic requirements.Furthermore,there is still a lack of in-depth knowledge on the theoretical models and technical calculations of the current co-precipitation process.This review elaborates on critical advances in the theoretical guidelines and process regulation strategies using a reactive crystallizer for the preparation of precursors by co-precipitation.The research progress on the kinetic models of co-precipitation reactive crystallization is presented.In addition,the regulation strategies for the reactive crystallization process of lithium-ion ternary cathodes are described in detail.These include the influence of different reactive crystallizer structures on the precursor's morphology and performance,the intelligent online measurement of efficient reactive crystallizers to ensure favorable conditions of co-precipitation,and preparing the precursor with a high tap density by increasing its solid holdup.A controllable reactive crystallization process is described in terms of the structural design with concentration gradient materials and bulk gradient doping of advantageous elements(such as magnesium ion)in lithium-ion cathodes and the fabrication of sodium-ion cathodes with three typical materials-Prussian blue analogues,transition metal oxides,and polyanionic phosphate compounds being involved.

Reactivity of Fe3(CO)(12) with Alkynes R-C≡C-R＇： Syntheses and Crystal Structures of Substituted Cyclic Ketones and Carbonyl Iron Complexes

The reactivity of carbonyl iron cluster with alkynes has been studied by the thermal reaction of Fe_3（CO）_（12） with R-C≡C-R＇（R = Fc（Ferrocenyl）; R′ = Ph（Phenyl）, Fc, H）. The hexacarbonyldiiron cluster with ferracyclopentadiene ring（μ_2, η~4-C_4Ph_4）Fe_2（CO）_6（1） and one tetraphenyl substituted cyclopentadienone（Ph_4C_4CO）（2） were simultaneously obtained by the reaction of Fe_3（CO）_（12） with alkyne（Ph-C≡C-Ph）. Only one ferrole cluster（μ_2, η~4-C_4Fc_2H_2）Fe_2（CO）_6（3） was separated by using Fc-C≡C-H as alkyne. One tri-carbonyl iron complex（η~4-C_4Fc_4CO）Fe（CO）_3（4） and an unexpected new cyclic ketone compound 2,2,4,5-tetraferrocenylcyclopenta-4-en-1,3-di-one [Fc_4C_3（CO）_2]（5） were obtained by using Fc-C≡C-Fc as alkyne. A new complex（η4-2,4-diphenyl-3,5-diferrocenylcyclopenta-2,4-dien-1-one）-tricarbonyl iron（η~4-C_4Ph_2Fc_2CO）Fe（CO）_3（6） was synthesized by the reaction of Fe_3（CO）_（12） with Fc-C≡C-Ph. The structures of compounds 1~6 were determined by X-ray single-crystal diffraction and spectroscopic characterization. The crystal structures of two new compounds 5 and 6 were analyzed. Our experimental results reveal the structural models of the reaction products are affected by the kinds of substituents from alkynes R-C≡C-R′.

Characterization of char from high temperature fluidized bed coal pyrolysis in complex atmospheres

The physiochemical properties of chars produced by coal pyrolysis in a laboratory-scale fluidized bed reactor with a continuous coal feed and char discharge at temperatures of 750 to 980 ~ C under N2-based atmospheres containing 02, H2, CO, CH4, and CO2 were studied. The specific surface area of the char was found to decrease with increasing pyrolysis temperature. The interlayer spacing of the char also decreased, while the average stacking height and carbon crystal size increased at higher temperatures, suggesting that the char generated at high temperatures had a highly ordered structure. The char obtained using an ER value of 0.064 exhibited the highest specific surface area and oxidation reactivity. Rela- tively high 02 concentrations degraded the pore structure of the char, decreasing the surface area. The char produced in an atmosphere incorporating H2 showed a more condensed crystalline structure and consequently had lower oxidation reactivity.