Related Experiment Video
Updated: Aug 5, 2026
09:27
Protein Crystallization for X-ray Crystallography
Published on: January 16, 2011
Layer-by-Layer Crystallization Phenomena in Urea Solution: An Experimental Study
Liwei Mao1, Jialong Jiang1, Bingqi Tian2
1School of Mechanical Engineering, Shanghai Dianji University, shanghai 201306, China.
ACS Omega
|August 1, 2026
Summary
Urea deposits in heavy-duty diesel Selective Catalytic Reduction (SCR) systems form complex structures. A new multilayer liquid-film method better replicates real-world urea crystallization, revealing distinct properties from lab samples.
Area of Science:
- Chemical Engineering
- Materials Science
- Environmental Science
Background:
- Urea deposits in heavy-duty diesel engine SCR systems exhibit complex morphology and composition under real operating conditions.
- Conventional laboratory methods fail to accurately replicate the dynamic, multi-cycle deposition processes leading to stubborn urea deposits.
Purpose of the Study:
- To develop and validate a novel multilayer liquid-film heating crystallization method for simulating real-world urea deposit formation.
- To investigate the fundamental differences in urea crystallization between multilayer and single-layer deposition models.
Main Methods:
- A multilayer liquid-film heating crystallization method was developed.
- Crystals from single-layer and multilayer films were analyzed using thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).
Main Results:
- Multilayer crystallization impedes heat transfer, favoring lower-temperature crystal components and requiring higher decomposition temperatures.
- Multilayer urea crystals showed greater mass than single-layer crystals of equivalent thickness under specific temperature conditions.
- Multilayer crystallization promotes ordered microstructures with cleaner surfaces due to secondary deposition and thermal history.
Conclusions:
- The multilayer liquid-film method provides a more realistic simulation of urea deposit formation in SCR systems.
- Understanding these crystallization differences is crucial for optimizing SCR system performance and preventing deposit-related issues.
Related Concept Videos
01:10Recrystallization: Solid–Solution Equilibria
Recrystallization is a purification technique used to separate impurities from solid compounds. In this technique, no chemical reactions occur. Instead, it exploits physical properties only, specifically, the solubility differences between the desired compound and impurities, either at a single temperature or at different temperatures, and under other selected conditions. The solid-solution equilibrium (solubility equilibrium) of each component in the solution represents a binary phase...
01:25Crystal Growth: Principles of Crystallization
Crystallization is a phase transformation process in which crystals are precipitated from a supersaturated solution or formed from other sources. During crystallization, atoms or molecules arrange themselves into a well-defined, rigid crystal lattice to minimize energy.
Initiating crystallization involves manipulating the concentration of the solute and the temperature of the solution. Since crystal growth occurs when the ratio of concentration and solubility of the solute in the solvent – the...
Initiating crystallization involves manipulating the concentration of the solute and the temperature of the solution. Since crystal growth occurs when the ratio of concentration and solubility of the solute in the solvent – the...
01:12Precipitation Processes
The experimental conditions in a gravimetric analysis should be optimized to maximize the particle size and purity of the obtained precipitate. Ideally, the concentration of the precipitating reagent should be low with effective stirring to maintain low relative supersaturation for the growth of large crystals. In homogeneous precipitation, the precipitant is slowly generated by a chemical reaction in the solution to avoid local reagent excesses. For example, urea decomposes gradually to...
01:21Polymer Classification: Crystallinity
Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
00:52Washing, Drying, and Ignition of Precipitates
After filtration, the precipitate is washed to remove coprecipitated impurities and any remaining mother liquor. Colloidal precipitates, such as silver chloride, are washed with an electrolyte (such as dilute nitric acid) to prevent the peptization of the precipitate. In the case of slightly soluble precipitates, the wash solution contains a common ion to reduce solubility. Lead sulfate, which is slightly soluble in water, is washed with dilute sulfuric acid. Similarly, wash solutions may be...
01:30Preparation of Amines: Alkylation of Ammonia and Amines
Alkylation is one of the methods used to prepare amines. Direct alkylation of ammonia or a primary amine with an alkyl halide gives polyalkylated amines along with a quaternary ammonium salt through successive SN2 reactions. This process of making the quaternary salt through the direct alkylation method is called exhaustive alkylation.
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering...
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering...