Density factors affecting crystal size

Crystal shape, size, and density all affect the physical properties of the final solid fat matrix. Crystal growth, primary nucleation, and secondary nucleation in fat systems are influenced by many factors, including diffusion, molecular compatibility, TAG structure, nuclei composition and surface properties, number of nuclei, and processing conditions (temperamre and/or shear) (38, 39). It is during the crystallization process of fats that the template for the final physical properties of the material is created. 

Two mtyorlactors affect droplet size and density in the PIPS process types and relative concentration of materials used and cure temperature. The cure temperature influences the rate of polymerization, viscosity of the polymer, diffusion rate of the liquid crystal and solubility of the liquid crystal in the polymer. Each factor is affected differently by the cure temperature with the result that droplet size varies in a complex manner with cure temperature (Figure 5) and must therefore be empirically determined for each formulation. 

Fundamentally, the solvent can influence crystal structure, crystal size, morphology, and purity by modifying solution properties (i.e., density, viscosity, and component diffusivities), solute solubility, as well as the structure of the crystal-liquid interface. The influence of the solvent on the first three factors are well known especially morphology (e.g., Srinivisan et al. 2000 Maruyuma et al. 2000 Wang et al. 1999 Walker 1997 Khoshkhoo et al. 1996 Blagden et al. 1998 Roberts et al. 1994 Geertman et al. 1992 Docherty et al. 1991 Shimon et al. 1990 van der Voort et al. 1990). The solvent properties affecting heat and mass transport... 

Light olefins especially ethylene ( 2 ) and propylene ( 3 ) can be formed from methanol in the MTO process (Chang et al., 1979) using catalyst SAPO-34. Several other catalysts like ZSM-5 (Marchi and Froment, 1991), and Chabazite (Liu et al.. 1984) have been tested. Physical and chemical properties of the catalyst influence its selectivity to hydrocarbons. The physical factors that affect the selectivity of the catalyst are temperature, pressure of the fixed bed reactor, and space velocity of the feed. Other physical characteristics that influence selectivity are crystal size, crystal size distribution, pore size and pore size arrangement. The chemical characteristics that influence the selectivity are acid site density, strength of acid sites, and type of surface acid groups. 

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