Solid-liquid reaction process

Since the free energy of a molecule in the liquid phase is not markedly different from that of the same species volatilized, the variation in the intrinsic reactivity associated with the controlling step in a solid—liquid process is not expected to be very different from that of the solid—gas reaction. Interpretation of kinetic data for solid—liquid reactions must, however, always consider the possibility that mass transfer in the homogeneous phase of reactants to or products from, the reaction interface is rate-limiting [108,109], Kinetic aspects of solid—liquid reactions have been discussed by Taplin [110]. 

The various types of heterogeneous reactions are shown in Table 3.3. They are broadly grouped as solid-gas, solid-liquid, solid-solid, liquid-gas, and liquid-liquid reactions. The different types included in each group are also shown in the compilation. Some representative processes have been indicated as examples. It may be pointed out that in the group of solid-liquid reactions a specific mention of what is known as autocatalytic reactions has not been made. The autocatalytic processes occur when the liquid product reacts further with the solid undergoing reaction. The dissolution of copper in dilute sulfuric acid (or aqueous ammonia) in the presence of oxygen may be cited as an example ... 

Solid-liquid reactions are much more complex than solid-gas reactions and include a variety of technically important processes such as corrosion and electrodeposition. When a solid reacts with a liquid, the products may form a layer on the solid surface or dissolve into the liquid phase. Where the product forms a layer covering the surface completely, the reaction is analogous to solid-gas reactions if the reaction products are partly or wholly soluble in the liquid phase, the liquid has access to the reacting solid, and chemical reaction at the interface therefore becomes important in determining the kinetics. 

Since the deterioration of stone generally requires water, it might be thought to be essentially a solid—liquid reaction and hence outside the scope of this article. There are, however, many indications that the water for these processes is picked up by the solid from the gas phase, at relative humidities often well below 100%, so that the water is itself a gaseous reactant. 

Various absorbers used for the measurements of absorption rates in gas-liquid reaction processes can also be used to make similar measurements for the gas-liquid-solid reaction processes. Commonly-used absorbers are the laminar-jet absorber (Fig. 5-19). the wetted-wall column absorber (Fig. 5-20), the rotary-drum absorber, the disk column absorber (Fig. 5-21), the single-pellet absorber (Fig. 5-22). and the gradientless contactor (Fig. 5-23). The key features of these absorbers... 

The countercurrent mode of fixed-bed operation is normally used for physical absorption or gas-liquid reaction processes, rather than gas liquid-solid reaction processes. An extensive literature review on this type of column, as applied to the former processes, has already been reported11-45 and will not be repeated here. Two flow regimes in countercurrent operation, namely trickle-flow and bubble-flow, may be useful for gas-liquid-solid reactions. The majority of the discussion in this chapter will, therefore, be restricted to these flow regimes. 

Since countercurrent-flow operation is largely used for absorption and gas-liquid reaction processes, no information on liquid-solid mass transfer appears to have been published. 

However, it proceeds by a two step process of (1) a solid—liquid reaction to form a gaseous suboxide,... 

Li et al. developed a solid-state reaction process to synthesize perov-skite-type LaCoOs NCs with grain diameters of 15 0 run (Li et al., 2002). In the first step of the preparation, 5 run composite hydroxide NPs were s)mthesized by grinding metal nitrates liquid paste and mixing with KOH. Then the composite powders were calcined at 800 °C, yielding a single-phase oxide. Tien-Thao et al. prepared LaCo Cui J.O3 x < 0.3) by mechano-synthesis (Tien-Thao et al., 2008). The sample has various distinct Co " " ions in the perovskite lattice, which are more reducible. The reduced catalyst surface comprising cobalt and copper atoms is very selective for the hydrogenation of CO. 

Chemical reactions in soils are generally heterogeneous solid-liquid reactions involving a solid component of the soil and the soil solution. The reaction includes chemical processes involving formation or rupture of chemical bonds,... 

To appreciate the impact of SECM on the study of phase transfer kinetics, it is useful to briefly review the basic steps in reactions at solid/liquid interfaces. Processes of dissolution (growth) or desorption (adsorption), which are of interest herein, may be described in terms of some, or all, of the series of events shown in Figure 1. Although somewhat simplistic, this schematic identifies the essential elements in addressing the kinetics of interfacial processes. In one limit, when any of the surface processes in Figure 1 (e.g., the detachment of ions or molecules from an active site, surface diffusion of a species across the surface, or desorption) are slow compared to the mass transport step between the bulk solution and the interface, the reaction is kinetically surface-controlled. In the other limit, if the surface events are fast compared to mass transport, the overall process is in a mass transport-controlled regime. 

Various catalysts have been studied for these reaction processes. The major disadvantages of these reaction processes are (i) the need for an energy intensive separation step for catalyst recovery and (ii) limiting solubility of CO and O2 in the liquid reactant medium. One of the objectives of our study is to develop a heterogeneous gas-solid catalytic reaction process for the synthesis of methyl-N-phenylcarbamate involving step 3 and dimethyl carbonate involving step 4 over Cu-based catalyst. This gas-solid process would eliminate the solubility limitation and catalyst separation step, thus enhancing the overall economics of the carbamate synthesis (6-8). 

Pyrometallurgical methods, magnet separation gas-solid and solid-liquid reaction chlorination examination, 176-178 nonmetallic elements control, 178 processes, Vllf on vapor pressure basis, 176 molten salts... 

X. H. Wang and Y. C. Zhou, Microstructuie and properties of Ti3AIC2 prepared by the solid-liquid reaction synthesis and simultaneous in-situ hot pressing process. Ac(a Mater., 50[12], 3141-3149 (2002). 

We therefore used a solid-liquid reaction between photo-Ti02 and H-siloxane to gain further insight into the process of silicone-modified TiCh formation. In this paper, we report on our kinetic analysis of silicone-modified photo-Ti02 formation by the solid-liquid reaction between photo-Ti02 and H-siloxane. We also discuss the change induced in its surface properties by irradiation. 

The basic design of a leaching vessel for a batch, co-current or counter-current system can be identical with that used in other chemical processes involving solid-liquid reactions. A stirred vessel is commonly employed. 

Reaction process Adsorption Catalytic reactions Crystallisation Polymerisation Curing Desorption Melting Vapourisation Sublimation Desolvation (drying) Solid-solid transition Solid-liquid reaction Solid-gas reaction Solid-solid reaction Decomposition... 

The flow sheet of the technical process is shown in Figure 13.4. For a comprehensive description of critical steps of this technology, see Refs. 14 and 15 the main points are control of the solid-liquid reaction between the glucose and the fatty alcohol with acidic catalysis avoiding a fast polymerization of glucose, the good water removal, the economic separation and recycle of the excess fatty alcohol, and the treatment of the highly viscous APG melt to get the desired product quality with low polydextrose content. 

The chemical activation of carbons is a complex solid-liquid reaction. The reaction takes place when the solid (carbon) reacts, at about 500°C, with a liquid (hydroxide), producing mainly H2, alkaline metal, and carbonate, if the heat treatment temperature is lower than 750°C. This reaction is a redox process in which carbon is oxidized to carbonate and hydroxide is rednced to alkali metal and hydrogen. This set of reaction products and the type of reactions taking place are not necessarily the same for all carbonaceous materials thus, for example, lignocellulosic... 

As in any solid-liquid reaction, the reactivity of the carbon precursor is a key factor governing the activation process. Thus, in the case of coals, the lower the rank, the higher the reaction extent with the hydroxide. As the structnral order of the carbon increases (i.e., anthracite versus lignite), the activation process becomes more difficult. In these cases, KOH is much more effective than NaOH, presumably because of its easier intercalation in the graphene layers of the carbon precursors. 

A key issue in solid-liquid reactions is determination of the controlling process regime chemical reaction in the bulk liquid phase or mass transfer in the liquid film surrounding the solid particle. Experimentally, this is done by checking... 

Copper powders, having a variety of interesting particle shapes, can also be produced by the CQG method (9), a multi-step process involving gas/liquid and solid/liquid reactions. The process depends on the fact that copper can exist in two oxidation states. A copper (I) salt is fust produced by reducing an aqueous copper (n) ammonium sulphate solution with sulphur dioxide as... 

---