Gas-Solid Processes

Direct (Single-Step) Process Routes 14.4.2.1 Gas-Solid Processes 

Mineral carbonation was first mentioned as a C02-binding concept for CCS by Seifritz in 1990 [80], A few years later, the concept of binding C02 in calcium and 

In a very recent study, the carbonation of Mg-silicates at 673-773 K, 100 MPa pressure with a (supercritical) C02-rich fluid , with or without NaCl present was reported to give between 3% and 57% carbonation conversion after 4h. The C02 source was oxalic acid, and the efficiency increased according to the ranking orthopyroxene, crystotile, olivine [86]. 

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Reh, L., The Circulating Fluid Bed Reactor—A Key to Efficient Gas-Solid Processing, Proc. First Intern. Conf. Circulating Fluidized Bed, p. 105-118, Halifax, Canada (1985)... 

Two Exemplified Combinatorial Approaches for Catalytic Liquid-Solid and Gas-Solid Processes in Oil Refining and Fine Chemicals... 

Reh, L., The Circulating Fluid Bed Reactor—A Key to Efficient Gas-Solid Processing, Proc. 

Reh, Lothar. The circulating fluid bed reactor—a key to efficient gas/solid processing, in Circ. Fluid Bed. Technol. (Basu, Prabir, ed.), pp. 105-118 (1986). 

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). 

A comparison between conventional and differential characterisation of gas-solid processes is illustrated by the Investigation of the redox properties of Ce02. The redox behaviour of this oxide is used in automotive exhaust catalysts. The ease of its reduction and re-oxidation makes it useful as an oxygen buffer during catalytic reactions [30]. 

In most condensed-matter phase transformations, pressure is typically not a chief controlling variable (although it is important in certain circumstances). This is in distinct contrast to the gas-solid processes discussed in the previous chapter, where gas-phase partial pressures typically played a cendal role. 

Table 4.4 compares the typical properties of major catalytic fluidized-bed processes, like those identified in Table 4.2, with corresponding practice for major gas-solid processes like combustion, gasification, roasting, incineration, and calcination. 

The degree of axial mixing of gas and particles in fluidized beds is important for many continuous as well as batch processes, and control thereof is desirable. It is very important to limit backmixing and maintain good gas-solid contact while using fluidization for solid or gas-solid processing, as these operations need high solid-phase conversion and gas-phase utilization. 

For gas/solid processes the fluidiz bed is the best alternative when large amounts of heat have to be supplied or removed (sections 45,1,4, 5.4.4 and 7,22.4),... 

Serra, J.M. and Corma, A. (2004). Two exemplified combinatorial approaches for catalytic liquid-solid and gas-solid processes in oil refining and fine chemicals. In Hagemeyer, A., Strasser, P. and Volpe, A.F. (eds.), Eligh-Throughput Screening in Chemical Catalysis, WUey-WCH, Weinheim, p. 129-151. 

S. A. Adelman and B. Garrison, Generalized Langevin theory for gas/solid processes Dynamical solid models, J. Chem. Phys. 65 3751 (1976). 

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