The term trickle bed is used here to mean a reactor in which a liquid phase and a gas phase flow concurrently downward through a fixed bed of catalyst particles while reaction takes place. The earliest antecedent probably was the so-called “trickling filter” which has long been used for removal of organic matter from wastewater streams by aerobic bacterial action. Biological growths are allowed to attach themselves to a bed of stone or other support over which the wastewater is allowed to trickle in contact with air. Another antecedent appeared in the 1930s when Duftschmid and co-workers at the I.G. Farbenindustrie used evaporative cooling of an inert oil which flowed upwards through a catalyst bed to remove the heat of reaction in a version of the FischerTropsch process for synthesis of liquid fuels from H2 and CO and a later version at the U.S. Bureau of Mines operated with concurrent upflow but without evaporative cooling. This was superceded by an ebulliating bed reactor because of difficulties with cementation of the catalyst in the fixed bed, but commercial scale operations of this process in Germany and elsewhere have all utilized completely vapor-phase reaction (Storch et al., 1951; Crowell et al., 1950; Benson et al., 1954; Kastens et al., 1952). Trickle-bed reactors have been used to a moderate extent in chemical processing, but most of the published information about their industrial applications concerns the processing with hydrogen of various petroleum fractions, in particular the hydrodesulfurization or hydrocracking of heavy or residual oil stocks and the hydrofinishing or hydrotreating of lubricating oils. Their commercial development during the 1950s by the Shell Companies and by the British Petroleum Company has been described by van Deemter (1964), Le Nobel and Choufoer ( 1959), and Lister (1964). The development of hydrocracking and hydrodesulfurization processes by Chevron, Esso (Exxon), Gulf, Union Oil, and others has been described in the proceedings of the various World Petroleum Congresses. Information is fragmentary on uses in chemical processing. A process for synthesis of butynediol (HOCH2C = CCH20H) from aqueous formaldehyde and acetylene uses trickle-bed flow over a copper acetylide catalyst and recycle of the product stream for heat removal (Brusie et al., 1963). Other trickle-bed studies of this reaction are given in a thesis by W. Bill, as reported by Bondi (1971), who also cites trickle-bed studies by H. Hofmann on the hydrogenation of glucose to sorbitol. Kronig (1963) describes a trickle-bed process used in one or more commercial plants for selective hydrogenation of acetylene to remove it in the presence of butadiene in Cq hydrocarbon streams. Operation at 10” to 20°C and 1.9 to 5.8 atm pressure allows liquid-phase processing which reportedly gives long catalyst life, unlike gas-phase processing in which polymers rapidly build up on the catalyst. The standard commercial process for manufacture of hydrogen peroxide utilizes a working solution of an alkyl

Trickle-bed reactors

Kinetics of the reaction of oxygen with clean nickel single crystal surfaces. I - Ni/100/ surface. II - Ni/111/ surface

Equilibria and kinetics of CO2 adsorption on hydrotalcite adsorbent

Experimental data for the adsorption and desorption of CO2 on potassium promoted hydrotalcite adsorbent were measured under conditions depicting the separation enhanced steam-methane reforming process. Adsorption saturation capacities of 0.58 and 0.65 mol/kg were measured at 753 and 673 K, respectively, under wet feed conditions. An ~ 10% reduction of the saturation capacity was observed under dry feed conditions. In both cases, a Langmuir model adequately described the adsorption isotherm. Experimental data revealed the rapid degradation of the adsorbent under dry feed conditions, and higher losses at higher temperatures. Adsorbent regeneration was possible by means of a steam purge, but some irreversible loss in capacity was indicated for very long times-on-stream. A dynamic model accounting for semi-technical scale operation was developed to describe the key operating steps of the pressure swing based adsorptive process. Kinetic studies suggested mass transfer control for the adsorption, depressurization, and purge steps of operation. The study illustrated the complexities of CO2 adsorption on hydrotalcite. Some variation in adsorption parameters is expected depending on the conditions of pre-treatment. For adsorbent previously not contacted with steam or CO2 feed, observations indicated an initial strong adsorption of material, depicting a chemisorption mechanism.

Equilibria and kinetics of CO 2 adsorption on hydrotalcite adsorbent

Phthalic anhydride is a chemical of considerable importance and is generally produced by the vapor-phase oxidation of o-xylene or naphthalene over vanadium pentoxide catalysts according to

C.N. Kenney

Papers

Partial wetting in trickle bed reactors — the reduction of crotonaldehyde over a palladium catalyst

Modelling of the pressure swing air seperation process

Island models and the catalytic oxidation of carbon monoxide and carbon monoxide-olefin mixtures

Simulation of rapid pressure swing adsorption and reaction processes

Adsorbent particle size effects in the separation of air by rapid pressure swing adsorption