Periodic operation of a trickle‐bed reactor

Abstract

The influence of periodic water flow on SO, oxidation in a trickle bed of activated carbon catalyst was investigated, whereby gaseous reactants were introduced into the trickle-bed reactor continuously, but water was turned on and off. Mean liquid superficial velocities of 0.86 and 1.65 mm/s were used. At the latter, an increase in the oxidation rate of about 30 to 45% was found within a range of cycle periods from 2 t o 80 min. A temperature change of up to 7OC was observed in the bed during periodic operation. An explanation of the improved average oxidation rate under periodic operation is developed in terms of the steady-state rates with and without water flow for symmetrical and asymmetrical cycles.

Periodic operation of catalytic reactors—introduction and overview

“…For ammonia synthesis using a ruthenium catalyst, a thousand-fold increase in the synthesis rate has been demonstrated in an operation that switches the reactor feed every several seconds between H 2 and N 2 [ 1 ]. For the oxidation of SO2 in the presence of air and water over an activated carbon catalyst, the rate of conversion of SO2 to sulfuric acid can be increased by about 50% if the water flow is periodically turned on for a short time rather than flowing continuously through the bed [2]. The yield of acrolein in the partial oxidation of propene over Sb-SnO catalyst can be doubled by switching between air and propene mixtures of different composition [ 3 ].…”

“…Another, often more meaningful, characterization is the global enhancement: ~b*= r/ ( rss)max (2) where the denominator is the maximum rate achievable at steady state at any composition with temperature and pressure of the system held constant. Fig.…”

“…High thermal inertia makes wall temperature difficult to modulate for cycle periods that affect performance. This input variable, therefore, has had only limited study [20] 1970 As above Flow Selectivity Wandrey and Renken [21 ] 1973 ' Hydrocarbons oxidation (propene, cyclohexene ) Concentration Product distribution Renken et al [22] 1974 EtOH dehydration to diethyl ether Concentration Selectivity Helmrich et al [23] 1974 Ethylene hydrogenation Concentration Rate Baiker and Richarz [ 24] 1976 As above Concentration Rate Renken et al [25] 1976 Ethylene oxidation Concentration Selectivity Dautzenberg et al [26] 1977 Fischer-Tropsch synthesis Concentration Product distribution Briggs et al [27] 1977-80 SO2 oxidation Concentration Rate Leupold and Renken [ 28 ] 1977 Ethyl acetate from ethylene and acetic acid Concentration Rate AI- Taie and Kershenbanm [ 291 1978 Butadiene hydrogenation Concentration Selectivity Bilimoria and Bailey [ 30] 1978 Acetylene hydrogenation Concentration Selectivity Crone and Renken [ 31 ] 1979 Styrene polymerization Concentration Rate, product distribution Cutlip [ 32 ] 1979 CO oxidation Concentration Rate Abdul-Kareem et al [33] 1980 As above Concentration Rate Lee et al [ 34 ] 1980 Saponification of diethyl adipate Concentration Selectivity Silveston and Hudgins [ 35 ] 1981 SO2 oxidation Concentration Rate Jain et al [ 15,36] 1982-83 NH3 synthesis Concentration Rate Wilson and Rinker [ 37 ] 1982 NH3 synthesis Concentration Rate Adesina et al [38] 1984 Fischer-Tropsch synthesis Concentration Rate EI-Masry [ 39] 1985 Claus reaction Concentration Rate Nappi et al [40] 1985 Low-pressure methanol Concentration rate M/iller-Erlwein and Guba [ 41 ] 1988 Methacrolein from IBA Concentration Selectivity Haure et al [2] 1989 SO2 oxidation in tfickel bed Flow Rate Saleh-Alhamed et al [42] 1992 ._co_J , ....…”

Carbon materials and catalytic wet air oxidation of organic pollutants in wastewater

“…Forced periodic operation of liquid flow must be considered as a new promising operation concept. Silveston and Hanika [199] lately reviewed periodic operation of TBRs pointing out the good results obtained for reactions including the wet oxidation of SO 2 over activated carbon [200] and the catalytic hydrogenation of a-methylstyrene [201,202] or crotonaldehyde [203]. Essentially, periodic operation consists in controlled ON-OFF liquid feed flow modulation to induce forced pulsing flow regime in the reactor.…”

“…periodic operation, is another example for dynamic behaviour of TBR. Periodic operation was experimentally studied for the catalytic oxidation of phenol [35] and SO 2 [200,240] over activated carbon. Proper adjusting of feed cycle period length and its split value was shown to increase conversion if the reaction system is limited by the gaseous reactant.…”