Chemical Engineering Science 58 (2003) 583–591 www.elsevier.com/locate/ces Is a monolithic loop reactor a viable option for Fischer–Tropsch synthesis? Ronald M. de Deugd a ; * , Rahul B. Chougule a , Michiel T. Kreutzer a , F. Michiel Meeuse b , Johan Grievink b , Freek Kapteijn a , Jacob A. Moulijn a a Reactor and Catalysis Engineering, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands b Process Systems Engineering, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands Abstract A Monolithic Loop Reactor design for Fischer–Tropsch synthesis with a production capacity of 5000 ton middle distillates per day (about 40 000 bbl= day) is presented. The required volume, 3350 m 3 , is competitive with conventional reactors, while eliminating disadvantages of existing reactor types such as catalyst attrition and separation, backmixing and large diusion distances. Although the kinetic expressions used in this study do not allow calculating the selectivity precisely, all important conditions, low temperature rise and constant H2= CO ratios, are met to ensure high selectivity towards heavy hydrocarbons. ? 2003 Elsevier Science Ltd. All rights reserved. Keywords: Fischer–Tropsch synthesis; Monolithic catalysts; Multiphase reactors; Modeling 1. Introduction Fischer–Tropsch synthesis (FTS) is a process to convert synthesis gas (1 : 2 mixture of CO and H 2 ) to water and hy- drocarbons that can be used as liquid fuels or base chemi- cals. Feedstocks for the generation of synthesis gas can be natural gas, coal and biomass. FTS is already an old process, but in the last decades, the interest is growing again under inuence of the need to convert natural gas from remote sources to liquid fuels and to utilize associate gas from oil rigs. Due to the polymerization-like mechanism of FTS a wide variety of, mainly, non-branched products is formed ranging from methane to heavy waxes. Therefore, the selectivity to, for instance, Diesel fuel is always limited. The selectivity of the process is usually described by the chain growth proba- bility, . This chain growth probability is strongly dependent on the process conditions. Super-stoichiometric concentra- tionsofhydrogenandhightemperatureslowertheselectivity ∗ Corresponding author. E-mail address: r.m.dedeugd@tnw.tudelft.nl (R. M. de Deugd). towards heavy products dramatically. High chain growth probabilities (¿ 0:90) are regarded desirable as they lead to reasonable primary selectivities to fuel ranges and high selectivities to heavy components, which subsequently can be converted to liquid fuels rather easily. Especially diesel range components are desirable as FTS products have high cetane numbers. A commercial feasible process should couple high pro- ductivity and high selectivity. FTS is a relatively slow process, which makes the process reaction rate determined. High catalyst loading per reactor volume is therefore cru- cial for the productivity and size of a FTS reactor. Constant temperature and H 2 = CO ratio over the reactor are essen- tial factors for selectivity. It is not easy to achieve this combination. The exothermal FTS process has a heat of reaction of 167 kJ= mol, what imposes strong requirements on heat removal capacity. The H 2 = CO ratio should be con- stant not only in the bulk phase, but also inside the pores of the catalyst. To obtain high selectivity and activity short diusional distances are favored (Schanke, Bergene, & Holmen, 1998). Typically particle sizes should be smaller than 100 m to avoid negative impact on selectivity. 0009-2509/03/$ - see front matter ? 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0009-2509(02)00583-3