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The exothermic reactions with fast intrinsic kinetics when carried out in conventional reactors are often limited by heat transfer. This results in the formation of hot spots, which affects product distribution of complex reactions and may lead to reactor runaway. Microstructured reactors (MSR) have been successfully used for this type of reaction, gaining increased temperature control and enhanced safety. Although different MSR concepts have been applied to various processes, the general design criteria are still poorly discussed in the literature. In this review, temperature management in conventional single injection MSR is described. The important issues, such as reactor safety and stability, along with the role of mixing, are discussed in detail. Subsequently, the multi-injection reactor concept is introduced and a simplified model developed to investigate the temperature profile is presented. Finally, the benefits and critical issues in the design of multi-injection MSR are highlighted.

The low water vapor pressures of mixtures of water with the ionic liquids (ILs), [EMIM][EtSO 4 ] and [BEIM] [EtSO 4 ], indicate that a process of gas dehydration by absorption in ILs might be an alternative to the classical absorption process with triethylene glycol (TEG). The activity coefficient for an infinite dilution of water in the IL (x IL → 1), which should be low for efficient dehydration, is only about 0.2 for [EMIM][EtSO 4 ] compared to 0.6 for triethylene glycol. In contrast to TEG, losses by evaporation are excluded with ILs as solvents, because they have a negligible vapor pressure. The number of separation stages needed for the absorption in the IL and for the subsequent regeneration of the water-loaded IL is small, about six and eight, respectively. IL regeneration can be achieved by distillation of water out of the IL (e.g., at 120°C) and stripping with ambient air, which is not possible in the case of TEG (chemical attack by O 2 ).

The development of microreactors that operate under harsh conditions is always of great interest for many applications. Here we present a microfabrication process based on low-temperature co-fired ceramic (LTCC) technology for producing microreactors which are able to perform chemical processes at elevated temperature (>400°C) and against concentrated harsh chemicals such as sodium hydroxide, sulfuric acid and hydrochloric acid. Various micro-scale cavities and/or fluidic channels were successfully fabricated in these microreactors using a set of combined and optimized LTCC manufacturing processes. Among them, it has been found that laser micromachining and multi-step low-pressure lamination are particularly critical to the fabrication and quality of these microreactors. Demonstration of LTCC microreactors with various embedded fluidic structures is illustrated with a number of examples, including micro-mixers for studies of exothermic reactions, multiple-injection microreactors for ionone production, and high-temperature microreactors for portable hydrogen generation. IntroductionChemical microreactors are a type of meso-scaled reaction systems that have fluidic channels with characteristic dimensions in the sub-millimeter range. By combining process intensification concepts with microfabrication techniques, these microreactors have been rapidly developed to perform liquid/gas phase chemical reactions, particularly the quasiinstantaneous endothermic or exothermic ones.1,2 Ceramic materials in general feature high chemical and thermal stability. Hence they are very preferable to be used as reactor construction materials, especially for reactors involved with high temperature and/or harsh chemical reactions. be used as the embedded fluidic structures (e.g. channels or cavities) get easily damaged in the stacked LTCC tapes by the high lamination temperature and/or pressure, causing sagging, tearing and cracking issues. Several approaches have been proposed so far in order to reduce these deformations and improve the quality of integrated LTCC fluidic structures. One method is using temporary inserts to introduce mechanical supports to the LTCC cavities to avoid deformation and/or sagging during lamination. These inserts, usually solid flexible objects, 23 are removed right after lamination. However, the removal of inserts from the laminate can cause permanent damage to these fluidic structures. Besides, this method is not applicable for fabricating fully embedded fluidic channels. Alternatively, a chemical-assisted lamination process has been proposed that enables low-pressure and/or lowtemperature bonding of LTCC green tapes. Roosen et al. 24used double-sided adhesive tape that contains acrylate adhesives and a polyethylene terephthalate (PET) film to ensure temporary binding of green tapes under a low lamination pressure at ambient temperature. Upon heating (40-60°C), these adhesives, together with the binders in the LTCC green tapes, soften and join the laminates through capillary forces. Aside from adhesives, ...