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Numerous qualified suppliers specialize in the design, engineering, manufacture, installation,commissioning, and support of bench-scale systems for use in laboratories, pilot plants and

small-scale production facilities in the chemical process industries. They may provide individualpieces of equipment, such as pressure vessels, agitated reactors, magnetic stirrers, metering

syringe pumps, diaphragm compressors, valves, heat exchangers, flow controllers and

instrumentation, or supply complete, multi-purpose skid-mounted systems.

Laboratory reactors may operate either continuously or in batch mode. This article focuses on

continuous reactors, which include: micro (or differential) reactors; integral reactors; semi-technical units and plant side-streams reactors; and continuous stirred-tank reactors (CSTRs).

Micro reactors. Micro reactors are characterized by a high flowrate-to-reactor-volume (or high

flowrate-to-catalyst-mass) ratio. They have short residence times and low pressure drops, operatenearly isothermally, and experience negligible axial and radial concentration gradients. These

features make such small reactors ideal for preliminary assessments and kinetic studies thatevaluate chemical reaction rates, kinetic constants, etc. Because the reaction rate is the same

throughout the reactor, the effect of each variable (e.g., pressure, temperature, reactant andproduct concentrations, etc.) can be studied separately and very accurate results can be obtained.

In addition, plug flow ensures the uniformity of the fluid properties throughout the bed

Micro reactor data are not sufficient to model full-scale reactors, even with comprehensive

knowledge of such parameters as mass and heat transfer, and wall effects. Other disadvantages of this type of reactor are that high flowrates are needed to preserve the differential conditions, and

it is difficult to simulate side-reactions, which are much lower than the main reaction and can gocompletely undetected.

Integral tubular reactors. It is generally more difficult to derive kinetic equations from integral

reactor data than from micro reactor data, and at adiabatic conditions it is even more difficult todo so. Most full-scale reactors, due to their low surface-to-volume ratio, normally operate under 

adiabatic conditions, so small-scale adiabatic integral reactors are typically not used to studykinetic parameters unless the kinetic model is already available. They may be used for the

simulation of full-scale reactors or for evaluating catalyst life.

Semi-technical units and plant side-stream reactors. These special arrangements provide theopportunity to study the overall process as a whole, both with regard to process performance, and

the chemical and physical characteristics of its components. This is the best way to test acatalyst, because it will be exposed to the variability of the actual full-scale process conditions.

In addition, this configuration may result in a significant cost saving compared to conventionalpilot-plant evaluations.

Continuous stirred-tank reactors. CSTRs are particularly suitable for kinetic studies. Theassumption of complete and perfect mixing must be checked before carrying out experimental

work in a CSTR; provided the fluid is not too viscous and mixing is adequate, the perfect mixingassumption is normally justified. Reactions of substances that poison a catalyst are also better 

studied in a CSTR than in an integral reactor, because the total catalyst volume is simultaneously

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exposed to the same concentration of the poisons, whereas in a tubular reactor, the catalyst layerscloser to the reactor entrance are exposed to higher concentrations of poisons.