What is the difference between a micromixing reactor and a conventional batch reactor

The microreactor is a kind of micro-pipeline reactor based on continuous flow, which is used to replace traditional reactors, such as glass flasks, funnels, and traditional batch reactors commonly used in industrial organic synthesis. In the microreactor, there are a large number of micro-reaction channels made by precision machining technology, which can provide a large specific surface area and extremely high mass and heat transfer efficiency. In addition, the microreactor replaces batch operation with continuous flow, making it possible to accurately control the residence time of the reactants.

These characteristics allow organic synthesis reactions to be precisely controlled at the microscopic scale, which provides the possibility to improve reaction selectivity and operational safety.

The big difference is that the fixed-bed reactor is fixed after the catalyst bed is filled, so it is called fixed-bed reactor. That is, the catalyst bed does not move, and the reactive substances react through the catalyst. The fixed bed reactor has a short reaction time and no backmixing, which requires a strong catalyst activity.

Similarly, for the reactor form, which is a fully mixed-flow reactor, it requires a long reaction time, poor catalytic activity of the catalyst, or no catalyst. The reaction conditions of pressure and temperature are relatively high, and these parameters are easy to control, so they cannot replace each other.

Ideal reactors are batch reactors and flow reactors.

Batch reactors with uniform mixing of reaction materials, or flow reactors with piston flow or full mixed flow of reaction materials, are collectively referred to as ideal reactors. Flow reactor features: both output and input are continuous flow.

Usually all flows are steady-state. The batch reactor has the characteristics of flexible operation, variable production, low investment and fast start-up. Therefore, it is widely used in medicine, pesticides, dyes and various fine chemical industries.

There are two types of ideal reactors that are commonly referred to: ideal hybrid (fully mixed) reactors and flat-flow (piston or extrusion flow) reactors. The so-called complete mixed flow reactor means that the reaction fluid in the vessel reaches complete mixing instantaneously, and the material in the vessel has the same temperature and concentration as the material at the outlet of the reactor.

The so-called translational flow reactor means that the reaction materials in the vessel move with the same flow rate and consistent direction, there is no mixing of materials with different residence times, and all materials have the same residence time in the tank.

Categorized by mode of operation:

1. Intermittent operation of the reactor.

Before the reaction, the raw materials are added to the reactor at one time until the reaction reaches the specified conversion rate, that is, the reactants are obtained, usually in a kettle reactor with a stirrer.

Advantages: Large operational flexibility, mainly used for small batch production.

2. Continuous operation of the reactor.

The reactants are continuously added to the reactor and the products are continuously led out of the reactor, which belongs to the steady-state process, and can use kettle, tubular and tower reactors.

Advantages: suitable for large-scale industrial production, strong production capacity, stable product quality, easy to achieve automatic operation.

3. Semi-continuous operation reactor.

It is an unsteady process to add part of the reactants to the reactor once before the reaction, and the rest of the reactants are added continuously or intermittently during the reaction process, or a certain product is continuously removed from the reactor during the reaction process.

Advantages: The reaction is not too fast, the temperature is easy to control, which is conducive to improving the conversion rate of reversible reactions.

Classification by fluid flow and mixing type:

1. Horizontal push flow reactor.

When the material flows in a tubular reactor with a large length-diameter ratio, if the fluid in each microelement volume in the reactor moves forward at the same speed, there is no backmixing in the flow direction of the fluid, which is the translational flow.

Features: The residence time of each material microelement through the reactor is the same, the material moves forward section by section along the flow direction in the reactor, there is no backmixing, the parameters such as material composition and temperature change gradually along the pipeline, but the parameters such as material composition and temperature on each section remain unchanged in the time process, continuous steady-state operation, and the structure is a tubular structure.

2. Ideal mixed flow reactor.

The material microelements of the reactor can be fully mixed with the original material microelements in the reactor instantaneously (strong stirring in the reactor), and the concentration of each point in the reactor is equal and does not change with time.

Features: The residence time of each material microelement in the reactor is not the same, the material is fully mixed, the backmixing is the most serious, the material composition and temperature at each point in the reactor are the same, and do not change with time, continuous stirred kettle reactor.

3. Non-ideal mixed flow reactor.

The actual reactor is mainly due to the dead angle, ditch flow, bypass, short circuit and uneven velocity distribution in the reactor in industrial production, which deviates from the ideal flow pattern. ‍

Kettle type, tubular type, tower type, fixed bed, fluidized bed.

Hangzhou Shenshi has actively invested in the research and development and application of micro-reaction technology, and has made some gratifying progress, and has now achieved industrial large-scale production, which has played an important role in improving intrinsic safety. After continuous experimental screening and exploration, the following are the experimental types and experimental conditions suitable for microreactors:

Oxidation reaction, Grignard reaction, Grignard addition reaction-elimination reaction, aldol condensation reaction, diazotization reaction, Balz-Seaman reaction, diazotization hydrolysis backslip reaction, nitrification coarse reaction.

Batch kettle reactor, or batch kettle.

Flexible operation, easy to adapt to different operating conditions and product varieties, suitable for small batch, multi-variety, long reaction time of product production. The disadvantage of batch kettle is that it needs to have auxiliary operations such as loading and discharging, and the product quality is not easy to stabilize.

However, some reaction processes, such as some fermentation reactions and polymerization reactions, are still difficult to achieve continuous production, and batch kettles are still used so far.

The intermittent operation reactor is to add the raw materials to the reactor at one time according to a certain ratio, and after the reaction reaches a certain requirement, the materials are discharged at one time. The continuous operation reactor is the continuous addition of raw materials and the continuous discharge of reaction products. When the operation reaches a steady state, the state parameters such as the composition and temperature of the material at any position in the reactor do not change with time.

A semi-continuous operating reactor, also known as a semi-batch operating reactor, is somewhere in between and typically involves the addition of one reactant at once and then another in succession. After the reaction reaches a certain requirement, the operation is stopped and the material is discharged.

The advantage of batch reactor is that the equipment is simple, and the same equipment can be used to produce a variety of products, especially suitable for the production of small batches and multiple varieties in industrial sectors such as medicine and dyes. In addition, there is no backmixing of the material in the batch reactor, which is beneficial for most reactions. The disadvantage is that auxiliary processes such as loading and unloading, cleaning and other auxiliary processes are required, and the product quality is not easy to be stable.

Continuous kettle reactor, or continuous kettle.

The disadvantages of batch kettles can be avoided, but the stirring effect will cause backmixing of the fluid in the kettle. In the case of vigorous stirring, low liquid viscosity or long average residence time, the flow pattern of the material in the kettle can be regarded as full mixed flow, and the reactor is accordingly called full mixed kettle. In situations where high conversion rate is required or there are tandem side reactions, the backmixing phenomenon in the kettle reactor is a disadvantageous factor.

At this time, a multi-kettle tandem reactor can be used to reduce the adverse effects of backmixing, and the reaction conditions can be controlled in separate reactors.

Continuous reactors should be used for large-scale production whenever possible. The advantages of continuous reactors are stable product quality and easy operation control. The disadvantage is that there are different degrees of backmixing in the continuous reactor, which is an unfavorable factor for most reactions, and should be suppressed by reasonable selection and structural design of the reactor.

Semi-continuous kettle reactor.

It refers to a reactor in which one raw material is added at one time and another raw material is added continuously, and its characteristics are between the batch kettle and the continuous kettle.

1。Bioreactor is a general term for vessels used in biological reaction processes. Including enzyme reactors, fixed cell reactors, various tremor and withered cell culturers and fermenters. In short, it is a special place where the activity of biological cells or enzymes is used to catalyze reactions;

2。The advantages of using bioreactors over chemical synthesis reactors are: high efficiency, stability, low cost, and repeated use.

3。For example, the main advantages of using a breast bioreactor are: stable product quality; Low cost; Short R&D cycle; No pollution; The economic performance has been remarkable.