The different Micro Reaction Technology, Design, Process & Applications in the industry

Micro reaction Technology – for miniaturization of chemical reaction systems

Category : General Chemicals
Published by : Data Research Analyst, Worldofchemicals.com

Abstract

In recent times chemical compounds need greater speed in the discovery process, which requires advanced automation. But majority of the current reactions are still performed by applying conventional techniques and apparatus. This has led to severe impact on the scale-up process. With recent advances in chemical reaction technology, sub-millimetre/sub-millilitre sized micro structured reactors, mixers and other micro process components have been developed. One of these technologies leading to miniaturization of reaction systems is the ‘Micro reaction technology (MRT)’ and these reactors are named as ‘Micro reactors.’ Micro reactors gained more importance in the field of chemistry, molecular biology and pharmaceutical chemistry etc by producing products in larger volumes. In this context, the present article will explain various concepts involved in the design, manufacturing and applications of micro reactors.

Introduction

MRT is a concept, which can increase performance of reactions in a continuous manner, within well-defined reaction channels, where typical dimensions are of the order <1000 μm and volumes. MRT which is growing in its usage is not a new concept, but has been suggested in the early eighties.

Main features of MRT are that the reaction conditions can be transferred from laboratory-scale reactors to production sites without the need for reoptimization of various conditions. MRT has certain advantages.

  • Optimal mixing
  • Effective heat exchange
  • Small reaction volume
  • Faster product development
  • Reduced exposure to hazardous chemicals

Efficient Heat Transfer

Micro reactors with their small surface to volume ratios are able to absorb heat created from a reaction much more efficiently than any batch reactor. In a micro reactor, the heat created by mixing the two reagents is also detectable. The small inner volume of a micro reactor (typically less than a millilitre) combined with its strong heat exchange efficiency guarantees the safe and stable performance of highly exothermic reactions over hours. Even explosive reactants and intermediates can be handled safely in a micro reactor.

Efficient Mixing

Mixing quality is crucial for many reactions where the molar ratio between reactants needs to be controlled precisely in order to suppress side reactions. A sophisticated regime will mix reactants efficiently with a small path length of a few centimetres.

MRT is currently one of the most innovative techniques in the field of chemical synthesis and similar fields. It opens up new ways to develop novel relation process and to construct advanced economic chemical plants.It is an innovative alternative to large-scale production in the chemical industry.

Advantages of MRT

  • Process safety
  • Novel reaction conditions
  • Reduced waste conditions
  • On-site chemical processing

Micro reactors

Micro reactors are defined as miniaturized reaction systems, fabricated by microtechnology. The chemical reactions which are happening in micro reactors are the batch reactions. 

Fig. 1) Micro reactors schematic diagram

Micro reactors offer a much improved control of reaction parameters, such as temperature and relative concentrations and allow higher yields, smaller amounts of by-products.

Micro reactors can be fabricated with materials like

  • Glass
  • Quartz
  • Diamond
  • Polymethylmethacrylate
  • Polydimethylsiloxane
  • Polyimide
  • Silicon
  • Stainless steel
  • Nickel

Glass is an excellent material for components in micro reaction technology because of its unique properties and advantages.

Advantages

  • Technical advantages
  • Ecological advantages
  • Economic advantages

Technical advantages

  • Good control of chemical reactions
  • Efficient heat exchange
  • They can withstand to high pressure and hazardous chemicals

Ecological advantages

  • Safe production of chemicals
  • Safe production of pharmaceutical products
  • Preservation of resources during production
  • Reduction of waste disposal

Economic advantages

  • Numbering up of reactors instead of scale up
  • Integration of various production steps
  • Integration of various production steps

Disadvantages

  • Cost issues
  • Challenges in numbering up
  • Clogged tubes

Case study: Biodiesel production in micro reactors

Introduction

Biodiesel is defined as the mono alkyl esters of long chain fatty acids and is derived from vegetable oils via the transesterification reaction of triglycerides with alcohols.

Fig. 2) Transesterification with methanol to produce fatty acid methyl esters (FAME)

Biodiesel has many merits as a renewable energy resource which relieves reliance on petroleum fuels. It is biodegradable, non-toxic and has a more favourable combustion emission profile such as low missions of carbon monoxide, sulphur, particulate matter and unburned hydrocarbons. In addition, using biodiesel on a large scale would result in more carbon dioxide recycling by photosynthesis, thereby minimizing the impact on greenhouse effect.

CSIR Biosciences has been investigating the production of biodiesel using various sources of vegetable oils eg soya, sunflower, canola, jatropha, palm and peanut. All of these reactions were successfully scaled up to pilot plant scale using conventional, batch, stirred tank, jacketed reactors and biodiesel standards were produced for the SABS (~100L of each oil). 

The agro processing and chemical technologies (ACT) group has been developing expertise in micro reactor technology and more recently an investigation was undertaken into the production of biodiesel using commercially available micro reactors. The laboratory investigation and optimization phase of the project has been completed and we are now in a position to conduct a comparative study of the conventional reactor system versus micro reactor system.

Experiment

Sunflower and soya were used as the oil source in a base catalyzed transesterification reaction with methanol. Various types of micro reactors were initially assessed to determine optimum reaction performance in terms of conversion, selectivity and, most importantly, productivity. The most appropriate reactor was selected. The process was optimized and downstream processing was investigated. An investigation was also undertaken to determine the reaction kinetics as well as key process parameters based on both experimental as well as modeling/simulation studies. Transesterification reaction normally takes about three hours to complete in a stirred tank batch reactor. However, complete conversion was achieved in less than a second in the micro reactor. This represents a 10800x increase in the reaction rate, which clearly demonstrates the unprecedented reaction efficiencies of micro reactors.

Conclusion

MRT showed more advantages in continuous processing over batch processing. More over micro reactors are becoming the standard tool for chemists to supplement existing technology for better product development. Use of MRT has led to production of many new compounds as a result of shorter development times, advanced automation and increased R&D efficiency. 

Micro reactors can handle 1,000–2,000 kilogramme of product per hour with yields up to 20 per cent higher than traditional large vessels, which is leading to increase in the productivity by 103-104.

The reaction conditions like temperature, time, mixing is well controlled by micro reactors and it uses minimal amount of raw materials.

Even though numerous impressive examples of applications of micro reactor technology in synthetic chemistry have been reported, some major drawbacks associated with this technique remain: the incompatibility of reactors with solid reagents that cannot be used for wall-coatings or be supported on linkers, the sensitivity to precipitations and the useful applicability mainly to fast reactions. The overall concept of highly efficient continuous-flow micro reactor techniques requires further improvements before it can be applied as a standard tool in chemical laboratories.

Reference

[1] Dr Axel Kleemann, CPC – Cellular Process Chemistry GmbH, Microreaction Technology, Available from- http://www.iptonline.com/articles/public/iptnine72noprint.pdf

[2] Sigma-Aldrich co website - http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Bulletin/1/al_chemfiles_v9n4.Par.0001.File.tmp/al_chemfiles_v9n4.pdf

[3] S R Buddoo, N Siyakatshana, and B Pongoma, Microreactors – A marvel of modern manufacturing technology: Biodiesel case study, Available from -http://researchspace.csir.co.za/dspace/bitstream/10204/2680/1/Buddoo_P_2008.pdf

[4] Karolin Geyer and Peter H. Seeberger, Microreactors as the Key to the Chemistry Laboratory of the Future, Available from - http://www.beilstein-institut.de/Bozen2008/Proceedings/Seeberger/Seeberger.pdf

Image Reference

Fig. 1): Dusemund Pte Ltd, website- http://www.dusemund.com/mikroglas/Microreaction%20Technolog1.pdf

Fig. 2): Transesterification with methanol to produce fatty acid methyl esters (FAME) - S R Buddoo, N Siyakatshana, and B Pongoma, Microreactors – A marvel of modern manufacturing technology: Biodiesel case study, Available from - http://researchspace.csir.co.za/dspace/bitstream/10204/2680/1/Buddoo_P_2008.pdf


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