Catalyst Separation, Recovery and Recycling

This book looks at new ways of tackling the problem of separating reaction products from homogeneous catalytic solutions. The new processes involve low leaching supported catalysts, soluble supports such as polymers and dendrimers and unusual solvents such as water, fluorinated organics, ionic liquids and supercritical fluids. The advantages of the different possibilities are discussed alongside suggestions for further research that will be required for commercialisation. Unlike other books, in addition to the chemistry involved, the book looks at the process design that would be required to bring the new approaches to fruition. Comparisons are given with existing processes that have already been successfully applied and examples are given where these approaches are not suitable. The book includes:

• New processes for the separation of products from solutions containing homogeneous catalysts

• Catalysts on insoluble or soluble supports - fixed bed catalysts - continuous flow or ultrafiltration

• Biphasic systems: water - organic, fluorous - organic, ionic liquid - organic, supercritical fluids (monophasic or biphasic with water, organic or ionic liquid)

• Comparisons with current processes involving atmospheric or low temperature distillation

• Consideration of Chemistry and Process Design

• Advantages and disadvantages of each process exposed

• Consideration of what else is need for commercialisation

  Homogeneous Catalysis: Separation, Recovery and Recycling

David Cole-Hamilton and Robert Tooze (Editors)

A volume in the Catalysis by Metal Complexes book series

This book looks at new ways of tackling the problem of separating reaction products from homogeneous catalytic solutions. The new processes involve low leaching supported catalysts, soluble supports such as polymers and dendrimers and unusual solvents such as water, fluorinated organics, ionic liquids and supercritical fluids. The advantages of the different possibilities are discussed alongside suggestions for further research that will be required for commercialisation. Unlike other books, in addition to the chemistry involved, the book looks at the process design that would be required to bring the new approaches to fruition. Comparisons are given with existing processes that have already been successfully applied and examples are given where these approaches are not suitable

The book includes:

New processes for the separation of products from solutions containing homogeneous catalysts

Catalysts on insoluble or soluble supports - fixed bed catalysts - continuous flow or ultrafiltration

Biphasic systems: water - organic, fluorous - organic, ionic liquid - organic, supercritical fluids (monophasic or biphasic with water, organic or ionic liquid)

Comparisons with current processes involving atmospheric or low temperature distillation

Consideration of Chemistry and Process Design

Advantages and disadvantages of each process exposed

Consideration of what else is need for commercialisation This book is an invaluable resource for industrialists in the chemical and pharmaceutical industries, particularly those involved with improving environmental impact of current or future processes. It is also a useful resource for academics who wish to apply homogeneous catalysis to solving real problems and for advanced undergraduate and postgraduate courses in catalysis.

If you are an industrialist interested in cleaner, cheaper synthesis, an academic interested in applying homogeneous catalysis as a synthetic methodology, or a practitioner looking to solve real technological problems then this book is for you.

Leseprobe

CHAPTER 2 CLASSICAL HOMOGENEOUS CATALYST SEPARATION TECHNOLOGY (p. 9)

DAVID R. BRYANT
2.1 Coverage of Chapter
When considering a separation technique for a homogeneous catalytic process, one must realize that catalyst/product/byproduct separation is an integral part of the entire process. The selection and design of the separation technology goes hand-in-hand with catalyst design, often in an iterative fashion.

That is, a catalyst is selected and tested in a continuous unit, with recycle of streams, to discover if there are problems that will necessitate redesign of the catalyst. Redesign is more often the fact than the exception. The objective of this chapter is to detail considerations that must be addressed in order to successfully marry a catalyst technology with catalyst/product separation technology. The focus of this chapter is hydroformylation, but the general principles should apply to many homogeneous precious-metal catalyzed processes.

2.2 General Process Considerations

There are four principal factors that are paramount in selecting the best separation technique. They are the energy required for the separation, the capital required for the equipment used in the separation, the efficiency/effectiveness of the separation, and the vitality of the catalyst after the separation. General process considerations include: Transitions of any type including temperature, pressure or phase changes should be minimized.

Cooling below 40 degrees Celsius becomes more expensive (river water cannot be used). Vacuum below 20 mm Hg is challenging. Byproduct formation should be minimized. Single product processes are better. A distillation column, or other step, will be required for each material in the mixture.

Everything feasible should be recycled so as to minimize waste. Pressures should be kept below 35 bar, at least below 100 bar, to minimize costs and because most process design experience is here. The use of rotating equipment such as compressors or centrifuges should be minimized to minimize maintenance costs.

Corrosive materials, particularly chloride, should be avoided. Batch operations should be avoided. The handling of solids should be avoided.

2.3 Everything is a Reactor

This may be a good time to introduce a very simple principal of process chemistry, but one that is not widely recognized. It is taught in chemical engineering that the only things in chemistry that matter are temperature and concentration. Every other variable can be reduced to these two. For example, time is simply a reflection of changing concentration.

Now a corollary: since every piece of process equipment has associated with it temperature and concentration, all pieces of process equipment are reactors. Stated differently, everything is a reactor.

There is a tendency to think that once the catalyst is removed from the reactor, all chemistry ceases. Chemistry is occurring throughout the process, and that is why separation of products cannot be viewed in isolation from the process that made them.

**2.4 Overview of Separation Technologies

2.4.1 TRADITIONAL COBALT WITH CATALYST DECOMPOSITION

Traditional cobalt hydroformylation separations will not be covered in detail since they have been described in many excellent references.

Inhalt
Homogeneous Catalysis Advantages and Problems.- Classical Homogeneous Catalyst Separation Technology.- Supported Catalysts.- Separation by Size-Exclusion Filtration.- Biphasic Systems: Water Organic.- Fluorous Biphasic Catalysis.- Catalyst Recycling Using Ionic Liquids.- Supercritical Fluids.- Areas for Further Research.