Heterogeneous catalysis

Technology
Technology details
Name:	Heterogeneous catalysis
Category:	Chemical conversion
Feedstock:	Wide range
Product:	Wide range

Heterogeneous catalysis is a catalysis in which the catalyst and the feedstock are different phases. In practice, this often means that the feedstock is a liquid or gas and the catalyst is a solid, also known as solid catalysis. Heterogeneous catalysis is the most widely used form of catalysis in the current chemical industry. There is a wide variety of catalytic systems and many reactions can be catalysed with a solid catalyst. Examples are pyrolysis, hydro-processing, oxidation, amination, dehydration, hydrolysis, (trans)esterification, and isomerisation. Common heterogeneous catalysts are heterogeneous solid base catalysts and heterogeneous solid acid catalysts.

Feedstock

Origin and composition

Due to the wide range of available catalysts and the large spectrum of reactions they can catalyse, the feedstock range for heterogeneous catalysis is significant. This ranges from biomass feedstocks such as lignocellulose, lignin, cellulose, sugars, and fatty acids, to products derived from biomass, such as glycerol and furfural.

Pre-treatment

The pre-treatment of the feedstock for a heterogeneous catalysis is depending on the specific process and feedstock used. In principal the feedstock normally is a liquid or gas so for solid feedstocks a conversion process like a pyrolysis or gasification or a solution is needed.

Process and technologies

Hydrogenation of ethene on a catalytic solid surface; (1) Adsorption, (2) Reaction, (3) Desorption

A wide range of processes and technologies can make use of heterogeneous catalysts. Examples are pyrolysis, hydro-processing, oxidation, amination, dehydration, hydrolysis, (trans)esterification, and isomerisation. The most common heterogeneous catalysts are heterogeneous solid base catalysts and heterogeneous solid acid catalysts. Base catalysts have a high concentration of basic sites that ensures the catalytic activity, often from Ba, Ca, Mg, and Sr and can be mixed or doped. Soap formation is a recurring drawback of these systems. Acid catalysts get their activity either from Brønsted or Lewis acidity and are commonly zirconia, silica, zeolites or zeotype materials. Major advantages of heterogeneous catalysis is the ease of separation, recyclability and high selectivity. Current development for future heterogeneous catalytic systems are in metal-organic frameworks (MOFs), magnetic catalysts, and solid phase ionic liquids.

Some large-scale industrial processes incorporating heterogeneous catalysts are listed below:

Process	Reactants, Product/s (not balanced)	Catalyst	Comment
Sulfuric acid synthesis (Contact process)	SO2 + O2, SO3	vanadium oxides	Hydration of SO3 gives H2SO4
Ammonia synthesis (Haber–Bosch process)	N2 + H2, NH3	iron oxides on alumina (Al2O3)	Consumes 1% of world's industrial energy budget
Nitric acid synthesis (Ostwald process)	NH3 + O2, HNO3	unsupported Pt-Rh gauze	Direct routes from N2 are uneconomical
Hydrogen production by Steam reforming	CH4 + H2O, H2 + CO2	Nickel or K2O	Greener routes to H2 by water splitting actively sought
Ethylene oxide synthesis	C2H4 + O2, C2H4O	silver on alumina, with many promoters	Poorly applicable to other alkenes
Hydrogen cyanide synthesis (Andrussov oxidation)	NH3 + O2 + CH4, HCN	Pt-Rh	Related ammoxidation process converts hydrocarbons to nitriles
Olefin polymerization Ziegler–Natta polymerization	propylene, polypropylene	TiCl3 on MgCl2	Many variations exist, including some homogeneous examples
Desulfurization of petroleum (hydrodesulfurization)	H2 + R2S (idealized organosulfur impurity), RH + H2S	Molybdenum-Cobalt on alumina	Produces low-sulfur hydrocarbons, sulfur recovered via the Claus process

Product

Heterogeneous catalysis is widely used throughout chemistry and a plethora of products can be made. Heterogeneous catalysis is often used in the production of biodiesel, but can also be employed in the pyrolysis process or in the production of many other value added chemicals.

Post-treatment

The post-treatment of the products of a heterogeneous catalysis is depending on the specific process and final products aimed for.

Process flow diagram illustrating the use of catalysis in the synthesis of ammonia (NH₃)

Technology providers

Technology comparison

Company name	Country	Technology category	Technology name	TRL	Capacity [kg/h]	Catalyst	Temperature [°C]	Feedstock: Food waste	Feedstock: Garden & park waste
Company 1	[Country HQ location]	[Technology category (if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]			●	●
Company 2	[Country HQ location]	[(if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]			●	●

Sigma-Aldrich

Heterogeneous catalysis provider

General information
Company:	Sigma-Aldrich
Country:	USA
Contact:
Webpage:	https://www.sigmaaldrich.com/NL/en/products/chemistry-and-biochemicals/catalysts/hydrogenation-catalysts
Technology and process details
Technology name:		Technology category:	Conversion (Chemical processes and technologies)
TRL:		Capacity:	kg·h-1
Catalyst:		Temperature:	°C
		Other:
Feedstock and product details
Feedstock:		Product:

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