The supply of conventional oil resources is declining, yet demand for fuels and energy production continues to grow worldwide. For countries whose economies are largely based on oil, such as Saudi Arabia, there is a pressing need to diversify and develop novel ways for utilizing the hydrocarbon fuels that remain. This will help bridge the inevitable gap between the decline of fossil fuels and the development of efficient, commercial-scale alternative energy sources.
Crude oil refineries focus predominantly on the production of transport fuels — diesel, jet fuel and gasoline — but also generate side-products including light hydrocarbons, ethylene and propylene which are the main building blocks for many petrochemical products, such as polypropylene and polyethylene (plastics), these are in increasing demand and are used in different applications, from household devices and electronic goods to toys and carpet fibres.
‘Cracking’ processes have long been used in the petroleum refineries as a means of generating different types of fuel from heavy hydrocarbons. Cracking involves breaking the chemical bonds in complex, long-chain hydrocarbons, like crude oil or naphtha, to create simpler, light, short-chain hydrocarbons like olefins. Such a process requires heat and the addition of catalysts to facilitate and speed up bond-breaking. In recent years, scientists have discovered that microwave energy is particularly useful for breaking carbon-hydrogen bonds, thanks to its high selectivity. Coupling microwave energy with specially designed catalysts will optimise the generation of light hydrocarbons from even the densest hydrocarbon residue products, such as bunker oil — the thick residual sludge left after refineries have produced all the useful fuels from crude oil. This will allow the oil industry to evolve as crude oil extraction dwindles and other, more sustainable energy sources begin to take over.
With this in mind, two of Saudi Arabia’s largest oil and chemical-related companies – Saudi Aramco and SABIC (Saudi Basic Industries Corporation) — have joined forces to build the first fully integrated crude oil-to-chemicals complex, known as COTC, in the kingdom. With a goal of pioneering the efficient production of high- quality, high-value chemicals from heavy hydrocarbons, the new complex will provide sustainable employment for the country, trial innovative technologies and help guide economic diversification away from reliance on crude oil exports. COTC will contribute considerably to Saudi’s Vision 2030 and aims to be fully operational by 2025.
International research to support Saudi complex
Such an ambitious project requires much planning and progressive, ambitious research to provide the backbone for its success. For the last eight years, scientists from the Materials Science Research Institute at King Abdulaziz City for Science and Technology (KACST) in Riyadh and researchers at Oxford University in the UK have been working together at the KACST-Oxford Petrochemical Research Center (KOPRC)1,2.
The joint centre has already developed a wide range of catalysts and pioneered new processes in the field of petroleum refining and petrochemicals. In addition to that, the centre provides opportunities for post-graduate exchange students.
KOPRC’s most recent projects focus on optimizing the microwave-enhanced conversion of crude oil into various chemicals and hydrogen fuel. The joint venture has published more than 20 papers and organised seven annual forum meetings, which have taken place in Oxford and Riyadh.
KOPRC researchers are trialling a technique not previously used in the oil industry called microwave-dielectric heating3, which is similar to the process used by a microwave oven to heat food. Some molecules absorb microwave radiation as it passes through a substance, especially molecules that are in liquid form. This causes the molecules to vibrate, raising their temperature.
Microwave heating is rapid, uniform and selective, meaning that target materials can be heated in a controlled manner. In order to use microwave radiation to heat bunker oil and break it down into olefins, KOPRC researchers are designing catalysts that can enhance the system’s efficiency and guide the production of specific target chemicals.
This process is not completely new — the use of synthetic porous minerals called zeolites as catalysts transformed oil refining from its early days. The crude oil or components of the oil are injected on to hot, fluid zeolites, triggering cracking of the larger hydrocarbon molecules into smaller ones.
While catalysts can be reused several times, eventually the zeolites can become coated in coke — a by-product of the cracking process that deactivates them. The KOPRC research team recently developed a method using microwaves to analyse zeolites under an electromagnetic field and measure the amount of coking present, both on the surface and inside the catalyst. These insights will provide further understanding of the extent of coking and ultimately improve the catalysts.
Another major challenge will be the successful transformation of crude oil into high-purity hydrogen gas and residual carbon. This could provide a valuable source for the much-anticipated hydrogen fuels of the future. Indeed, KOPRC published a paper in the journal Scientific Reports, in 20165, demonstrating that hydrocarbon wax, a benign, readily-available by-product of the petrochemical industry, can release large amounts of hydrogen under microwave-assisted catalytic decomposition. Their results could pave the way for using the wax to safely store hydrogen on hydrogen-powered fuel cell vehicles.
Another project at KOPRC aims to design compact, single units for microwave-enhanced conversion of crude oil and naphtha — a liquid hydrocarbon derivative of crude oil refining — in the laboratory. The Saudi Aramco ‘oil-to-chemicals’ research and development team are working in close collaboration with KOPRC scientists to assess the potential for this emerging manufacturing equipment.
The KOPRC research might improve the environmental credentials of the oil industry by reducing and reusing waste products. A novel technique developed by scientists at KOPRC in collaboration with Jinghai Li at the National Natural Science Foundation of China could help mitigate the impact of emissions from the petrochemical industry by converting flue gases into usable fuels and chemicals2. Flue gas reforming converts waste gases such as carbon dioxide and nitric oxide into synthetic gas using specially designed catalysts during standard oil refining processes. This synthetic gas can in turn be used to create clean fuels and industrial chemicals without the need for carbon capture and storage. The team are hoping to optimise their technique with a goal of creating a carbon-neutral or even carbon-negative process.
The research conducted at KOPRC will ensure that the new crude oil-to-chemical complex in Saudi Arabia will be off to a flying start when it opens in 2025. The researchers at KACST and Oxford University will continue their fruitful partnership and will redouble their efforts to lead the way in developing microwave-assisted oil refining processes and finding cleaner, more sustainable energy sources for the future.
- . Porch, A., Slocombe, D., Beutler, J., Edwards, P., Aldawsari, A. et al. Microwave treatment in oil refining. Applied Petrochemical Research 2, 37-44 (2012). | article
- Liu, B., Slocombe, D.R., Wang, J., Aldawsari, A., Gonzalez-Cortez, s., et al. Microwaves effectively examine the extent and type of coking over acid zeolite catalysts. Nature Communications 8, 514 (2017). | article
- Gonzalez-Cortes, S., Slocombe, D.R., Xiao, T., Aldawsari, A., Yao, B. et al. Wax: a benign hydrogen-storage material that rapidly releases H2-rich gases through microwave-assisted catalytic decomposition. Scientific Reports 6, 35315 (2016). | article