Selecting the right catalyst system helps reduce operational issues
Selecting the right catalyst system helps reduce operational issues and improves manufacturers ability to meet customer performance supply requirementsperts.
The transformation of feedstock from its initial status to the final products requires a chemical reaction, which is performed under certain temperature and pressure conditions.
Also, it requires the presence of a catalyst, which is a key component for any chemical reaction.
“Catalysis plays an important role in the petrochemical and refining industries, as it provides alternative faster reaction routes with lower activation energy for desired reaction,” says Yassir Ghiyati, sales manager for the hydroprocessing technology division at Haldor Topsoe. “Simply - without catalysis, most reactions in the industry would not be feasible,” Ghiyati says.
Catalysts are a crucial component in the processing of highly valued products in all processing industries; therefore, there are a wide variety of catalysts which can be either heterogeneous or homogeneous, depending on whether a catalyst exists in the same phase as the substrate.
Heterogeneous catalysts act in a different phase than the reactants. Most heterogeneous catalysts are solids that act on substrates in a liquid or gaseous reaction mixture.
They are typically supported, which means that the catalyst is dispersed on a second material that enhances the effectiveness or minimises their cost.
Homogeneous catalysts function in the same phase as the reactants, but the mechanistic principles invoked in heterogeneous catalysis are generally applicable. Typically homogeneous catalysts are dissolved in a solvent with the substrates.
Due to its importance, companies tend to conduct a maintenance turnaround to change the catalyst used in the process, and the frequency of changing catalysts varies from one company to another.
“The frequency of catalyst change is dependent upon many factors, but is primarily driven by the changing needs of the polymer market place,” says Dr Mike Tilston, director, polypropylene R&D, The Dow Chemical Company.
“Typically a polymer producer will change a catalyst system every 3 to 5 years, but in some cases PP manufacturers have used the same catalyst system for up to 10 years or more without changing,” he adds.
The frequency of catalyst change depends on various factors. “This includes catalyst type, quality and amount,” says Ghiyati. “Feed quality and process severity also play an important role in addition to overall petrochemical plant and refinery plans for turnaround,” Ghiyati explains.
“Changing the catalyst type on a polypropylene manufacturing facility is a complex project, and often takes many months or sometimes years to complete. When a catalyst is changed, the properties of the polypropylene products produced will be changed, often requiring re-qualifications of customers,” says Dr Tilston.
Equally, most catalyst changes also require changes in operating conditions and therefore require re-training of operations staff.
“Dow has extensive experience in supporting our customer needs and changes in catalysts for polypropylene production.
A dedicated team of both operations and product specialists works extensively with the customer to ensure successful transition to the new catalyst technology both for the polypropylene producer and their customers,” explains Dr Tilston.
Failures related to the catalyst fall into two main categories, including product performance failures and manufacturing operational failures.
Product performance failures are usually related to subtle changes in the characteristics of the polymer produced which causes problems in the subsequent conversion to end products or the performance of the polymer in the end-use application itself.
Manufacturing operational failures caused by the catalyst can range from short-term reductions in rates of polypropylene manufacture, to long-term plant outages caused by severe plugging in the manufacturing facility.
“Our catalyst systems are unique in the industry today in that the donor systems are specifically engineered not only to control the characteristics of the polymer, but also to modify the operational characteristics of the catalyst, significantly reducing the possibility of operational upsets,” says Dr Tilston.
“Catalyst systems offered by Dow substantially improve operating time benefits compared to older generation technology.”
Procuring catalysts is a tough task for procurement managers who should be rigorous when purchasing catalysts.
“Procurement managers should make rigorous evaluations of catalyst proposals, taking into account the performance of the catalyst in its entire life. This is a philosophy which major refineries and petrochemical plants have already adopted,” says Ghiyati.
It is also critical that a procurement manager needs to focus on the total value of the catalyst system and not just the cost of the catalyst itself. “The performance of the catalyst has a major effect on essentially every aspect of the manufacturing operation and the products produced from the facility,” says Dr Tilston.
Choosing the right catalyst system can result in reduced operational issues, and an improved ability to meet or exceed customer performance supply requirements and end-use polymer performance requirements.
“A catalyst that has the correct operational performance characteristics can actually result in much higher overall business profitability than purchasing a low cost and inconsistent catalyst that does not meet these requirements,” explains Dr Tilston.
More than ever before, efficiency is the operator’s primary concern. “A good way for a refinery to reduce global catalyst expenses is to maximise the catalyst’s multiple uses, which is possible for a number of applications,” says Dr Saleh Abotten, general manager of Al Bilad Catalyst.
“The technique of ex-situ regeneration gives the best chance to recover the maximum performance, with the lowest chance for pressure drop build up in the reactor beds as well as improper liquid distribution,” concludes Dr Abotten.