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Making The Most Of It

Maximising aromatic assets in Oman.

Transforming low-value feedstocks into valuable products is a major goal of the petrochemical industry. Plant operators aim to maximise the production and purity of the desired products while reducing their overall costs.

Oman Oil Refineries and Petroleum Industries Company (Orpic) approached Zeolyst Specialty Catalysts* (ZSC) for assistance in enhancing the performance of its transalkylation unit. ZSC simulated the transalkylation process in a pilot plant test unit running Orpic feed and found that switching to ZSC’s ATA-21 catalyst would help with further process optimisation.

In most industrial catalytic processes, catalyst performance optimisation is a critical focus area. The study facilitated the decision to perform an early catalyst change out justified by the improved performance when using ATA-21 catalyst. Orpic planned a catalyst change out for the end of Q1 2013.

“Our main driver for catalyst replacement was to improve our economic benefit significantly by using the latest technology for transalkylation,” Chirag Patel, Orpic’s Process Optimisation Aromatics and Polypropylene Team Lead, explains. “The challenge was to select a catalyst that would improve productivity and help to debottleneck a specific unit. We chose ZSC’s ATA-21 catalyst on the basis of a techno-commercial evaluation of the proposed yields and the projected improvements of various catalysts.”

ATA-21 is the latest catalyst innovation in the ATA (advanced transalkylation) range of high-performance transalkylation catalysts developed and commercialised as a result of the partnership between ZSC, South Korea’s SK Innovation and Shell Technology Centre Amsterdam in the Netherlands. These transalkylation catalysts exhibit reliable high activity and efficiency for the treatment of heavy feedstocks.

Richard Mauer, Research Scientist, Shell Global Solutions, worked closely with the Orpic operations team to help meet Sohar’s goals. He says, “We were confident that ATA-21 would meet the challenge at Sohar based on our continual optimisation and pilot plant performance confirmation. The catalyst delivers very low aromatics loss and reduced hydrogen requirements, and offers high benzene purity. Low hydrogen requirements help to reduce utility or investment costs, and the catalyst’s outstanding stability means that a typical cycle can run from four to eight years, depending on the operating conditions.”

Orpic placed the commercial order for ATA-21 in December 2012; catalyst delivery to the Oman site was slated for February 2013. Manufacturing and delivering 60 tonnes of novel catalyst technology within such a tight schedule was a technical and logistical challenge, but the close collaboration of Shell Technology Centre Amsterdam, ZSC and SK Innovation enabled quick delivery of the first commercial catalyst samples to Amsterdam for catalyst evaluation and qualification.

To deliver on schedule, the team in the Netherlands worked diligently to deliver on this commitment. This was ZSC’s  first user of ATA-21 catalyst and its first transalkylation customer in the Middle East, so there was no room for error.

Mauer explains: “We knew that any time we lost would negatively affect our delivery schedule, so we did all that we could to meet key milestones and the deliver high-quality catalyst within the allotted time. When the catalyst was ready for shipment, extra measures were taken to meet the start-up schedule. Logistics were put in place to ensure that the catalyst would be on-site for installation and a successful start-up.”

“Selecting the ZSC catalyst and having it delivered to site in record time enabled Orpic to replace the old catalyst as planned and to gain the benefits associated with the new catalyst at the earliest opportunity,” affirms Patel. “The ZSC team was very helpful and flexible in its efforts to ensure the delivery of catalyst on the promised date and the safe start-up of the transalkylation reactor.”

There is often a breaking-in period following the introduction of a new transalkylation catalyst system. Typically, the high activity of the catalyst results in side reactions and affects the high benzene purity target. For the first 12 hours at Sohar, process adjustments were implemented to achieve the high benzene purity requirement with the inclusion of a stabiliser side stream.

Unlike some other catalysts on the market, within a few days, the performance of ZSC’s ATA‑21 catalyst stabilised and the operator was able to shut down the stabiliser side stream. In addition, the operating temperature was 80–90°C lower than that achieved with the historical catalyst charge. This start-of-run temperature reduction with ATA-21 helped to improve the energy efficiency of the aromatics unit further.

During the first few weeks of operation, ZSC received regular updates from Sohar. Two weeks into the production cycle, the plant operators were extremely pleased with the performance.

“The ZSC catalyst helped to increase conversion and yields of selected products (paraxylene and benzene) and reduced by-products such as heavy aromatics and low-cost blend material,” Patel says. “The quality of the benzene being produced improved substantially, which, in turn, resulted in debottlenecking of the extraction unit. Furthermore, the cost of olefin treatment came down because the products from the new catalyst system contain less unsaturated materials.”

“After a few months of operation following the introduction of the new catalyst, we could safely conclude that the performance of the Orpic aromatics complex had shown a marked improvement and enabled the company to achieve new production records for benzene. This changeout of catalyst was surely among our best achievements for Orpic in 2013,” adds Livio Accattatis, Orpic General Manager Technical Services.

involves transferring an alkyl group from one organic compound to another and enables operators to upgrade low-value streams (including heavy aromatics C9+ and toluene) to high-value feedstocks for paraxylene and benzene production.

*Zeolyst Specialty Catalysts is a division of Zeolyst International, a partnership between PQ Corporation and the Shell Global Solutions affiliate CRI/Criterion Inc.