(29b) Performance of Bimetallic Hydroprocessing Catalysts for LCO Upgrading in Liquid-Full Isotherming Reactors

DuPont™ IsoTherming^® Hydroprocessing technology is emerging as a cost-effective alternative to the traditional trickle-bed reactors in refinery hydroprocessing applications. Performances of many hydrotreating and hydrocracking catalysts have been observed in a pilot plant setting as well as in commercial operation. Most of the catalysts are bimetallic and contain nickel or cobalt with molybdenum or tungsten on an alumina support for hydrotreating applications and on a zeolite support for hydrocracking applications.

In the refining industry, highly aromatic light cycle oil (LCO) offers a limited market value due to its low cetane value, high density, and high sulfur content. LCO must undergo hydrotreatment in order to meet diesel product specifications, but the highly reactive nature of the hydrocarbon stream causes complications with regards to supplying the necessary hydrogen and managing the considerable exothermic heat release. There are commercial units using conventional trickle-bed technology to process the LCO with the use of hydrotreating and hydrocracking catalysts to meet product specifications, but often at a significant yield of the primary diesel product.

Materials and Methods

Continuous pilot plant tests were conducted using a bench-scale reactor system containing 1" O.D. by 20" long flow reactors. Temperature, pressure, and gas & liquid flows in this continuous pilot unit were controlled using a PLC system. Multiple reactors packed with commercial bimetallic hydroprocessing catalysts, each reactor corresponding to a catalyst bed in a commercial reactor, were used in the pilot tests. Business goal was to conduct several weeks long tests using a customer supplied LCO feed to obtain the kinetic information for preparing a commercial licensing proposal. In a typical test, the commercial catalyst was dried, sulfided and stabilized (pre-coked) in the first week. One to two data points were then obtained per day in the remainder of the test at different temperature, pressure, and liquid/gas flow rates. Feed and product samples were analyzed to obtain sulfur & nitrogen removal kinetics, as well as the chemical hydrogen consumption rate and the aromatic saturation level. Feed and total product samples (TLP) were also distilled to obtain the relative naphtha and diesel yields.

Results and Discussion

IsoTherming^® technology offers a one- and two-stage process to hydrotreat highly aromatic LCO using commercial bimetallic hydrotreating (HT) and hydrocracking (HC) catalysts to meet the desired product specifications while also maximizing product yield. While commercial trickle-bed processes often result in diesel yields of about 50-60%[1], a one-stage IsoTherming^® process, consisting of both HT and HC catalysts under a single liquid recycle, have resulted in diesel yields of up to 80%[2]. The efficacy of the zeolitic cracking catalyst may be further increased and yields greater than 90% achieved in a two-stage IsoTherming^® process [3] [4] [5] [6], which includes a separation step between the hydrotreating and hydrocracking sections to remove dissolved ammonia that has a poisoning effect.

The intermediate separating step could be a simple high pressure flash alone, or in combination with a stripper or a fractionator. The value of the desired product plus the relative magnitude of the associated capital expenditures, the reduction of the product yield loss and the utility savings, determine the most economical option.

This presentation will discuss pilot plant tests of LCO hydroprocessing in IsoTherming^® reactors using commercial, bimetallic hydrotreating and hydrocracking catalysts including tests with and without a separation step after hydrotreating (as is the case of a two-stage and one-stage process, respectively). The examples will demonstrate the principles and the advantages of the liquid-full IsoTherming^® reactors over the traditional trickle-bed reactors used in refineries today.

Significance

Liquid-full IsoTherming^® reactors offer advantages over the traditional trickle-bed reactors for hydroprocessing of oil refinery streams. The advantages and the basic operating principles of the IsoTherming^® reactors are demonstrated for Light-Cycle Oil (LCO) upgrading for maximum diesel production.

References

1. Thakkar, V.P. et al. LCO Upgrading, AM, 05-53, NPRA, p. 1-15, 2005.
2. Dindi, H., et al. Hydroprocessing light cycle oil in liquid-full reactors, US 8,721,871 (2014)
3. Dindi, H., et al. Targeted Pretreatment and Selective Ring Opening in Liquid-full Reactors, US 9,139,782 (2015)
4. Dindi, H., et al. Hydroprocessing light cycle oil in liquid-full reactors, US 9,139,783 (2015)
5. Dindi, H. et al. Liquid-full Hydrotreating and Selective Ring Opening Processes, US 9,212,323 (2015)
6. Dindi, H., et al. Hydroprocessing light cycle oil in liquid-full reactors, US 9,139,783 (2016)