Advances in Refining Catalysis

Deniz Uner, Deniz Uner

• Editore: CRC Press
• Anno: 2017
• ISBN:
  9781315353081
• Edizione: 1
• Argomento: Ciencias físicas
• Categoria: Química

To meet changing market demands that have stringent emission standards and to ensure proper performance in refinery units, evaluation of novel catalyst designs and results from material characterization and testing of catalysts are of crucial importance for refiners as well as for catalyst manufacturers. This book highlights recent developments in the application of refinery catalysts in selected units such as fluid catalytic cracking (FCC), hydrogen production for hydroprocessing units, hydrotreating, hydrocracking, and sustainable processing of biomass into biofuels.

Section II

Advances in Conventional Refining Technologies

3 Recent Developments in Hydrocracking Catalysts—Patent and Open Literature Survey*

Melek Bardakcı Türkmen

CONTENTS

3.1 Hydrocracking Technology in Perspective

3.2 Hydrocracking Process Chemistry and Catalysts in Perspective

3.3 Analysis Based on Patent Applicants and Countries of the Applicants

3.3.1 Involvement of Refineries

3.3.2 Involvement of Catalyst Manufacturers

3.3.3 Involvement of Universities/Research Institutes/R&D Companies

3.4 Analysis Based on Research Area

3.4.1 Developments in Terms of “Synthesis/Modification”

3.4.2 Developments in Terms of Feedstock-Based Technologies

3.4.3 Developments in Terms of Target Products

3.4.4 Developments in Terms of Performance Enhancements

3.4.5 Developments in Terms of “Ancillary Processes, Environmental, and Cost-Effective Aspects”

3.5 Future Prospects in Hydrocracking Technologies

References

* The review for the historical overview of the hydrocracking technology, process chemistry, and the developments of the catalysts has been performed by eight literature resources, namely Petroleum Refining Process (Speight, J.G. and Ozum, B.), Handbook of Petroleum Processing (David, S.J.J. and Pujado, P.R.), Petroleum Refining Vol. 3, Conversion Processes (Leprince, P.), Petroleum Refining Technology and Economics (Gary, J.H., Handwerk, G.E., and Kaiser, M.J.), Practical Advances in Petroleum Processing (Hsu, C.S. and Robinson, P.), Hydroprocessing of Heavy Oils and Residua (Ancheyta, J. and Speight, J.G.), Hydrocracking Science and Technology (Scherzer, J. and Gruia, A.J.), and Diesel Fuels Technical Review (Chevron) [1,2,3,4,5,6,7 and 8].

3.1 HYDROCRACKING TECHNOLOGY IN PERSPECTIVE

Hydrocracking is a refining technology within the scope of hydroprocessing that is used for the conversion of a variety of feedstocks to a range of products by adding hydrogen, removing impurities in the presence of a catalyst. Hydrocracking feeds, with higher molecular weights and lower hydrogen/carbon ratios, can range from heavy vacuum gas oils and coker gas oils to atmospheric oils, where products, having a lower molecular weight with higher hydrogen content and a lower yield of coke, usually range from heavy diesel to light naphtha [1,2].

Hydrocracking technology for conversion of coal to liquid fuels was developed in Germany as early as 1915. The forerunner of hydrocracking was the Bergius process, which may be considered as the first commercial plant and brought on stream in Germany in 1927 for hydrogenation of distillates-derived brown coal [2,3]. During World War II, hydrocracking processes played an important role in producing aviation gasoline. Nevertheless, after World War II, the emergent availability of Middle Eastern crude removed the incentive to convert coal to liquid fuels, which caused the development of hydrocracking technology to become less important as newly developed fluid catalytic cracking processes were much more economical than hydrocracking for converting high-boiling petroleum oils to fuels. In the mid-1950s, manufacturing of high-performance cars with high-compression ratio engines of the automobile industry required high-octane gasoline, where the switch of railroads from steam to diesel engines and the introduction of commercial jet aircraft in the late 1950s increased the demand for diesel fuel and jet fuel [2]. Thus, in the early 1960s, with the increasing demand for gasoline, diesel, and jet fuel, by-product hydrogen at low cost and in large amounts from catalytic reforming operations, and environmental concerns limiting sulfur and aromatic compound concentrations, hydrocracking technology gained importance again. And in 1958, the first modern distillate hydrocracker had been put into commercial operation by Standard Oil of California (now Chevron). It grew in other parts of the world, starting in the 1970s, primarily for the production of middle distillates, while hydrocracking was used in the United States primarily in the production of high-octane gasoline [2,4].

Hydrotreating and hydrocracking employ process flow schemes and similar catalysts where hydrocrackers tend to operate at more severe operational conditions as hydrotreaters are not conversion units through which breaking of carbon to carbon bonds is minimal. Hydrocrackers with higher severity in terms of process conditions have lower liquid hourly space velocity (LHSV), which means the given volume of feed requires more catalyst and higher pressure and temperature [5].

Hydrocracking is used to convert heavy fractions to lighter cuts similar to catalytic cracking, but unlike catalytic cracking, it is at relatively low temperatures and under high hydrogen partial pressures leading to inhibit rapid catalyst deactivation, which requires continuous regeneration of the catalyst during operation.

Since product balance is of major importance in any petroleum refinery, there are also relatively few operations that offer the versatility of the hydrocracking process, which has the ability to process high-boiling aromatic stocks produced by catalytic cracking or coking [1,4]. In general, hydrocracking is an in-between process that must be integrated in the refinery with other processes to take full advantage of the operations. As liquid, feed comes from the atmospheric/vacuum distillation, fluid catalytic cracking (FCC) bottom, delayed coker, or visbreakers, and the required hydrogen comes from catalytic reformers or steam/methane reformers or both. The outputs from a hydrocracker such as middle distillates usually meet finished-product specifications where heavy naphtha from a hydrocracker must be further processed in a catalytic reformer in the production of high-octane gasoline. The fractionator bottoms from a hydrocracker can be sent to an FCC, olefin, or lube plant [1,6].

Furthermore, conversion of heavy vacuum gas oil fraction into middle distillates requires not only a reduction in the number of carbon atoms but also an increase in the H/C ratio to get the desired product specifications, which also depend on the type of process. Naphtha cut, for example, can have a wide range of H/C ratio, where middle distillates must have a highly saturated structure to meet market quality requirements such as smoke point for jet fuel and cetane number for diesel cut [3].

Depending on the objectives chosen with respect to the type of feedstock, desired product quality, and degree of conversion, operating conditions are determined at the following range of conditions: liquid hourly space velocity (LHSV), 0.5 to 2.0 h^–1; H₂ circulation, 850–1700 Nm³/m³; H2PP, 10,300–13,800 kPa; and SOR temperatures ranging between 630.15 and 658.15 K [2]. In general, hydrocracker flow schemes can be grouped into two major categories: single-stage and two-stage operations. A single-stage once-through hydrocracking unit is the simplest configuration for a hydrocracking unit that resembles the first stage of the two-stage plant. The feed mixes with hydrogen before going to the reactor and the effluent goes to the fractionation. This type of hydrocracking unit has the lowest cost, but feedstock is not completely converted and highly refined heavy oil is required [1,2]. The once-through configuration is used when the fractionator bottoms are also the desired products. However, middle distillates obtained are of lower quality having higher aromatic content due to being operated at high-severity conditions in order to obtain high overall conversions [7]. In a single-stage recycle unit, which is the most widely found hydrocracking unit, unconverted feed is recycled by sending it back to the reactor section for further conversion [2]. This type of unit is more economical than a more complicated two-stage unit when the plant capacity is less than about 10,000–15,000 bbl/day. However, it is less selective for liquid products as compared with a two-stage configuration [1]. The two-stage hydrocracking process is also widely used especial...