G.E. Dolbear & Assoc- Glossary of Petroleum Refining Terms

G.E. Dolbear & Assoc

Glossary of Petroleum Refining Terms
From the book, "Petroleum Catalysis in Nontechnical Language", by John Magee and Geoffrey Dolbear; copyright 1998 by Pennwell Publishing Company, Tulsa, OK; the book is available from Amazon or directly from the publisher at http://store.yahoo.com/pennwell/petcatinnonl.html c1998 Pennwell Publishing Co.
Absorb	Describes what happens when a molecule from a fluid phase (gas or liquid) dissolves in a solid. Absorb is different from adsorb (which see).
Acid Sites	Locations on a solid that have acidic properties, as shown by their ability to react with a base such as ammonia or pyridine. Acid sites are found on many solid oxides and are active for catalyzing reactions.
Activation Energy	Measure of the sensitivity of a reaction rate to increase in temperature. Activation energy is related to the fundamental energetics of a molecular reaction.
Active Matrix	Catalyst matrix with catalytic activity. See Matrix.
Active Site	Location on a catalyst surface where reaction takes place.
Adsorb	Describes what happens when a molecule from a fluid phase (gas or liquid) lands on the surface of a solid and stays, if only for a short while. Adsorb is different from absorb (which see).
Aliphatic	See alkane.
Alkane	Any hydrocarbon molecule with the maximum ratio of hydrogen to carbon. The general formula for alkanes is C_nH_2n+2, where n is 1, 2, 3, etc.
Alkanes	Hydrocarbon molecules with the maximum ratio of hydrogen to carbon. The general formula for alkanes is C_nH_2n+2, where n is 1, 2, 3, etc.
Alkylation	Processes that combine small molecules in pairs to make a larger molecule; butane alkylation uses strong acid catalysts (sulfuric or hydrofluoric acid) to combine isobutene with isobutane, producing isooctane.
Alumina	Aluminum Oxide, Al₂O₃. Exists in a variety of forms, many with high surface areas. Aluminas are very important catalyst supports and catalyst components
Alundum	The thermally stable, low surface area, crystalline form of alumina; formally a -Al₂O₃.
Aromatic	A large family of hydrocarbon compounds based on the benzene structure. Chemists link the name aromatic to the exceptional stability that derives from the benzene structure; see Benzene.
Asphaltenes	A class of organic materials defined by their insolubility in pentane or heptane. Asphaltenes are generally polar molecules, rich in S, N, O, and organically bound Ni and V. The vast majority of asphaltenes distill at temperatures above about 1000° F (540° C). They are an important component of asphalt.
Attrition Resistance	Strength of a catalyst as measured by its ability to hold together when being fluidized in a stream of air.
Benzene	The simplest aromatic compound, consists of six carbons and six hydrogens. The six carbons are linked in a ring and each carbon has a single hydrogen bound to it. C-C double bonds are found between alternate pairs of carbons. It is this continuous double bond structure that provides the This structure is exceptionally stable and virtually impossible to crack open without adding hydrogen to generate cyclohexane. Benzene is poisonous, attacking the liver, and a known carcinogen. See Aromatic.
BET	Method for measuring the surface area of catalysts and other high area materials using adsorption of nitrogen gas. Named for Brunauer, Emmett, and Teller, who developed the method.
Boiling Point Range	A convenient way of describing a petroleum fraction is to measure the lowest and highest temperature at which some of the molecules in the fraction will distill. See Carbon Number.
BPCD	Barrels per calendar day. Measure of the rated capacity of a process unit or operation. Defined as 1/365th of the annual throughput. This measure accounts for down time for maintenance, etc. An alternate measure is barrels per stream day, the measure of the maximum daily capacity. On-stream factor is the ratio of BPCB to BPSD.
Brønsted Acid Site	An acid site on a catalyst where the acidic entity is an ionizable hydrogen. Familiar mineral acids such as sulfuric are also acids of this type, named for the physical chemist J. N. Brønsted. See also Lewis Acid Site.
BTX	Benzene, toluene, and xylene. These aromatic molecules are very important components of gasoline and petrochemicals. Benzene, the simplest aromatic, is carcinogenic and its level in gasoline is severely restricted. Toluene and xylene have benzene rings to which are attached one or two methyl (CH₃) groups, respectively; xylene has three isomers, with the methyls adjacent on the ring (ortho), separated by one carbon (meta), or separated by two carbons (para); see figure.
Calcine	Describes the high temperature treatment of catalyst precursor materials, converting them to strong, stable solids. The term comes from ceramics technology, where calcining or firing is used to convert clay intermediates (green materials) to finished products.
Carbenium Ion	A general term describing positively charged carbon-containing compounds. Generally, carbenium ions are unstable reaction intermediates. Many acid catalyzed reactions of petroleum involve carbenium ion intermediates. These are sometimes called carbocations and, in the past, were known as carbonium ions.
Carbon Number	A way of describing the size of hydrocarbons in terms of the total number of carbons in the molecule. Boiling points of hydrocarbons generally increase with carbon number.
Catalyst	Any substance that changes the rate of a reaction without itself being changed in the reaction; catalysts can be solids, liquids or gases, and they may be individual molecules that are dissolved in a liquid containing the reacting molecules. The most common industrial catalysts are solids used in treating feeds that are liquids or gases.
Catalyst Support	Any of a variety of materials that a catalytically active material is coated on. Generally not involved in the catalytic reaction, supports are important because of their interactions with the active material.
Coke	In catalysis, refers to a carbon-rich deposit that can form on the surface, often blocking access to active sites.
Conradson Carbon Residue	A measure of the tendency of a carbonaceous material to form coke.
Continuous Regeneration System	Any process step that treats catalyst removed from a reactor to restore its activity (regeneration) and return it to the reactor.
Conversion	In refinery parlance, conversion is changing the boiling point distribution of a feed, usually predominantly to lower boiling fractions.
Cracking	A general term covering any of a variety of reactions and processes that convert high boiling fractions to more valuable lower boiling fractions.
Cyclic Fixed-Bed System	A process were the feed and conditions in a catalytic reactor are changed regularly in an alternating fashion. The most common example is where the reaction deposits coke; feed is passed through the bed continuously until the activity falls to a low level; then the bed is purged of hydrocarbon feed and heated under air or oxygen to remove the coke. Finally the bed is purged of oxygen, and feed is once again introduced. See Fixed-bed Catalyst.
Desulfurization	Any process or process step that results in removal of sulfur from organic molecules.
Diatomaceous Earth	A mineral formed by deposition of siliceous remains of diatoms, microscopic aquatic life forms. Diatomaceous earth has long been used as a catalyst support. Also known as Kieselguhr.
Double-Bond Isomers	Two or more olefinic compounds with identical molecular formulas but having the double bond at different locations in the molecule.
Dual-Function Catalyst	Any catalyst with two distinctly different catalytic functions, such as cracking and hydrogenation. Examples are platinum reforming and hydrocracking catalysts.
Emulsion	A mixture of two materials, where micron scale particles of a solid or liquid are dispersed in a liquid where it does not dissolve. Common emulsions have oil dispersed in water (e.g. milk and mayonnaise) or water dispersed in oil (margarine). Common cleaning agents and greases are also emulsions. Stable emulsions require the presence of a surface active agent (surfactant), often a detergent or soap, that accumulates at the interface between the two kinds of materials.
Endothermic	Reactions that proceed with absorption of enthalpy (heat energy) are termed endothermic; see exothermic.
Equilibrium Catalyst	In FCC, mixtures of fresh and used catalysts of various ages as found when small amounts of fresh catalyst are added daily, or more often, to maintain some activity level. Equilibrium catalysts can be purchased on the open market. See FCC.
ETBE	Ethyl-t-butyl ether, an oxygen-containing fuel component used in reformulated gasoline. Commonly made from ethanol (ethyl alcohol) and isobutene.
EXAFS	Extended x-ray absorption fine structure spectroscopy, a technique used to characterize detailed structures on the surfaces of catalysts and other solids.
Exothermic	Reactions that proceed with release of enthalpy (heat energy) are termed exothermic; see endothermic.
Extrudates	Catalyst particles that are made by forcing a paste of catalyst precursor material through a hole in a steel plate, called a die, to form a spaghetti-like solid. The solid is dried and broken into short segments to form the final product.
Faujasite	A naturally occurring zeolite mineral. The synthetic zeolites X and Y have the same crystallographic structure as Faujasite.
FCC	Fluid catalytic cracking. A process for converting high boiling gas oils to lighter liquids, primarily gasoline range naphtha and diesel range gas oils. The most widely practiced refinery conversion process.
FCCU	Fluid catalytic cracking unit. Process equipment for carrying out the FCC process.
Fines	Powder formed as product of unintentional fracturing, grinding, and attrition of catalyst particles.
Fischer-Tropsch Chemistry	Family of reactions combining carbon monoxide with hydrogen to create hydrocarbons, with water as a coproduct. Composition of products varies with catalyst.
Fixed-Bed Catalyst	Any catalyst used in a reactor where the catalyst fills the reactor and remains motionless (fixed) and the gas and/or liquid feed mixtures flows past. The fluid flows through the void spaces between catalyst particles.
Fluid Catalytic Cracking	See FCC.
Fluid-Bed Catalyst	Any catalyst used in a fluidized bed. When gas is allowed to flow upward through container filled with fine powder at a sufficient velocity, the gas-solid mix exhibits the properties of a boiling liquid. Catalysis under these conditions can be very efficient because of the thorough mixing. At higher gas velocities, the solids may be carried out of the bed and upward through the container. Such systems are called transport or riser reactors.
Forming	Any process designed to convert catalyst precursor mixtures into useful solid forms.
Free Radical	Any molecular fragment containing an unpaired electron. Such fragments are often very reactive, reacting with nearby molecules as fast as they encounter them. Radicals formed on the surface of catalysts may be much more stable and able to undergo more selective chemistry. This is due to the stabilizing influence of the surface.
Friedal Crafts Reactions	Family of reactions, catalyzed by strong acids, that are responsible for alkylation.
Gas Oil	General term describing any distillable refinery stream boiling above about 350° F. Diesel, turbine, and jet fuels are blended from gas oils. Higher boiling gas oils are called heavy.
HCO	Heavy cycle oil A fraction of FCC product liquid distilling above about 700° F.
HDN	See Hydrodenitrogenation.
HDS	See Hydrodesulfurization.
HTS	High-temperature shift. One of the process steps in hydrogen manufacture, involving the water-gas shift reaction.
Hydride Ion Abstraction	Reaction of strong acid with C-H bond, where hydrogen is removed as a negative ion, hydride, yielding a carbenium ion.
Hydrocarbon	Strictly defined as molecules containing only hydrogen and carbon. The term is often used more broadly to include any molecules in petroleum, which also contains molecules with S, N, O, and various organically bound metals.
Hydrocracking	Process, or family of processes, combining hydrogenation of olefins and aromatics with catalytic cracking.
Hydrodenitrogenation	Hydrotreating processes that remove nitrogen from feeds; these are usually also effective for hydrodesulfurization. See Hydrotreating.
Hydrodesulfurization	Hydrotreating processes that remove sulfur from feeds; these are usually not also effective for hydrodesulfurization. See Hydrotreating.
Hydrogen Transfer	Some catalyst that are not designed as hydrogenation catalysts nonetheless have the ability, under operating conditions, to transfer hydrogen atoms from one reactant molecule to another.
Hydrotreating Catalysts	Catalysts that operate in an hydrogen environment and function to remove heteroatoms (S, N, O, Ni, V, etc.) and add hydrogen to olefins and aromatics.
Impregnation	Process for making a catalyst in which catalyst precursor materials dissolved in water or some other solvent soak into a high surface area support material.
Incipient Wetness	Condition when just enough liquid has been added to a porous solid to just fill all the pore. If more liquid is added to the mixture, it coats the outer surface, changing the appearance from dull to glistening. On drying, catalyst materials added in an incipient wetness impregnation will deposit in the pores rather than on the outer surface.
Isomer	When two molecules have the same elemental composition but different structures, they are said to be isomers.
Isomerization	The process of changing a molecule into one or more of its isomeric forms. See Isomer.
LCO	Light cycle oil. A fraction of FCC product liquid distilling between about 400° F and about 700° F.
Lewis Acid Site	An acid site on a catalyst where the acidic entity is a positive ion (called a cation) such as Al³⁺ rather than an ionizable hydrogen. Named for the famed physical chemist G. N. Lewis. See Brønsted Acid Site.
Liquefied Petroleum Gas	Generally, any light hydrocarbon fuel that must be compressed to keep it from boiling away. (LPG) Commercial LPG usually contains mixtures of propane (C₃H₈) and butane (C₄H₁₀).
LPG	Liquefied Petroleum Gas.
LTS	Low-temperature shift. One of the process steps in hydrogen manufacture, involving the water-gas shift reaction.
Matrix	Major component of catalysts, often an inert supporting material. Typical matrix materials include silica, alumina, and various clays.
Modifier	In catalysis, any metal or oxide added to a catalyst to change its activity, selectivity, or aging behavior.
Molecular Sieves	Any of a variety of high surface area solids having pores roughly the size of individual molecules and thus able to adsorb smaller molecules while excluding larger ones.
MON	Motor octane number. One of two ASTM tests for octane measures MON, predicting behavior at high speed operation. MON is generally lower than RON. See Octane Number.
Moving-Bed Catalyst	Moving bed catalytic processes add fresh or regenerated catalyst to the top of a reactor bed while simultaneously removing less active, used catalyst from the bottom. An important current example is UOP’s CCR reforming process. Catalysts for these processes must have physical shape and strength to survive this continued movement.
MTBE	Methyl-t-butyl ether, an oxygen containing fuel component used in reformulated gasoline. Commonly made from methanol (methyl alcohol) and isobutene.
Naphtha	Any low boiling refinery stream. Gasoline is made by blending several virgin and treated naphthas.
Octane Number	Measurement of the resistance of gasoline to explosive preignition, also known as knocking. Reference is to 2,2,4-trimethylpentane (isooctane) mixtures with n-heptane, with pure isooctane defined as 100.
Olefins	Hydrocarbon molecules containing carbon-carbon double bonds. The name olefin comes from roots the imply oil former. The general formula for olefins is C_nH_2n, where n is 1, 2, 3, etc. Olefins are not found in crude oil, but are formed during cracking reactions in many refinery processes.
Organic	In chemistry, refers to carbon-containing molecules. At one time, chemists believed incorrectly that such molecules could only be made by living plants and animals or by doing reactions with such molecules.
PA	Powdered alumina, used in making catalysts.
Paraffins	Synonym for alkanes. The name paraffin often refers specifically to alkane molecules (isomers) having long straight chains. These are the constituents of common candle wax.
Platinum Reforming	Process for increasing the aromatic content of naphtha by passing the naphtha and hydrogen over a catalyst containing platinum supported on alumina. See Naphtha, Aromatic.
Poison (Catalyst)	Any molecule or material that tends to collect on a catalyst surface, blocking access to active sites or destroying their activities.
Pore Structure	In high surface area solids, the structure as observed under a microscope resembles a sponge, with the holes being called pores. Detailed pore structure includes micropores of molecular size, macropores thousands of times larger, and mesopores of intermediate size.
Prilling	A process for making catalyst particles by dripping a liquid precursor into a bath of oil, usually in a tall cylindrical reactor called a prilling tower. Prilling is also widely used in forming particles of synthetic fertilizers.
Promoter	Any component added to a catalyst to increase activity or selectivity. Examples are tin added to platinum reforming catalysts to improve selectivity to coke formation and chloride added to isomerization catalysts to increase activity.
PSA	Pressure swing adsorption. Technique for separating gases from a mixture using adsorbents that discriminate by molecular size.
PSD	Pore Size Distribution. See Pore Structure.
Rare Earth	A group of fifteen closely related elements, not so rare as once thought. They are also called lanthanides for lanthanum, the lead member of the group. Mixtures of rare earth ions are used as components in FCC catalysts.
Reactor	Any of a variety of containers for carrying out refining, chemical, or other similar processes. Often reactors are little more than large tanks, but they can be very sophisticated, with methods for mixing reactants and controlling temperature.
Reformate	Highly aromatic naphtha made by platinum reforming. See Aromatic, Platinum Reforming.
Reforming	See Platinum Reforming, Steam Reforming.
Regeneration	A general term applying to any process or step that treats are used catalyst to restore fresh activity. In an FCC Unit, specifically refers to the step where coke is removed by burning in air.
REHY	Rare Earth Hydrogen Y Zeolite. A cracking catalyst component. See REY, REUSY, Type Y Zeolite.
Reid Vapor Pressure	A specific test measuring the presser of light molecules that evaporates from gasoline under carefully defined conditions. Gasolines are blended to have Reid Vapor Pressure (RVP) in the range 7 to 10 pounds per square inch, with variations with season and elevation to allow easy starting without excess air pollution.
Resid	Short for Residuum. General term for any refinery fraction that is left behind in a distillation. Atmospheric resid, sometimes called long resid or atmospheric tower bottoms (ATB), is the undistilled fraction in an atmospheric pressure distillation of crude oil. Likewise, vacuum resid, short resid, or vacuum tower bottoms (VTB), is the undistilled fraction in a vacuum distillation.
RET	Reactor entry technician. Person who works inside a reactor during the loading of a catalyst.
REUSY	Rare Earth Ultra Stable Y Zeolite. A cracking catalyst component made by ion exchanging rare earth (lanthanide) metals into ultra stable type Y molecular sieves. See Rare Earth, USY, Type Y Zeolite.
REY	Rare Earth Y Zeolite. A cracking catalyst component made by ion exchanging rare earth (lanthanide) metals into sodium Y molecular sieves. See Rare Earth, Type Y Zeolite.
Riser Reactor	The cracking portion of the FCC process, essentially a hundred foot tall vertical pipe. Oil, hot catalyst, and steam are injected continuously into the bottom of the riser, and the reaction occurs as the mixture rises to the top. Residence times in risers are typically one to two seconds. Risers are one of a general class of transport reactors, where reactions occur in dilute phase as the feed mixtures pass through a pipe. See Fluid Bed Reactor.
RON	Research octane number. One of two ASTM tests for octane measures RON, predicting behavior under acceleration at low speed. RON is generally higher than MON. See Octane Number.
RVP	See Reid Vapor Pressure.
SAC	Solid alkylation catalyst. Conventional butane alkylation processes use sulfuric or hydrofluoric acid as catalysts. For many years, catalyst developers have searched for a solid catalyst that could be used for this application. Several candidates, and associated processes, have emerged, but none has yet shown itself economically competitive with the liquid acids. This situation may well change in the next decade.
Saturated Hydrocarbon	A molecule containing only hydrogen and carbon and having all olefinic and aromatic double bonds removed by addition of hydrogen.
Selectivity	Many reactions can potentially occur in any real catalyst systems. Selectivity is the measure of the ability of the catalyst to promote desired reactions without affecting those that are not desired.
Semi-Regenerative Fixed-Bed System	One of several types of platinum reforming processes.
Shape Selectivity	The ability of a porous catalyst to discriminate against certain kinds of reactant molecules based on molecular shape.
Sintering	The generalized process by which high surface area materials lose surface area without melting.
Size Selectivity	The ability of a porous catalyst to discriminate against certain kinds of reactant molecules based on molecular size.
Skeletal Isomers	A group of compounds having the same empirical composition but where the atoms are linked in different patterns. See Isomer.
Sock Loading	Method of pouring catalyst particles into a reactor where the particles are allowed to fall down a long cloth bag (the sock) that is open at the bottom onto the growing catalyst bed; the friction of the sock slows the fall of the particles and thus is less likely to fracture them than pouring directly through open air from above. Sock loading also allows a technician to load the reactor more evenly by directing the catalyst particles back and forth across the bed rather than allowing a conical pile to form.
Sol	Refers to a dry colloidal particle, as opposed to a gel, which contains water or other solvent.
Spray Dryer	Equipment which forms uniform spherical particles by spraying droplets of a slurry or solution into hot air or flue gas, where the particles dry rapidly by evaporation.
Steam Reforming	Catalytic process for converting a mixture of steam and hydrocarbon to synthesis gas, a mixture of hydrogen and carbon monoxide.
Stripper	Refers to any system designed to remove ("strip") adsorbed liquid from a catalyst particle by subjecting it to a flowing stream of some other fluid. Typically steam is used to strip hydrocarbons from catalysts.
Surface Area	Measure of the amount of surface presented by a catalyst particle to a reaction system. Many catalysts have surface areas in excess of 100 M²/gm.
Surface Energy	Thermodynamic energy associated with the formation of a surface by fracturing a solid.
Synthesis Gas	A mixture of hydrogen and carbon monoxide useful as a feed for making hydrogen, ammonia, methanol, and various hydrocarbons, depending on the catalyst.
TAME	Tertiary-amyl methyl ether, an oxygen containing fuel component used in reformulated gasoline. Commonly made from methanol (methyl alcohol) and isopentene.
TEM	Transmission electron microscope. An electronic microscope using beams of electrons rather than light to examine a sample. TEMs are capable of observing features as small as a few angstroms.
TIR	Temperature increase requirement. A measure of the loss in a catalyst’s activity; reactions invariably go faster at higher temperatures, and the TIR measures the increase in temperature to bring activity back to a previous level; it may also measure the increase of temperature per day or week to maintain activity.
Type Y Zeolite	Faujasite zeolite with ratio of Si/Al greater than 1.5. Y zeolites have pores the size of common molecules and are very useful in refining reactions.
Unit Cell	In crystallography, the smallest fragment of a crystal that is exactly reproduced in the construction of the crystal lattice. Opposite sides of a unit cell are parallel, and the distances along the edges measure unit cell size. In the description of zeolites used in FCC catalysts, unit cell sizes vary with the atomic Si/Al ratio in the unit cell.
Unsaturated Hydrocarbon	Any hydrocarbon containing olefinic or aromatic structures. See Hydrocarbon, Olefin, Aromatic.
USY	Ultra Stable Y zeolite. A form of Type Y Zeolite (which see) with the majority of sodium ions removed and treated thermally to enhance its thermal and steam stability. USY has proved exceedingly useful in FCC catalysts.
Water Gas Shift	A reaction of synthesis gas, where water and carbon monoxide react to form hydrogen and carbon dioxide: H₂O + CO = H₂ + CO₂ see Synthesis Gas.
Zeolite	Any of a large family of crystalline metal oxide materials characterized by the presence of extensive regular interconnected pore systems. Most are based on mixtures of aluminum and silicon oxides, while others have phosphorous and other elements as well. See Molecular Sieve.