Pressure reactor

Last updated May 03, 2019

A Pressure Reactor, sometimes referred to as a pressure tube, or a sealed tube, is a chemical reaction vessel which can conduct a reaction under pressure. A pressure reactor is a special application of a pressure vessel. The pressure can be caused by the reaction itself or created by an external source, like hydrogen in catalytic transfer hydrogenation.

A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.

Hydrogenation – meaning, to treat with hydrogen – is a chemical reaction between molecular hydrogen (H₂) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule, often an alkene. Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures. Hydrogenation reduces double and triple bonds in hydrocarbons.

Advantages

A pressure reactor can offer several advantages over the conventional round-bottom flask. Firstly, it can conduct a reaction above the boiling point of a solvent. Secondly, the pressure can reduce the reaction volume, including the liquid phase, and in turn increase concentration and collision frequency, and accelerate a reaction.

Round-bottom flasks are types of flasks having spherical bottoms used as laboratory glassware, mostly for chemical or biochemical work. They are typically made of glass for chemical inertness; and in modern days, they are usually made of heat-resistant borosilicate glass. There is at least one tubular section known as the neck with an opening at the tip. Two or three-necked flasks are common as well. Round bottom flasks come in many sizes, from 5 mL to 20 L, with the sizes usually inscribed on the glass. In pilot plants even larger flasks are encountered.

The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.

A solvent is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. The quantity of solute that can dissolve in a specific volume of solvent varies with temperature. Common uses for organic solvents are in dry cleaning, as paint thinners, as nail polish removers and glue solvents, in spot removers, in detergents and in perfumes (ethanol). Water is a solvent for polar molecules and the most common solvent used by living things; all the ions and proteins in a cell are dissolved in water within a cell. Solvents find various applications in chemical, pharmaceutical, oil, and gas industries, including in chemical syntheses and purification processes.

Increase in temperature can speed up the desired reaction, but also speed up the decomposition of reagents and starting materials. However, pressure can speed up the desired reaction and only impacts decomposition when it involves the release of a gas or a reaction with a gas in the vessel. When the desired reaction is accelerated, competing reactions are minimized. Pressure generally enables faster reactions with cleaner reaction profiles.

Chemical decomposition, analysis or breakdown is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds. Chemical decomposition is usually regarded and defined as the exact opposite of chemical synthesis. In short, the chemical reaction in which two or more products are formed from a single reactant is called a decomposition reaction.

Reagent substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs

A reagent is a substance or compound added to a system to cause a chemical reaction, or added to test if a reaction occurs. The terms reactant and reagent are often used interchangeably—however, a reactant is more specifically a substance consumed in the course of a chemical reaction. Solvents, though involved in the reaction, are usually not called reactants. Similarly, catalysts are not consumed by the reaction, so they are not reactants. In biochemistry, especially in connection with enzyme-catalyzed reactions, the reactants are commonly called substrates.

The above benefits from a pressure reactor has been shown in microwave chemistry. E.g., if a Suzuki Coupling takes 8 hours at 80°C, it only takes 8 minutes at 140°C in a microwave synthesizer. The microwave effect is a controversial topic. Later experiments show some of these early reports to be artifacts and rate enhancement is strictly due to thermal effects.^[1]^[2]^[3]

Microwave chemistry is the science of applying microwave radiation to chemical reactions. Microwaves act as high frequency electric fields and will generally heat any material containing mobile electric charges, such as polar molecules in a solvent or conducting ions in a solid. Polar solvents are heated as their component molecules are forced to rotate with the field and lose energy in collisions. Semiconducting and conducting samples heat when ions or electrons within them form an electric current and energy is lost due to the electrical resistance of the material. Microwave heating in the laboratory began to gain wide acceptance following papers in 1986, although the use of microwave heating in chemical modification can be traced back to the 1950s. Although occasionally known by such acronyms as MAOS, MEC or MORE synthesis, these acronyms have had little acceptance outside a small number of groups.

The Suzuki reaction is an organic reaction, classified as a coupling reaction, where the coupling partners are a boronic acid and an organohalide catalyzed by a palladium(0) complex. It was first published in 1979 by Akira Suzuki and he shared the 2010 Nobel Prize in Chemistry with Richard F. Heck and Ei-ichi Negishi for their effort for discovery and development of palladium-catalyzed cross couplings in organic synthesis. In many publications this reaction also goes by the name Suzuki–Miyaura reaction and is also referred to as the Suzuki coupling. It is widely used to synthesize poly-olefins, styrenes, and substituted biphenyls. Several reviews have been published describing advancements and the development of the Suzuki Reaction. The general scheme for the Suzuki reaction is shown below where a carbon-carbon single bond is formed by coupling an organoboron species (R₁-BY₂) with a halide (R₂-X) using a palladium catalyst and a base.

If a pressure reactor is engineered properly, it can meet 4 out of 12 green chemistry principles

Green chemistry, also called sustainable chemistry, is an area of chemistry and chemical engineering focused on the designing of products and processes that minimize the use and generation of hazardous substances. While environmental chemistry focuses on the effects of polluting chemicals on nature, green chemistry focuses on the environmental impact of chemistry, including technological approaches to preventing pollution and reducing consumption of nonrenewable resources.

1, less solvent and cleaner reaction profile result in less waste
5, less solvent is needed
6, short reaction time can save up to 92 percent electricity and 200 gallons of cooling water per refluxed reaction ^{[ citation needed ]}
12, closed vessel can prevent releasing toxic gas and explosions.

Types of Pressure Reactors

Standard glass pressure reactor

Glass Pressure reactors are typically used when an operator needs to observe how a reaction takes place. Although the pressure ratings on these systems are lower than most metal pressure reactors, they are still an efficient set up for reaching responsible pressure limits. The ratings on glass vessels are directly related to the diameter of the vessel. The larger the diameter, the lower the allowable pressure. Integrated bottom valves can also impact the pressure ratings. A bottom valve on a glass vessel typically relates to a lower allowable working pressure. These are all variables determined by the process and parameters of each individual reaction. Glass pressure vessels can also be used in inert applications. These vessels are used in reactions included but are not limited to Hydrogenations, Polymerizations, Synthesis, Catalytic, petrochemical, crystallization, and so on.

One of the drawbacks of a standard glass pressure reactor is the potential explosions due to hard-to-predict excessive internal pressure and lack of relief mechanism. However, with proper safety implementation provided by the manufacturer, the operator can perform most reactions in a safe manner.

Fisher-Porter tube

A Fisher-Porter tube or Fisher-Porter vessel is a glass pressure reactor used in the chemical laboratory. Manufactured by Andrews Glass Co. of Vineland NJ

Q-tube

There is a new pressure reactor, called Q-Tube.^[4] It features a simple and safe pressure release and reseal mechanism which can prevent a glass pressure reactor from explosions and retain the solvent.

Metal pressure reactor

Metal Pressure reactors are typically used for high pressure reactions. They have a much higher pressure rating than glass reactors. Although they have a higher pressure rating, they still have their own distinct flaws. One of which would be that metal vessels are more susceptible to corrosion. The material of construction (MOC) is particularly important during the design phase of a metal pressure reactor. The correct MOC can reduce or even eliminate the corrosion seen in the vessel but, depending on the material chosen, could increase the price of a system. Metal vessels are also much heavier and should be handled carefully when performing maintenance.

Metal high pressure reactors are used in reactions included but are not limited to Hydrogenation, Polymerization, Synthesis, Catalytic, Petrochemical and so on. They are also used to perform research such as Upstream, Biomass, Biopolymer, Zeolite, etc.

The drawbacks of a metal pressure reactor (bomb) are set-up, maintenance, and corrosiveness.

Microwave synthesizer

The drawbacks of a microwave synthesizer are solvent limitation

Related Research Articles

In chemistry, a hydride is the anion of hydrogen, H⁻, or, more commonly, it is a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties in it. In compounds that are regarded as hydrides, the hydrogen atom is bonded to a more electropositive element or groups. Compounds containing hydrogen bonded to metals or metalloid may also be referred to as hydrides. Common examples are ammonia (NH₃), methane (CH₄), ethane (C₂H₆) (or any other hydrocarbon), and Nickel hydride (NiH), used in NiMH rechargeable batteries.

Oil refinery or petroleum refinery is an industrial process plant where crude oil is transformed and refined into more useful products such as petroleum naphtha, gasoline, diesel fuel, asphalt base, heating oil, kerosene, liquefied petroleum gas, jet fuel and fuel oils. Petrochemicals feed stock like ethylene and propylene can also be produced directly by cracking crude oil without the need of using refined products of crude oil such as naphtha.

Tungsten(VI) fluoride, also known as tungsten hexafluoride, is an inorganic compound with the formula WF₆. It is a toxic, corrosive, colorless gas, with a density of about 13 g/L (roughly 11 times heavier than air.) It is one of the densest known gases under standard conditions. WF₆ is commonly used by the semiconductor industry to form tungsten films, through the process of chemical vapor deposition. This layer serves as a low-resistivity metallic "interconnect". It is one of seventeen known binary hexafluorides.

A chemical reactor is an enclosed volume in which a chemical reaction takes place. In chemical engineering, it is generally understood to be a process vessel used to carry out a chemical reaction, which is one of the classic unit operations in chemical process analysis. The design of a chemical reactor deals with multiple aspects of chemical engineering. Chemical engineers design reactors to maximize net present value for the given reaction. Designers ensure that the reaction proceeds with the highest efficiency towards the desired output product, producing the highest yield of product while requiring the least amount of money to purchase and operate. Normal operating expenses include energy input, energy removal, raw material costs, labor, etc. Energy changes can come in the form of heating or cooling, pumping to increase pressure, frictional pressure loss or agitation.

A steam explosion is an explosion caused by violent boiling or flashing of water into steam, occurring when water is either superheated, rapidly heated by fine hot debris produced within it, or heated by the interaction of molten metals. Pressure vessels, such as pressurized water (nuclear) reactors, that operate above atmospheric pressure can also provide the conditions for a steam explosion. The water changes from a liquid to a gas with extreme speed, increasing dramatically in volume. A steam explosion sprays steam and boiling-hot water and the hot medium that heated it in all directions, creating a danger of scalding and burning.

The Fischer–Tropsch process is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at temperatures of 150–300 °C (302–572 °F) and pressures of one to several tens of atmospheres. The process was first developed by Franz Fischer and Hans Tropsch at the Kaiser-Wilhelm-Institut für Kohlenforschung in Mülheim an der Ruhr, Germany, in 1925.

Dimethylformamide is an organic compound with the formula (CH₃)₂NC(O)H. Commonly abbreviated as DMF (although this initialism is sometimes used for dimethylfuran, or dimethyl fumarate), this colourless liquid is miscible with water and the majority of organic liquids. DMF is a common solvent for chemical reactions. Dimethylformamide is odorless whereas technical grade or degraded samples often have a fishy smell due to impurity of dimethylamine. Dimethylamine degradation impurities can be removed by sparging degraded samples with an inert gas such as argon or by sonicating the samples under reduced pressure. As its name indicates, it is a derivative of formamide, the amide of formic acid. DMF is a polar (hydrophilic) aprotic solvent with a high boiling point. It facilitates reactions that follow polar mechanisms, such as S_N2 reactions.

The water-gas shift reaction (WGSR) describes the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen (the mixture of carbon monoxide and hydrogen (not water) is known as water gas):

Catalytic reforming is a chemical process used to convert petroleum refinery naphthas distilled from crude oil into high-octane liquid products called reformates, which are premium blending stocks for high-octane gasoline. The process converts low-octane linear hydrocarbons (paraffins) into branched alkanes (isoparaffins) and cyclic naphthenes, which are then partially dehydrogenated to produce high-octane aromatic hydrocarbons. The dehydrogenation also produces significant amounts of byproduct hydrogen gas, which is fed into other refinery processes such as hydrocracking. A side reaction is hydrogenolysis, which produces light hydrocarbons of lower value, such as methane, ethane, propane and butanes.

Hydrodesulfurization (HDS) is a catalytic chemical process widely used to remove sulfur (S) from natural gas and from refined petroleum products, such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils. The purpose of removing the sulfur, and creating products such as ultra-low-sulfur diesel, is to reduce the sulfur dioxide emissions that result from using those fuels in automotive vehicles, aircraft, railroad locomotives, ships, gas or oil burning power plants, residential and industrial furnaces, and other forms of fuel combustion.

In flow chemistry, a chemical reaction is run in a continuously flowing stream rather than in batch production. In other words, pumps move fluid into a tube, and where tubes join one another, the fluids contact one another. If these fluids are reactive, a reaction takes place. Flow chemistry is a well-established technique for use at a large scale when manufacturing large quantities of a given material. However, the term has only been coined recently for its application on a laboratory scale. Often, microreactors are used.

A drying tube or guard tube is a tube-like piece of apparatus used to house a disposable solid desiccant, wherein at one end the tube-like structure terminates in a ground glass joint for use in connecting the drying tube to a reaction vessel, for the purpose of keeping the vessel free of moisture.

Tetralin (1,2,3,4-tetrahydronaphthalene) is a hydrocarbon having the chemical formula C₁₀H₁₂. This molecule is similar to the naphthalene chemical structure except that one ring is saturated.

Cannula transfer or cannulation is a subset of air-free techniques used with a Schlenk line, in transferring liquid or solution samples between reaction vessels via cannulae, avoiding atmospheric contamination. While the syringes are not the same as cannulae, the techniques remain relevant.

FLiBe is a molten salt made from a mixture of lithium fluoride (LiF) and beryllium fluoride (BeF₂). It is both a nuclear reactor coolant and solvent for fertile or fissile material. It served both purposes in the Molten-Salt Reactor Experiment (MSRE).

A nuclear reactor coolant is a coolant in a nuclear reactor used to remove heat from the nuclear reactor core and transfer it to electrical generators and the environment. Frequently, a chain of two coolant loops are used because the primary coolant loop takes on short-term radioactivity from the reactor.

Borrowing hydrogen catalysis, also called hydrogen autotransfer, is an important catalytic concept. "Borrowing hydrogen" can be seen as an example of Green chemistry. It is based on the intermediate oxidation of an alcohol substrate to the corresponding aldehyde by the catalyst ; the intermediate aldehyde then reacts with e.g. a secondary amine in a condensation reaction to produce e.g. an imine, that is then reduced by the catalyst in the final step to yield e.g. a tertiary amine. The method is highly atom economic, because is circumvents the activation of the alcohol.

Renewable hydrocarbon fuels via decarboxylation/decarbonylation. With an increasing demand for renewable fuels, extensive research is under way on the utilization of biomass as feedstock for the production of liquid transportation fuels. Using biomass is an attractive alternative, since biomass removes carbon dioxide from the atmosphere as it grows through photosynthesis, thus closing the carbon cycle and making biofuels carbon neutral when certain conditions are met. First generation biofuels such as biodiesel have important drawbacks, as they are normally derived from edible feedstock and are not fully compatible with standard diesel engines. Given that the majority of the problems associated with these fuels stem from their high oxygen content, methods to deoxygenate biomass-derived oils are currently being pursued. The ultimate goal is to convert inedible biomass feeds into hydrocarbon biofuels fully compatible with existing infrastructure. These so-called second generation biofuels can be used as drop-in substitutes for traditional petroleum-derived hydrocarbon fuels.

References

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[1] Biotage Synthesis and Purification Catalog 2008

[2] Nonthermal Microwave Effects Revisited, On the Importance of InternalTemperature Monitoring and Agitation in Microwave Chemistry M. A. Herrero, J. M. Kremsner, C. O. Kappe J. Org. Chem. 2008, 73, 36-47. Archived 2008-10-20 at the Wayback Machine .

[3] Microwave Chemistry in Silicon Carbide Reaction Vials: Separating Thermal from Nonthermal Effects. D. Obermayer, B. Gutmann, C. O. Kappe Angew. Chem. Int. Ed. 2009, 48, 8321-8342. Archived 2008-10-20 at the Wayback Machine .

[4] ufacturer's website