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Please see the Volume Licensing Service Center for more information. Cumene processes based on zeolites are environmentally friendly, offering high productivity and selectivity. The most important are listed in Table 3. The catalyst performance determines the type and operational parameters of the reactor and, accordingly the flowsheet configuration. Propylene is dissolved in a large excess of benzene more than 5 : 1 molar ratio at sufficiently high pressure that ensures only one liquid phase at the reaction temperature, usually between and C.
The alkylation reactor is a column filled with fixed-bed catalyst, designed to ensure complete conversion of propylene.
The reactor effluent is sent to the separation section, in this case a series of four distillation columns: propane LPG recovery, recycled benzene, cumene product and separation of polyisopropylbenzenes. The flowsheet involves two recycles: nonreacted benzene to alkylation and polyalkylbenzenes to transalkylation. The minimization of recycle flows and of energy consumption in distillation are the key objectives of the design. These can be achieved by employing a highly active and selective catalyst, as well as by implementing advanced heat integration.
Beside cumene, variable amounts of LPG can be obtained as subproducts. Energy is also exported as LP steam, although it is consumed as well as other utilities fuel, cooling water, electricity. Critical pressures of propane and propylene are above 40 bar, but in practice 20 to 30 bar are sufficient to ensure a high concentration of propylene in the coreactant benzene.
From the separation viewpoint one may note large differences in the boiling points of components and no azeotrope formation. In consequence, the design of the separation train should not raise particular problems. Since the liquid mixtures behave almost ideally a deeper thermodynamic analysis is not necessary.
The use of vacuum distillation is expected because of the high boiling points of the polyalkylated benzenes. Cumene is oxidized in air which removes the tertiary benzylic hydrogen from cumene and hence forms a cumene radical: This cumene radical then bonds with an oxygen molecule to give cumene hydroperoxide radical, which in turn forms cumene hydroperoxide C6H5C CH3 2-O-O- H by abstracting benzylic hydrogen from another cumene molecule.
By the isomerization some n - propylbenzene appears, which is highly undesirable as an impurity. The presence of stronger acid sites favors the formation of propylene oligomers and other hydrocarbon species. Therefore, high selectivity of the catalyst is as important as high activity. It is remarkable that the polyalkylates byproducts can be reconverted to cumene by reaction with benzene. The second type is A homogeneous AlCl3 and hydrogen chloride catalyst system developed by Monsanto.
The solid phosphoric acid catalyst provides an essentially complete conversion of propylene on a one-pass basis. Fresh benzene is combined with recycle benzene and fed to the alkylation reactor 1. The benzene feed flows in series through the beds, while fresh propylene feed is distributed equally between the beds. This reaction is highly exothermic, and heat is removed by recycling a portion of reactor effluent to the reactor inlet and injecting cooled reactor effluent between the beds.
In the fractionation section, propane that accompanies the propylene feedstock is recovered as LPG product from the overhead of the depropanizer column 2 , unreacted benzene is recovered from the overhead of the benzene column 4 and cumene product is taken as overhead from the cumene column 5.
Di- isopropylbenzene DIPB is recovered in the overhead of the DIPB column 6 and recycled to the transalkylation reactor 3 where it is transalkylated with benzene over a second zeolite catalyst to produce additional cumene.
A small quantity of heavy byproduct is recovered from the bottom of the DIPB column 6 and is typically blended to fuel oil. The cumene product has a high purity The zeolite catalyst is noncorrosive and operates at mild conditions; thus, carbon-steel construction is possible.
Catalyst cycle lengths are two years and longer. The catalyst is fully regenerable for an ultimate catalyst life of six years and longer. Existing plants that use spa or ALCL3 catalyst can be revamped to gain the advantages of Q-Max cumene technology while increasing plant capacity. Separately, recycled polyisopropylbenzene PIPB is premixed with benzene and fed to the transalkylation reactor 2 where PIPB reacts to form additional cumene.
The transalkylation and alkylation efuents are fed to the distillation section. The distillation section consists of as many as four columns in series. The depropanizer 3 recovers propane overhead as LPG. The benzene column 4 recovers excess benzene for recycle to the reactors. The cumene column 5 recovers cumene product overhead. The new catalyst is environmentally inert, does not produce byproduct oligomers or coke and can operate at the lowest benzene to propylene ratios of any available technology with proven commercial cycle lengths of over seven years.
Expected catalyst life is well over ve years. At present, there are 12 plants operating with a combined capacity exceeding 5. In addition, four grassroots plants and an ALCL3 revamp are in the design phase. The effluent from the alkylation zone is combined with recycle polyisopropyl benzene and fed to the transalkylation zone, where polyisopropyl benzenes are transalkylated to cumene.
The strongly acidic catalyst is separated from the organic phase by washing the reactor effluent with water and caustic. The distillation system is designed to recover a high purity cumene product. The unconverted benzene and polyisopropyl benzene are separated and recycled to the reaction system.
Propane in the propylene feed is recovered as liquid petroleum gas. The overall yields of cumene for this process can be high as 99 Wt. But these processes have been used more extensively for the production of ethylbenzene than for the production of cumene. The CD cumene process uses a specially formulated zeolite alkylation catalyst packaged in a proprietary CD structure and another Specially formulated zeolite transalkylation catalyst in loose form.
Alkylation takes place isothermally and at low temprature. Cd also promotes the continuous removal of reaction products from reaction zones. These factors limit byproduct impurities and enhance product purity and yield. Low operating temperatures and pressures also decrease capital investment, improve operational safety and minimize fugitive emissions.
Overhead vapor from the CD column 1 is condensed and returned as reux after removing propane and lights p. The CD column bottom section strips benzene from cumene and heavies. The distillation train separates cumene product and recovers polyisopropylbenzenes PIPB and some heavy aromatics h from the net bottoms.
PIPB reacts with benzene in the transalkylator 2 for maximum cumene yield. Operating conditions are mild and noncorrosive; standard carbon steel can be used for all equipment. Figure 3. This modern process features higher product yields, with a much lower capital investment, than the environmentally outdated acid-based processes.
The exceptional quality of the cumene product from the CDCumene process easily surpasses current requirements of phenol producers, and may well define tomorrows more stringent quality standards. The unique catalytic distillation column combines reaction and fractionation in a single unit operation. The alkylation reaction takes place isothermally and at low temperature.
Reaction products are continuously removed from the reaction zones by distillation. These factors limit the formation of by-product impurities, enhance product purity and yields, and result in expected reactor run lengths in excess of two years. Low operating temperatures result in lower equipment design and operating pressures, which help to decrease capital investment, improve safety of operations, and minimize fugitive emissions.
All waste heat, including the heat of reaction, is recovered for improved energy efficiency. The CDCumene technology can process chemical or refinery grade propylene. Cumene product is at least The Q-Max process represents a substantial improvement over older cumene technologies and is characterized by its exceptionally high yield, superior product quality, low investment and operating costs, reduction in solid waste, and corrosion- free environment. Cumene is produced commercially through the alkylation of benzene with propylene over an acid catalyst.
Over the years, many different catalysts have been proposed for this alkylation reaction, including boron trifluoride, hydrogen fluoride, aluminum chloride, and phosphoric acid. In the s, UOP introduced the UOP catalytic condensation process, which used a solid phosphoric acid SPA catalyst to oligomerize light olefin by-products from petroleum thermal cracking into heavier paraffins that could be blended into gasoline.
During World War II, this process was adapted to produce cumene from benzene and propylene to make a high-octane blending component for military aviation gasoline. Today, cumene is no longer used as a fuel, but it has grown in importance as a feedstock for the production of phenol.
Cumene yield is limited to about 95 percent, because of the oligomerization of propylene and the formation of heavy alkylate by-products 2. The catalyst is not regenerable and must be disposed of at the end of each catalyst cycle. In recent years, producers have been under increasing pressure to improve cumene product quality so that the quality of the phenol produced downstream as well as acetone and alpha-methylstyrene, which are coproduced with phenol could be improved.
Twenty-five years ago, most phenol was used to produce phenolic resins, and acetone was used primarily as a solvent. Today, both phenol and acetone are used increasingly in the production of polymers such as polycarbonates and nylon. Over the years, improvements to the SPA producers still sought an improved cumene process that would produce a better- quality product at higher yield.
Because zeolites are known to selectively perform many acid-catalyzed reactions, UOP began searching for a new cumene catalyst that would overcome the limitations of SPA. UOPs objective was to develop a regenerable catalyst that would increase the yield of cumene and lower the cost of production.
More than different catalyst materials were screened, including mordenites, MFIs, Y-zeolites, amorphous silica- aluminas, and betazeolite.
The result of this work is the Q- Max process and the QZ- catalyst system. The alkylation reactor is typically divided into four catalyst beds contained in a single reactor shell.
The fresh benzene is routed through the upper midsection of the depropanizer column to remove excess water and then sent to the alkylation reactor via a sidedraw. The recycle benzene to both the alkylation and transalkylation reactors comes from the overhead of the benzene column. A mixture of fresh and recycle benzene is charged downflow through the alkylation reactor.
The fresh propylene feed is split between the four catalyst beds. An excess of benzene is used to avoid polyalkylation and to help minimize olefin oligomerization. Because the reaction is exothermic, the temperature rise in the reactor is controlled by recycling a portion of the reactor effluent to the reactor inlet, which acts as a heat sink.
In addition, the inlet temperature of each downstream bed is reduced to the same temperature as that of the first bed inlet by injecting a portion of cooled reactor effluent between the beds. Effluent from the alkylation reactor is sent to the depropanizer column, which removes any propane and water that may have entered with the propylene feed. The bottoms from the depropanizer column are sent to the benzene column, where excess benzene is collected overhead and recycled.
Benzene column bottoms are sent to the cumene column, where the cumene product is recovered overhead. The DIPB stream leaves the column by way of a sidecut and is recycled to the transalkylation reactor. The DIPB column bottoms consist of heavy aromatic by-products, which are normally blended into fuel oil. Steam or hot oil provides the heat for the product fractionation section.
A portion of the recycle benzene from the top of the benzene column is combined with the recycle DIPB from the sidecut of the DIPB column and sent to the transalkylation reactor. In the transalkylation reactor, DIPB and benzene are converted to additional cumene.
The effluent from the transalkylation reactor is then sent to the benzene column. The QZ catalyst utilized in both the alkylation and transalkylation reactors is regenerable. At the end of each cycle, the catalyst is typically regenerated ex-situ via a simple carbon burn by a certified regeneration contractor.
However, the unit can also be designed for in-situ catalyst regeneration. Mild operating conditions and a corrosion-free process environment permit the use of carbon-steel construction and conventional process equipment. The basic alkylation chemistry and reaction mechanism are shown in Figure 3. The addition to the olefin double bond is at the middle carbon of propylene, in accordance with Markovnikovs rule. The addition of the isopropyl group to the benzene ring weakly activates the ring toward further alkylation, producing di-isopropyl-benzene DIPB and heavier alkylate by-products.
The QZ catalyst functions as strong acid. In the QZ catalyst, the active surface sites of the silica-alumina structure act to donate the proton to the adsorbed olefin.
Because the QZ catalyst is a strong acid, it can be used at a very low temperature. Low reaction temperature reduces the rate of competing olefin oligomerization reactions, resulting in higher selectivity to cumene and lower production of heavy by-products.
After recovery of the cumene product by fractionation, the DIPB is reacted with recycle benzene at optimal conditions for transalkylation to produce additional cumene.
With the alkylation and transalkylation reactors working together to take full advantage of the QZ catalyst, the overall yield of cumene is increased to Oligomerization of olefins.
The model for acid-catalyzed alkylation is diffusion of the olefin to an active site saturated with benzene followed by adsorption and reaction. One possible side reaction is the combination of the propyl carbonium ion with propylene to form a C6 olefin or even further reaction to form C9, C12, or heavier olefins.
Alkylation of benzene with heavy olefins. Once heavy olefins have been formed through oligomerization, they may react with benzene to form hexylbenzene and heavier alkylated benzene by-products. The addition of an isopropyl group to the benzene ring to produce cumene weakly activates the ring toward further substitution, primarily at the meta and para positions, to make DIPB and heavier alkylates.
Hydride-transfer reactions. Transfer of a hydrogen to an olefin by the tertiary carbon on cumene can form a cumyl carbonium ion that may react with a second benzene molecule to form diphenylpropane 5. In the Q-Max process, the reaction mechanism of the QZ catalyst and the operating conditions of the unit work together to minimize the impact of these side reactions.
The result is an exceptionally high yield of cumene product. By reacting benzene and propylene, cumene can be produced. Actually, this reaction can be occurred in liquid and gas phases, but high conversion are obtained at gas phase reactions, catalyst like solid phosphoric acid are replaced by zeolites and the catalytic conversion reaction are held in shell and tube reactors rather than packed fixed bed reactors.
Cumene process reaction is exothermic in nature so a complex shell and tube reactor designs are not sufficient for energy conversion, tremendous research work is involved in design a rector of Cumene production from benzene and propane. Storage and pumping sectio 2. Preheating and vaporization section 3. Reactor section 4. Separation and purification section 3. Benzene excess reactant is mixed in the circulation tank where propane is added to the stream line of the feed inlet to the cascade of heat exchangers.
Finally after the heat exchanger a fired heater is used to vaporize and raise the temperature of the mixture to the reaction condition temperature.
The process followed for the production of cumene is the catalytic alkylation of benzene with propylene and now a days zeolite based catalysts are used in place of the normal acid based catalysts due to added advantages.
Cumene production process has been greatly studied and the reaction mechanism and the reaction kinetics have been specified by many researchers. Both experimental as well as computer based simulation and optimization studies have been carried out by various researchers. The UOP process converts a mixture of benzene and propylene to high quality cumene using a regenerable zeolite catalyst.
The UOP process is characterized by a exceptionally high yield, better product quality, less solid waste, decrease in investment and operating costs and a corrosion free environment. The QZ zeolite based catalyst utilized for the UOP process which operates with a low flow rate of benzene and hence investment and utility costs are reduced greatly. QZ is non-corrosive and regenerate-able.
Compared to other zeolite based cumene technologies, the UOP process provides the highest product quality and great stability. Impurities in the fee have less effect The alkylation reactor is divided into four catalytic beds present in a single reactor shell. The fresh benzene feed is passed through the upper-mid section of the depropanizer column to remove excess water and then sent to the alkylation reactor.
The recycle benzene to the alkylation and transalkylation reactors is drawn from the benzene column. This mixture of fresh and recycle benzene is charged through the alkylation reactor. The fresh propylene feed is split between the catalyst beds and is fully consumed in each bed. An excess of benzene helps in avoiding formation of poly alkylation and reduce the effect of olefin oligomerization.
As the chemical reaction occurs at exothermic condition, the temperature increase during the alkylation reaction is controlled by the reactor effluent. The temperature of inlet stream from the catalyst beds is further maintained to the designed temperature by the circuit reactor effluent passing tubes which are cooled by the side stream heat exchangers between the beds. The bottoms stream of the depropanizer column is fed to the benzene distillation column where excess benzene is collected at top of the column and recycled to the process fed stream.
The benzene distillation column bottom stream fed to the cumene rectifying column where cumene is recovered overhead. The DIPB stream is recycled to increase the conversion to the transalkylation reactor. The DIPB column bottom products contains of heavy aromatic by-products, which are blended into fuel oil.
High pressure steam is used as heating medium to the fractionation columns. The recycle DIPB from the overhead of the DIPB column combines with a portion of the recycle benzene and is charged downflow through the transalkylation reactor. In the transalkylation reactor, DIPB and benzene are converted to more cumene. The new QZ catalyst is utilized in the alkylation reactor while the original QZ catalyst used for the transalkylation reactor.
Catalyst life time is about 24 years. The DIPB is separated from the cumene and is reacted with recycle benzene at optimal conditions for transalkylation to produce additional cumene. The major reactions taking place are alkylation and trans-alkylation.
Side reactions which take place are isomerisation and dis-proportionation. The reaction mechanism and kinetics may vary depending on the catalyst used. The reaction can occur in presence or absence of carbonium ion intermidate. Mass flows can be identified which might have been unknown, or difficult to measure without this technique by accounting for material entering and leaving a system.
The exact conservation law used in the analysis of the system depends on the context of the problem but all revolve around mass conservation, i. So, in engineering and environmental analyses, mass balances are used widely. Mass balance theory can be used to design chemical reactors, analyses alternative processes to produce chemicals as well as in pollution dispersion models and other models of physical systems.
Closely related and complementary analysis techniques include the population balance, energy balance and the somewhat more complex entropy balance. These techniques are required for thorough design and analysis of systems such as the refrigeration cycle. Therefore, the general form quoted for a mass balance is The mass that enters a system must, by conservation of mass, either leave the system or accumulate within the system.
In the absence of a chemical reaction the amount of any chemical species flowing in and out will be the same. This gives rise to an equation for each species in the system. However if this is not the case then the mass balance equation must be amended to allow for the generation or depletion consumption of each chemical species. Some use one term in this equation to account for chemical reactions, which will be negative for depletion and positive for generation.
However, the conventional form of this equation is written to account for both a positive generation term i. Although overall one term will account for the total balance on the system, if this balance equation is to be applied to an individual species and then the entire process, both terms are necessary.
The equation is given below. Note that it simplifies to the earlier equation in the case that the generation term is zero. The molecular weight for the cumene was However, it is very expensive to operate the reactor at elevated temperature. Besides, it is very dangerous to the worker too. The loss of the product In the reactor is normally due to the fouling of the product on the wall of the reactor or in the pipeline.
Besides, it might due to leaking. For example, the flange which connect the inlet pipeline to the reactor is not screwed tightly. Thus, some of the product leak through the flangle. It is used for quenching purpose in the reactor. It does not take part in the chemical reaction. Also It is inevitably associated with the propylene as an impurity as their molecular weight is very close. We assume propylene to propane ratio as Being an inert we are neglecting propane balance in the material balance to avoid complexity.
Assuming almost all the propane is removed in depropanising column and sent to reactor for quenching. Hence material balance for depropanasing column is not considered. The removed benzene is recycled back to the benzene feed tank to minimize the waste of the raw material. This will avoid the complexity of multi component distillation in Cumene column. The energy coming into a unit operation can be balanced with the energy coming out and the energy stored.
For example mechanical energy to heat energy, but overall the quantities must balance. Besides that, energy also takes many forms, such as heat, kinetic energy, chemical energy, potential energy but because of interconversions it is not always easy to isolate separate constituents of energy balances. However, under some circumstances certain aspects predominate. We are seldom concerned with internal energies.
Therefore practical applications of energy balances tend to focus on particular dominant aspects and so a heat balance, for example, can be a useful description of important cost and quality aspects of process situation. When unfamiliar with the relative magnitudes of the various forms of energy entering into a particular processing situation, it is wise to put them all down.
Then after some preliminary calculations, the important ones emerge and other minor ones can be lumped together or even ignored without introducing substantial errors. With experience, the obviously minor ones can perhaps be left out completely though this always raises the possibility of error.
Energy balances can be calculated on the basis of external energy used per kilogram of product, or raw material processed, or on dry solids or some key component.
The energy consumed in food production includes direct energy which is fuel and electricity used on the farm, and in transport and in factories, and in storage, selling, etc. Food itself is a major energy source, and energy balances can be determined for animal or human feeding; food energy input can be balanced against outputs in heat and mechanical energy and chemical synthesis.
However, kilocalories are still used by some nutritionists and British thermal units Btu in some heat-balance work. Heat Balances The most common important energy form is heat energy and the conservation of this can be illustrated by considering operations such as heating and drying.
In these, enthalpy total heat is conserved and as with the mass balances so enthalpy balances can be written round the various items of equipment. Enthalpy H is always referred to some reference level or datum, so that the quantities are relative to this datum. Working out energy balances is then just a matter of considering the various quantities of materials involved, their specific heats, and their changes in temperature or state as quite frequently latent heats arising from phase changes are encountered.
Latent heat is the heat required to change, at constant temperature, the physical state of materials from solid to liquid, liquid to gas, or solid to gas. Sensible heat is that heat which when added or subtracted from materials changes their temperature and thus can be sensed. Having determined those factors that are significant in the overall energy balance, the simplified heat balance can then be used with confidence in industrial energy studies.
Such calculations can be quite simple and straightforward but they give a quantitative feeling for the situation and can be of great use in design of equipment and process. Propylene, propane, benzene enter at 25 C and benzene enters at 80C.
Propane i. Assuming very small propane content to be a part of Benzene stream. Stream No. Impurities in the cumene product are governed primarily by trace contaminants in the feeds. Cumene can be operated at very low temperature due to the high activity of the QZ- catalyst. This will dramatically reduces the rate of competing olefin oligomerization reactions and decreases the formation of heavy by-products.
As a result, cumene product impurities are primarily from impurities in the feedstocks in the Q-Max process. Cumene is formed by the alkylation of toluene with propylene. Table 1. Ethylbenzene is primarily formed from ethylene impurities in the propylene feed. The toluene may already be present as an impurity in the benzene feed, or it may be formed in the alkylation reactor from methanol and benzene.
However, as with cumene, ethylbenzene can also be formed from ethanol. To protect against hydrate freezing, small quantities of methanol and ethanol are sometimes added to the pipeline. Although the Q-Max catalyst is tolerant of these alcohols, removing them from the feed by a water wash may be desirable.
This is done to achieve the lowest possible levels of ethylbenzene or cumene in the cumene product n Butylbenzene. However, oligomerization is reduced as a result of the very low reaction temperature of the Q-Max process. This will caused minimal overall butylbenzene formation. The n-propylbenzene NPB is produced from trace levels of cyclopropane in the propylene feed.
The chemical behavior of cyclopropane is similar to that of an olefin. It reacts with benzene to form either cumene or NPB. As the reaction temperature is lowered, the tendency to form NPB rather than cumene decreases. However, the catalyst deactivation rate increases with lower reaction temperature Fig.
A Q-Max unit can be operated for extended cycle lengths and still maintain an acceptable level of NPB in the cumene product because of the exceptional stability of the QZ catalyst system.
For example, with a typical FCC-grade propylene feed containing normal amounts of cyclopropane, the Q-Max process can produce a cumene product containing less than wt ppm NPB and maintaining an acceptable catalyst cycle length. All the listed compounds are known to neutralize the acid sites of zeolites.
Good feedstock treating practice or proven guard-bed technology easily handles these potential poisons. To neutralize some of the stronger zeolite acid sites first, water in an alkylation environment can act as a Brnsted base. Unfortunately, water does not have a detrimental effect at the typical feedstock moisture levels and normal alkylation and transalkylation conditions as a result of the inherently high activity of the Q-Max catalyst.
Sulfur does not affect Q-Max catalyst stability or activity at the levels normally present in the propylene and benzene feeds processed for cumene production. The Q-Max catalyst can process feedstocks up to the normal water saturation conditions, typically to ppm, without any loss of catalyst stability or activity.
Within the Q-Max unit, the majority of sulfur compounds associated with propylene mercaptans and those associated with benzene thiophenes are converted to products outside the boiling range of cumene. Thus, trace sulfur in the cumene product, for example, might be a concern in the downstream production of certain monomers e.
Sulfur at the levels normally present in propylene and benzene feeds considered for cumene production will normally result in cumene product sulfur content that is within specifications for example, 1 wt ppm. Chemical-grade, FCCgrade, and polymer-grade propylene feedstocks can all be used to make high-quality cumene product.
Successful operation with a wide variety of propylene feedstocks from different sources has demonstrated the flexibility of the Q-Max process. Figure 5. The remaining 0. The cumene product quality summarized in Table 1. The specific contaminants present in the feedstocks strongly influenced the quality of the cumene product from any specific Q-Max unit, Propane entering the unit with the propylene feedstock is unreactive in the process.
It is then is separated in the fractionation section as a propane product. The distillation requirements involve the separation of propane for LPG use, the recycle of excess benzene to polypropyl benzene for transalkylation to cumene and the production of purified cumene product. The selectivity to cumene is generally between 70 and 90 Wt. The remaining components are primarily polypropyl benzenes, which are transalkylated to cumene in a separate reaction zone. This give an overall yield to cumene of about 99 Wt.
The basic principle is to use the heat of reaction directly to supply heat for fractionation. This concept has been applied commercially for the production of MTBE but has not yet been applied commercially to cumene. Relative high selectivity to hexyl benzene 2. Significant yield of DIPB 3. Unloading of spent catalyst from reactor difficult 4.
Lower activity 5. Catalyst non-regenerability 5. Environmental hazard 2. Washing step for catalyst removal 3. The process followed for the production of cumene is the catalytic alkylation of benzene with propylene. Recently, zeolite based catalysts are used to replace the normal acid based catalysts due to added advantages.
Many researchers have greatly studied and specified on the cumene production process and the reaction mechanism and the reaction kinetics. They have carried out both experimental as well as computer based simulation and optimization studies. With the Q-MAX TM process, mixture of benzene and propylene is converted to high quality cumene using a regenerable zeolite catalyst. The Q-MAX TM process is characterized by an exceptionally high yield, better product quality, less solid waste, decrease in investment and operating costs and a corrosion free environment.
This is because the QZ zeolite based catalyst utilized for the UOP process operates with a low flow rate of benzene. Because of that, the investment and utility costs are reduced greatly.
Impurities in the fee have less effect. For the production of ethylbenzene, cumene, and detergent alkylate, the most important monoolefins are ethylene, propylene, and olefins with carbons, respectively. This section focuses primarily on these alkylation technologies. The rearrangement of carbonium ions that readily occurs according to the thermodynamic stability of cations sometimes limits synthetic utility of aromatic alkylation.
For example, the alkylation of benzene with n-propyl bromide gives mostly isopropylbenzene cumene C9H12 and much less n-propylbenzene. However, the selectivity to n-propylbenzene versus isopropylbenzene changes depending on alkylating reagents, conditions, and catalysts; eg, the alkylation of benzene with n-propyl chloride at room temperature gives mostly n-propylbenzene.
Today, the alkylation of aromatics is dominated by liquid - phase processes based on zeolites. The term zeolitic refers to molecular sieves whose framework consists essentially of silica and alumina tetrahedra. The complexity of tetrahedral groups may be linked in polynuclear structures. These catalysts are characterized by large pore opening necessary for achieving high selectivity.
Since industrial catalysts are employed as pellets, the mass - and heat transfer effects can play an important role. The use of an efficient catalyst is the decisive element in designing a competitive process. Beta-zeolite is quickly becoming the catalyst of choice for commercial production of ethylbenzene and cumene.
Mobil invented the basic beta-zeolite composition of matter in Since that time, catalysts utilizing beta-zeolite have undergone a series of evolutionary steps leading to the development of state- of-the-art catalysts such as the UOP EBZ and QZ for ethylbenzene and cumene alkylation service, respectively. At the same time that the structure of beta was being investigated, extensive research was being conducted to identify new uses for this zeolite. In fact, to make successful MediaTek Android Flash, your device should have rooted successfully.
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