33results about How to "Low selectivity" patented technology

The application relates to the technical field of nanomaterial preparation, and particularly discloses a carbon nanotube preparation method based on carbon source and plasma time sequence cooperation and a carbon nanotube. In the gas phase deposition process, carbon source gas is input in a pulse mode, and a pulse type plasma is synchronously applied, wherein the carbon source input pulse and the plasma output pulse are time-differently matched, the carbon source supply window and the plasma action window form a non-fully-synchronized time sequence coupling relationship, the carbon source activation, transportation, deposition and structure reconstruction process are controlled in the time dimension, and meanwhile, the carbon source gas is introduced from a position close to the plasma action area to maintain the pulse opening and closing characteristics. The method can improve the growth selectivity of the carbon nanotube, reduce the defect density, and is suitable for controllable preparation of single-wall carbon nanotubes. The single-wall carbon nanotube with a semiconductor content greater than or equal to 83% can be prepared with high selectivity, and the product has the advantages of few defects, high purity and high yield.

This invention relates to the field of catalyst technology, and in particular to a formaldehyde reforming hydrogen production catalyst, its preparation method, and its application. The formaldehyde reforming hydrogen production catalyst of this invention comprises a Cu-O-Zn solid solution and mordenite zeolite; the mass ratio of the Cu-O-Zn solid solution to the mordenite zeolite is 50-100:100. This formaldehyde reforming hydrogen production catalyst of this invention has advantages such as low reaction temperature, high formaldehyde conversion rate, high H2 selectivity, low CO selectivity, good stability, and long service life, and has broad market application prospects. This catalyst is not only suitable for formaldehyde systems, but can also be applied to other organic aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde, and benzaldehyde for reforming to produce hydrogen, demonstrating high versatility and practicality in the research field of catalytic reforming of organic aldehydes to produce clean energy hydrogen. The preparation method of this invention is simple, the raw materials are readily available, and it is easy to scale up for industrial production.

The invention relates to a preparation method of a catalyst for preparing 1-hexyl methyl acetate by addition of n-heptene and acetic acid, which comprises the following steps: impregnating a carrier sulfonic acid group strong acid resin into a heteropoly acid solution, stirring at 20-50 DEG C for 8-24 hours, and controlling the mass ratio of the sulfonic acid group strong acid resin to the heteropoly acid solution to be (10: 1)-(1: 3); and after stirring, filtering, and drying a solid obtained after filtering at 80-140 DEG C to obtain a finished product. The invention also provides a synthetic method for synthesizing 1-hexyl methyl acetate by using the catalyst. The supported solid acid catalyst can be recycled from reaction slurry through simple liquid-solid separation means such as filtration and centrifugation, and good product selectivity can be obtained.

The application discloses a kind of carolic acid and preparation method thereof, and specifically relates to the field of medical technology.The method comprises the following steps: stirring catalyst H2WO4 / C with hydrogen peroxide, then adding dichloro chrysanthemic acid ethyl ester; oil bath heating is carried out, reaction temperature is controlled, repeated reflux is carried out, and oxidation reaction is carried out; after the reaction, homogeneous transparent solution is filtered, extracted, and subjected to reduced pressure distillation to obtain carolic acid product.In the application, when catalyzing and oxidizing dichloro chrysanthemic acid ethyl ester, a high-activity H2WO4 / C heteropoly acid is used as a catalyst, the reaction scheme is optimized, the selectivity of the reaction is greatly improved, the number of cycles of the catalyst is increased, and after 20 cycles of the new catalyst, the catalyst activity does not decrease obviously.Furthermore, due to the great improvement of selectivity, the loss of product is reduced, and the yield is improved.

An isomerization catalyst characterized in that the catalyst comprises a composite carrier and platinum supported on the composite carrier, the composite carrier comprising 15.0-80.0 mass% of hydrogen type ZSM-22 zeolite, 10.0-70.0 mass% of hydrogen type ZSM-48 zeolite, 10.0-60.0 mass% of aluminum oxide based on the composite carrier. The catalyst is used for n-alkane isomerization reaction, has high activity and good stability, and can obtain higher isomer selectivity and yield, especially higher multi-branched alkane isomer selectivity and yield, and lower cracking product yield.

A method for one-step preparation of methylamine by hydrogenation amination of carbon dioxide, belonging to the field of catalysis. In a fixed-bed reactor, carbon dioxide, hydrogen, and ammonia are reacted. The catalyst comprises a microporous or mesoporous silica support, and the active component includes indium, zirconium, and at least one metal promoter selected from nickel, copper, palladium, rhodium, and platinum; the In 3d... 5 / 2 The binding energy is 444.0~444.7 eV, which is more than 0.2 eV lower than that of pure indium oxide; the single-pass conversion rate of carbon dioxide is not less than 50%, the total selectivity of methylamine is not less than 80%, and the selectivity of the byproduct carbon monoxide is not higher than 20%. This invention constructs a unique In-Zr-M active center, with In, Zr, and M uniformly co-distributed at the nanoscale. By adjusting the NH3 / CO2 ratio, the ratio of dimethylamine to trimethylamine can be controlled. The catalyst of this invention exhibits excellent performance and good stability, and has broad application prospects in the fields of carbon dioxide resource utilization and green synthesis of methylamine.

This application discloses a method, system, device, and medium for acquiring information from power equipment, belonging to the field of power electronics technology. The method includes: power equipment responding to a connection request from a pre-installed device by establishing a communication connection with the pre-installed device via an AP hotspot; receiving an inquiry command sent by the pre-installed device; obtaining the response information corresponding to the inquiry command; and sending the response information back to the pre-installed device. This application, by activating the AP hotspot of the WiFi module after the power equipment is powered on, allows the pre-installed device to establish a communication connection with the power equipment via the AP hotspot, obtain the corresponding response information based on the network relationship within the power equipment cluster, and provide feedback. This eliminates the need for manual scanning of QR codes or manual data entry for each power equipment, simplifying the power equipment information collection process, shortening the information acquisition time cycle, and improving the efficiency of power equipment information acquisition.

The invention discloses a heavy hydrocarbon catalytic cracking method and a heavy hydrocarbon catalytic cracking device, which are used for producing a carbon material raw material while increasing the yield of low-carbon olefin, improving the yield and selectivity of ethylene, propylene and butylene, reducing the yield of methane, reducing the content of ethanol in the product to the greatest extent and realizing low-cost conversion of ethanol into low-carbon olefin. The method can realize high-selectivity conversion of olefin and ethanol into low-carbon olefin, solves the problem of overhigh yield of ethanol cracking methane, maximally obtains ethylene and propylene, improves the selectivity of methane and coke, and realizes efficient utilization of ethanol and fossil resources.

The present application relates to a kind of silver catalytic oxidation preparation sulfoxide method, first preparation is supported silver catalyst, under the action of this silver catalyst, catalytic hydrogen peroxide oxidation sulfide preparation sulfoxide.The silver catalyst prepared by this method has high stability and can be recycled multiple times.It catalyzes the oxidation of sulfide to obtain sulfoxide with high efficiency.Silver catalytic oxidation of sulfoxide reaction process has the advantages of high efficiency and high selectivity, and the catalyst is easy to recover, and is friendly to the environment.The product is easy to separate, and has good industrial application prospect.

The invention discloses a preparation method of a macroporous magnesium-aluminum composite material, and belongs to the technical field of chemical engineering, and the method comprises the following steps: preparation of magnesium-aluminum sol, preparation of a first solution, preparation of a magnesium-aluminum dry gel film, preparation of a macroporous magnesium-aluminum composite material precursor and preparation of the macroporous magnesium-aluminum composite material. According to the invention, the alumina matrix is subjected to magnesium-aluminum coating modification, the pore structure of the magnesium-aluminum composite material is optimized, the surface acid-base property of the adsorbent material is improved by combining the modification of the organic ligand, and the adsorption selectivity of water vapor is greatly reduced while the structural stability of the material is ensured; the carbon dioxide can be efficiently captured in a high-water-vapor environment (such as air). The invention also discloses the macroporous magnesium-aluminum composite material prepared by the preparation method. Meanwhile, the invention further discloses application of the macroporous magnesium-aluminum composite material in the field of adsorption.

The application discloses a diesel oxidation catalyst for reducing N2O emission and a preparation method thereof. First and second catalytic coating layers of the catalyst are continuously coated on a carrier in sections, a third catalytic coating layer is located on the upper layer of the first catalytic coating layer, and a fourth catalytic coating layer is located on the upper layer of the second catalytic coating layer. The first and second catalytic coating layers are used for purifying HC / CO pollutants and oxidizing NOx into NO2. The third noble metal active component of the third catalytic coating layer is composed of Pt or a mixture of Pt and Pd, and the ratio of Pt / Pd is 5:1-1:0. The fourth noble metal active component of the fourth catalytic coating layer is one or more of Pt, Pd, Rh and Ru. The third catalytic coating layer is used for reducing the selectivity of the DOC catalyst to N2O when oxidizing NH3 and the selectivity to N2O when the HC-SCR reaction is performed. The fourth catalytic coating layer adopts a coating layer with N2O decomposition capacity, and the N2O selectively generated in the upstream section is decomposed into N2. The catalyst coating layers are mutually cooperative, have basic DOC catalytic performance, and can reduce N2O emission.

The invention relates to the field of oil refining catalysts, in particular to a high-activity catalytic cracking catalyst, a preparation method thereof and a method for reducing coke yield in catalytic cracking reaction. The catalytic cracking catalyst is prepared from the following components in percentage by weight: 5 to 40 percent of molecular sieve, 5 to 40 percent of clay, 5 to 35 percent of silicon species in terms of SiO2, 30 to 75 percent of aluminum species in terms of Al2O3, 0.5 to 5 percent of stable elements in terms of oxide and 0.5 to 10 percent of active regulating elements in terms of oxide, and is measured by a low-temperature nitrogen adsorption method, the total pore volume of the catalyst is not less than 0.5 mL / g, and the pore volume of pores with the pore diameter of 10-100 nm accounts for 80% or more of the total pore volume; and the micro-reactivity after being treated for 17 hours at 800 DEG C under 100% water vapor is not lower than 50%. The catalyst is high in heavy oil conversion rate, high in light oil selectivity and low in coke yield.

This invention discloses a bisphosphonophenylamine tridentate ligand compound, which is prepared from diphenylamine compounds, elemental bromine, n-butyllithium, organophosphorus compounds, etc. This ligand compound can be combined with transition metal compounds and aluminum-containing additives to form a catalyst composition for the catalytic reaction of ethylene tetramerization to 1-octene, exhibiting advantages such as high catalytic activity, high 1-octene selectivity, and low deactivation at high temperatures.

This invention relates to the field of flue gas purification catalyst technology, specifically to a coconut shell activated carbon-supported metal oxide catalyst and its application in flue gas purification. It uses hierarchical porous coconut shell activated carbon as a carrier, constructed sequentially through surface Al2O3 modification, inner cerium-lanthanum composite oxide loading, and a core manganese-copper active center. The key to its preparation lies in a three-step sequential impregnation-calcination process: first, the carrier surface is modified with aluminum sulfate solution; then, cerium and lanthanum nitrates are loaded to form a catalyst promoter layer; finally, the active components are loaded with an alcohol-water solution of manganese acetate and copper, and activated by calcination in a weakly reducing atmosphere. This method, by constructing a gradient structure of the modification layer, promoter layer, and active layer, significantly improves the dispersion of the active components, the low-temperature activity of the catalyst, and its anti-sintering ability. The resulting catalyst exhibits advantages such as high activity, long lifespan, and good stability in the field of volatile organic compound purification.

This invention relates to the field of mineral processing technology, and discloses a copper sulfide ore beneficiation reagent, its preparation method, and its application. The reagent is composed of 50-55 parts by weight of sodium dibutyl monothiophosphate, 20-25 parts by weight of sodium isobutyl xanthate, 10-15 parts by weight of modified mercaptothiocyanate, and 5-10 parts by weight of fusel oil. The modified mercaptothiocyanate is obtained by chemically modifying the molecular structure of conventional mercaptothiocyanates by introducing hydrophobic alkyl groups and / or sulfur-containing functional groups. The fusel oil is a mixture of C4-C8 fatty alcohols. The preparation method includes: weighing the raw materials; mixing and dissolving sodium dibutyl monothiophosphate and sodium isobutyl xanthate to obtain a mixed solution; adding the modified mercaptothiocyanate and stirring to obtain a reaction solution; adding the fusel oil, stirring, separating the liquid to obtain an oily liquid, and filtering to obtain the reagent. The mass ratio of the oily liquid to the mixed solution after separation is (20-80):(80-20), and the filtration time is 30-60 min. The reagent of this invention can be used in the flotation of copper sulfide ore, with a dosage of 60-120 g / t.

The invention relates to a preparation method of a catalytic cracking catalyst. The method comprises the following steps: carrying out contact treatment on a NaY molecular sieve and a rare earth salt solution or a mixed solution of the rare earth salt solution and an ammonium salt solution, filtering and washing to obtain preparation raw materials including the rare earth-containing NaY molecular sieve, an inorganic oxide binder and natural minerals, mixing, pulping and molding; carrying out deacidification treatment on the formed catalyst, so that the content of Cl <-> on the basis of the catalyst is reduced to be less than or equal to 1.5 wt%; and performing hydrothermal roasting treatment on the deacidified molded catalyst in an atmosphere environment in which pressure is applied externally and an aqueous solution containing an acidic substance or an alkaline substance is added externally, and removing alkali metal through ammonium exchange. According to the method, under the condition that the chlorine content in the catalyst is reduced, the damage of a large amount of released hydrochloric acid gas to a rare earth NaY molecular sieve crystal structure in the catalyst is relieved, so that the cracking performance of the catalyst is improved.

The application discloses a preparation method of pharmaceutical-grade glacial acetic acid. It belongs to the technical field of fine chemical industry. The method uses bio-based ethanol as raw material, and performs catalytic oxidation reaction with oxygen in a reaction rectifying tower under the action of a multifunctional composite ionic liquid catalyst designed by the application. After the reaction, the crude acetic acid liquid is purified by specific molecular sieve adsorption and multi-stage low-temperature gradient crystallization in sequence. The core of the application lies in catalyst design: by utilizing the "template effect" of acetate anions and the synergistic effect of palladium-ruthenium bimetallic nanoclusters, the application realizes the ultrahigh selectivity (>99.8%) and ultralong catalytic stability of ethanol to acetic acid under mild conditions. The integrated process avoids halogen and heavy metal pollution from the source, the product purity is greater than or equal to 99.99%, the content of key impurities (formic acid, propionic acid) is reduced by 1-2 orders of magnitude compared with traditional processes, and the energy consumption is significantly reduced. Therefore, the application is an efficient and pharmaceutical glacial acetic acid preparation path.

The present application belongs to the technical field of catalyst, and particularly relates to a method for hydrogenation reaction in production of triethylaluminum catalyzed by aluminum hydrogen structure activator. The present application provides a method for hydrogenation reaction in production of triethylaluminum catalyzed by aluminum hydrogen structure activator, which comprises adding triethylaluminum mother liquor and aluminum powder mixture mixed with aluminum hydrogen structure activator in advance into a reaction kettle, heating under stirring, passing in hydrogen and pressurizing, continuously keeping hydrogen passing in during the reaction to ensure that the reaction kettle is in a constant pressure state, and obtaining target product diethylaluminum hydride and hydrogenolysis byproduct ethane after the reaction is completed. The present application provides a hydrogenation reaction with introduction of aluminum hydrogen structure activator, effectively improves the hydrogenation reaction speed and production efficiency, simultaneously reduces by-reactions and production cost, the activator is convenient to add, does not additionally increase process burden, related by-products are easy to remove and do not affect the environment and production safety.

The present application belongs to the field of catalyst preparation, and relates to a catalytic cracking catalyst and a preparation method thereof. The catalytic cracking catalyst comprises 10-70 wt% of a cracking active component, 10-60 wt% of a binder and 10-70 wt% of clay, wherein the cracking active component comprises 5-100 wt% of a first Y-type molecular sieve and 0-95 wt% of a second molecular sieve; the first Y-type molecular sieve is a modified kaolin-based metacrystalline molecular sieve, and the sodium oxide content thereof is less than 2 wt%. The preparation method of the catalyst comprises the steps of beating, spray drying, washing, filtering and drying the cracking active component comprising the modified kaolin-based metacrystalline molecular sieve, the binder and the clay. The catalyst is used for heavy oil catalytic cracking reaction, and has good coke selectivity and high heavy oil conversion rate.

The invention relates to a heavy oil catalytic cracking aid and a preparation method and application thereof, and the method comprises the following steps: S1, mixing a first silicon source, a first aluminum source, clay, water and modified alumina and / or modified silica gel, adjusting the pH value of the mixture to 3-10, and then carrying out a first reaction; s2, carrying out spray drying on the mixed material obtained by the reaction, and carrying out first roasting treatment on the obtained solid; the modified aluminum oxide is aluminum oxide modified by magnesium and silicon, and the modified silica gel is silica gel modified by aluminum and phosphorus and / or boron. The heavy oil catalytic cracking aid prepared by the method disclosed by the invention has good heavy oil cracking ability, and the coke yield is reduced while the heavy oil conversion rate is increased.

The invention provides a noble metal catalyst and a manufacturing method and application thereof, the noble metal catalyst comprises a Pt-In-Ga / Al2O3 catalyst, the Pt-In-Ga / Al2O3 catalyst comprises an Al2O3 carrier and Pt-In2O3-Ga2O3 active components loaded on the Al2O3 carrier, and the total mass of the Pt-In2O3-Ga2O3 active components accounts for 5-50% of the total mass of the catalyst; according to the present invention, under the high temperature reaction condition, the catalyst still has the high methanol conversion rate and the high hydrogen production rate at the high space velocity, the CO selectivity is low, the CO content in the product is low, the methanol conversion rate, the CO content in the reformed gas, the hydrogen production rate and other properties are excellent under the long operation time working condition, and the long-term stability of the catalyst in use is improved.

The present application relates to isobutane dehydrogenation to isobutene chemical technology field, provide a kind of isobutane dehydrogenation to isobutene catalyst and its preparation method, the catalyst includes first active component, first adjuvant, second adjuvant and carrier.The preparation method of the catalyst includes the following steps: first, with isopropyl alcohol aluminum and bismuth nitrate pentahydrate as raw material preparation supported first adjuvant carrier;Then with alcohol-water solution as solvent, under stirring, join the platinum salt containing first active component and the alkali metal salt containing second adjuvant, then join the supported first adjuvant carrier, ultrasonic dispersion after vacuum rotary evaporation, again through drying, finally placed in muffle furnace calcination, obtain catalyst.The catalyst prepared by the method of the present application has good stability at higher dehydrogenation to isobutene reaction temperature, the range of adaptive reaction temperature is wider, has high activity while having high selectivity.

The invention relates to the field of molecular sieves, and particularly discloses a nano H-Beta molecular sieve, the grain size of which is less than 40nm. The XRD spectrum of the molecular sieve shows that the molecular sieve has the strongest peak at the 2theta angle of 23 degrees; the nano H-Beta molecular sieve disclosed by the invention is uniform in particle size, can improve diffusion of reactant molecules, and has good selectivity; the molecular sieve also has more exposed catalytic activity sites, so that the molecular sieve is good in catalytic activity and high in stability, the carbon deposition generation rate can be remarkably reduced, the catalytic efficiency of the molecular sieve is improved, and the molecular sieve is particularly suitable for being used as a catalyst and is particularly suitable for being used as a catalyst in preparation of diisopropylbenzene.

The application discloses a catalyst for efficiently preparing methyl methacrylate and application thereof. The catalyst is prepared by impregnation of active components and high-temperature nitrogen-treated zeolite molecular sieves to obtain a modified nitrogen-doped molecular sieve composite catalyst. The catalyst provided by the application has high formaldehyde conversion rate and methyl propionate selectivity, and the catalyst has certain stability. The catalytic reaction is carried out in a high-pressure autoclave reactor, raw materials are cheap and easy to obtain, the preparation method is simple, the reaction operation process is short, no greenhouse gas carbon dioxide is generated in the preparation of methyl methacrylate, and the catalyst has good application prospect in the petrochemical industry.

The application discloses a kind of catalyst and the method for directly converting synthesis gas to prepare aromatic hydrocarbon rich in benzene (B), toluene (T), dimethyl benzene (X), belongs to synthesis gas directly preparing aromatic hydrocarbon, with synthesis gas as reaction raw material, conversion reaction is carried out on fixed bed, the catalyst is composite catalyst I+II+III, three components are mechanically mixed, and the active component of component I is metal oxide I, component II is molecular sieve, and component III is molecular sieve.Reaction process has very high BTX product yield and selectivity, and aromatic hydrocarbon selectivity can reach 50-80%, and the proportion of benzene, toluene, dimethyl benzene in aromatic hydrocarbon can reach 30-80%, while by-product methane selectivity is less than 10%, with good application prospect.

This disclosure relates to a framework heteroatom titanium-silicon molecular sieve with hierarchical pores, its preparation method, and its application. The framework heteroatoms include titanium. The framework heteroatom titanium-silicon molecular sieve has the following characteristics: 29 Si MAS NMR characteristics: The peak area of ​​the peak at the chemical shift position of the framework heteroatom titanium-silicon molecular sieve at -103±1ppm is denoted as Q3; the peak area of ​​the peak at the chemical shift position of the framework heteroatom titanium-silicon molecular sieve at -113±1ppm is denoted as Q. 4‑1 The peak area of ​​the spectrum at the position with a chemical shift of -116±1ppm for the framework heteroatom titanium-silicon molecular sieve is denoted as Q. 4‑2 As defined in equation (1), X1 is any value between 0.02 and 0.35: X1 = Q3 / Q 4‑1 Equation (1); X2 is defined as any value between 0.10 and 0.60 as in Equation (2): X2 = Q3 / Q 4‑2 Formula (2). This molecular sieve has high catalytic activity and stability, and significantly improves the conversion rate of cyclohexanone oxime and the selectivity of caprolactam.

The present application relates to a kind of hydrophobic copper-based molecular sieve catalyst and its preparation method and use method, belong to copper-based catalyst technical field.The present application discloses a kind of hydrophobic copper-based molecular sieve catalyst, the hydrophobic copper-based molecular sieve catalyst includes the copper nanoparticle of mass ratio 1 :(0.3~1.2) :(1~10), methyl functional group, silica molecular sieve framework;The methyl functional group is located on the surface of silica molecular sieve framework, and copper nanoparticle exists in silica molecular sieve channel and / or cavity.This application also discloses the preparation method of hydrophobic copper-based molecular sieve catalyst and the use method of hydrophobic copper-based molecular sieve catalyst.This application will be evenly distributed in the copper nanoparticle in silica molecular sieve channel and / or cavity, and there is methyl functional group on the outside of urchin-shaped structure molecular sieve, in maleic anhydride selective hydrogenation make by-product water quickly leave catalyst surface, reduce the occurrence of hydrolysis side reaction, improve catalyst activity and reduce the selectivity of acid product.

The application provides a three-dimensional multi-stage hole phosphonated chitosan / microalgae-based aerogel and a preparation method and application thereof, and belongs to the technical field of aerogel preparation. The three-dimensional multi-stage hole phosphonated chitosan / microalgae-based aerogel (aCSP / CP) is prepared by taking chitosan (CS), phosphonated chitosan (CSP) and chlorella pyrenoidosa powder (CP) as raw materials. The selectivity of CP to U(VI) is low, but the total ion adsorption capacity is higher, and more coexisting ions can be adsorbed. The selectivity of CSP to U(VI) is greatly improved. The high affinity and high selectivity between the phosphorus functional groups in CSP and U(VI) can improve the selective adsorption of U(VI). In the application, CP and CSP synergistically act together to realize the high selective adsorption of U(VI).

The application discloses a kind of water quality comprehensive toxicity high flux determination method, the determination method includes using sewage sample to expose the test organism after being contaminated, obtains the phenotypic characteristic data of test organism;Toxicity matrix is constructed;Establish machine learning model, determine the water quality comprehensive toxicity of sewage sample in combination with toxicity matrix.The water quality comprehensive toxicity determination method provided by the application does not need sample concentration enrichment, guarantees the comprehensiveness and accuracy of detection result, and can be applied to the comprehensive toxicity high flux determination of sewage treatment plant whole-process sewage.

This invention discloses a composite catalyst, its preparation method, and its application. The composite catalyst comprises a metal oxide and a carbon-modified molecular sieve. The preparation method of the composite catalyst includes the following steps: (1) the molecular sieve undergoes pre-carbon deposition treatment to obtain a carbon-modified molecular sieve; (2) the metal oxide and the carbon-modified molecular sieve are mixed to obtain the composite catalyst. The composite catalyst provided by this invention is used in the CO / CO2 hydrogenation reaction to produce light aromatics, exhibiting high catalytic activity and high selectivity for light aromatics.