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The polyolefinic fraction of post consumer plastics waste was pyrolyzed in a fluidized bed lab scale reactor. In order to improve olefin yields, steam was used as the fluidizing agent. The influence of the reaction temperature on olefin yields was investigated in the range 600–800 °C. Furthermore, the residence time was varied at a given temperature of 700 °C between 1.8 and 3.2 s. The product distribution shows a characteristic influence of the cracking temperature on the yields of the different components. High amounts of olefins are obtained at temperatures around 700 °C, with 20–31 wt.% ethene, 14–18 wt.% propene, 3–6 wt.% butenes and, additionally, 19–23 wt.% pyrolysis gasoline as the main products. These yields are similar to the product distribution of naphtha cracked in a steam cracker, with 29 wt.% ethene, 16 wt.% propene, 10 wt.% butene/butadiene, and 24 wt.% pyrolysis gasoline. After separation the olefins can be reused as monomers for the production of polyolefins.

The composition of oils derived from the on-line, low pressure zeolite upgrading of biomass pyrolysis oils from a fluidized bed pyrolysis unit have been investigated in relation to the regeneration of the zeolite catalyst. The catalyst used was H-ZSM-5 zeolite. The gases were analysed by packed column gas chromatography. The composition of the oils before catalysis and after catalyst upgrading were analysed by liquid chromatography fractionation, followed by coupled gas chromatography—mass spectrometry of each fraction. In particular, the aromatic and oxygenated aromatic species were identified and quantified. In addition, the oils were analysed for their elemental composition and molecular weight range using size exclusion chromatography. Before catalysis the biomass pyrolysis oil was highly oxygenated but after catalysis a highly aromatic oil was formed with high concentrations of monocyclic aromatic hydrocarbons. In addition, significant concentrations of polycyclic aromatic hydrocarbons (PAH) were formed. Regeneration of the zeolite catalyst showed that continued regeneration reduced the effectiveness of the catalyst in converting biomass pyrolysis oils to an aromatic product. Elemental analysis of the upgraded oils showed an increase in the oxygen content of the oil with increasing regeneration of the catalyst. The molecular weight range of the oils was found to decrease markedly after catalysis, but continued regeneration of the catalyst increased the molecular weight range of the upgraded oils. Detailed analysis of the uncatalysed oils showed they contained low concentrations of aromatic and PAH species which markedly increased in concentration after catalysis. The overall effect of increasing catalyst regeneration was a decrease in the concentration of aromatic hydrocarbons and PAH. Also as the catalyst was regenerated, the number of methyl groups on the parent single ring aromatic compound or PAH increased. The oxygenated aromatic species in the oil before catalysis were mainly, phenols and benzenediols and their alkylated homologues. After catalysis some of the oxygenated species were reduced and some increased in concentration. A dual mechanistic route is suggested for the formation of aromatics and PAH during the catalytic upgrading of biomass pyrolysis oils: (1) the formation of low-molecular-weight hydrocarbons on the catalyst which then undergo aromatization reactions to produce aromatic hydrocarbons and PAH; (2) deoxygenation of oxygenated compounds found in the non-phenolic fraction of the pyrolysis oils which directly form aromatic compounds.

Mixed plastics collected from households were separated into a poly(vinyl chloride) (PVC) poor light fraction (0.66 wt.% chlorine) and pyrolyzed in a fluidized bed reactor. The process was optimized to give high amounts of olefins. For comparison, high density polyethylene was used as feed material. The pyrolysis products contained about 36% ethene, 15% propene, 9% 1-butene and butadiene and an additional 15% pyrolysis gasoline. The olefins could be used again after separation as monomers for the production of polyolefins.

The catalyst deactivation of the selective hydrogenation of pyrolysis gasoline of a commercial plant was investigated. Both the fresh and the regenerated catalysts, sampled from the commercial plant, were characterized by the palladium wt %, BET surface area, pore volume, the dispersion of Pd/Al[sub 2]O[sub 3], XRD (X-ray diffraction), and EPMA (electron probe microanalyzer). The results indicated that the major factors affecting the catalyst deactivation of the selective hydrogenation of pyrolysis gasoline of a commercial plant are palladium migration and coke deposition, 53.2%, poor palladium dispersion, 37%, and palladium metal loss, 9.8%. However, the pore mouth plugging, loss of surface area, and phase change of support were the minor factors for catalytic deactivation. The first findings of the effect of palladium migration on the catalyst deactivation of the eggshell palladium profile catalyst are meaningful and important for improving the performance of the catalyst with nonuniform active site distribution.

Hydrocracking of saturated hydrocarbons can proceed by means of four distinctly different mechanisms. On bifunctional catalysts comprising hydrogenation/dehydrogenation and Bronsted acid sites alkenes and carbocations occur as intermediates. The current mechanistic views of bifunctional hydrocracking of long-chain n-alkanes are discussed in detail with emphasis on the now widely accepted concept of ideal hydrocracking. Other mechanisms are hydrogenolysis and Haag–Dessau hydrocracking which proceed, respectively, on monofunctional metallic and acidic catalysts. Even without a catalyst, thermal hydrocracking occurs in chain reactions via radicals. The chemistry of hydrocracking naphthenes on bifunctional catalysts resembles that of alkanes. A peculiarity, however, is the pronounced reluctance of cyclic carbenium ions to undergo endocyclic β-scissions. The effect manifests itself in the so-called paring reaction, which, in turn, forms the basis for measuring the Spaciousness Index for characterizing the effective pore width of zeolitic catalysts. Hydrocracking on bifunctional catalysts is among the very important processes in modern petroleum refining. It is primarily used for converting heavy oils into diesel and jet fuel. Besides, hydrocracking is appreciated for its pronounced versatility: numerous process variants exist which help to meet specific requirements in refineries or petrochemical plants. Two recent developments are briefly discussed in this review, viz. the conversion of surplus aromatics, e.g., in pyrolysis gasoline, into a synthetic feedstock for steam crackers, and quality enhancement of diesel fuel by selective ring opening of polynuclear aromatics.

To optimize the chemical composition of catalysts for the selective hydrogenation of diene and vinyl aromatic hydrocarbons in pyrolysis gasoline, we study the effect of the acid-base and textural characteristics of a support modified with additives of sodium compounds on the activity and stability of the catalysts in reactions of hydrogenation and oligomerization of unsaturated compounds. It is shown that the rate of formation of oligomeric compounds depends on the number of Lewis (Q CO > 34 kJ/mol) and Brönsted sites (νOH = 3688 cm-1). An increase in their total amount on the catalyst surface leads to an increase in the rate of formation of oligomeric hydrocarbons. The amount of surface condensation products is determined by the concentration of strong aprotic sites with Q CO > 35 kJ/mol. Alumina support samples with a high surface concentration of medium-strong Lewis sites, wedge-shaped or conical pores, and the preferential distribution of porometric volume in pores with a diameter of 5-15 nm are characterized by a significant ability to oligomerize unsaturated compounds. Catalysts that contain 0.5 wt % Na exhibit the lowest oligomerization ability and a high stabile activity in reactions of hydrogenation of diene and vinyl aromatic hydrocarbons in pyrolysis gasoline. For the selective hydrogenation of diene and vinyl aromatic hydrocarbons in pyrolysis gasoline, we recommend a catalyst with 0.5 wt % Pd supported from palladium acetylacetonate on δ-Al2O3 modified with 0.5 wt % sodium; it is characterized by the absence of wedge-shaped or conical pores, the preferential (60.7%) distribution of porometric volume in a range of d p > 15 nm, and a low aprotic acidity (L = 3.1 μmol/g), which contributes to the decrease in the amount of resulting condensation products (V = 3.6 μg/(gcat h)) and a high stable activity (DN = 0.68 g J2/100 g) in reactions of hydrogenation of unsaturated compounds. © 2010 Pleiades Publishing, Ltd.

The heavy-RPG(Raw Pyrolysis Gasoline), which is a variable mixture of mainly unsaturated C9 fractions in the cracking of petroleum naphthas, is one of the important feed materials for petroleum resins. To produce the resin with favorable quality, one need to use well purified fraction of the h-RPG and, accordingly, a knowledge of the phase equilibria for the h-RPG is required. The h-RPG, however, is regarded as a typical continuous mixture which contains far too many components for standard chemical analysis. Thus, we present here an efficient method collecting phase equilibrium data for such a mixture based the method of continuous thermodynamics and the PengRobinson equation of state. First, through the gas Chromatographie analysis and the ASTM D86 experiment for a typical h-RPG mixture, we identified the total number of 43 constituents and found the distribution of TBPs. Then, the continuous fraction of h-RPG mixture is characterized by gamma function where the TBP index is used as the distribution variable. Finally, we performed bubble and dew point, and flash calculations by the quadrature method to the continuous fraction. The results are compared with those calculated by the pseudo-component methods. We found that the method presented here can be used for the reliable phase equilibrium calculation of such a continuous mixture while significantly reduce the computation time with more favorable accuracy over the conventional pseudocomponent method.

There was a high rate of corrosion in Pyrolysis Gasoline Hydrogenation (PGH) unit of Arak Petrochemical Company (ARPC), and it caused some operational problem in this plant. A commercial chemical had been used as anti-corrosion in the depentanizer column overhead in order to control the corrosion rate. Injection of commercial corrosion inhibitor caused some operational problems such as fouling in some heat exchangers. It was proposed to replace this commercial material with another more effective trouble free, and well-known additive by R&D and operation specialists. At first, the system was simulated by commercial simulation software in electrolytic system to specify low pH points inside the plant. After a very comprehensive study of the situation and technical investigations ,ammonia / monoethanol amine solution was proposed as neutralizer or corrosion inhibitor to be injected in a suitable point of the plant. For this purpose, the depentanizer column and its accessories system was simulated again in case of this solution injection. According to the simulation results, injection of new anticorrosion substance has no any side effect on C5 cut product and operating conditions of the column. The corrosion rate will be cotrolled, if the pH remains at the range of 6.5 to 8 . Aactual plant test run was also carried out by injection of ammonia / monoethanol amine solution at the rate of 0.6 Kg/hr and the results of iron content of water samples and corrosion test coupons confirmed the simulation results. Now, ammonia / monoethanol amine solution is injected to a suitable pint inside the plant and corrosion rate has decreased significantly., {"references":["Manual of Pyrolysis Gasoline Hydrogenation Plant (PGH), Arak\nPetrochemical Company ,Iran, Vol. I &II , june 1991.","S. Khajehmandali and R. Hassannezhad, \"Simulation of Depenthaniser\nof Pyrolysis Gasoline Hydrogenation Plant in Arak Petrochemical\nCompany Based on ElectrolyteSystem in order to Replacing Trademark\nAnticorrosion by Ammonia Solution in the Plant and Test Run,\" 10th\nNational Iranian Chemical Engineering Congress Proceeding,\nSistan&Balochestan University, Iran, October 21-23, 2005.","R. D. Merrick, and T. Auerbach, \"Crude Unit Overhead Corrosion\nControl,\" Materials Performance, September 1983, pp. 15.","E.C. French, and W.F. Fahey, \"Water Soluble Filming Inhibitor System\nfor Corrosion Control in Crude Unit Overheads,\" Materials\nPerformance, September 1983, pp. 9.","J.G. Edmonson, and S.E. Lehrer, \"Advances in Neutralizing Amine\nTechnology,\" CORROSION/94, Paper # 514, NACE, Houston, Texas,\n1994.","P. R. Petersen, S. R. Lordo and G. R. McAteer, \"Choosing a\nNeutralizing Amine Corrosion Inhibitor,\" PTQ, Summer 2004, pp. 121-\n127.","D. W. Green, and et al, \"Perry's chemical engineers' handbook,\" 7th ed.,\nNew York, McGraw-Hill, 1997 , pp. 23-11."]}

The sections in this article are Introduction Fundamentals of Hydrodecyclization of Cycloalkanes Hydrogenolysis on Metals Hydrocracking on Bifunctional Catalysts Cracking and Activation of Hydrogen on Monofunctional Acidic Catalysts Ring Opening of Aromatics in Diesel and Jet Fuels Bifunctional Catalysts Metal Catalysts Acid Catalysts Ring Opening of Aromatics in Gasoline Without Degradation of the Carbon Number Ring Opening of Aromatics in Pyrolysis Gasoline Followed by Hydrocracking into a Synthetic Steam-Cracker Feed Hydrodecyclization and Hydrocracking of Cycloalkanes on Acid Zeolites Direct Ring Opening of Aromatics on Bifunctional Zeolites Conclusions Acknowledgments Keywords: aromatic hydrocarbons; ring opening; hydrodecyclization catalysts; petrochemicals; jet fuel; diesel fuel; gasoline

Pyrolysis gasoline - PYGAS - is an intermediate boiling product of naphtha steam cracking with a high octane number and high aromatic/unsaturated contents. Due to stabilization concerns, PYGAS must be hydrotreated in two stages. The first stage uses a mild trickle-bed conversion for removing extremely reactive species (styrene, dienes and olefins) prior to the more severe second stage where sulfured and remaining olefins are hydrogenated in gas phase. This work addresses the reaction network and two-phase kinetic model for the first stage of PYGAS upgrading. Nonlinear estimation was used for model tuning with kinetic data obtained in bench-scale trickle-bed hydrogenation with a commercial Pd/Al2O3 catalyst. On-line sampling experiments were designed to study the influence of variables - temperature and spatial velocity - on the conversion of styrene, dienes and olefins.

Conselho Nacional de Desenvolvimento Científico e Tecnológico The quality of gasoline may be affected by the presence of several compounds. Among them, the conjugated dienes play an important role due to the fact that their presence is strongly associated with gum formation, which may clogs the injector of automobiles and may causes damages in the petroleum derivates. The main used method for the determination of total conjugated dienes is the UOP-326 method. However, the long analysis time (from 5 to 6 hours) is the main disadvantages. The available methodologies investigated as alternative to the UOP-326 method do not solve the problem properly. The present work reports the use of multivariate models to assess the diene value (DV) in pyrolysis gasoline samples starting from voltammetric and spectrophotometric data. The calibrations were carried out using the UOP-326 method instead of diene standards. In the voltammetric model, starting from a group of 24 hydrogenated pyrolysis gasoline, the PLS (Partial Least Squares) method was used to predict the DV in an independent group of 7 samples. The deviations observed were lower than 12,2% comparing to the UOP-326 method. In a group of 24 non-hydrogenated pyrolysis gasoline samples, an independent group of 7 samples was also used to predict the DV. The deviations observed were lower than 4,1%. In the spectrophotometric approach, the PLS method was used to predict the DV in an independent group of 5 samples of hydrogenated pyrolysis gasoline (n=21). The deviations observed were lower than 11% by comparing to the UOP-326 method. In a group of 26 non-hydrogenated pyrolysis gasoline samples, an independent group of 10 samples was used to predict the DV. The deviations observed were lower than 5,7%. Comparing the voltammetric and spectrophotometric methods, the former showed more reliable results with lower RMSEP (Root Mean Square Error of Prediction) values. A qualidade da gasolina é afetada pela presença de diversos compostos. Entre eles, os dienos conjugados possuem um importante papel devido ao fato de estarem associados à formação de goma, que forma depósitos no injetor de combustível de automóveis e diminui a qualidade dos produtos petrolíferos. O método comumente utilizado para a determinação de dienos conjugados totais é o método UOP-326. Contudo, ele apresenta como principal desvantagem o longo tempo de análise (de 5 a 6 horas). As metodologias já investigadas que visam substituir o método UOP-326 na quantificação de dienos conjugados em gasolina não resolvem adequadamente o problema. Dessa forma, o presente trabalho aborda o uso de modelos multivariados para a avaliação do valor de dienos (DV) em amostras de gasolina de pirólise a partir de dados voltamétricos e espectrofotométricos, utilizando o método UOP-326 para a calibração do sistema. No modelo voltamétrico, de um grupo de 24 amostras de gasolina de pirólise hidrogenada, utilizou-se o método PLS (Regressão por Mínimos Quadrados Parciais) para a predição do DV em um grupo independente de 7 amostras, obtendo-se desvios inferiores a 12,2% quando comparado ao método UOP-326. E em 24 amostras de gasolina de pirólise não hidrogenada, um grupo independente de 7 amostras foi utilizado para a predição do DV, obtendo desvios inferiores a 4,1%. No modelo espectrofotométrico, utilizou-se o método PLS para a predição do DV em um grupo independente de 5 amostras de gasolina de pirólise hidrogenada (n=21), obtendo-se desvios inferiores a 11% quando comparado ao método UOP-326. E em 26 amostras de gasolina de pirólise não hidrogenada, um grupo independente de 10 amostras foi utilizado para a predição do DV, obtendo-se desvios inferiores a 5,7%. Na comparação entre os métodos voltamétrico e espectrofotométrico, o primeiro mostrou-se mais confiável, apresentando valores de RMSEP (erro médio dos resíduos quadráticos de predição) inferiores para ambas as amostras.

Environmental legislation will restrict the total aromatic content in gasoline. Consequently, the amount of heavy pyrolysis gasoline (a by-product from steam cracker, mainly composed of C 7 –C 9 aromatics) blended into motor gasoline will be limited. Hydrocracking into premium stream cracker feed has been suggested as a possible way to get value from pyrolysis gasoline. Pd/LaH-Y proved to be an effective catalyst not only in the hydrocracking of C 7 –C 9 aromatics, but also of polynuclear aromatics (e.g. naphtalenes). Feed with relevant sulphur content can be successfully hydrotreated too.

A model is developed based on a two-stage hydrogenation of pyrolysis gasoline to obtain a C6-C8 cut suitable for extraction of aromatics. The first stage hydrogenation takes place in a trickle bed reactor while the second stage hydrogenation is carried out in a two compartment fixed bed reactor in which hydrogenation of olefins takes place in the first compartment while the sulphur is eliminated in the second compartment. The key component in this stage is considered to be cyclohexene whose hydrogenation was found to be the most difficult among other olefins in the feed. The LangmuirHinshelwood kinetic expression was adopted for hydrogenation of cyclohexene and its kinetic parameters were determined experimentally in a micro-reactor. The model was solved for the whole process of hydrogenation, including hydro-desulphurization. The predictions of the model were compared with the actual plant data of an industrial scale pyrolysis gasoline hydrogenation unit and satisfactory agreement was found between the model and the plant data.

Biomass in the form of pine bark (Pinus brutia Ten.) was pyrolysed in an externally heated fixed-bed reactor. The effects of temperature and heating rate on the yields and compositions of the products were investigated. Pyrolysis runs were performed using reactor temperatures between 300 and 500 degrees C with heating rates of 7 and 40 degrees Cmin(-1). The product yields were significantly influenced by the process conditions. The bio-oil obtained at 450 degrees C, at which the liquid product yield was maximum, was analysed. It was characterized by Fourier transform infrared spectroscopy. In addition, the solid and liquid products were analysed to determine their elemental composition and calorific value. Chemical fractionation of bio-oil showed that only low quantities of hydrocarbons were present, while oxygenated and polar fractions dominated. The empirical formula of the bio-oil with heating value of 31.03 MJkg(-1) was established as CH(1.43)O(0.332)N(0.0013).

Development of mathematical models for chemical process simulation has been the main focus of research for many years. In the past trickle bed reactor models for various reaction systems were validated with pilot plant data but the development of a dynamic model based on industrial data is rare. Kittisupakorn and Arpornwichanop (1999) have recently developed a steady state model of an industrial trickle-bed reactor for the above system. However, this model is only applicable to predict steady state conditions and inapplicable to design startup and shutdown as well as control studies. Therefore, in this work, a dynamic model of an industrial trickle-bed reactor for describing the hydrogenation reactions of a pyrolysis gasoline in an olefin plant has been developed based on actual plant data. The model results to a set of partial differential equations which were solved by method of lines with approximate spatial derivative terms by an orthogonal collocation method. The model was used to study the response of the process. The simulation results demonstrated that the dynamic response gave a reasonable path from a transient to steady state condition. This dynamic model will be used in future in the formulation of model based control strategies in order to control the reactor.

Publisher Summary Benzene, toluene, and xylenes (BTX) are a valuable petrochemical feedstock that can be produced from aromatic rich stream by upgrading naphtha reformate or pyrolysis gasoline in the refinery. However, with the advent of the modern continuous catalyst regeneration (CCR) reformer, the operation of conventional fixed bed reformer has declined drastically. There are also ample supply of the low value naphtha reformate. It is therefore desirable to produce BTX enriched aromatic stream using the surplus reformate in the idled unit. Aromatics produced can be recovered by solvent extraction. But the extraction unit in the loop has limited processing capacity to handle the extra amount of BTX produced. A novel noble metal that promoted shape selective zeolite catalyst is developed to utilize the idled fixed bed reformer to convert surplus reformate into valuable BTX streams and liquefied petroleum gas (LPG) without adding extra burden to the solvent extraction columns.

Publisher Summary The primary sources of benzene, toluene, and xylenes (BTX) are refinery streams, especially from catalytic reforming and cracking, and pyrolysis gasoline from steam cracking and from coal liquids. BTX and ethyl benzene are extracted from these streams using selective solvents such as sulfolene or ethylene glycol. The extracted components are separated through lengthy fractional distillation, crystallization, and isomerization processes. The reactivity of C6, C7, C8 aromatics is mainly associated with the benzene ring. Aromatic compounds in general are liable for electrophilic substitution. Most of the chemicals produced directly from benzene are obtained from its reactions with electrophilic reagents. Benzene could be alkylated, nitrated, or chlorinated to important chemicals that are precursors for many commercial products. Toluene and Xylenes (methylbenzenes) are substituted benzenes. Although the presence of methyl substituents activates the benzene ring for electrophilic attack, the chemistry of methyl benzenes for producing commercial products is more related to reactions with the methyl than with the phenyl group. As an electron-withdrawing substituent (of methane), the phenyl group influences the methyl hydrogens and makes them more available for chemical attack. With details and indepth description, the chapter shows that the methyl group could be easily oxidized or chlorinated as a result of the presence of the phenyl substituent.

In initiator/TiCl4-initiated cationic polymerization, studies of the dynamics of reaction systems must be conducted within a certain range of the concentration ratio between the initiator and TiCl4. The current study explored the range of the concentration ratio of CH2Cl2/TiCl4 in the cationic polymerization of pyrolysis gasoline. AlCl3 and TiCl4 were used as the catalysts. The compositions and iodine values of the light components were analyzed using gas chromatography-mass spectrometry and the iodine–alcohol method, respectively. The molecular weights of the resulting polymers were analyzed using gel permeation chromatography, and their compositions were analyzed using Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. In the CH2Cl2/TiCl4-initiated cationic polymerization of multiple-olefin-containing C9 pyrolysis distillate, the CH2Cl2/TiCl4 ratio needed to be ≤1 for effective initiation. A low concentration of olefins in the reaction systems yielded satisfactory polymerization. The temperature for the CH2Cl2/TiCl4-initiated polymerization of the C9 pyrolysis distillate was 50 °C, and the amount of TiCl4 was 1.5%. The olefins in the C9 pyrolysis distillate were effectively isolated from the saturated solutions through cationic polymerization, and the resulting light oil was transparent and colorless. The analysis of the resulting polymers suggested the secondary polymerization of low-molecular-weight polymers after the addition of initiator/TiCl4.

December 23, 1994 the wall of the first stage pyrolysis gasoline hydrogenation reactor in DSM's NAK3 steam cracker ruptured, requiring an emergency shutdown of, the plant. A mixture of gasoline, hydrogen and nickel catalyst escaped through the crack and immediately caught fire. There were no personal injuries, but property damage was substantial. There had been no domino effects, nor had there been any danger to the surrounding area. One week after this severe fire NAK3 was put back into operation except for the first stage pygas hydrogenation. Thermodynamic calculations, analysis of the process data and of the catalyst and reactor wall indicated that the bulge and subsequent rupture of the reactor wall were caused by a brief local temperature excursion to 700–750 °C at an operating pressure of 30 bar. This temperature excursion can be explained by maldistribution of the liquid and thus poor heat transfer caused by local excessive carbon formation in the reactor in the period preceding the incident. Disruption of the heat removal can cause a chain of exothermic reactions, viz . hydrogenation of olefins, aromatics, as well as hydrocracking. Results of the investigation as well as the improvements made in the operation and procedures are presented in this paper.

A stable nano-sulfide composite catalyst was synthesized and developed to improve the catalysis of classic pyrolysis gasoline hydrorefinery, based on the rigorous requirement of practical full-ranged (FR) feedstock. Through controlling active components on shielded nanosubstrates, the developed nanocatalyst showed superior characteristics over 1000 h of catalytic test, such as 1) high dispersibility of active components, 2) ultrastability under high space velocity (SV) and complex feedstock conditions and 3) better anti-impurity ability.

Aromatics with 6 to 9 carbon atoms can be converted catalytically with hydrogen on bifunctional zeolites, such as Pd/H-ZSM-5, into a high-quality steamcracker feed, thereby opening a direct route for the utilisation of surplus pyrolysis gasoline.

An industrial trickle bed reactor was simulated for pyrolysis gasoline selective hydrogenation. The operation was recognised in the upper limit of pulsing flow regime by the Charpentier-Tosun flow pattern diagram at a very low hydrogen to oil volumetric ratio. Hydrodynamic parameters in the pulsing flow regime were calculated from the literature correlations which apply to the hydrogen-paraffin system. The external wetting efficiency which should be no higher than 100% was found to be 147% according to the correlation of Al-Dahhan and Dudukovic (1995), due to the undefined upper limit of their equation. The reactor simulation shows the gas-liquid and liquid-solid mass transfer rates were large enough for the active Pd hydrogenation catalyst. By comparing with the mass transfer rate in the Taylor flow regime in a monolithic structure, it shows the hydrogen concentration in the liquid phase in an industrial trickle reactor is more than two times of that in the monolith, which implies the substitution of the conventional catalyst pellet by the monolith is not required.

A polycyclic aromatic is contacted with an alkyl-substituted single ring aromatic, such as toluene, o-, m- or p-xylene or mesitylene, over a catalyst comprising a zeolite, such as zeolite beta, USY or ZSM-5 to alkylate the polycyclic aromatic. The polycyclic aromatic can be a fused polynuclear aromatic, e.g. phenanthrene, or an assembly of two or more cyclic systems, e.g. biphenyl. The polycyclic aromatic can also include carbocyclic systems such as fluorene and naphthalene or heterocyclic systems such as benzothiophene and dibenzothiophene. The polycyclic aromatic can be derived from a cycle oil, coker gas oil, extract of lubricant solvent refining or crude distillate fraction. The transalkylating agent can be derived from a reformate, pyrolysis gasoline or coker naphtha.

Pilot plant experiments showed that selective hydrogenation of diolefine compounds in pyrolysis gasoline, at present achieved by trickle flow reactor, may be better achieved by flooded bed reactor, with co-current upflow of reagents. Advantages of the flooded bed reactor with respect to trickle flow are higher selectivity, higher catalyst life and less residue production. The use of a flooded bed reactor appears to be an inexpensive way to allow reaction to be accomplished extensively in the liquid phase.

The hydrogenation of pyrolysis gasoline was carried out over a supported palladium catalyst. Some of the operation variables which showed the effects on catalyst reduction and pyrolysis gasoline hydrogenation were discussed. The reduction conditions were studied by TPR technique and verified by the hydrogenation reaction. The supported palladium oxide could be reduced to palladium completely in less than one hour at 100°C and 4.5 atm of H2. The sintering of palladium became significant when the reduction temperature was above 300°C. The reaction temperature which gave the maximum pseudo rate constant of hydrogenation increased with increaing pressure. The kinetics of hydrogenation of model compounds, isoprene and styrene, were also studied in a semibatch basket reactor. The increase in hydrogen pressure not only enhances the rate of hydrogenation but also depresses the polymerization of dienes. It can be concluded that the reaction temperature and pressure should be compromised in order to obtain the optimum operation for hydrogenation of diene to monoolefin.

In this paper, the use of temperature-pro- grammed oxidation (TPO) is highlighted as a means of interrogating the surface of catalysts. Most studies only concern themselves with the active portion of the catalyst bed; in this study, we examine both the active part and the part that experiences equilibrated gas after reaction. The extent and nature of carbonaceous deposits on both sections of catalyst have been characterised by TPO and reveal that there is significant deposition of low H:C ratio carbonaceous species on catalyst that has only seen equilibrated reaction gas. This has potential implications for the life of the catalyst bed and the activity and selectivity observed.

A basic process for production of benzene from petroleum, along with catalytic reforming, is processing of liquid pyrolysis products and toluene. The conversion of pyrolysis gasoline and toluene on an iron-chromium oxide catalyst in a medium of steam and hydrogen at atmospheric pressure was investigated. Catalytic conversion of the pyrolysis gasoline was carried out in a medium of steam in a gradientless spherical reactor made of Kh23N18T steel under the following conditions: temperature 750 to 840/sup 0/C; steam pyrolysis gasoline weight ratio 1:1; pyrolysis gasoline feed rate 1 g per g catalyst per hour; experiment time 1 hour; catalyst volume 8 cm/sup 3/. Hydrodealkylation of toluene was also studied with the goal of producing benzene. In contrast to the conversion of pyrolysis gasoline in a medium of steam, hydrodealkylation was accomplished in a medium of steam and hydrogen. The preliminary tests showed that higher selectivity for formation of benzene is achieved in the presence of hydrogen. 11 references, 4 tables.