Treating processes catalytic

Catalytic methanation processes include (/) fixed or fluidized catalyst-bed reactors where temperature rise is controlled by heat exchange or by direct cooling using product gas recycle (2) through wall-cooled reactor where temperature is controlled by heat removal through the walls of catalyst-filled tubes (J) tube-wall reactors where a nickel—aluminum alloy is flame-sprayed and treated to form a Raney-nickel catalyst bonded to the reactor tube heat-exchange surface and (4) slurry or Hquid-phase (oil) methanation. 

Acid-treated clays were the first catalysts used in catalytic cracking processes, but have been replaced by synthetic amorphous silica-alumina, which is more active and stable. Incorporating zeolites (crystalline alumina-silica) with the silica/alumina catalyst improves selectivity towards aromatics. These catalysts have both Fewis and Bronsted acid sites that promote carbonium ion formation. An important structural feature of zeolites is the presence of holes in the crystal lattice, which are formed by the silica-alumina tetrahedra. Each tetrahedron is made of four oxygen anions with either an aluminum or a silicon cation in the center. Each oxygen anion with a -2 oxidation state is shared between either two silicon, two aluminum, or an aluminum and a silicon cation. 

HyChlor Formerly called DHC. A catalytic hydrodechlorination process which converts organic chlorides to hydrogen chloride and saturated hydrocarbons. The UOP HyChlor process recovers and recycles both the organic and inorganic reaction products in order to minimize waste disposal requirements and maximize yield. Used for treating wastes from the production of chlorinated petrochemicals such as vinyl chloride. Developed by UOP but not commercialized as of 1992. 

The development of a catalytic hydroboration process was aided by the observation of Kono and Ito in 1975 that Wilkinson s catalyst [Rh(PPh3)3Cl] 2 undergoes oxidative addition when treated with catecholborane 1 (Scheme l).6... 

Ti-F bond and generate a Ti-H species when 99 was treated with phenylsilane. The chirality transfer may take place through imine insertion into the Ti-H bond, similar to that in the catalytic hydrogenation process.1000 The reaction can be carried out by the subsequent addition of imines. The corresponding silylated amines can be obtained and further converted to enantiomerically enriched amines upon acid treatment. For example, in the presence of 99, N-methylimine 100 undergoes complete hydrosilylation within 12 hours at room temperature, with 97% ee and up to 5000 turnovers.103... 

Tail gas cleanup is required because a well-designed Claus plant with three catalytic stages and fresh catalyst will recover only 95-97% of its feed sulfur (8), which is not generally sufficient to meet current emission standards. In addition, feed impurities and catalyst aging will reduce overall recovery in some plants to about 92% just before catalyst changeout. Therefore, tail-gas cleanup is required. Tail-gas treating processes are generally classified as follows ... 

It safely treats process offgases using a combination of thermal treatment, catalytic oxidation, activated carbon filters, and treatment of the munitions demilitarization building (MDB) HVAC system ventilation air through activated carbon filter media prior to release. 

Caustics are widely used in petroleum refineries. Typical uses are to neutralize and to extract acidic materials that may occur naturally in crude oil, acidic reaction products that may be produced by various chemical treating processes, and acidic materials formed during thermal and catalytic cracking such as H2S, phenolics, and organic acids. 

Prior to 1938, gasoline was obtained from thermal-cracking plants then the Houdry fixed-bed catalytic cracking process led to the development of a fluidized-bed process by Standard Oil for the catalytic production of motor fuels (4-8). Acid-treated clays of the montmorilIonite type were the first fluid-cracking catalysts widely employed by the industry. However, the ever greater demand for aviation fuels during the 1939-1945 period prompted the search for more active and selective catalysts. Research on novel catalyst... 

M4 Environmental, L.P., has developed the catalytic extraction process (CEP) for treating hazardous wastes. In CEP technology, a bath of molten metal is used as a catalyst to dissociate... 

Catalytic cracking processes evolved in the 1930s from research on petroleum and coal liquids. The petroleum work came to fruition with the invention of acid cracking. The work to produce liquid fuels from coal, most notably in Germany, resulted in metal sulfide hydrogenation catalysts. In the 1930, a catalytic cracking catalyst for petroleum that used solid acids as catalysts was developed using acid-treated clays. 

Gulfining a catalytic hydrogen treating process for cracked and straight-run distillates and fuel oils, to reduce sulfur content improve carbon residue, color, and general stability and effect a slight increase in gravity. 

Cerqueira and co-workers203 confirmed the appearance of the of the tetrahedral aluminium and phosphorus in AlPO-like crystalline structures both in beta (BEA) and in MOR zeolites treated with phosphoric acid. 31P MAS,27Al MAS and TQM AS NMR spectra permitted the species present in the samples to be assigned. Possibly, besides the the Altet-f species, other Al species are also taking part in the activity and selectivity of the catalysts. The formation of Alocl o P can also contribute to the increase in the activity by preventing further dealumination. Dual zeolite additives have no impact on the quality of naphtha when compared to MFI-based additives, which are used in the fluid catalytic cracking processes. 

The Rectisol process, developed by Lurgi, is the most widely used physical solvent gas treating process in the world. More than 100 Rectisol units are in operation or under construction worldwide. Its most prevalent application is for deep sulfur removal from syngas that subsequently undergoes catalytic conversion to such products as ammonia, hydrogen, and Fischer-Tropsch liquids. 

Treatment of Lamffill Leachates. Landfill leachate contains large quantities of nonbiodegradable and toxic constituents. Some heterogenous catalytic ozonation processes (Ecoclear or Catazone systems) can successfully treat landfill leachates. " In addition, ozone-based AOPs have also been successfully used to remove COD or TOC either as pretreatment or at the final stage of the treatment. Both heterogenous catalytic ozonation and the AOP processes are introduced below. 

Starting from MPDA an overall yield for the process of around 90% is obtained, which means that the carbon efficiency (ratio of carbon in product to reactants) and overall atom efficiency (yield ratio of molecular weight of product to reactant) are 90% and 99%, respectively. The waste and any toxic by-products generated from the process are catalytically treated to give nitrogen, water and low quantities of carbon dioxide (about 200 kg per ton nicotinamide). 

Alkynes provide one of the most fruitful sources of vinylsilanes. Terminal and internal alkynes can be treated directly with silyl cuprates, or with hydridosilanes (hydrosilylation—see Chapter 17) problems of regio-selectivity arise in internal cases. Alternatively, terminal alkynes can be converted into the corresponding alkynylsilanes (Chapter 7) such species react regioselectively with a wide range of organometallic reagents, and they can also be reduced catalytically. These processes are summarized here for terminal alkynes ... 

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