Catalyst continued molten

Reduction of the aromatic nuclei contained in catalytic C-9 resins has also been accomplished in the molten state (66). Continuous downward concurrent feeding of molten resin (120°C softening point) and hydrogen to a fixed bed of an alumina supported platinum—mthenium (1.75% Pt—0.25% Ru) catalyst has been shown to reduce approximately 100% of the aromatic nuclei present in the resin. The temperature and pressure required for this process are 295—300°C and 9.8 MPa (lOO kg/cni2), respectively. The extent of hydrogenation was monitored by the percent reduction in the uv absorbance at 274.5 nm. 

Novolak Resins. In a conventional novolak process, molten phenol is placed into the reactor, foHowed by a precise amount of acid catalyst. The formaldehyde solution is added at a temperature near 90°C and a formaldehyde-to-phenol molar ratio of 0.75 1 to 0.85 1. For safety reasons, slow continuous or stepwise addition of formaldehyde is preferred over adding the entire charge at once. Reaction enthalpy has been reported to be above 80 kj /mol (19 kcal/mol) (29,30). The heat of reaction is removed by refluxing the water combined with the formaldehyde or by using a small amount of a volatile solvent such as toluene. Toluene and xylene are used for azeotropic distillation. FoHowing decantation, the toluene or xylene is returned to the reactor. 

Oxychlorination of methane can yield significant amounts of methylene chloride. A number of patents were obtained by Lummus in the mid-1970s on a high temperature, molten salt oxychlorination process (22,23). Catalyst development work has continued and generally consists of mixtures of Cu, Ni, Cr, or Fe promoted with an alkah metal (24—27). There are no industrial examples of this process at the present time. 

New and improved polymerization catalysts are continuously being developed to produce polymer with higher rates and with improved properties. Early Ziegler Natta catalysts were supported on porous alumina or sihca catalyst supports. These catalysts had low activity, and large amounts of catalysts had to be used that had to be separated from the molten polymer because otherwise the catalyst would color the polymer. With high-activity catalysts, the catalyst can be left in the polymer, thus saving considerable cost in separation. 

The above work concentrated most of its attention on the use of zinc chloride as the molten halide and on the use of bituminous coal extract as feed to the process. Hydrocracking of the extract (1) and regeneration by a fluidized-bed combustion technique of the spent catalyst melt (2) from the process were both demonstrated in continuous bench-scale units. 

The structure of the hydrocarbons produced can be modified by the use of catalyst. Catalytic cracking consumes less energy than the noncatalytic process and results in formation of more branch-chain hydrocarbons. On the other hand the addition of the catalyst can be troublesome, and the catalyst accumulates in the residue or coke. There are two ways to contact the melted polymer and catalysts the polymer and catalyst can be mixed first, then melted, or the molten plastics can be fed continuously over a fluidized catalyst bed. The usually employed catalysts are US-Y, and H-ZSM-5. Catalyst activity and product structure have been reported [7-11]. It was found that the H-ZSM-5 and ECC catalysts provided the best possibility to yield hydrocarbons in the boiling range of gasoline. 

Acrylic acid is a high volume chemical, continuous processing is used. Similar catalysts are used for both reactions, but the catalysts and conditions are sufficiently different that the reactions are conducted separately. Bismuth molybdate and molybdenum vanadium oxides typically are the bases for the catalysts in the first and second reactions, respectively. Effluent from the first reactor can go directly to the second reactor wilfrout processing. Fixed bed, shell-and-tube, solid-catalyst reactors are used for the gas-phase reaction. Reactors are cooled with circulating molten salts. Additional process information is presented as needed. 

Promising results have been reported by various laboratories since 1990 on catalysis in molten salts, notably for catalytic hydrogenation, hydroformylation, oxidation, alkoxycarbonylation, hydrodimerization/telomerization, oligomerization, and Trost-Tsuji coupling [113]. A continuous-flow application to the linear dimerization of 1-butene on an ionic-liquid nickel catalyst system reached activities with TON > 18000 [116]. 

The use of a Supported Liquid Phase Catalyst offers an opportunity for continuous removal of soot from diesel exhaust gas. Molten salt mixtures show a higher activity compared to solid metal oxides. This high activity can be ascribed to a better contact between the liquid catalyst and the soot. The contact between soot and catalyst remains intact during oxidation. 

A stainless-steel stirrer with a paddle cut to conform with the internal radius of the flask is positioned about % inch from the bottom of the flask and agitation is started. The flask is placed in an oil bath at 200°C, agitated for five minutes, and 0.3 ml of catalyst is added. Methanol distillation starts almost immediately, and distillation is practically complete in 20 minutes. The temperature of the oil bath is maintained for one hour after the addition of catalyst. The temperature of the bath is then increased to 260°C during about 30 minutes. The pressure on the system is then reduced to 0.5 mm Hg or less (about 0.1 mm Hg measured with a McLeod gauge at the pump) and distillation at reduced pressure is continued for about 90 minutes. The resulting viscous, molten product is scraped from the flask in a nitrogen (water-and oxygen-free) atmosphere and allowed to cool. 

The N-acetyl-D,L-amino acid precursors are conveniently accessible through either acetylation of D,L-amino acids with acetyl chloride or acetic anhydride in a Schotten-Baumann reaction or via amidocarbonylation I801. For the acylase reaction, Co2+ as metal effector is added to yield an increased operational stability of the enzyme. The unconverted acetyl-D-methionine is racemized by acetic anhydride in alkali, and the racemic acetyl-D,L-methionine is reused. The racemization can also be carried out in a molten bath or by an acetyl amino acid racemase. Product recovery of L-methionine is achieved by crystallization, because L-methionine is much less soluble than the acetyl substrate. The production is carried out in a continuously operated stirred tank reactor. A polyamide ultrafiltration membrane with a cutoff of 10 kDa retains the enzyme, thus decoupling the residence times of catalyst and reactants. L-methionine is produced with an ee > 99.5 % and a yield of 80% with a capacity of > 3001 a-1. At Degussa, several proteinogenic and non-proteinogenic amino acids are produced in the same way e.g. L-alanine, L-phenylalanine, a-amino butyric acid, L-valine, l-norvaline and L-homophenylalanine. 

After decomposition of the aluminum alloys there is still residual aluminum in the metal, and this residue seems to be in part responsible for the activity of the catalyst. If this residue is largely removed by continued extraction, the catalyst becomes inactive.157 Alloys containing more than 75% of nickel are only partly attacked by aqueous sodium hydroxide, or are not attacked at all then decomposition has to be undertaken with very concentrated sodium hydroxide solution or by adding solid sodium hydroxide to the molten mass.158 Alloys containing between 30% and 50% of active metal are most suitable for preparation of active metal catalysts. 

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