Attrition hydrogenation

Chelating resins undergo volumetric change by as much as 50% in converting from the hydrogen form to sodium form. This tends to cause attrition of the resin and reduce its life. 

In a continuous reformer, some particulate and dust matter can be generated as the catalyst moves from reactor to reactor and is subject to attrition. However, due to catalyst design little attrition occurs, and the only outlet to the atmosphere is the regeneration vent, which is most often scrubbed with a caustic to prevent emission of hydrochloric acid (this also removes particulate matter). Emissions of carbon monoxide and hydrogen sulfide may occur during regeneration of catalyst. 

STRs in the most recent fine chemical hydrogenations [26]. The L/S slurry is circulated back at high flow in a loop connected to a Venturi. The local underpressure in the neck causes gas to be sucked in the intense turbulence achieves a very large interfacial area between tiny bubbles and the slurry. An external heat exchanger on the loop enables an almost unlimited heat removal, convenient for extremely high exothermic reactions, and isothermal operations. On the other hand, JLRs are restricted to a batch mode and can only accommodate catalysts compatible with the pump (low hard ness, low attrition). 

Powders possessing relatively high surface area and active sites can be intrinsically catalytically active themselves. Powders of nickel, platinum, palladium, and copper chromites find broad use in various hydrogenation reactions, whereas zeolites and metal oxide powders are used primarily for cracking and isomerization. All of the properties important for supported powdered catalysts such as particle size, resistance to attrition, pore size, and surface area are likewise important for unsupported catalysts. Since no additional catalytic species are added, it is difficult to control active site location however, intuitively it is advantageous to maximize the area of active sites within the matrix. This parameter can be influenced by preparative procedures. 

The main disadvantages of the present industrial process are the use of large amounts of ammonia as solvent and the degradation of the Raney nickel catalyst either by attrition or leaching (solubilization in liquid ammonia). Considerable efforts are currently being made to search for efficient and resistant catalysts for the gas phase hydrogenation of adiponitrile with high hexamethylenediamine selectivity. 

DuPont s new tetrahydrofuran plant, which is slated to start up in the second quarter of 1996 in Asturias, Spain, is based on a new process that is claimed to be environmentally friendly [133], The process is harnessed with a circulating fluidized-bed (CFB) reactor for the partial oxidation of n-butane. The catalyst used for this stage is vanadium phosphorus oxide (VPO). To enhance the catalytic life in the CFB reactor, attrition-resistant catalyst particles have been developed. A highly selective catalyst for hydrogenation of maleic acid to THF also has been developed. This THF conversion reaction is carried out in a bubble column reactor under relatively mild conditions. This process has several significances ... 

Demonstrate the "trap grease"-to-hydrogen process in long-duration tests using the attrition-resistant catalysts. An alternative reactor option that uses a circulating bed to prepare 80 pm catalyst particles will also be considered. 

The fluidized bed process performance significantly decreased after 135 hours of uninterrupted operation. This low conversion to hydrogen was most likely due to the catalyst losses by attrition and elutriation from the reactor, though some deactivation effects cannot be excluded at this time. 

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