Waste catalyst

In 1974, Monsanto brought on-stream an improved Hquid-phase AIQ. alkylation process that significantly reduced the AIQ. catalyst used by operating the reactor at a higher temperature (42—44). In this process, the separate heavy catalyst—complex phase previously mentioned was eliminated. Eliminating the catalyst—complex phase increases selectivities and overall yields in addition to lessening the problem of waste catalyst disposal. The ethylben2ene yields exceed 98%. 

Pyrolysis characteristics of polyethylene using waste catalysts... 

In this work, LDPE and HDPE were used as the waste plastics and ZSM-5 and RFCC were used as the waste catalyst. The effects reaction temperature and catalyst concentration on the production of liquid products were investigated in a semi-batch reactor. 

The plastic samples used in this study were palletized to a form of 2.8 3.2min in diameter. The molecular weights of LDPE and HDPE were 196,000 and 416,000, respectively. The waste catalysts used as a fine powder form. The ZSM-5 was used a petroleum refinement process and the RFCC was used in a naphtha cracking process. The BET surface area of ZSM-5 was 239.6 m /g, whose micropore and mesopore areas were 226.2 m /g and 13.4 m /g, respectively. For the RFCC, the BET surface area was 124.5 m /g, and micropore and mesopore areas were 85.6 m /g and 38.89 m /g, respectively. The experimental conditions applied are as follows the amount of reactant and catalyst are 125 g and 1.25-6.25 g, respectively. The flow rate of nitrogen stream is 40 cc/min, and the reaction temperature and heating rate are 300-500 C and 5 C/ min, respectively. Gas products were vented after cooling by condenser to -5 °C. Liquid products were collected in a reservoir over a period of... 

Mercury Recovery Services, Inc. (MRS), has developed the Mercury Removal/Recovery Process (MRRP) to treat media contaminated with mercury. The ex situ process uses medium-temperature thermal desorption to remove the mercury from contaminated wastes. Process wastes are heated in a two-step process to recover metallic mercury in a 99% pure form. MRS claims MRRP can be applied to soils, activated carbon, mixed waste, catalysts, electrical equipment, batteries, lamps, fluorescent bulbs, mercurous and mercuric compounds, mercury-contaminated waste liquids, and debris. 

Gas/gas reaction in which solids are transformed Coal combustion Gasification Incineration of waste Catalyst regeneration... 

Without length grading, the refiner was planning to ship all of the material to reclamation. Application of LDG provided an economical way to recover a high quality product as well as reduce the amount of waste catalyst. 

LDPE was catalytically depolymerized in solution in an autoclave by Scott et al. [47] who observed, as expected, that increasing the temperatnre or decreasing the reaction time resulted in higher liqnid yield. At a plastic waste catalyst ratio of 20 1 and a maximum temperature of 420°C, they reported 52.6% liquid and 47.4% gas yield. The majority of the gas was C3 and C4, the monomer being about 5%. 

Spent Catalyst. Opportunities may exist to reduce the volume of waste catalyst by reusing the catalyst through several hydrogeneration batches however, experts disagree on the final benefit of this. The measurement of this can be made by measuring hydrogeneration efficiency versus catalyst disposal costs. Other catalysts have been explored however, their costs and effectiveness are less desirable. These catalysts have environmental problems of their own because they are heavy metal-based. 

Hazards None Spent adsorber is hazardous waste Catalyst is priority pollutant and requires special activation... 

Following the successful application of zeolites in the major oil refining processes, zeolites entered the field of bulk chemicals synthesis, e.g. ethylbenzene, cumene and recently caprolactam. Their applications in the areas of fine chemicals arc also growing. An important factor is that zeolites, compared to conventional Brocnsted and Lewis acid catalysts, are low-waste catalysts and are regarded as green . After the early review on zeolite-catalyzed organic reactions by Venuto and Landis [ 1J the field has been reviewed several times [2-11],... 

For large pellets, it lakes a long time for the reactant A to diffu.se into interior compared to the time it takes for the reaction to occur on the inter pore surface. Under these circumstances, the reactant is only consumed n the exterior surface of the pellet and the catalyst near the center of the pcile wasted catalyst. On the other hand, for very small pellets it takes very It time to diffuse into and out of the pellet interior and. as a result, internal c fusion no longer limits the rate of reaction. The rate of reaction can expressed as... 

A large number of key industrial processes in oil refinery, petrochemistry, and chemistry are acid-catalyzed. Despite the large use of AlClj, there is an evident evolution to greener solid acid catalysts. The reasons for this evolution are a combination of economic and environmental factors. Indeed, the use ofAICI3 results in a high level of waste catalyst streams, the inability to recycle used catalyst, and the economic impact of treatment of waste catalyst streams associated with a negative environmental image. 

Waste catalyst—especially with low residual vanadium pentoxide content. 

Nowadays, in order to alleviate the shortage of domestic resources and improve the environmental condition, many countries in the world p>ay much attention to the comprehensive utilization of the secondary resources. In Jap>an, recycling of the waste catalysts has been done since 1950s the turnover of waste catalysts was already up to 500 million dollars in 19%. 

While the aluminium chloride catalyst enables the reaction to be carried out at 80-100 C temperature, there are inherent problems with this catalyst such as, complex formation with polyisopropylated products, short catalyst life, require large amount of catalyst, it is not recycled, problem in disposing the waste catalyst complex, and polluting problems. 

The spent and discharged catalyst from converter in ammonia plant is called as waste catalyst. The waste catalyst is mainly composed of 65% 80% of metallic iron, 10%-20% of iron oxide and 8%-10% of promoter oxides such as AI2O3, K2O, CaO, CoO etc. At present, they are generally abandoned or are interred in the scrapheap. This is not only a waste of resources, but also leads to environmental pollution, especially for the catalyst containing precious metals such as cobalt which has great recycling value. Example, the content of CoO and promoters in Fe-Co catalysts is illustrated in Table 4.13. 

Technically, it is difficult to recover a single component in the waste catalyst and the total amount of waste catalyst is limited. It may not be rational in an economic sense. Probably, it is the best way to recycle the catalyst as a whole and then use the recycled catalysts for production of a fresh catalyst, so that all the components of waste catalyst can be used effectively. However, it is not an easy thing to transform the waste catalyst to new catalyst because the main component of the waste catalyst is metallic iron (Fe) with the content of more than 70% while the iron in the new catalyst should be iron oxide. Therefore, the metallic iron should be first transformed into iron oxide. The method for the transformation is varied according to the required state of iron oxide in the fresh catalyst. 

The iron oxide in the novel Fei xO-based catalyst is Fei xO. In order to transform the metallic iron in the waste catalyst into Fei xO, the following chemical reaction can be adopted ... 

That is, the 70%-80% of metallic iron of the waste catalyst can be used as a reducing agent for the reduction of magnetite to FeO, and Fej xO-based catalysts can be obtained. At the same time, all the promoters such as AI2O3, K2O, CaO, CoO, etc in the waste catalyst enter into the fresh catalyst (the amount of promoters in fresh catalyst should include that from the waste catalyst), so that all of the components of the waste catalyst are utihzed effectively. Based on this idea, the... 

In plants without a methanation process, such as small and medium-scale plants, there is no Ni catalyst serving as a protection for the Fe catalyst, the latter is under the threat of sulfur. As a result, sulfur is the main reason for the deactivation of catalyst in these plants. Table 8.31 shows the measurements of organic sulfur for several plants. The sulfur content in the fresh syngas is 0.29-0.88g-m (standard). The shortest life of the catalysts is only 41 days, the longest only 264 days (Table 8.32), which are fully expected. The average sulfur content found in the waste catalysts... 

---