Catalyst Rejuvenation Research Articles

Effect of Decoking Pretreatment on Catalyst Rejuvenation Using Glycerol and Mono Ethylene Glycol (MEG)

Hydrotreating process is one of the crucial processes in petroleum refinery to remove sulfur with the aid of catalyst. By the end of hydrotreating life cycle, the catalyst contaminated by silicon cannot be reused or regenerated and have to be sent to final disposal. The previous study reported that glycerol was able to selectively remove silic on from industrial spent catalysts using severe operating conditions. However, the treatment used did not consider carbon/ coke removal steps. The present work focuses on investigating the effect of decoking pretreatment on silicon removal process using glycerol, mono ethylene glycol, and a combination of glycerol + mono ethylene glycol. It was found that the decoking pretreatment will worsen solvent selectivity. In addition, XRD analysis also revealed that decoking pretreatment caused formation of MoO3 particles agglomerate as indicated by the presence of high crystalline. Compared with glycols, glycerol showed the best selectivity and could preserve catalyst phase from transformation that was occurred during decoking.

Review on the Use of Heavy Metal Deposits from Water Treatment Waste towards Catalytic Chemical Syntheses.

The toxicity and persistence of heavy metals has become a serious problem for humans. These heavy metals accumulate mainly in wastewater from various industries’ discharged effluents. The recent trends in research are now focused not only on the removal efficiency of toxic metal particles, but also on their effective reuse as catalysts. This review discusses the types of heavy metals obtained from wastewater and their recovery through commonly practiced physico-chemical pathways. In addition, it covers the advantages of the new system for capturing heavy metals from wastewater, as compared to older conventional technologies. The discussion also includes the various structural aspects of trapping systems and their hypothesized mechanistic approaches to immobilization and further rejuvenation of catalysts. Finally, it concludes with the challenges and future prospects of this research to help protect the ecosystem.

Elucidation of deactivation phenomena in cobalt catalyst for Fischer-Tropsch synthesis using SSITKA

Catalyst deactivation is a major problem in Fischer-Tropsch synthesis. It leads to a decrease in hydrocarbon productivity and loss of active sites in the expensive cobalt catalyst, and thus, undermines the overall efficiency of the technology. In the present paper, the effect of deactivation of silica-supported cobalt catalysts and their reductive rejuvenation on the number of active sites and their intrinsic activity (turnover frequency) in Fischer-Tropsch synthesis was studied using a combination of Steady State Isotopic Transient Kinetic Analysis (SSITKA) and catalyst characterization techniques. Catalyst characterization revealed that carbon deposition and agglomeration of cobalt nanoparticles during reaction were responsible for the deactivation. SSITKA experiments showed that the initial rate constant of 2.33μmolg−1s−1 had a loss of 67% of activity after 150h on stream with a reduction in the amount of sites due to deposited carbon by 33.4μmolg−1. The carbon deposition leads to a decrease in the number of carbon chemisorbed intermediates which yield methane through their hydrogenation and desorption. The number of sites for reversible adsorption of CO is less affected by carbon deposition. The surface hydrogenation sites and surface sites favoring stronger reversible adsorption of carbon monoxide deactivate first during the first hours of Fischer-Tropsch synthesis. Catalyst rejuvenation in hydrogen lessens the amounts of deposited carbon species and partially releases the most active sites of carbon monoxide dissociative adsorption and stronger sites of carbon monoxide reversible adsorption. The transient isotopic methods provide an attractive tool to obtain precise information about the mechanisms of deactivation of cobalt catalysts in Fischer-Tropsch synthesis.

Renewable Hydrogen Production from Bio-oil in an Aerosol Pyrolysis System

Abundant bio-oil resulting from thermochemical conversion of biomass could potentially be an important source of renewable hydrogen (H2). Direct pyrolysis of hardwood bio-oil was carried out in an aerosol reaction system to evaluate temperature and catalytic effects on H2 production. The laboratory system achieved stable H2 output for hours without the need of steam or catalyst rejuvenation. Hydrogen yields (∼50%) are comparable to those from fixed-bed reactors under typical pyrolysis temperatures (700 – 900°C). Pure nickel catalyst enhanced hydrogen yield at lower temperatures (≤ 800°C) but suppressed it at higher temperatures, while an activated charcoal catalyst showed activities only above 800°C. Elemental balance calculations estimate an overall enthalpy of reaction of 2 – 3kJ/g bio-oil, less than 17% of the bio-oil heating value and lower than that of conventional steam-reforming processes. Advantages and future research needs of the aerosol approach for bio-oil/hydrogen conversion are discussed.

Frontiers in Catalysis and Materials Chemistry: The 3rdIDECAT Conference on Catalysis

Frontiers in Catalysis and Materials Chemistry: The 3^rdIDECAT Conference on Catalysis

A preliminary process design and economic assessment of a catalyst rejuvenation process for waste disposal of refinery spent catalysts

Spent hydroprocessing catalysts from refineries have been classified as hazardous solid waste by the United States Environmental Protection Agency (USEPA), refiners must find a viable but economical solution to solve this serious environmental issue. Catalyst rejuvenation is an attractive option for minimizing the environmental problems associated with spent catalysts. In this study, a preliminary design for such a process and the corresponding economic analysis are performed to assess the proposed catalyst rejuvenation process for metal-fouled spent catalysts generated in residue hydroprocessing units. The scenarios used in the economic assessment are based on three options of process synthesis and two operator modes. It is found that the option of rejuvenating medium and lightly fouled spent catalyst produced by the refinery will be the best solution for refiners, both environmentally and economically.

Kinetics of Hydrodesulfurization Catalyst Rejuvenation Process

Kinetics of Hydrodesulfurization Catalyst Rejuvenation Process

Gas conversion using synthesis gas-produced hydrogen for catalyst rejuvenation and hydrocarbon conversion

Gas conversion using synthesis gas-produced hydrogen for catalyst rejuvenation and hydrocarbon conversion

99/03065 Slurry hydrocarbon synthesis process with catalyst rejuvenation in external lift pipe

99/03065 Slurry hydrocarbon synthesis process with catalyst rejuvenation in external lift pipe

In-situ ultrasonic catalyst rejuvenation in three-phase hydrogenation of xylose

Many catalytic, batchwise three-phase hydrogenations are carried out over Raney Ni catalysts, it being an appropriate choice for several reaction systems, such as manufacturing of various fine chemicals, alimentary industry products and petrochemical compounds. One important drawback of Raney catalysts, usually, is its relatively fast deactivation. In this paper, the usefulness of an integrated ultrasonic treatment of the catalyst is demonstrated in the hydrogenation of xylose to xylitol, resulting to a stable catalyst activity. The underlying reason for the stabilizing effect of the applied ultrasonic field is proposed to consist primarily due to the following phenomena: decontamination of the active sites and creation of fresh active sites, caused by the mechanical stress introduced by the ultrasonic field.

95/00223 External catalyst rejuvenation system for the hydrocarbon synthesis process

95/00223 External catalyst rejuvenation system for the hydrocarbon synthesis process

Heavy oil hydrotreating catalyst rejuvenation by leaching of foulant metals with ferric nitrate-organic acid mixed reagents

Much effort has been devoted in recent years to develop processes for the rejuvenation of metal fouled spent catalysts from residue hydroprocessing units. In this paper we report the influence of adding ferric salts to some organic acids in selective extraction of foulant metals from the spent catalyst prior to decoking. Leaching experiments were carried out using two different organic acids, namely, oxalic acid and tartaric acid with and without ferric nitrate addition. The spent and the treated catalysts were characterized and the improvements in surface area, pore volume and HDS activity as a result of leaching with different reagents compared. The studies revealed that in the absence of ferric salts, the acids showed very poor activity for leaching foulant metals from coked spent catalyst. Addition of ferric nitrate enhanced the leaching efficiency of each acid to a different degree. The selectivity for the removal of the major metal foulant (vanadium) was different for different leaching reagents. The enhanced leaching by the ferric nitrate-organic acid system has been explained in terms of a synergistic mechanism involving oxidizing and complexing reactions. The improvements in surface area and pore volume recovery was found to be related to the extent of vanadium removal from the catalyst. The HDS activity of the catalyst also increased significantly by leaching of the deposited metals. The study showed that oxalic acid-ferric nitrate reagent was superior to other reagent systems in terms of selectivity for vanadium leaching as well as for surface area, pore volume and activity recovery.