Spent Refinery Catalyst Research Articles

Recovery of vanadium from spent refinery catalysts: optimizing the process and analyzing the environmental impact

Recovery of vanadium from spent refinery catalysts: optimizing the process and analyzing the environmental impact

Optimization of thermal pre-treatment for simultaneous and efficient release of both Co and Mo from used Co[sbnd]Mo catalyst by bioleaching and their mechanisms

There are a number of attempts to release and recover the valuable metals from spent refinery catalysts by bioleaching, and the heat pretreatment is widely used to remove the oil-like compounds for better bioleaching performance. However, the irrational selection of high calcinations temperature of 600–800 °C not only resulted in high energy consumption but also might be cause lower bioleaching efficiencies of metals. In this work, Plackett-Burman design was used to optimize the heat treatment process and recognize the significant control factor. Especially, the mechanisms why low calcinations temperature of 400 °C had the best enhancement on the bioleaching performance of spent catalyst were expounded via microcosmic phase change analysis, biochemical leaching process analysis and bioleaching kinetics analysis. The results showed that the calcinations temperature greatly affected the bioleaching performance and the calcinations of 400 °C witnessed the maximum release efficiencies of 94% for Co and 100% for Mo, respectively; whereas poor bioleaching occurred with 200 or 600 °C. Further studies demonstrated the 400 °C-treatment removed the toxic oil-like compounds, excited the growth of cells, transformed refractory Co/Mo sulfides into tractable Co3O4/MoO3, reduced the percent of residual from, enabled more exposure of Co/Mo oxides at catalyst surface, which caused the best bioleaching performance.

Saudi Arabia attracts $2 billion in projects

Several companies have signed tentative deals with the Saudi Arabian General Investment Authority that could lead to $2 billion in chemical investments. Mitsui & Co. is eyeing construction of an ammonia plant, and the water treatment–chemical maker SNF is considering a polyacrylamide plant. Shell plans a recycling facility that will upgrade spent refinery catalysts from around the region. And BASF signed a deal broadly aimed at “evaluating and assessing opportunities.” Saudi Arabia is trying to diversify its economy away from oil and gas exploration.

Investigation of platinum recovery from a spent refinery catalyst with a hybrid of oxalic acid produced by Aspergillus niger and mineral acids

The capability of oxalic acid produced by Aspergillus niger was investigated for bioleaching of platinum from a refinery reforming catalyst. The spent medium mode was selected for bioleaching because of its higher efficiency at favorable pH and temperature conditions. The effects of several important factors such as the pulp density, pH and temperature on platinum recovery were optimized using Box-Behnken design of response surface methodology. The results indicated that pH adjustment during the bioleaching process increases the final platinum recovery significantly. The obtained optimum conditions were 1% for the pulp density, 0.5 for the medium pH, and 70 °C for the temperature which led to 37% platinum recovery. The significance of oxalic acid as the leaching agent in platinum bioleaching was highlighted by investigating the recovery of a blank medium without oxalic acid at the optimum conditions which was just about 13%. The presented method can be utilized in an environmentally friendly process to recover platinum from industrial catalysts.

Chemical and petrochemical industry

Abstract The potential sources of various metals in chemical and petrochemical processes are discussed. Special emphasis is put on the catalysts used in the industry. Their main applications, compositions, especially metal contents are presented both for fresh and spent ones. The focus is on the main types of metals used in catalysts: the platinum-group metals, the rare-earth elements, and the variety of transition metals. The analysis suggested that chemical and petrochemical sectors can be considered as the secondary source of metals. Because the utilization of spent refinery catalysts for metal recovery is potentially viable, different methods were applied. The conventional approaches used in metal reclamation as hydrometallurgy and pyrometallurgy, as well as new methods include bioleaching, were described. Some industrial solutions for metal recovery from spent solution were also presented.

A Bioleaching Regeneration and Recovery of Spent Refinery Catalyst Using Adapted Microorganisms

The regeneration of spent catalyst is either through chemical leaching or bioleaching techniques; with the latter being an alternative to the traditional extraction methods involving the use of series of adapted microorganisms. The bioleaching process is therefore the best alternative due to cost effectiveness, simple in operation and higher recovery of heavy metals. This research work adapted various microorganisms (three bacteria and one fungus) both singly and in mixture into a digested solution of a spent refinery catalyst. The activity order of the adapted microorganisms was described in this order; Pseudomonas flourescens>Bacillus coagulans>Bacillus megaterium or Pseudomonas putida>Fusarium flocciferum. The Pb-ion showed a greater resistance to bioleaching while Mn ion was easily bioleached by the adapted microorganisms. From the results obtained, the affinity of some of these cultured microorganism strains to the heavy metals was attained with Fusarium flocciferum showing affinity for Mn only, Bacillus megaterium or Pseudomonas putida for Mn and Cd-ions, Bacillus coagulans for Pb and partially for Ni- ion, while Pseudomonas flourescens for Pb and Cd-ions. Hence the adaptation of various microorganisms into a digested solution of a spent refinery catalyst already poisoned with the heavy metals is explicitly carried out to regenerate the catalyst for a possible reuse which is optimal in saving the cost of production.

Optimization of two-step bioleaching of spent petroleum refinery catalyst by Acidithiobacillus thiooxidans using response surface methodology

A central composite design (CCD) combined with response surface methodology (RSM) was employed for maximizing bioleaching yields of metals (Al, Mo, Ni, and V) from as-received spent refinery catalyst using Acidithiobacillus thiooxidans. Three independent variables, namely initial pH, sulfur concentration, and pulp density were investigated. The pH was found to be the most influential parameter with leaching yields of metals varying inversely with pH. Analysis of variance (ANOVA) of the quadratic model indicated that the predicted values were in good agreement with experimental data. Under optimized conditions of 1.0% pulp density, 1.5% sulfur and pH 1.5, about 93% Ni, 44% Al, 34% Mo, and 94% V was leached from the spent refinery catalyst. Among all the metals, V had the highest maximum rate of leaching (Vmax) according to the Michaelis–Menten equation. The results of the study suggested that two-step bioleaching is efficient in leaching of metals from spent refinery catalyst. Moreover, the process can be conducted with as received spent refinery catalyst, thus making the process cost effective for large-scale applications.

Sequential leaching of metals from spent refinery catalyst in bioleaching–bioleaching and bioleaching–chemical leaching reactor: Comparative study

The effect of sequential leaching such as bioleaching followed by bioleaching and bioleaching followed by chemical leaching is aimed at enhancing metal (Mo, Ni, V and Al) dissolution from a differently pretreated (acetone washed/decoked) spent catalyst. The X-ray photoelectron spectroscopy characterization of spent catalyst samples suggested the presence of metals in their oxide and sulfide forms. Bioleaching followed by bioleaching with either Acidithiobacillus thiooxidans (Ni-100%, Al-55%, Mo-81% and V-100%) or Acidithiobacillus ferrooxidans (Ni-94%, Al-55%, Mo-77% and V-99%) significantly enhanced removal of Al, Ni, and V from acetone washed (AS) spent catalyst compared to decoked spent catalyst (RS). In contrast, bioleaching using either A. thiooxidans or A. ferrooxidans followed by alkali leaching remarkably enhanced removal of Mo from both AS and RS, although higher yields were achieved using AS. Bioleaching using A. thiooxidans followed by alkaline leaching is an optimum strategy yielding a maximum of 96% Mo in 125h from AS. A field emission scanning electron microscopic study revealed only minor stretches of Mo in the treated AS.

Platinum and rhenium extraction from a spent refinery catalyst using Bacillus megaterium as a cyanogenic bacterium: Statistical modeling and process optimization

The present study evaluated the potential of Bacillus megaterium as a cyanogenic bacterium to produce cyanide for solubilization of platinum and rhenium from a spent refinery catalyst. Response surface methodology was applied to study the effects and interaction between two main effective parameters including initial glycine concentration and pulp density. Maximum Pt and Re recovery was obtained 15.7% and 98%, respectively, under optimum conditions of 12.8g/l initial glycine concentration and 4% (w/v) pulp density after 7days. Increasing the free cyanide concentration to 3.6mg/l, varying the pH from 6.7 to 9, and increasing the dissolved oxygen from 2 to 5mg/l demonstrated the growth characteristics of B. megaterium during bioleaching process. The modified shrinking core model was used to determine the rate limiting step of the process. It was found that diffusion through the product layer is the rate controlling step.

Effects of key parameters in recycling of metals from petroleum refinery waste catalysts in bioleaching process

Environmental laws concerning spent catalysts disposal have become increasingly more severe in recent years. Due to the toxic nature of spent catalysts, their disposal can pollute the environment. The recovery of heavy metals decreases the environmental impact of the waste catalysts and the recycled product can be further used for industrial purposes. Bio-hydrometallurgical approaches, such as bioleaching, appear to offer good prospects for recovering valuable metals from spent refinery catalysts. Currently, identifying and modifying the parameters that influenced the efficiency of bioleaching is important for industrial sector. The biological system can be further improved through optimizing the bioleaching parameters, such as the nutrient culture media, amount of oxygen and carbon dioxide, pH, temperature, inoculum, metal resistance of microorganisms, chemistry of solid waste, particle size of solid waste, solid liquid ratio, bioleaching period, size of substrate, shaking speed, and also the development of more effective bioleaching microorganisms. In our previous review (Asghari et al. in J Ind Eng Chem 19:1069–1081, 2013), information available in the literature on the bioleaching fundamentals of spent catalysts with a focus on recent developments was reviewed in detail. In this study, the effects of most important factors that influence an efficient bioleaching process of spent refinery catalysts with the hope that these valuable and useful data can help determine the most efficient process will be discussed. The details of metals recovery with a focus on the effects of different variables in the bioleaching such as reaction time, pulp density, initial pH, particle size, nutrient concentration, temperature and buffer will also be presented.

An environmentally friendly process for the recovery of valuable metals from spent refinery catalysts

The present study dealt with the whole valorization process of exhaust refinery catalysts, including metal extraction by ferric iron leaching and metal recovery by precipitation with sodium hydroxide. In the leaching operation the effects on metal recovery of the concentration and kind of acid, the concentration of catalyst and iron (III) were determined. The best operating conditions were 0.05 mol L(-1) sulfuric acid, 40 g L(-1) iron (III), 10% catalyst concentration; almost complete extraction of nickel and vanadium, and 50%extraction efficiency of aluminium and less than 20% for molybdenum. Sequential precipitation on the leach liquor showed that it was not possible to separate metals through such an approach and a recovery operation by means of a single-stage precipitation at pH 6.5 would simplify the procedures and give a product with an average content of iron (68%), aluminium (13%), vanadium (11%), nickel (6%) and molybdenum (1%) which would be potentially of interest in the iron alloy market. The environmental sustainability of the process was also assessed by means of life cycle assessment and yielded an estimate that the highest impact was in the category of global warming potential with 0.42 kg carbon dioxide per kg recovered metal.

Selective precipitation of metals from synthetic spent refinery catalyst leach liquor with biogenic H2S produced in a lactate-fed anaerobic baffled reactor

This work evaluated the feasibility of using biogenic H2S and NaOH to selectively precipitate molybdenum (Mo), nickel (Ni), cobalt (Co) and vanadium (V) from synthetic spent refinery catalyst leach liquor. A lactate-fed sulfate-reducing anaerobic baffled reactor (ABR) was operated at room temperature to generate the required H2S. The average sulfate reduction rate in the ABR was 130mgL−1d−1 and the average dissolved sulfide concentration was 190mgL−1. Biogenic H2S facilitated the selective precipitation of Mo at pH2 with recoveries of 36–72%. Vanadium precipitation of 64–70% was achieved with NaOH at pH6. The purity indices of Mo and V precipitates were 0.97 and 0.90 at pH2 and pH6, respectively. Percent Ni and Co precipitations were only up to 23 and 16%, respectively at pH3.5, and the purity indices of these metals were low due to their simultaneous precipitation. After the optimization of the Ni and Co precipitations, the mixed Ni–Co sulfide solids could be sold to smelters or hydrometallurgical processing to recover the metals. Moreover, using biogenic H2S to selectively precipitate Mo at pH2 as sulfide and NaOH to precipitate V at pH6 as hydroxide/oxide could be a viable option for recovering these metals from spent catalysts leachate.

A novel sequential process of bioleaching and chemical leaching for dissolving Ni, V, and Mo from spent petroleum refinery catalyst

Two step leaching experiments were carried out to extract nickel, vanadium, and molybdenum present in spent refinery catalyst. A bioleaching process was applied in the first step. Pulp density, initial Fe(II) concentration, initial pH, particle size, and temperature were varied to optimize the bioleaching process. Ni, V, and Mo were leached out with maximum recoveries of 97%, 92% and 53%, respectively, at an optimized bioleaching condition of initial ferrous ion of 2g/L, initial pH of 2, pulp density of 10% (w/v), particle size of (−106+45) μm, and a temperature of 35°C. As the Mo leaching rate was very low, a second leaching step for the bioleached residue was applied with different concentrations of (NH4)2CO3, Na2CO3, or H2SO4. The second step leaching was optimum at a concentration of 30g/L (NH4)2CO3 with respect to Mo extraction. The rate of Mo dissolution with respect to concentration of lixiviant in the second leaching step was evaluated. The percentages of Ni, V, and Mo leached were 97%, 97% and 99%, respectively, by combining the first step under optimized conditions and the second step with 30g/L (NH4)2CO3.

Bioleaching kinetics of a spent refinery catalyst using Aspergillus niger at optimal conditions

The kinetics of bioleaching of Mo, Ni, and Al from spent hydrocracking catalyst, using Aspergillus niger was studied. The four most effective bioleaching variables were selected in accordance with the Plackett–Burman design and were further optimized via central composite design (CCD). The optimal values of the variables for maximum multi-metal bioleaching were as follows: particle size 150–212μm, sucrose 93.8g/L, pulp density 3%w/v, and pH 7. The maximum metal recoveries corresponding to these conditions were 99.5±0.4% Mo, 45.8±1.2% Ni, and 13.9±0.1% Al. The relatively low Ni extraction was attributed to the precipitation of Ni in the presence of oxalic acid. Under the optimal conditions, the fungus growth was found to be higher in the presence of spent catalyst than that in the catalyst-free medium. Determinations of the organic acid concentration showed noticeable variation during bioleaching, particularly for gluconic acid. Accordingly, a modified form of shrinking core model was used to take these variations into account. The predictions by the model showed good consistency with the experimental results, suggesting that diffusion of bioleaching agent through the solid matrix was the rate-controlling step.

Assessment of biotechnological strategies for the valorization of metal bearing wastes

The present work deals with the application of biotechnology for the mobilization of metals from different solid wastes: end of life industrial catalysts, heavy metal contaminated marine sediments and fluorescent powders coming from a cathode ray tube glass recycling process. Performed experiments were aimed at assessing the performance of acidophilic chemoautotrophic Fe/S-oxidizing bacteria for such different solid matrices, also focusing on the effect of solid concentration and of different substrata. The achieved results have evidenced that metal solubilization seems to be strongly influenced by the metal speciation and partitioning in the solid matrix. No biological effect was observed for Ni, Zn, As, Cr mobilization from marine sediments (34%, 44%, 15%, 10% yields, respectively) due to metal partitioning. On the other hand, for spent refinery catalysts (Ni, V, Mo extractions of 83%, 90% and 40%, respectively) and fluorescent powders (Zn and Y extraction of 55% and 70%, respectively), the improvement in metal extraction observed in the presence of a microbial activity confirms the key role of Fe/S oxidizing bacteria and ferrous iron. A negative effect of solid concentration was in general observed on bioleaching performances, due to the toxicity of dissolved metals and/or to the solid organic component.

Process optimization and modeling of heavy metals extraction from a molybdenum rich spent catalyst by Aspergillus niger using response surface methodology

The present study examines the biorecovery of heavy metals from a spent refinery catalyst obtained from one of the oil refineries in Iran using Aspergillus niger. Bioleaching experiments were carried out in batch cultures using A. niger in the one-step process to mobilize Co, Mo and Ni from hazardous spent catalysts. Response surface methodology (RSM) was applied for the design and analysis of experiments with the optimization of pH, temperature, inoculum percentage, pulp density and rotation speed during the bioleaching of the metals. Experiments were designed as per the central composite design (CCD) technique. Three cubic mathematical models were derived for prediction of the responses. In process optimization, maximal values of Co, Mo and Ni recoveries were achieved as 71%, 69% and 46%, respectively, with a pH of 5.0, a temperature of 31 °C, a pulp density of 2 g/L, a rotation speed of 115 rpm, and using a 12% inoculum.

탈황(脫黃) 폐촉매(廢觸媒)로부터 유가금속(有價金屬) 추출(抽出)

황산으로 탈황 폐촉매를 침출한 결과 황산농도 1 M, 반응시간 1 hr인 실험조건에서 Ni 및 V은 95% 이상, 그리고 Mo은 30%가 침출되었다. 탈황 폐촉매의 Mo matrix 특성으로 인하여 다른 금속에 비하여 Mo의 침출율이 낮았으며, 본 침출반응은 확산반응에 의하여 제어되는 것으로 판단된다. Mo을 완전히 침출하기 위하여 유황성분이 제거된 폐촉매로 침출실험을 실시하였다. 1M 황산으로 처리후 탄산나트륨으로 세척시 Ni, Mo 그리고 V의 침출율은 99% 이었다. Ni 2 g/L; V 9 g/L, Mo 0.6 g/L 조성의 침출액을 LIX 841로 용매추출한 조건에서 A:O 비 5:2, 2단계로 처리시 Mo은 98% 이상 추출되었으며 A:O 비 5:3, 2단계로 처리시 V은 82%가 추출되었다. Sulphuric acid leaching was conducted to extract the metal values from spent refinery catalyst. More than 95% of Ni and V and 30% of Mo could be leached out in 1 M sulphuric acid and 1 hr of leaching time. The decrease in Mo leaching was due to typical characteristic of Mo matrix. The activation energies of the leaching reactions showed the dissolution process follows a diffusion control mechanism. In order to leach out all Mo, further the leaching experiments were conducted with sulfur free spent refinery catalyst. For sulfur free spent refinery catalyst, a two step process of leaching with 1 M sulphuric acid followed by sodium carbonate washing showed better leaching than a two step leaching process with sodium carbonate followed by sulphuric acid washing, with almost 99% leaching of Ni, Mo and V. Solvent extraction using LIX 841 were conducted for a leach liquor containing Ni, 2 g/L; V, 9 g/L, Mo, 0.6 g/L. More than 98% of Mo was extracted from the leach liquor at A:O ratio of 5:2 in a 2 stage process. Similarly V was extracted at A:O ratio of 5:3 in a 2 stage process with 82% of total V extraction.

Enhancement of metals dissolution from spent refinery catalysts using adapted bacteria culture — Effects of pH and Fe(II)

Leaching studies of Ni, V, Mo and Al from spent refinery catalysts were conducted using both adapted and unadapted bacterial cultures. The effects of variations in leaching parameters such as pH and Fe(II) concentration on the leaching rate of both bacterial cultures were evaluated. The leaching kinetics was characterized by an initial faster rate followed by a slower rate, which corresponded to surface and pore diffusion model, respectively. Additionally, the leaching efficiencies of Ni and V were found to be ~ 95% and ~ 85% in the case of adapted and unadapted bacteria cultures, respectively. The lower leaching rate of Mo than Ni and V was due to the mutual effects of the hydrophobic sulfur layer over the molybdenum matrix and refractory nature. The leaching rates increased as the pH increased from 1.5 to 2.0, then decreased at pH 3.0 for all metals. The variation in the concentration of Fe(II) supplement also had a substantial effect on the leaching rates. The dissolution of all metals followed first order reaction kinetics; therefore, unified dissolution rate equations were developed using the first order rate equation for different parameters. The pore diffusion mechanism was found to be the rate determining step.

Metal recovery from spent refinery catalysts by means of biotechnological strategies

A bioleaching study aimed at recovering metals from hazardous spent hydroprocessing catalysts was carried out. The exhaust catalyst was rich in nickel (4.5 mg/g), vanadium (9.4 mg/g) and molybdenum (4.4 mg/g). Involved microorganisms were iron/sulphur oxidizing bacteria. Investigated factors were elemental sulphur addition, ferrous iron addition and actions contrasting a possible metal toxicity (either adding powdered activated charcoal or simulating a cross current process by means of periodical filtration). Ferrous iron resulted to be essential for metal extraction: nickel and vanadium extraction yields were 83% and 90%, respectively, while about 50% with no iron. The observed values for molybdenum extraction yields were not as high as Ni and V ones (the highest values were around 30-40%). The investigated actions aimed at contrasting a possible metal toxicity resulted not to be effective; in contrast, sequential filtration of the liquor leach had a significant negative effect on metals extraction. Nickel and vanadium dissolution kinetics resulted to be significantly faster than molybdenum dissolution ones. Furthermore, a simple first order kinetic model was successfully fitted to experimental data. All the observed results supported the important role of the indirect mechanism in bioleaching of LC-Finer catalysts.

Bioleaching of Nickel, Vanadium and Molybdenum from Spent Refinery Catalysts

Spent catalysts represent a large amount of refinery solid waste. In particular, hydro-processing catalysts contain base valuable metals, such as nickel, vanadium and molybdenum and, for their toxic component, these wastes have been classified as hazardous by the Environmental Protection Agency in the USA. The development of an innovative eco-sustainable process for the valorisation of such wastes would undoubtedly give significant advantages also taking into account primary resources preservation. This paper deals with bioleaching of metals from hazardous spent hydro-processing catalyst by means of iron/sulphur oxidizing bacteria. The exhaust catalyst was rich in nickel (45 mg/g), vanadium (44 mg/g) and molybdenum (94 mg/g). Before bioleaching, the solid was washed by means of a mixture of Tween 80 and ethyl alcohol, for hydrocarbon removal. The effects of elemental sulphur, ferrous iron and actions contrasting a possible metal toxicity (either the presence of powdered activated charcoal or the simulation of a cross current process by means of filtration stages in series) was investigated. Ferrous iron resulted to be essential for metal extraction and for bacteria adaptation. Nickel and vanadium were successfully bioleached in the presence of iron, reaching extraction yields of 83% and 90%, respectively; on the other hand extractions around 50% for nickel and vanadium were observed both in biological systems in the absence of iron and in the chemical controls with iron. As concerns molybdenum, the highest extraction yields experimentally observed was about 50%, after 26 days bioleaching in the presence of iron, while a maximum extraction of 25 % was observed in the other treatments. In conclusion, a bio-oxidative attack with iron could successfully extract nickel, vanadium and partially molybdenum. Further actions aimed at contrasting a possible metal toxicity resulted not to be effective.