Methods for recovering spent fluidized bed cracking catalyst to sustainable products

Abstract

Disclosed herein includes methods for recovering chemical constituents from a spent catalyst comprising the chemical constituents. The methods may involve one or more of the following steps, such as treating the spent catalyst with an acid to form a first leachate and a first residue, wherein the first leachate comprises a rare earth metal and aluminum, and wherein the first residue comprises silicon and aluminum; treating the first residue with a base to form a second leachate and a second residue, wherein the second leachate comprises silicon, and wherein the second residue comprises mullite; treating the second leachate with gaseous carbon dioxide to form a carbonate- containing base and silicon dioxide; and recycling the carbonate-containing base to mix with the first leachate to form a third residue and a third leachate, wherein the third residue comprises NaLa(SO4)2. In certain non-limiting embodiments, the methods may involve one or more of the following steps, such as treating the first leachate with a sodium salt to form a second residue comprising the rare earth metal; treating the first residue with a base to form a second leachate and a second residue, wherein the second leachate comprises silicon, and wherein the second residue comprises mullite; treating the second leachate with gaseous carbon dioxide to form a carbonate-containing base and silicon dioxide; mixing the sodium salt, after treating the first leachate with the sodium salt, with the base to form carbon dioxide and an alumina-containing residue; and recycling the carbon dioxide as the gaseous carbon dioxide for treating the second leachate to form the carbonate-containing base and the silicon dioxide.

Description

METHODS FOR RECOVERING SPENT FLUIDIZED BED CRACKINGCATALYST TO SUSTAINABLE PRODUCTSTechnical Field

[0001] The present disclosure relates to a method for recovering chemical constituents from a spent catalyst containing the chemical constituents.Background

[0002] Several tons of spent fluidized bed cracking catalyst (SFCC) were consumed for the oil refining industry, which generated spent fluid catalytic cracking as waste for landfilling. In general, the SFCC tends to be contaminated by heavy metals, rare earth elements and a considerable portion of silica alumina. Solid disposal in landfill seems to be the main choice for SFCC, but this may subsequently cause environmental risks and dilemma for space of disposal in the long term. The minimum portion of waste may be used as additive for replacement of sand in cement but tends to be undesirably limited to 20% only. The excess use of additive may alter chemical and mechanical properties of cement and mortar- powder, hence direct application of SFCC may have been limited in any industrial process. Undesirably, waste dumping creates a non-productive use of land resources, leaching of metal / heavy metals in groundwater supplies and handling of waste segregation charges. Existing industrial processes for synthesis of silica and mullite depend on thermal treatments of quartz silica and clays at 1200°C to 1400°C, which may be mainly responsible for high CO2 emission to the atmosphere. There may have been attempts made by researchers to recover value-added products from SFCC but the attempts may have limitation in terms of not being able to produce zero waste, not CO2 neutral, and neither cost-effective process nor sustainable.

[0003] There is thus a need to provide for a solution that ameliorates one or more of the limitations mentioned above. The solution should at least provide for recovery of chemical constituents of the spent fluidized bed cracking catalyst, which include at least rare earth elements.Summary

[0004] In a first aspect, there is provided for a method for recovering chemical constituents from a spent catalyst comprising the chemical constituents, the method comprising: treating the spent catalyst with an acid to form a first leachate and a first residue, wherein the first leachate comprises a rare earth metal and aluminum, and wherein the first residue comprises silicon and aluminum; treating the first residue with a base to form a second leachate and a second residue, wherein the second leachate comprises silicon, and wherein the second residue comprises mullite; treating the second leachate with gaseous carbon dioxide to form a carbonate - containing base and silicon dioxide; and recycling the carbonate-containing base to mix with the first leachate to form a third residue and a third leachate, wherein the third residue comprises NaLafSOfh.

[0005] In a second aspect, there is provided a method for recovering chemical constituents from a spent catalyst comprising the chemical constituents, the method comprising: treating the spent catalyst with an acid to form a first leachate and a first residue, wherein the first leachate comprises a rare earth metal and aluminum, and wherein the first residue comprises silicon and aluminum; treating the first leachate with a sodium salt to form a second residue comprising the rare earth metal; treating the first residue with a base to form a second leachate and a second residue, wherein the second leachate comprises silicon, and wherein the second residue comprises mullite; treating the second leachate with gaseous carbon dioxide to form a carbonate- containing base and silicon dioxide; mixing the sodium salt, after treating the first leachate with the sodium salt, with the base, to form carbon dioxide and an alumina-containing residue; and recycling the carbon dioxide as the gaseous carbon dioxide for treating the second leachate to form the carbonate-containing base and the silicon dioxide.Brief Description of the Drawings

[0006] The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present disclosure arc described with reference to the following drawings, in which:

[0007] FIG. 1 is a table that shows screening of SFCC at kg scale and lab scale.

[0008] FIG. 2A is a flow diagram showing the pH (or written as PH) dependency and process steps in methods of the present disclosure configured for the extraction of NaLafSCrih, alumina and La / Silica:Alumina. The use of a base solution after recovery of silica as an additive with different PHto recover sodium lanthanum sulphate and alumina. This clearly improves the process efficiency and steps.

[0009] FIG. 2B shows the use of base leachate to recover NaLa(SO4)2 and Alumina.

[0010] FIG. 3 is a table showing for the XRF (x-ray fluorescence) study of the recovered samples.

[0011] FIG. 4 is a SEM (scanning electron microscopy) of NaLa(SO )2 recovered using base leachate (PH2-4).

[0012] FIG. 5 shows XRD (x-ray diffraction) study of silica alumina and alumina product.

[0013] FIG. 6 is a process flow diagram (PFD) for PHdependent synthesis of NaLa / SCrih and alumina and heat recovery. TEA (techno-economic analysis) have been calculated for processing of 12,500 SFCC / year for recovery to value added products. Process step modification and Heat Recover}'. 90% water recover '. Remove PREC1P1, retain sizing of R4. Adjust filter efficiency to 30% moisture in solid (able to recover 507.408 kW from steam).

[0014] FIG. 7A shows technoeconomic analysis (TEA) Results (Total Capital Investment - TCI). Total Capital Investment (TCI): S$27,133,100. Depreciation: 20 years. TCI per tonne FCC: S$72.89. Scale: 12,500 tonne / year (37.5 tonnes / day).

[0015]

[0016] FIG. 7B shows TEA result (OpEx). OpEx before Revenue: S$8,500,831 per year (S$680.07 / t FCC). Total Revenue: S$10,433,925 per year (S$834.71 / t FCC). Profit after Revenue: S$l,933,094 per year (S$ 154.65 / t FCC). FCC Processed: 12,500 tonne / year (37.5 tonnes / day).

[0017] FIG. 7C shows TEA results (revenue).

[0018] FIG. 7D shows Energy Analysis. FCC Processed: 12,000 tonne / year (37.5 tonnes / day)

[0019] FIG. 7E shows overall summary.

[0020] FIG. 8 is Process flow diagram (PFD) for process step modification and heat recovery. Remove R3 filter dryer system, remove alumina filter dryer system. Remaining R4, 1 filter and 1 dryer to produce Lanthanum / Silica Alumina product. Price is set at $1050 / tonne (reference zeolite catalysts). Energy consumption remains the same. TCI will change, OpEx expected to change slightly for maintenance and minor electricity.

[0021] FIG. 9A shows TEA Results (TCI). Total Capital Investment (TCI): S$23,034,300. Depreciation: 20 years. TCI per tonne FCC: S$61.42. Scale: 12,500 tonne / year (37.5 tonnes / day).

[0022] FIG. 9B shows TEA result (OpEx). OpEx before Revenue: S$8,206,566 per year (S$656.53 / t FCC). Total Revenue: S$12,190,225 per year (S$975.22 / t FCC). Profit after Revenue: S$3,983,659 per year (S$318.69 / t FCC). FCC Processed: 12,500 tonne / year (37.5 tonnes / day).

[0023] FIG. 9C TEA Results (Revenue). Total Revenue: S$12, 190,225 per year.

[0024] FIG. 9D shows New Production Rate.

[0025] FIG. 9E Energy Analysis. FCC Processed: 12,000 tonne / year (37.5 tonnes / day).

[0026] FIG. 9F shows overall summary.

[0027] FIG. 10 shows the products recovery rate, yields and purity of a method of the present disclosure.

[0028] FIG. 11 shows results of screening of acid and base leaching for SFCC to value added products.

[0029] FIG. 12A shows the XRD study of the obtained solids.

[0030] FIG. 12B shows the XRD study of the obtained solids.

[0031] FIG. 13 shows XRF results of metal oxides of recovered samples.

[0032] FIG. 14 shows SEM study of the obtained solids.

[0033] FIG. 15 shows BET surface area study of the obtained solids.

[0034] FIG. 16 shows photographs of spent SFCC and recovered products using methods of the present disclosure. The recovered products shown include silica, NaLa / SOr salt, mullite. Also shown are the “acid leachate” (containing lanthanum) and carbonatc-containing base. The kg scale products arc ready for the third-party analysis and validation.

[0035] FIG. 17 shows the process loop for the recycling of solids from SFCC.Detailed Description

[0036] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practised. These embodiments arc described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0037] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that arc described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0038] The present disclosure relates to methods for recovering chemical constituents from a spent catalyst comprising the chemical constituents. The methods may be carried out independently, separately, simultaneously, or in any combination (e.g., sequentially). For example, in a sequential operation, any component (e.g., starting material or intermediate product) or product generated in one method may be channeled for use in the other method.

[0039] The chemical constituents may include rare earth elements, silicon-containing constituents, aluminum-containing constituents, and / or mullite. Said differently, methods of the present disclosure is advantageous in that the method is able to recovervarious chemical constituents of a spent catalyst after the catalyst has been used, wherein the chemical constituents may include at least one or more rare earth elements. This helps to reduce or circumvent unnecessary disposal of the spent catalyst in landfills, as value-added products may be recovered using the present methods.

[0040] In certain non-limiting embodiments of the methods, recovery of the different products may involve precipitation at different pHs. As a non-limiting example, which is described in more details in the examples section, certain non-limiting embodiments of the methods may involve recovery of NaLa(SO4)2 by using pH dependent approaches (e.g., at pH 2 to 4), such as simultaneous addition of a solution of base leachate (e.g. NaHCOs - obtained after silica recovery, in presence of excess Na+) to a sulfuric acid treated leachate (pH 0 to 1). The obtained NaLafSCU)? has efficient recovery with purity similarly as a Na(SC>4)2 precipitation approach. Then, after filtration of NaLaSC as solid, the pH of the acid solution may be adjusted by addition of an excess solution of the base leachate (NaHCCh) (in excess Na+) to acid at pH 6 to 7 to generate alumina as another product. This method not only avoids use of excess sodium sulfate to recover the NaLa(SC> )2 crystals, but also decreases the process cost and increase the process efficiency. Similarly, the development of process parameters of the present methods, such as recovery of base, recovery of water, heat integration, and change in process steps, have a direct impact on reduction of solid waste, feasibility of the process, decreasing number of process steps, improved technoeconomic towards positive side and a considerable decrease in CO2 emission of the process.

[0041] Also, in various embodiments, the methods disclosed herein involve improved processes, efficiency, and cost in the recovery of one or more rare earth elements, silica, alumina, and mullite, from a spent catalyst. The spent catalyst may be a spent fluidized bed cracking catalyst (SFCC). The methods may involve converting a solid waste to valuable products without forming any waste in the process. The recovery of all solid products with mass balance may be close to 100%. For example, in certain non-limiting embodiments, the method may involve a solution of acid leachate (PH about 1 to 2), such as sodium sulphate, and a base leachate (PH about 8 to 9), such as as a bicarbonate, mixed with a ratio of about 1:3 to generate not only alumina as asolid product, but also recycle CO2 back to the method for next cycle processing. A resultant liquid solution may contain metal sulphates, wherein the metal sulphates can be easily recovered using a basic metal hydroxide (e.g., calcium hydroxide) with additional gypsum. The stcp(s) in the methods helps avoid disposal of SFCC in landfills, may be considered carbon neutral, generates zero waste and requires no wastewater treatment.

[0042] With the above in mind, details of the methods and their various embodiments, are described as follow .

[0043] In the present disclosure, there is provided a method for recovering chemical constituents from a spent catalyst comprising the chemical constituents. In various embodiments, the method may comprise treating the spent catalyst with an acid (e.g., sulfuric acid, hydrochloric acid, nitric acid) to form a first leachate and a first residue. In various embodiments, the first leachate may comprise a rare earth metal and aluminum. In various embodiments, the first residue may comprise silicon and aluminum. In various embodiments, the method may comprise treating the first residue with a base to form a second leachate and a second residue. In various embodiments, the second leachate may comprise silicon. In various embodiments, the second residue may comprise mullite. In various embodiments, the method may comprise treating the second leachate with gaseous carbon dioxide to form a carbonate-containing base and silicon dioxide. In various embodiments, the method may comprise recycling the carbonate-containing base to mix with the first leachate to form a third residue and a third leachate. In various embodiments, the method may comprise NaLafSChh. The use of gaseous carbon dioxide as a precipitating agent allows recovery of silica (silicon dioxide) from the “base leachate” leading to free Na+ions and NaHCO3 in liquid.

[0044] hr the context of the present disclosure, the term leachate refers to a liquid that may contain dissolved substances. The liquid may have been percolated through a filter, and in such instances, the leachate may be exchangeably referred to as “filtrate”.

[0045] In various embodiments, the carbonate-containing base may comprise or consist of sodium bicarbonate, i.e., NaHCOr. In various embodiments, the sodium bicarbonate may contain an excess of sodium cation, i.e., Na+. Advantageously, thesodium bicarbonate solution allows lanthanum to be extracted from an acidic leachate (containing the lanthanum) without using a considerably alkaline solution, as sodium bicarbonate is a relatively weak base having a pH of 8 to 9.

[0046] In various embodiments, recycling the carbonatc-containing base to mix with the first leachate may be carried out at an acidic pH to form the third residue and the third leachate. In various embodiments, the acidic pH may be in a range of 1 to 3. This pH range aids extraction of highly pure lanthanum complex. If the pH is higher than 3, alumina may be extracted (together with or instead of the lanthanum complex).

[0047] In various embodiments, the method may further comprise treating the third leachate to form alumina and a fourth leachate. In various embodiments, treating the third leachate to form alumina and the fourth leachate may be carried out at a pH higher than the acidic pH to form alumina and the fourth leachate. In various embodiments, the pH higher than the acidic pH is in a range of 6 to 7. This pH range is close to being neutral, but still relatively acidic for extraction of alumnium-based compounds.

[0048] In various embodiments, recycling the carbonate-containing base to mix with the first leachate to form the third residue and the third leachate may comprise mixing, simultaneously, the acid and the carbonatc-containing base with the spent catalyst. This may involve formation on lanthanum oxide on silica alumina, which may be carried out by treatment of a basic leachate containing silica (before contacting with the gaseous carbon dioxide as precipitating agent) to an acidic leachate containing both lanthanum and alumina. This mixing helps render lanthanum oxide / silica: alumina as a resultant solid product (i.e. , the third residue).

[0049] In various embodiments, the method may further comprise treating the fourth leachate with a metal hydroxide, in the presence of gypsum, to form a metal salt and an alkali, wherein the fourth leachate may comprise NazSO i. Advantageously, the use of a metal hydroxide (e.g., calcium hydroxide) aids in sulfate ions exchange to form gypsum, which may be easily rendered in the process. Moreover, this aids in recycling of a base (such as NaOH), which may be recycled by exchanging NaiSC with Ca(OH)2 to NaOH and CaSO4. hi various embodiments, treating the fourth leachate may be carried out at a pH of 12 to 14, 12 to 13, etc. In various embodiments, the metal hydroxide may comprise calcium hydroxide.

[0050] In various embodiments, the method may further comprise mixing the second leachate with the first leachate to form a composition that may comprise the rare earth element, aluminum, and silicon. Such a composition may be LazO;. SiCb.AICh (denoted as La / (silica: alumina)). The composition may be slightly modified to be used as a recycled fluidized bed cracking catalyst (FCC) in cracking.

[0051] In various embodiments, the rare earth metal comprises lanthanum (La) and / or cerium (Ce). In the context of the present disclosure, the term “rare earth metal” refers to 17 chemical elements of the periodic table, includes 15 chemical elements of the lanthanide series, from lanthanum to lutetium, as well as two other chemical elements, i.e., scandium and yttrium.

[0052] The present disclosure also provides for a method for recovering chemical constituents from a spent catalyst comprising the chemical constituents. Embodiments and advantages described in the context of the present method are analogously valid for the method described above, and vice versa. Embodiments and advantages of the method described above, which have already been mentioned above and demonstrated in the examples, and shall not be iterated for brevity.

[0053] In various embodiments, the method may comprise treating the spent catalyst with an acid (c.g., sulfuric acid, hydrochloric acid, nitric acid) to form a first leachate and a first residue. In various embodiments, the first leachate may comprise a rare earth metal and aluminum. In various embodiments, the first residue may comprise silicon and aluminum. In various embodiments, the method may comprise treating the first leachate with a sodium salt to form a second residue that may comprise the rare earth metal (and in certain non-limiting instances an acidic solution may also be rendered). In various embodiments, the method may comprise treating the first residue with a base to form a second leachate and a second residue. In various embodiments, the second leachate may comprise silicon. In various embodiments, the second residue may comprise mullite. In various embodiments, the method may comprise treating the second leachate with gaseous carbon dioxide to form a carbonate-containing base and silicon dioxide. In various embodiments, the method may comprise mixing the sodium salt, after treating the first leachate with the sodium salt, with the base, to fonn carbon dioxide and alumina-containing residue. In various embodiments, the method may comprise recycling the carbon dioxide as the gaseous carbon dioxide fortreating the second leachate to form the carbonate-containing base and the silicon dioxide.

[0054] hi various embodiments, the carbonate-containing base may comprise NaHCCh in excess sodium cation.

[0055] hi various embodiments, the sodium salt may comprise sodium sulfate.

[0056] In various embodiments, the method may further comprise treating the alumina-containing residue with a metal hydroxide, in the presence of gypsum, to form a metal salt and an alkali. In various embodiments, the method may comprise recycling the alkali as the base for treating the first residue to form the second leachate and the second residue.

[0057] In various embodiments, the metal hydroxide may comprise calcium hydroxide.

[0058] In various embodiments, mixing the sodium salt with the base may comprise mixing the sodium salt and the base in a ratio of 1 to 3.

[0059] In various embodiments, the rare earth metal may comprise lanthanum and / or cerium.

[0060] In various embodiments, the second residue may comprise LaiOr

[0061] In the context of the present disclosure, the word “substantially” docs not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the invention.

[0062] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0063] In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance. The variance may be ±0.1%, +0.5%, +1%, +5%, or even +10%.

[0064] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0065] Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" languagesuch that they include recited elements but also permit inclusion of additional, unrecited elements.

[0066] While the methods described above are illustrated and described as a series of steps or events, it will be appreciated that any ordering of such steps or events arc not to be interpreted in a limiting sense. For example, some steps may occur in different orders and / or concurrently with other steps or events apart from those illustrated and / or described herein. Tn addition, not all illustrated steps may be required to implement one or more aspects or embodiments described herein. Also, one or more of the steps depicted herein may be carried out in one or more separate acts and / or phases.Examples

[0067] The present disclosure relates to methods for recovering chemical constituents from a spent catalyst comprising the chemical constituents. The present disclosure provides methods to produce rare earth elements (REE), silica (SiOn), alumina, and mullite, from a spent catalyst. In various non-limiting examples, the spent catalyst may be, for example, spent fluidized bed cracking catalyst (SFCC). Non-limiting examples of the rare earth clement may be lanthanum (La) and cerium (Ce).

[0068] Further details of the methods are discussed, by way of non-limiting examples, as set forth below.

[0069] Summary Example:

[0070] Methods of the present disclosure are illustrated by way of non-limiting examples in and can be understood from FIG. 2B and FIG. 17. FIG. 2B shows one of the methods depicted as strategy-I and one of the methods depicted as strategy-II. FIG. 17 is a schematic diagram of strategy-I.

[0071] In the method shown via strategy-I, there is a method for recovering chemical constituents from a spent catalyst comprising the chemical constituents, the method may comprise: treating the spent catalyst with an acid to form a first leachate and a first residue, wherein the first leachate may comprise a rare earth metal and aluminum, and wherein the first residue may comprise silicon and aluminum; treating the first leachate with a sodium salt to form a second residue comprising the rare earthmetal (and in certain non-limiting instances an acidic solution may also be formed, e.g., sulfuric acid); treating the first residue with a base to form a second leachate and a second residue, wherein the second leachate may comprise silicon, and wherein the second residue may comprise mullite; treating the second leachate with gaseous carbon dioxide to form a carbonate -containing base and silicon dioxide; mixing the sodium salt, after treating the first leachate with the sodium salt, with the base, to form carbon dioxide and an alumina-containing residue; and recycling the carbon dioxide as the gaseous carbon dioxide for treating the second leachate to form the carbonate-containing base and the silicon dioxide.

[0072] In various non-limiting examples, the carbonate-containing base may comprise NaHCC in excess sodium cation.

[0073] In various non-limiting examples, the sodium salt may comprise sodium sulfate.

[0074] In various non-limiting examples, the method may further comprise: treating the alumina-containing residue with a metal hydroxide, in the presence of gypsum, to form a metal salt and an alkali; and recycling the alkali as the base for treating the first residue to form the second leachate and the second residue.

[0075] In various non-limiting examples, the metal hydroxide may comprise calcium hydroxide.

[0076] In various non-limiting examples, mixing the sodium salt with the base may comprise mixing the sodium salt and the base in a ratio of 1 to 3.

[0077] In various non-limiting examples, the rare earth metal may comprise lanthanum or cerium.

[0078] In various non-limiting examples, the second residue may comprise La2Os.

[0079] In the example method illustrated via strategy-II, there is a method for recovering chemical constituents from a spent catalyst comprising the chemical constituents. The method may involve recycling components from the method under strategy-I. The method may comprise: treating the spent catalyst with an acid to form a first leachate and a first residue, wherein the first leachate may comprise a rare earth metal and aluminum, and wherein the first residue may comprise silicon and aluminum; treating the first residue with a base to form a second leachate and a second residue, wherein the second leachate may comprise silicon, and wherein thesecond residue may comprise mullite; treating the second leachate with gaseous carbon dioxide to form a carbonate-containing base and silicon dioxide; and recycling the carbonate-containing base to mix with the first leachate (of strategy-II) to form a third residue and a third leachate, wherein the third residue may comprise NaLa(SO4)2.

[0080] In various non-limiting examples, the carbonate-containing base may comprise Nal ICO , in excess sodium cation.

[0081] In various non-limiting examples, recycling the carbonate-containing base to mix with the first leachate may be carried out at an acidic pH to form the third residue and the third leachate.

[0082] In various non-limiting examples, the method may further comprise: treating the third leachate to form alumina and a fourth leachate.

[0083] In various non-limiting examples, treating the third leachate to form alumina and the fourth leachate may be carried out at a pH higher than the acidic pH to form alumina and the fourth leachate.

[0084] In various non-limiting examples, the acidic pH may be in a range of 1 to 3.

[0085] In various non-limiting examples, the pH higher than the acidic pH may be in a range of 6 to 7.

[0086] In various non-limiting examples, recycling the carbonate-containing base to mix with the first leachate to form the third residue and the third leachate may comprise mixing, simultaneously, the acid and the carbonate-containing base with the spent catalyst.

[0087] In various non-limiting examples, the method may further comprise: treating the fourth leachate with a metal hydroxide, in the presence of gypsum, to form a metal salt and an alkali, wherein the fourth leachate comprises NarSOr.

[0088] hr various non-limiting examples, treating the fourth leachate may be carried out at a pH of 12 to 14.

[0089] In various non-limiting examples, the method may further comprise: mixing the second leachate with the first leachate to form a composition comprising the rare earth element, aluminum, and silicon.

[0090] In various non-limiting examples, the rare earth metal may comprise lanthanum or cerium.

[0091] Example 1A: General Description of Method Involving pH Effect and Heat

[0092] The present method advantageously produces one or more rare earth elements, silica (SiCh), alumina, and mullite, from a spent catalyst. Solid waste obtained from refineries may be dumped into landfills, which subsequently creates not only land claiming but also environmental concerns related to air and water pollution. The present method helps to address at least such problems.

[0093] In the present method, the SFCC valorisation can be carried out using acid / base leaching followed by selective precipitation. Highlights of the method include (1) Use of a base leaching solution (NaHCO j (also termed herein cxchancgably as a “base leachate” and “carbonatc-containing base”), which is obtained from recovery of silica, mixed with an acid solution (mixed with the SFCC) to produce subsequent leachates with different pHs. The addition of acid solution at pH 2 to 4 can render recovery of NaLaSCri crystals, further addition of the base leaching solution (NaHCOs) to alter the pH of the acid solution (containing the SFCC) to pH 6 to 7 can render recovery of alumina product, (2) the method being a one step synthesis of a composition of La / (silica: alumina) by mixing solutions of LaSO4.H2O, AISO4 H2O, (pH 1) (from acid leaching) to a base solution (NaSiOvFFO, pH 13 to 14), and (3) the method configures the process steps, base concentration, heat integration, so to recycle the base solution (carbonate-containing base) and recycle of process water. The recovery of products is well defined and matched with specifications. Thus, the modification of process not only pave a chance to recover a distributed products but also helps to synthesis identical fresh FCC catalyst to the petroleum refinery. Subsequently, the effective benefit by this approach is estimated by techno-economic analysis (TEA), which showed drastically decrease in process cost and increase in positive net profit value (NPV) with minimum breakeven time. This understandably indicates that this modified methodology in the process can be consider as carbon neutral, energy efficient and sustainable process.

[0094] Example IB: Detailed Illustration and Results of Method of Example 1A

[0095] FIG. 1 results showed that the screening of SFCC by adopting different process and protocols. In particular, the downstream treatments were carried out using 3 kg SFCC samples and liquids at lab scale. It was successfully demonstrated that therecovery of four different products including La, Silica, Mullite and alumina from spent SFCC with optimum yield. Here, the recovery of sodium lanthanum sulphate has been recovered by using the solution obtained from base leachate (NaHCCh, PH-8- 10) after silica recovery at PH2-4 with optimum yield of 75-80%. Then addition of remaining base leachate to the La recovered acid solution until PH6-7 helped to recover solid alumina in the form (AISO4) from the solution. The purity of NaLa(SC>4)2 is very well matched similarly to NaSCL treated method, which is confirmed by XRF and SEM. In another strategy, it was established that by mixing obtained acid leachate (before La recovery) and base leachate (before silica recovery), La / Silica:Alumina was produced, which may be utilized as a precursor for FCC catalyst (FIG. 2A and 2B).

[0096] In FIG. 3, the XRF study clearly states that the La, Na and S elements are presents in the recovered samples. Also, the presence of Ce is also observed (FIG. 3). This is very well matched with obtained results with previous NaSO4 precipitation method. Moreover, the well differentiated hexagonal prism morphological particles of NaLa(SO )2 have been observed similar to previous precipitation method (FIG. 4).

[0097] From FIG. 5, the XRD study of both alumina and silica alumina showed respective crystalline phases of alumina and silica alumina phases. The silica alumina sample showed a broad peak at 2 theta 23-28 is respective to the amorphous nature of silica. This clearly identified that the silica alumina and alumina samples are distinctly different, which confirm that the recovery of obtained solids arc pure.

[0098] Example 2A: General Description of Method to Precipitate Silica, Lanthanum and Alumina via a Sustainable Process

[0099] The method is advantageously a sustainable process for utilizing spent FCC to produce rare earth element (REE), such as La, silica (SiOz), alumina and mullite. The solid waste obtained from refineries are generally dumped into landfilling, which subsequently creates not only land claiming, but also environmental concerns related to air and water pollution. Here, the developed process carried out acid / basc leaching followed by selective precipitation. Also, recovery of silica using CO2 precipitation at atmospheric conditions and finally recovery of solid alumina using recycled acid and base solution, which generates CO2 for back next cycle. The obtained solution mainly contains metal salt, the base metal hydroxide can be regenerated using calciumhydroxide treatment. This clearly indicates that the there is no solid material for landfilling, CO2 neutral process, zero waste and no wastewater.

[0100] The presently developed method contains acid and base leaching of waste solid followed by selective precipitation. The successful recovery of La in the crystalline form of NaLa(SO4)2, which has more than 95% purity. Obtained mullite after acid and base leaching in our process has similar properties of mullite synthesize via traditional heat treatments (>800-1200 °C and sintering by solid-state reactions with the 3:2 stoichiometry) of clays. The sintering process of mullite has high CO2 equivalent emission as against our synthetic mullite, which is produced at 90-100 °C. Recovery of silica using CO2 precipitation of obtained sodium silicate after base leaching at atmospheric conditions. Then recovery of solid alumina using recycled acid and base solution, which generates CO2 back for next cycle. The obtained solution mainly contains metal salt, recycle of base metal hydroxide can be regenerate using calcium hydroxide treatment with added gypsum product. Hence, in this process there is no solid material for landfilling, CO2 neutral process, zero waste and no wastewater.

[0101] The developed method offers improved recovery of rare earth elements, silica, alumina and mullite from spent FCC catalyst. The unique approach is in process to convert solid waste to valuable products without forming any waste in the process. Typically, the recovery of all solid products with mass balance close to 100%. The protocol adopted in such way that, the final solution of acid leachate (PH= 1-2) associated with sodium sulphate and base leachate (PH= 8-9) as bicarbonate with optimum ratio 1:3 mixing can generate not only alumina as solid product but also recycle of CO2 back to the next cycle. Finally, the obtained liquid solution contains metal sulphates, which can be easily regenerate base metal hydroxide using calcium hydroxide with additional gypsum as a product in the process. This unique step in the process can be consider as carbon neutral, zero waste and no wastewater treatment.

[0102] Example 2B: Detailed Illustration and Results of Method of Example 2A

[0103] Screening of SFCC batch 2 and 3 with changes of parameters such as molar ratio of base (1.25 to 1,75M), recycle of acid solution and change in liquid to solid ratio typically in base leaching from 1:10 to 1:15. The overall observation suggests that, the recovery rate for La is in the range of 70-80%, the silica yield is in the rangeof 30-35% for both batches B2 and B3. The recycle of acid solution did not show any improvement in the increase of La recovery, this suggests optimum 3N acid solution required for best optimized yield of La. The effect of molar ratio of base, the increasing base molarity from 1.25 to 1,75M, the yield of silica is improved. The acid washing of the base leachate solid of mullite and silica showed more than 20% loss to the actual yield of the products. The protocol adopted to recover the solid as Al, which may be in the form of NaAl(S Or)2 known as Alum. The formation of Alum has been confirmed by XRF and XRD study, which needs to study in detail with further characterization study.

[0104] From FIG. 12A and 12B, the XRD results for various recovered samples of B2 and B3 have been evaluated, the planes of SFCC 2 and SFCC 3 samples were exhibited typically for silica alumina with impurities of other metal oxides. The all XRD planes of solid are very well match with the NaLa(SC>4)2 crystals as a sole species, which has been supported by SEM study. The amorphous nature of silica has been observed by typical broad peak of XRD results. The XRD planes of mullite were clearly matches, which has been confirmed by JCPDS data. Similarly, the typical planes of Alumina, Na2SC>4 and CaSC>4 have been identified.

[0105] In FIG. 13, The XRF study of all recovered samples have been carried out, the actual concentration of respective metal oxides is very close to the expected metal oxides. The La is in the form of sodium lanthanum sulphate and Al may consider as sodium aluminium sulphate (well know as Alum). The observation of alum formation is based on obtained oxides of alumina, sulphur, and sodium. The ratio of alumina to silica is 2:1, in mullite, which is matches very with the commercial ratio of mullite. The obtained silica has a very high purity, the traces of Na O have been disappear' after acid washing. Both Sodium sulphate and calcium sulphate showed respective metal oxides. This may justify, the recovery of all other metal oxides completed during the process.

[0106] From FIG. 14, the SFCC 2 and 3 samples were analysed using SEM study, the spherical morphology of agglomerated particles with more than 100mm sizes were obtained. On the other hand, the well differentiated hexagonal prism morphological particles of NaLa(SO4)2have been observed, which has been very well matched with our lab scale recovered sample study.

[0107] From FIG. 15, the BET (Bnmauer, Emmett and Teller) surface area for B2 and B3 have been characterized. The silica recovers from batch 2 has surface area about 104 m2 / g, while the surface area for batch 3 recovered silica is 633 m2 / g. The acid wash silica decreased the surface area slightly to 581 m2 / g.

[0108] FIG. 17 shows the process loop, which depicts a carbon neutral process for the efficient recovery of the value added La, silica, mullite and Alumina via SFCC. Most of the products were separated, the CO2 and base NaOH can be recycled. The main interest for the modification of the process do not generate waste by handling waste utilization.

[0109] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

CLAIMS1. A method for recovering chemical constituents from a spent catalyst comprising the chemical constituents, the method comprising: treating the spent catalyst with an acid to form a first leachate and a first residue, wherein the first leachate comprises a rare earth metal and aluminum, and wherein the first residue comprises silicon and aluminum; treating the first residue with a base to form a second leachate and a second residue, wherein the second leachate comprises silicon, and wherein the second residue comprises mullite; treating the second leachate with gaseous carbon dioxide to form a carbonate - containing base and silicon dioxide; and recycling the carbonate-containing base to mix with the first leachate to form a third residue and a third leachate, wherein the third residue comprises NaLafSCLh.

2. The method of claim 1, wherein the carbonate-containing base comprises NaHCCh in excess sodium cation.

3. The method of claim 2 or 3, wherein recycling the carbonate-containing base to mix with the first leachate is carried out at an acidic pH to form the third residue and the third leachate.

4. The method of any one of claims 1 to 3, further comprising: treating the third leachate to form alumina and a fourth leachate.

5. The method of claim 4, wherein treating the third leachate to form alumina and the fourth leachate is carried out at a pH higher than the acidic pH to form alumina and the fourth leachate. The method of any one of claims 3 to 5, wherein the acidic pH is in a range of7. The method of claim 5 or 6, wherein the pH higher than the acidic pH is in a range of 6 to 7.

8. The method of any one of claims 1 to 7, wherein recycling the carbonatc- containing base to mix with the first leachate to form the third residue and the third leachate comprises mixing, simultaneously, the acid and the carbonate-containing base with the spent catalyst.

9. The method of any one of claims 4 to 8, further comprising: treating the fourth leachate with a metal hydroxide, in the presence of gypsum, to form a metal salt and an alkali, wherein the fourth leachate comprises ISfeSCh.

10. The method of claim 6, wherein treating the fourth leachate is carried out at a pH of 12 to 14.

11. The method of any one of claims 1 to 10, further comprising: mixing the second leachate with the first leachate to form a composition comprising the rare earth clement, aluminum, and silicon.

12. The method of any one of claims 1 to 11, wherein the rare earth metal comprises lanthanum or cerium.

13. A method for recovering chemical constituents from a spent catalyst comprising the chemical constituents, the method comprising: treating the spent catalyst with an acid to form a first leachate and a first residue, wherein the first leachate comprises a rare earth metal and aluminum, and wherein the first residue comprises silicon and aluminum; treating the first leachate with a sodium salt to form a second residue comprising the rare earth metal; treating the first residue with a base to form a second leachate and a second residue, wherein the second leachate comprises silicon, and wherein the second residue comprises mullite;treating the second leachate with gaseous carbon dioxide to form a carbonate- containing base and silicon dioxide; mixing the sodium salt, after treating the first leachate with the sodium salt, with the base, to form carbon dioxide and an alumina-containing residue; and recycling the carbon dioxide as the gaseous carbon dioxide for treating the second leachate to form the carbonate-containing base and the silicon dioxide.

14. The method of claim 13, wherein the carbonate-containing base comprises NaHCOa in excess sodium cation.

15. The method of claim 13 or 14, wherein the sodium salt comprises sodium sulfate.

16. The method of any one of claims 13 to 15, further comprising: treating the alumina-containing residue with a metal hydroxide, in the presence of gypsum, to form a metal salt and an alkali; and recycling the alkali as the base for treating the first residue to form the second leachate and the second residue.

17. The method of any one of claims 13 to 16, wherein the metal hydroxide comprises calcium hydroxide.

18. The method of any one of claims 13 to 17, wherein mixing the sodium salt with the base comprises mixing the sodium salt and the base in a ratio of 1 to 3.

19. The method of any one of claims 13 to 18, wherein the rare earth metal comprises lanthanum or cerium.

20. The method of claim 13, wherein the second residue comprises LazO’,.

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