Solid Phosphoric Acid Catalyst Research Articles

Solid phosphoric acid catalysts based on mesoporous silica for levoglucosenone production via cellulose fast pyrolysis

ABSTRACTBACKGROUNDBiochemicals are interesting alternatives for biomass valorization owing to their much higher added value compared to biofuels and energy products. Several methods for the production of valuable chemicals such as levoglucosenone (LGO) via thermochemical processes over solid acid catalysts are being investigated due to their important advantages compared to conventional biomass acid impregnation techniques. The present work explores the synthesis of catalytic materials for the production of this platform molecule.RESULTSAluminum‐loaded SBA‐15 mesoporous silica and the corresponding solid phosphoric acid (SPA) catalysts were prepared, characterized by TEM, FTIR, MAS NMR, NH3‐TPD, N2 adsorption, ICP‐AES and titration of ‘free H3PO4’, and tested in cellulose fast pyrolysis. Post‐synthesis Al deposition on the silica support produced an increase of bio‐oil yield and LGO amount in pyrolysis products. The presence of Al in SPA catalysts led to the formation of aluminum phosphates, decreasing the concentration of H3PO4 species in the surface and therefore the LGO levels. The SPAs presented relatively high LGO levels in the GC–MS detectable liquid products (up to 85 peak area%) which was found to be correlated with the amount of free H3PO4 in the solid catalysts.CONCLUSIONAluminum grafting over SBA‐15 is an effective way to increase the selectivity to the target anhydrosaccharide. In SPAs, the presence of Al reduced the easily leachable H3PO4 amount, which is desirable from the point of view of catalyst stability because deactivation is mainly caused by H3PO4 leaching, but also led to lower levels of LGO in bio‐oil. © 2018 Society of Chemical Industry

Multinuclear magnetic resonance study on the occurrence of phosphorus in activated carbons prepared by chemical activation of lignocellulosic residues from the babassu production

Activated carbons with well-developed microporosity and containing dispersed nanostructured phosphorus compounds were produced by the chemical activation with H3PO4 of an abundant Brazilian lignocellulosic residue (endocarp of babassu coconut). The chemical nature of the phosphorus-containing species in the produced materials was studied by 1H, 13C and 31P solid-state NMR spectroscopy, including 2D 1H-31P correlation experiments and the use of 1H homonuclear decoupling. With this approach, it was possible to detect the formation of different phosphorus compounds (mostly containing phosphate groups) embedded into the porous carbon network and exhibiting strong dipolar coupling between 31P nuclei and 1H nuclei in hydrogen atoms bonded to aromatic carbons. The chemical activation with H3PO4 was found to be noticeably effective when starting from the raw lignocellulosic precursor, leading to the achievement of activated carbons with large surface area (up to 1900m2/g). Due to the natural occurrence of silicon compounds in the endocarp of babassu coconut, the chemical activation with H3PO4 was found to produce silicon pyrophosphate nanocrystals in addition to phosphate groups in non-crystalline clusters dispersed into the porous structure of the activated carbons, suggesting that these materials can be useful for applications as solid phosphoric acid catalysts.

Phosphated tungstate: An efficient new solid phosphoric acid catalyst for the synthesis of heterocyclic nitrones

Phosphated tungstate as a new, reusable and efficient solid phosphoric acid catalyst was synthesized and used to promote the reaction of diaminoglyoxime with various aromatic aldehydes. The prepared phosphated tungstate was characterized using various techniques including X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy and thermal analysis. A wide variety of heterocyclic nitrones were obtained under mild reaction conditions and in high yields by using the prepared catalyst.

Elucidation of phosphorus interaction in dual component zeolite/matrix catalysts: Selectivity control in olefin oligomerization with MTW/Al2O3

Treatment of alumina bound MTW zeolite extrudates with H3PO4 causes conversion of the binding matrix from Al2O3 to tridymite AlPO4 and we show the crystalline AlPO4 coats the surface of the MTW zeolite crystals. In this transformation, the surface area and pore volume of the catalyst decrease precipitously, but the MTW crystallinity remains largely intact. Similar, but less specific behavior was observed when using NH4H2PO4 as the phosphorus source. After phosphate treatment, the interaction of P with zeolite framework Al is a major effect reducing acidity of the zeolite. These two effects allow for selectivity control during oligomerization of propylene and butenes. Increasing the phosphorus content of the catalyst from 0 to 10wt% causes a decrease in the amount of liquid product heavier than gasoline from 15wt% to 3wt%. Concomitantly, the selectivity to triisobutylenes increases to almost 50%. Thus we attain catalytic performance similar to traditional solid phosphoric acid catalyst, but with a significant yield of triisobutylenes.

Renewable p‐Xylene from 2,5‐Dimethylfuran and Ethylene Using Phosphorus‐Containing Zeolite Catalysts

Abstractp‐Xylene is a major commodity chemical used for the production of polyethylene terephthalate, a polymer with applications in polyester fibers, films, and bottles. The Diels–Alder cycloaddition of 2,5‐dimethylfuran and ethylene and the subsequent dehydration of the cycloadduct intermediate is an attractive reaction pathway to produce renewable p‐xylene from biomass feedstocks. However, the highest yields reported previously do not exceed 75 %. We report that P‐containing zeolite Beta is an active, stable, and selective catalyst for this reaction with an unprecedented p‐xylene yield of 97 %. It can catalyze the dehydration reaction selectively from the furan‐ethylene cycloadduct to p‐xylene without the production of alkylated and oligomerized products. This behavior is distinct from that of Al‐containing zeolites and other solid phosphoric acid catalysts and establishes a commercially attractive process for renewable p‐xylene production.

Oligomerization of Light Olefins to Gasoline: An Advanced NMR Characterization of Liquid Products

Using multiple 1H and 13C NMR spectroscopic techniques, we have investigated the C8 cut from samples of liquid products obtained by the oligomerization of light olefins over solid phosphoric acid (SPA) and MTW zeolite. The carbon species present, CHn (n = 0–3), were identified by DEPT NMR and quantified using inverse-gated decoupled 13C NMR spectra. The olefinic protons and carbons as well as the types of olefins were quantified. 13C NMR shows that the amount of methyl carbons is similar for both catalysts but that methylene and methyne carbon distributions are different. The product obtained over MTW catalyst showed higher quantities of quaternary olefins, likely from type V tetrasubstituted olefins, compared to that over SPA catalyst. In addition, 2D NMR has also been attempted to understand the proton and carbon connectivities and confirmed the presence of type I and II olefins.

A novel solid phosphoric acid from rice hull ash for olefinic alkylation of thiophenic sulfur in gasoline

ABSTRACT A novel solid phosphoric acid (SPA) was prepared from rice hull ash by impregnation with phosphoric acid and followed by calcination. The characterization results reveal that the solid phosphoric acid exhibits high surface area (335 m 2 /g) and acid densities (1.25 mmol/g) compared with commercial SPA catalyst. It was also clearly confirmed that silicon phosphate and silicon pyrophosphate were formed by the reaction of silica with phosphoric acid during the calcination process. The OATS catalytic performance results indicate that the solid phosphoric acid shows very good activity for thiophene alkylation reaction. This research provided a promising way to synthesis high active solid phosphoric acid for OATS desulfurization application.

Selective Production of Levoglucosenone from Catalytic Fast Pyrolysis of Biomass Mechanically Mixed with Solid Phosphoric Acid Catalysts

Solid phosphoric acid (SPA) catalysts with different carriers were prepared and used for catalytic fast pyrolysis of poplar wood to produce levoglucosenone (LGO), a valuable anhydrosugar derivative that can be used in various organic synthesis applications. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were performed to evaluate the catalytic capabilities of these catalysts under different reaction conditions. The results indicated that SPA catalyst prepared with the SBA-15 carrier exhibited the best catalytic capability for selectively producing LGO. Both the catalytic pyrolysis temperature and catalyst-to-biomass ratio affected the pyrolytic products greatly. The maximal LGO yield reached as high as 8.2 wt% from poplar wood, obtained at the pyrolysis temperature of 300 °C and the catalyst-to-biomass ratio of 1. The by-products during the catalytic pyrolysis process were mainly acetic acid (AA) and furfural (FF). In addition, the SPA catalyst possessed better catalytic capability than the liquid phosphoric acid (H3PO4) catalyst to produce LGO.

Solid phosphoric acid catalyst for propene oligomerization: Effect of silicon phosphate composition

Solid phosphoric acid catalysts have been industrially used for propene oligomerization to improve the gasoline quality. However, solid phosphoric acid catalysts will lose their mechanical strength in the presence of water which is used to hydrolyze silicon phosphates to produce free phosphoric acids for maintaining the catalytic activity. In this case, to harmonize the catalyst lifetime and activity of solid phosphoric acid catalysts, the properties of silicon phosphate were investigated to achieve the maximum catalytic performance. A solid phosphoric acid catalyst was prepared with kieselguhr and concentrated phosphoric acid. Trace water was used to promote the release of active components from silicon phosphates during the reaction. Free phosphoric acid content, as a vital property of a solid phosphoric acid catalyst, was measured by ammonia temperature-programmed desorption. The crystal phase composition of silicon phosphates in a solid phosphoric acid catalyst was analyzed by X-ray diffraction. The catalytic performance was evaluated in a fixed bed under the conditions of 210°C and 4MPa. A solid phosphoric acid catalyst with relative content of 51% Si5O(PO4)6 and 49% SiP2O7 showed the best performance in improving catalytic activity and lifetime, and the conversion of propene was above 99% for nearly 70h.

ECONOMIC OPTIMIZATION OF THE CUMENE PRODUCTION PROCESS USING RESPONSE SURFACE METHODOLOGY

The process of manufacturing cumene from propylene and benzene on a solid phosphoric acid catalyst was studied. The aim of this article is to optimize this process economically and to realize how statistical methods can be utilized to optimize the operational conditions of the process at the industrial scale. The net present value (NPV) that reflects all the economic aspects of the process was chosen as the objective function for optimization. The NPV of the base process was estimated at $0.19 million. In the first step, the full factorial design was applied to determine the significant factors affecting the process. Results revealed that benzene recycle, reactor volume, reactor pressure, and inlet temperature, as well as the binary interaction of recycle-temperature and recycle-pressure influence the NPV. Benzene recycle and inlet temperature had the most important effects on NPV. In the second step, the response surface methodology was applied to find a reliable quadratic model for NPV. Optimization of the effective parameters was carried out. The maximum predicted value of NPV was calculated $4.56 million at benzene recycle of 141.4 kmol/h, temperature of 340°C, and pressure of 29 bar with 468 tubes inside the reactor.

Fractionation by liquid chromatography combined with comprehensive two-dimensional gas chromatography–mass spectrometry for analysis of cyclics in oligomerisation products of Fischer–Tropsch derived light alkenes

In oligomerisation products of High Temperature Fischer–Tropsch (HTFT) derived light alkenes using a solid phosphoric acid (SPA) catalyst, the presence of cyclics was presumed although their occurrence could not be explained by the generally accepted oligomerisation mechanism. Notwithstanding the use of GC×GC-TOFMS, the cyclic alkanes could not be differentiated from the alkenes. On the one hand, compounds co-eluted in GC×GC and, on the other hand, MS cannot distinguish between these classes because of identical molecular masses and very similar mass fragmentation patterns. An LC pre-fractionation procedure utilising a silver-modified column was developed to separate the saturates from the unsaturates. Using this approach we were able, for the first time, to confirm the presence of cyclics, probably resulting from secondary reactions, in HTFT oligomerisation products. The occurrence of cyclics can be an indication of the beginning of carbonaceous deposit formation that could eventually lead to catalyst deactivation.

The performance of solid phosphoric acid catalysts and macroporous sulfonic resins on gasoline alkylation desulfurization

Sulfur removal has received increasing attention in recent years primarily for environmental protection purpose. As an attractive technology in the case of gasoline, OATS (olefinic alkylation of thiophenic sulfur) proposed to separate sulfur compounds by distillation after being weighed down by alkylation with olefins in the feed. In this paper, alkylation reactions of thiophenic compounds were studied over solid phosphoric acid catalysts (SPAM and SPAS using MCM-41 and Silicalite-1 zeolite as supporters respectively) and macroporous sulfonic resins (including NKC-9, D005-2 and Amberlyst 35) with model gasoline and FCC (fluid catalytic cracking) gasoline. Results showed that macroporous sulfonic resins showed better performance than solid phosphoric acid catalysts under milder conditions in both feeds. Among the resins, Amberlyst 35 was the most suitable catalyst for the application of catalytic distillation for its good performance at the temperature range of 353–413 K in FCC gasoline. However, the selectivity of isoamylene dimerization over Amberlyst 35 decreased with the temperature, which was harmful to the product yield and catalyst stability. Besides, different activity orders of solid phosphoric acid catalysts in model gasoline and FCC gasoline were explained by combining the acidic properties of the catalysts with the species of olefins in two feeds.

Conversion of Spent Solid Phosphoric Acid Catalyst to Environmentally Friendly Fertilizer

Solid phosphoric acid (SPA) catalysts are widely used in the petroleum industry. Despite a high phosphorus content the spent catalyst is generally not reused. Moreover, due to the limited life spans that are achieved industrially, large quantities of spent catalyst requires disposal, often by landfill. SPA can be readily converted to fertilizer, but the presence of carbonaceous deposits on the catalyst presents a potential environmental hazard. This work demonstrates that these deposits are mostly polyaromatic (amorphous carbon) with smaller amounts of oxygenates and aliphatics. Neither the chemical makeup nor the physical structure of the catalyst or the presence of coke precludes it from use as fertilizer. Subsequently, the spent catalyst was milled, neutralized with lime and ammonium hydroxide, and then calcined to yield a phosphate-rich fertilizer. Toxicity characteristic leaching tests of the spent catalyst fertilizer showed low levels of metals and organics, establishing that no harmful compounds are likely to be absorbed into plant life or groundwater. A plant growth study of the spent catalyst fertilizer indicated that it is approximately as effective as superphosphate fertilizer when used in alkaline soil. The spent catalyst fertilizer is environmentally benign and economically efficient.

Solid phosphoric acid catalysts: The effect of free acid composition on selectivity and activity for 1-hexene dimerisation

The rate of dimerisation of 1-hexene in a batch reactor at 200 °C was used to compare the activity and dimerisation route selectivity of solid phosphoric acid (SPA) at various phosphoric acid strengths and subsequently free acid compositions. The initial reaction rates, calculated from an elementary kinetic rate model, showed an increase in catalyst activity with increased acid strength. This trend becomes more significant at acid strengths where the more condensed pyrophosphoric acid started becoming present in the free acid. At low acid strengths, a reaction pathway where linear hexenes were directly oligomerised dominated the reaction progression. An increase in acid strength favoured a two-step reaction pathway, where linear hexenes were first isomerised to skeletal hexene isomers before dimerisation. This sequential pathway becomes especially dominant where pyrophosphoric acid became present in the free acid. However, analysis of the final product with proton NMR showed no significant difference in the degree of branching with a variation in dimerisation route selectivity as a function of acid strength.

UOP announces price increase for solid phosphoric acid catalysts for refining and petrochemicals

UOP announces price increase for solid phosphoric acid catalysts for refining and petrochemicals

Kinetic model for the dimerisation of 1-hexene over a solid phosphoric acid catalyst

Abstract Batch kinetic experiments at 150 °C, 200 °C and 250 °C showed that the reaction can be modeled with a three step sequential reaction scheme. This involves firstly linear isomerisation of 1-hexene followed by skeletal isomerisation and finally dimerisation and cracking. The first and last steps in the sequence are modeled as reversible reactions. When first order reaction kinetics is assumed for each of the reactions, the model gave a very good representation of the experimental data. In order to test the validity of the series pathway hypothesis, the reaction was repeated with a skeletal hexene isomer – 2,3-dimethyl-2-butene (DMB) – as reactant. Although the rate and equilibrium constants for the third reaction step as obtained from the 1-hexene conversion data gave a good prediction of the DMB conversion at 200 °C and 250 °C, it failed to predict the reaction rate at 150 °C. This suggests that a different reaction pathway – where linear hexene isomers are directly converted to dimer product – becomes more significant at lower temperatures. The relatively high activation energy of the linear to skeletal hexene reaction may be to blame for this observation. However, this needs to be confirmed be further experimental work. The same equilibrium conversions of both 1-hexene and DMB were observed at all three temperatures investigated—suggesting that the equilibrium conversion is independent of the type of hexene isomer in the reaction mixture.

Preparation of a Solid Phosphoric Acid Catalyst from Low-Quality KieselguhrParameters Controlling Catalyst Quality and Performance

High-quality Kieselguhr is normally employed as the support for solid phosphoric acid (SPA), the catalyst used for the oligomerization of C3−C5 alkenes in a Fischer−Tropsch refinery. In this paper, we demonstrate that an SPA catalyst of suitable activity can be prepared from a low-quality Kieselguhr provided that the Kieselguhr bulk density is ≤0.3 g/mL. Several catalyst samples were evaluated on microreactor and pilot-plant scale using propene mixtures as feed. An increase in acid-to-Kieselguhr ratio used during catalyst preparation was shown to improve catalyst activity, although this is detrimental to catalyst particle strength under similar calcination conditions. By studying the effect of impurities on catalyst performance, it was confirmed that high impurity levels lower oligomerization activity. It was also established that a high Kieselguhr quartz content (>10% by mass) reduces the catalyst particle crushing strength.

Solid phosphoric acid catalysed conversion of oxygenate containing Fischer–Tropsch naphtha

Abstract The effect of Fischer–Tropsch derived oxygenates on olefin oligomerisation over a solid phosphoric acid (SPA) catalyst is mainly related to increased catalyst hydration and the conversion of strong pyrophosphoric acid (H 4 P 2 O 7 ) sites to weaker orthophosphoric acid (H 3 PO 4 ) sites. At 180 °C, 3.8 MPa and WHSV of 1.5 h −1 , oxygenate conversion to hydrocarbons is 99%. The main oxygen-containing product was water, although alcohols produced by olefin hydration and ketone decomposition to carboxylic acids were also observed. With increasing catalyst hydration the oligomer yield decreased. The extent of inhibition was related to the oxygenate concentration, the nature of the oxygenates and the nature of the olefins. Leaching of phosphoric acid was negligible and not a significant factor in determining catalyst activity. It was shown that olefin oligomerisation on SPA follows a Langmuir–Hinshelwood mechanism.

Selectivity Differences of Hexene Isomers in the Alkylation of Benzene over Solid Phosphoric Acid

Alkylation of benzene with 1-hexene, 2-methylpentenes, 3-methylpentenes, and 2,3-dimethyl-2-butene has been investigated over a solid phosphoric acid (SPA) catalyst at 220 °C. It was found that on SPA linear olefins preferably alkylated, rather than dimerized, as opposed to branched olefins that preferably dimerized. The initial selectivity ratios of dimerization to alkylation for the hexene isomers are 0.16 (n-hexenes), 12 (3-methylpentenes), 21 (2-methylpentenes), and 33 (2,3-dimethylbutenes). SPA did not readily form heavy oligomers or dialkylated benzenes and had a high propensity for the skeletal isomerization of hexenes. The alkylbenzene product selectivities could not be used to confirm that benzene alkylation always proceeded through a protonated cyclopropane (PCP) intermediate over SPA, as was found during SPA catalyzed alkylation of benzene with 1-pentene.

Butene Oligomerization by Phosphoric Acid Catalysis: Separating the Effects of Temperature and Catalyst Hydration on Product Selectivity

Solid phosphoric acid (SPA) catalysts find commercial application in olefin oligomerization and in the alkylation of aromatics with olefins. The composition of strong phosphoric acids, the hydrolysis rate of different phosphoric acid species, and the effect of temperature and hydration (composition of phosphoric acid) on butene oligomerization, as well as two case studies to show these effects on commercial operation in a Fischer−Tropsch refinery, are discussed. It was found that the hydrolysis rate of higher phosphoric acid species is much faster than that of ortho-, pyro- and triphosphoric acids (P1−P3). This implies high hydration sensitivity for SPA catalysts when operated at low hydration levels. The initial product of hydrolysis is P3, and not P1 as previously suggested, indicating additional stability of the triphosphoric acid species, possibly due to intramolecular hydrogen bonding to create a P3 cage structure. Both temperature and the degree of catalyst hydration influence catalysis. The highest yield of the best quality hydrogenated motor gasoline (highest degree of branching) was obtained when operating in a “cold and wet” mode. Decreasing catalyst hydration, irrespective of temperature, increased distillate yield. No benefit was found for “hot and wet” operation. The operating region covered by the study is 150−250 °C and 100−115% H3PO4.