Gas Phase Hydrogenation Of Maleic Anhydride Research Articles

Highly selective conversion of maleic anhydride to γ-butyrolactone over Ni-supported catalysts prepared by precipitation–deposition method

The gas-phase hydrogenation of maleic anhydride over Ni catalysts supported on SiO2 and SiO2–Al2O3, prepared by incipient wetness impregnation (I) and constant-pH precipitation–deposition (PD), was studied. The samples were characterized by N2 adsorption at −196°C, X-ray diffraction, temperature-programmed reduction, H2 chemisorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. The catalytic tests were carried out at atmospheric pressure, between 170 and 220°C and using a space-time of 12 ghmol−1. From the characterization results, it was determined that the interaction between Ni2+ species and the support strongly depends on the preparation method. The trend found for the Ni2+-support interaction was Ni/SiO2-PD >Ni/SiO2-Al2O3-PD > Ni/SiO2-I. After reduction in H2 flow, metal Ni particles were one order of magnitude smaller in catalysts prepared by precipitation–deposition than those prepared by impregnation. All catalysts were active for the hydrogenation of maleic anhydride (MA) into succinic anhydride (SA) and subsequent hydrogenolysis to γ-butyrolactone (GBL) and propionic acid (PA). Regardless of small amounts of CH4, no other products were detected at the reactor outlet. However, the activity and selectivity to GBL depends on the metal particle size, Ni-support interaction and the presence of Lewis acid sites on SiO2–Al2O3 surface. It was found that the small metallic particles obtained by precipitation–deposition method are more active and selective to GBL than the large particles formed using the impregnation method. The highest GBL yield (83%) was reached at 220°C with Ni/SiO2–Al2O3–PD, which is attributed to selective hydrogenolysis of SA adsorbed on Lewis acid sites by spillover of hydrogen chemisorbed on neighboring metal nickel nanoparticles.

Gas-phase hydrogenation of maleic anhydride to γ-butyrolactone over Cu-CeO2-Al2O3 catalyst at atmospheric pressure: Effects of the residual sodium and water in the catalyst precursor

Cu-CeO2-Al2O3 catalysts were prepared by the co-precipitation method with different washing operations during the preparation process for the purpose of controlling the contents of the residual sodium and water in the catalyst precursors. Cu-CeO2-Al2O3 catalysts were characterized by ICP-AES, XRD, SEM, nitrogen sorption, N2O chemisorption, Raman spectroscopy and H2-TPR. Effects of the residual sodium and water in the catalyst precursor on the catalytic performance of Cu-CeO2-Al2O3 catalyst for gas-phase hydrogenation of maleic anhydride to γ-butyrolactone at atmospheric pressure, and the structure–activity relationships were investigated. The results show that the residual water and sodium in the form of Na2CO3 in the catalyst precursor lead to a decrease in Cu dispersion and Cu surface area, which is disadvantageous to the catalytic performance and stability. Washing step of the residual sodium in the catalyst precursor with the deionized water and then removing step of the residual water using azeotropy distillation shows a great improvement in the stability of Cu-CeO2-Al2O3 catalyst, in which 100% of conversion of maleic anhydride and 100% of selectivity to γ-butyrolactone were maintained for 12h.

Effect of promoters on Cu–ZnO–SiO2 catalyst for gas-phase hydrogenation of maleic anhydride to γ-butyrolactone at atmospheric pressure

Cu-ZnO-SiO2 (CZS) catalysts, prepared by the coprecipitation method, were investigated for gas-phase hydrogenation of maleic anhydride (MA) to γ-butyrolactone (GBL) at atmospheric pressure and characterized by XRD, N2O chemisorption, SEM and TGA. Effects of the compositions and the promoters on the catalytic performance and stability of CZS catalysts were investigated, in which CZS111 catalyst with the molar ratio of Cu:Zn:Si=1:1:1 showed better catalytic performance and stability. The results show that the introduction of Ba as a promoter to CZS111 catalyst can further improve greatly the catalyst stability by increasing Cu surface area and ZnO dispersion with more additional adsorption sites for succinic anhydride (SA) to suppress the adsorption and polymerization of SA on the active sites of Cu0. The possible reaction pathways were proposed for gas-phase hydrogenation of MA to GBL, which could explain well the effect of Ba as a promoter on the stability of CZS111 catalyst.

Gas phase hydrogenation of maleic anhydride at low pressure over silica-supported cobalt and nickel catalysts

The gas-phase hydrogenation of maleic anhydride over Ni/SiO2 and Co/SiO2 catalysts, prepared by the incipient wetness impregnation method, was studied. The catalytic tests were carried out at 1bar pressure, between 170 and 220°C and W/FMA0 in the range 5–25ghmol−1. In this work, the product distribution was different to those obtained at high pressures, previously reported in the open literature. Both Ni/SiO2 and Co/SiO2 catalysts were active for the selective hydrogenation of maleic anhydride (MA) into succinic anhydride (SA). Subsequently, SA was converted to γ-butyrolactone (GBL) and propionic acid (PA). Neither tetrahydrofurane nor butanediol were detected at the reactor outlet. GBL/PA ratio was strongly depending on the metallic catalyst and temperature. At 170°C, Ni/SiO2 was more selective to GBL than Co/SiO2. Besides, with Ni/SiO2, GBL formation rate diminished during the experiment while PA production showed a small increase. Instead, over Co/SiO2, both the PA and GBL formation rate decayed with time on stream. At 220°C, Co/SiO2 showed a higher initial selectivity to GBL than Ni/SiO2. However, the GBL formation rate diminished more rapidly with Co/SiO2 than with Ni/SiO2. Thus, both catalysts gave similar selectivity to GBL after 3h reaction at 220°C. The observed catalyst deactivation was attributed to carbonaceous species of different nature deposited on the metallic phase during reaction. The amount and type of these species depends on both metal catalysts and reaction conditions. Selectivity and stability of Ni/SiO2 and Co/SiO2 catalysts is explained on the basis of their hydrogenolytic activity.

Gas-phase hydrogenation of maleic anhydride to γ-butyrolactone at atmospheric pressure over Cu–CeO 2–Al 2O 3 catalyst

Cu–CeO 2–Al 2O 3 catalyst, prepared by co-precipitation method, was investigated for the gas-phase hydrogenation of maleic anhydride (MA) to γ-butyrolactone (GBL) at atmospheric pressure and the catalyst deactivation was also studied. Effects of catalyst composition, reaction temperature, and liquid hourly space velocity (LHSV) of raw material on the catalytic performance of Cu–CeO 2–Al 2O 3 catalyst were investigated. The catalyst (molar ratio of Cu:Ce:Al = 1:1:2) showed better catalytic performance, in which both the conversion of MA and the selectivity of GBL kept 100% within two hours under the reaction conditions of 6 mL catalyst, 0.1 MPa, 220–280 °C, 30 mL min −1 H 2, 0.6 h −1 LHSV of 20 wt.% MA/GBL. As for Cu–CeO 2–Al 2O 3 catalyst, smaller crystallite size of Cu and higher Cu surface area are favorable to increase its catalytic performance. The deactivation of Cu–CeO 2–Al 2O 3 catalyst is due to formation of the compact wax-like deposition on the catalyst surface, which is probably ascribed to the strong adsorption of succinic anhydride and then polymerization on the catalyst surface. The catalytic performance of the regenerated catalyst can be recovered completely by the regeneration method of N 2–air–H 2 stage treatment.

Deactivation and regeneration of Cu/SiO 2 catalyst in the hydrogenation of maleic anhydride. Kinetic modeling

In this work, the deactivation of a Cu(10%)/SiO 2 catalyst in the gas-phase hydrogenation of maleic anhydride ( MA) was studied. The reaction was performed between 170 and 220 °C, at atmospheric pressure and using two contact times ( W / F M A 0 ) : 11.9 and 23.8 g cat. h/mol MA. The Cu(10%)/SiO 2 catalyst was prepared by the wetness impregnation method and characterized by N 2 physisorption at −196 °C, N 2O decomposition at 90 °C, X-ray diffraction and temperature programmed reduction. From this characterization, it was concluded that catalyst is formed by large metal copper crystallites with little or none interaction with silica surface. Under the conditions used in this work, the Cu(10%)/SiO 2 catalyst was highly selective to succinic anhydride ( SA) while MA conversion dropped drastically with time. Both high selectivity to SA and rapid catalyst deactivation can be explained considering different types of MA interaction with the large metal copper crystallites. Catalyst regeneration feasibility under two different atmospheres, oxidizing and reducing, was also analyzed. The experimental results were successfully fitted, by non-linear regression, using a deactivation model with residual activity ( DMRA). This model predicts satisfactorily the deactivation of Cu(10%)/SiO 2 in the gas-phase hydrogenation of MA, both for fresh and regenerated catalysts, under the experimental conditions used in this work.

Gas-phase hydrogenation of maleic anhydride to butyric acid over Cu/TiO 2/γ-Al 2O 3 catalyst promoted by Pd

The promoter effect of palladium on the Cu/TiO 2/γ-Al 2O 3 catalyst was investigated for the gas-phase selective hydrogenation of maleic anhydride to butyric acid at atmospheric pressure. The results show that Pd is added rarely into the Cu/TiO 2/γ-Al 2O 3 catalyst for the hydrogenation of maleic anhydride, the higher selectivity to butyric acid can be obtained. In the absence of Pd (or Cu) in the Cu–Pd/TiO 2/γ-Al 2O 3 catalyst, the selectivity to butyric acid (BA) is nearly zero. Using the Cu–Pd/TiO 2/γ-Al 2O 3 (Pd/Cu=3/100 (atom)) catalyst, 56.2% selectivity to BA and 100% conversion of maleic anhydride were obtained at 280 °C.