P-modified Catalysts Research Articles

Hydrotreatment of fast pyrolysis liquid over Cr and P-modified catalysts with high Ni content

Hydrotreatment of birch wood pyrolysis liquid (PL) was carried out at 350 °C and 6.0 MPa initial hydrogen pressure (RT) for 4 h in a batch autoclave using promising high-loading Ni-based catalysts stabilized by SiO2. Different additives (Cu, Mo, Cr, P) were used to modify the catalysts. The products in liquid organic (OPh) and aqueous phases (AqPh) after PL hydrotreatment were characterized by different methods, such as gas chromatography-mass spectrometry (GC–MS), Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), etc. Herein, the performance of the catalysts was evaluated by considering the yield and chemical composition of the products (gaseous phase, OPhs, AqPhs, and coke). For the MoCr-containing system, a higher yield of the aqueous phase with low O/C ratio was observed that could be explained by more effective hydrodeoxygenation of water-soluble compounds due to Ni-Mo-Cr solid solutions and coordinatively unsaturated Cry+ and Mox+ sites. P-modified NiCuMoP-SiO2 and NiCrP-SiO2 catalysts reveal more intense CO2 formation very likely due to decarboxylation over Ni3P particles, thus leading to the decrease in the oxygen content in organic phase to 14 wt.%. Fresh reduced catalysts were examined by CO chemisorption, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM) to provide insights into the structure and morphology. High resistance to coke formation was evidenced according to CHNS analysis of spent samples, besides, the stability of catalysts was additionally assessed by X-ray diffraction.

P promotion on the performance of Pd-based catalyst for emission control of natural gas driven vehicles

Abstract A model catalyst for natural gas vehicles (NGVs), Ce-Pd/Al2O3 (Pd-C/A), was modified with P. The chemical properties of the catalyst were affected significantly by P modification. The P-modified catalyst (Pd-CP/A) showed better reducibility, more Pd step sites and surface PdO species. The catalysts were tested for the removal of CH4, CO and NO under simulated stoichiometric NGVs exhaust conditions. Compared to Pd-C/A, Pd-CP/A showed enhanced activity for the removal. The time on stream (TOS) results further demonstrated that the P additive was capable to stabilize Pd species in the form of active PdO, resulting in significantly improved durability for Pd-CP/A. The electronic interaction of Pd with P was found to contribute to the stabilization. The P additive could also considerably suppress the formation of PdO2 which is much less active for the reactions. Our work may provide a general approach to design highly efficient catalysts for NGVs emission control.

ZSM-5 extrudates modified with phosphorus as a super effective MTP catalyst: Impact of the acidity on binder

ZSM-5 extrudates catalyst was modified by wet-impregnation using phosphoric acid with various mass concentration (5%, 10% and 15%) and their performances were respectively evaluated in the methanol to propylene (MTP) reaction. This work focused on the changes in property of the extrudates and the interplay of P species with zeolite ZSM-5 and γ-Al2O3 binder before and after steam treatment. After introducing phosphorous acid, the surface P species was formed on the binder through P hydroxy bonding with Al hydroxy, thus allowed the decrease in number of Lewis acid sites (LAS) of binder. A small amount of P species interacted with TFAl in ZSM-5 powder, due to high silica ZSM-5 zeolite, leading to the reduction of Brønsted acid sites (BAS). For the P-modified extrudates, propylene selectivity and catalytic lifetime was improved compared to its pristine one, due to the increase of micropore area and the decrease of acid density with low ratio of strong acid sites/weak acid sites (S/W). After steaming at 500°C, the ratio of S/W on the P-modified extrudates further decreased. For the unmodified extrudates, the decrease was mainly enabled by the reduction in acid density and strong BAS, while for P-modified extrudates, the change of strong LAS of the binder to weak acid was more significant and its total LAS amount is nearly unchanged. The steamed P-modified catalyst (10wt%) showed high propylene selectivity of 47.5% and the longest lifetime of 218h at WHSV of 6h−1. The mechanism of regulating the acidity of extrudates by phosphorus modification has been proposed.

수열특성 및 기계적 안정성의 개선으로 슬러리상 CSTR에 적합한 P 첨가 알루미나 기반의 Fischer-Tropsch 합성용 코발트 촉매

Fischer-Tropsch 합성용 Co/<TEX>$Al_2O_3$</TEX> 촉매에서 알루미나 지지체에 인산 용액으로 알루미나 표면을 개질하여 촉매적 활성은 물론이고, 기계적 강도와 수열 안정성을 개선하였다. FT-IR과 같은 촉매 표면 분석법을 통하여 P 첨가로 알루미나 표면에 <TEX>$AlPO_4$</TEX> 상이 생성되어 촉매인 코발트와 지지체인 알루미나 사이의 상호작용이 약화되어 촉매의 환원도가 높아졌음을 보였다. 이에 따른 촉매성능을 평가하기 위하여 <TEX>$C_{5+}$</TEX> productivity와 turnover frequency를 계산하였다. 또한, 2 wt.% P 첨가 알루미나를 대상으로 지지체의 소성온도가 촉매활성에 미치는 영향도 살펴보았다. 한편, 고온 가압 하에서 물을 이용하여 P 첨가 알루미나(P-알루미나)를 지지체로 한 촉매의 수열 특성을 살펴보았으며, 실험 전후의 XRD 패턴을 분석함으로써 P 첨가 알루미나 기반 촉매가 수열 안정성이 우수하다는 것을 증명하였다. 뿐만 아니라, 촉매의 기계적 강도를 측정하기 위하여 유동화 반응기를 직접 제작하여 P-알루미나 기반 촉매의 P 함량이 증가할수록 마모도가 감소함을 확인하였다. 촉매 활성, 수열 안정성, 그리고 기계적 강도를 모두 고려하면, 알루미나에 첨가된 P의 함량이 1~2 wt.% 이고, 지지체를 <TEX>$500^{\circ}C$</TEX>에서 소성하여 제조한 촉매가 가장 좋은 성능을 보였다. Phosphorus was incorporated into Co/<TEX>$Al_2O_3$</TEX> catalyst for FTS by impregnating an acidic precursor, phosphoric acid, in <TEX>${\gamma}-Al_2O_3$</TEX> support to improve the mechanical strength, the hydrothermal stability of the catalyst particle, and the catalytic performance as well. Surface characterization techniques such as FT-IR revealed that <TEX>$AlPO_4$</TEX> phase was generated on the surface of the P-modified catalyst. The addition of phosphorus was found to alleviate the interaction between cobalt and alumina surface, and to increase reducibility of catalyst. The catalytic activity such as <TEX>$C_{5+}$</TEX> productivity and turnover frequency (TOF) was calculated to evaluate catalytic performance. The influence of calcination temperature of the <TEX>$Al_2O_3$</TEX> containing 2 wt.% P on the catalytic performance was also investigated. Through hydrothermal stability test and XRD analysis, the P-modified catalyst had strong resistant to the pressurized and hot <TEX>$H_2O$</TEX>. The mechanical strength of the P-modified catalyst was also examined through an in-house fluidized-bed vessel, and it was found that the catalyst fragmentation could be successfully suppressed with P. Taken as a whole, the best performance was shown to be at 1~2 wt.% P in alumina and at the calcination temperature of <TEX>$500^{\circ}C$</TEX>.

Synthesis, Characterization, and Catalytic Activity of Phosphorus Modified H-ZSM-5 Catalysts in Selective Ethanol Dehydration

Phosphorus (P) modified H-ZSM-5 catalysts were prepared by wet impregnation method by varying P loadings from 0 to 7.43 wt % using phosphoric acid (H3PO4) as the P source. The catalysts were tested for ethanol dehydration in the temperature range of 523−723 K. The P-modified catalysts were found to be highly active and selective toward ethylene at 673 K and atmospheric pressure. In addition, the P-modified catalysts were found to be extremely stable more than 200 h without any sign of deactivation. However, the selectivity was found to be strongly dependent on several factors such as P content, reaction temperature, and space velocity (WHSV). The P-modified ZSM-5 catalysts were also found to be highly active for the dehydration of aqueous ethanol solutions (10 wt %) showing very high ethylene selectivity (above 98%) at significantly lower temperature 623 K. The catalysts were thoroughly characterized using various methods, including N2 physisorption, X-ray diffraction (XRD), Fourier transform infrared spe...

Effect of P Content on the Catalytic Performance of P-modified HZSM-5 Catalysts in Dehydration of Ethanol to Ethylene

A series of phosphorus (P) modified HZSM-5 catalysts were prepared and characterized with various techniques. These catalysts were used in dehydration of ethanol to ethylene at different temperatures. It was found that not all the P-modified catalysts favor this reaction at high temperatures. Over the catalyst with 3.4 wt% P, the main product is ethylene at 573-713 K, due to the presence of weak acid sites after P modification. When the P loading is below 3.4 wt%, ethylene and higher hydrocarbons are observed at high temperatures. As P content is above 3.4 wt%, higher reaction temperature is necessary for ethanol dehydration to ethylene.