Metal-acid Bifunctional Catalysts Research Articles

Highly active metal–acid bifunctional catalyst system for hydrogenolysis of glycerol under mild reaction conditions

Combination of active carbon supported Ru catalyst with a cation exchange resin (Amberlyst 15) exhibited much higher activity in glycerol hydrogenolysis under mild reaction conditions such as 393 K and 4 MPa H 2, than other metal–acid bifunctional catalyst systems using various zeolites, sulfated zirconia, H 2WO 4, and liquid H 2SO 4.

New progress in R&D of lower olefin synthesis

This paper gives a brief review of R&D researches for light olefin synthesis directly and indirectly from synthesis gas in the Dalian Institute of Chemical Physics (DICP). The first pilot plant test was on methanol to olefin (MTO) reaction and was finished in 1993, which was based on ZSM-5-type catalyst and fixed bed reaction. In the meantime, a new indirect method designated as SDTO (syngas via dimethylether to olefin) was proposed. In this process, metal–acid bifunctional catalyst was applied for synthesis gas to dimethylether(DME) reaction, and modified SAPO-34 catalyst that was synthesized by a new low-cost method with optimal crystal size was used to convert DME to light olefin on a fluidized bed reactor. The pilot plant test on SDTO was performed and finished in 1995. Evaluation of the pilot plant data showed that 190–200 g of DME were yielded by single-pass for each standard cubic meter of synthesis gas. For the second reaction, 1.880 tons of DME or 2.615 tons of methanol produced 1 ton of light olefins, which constitutes of 0.533 ton of ethylene, 0.349 ton of propylene and 0.118 ton of butene. DICP also paid some attention on direct conversion of synthesis gas to light olefins. A semi-pilot plant test (catalyst 1.8 l) was finished in 1995 with a CO conversion >70% and a C 2 –C 4  olefin selectivity 71–74% in 1000 h.

97/04527 Oil shock ‘imminent’ if heavies are slow or expensive to produce: Bentley, R. Energy World, June 1997, 250, 20–22

Metal–acid bifunctional catalysts containing platinum and heteropolyacids (HPA) in supported on zirconia have been employed for the selective vapor phase hydrogenolysis of glycerol to propanols (1-propanol + 2-propanol) under normal atmospheric pressure. The Pt–HPA/ZrO2 catalysts (HPAs such as silicotungstic acid (STA), phosphotungstic acid (PTA), phosphomolybdic acid (PMA) and silicomolybdic acid (SMA)) were prepared by impregnation method and the calcined catalysts were characterized by means of X-ray powder diffraction, FTIR, Raman spectroscopy, BET surface area, CO chemisorption and NH3-Temperature-programmed desorption methods. The characterization results reveal the presence of well dispersed Pt metallic phase and Keggin structure of HPAs on support. The catalytic performance during glycerol hydrogenolysis is well correlated with Pt dispersion and the acidic properties of catalysts. Among the tested catalysts, it was found that Pt–PTA/ZrO2 exhibited excellent selectivity to propanols (98%) with total glycerol conversion at 230 °C. A detailed study was made on the effect of various reaction parameters such as the influence of reaction temperature, reduction temperature, glycerol concentration, hydrogen flow rate, feed flow rate and HPA loading to unveil the optimized reaction conditions. Reaction temperature was observed to have a significant effect on the glycerol conversion and product selectivity. The spent catalysts were also characterized by the X-ray diffraction, NH3-TPD and SEM analysis to investigate the changes in catalytic performance and causes of catalyst deactivation.

The Reaction Mechanism of C6Hydrocarbons over Acid–Base Bifunctional Catalysts, TiO2–ZrO2

This study examined the relation between the acid–base properties of a binary oxide, TiO2–ZrO2, and the reaction behavior of various C6hydrocarbons over this mixed oxide. Based on experimental results, both the strong acid sites and the strong base sites performed as cracking sites and could be poisoned by doping a small amount of K2O and B2O3, respectively. It was demonstrated that the paired acid–base sites played most important roles on dehydrogenation of cyclohexane and cyclization ofn-hexane and hexene. Both the yield and selectivity of benzene increased with the relative paired acid–base amount. The results of isomerization of 1-hexene showed that the yield of the molecular isomerization increased at the expense of the double bond migration as the relative acid/base ratio increased. The results also showed that 2-hexene had a much higher aromatization rate than 1-hexene over TiO2–ZrO2catalysts. A detailed reaction mechanism of the aromatization C6hydrocarbons over an acid–base bifunctional catalyst is proposed, which was different from the mechanism of a conventional metal–acid bifunctional catalysts.