Andrzej Borodzinski

Selective Hydrogenation of Ethyne in Ethene‐Rich Streams on Palladium Catalysts. Part 1. Effect of Changes to the Catalyst During Reaction

The effect of various changes to the palladium catalyst during its stabilization in the course of the selective hydrogenation of ethyne‐ethene mixtures (formation of hydride and carbide phases and of carbonaceous deposits) was reviewed. The deposits in the form of a carbonaceous overlayer on the palladium surface create sites at which selective ethyne hydrogenation to ethene can occur. The carbonaceous deposit on the support increases the selectivity to ethane formation by increasing the rate of ethene hydrogenation on support sites (spillover of hydrogen from metal to the support surface) and by decreasing the effective diffusivity of ethyne in the pores.

Selective Hydrogenation of Ethyne in Ethene‐Rich Streams on Palladium Catalysts, Part 2: Steady‐State Kinetics and Effects of Palladium Particle Size, Carbon Monoxide, and Promoters

Developments in the last three decades of kinetics of selective hydrogenation of ethyne in ethene‐rich streams on palladium catalysts are reviewed. Most of the studies can be described comprehensively by a model that assumes carbonaceous deposits (i) create irreversibly on the palladium surface small A types of active site (selective to ethene) and large E types of active site (selective to ethane), and (ii) are involved in hydrogenation of ethene on E s sites on the support. The relative importance of these sites, with varying (i) reaction conditions, (ii) palladium dispersion, (iii) process modifiers, and (iv) promoters, is discussed.

The kinetic model of hydrogenation of acetylene–ethylene mixtures over palladium surface covered by carbonaceous deposits

Abstract The kinetics of hydrogenation reactions of acetylene–ethylene mixtures over a Pd/α-Al 2 O 3 commercial catalyst was studied. Reaction rates were measured by using a gradientless reactor. The kinetic expressions derived, based upon a mechanism involving two types of active sites produced on the palladium surface by carbonaceous deposits, were used for the interpretation of experimental results. The kinetic parameters in these equations and in recently published kinetic expressions were estimated by using multiresponse technique. Statistical analysis of regression showed that the proposed kinetic model describes the process more adequately than do the competitive models.

A novel-design camera for simultaneous X-ray and kinetic studies

Abstract A novel-designed camera for simultaneous X-ray and kinetic studies was developed. The camera was used for studying the phase transformation and reaction kinetics in the hydrogenation of acetylene-ethylene mixture on Pd/Al 2 O 3 catalysts.

Synthesis and Electrocatalytical Application of Hybrid Pd/Metal Oxides/MWCNTs

The performance of Pd electrocatalysts for formic acid electrooxidation was improved by application of metal oxide-multiwall carbon nanotubes composites as a catalyst support. Hybrid oxides/MWCNTs were synthesized by two different methods: chemical reduction method and impregnation method. Pd based catalysts were synthesized by polyol method on the MWCNTs or oxide/MWCNTs composites. The In2O3 was deposited on MWCNTs by impregnation method (In2O3/MWCNTs-IM support) and in the presence of NaBH4 (In2O3/MWCNTs-NaBH4 support). The physical properties of the Pd/In2O3/MWCNTs-IM, Pd/In2O3/MWCNTs-NaBH4, Pd/SnO2/MWCNTs, and Pd/MWCNTs catalysts were characterized and their electrocatalytical performance in formic acid oxidation was compared. During Pd deposition on In2O3/MWCNTs-NaBH4 support, InPd2 structure was formed as observed by XRD. The electrochemical tests indicate that the two Pd/ In2O3/MWCNTs electrocatalysts have higher electrocatalytic activity than those of Pd/SnO2/MWCNTs and Pd/MWCNTs. The best performance was observed for the catalyst obtained by In2O3 impregnation of MWCNTs denoted by Pd/In2O3/MWCNTs-IM.

Synthesis and Characterization of PANI-MWCNTs Supported Nano Hybrid Electrocatalysts

Among new energy systems, fuel cells are electrochemical devices transforming chemical energy directly into electrical energy. In our previous works, MWCNTs (the multi walled carbon nanotubes) supported palladium anodic electrocatalysts for DFAFCs (direct formic acid fuel cells) have been studied. MWCNTs can be modified by appropriate oxides, for example, cerium oxide, zirconium oxide and N-doped titanium dioxide, to enhance the electrocatalytic performance of the catalysts. But the oxides and the defects of the acid oxidized MWCNTs, denoted as AO-MWCNTs, can cause the electron capture and reduce both the catalyst conductivity and the catalysts activity. In order to improve the conductive properties of the support, in the present work a conductive polymer was introduced to modify the surface of carbon nanotubes. PANI (polyaniline) has a long-chain structure and conjugated structure and exhibits good conductivity, high stability, and is non-toxic. After PANI modification, AO-MWCNTs can provide efficient electronic conduction network. In this study, PANI modified AO-MWCNTs were prepared via polymerization process. AO-MWCNTs were homogeneously coated with PANI to obtain composite with weight ratio 50:50 PANI to MWCNTs. The thickness of the PANI layer was 4-9 nm. It was shown that the photosynthesis process is a better method to reduce Pd on PANI/AO-MWCNTs than by using NaBH4. By adjusting pH value to 9, during preparation of Pd/PANI/AO-MWCNTs composites by X-ray irradiation process, smaller Pd particles were obtained and PANI deprotonation was avoided which explains better activity of this composite in formic acid electro oxidation.

Synthesis and Characterization of Nano-hybrid Noble Metals/N doped TiO 2 /MWCNTs Electrocatalysts

Novel metal catalysts are easily poisoned by CO adsorption or leaching in oxidation of formic acid that leads to decrease the performances of catalyst. To increase the catalyst activity and poison tolerance in fuel cells, novel metal nanoparticles are usually supported on modified support materials to enhance its performance. In this study, TiO2/MWCNTs are synthesized by sol-gel method. Also, ammonium is used to dope nitrogen into TiO2 to modify its electrical and chemical property. MWCNTs, TiO2/MWCNTs and N-doped TiO2/MWCNTs are three supporters using in this study to examine the effects of supporters on the electrocatalytic performance of Pd and AuPd catalysts. The synthesized metal nanoparticles are uniformly dispersed on the surfaces of MWCNTs, TiO2 and N-doped TiO2 modified MWCNTs. The electrochemical analysis illustrate that Pd/N-doped TiO2/MWCNTs (molar ratio of NH4OH:TiO2=4:1) catalyst exhibits higher activity and better stability than that of Pd/MWCNTs either/or Pd/TiO2/MWCNTs catalyst in formic acid electrooxidation. Same results are observed in AuPd series of catalyts. It indicates that suitable N-doping TiO2 improves dramatically on the performance of Pd or AuPd-based catalysts in electrochemical reaction. Thus, hybrid AuPd/N-doped TiO2/MWCNTs (molar ratio of NH4OH:TiO2=4:1) materials have potentially to be used in the direct formic acid fuel cells (DFAFCs) in the future. Keywords—Fuel cells, Formic Acid, Pd, AuPd, N-doped TiO2, catalyst, MWCNTs