José A. Calles

Bio: José A. Calles is an academic researcher from King Juan Carlos University. The author has contributed to research in topics: Catalysis & Steam reforming. The author has an hindex of 27, co-authored 61 publications receiving 2361 citations. Previous affiliations of José A. Calles include Complutense University of Madrid.

Catalytic Conversion of Polyolefins into Liquid Fuels over MCM-41: Comparison with ZSM-5 and Amorphous SiO2−Al2O3

Abstract: The catalytic degradation of both low- and high-density polyethylene (LDPE and HDPE) and polypropylene (PP) has been investigated using MCM-41, a mesoporous aluminosilicate recently discovered, as catalyst. The results obtained have been compared to those of ZSM-5 zeolite and amorphous silica−alumina. For all the studied plastics, MCM-41 has been found more active than the amorphous SiO2−Al2O3, as a consequence of the higher surface area and the uniform mesoporosity present in the former. Compared to ZSM-5, MCM-41 exhibits a lower activity for the degradation of linear and low branched polymers (HDPE and LDPE, respectively), which can be related to the higher strength of the zeolite acid sites. However, the opposite is observed for the cracking of highly substituted plastics such as PP due to the severe steric hindrances these molecules encounter to enter into the narrow pores of the zeolite, as confirmed by molecular simulation measurements. Moreover, for the cracking of LDPE, HDPE, and PP, the selectivi...

Hydrogen production by ethanol steam reforming over Cu-Ni/SBA-15 supported catalysts prepared by direct synthesis and impregnation

Abstract: Cu-Ni/SBA-15 supported catalysts prepared by the incipient wetness impregnation method were tested in the ethanol steam reforming reaction for hydrogen production. The effect of reaction temperature and metal loading was studied in order to maximize the hydrogen selectivity and the CO2/(CO + CO2) molar ratio. The best catalytic performance was achieved at 600 °C. Products distribution was the result of the combined effects of metal particles size, metal content and Ni/Cu ratio on the catalyst. In addition, two catalysts were prepared by the method of direct insertion of Ni and Cu in the initial stage of the SBA-15 synthesis. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), N2- adsorption and inductively coupled plasma atomic emission spectroscopy (ICP-AES) results evidenced that SBA-15 materials with long range hexagonal ordering were successfully synthesized in the presence of copper and nickel salts with the (Cu + Ni) contents around 4–6 wt.%. However, lower hydrogen selectivity as well as ethanol and water conversions were obtained with catalysts prepared by direct synthesis in comparison with those prepared by incipient wetness impregnation method. Particularly, the best catalytic results were achieved with a sample impregnated with 2 and 7 wt.% of copper and nickel, respectively.

CO2 capture by solid adsorbents and their applications: current status and new trends

Abstract: In the last few years there has been a rapid growth in governmental funding and research activities worldwide for CO2 capture, storage and utilization (CSU), due to increasing awareness of the link between CO2 accumulation in the atmosphere and global warming. Among the various technologies and processes that have been developed and are emerging for CSU of CO2, solid CO2-adsorbents are widely applied. In this review, these solid CO2-adsorbents are classified into three types according to their sorption/desorption temperatures: low-, intermediate- and high-temperature adsorbents with temperatures ranging from below 200 °C, between 200–400 °C and above 400 °C, respectively. For each type of solid CO2-adsorbent, the synthesis, interaction mechanism with CO2 and sorption performance, potential applications and problems are reviewed. In the last section, several representative CO2-sorption-enhanced catalytic reactions are discussed. It is expected that this review will not only summarize the main research activities in this area, but also find possible links between fundamental studies and industrial applications.

Catalytic applications of layered double hydroxides: recent advances and perspectives

Abstract: This review surveys recent advances in the applications of layered double hydroxides (LDHs) in heterogeneous catalysis. By virtue of the flexible tunability and uniform distribution of metal cations in the brucite-like layers and the facile exchangeability of intercalated anions, LDHs-both as directly prepared or after thermal treatment and/or reduction-have found many applications as stable and recyclable heterogeneous catalysts or catalyst supports for a variety of reactions with high industrial and academic importance. A major challenge in this rapidly growing field is to simultaneously improve the activity, selectivity and stability of these LDH-based materials by developing ways of tailoring the electronic structure of the catalysts and supports. Therefore, this Review article is mainly focused on the most recent developments in smart design strategies for LDH materials and the potential catalytic applications of the resulting materials.

Thermolysis of waste plastics to liquid fuel: A suitable method for plastic waste management and manufacture of value added products—A world prospective

Abstract: The present rate of economic growth is unsustainable without saving of fossil energy like crude oil, natural gas or coal. Thus mankind has to rely on the alternate/renewable energy sources like biomass, hydropower, geothermal energy, wind energy, solar energy, nuclear energy, etc. On the other hand, suitable waste management strategy is another important aspect of sustainable development. The growth of welfare levels in modern society during the past decades has brought about a huge increase in the production of all kinds of commodities, which indirectly generate waste. Plastics have been one of the materials with the fastest growth because of their wide range of applications due to versatility and relatively low cost. Since the duration of life of plastic products is relatively small, there is a vast plastics waste stream that reaches each year to the final recipients creating a serious environmental problem. Again, because disposal of post consumer plastics is increasingly being constrained by legislation and escalating costs, there is considerable demand for alternatives to disposal or land filling. Advanced research in the field of green chemistry could yield biodegradable/green polymers but is too limited at this point of time to substitute the non-biodegradable plastics in different applications. Once standards are developed for degradable plastics they can be used to evaluate the specific formulations of materials which will find best application in this state as regards their performance and use characteristics. Among the alternatives available are source reduction, reuse, recycling, and recovery of the inherent energy value through waste-to-energy incineration and processed fuel applications. Production of liquid fuel would be a better alternative as the calorific value of the plastics is comparable to that of fuels, around 40 MJ/kg. Each of these options potentially reduces waste and conserves natural resources. Plastics recycling, continues to progress with a wide range of old and new technologies. Many research projects have been undertaken on chemical recycling of waste plastics to fuel and monomer. This is also reflected by a number of pilot, demonstration, and commercial plants processing various types of plastic wastes in Germany, Japan, USA, India, and elsewhere. Further investigations are required to enhance the generation of value added products (fuel) with low investments without affecting the environment. The paper reviews the available literature in this field of active research and identifies the gaps that need further attention.