Sorption kinetics for the removal of aldehydes from aqueous streams with extractant impregnated resins

The sorption kinetics for the removal aldehydes from aqueous solutions with Amberlite XAD-16 and MPP particles impregnated with Primene JM-T was investigated. A model, accounting for the simultaneous mass transfer and chemical reaction, is developed to describe the process. It is based on the analogy to the diffusion and reaction in a stagnant liquid sphere, but corrected for the porosity and particle properties influencing the diffusion. The developed model describes the kinetic behavior of the process in the low concentration region rather well. However, in the high concentration region, larger discrepancies are observed. Initially, the influence of the flow rate was investigated to eliminate the effect of the external mass transfer. The influence of the particle morphology was investigated for both physical and reactive sorption. Physical sorption experiments were used to determine the factor τ that takes the particle properties influencing the diffusion into account. It was shown that the diffusion is faster in XAD-16 than in MPP impregnated systems. Reaction rate constant kx was determined by fitting the model to the experimental data. Sorption of benzaldehyde appears to be significantly slower (kx ~ 10−4 l/mol s) than the sorption of pentanal (kx ~ 10−3 l/mol s) due to the slower chemical reaction. The influence of the particle size was investigated for the sorption of pentanal with XAD-16. It was observed that the particle size does influence the diffusion term, but does not have an effect on the reaction rate. On the other hand, the extractant loading influences the reaction rate slightly in the low concentration region, whereas the initial concentration of the solute has more pronounced effect

Industrial Process Design for the Production of Aniline by Direct Amination

The objective is to design a plant from raw material to product for the production of aniline by direct amination of benzene. The process design is started on a conceptual level and ended on a basic engineering level as well as a techno-economical evaluation. The amination of benzene by hydroxylamine was used as basis. For the production of hydroxylamine four routes are proposed. The most promising route is the chemical reduction of nitric oxide with hydrogen. The process evaluation shows that 27 % of the atomic nitrogen is lost. The atomic carbon efficiency is close to unity. Furthermore, a significant amount of steam can be produced. From an economical perspective, there is still room for improvement because the return of investment is quite low and the payback period is quite high

Selection and evaluation of adsorbents for the removal of anionic surfactants from laundry rinsing water

Low-cost adsorbents were tested to remove anionic surfactants from laundry rinsing water to allow re-use of water. Adsorbents were selected corresponding to the different surfactant adsorption mechanisms. Equilibrium adsorption studies of linear alkyl benzene sulfonate (LAS) show that ionic interaction results in a high maximum adsorption capacity on positively charged adsorbents of 0.6–1.7 g LAS/g. Non-ionic interactions, such as hydrophobic interactions of LAS with non-ionic resins or activated carbons, result in a lower adsorption capacity of 0.02–0.6 g LAS/g. Negatively charged materials, such as cation exchange resins or bentonite clay, have negligible adsorption capacities for LAS. Similar results are obtained for alpha olefin sulfonate (AOS). Cost comparison of different adsorbents shows that an inorganic anion exchange material (layered double hydroxide) and activated carbons are the most cost-effective materials in terms of the amount of surfactant adsorbed per dollar worth of adsorbent.

Kinetic analysis of anionic surfactant adsorption from aqueous solution onto activated carbon and layered double hydroxide with the zero length column method

Low cost adsorption technology offers high potential to clean-up laundry rinsing water. From an earlier selection of adsorbents, layered double hydroxide (LDH) and granular activated carbon (GAC) proved to be interesting materials for the removal of anionic surfactant, linear alkyl benzene sulfonate (LAS), which is the main contaminant in rinsing water. The main research question is to identify adsorption kinetics of LAS onto GAC-1240 and LDH. The influence of pre-treatment of the adsorbent, flow rate, particle size and initial LAS concentration on the adsorption rate is investigated in a zero length column (ZLC) set-up. The rate determining step is obtained by fitting an adsorption model and an ion exchange model describing intraparticle diffusion to the experimental data. GAC-1240 is well described with the adsorption model following Fick's second law. The effective diffusion coefficient of GAC-1240 is 1.3 × 10−10 ± 0.2 × 10−10 m2/s and is not influenced by particle sizes or initial LAS concentrations. The ion exchange of LAS onto LDH is not well described by the ion exchange model. The rate determining step is obtained by comparing several models to different experimental data. A double layer model resulted in a good description of the experimental data. At the outer surface of LDH a stagnant film resistance originating from an electric double layer is assumed. The double layer mass transfer coefficient is 7 × 10−5 ± 2 × 10−5 m/s

Optimization of layered double hydroxide stability and adsorption capacity for anionic surfactants

Low cost adsorption technology offers high potential to clean up laundry rinsing water. From an earlier selection of adsorbents (Schouten et al. 2007), layered double hydroxide (LDH) proved to be an interesting material for the removal of anionic surfactant, linear alkyl benzene sulfonate (LAS) which is the main contaminant in rinsing water. The main research question was to identify the effect of process parameters of the LDH synthesis on the stability of the LDH structure and the adsorption capacity of LAS. LDH was synthesized with the co-precipitation method of Reichle (1986); a solution of M2+(NO3)2 and M3+(NO3)3 and a second solution of NaOH and Na2CO3 were pumped in a beaker and mixed. The precipitate that was formed was allowed to age and was subsequently washed, dried and calcined. The process parameters that were investigated are the concentration of the initial solutions, M2+/M3+ ratio and type of cations. The crystallinity can be improved by decreasing the concentration of the initial solutions; this also decreases the leaching of M3+ from the brucite-like structure into the water. The highest adsorption capacity is obtained for Mg2+/Al3+ with a ratio 1 and 2 because of the higher charge density compared to ratio 3. Storing the LDH samples in water resulted in a reduction of adsorption capacity and a decrease in surface area and pore volume. Therefore, LDH is not applicable in a small device for long term use in aqueous surroundings. The adsorption capacity can be maintained during storage in a dry N2 atmosphere

Hydrogenation of carbon dioxide for methanol production

A process for the hydrogenation of CO2 to methanol with a capacity of 10 kt/y methanol is designed in a systematic way. The challenge will be to obtain a process with a high net CO2 conversion. From initially four conceptual designs the most feasible is selected and designed in more detail. The feeds are purified, heated to 250 °C and fed to a fluidized bed membrane reactor equipped with a Cu/ZnO/Al2O3 catalyst. Zeolite membranes mainly remove the methanol and shift the equilibrium reaction towards methanol. A yield of 25 % per pass is obtained. The permeate and the water-methanol mixture from the phase separator is finally separated in a distillation column. In the final design 15.4 kt/y of carbon dioxide is needed in order to produce 10 kt/y methanol. The net CO2 reduction is about 2/3, which is significant. The process is technical but currently not economically feasible

Design and intensification of industrial DADPM process

Process intensification is an essential method for the improvement of energy and material efficiency, waste reduction and simplification of industrial processes. In this research a Process Intensification methodology developed by Lutze, Gani and Woodley at the Computer Aided Process Engineering Center (CAPEC) at DTU in Denmark is used for the intensification of the 4,4′-methylenedianiline (DADPM) process at Huntsman B.V. in the Netherlands. The goal of this research was the extension of the DTU methodology for applicability on running, industrial processes and improvement of the Huntsman process, focus is on reduction of operation costs. We have shown in the DADPM case that an analysis of the performance per section or unit operation and the mutual interactions provide essential additional information that is not being detected by the DTU method. We demonstrated how good engineering practice and heuristics can also reduce the number of process options that have to be modelled in detail. Selection of the optimal process is done based on a quantitative analysis of several intensified process options which all obey all required constraints. Equipment models were built in Excel and integrated in an Aspen Plus process flowsheet containing 27 different process options. A sensitivity analysis is done using Aspen, yielding the optimized and intensified process for DADPM production. Energy costs for the DADPM process are reduced by 24% using a combination of both heuristic and methodology-based intensification. We conclude that the method developed by Lutze et al. is a valuable tool for PI and process analysis and synthesis. The extension developed using heuristics, provides additional insight, traces the process weak points, facilitates implementation of new technology and reduces calculations