Ali Goksu

Silica-supported nickel phosphide catalysts with varying Ni/P atomic ratios (12/5, 2, 1, and 0.5) and 15 wt.% Ni-loading are synthesized. The synthesized catalysts are calcined and subjected to Temperature Programmed Reduction (TPR) analysis to evaluate Hydrogen consumption. Pre-reaction X-ray diffraction (XRD) analysis is performed on all calcined samples after reduction and passivation. The reduced catalysts are tested for the reverse water-gas shift reaction and post-reaction XRD analysis is performed on them. Stability tests are conducted on catalysts with Ni/P atomic ratios of 12/5 and 2, followed by XRD analysis of post-stability samples. The elemental composition of the catalysts at each stage is evaluated via inductively coupled plasma mass spectroscopy (ICP-MS) analysis. All experimental data is made available for re-use through this platform.

Kinetic studies on the quality alters of couscous are crucial to the suitable design of ohmic heating treatment. Hence, it was targeted to build mathematical models to forecast the changes in quality attributes of couscous cooked using ohmic heating (OH) in the present study. In addition, the average power and total energy for cooking couscous with OH at a voltage gradient of 17 V/cm were determined. Three dissimilar kinetic models—zero, first, and second—were fitted to the data. Our findings showed that, for the ohmic heating system, as cooking time increased, energy consumption increased while heating system efficacy declined. The best model to reflect the changes in color parameters was the second-order model, while the zero-order model best fit the experimental data observed for the cooking loss, moisture content, and weight increase (%). For all TPA parameters, however, neither model yielded the greatest fit.

Nickel phosphide catalysts show a high level of selectivity for the reverse water-gas shift (RWGS) reaction, inhibiting the competing methanation reaction. This work investigates the extent to which suppression of methanation can be controlled by phosphidation and tests the stability of phosphide phases over 24-hour time on stream. Herein the synthesis of different phosphide crystal structures by varying Ni/P atomic ratios (from 0.5 to 2.4) is shown to affect the selectivity to CO over CH 4 in a significant way. We also show that the activity of these catalysts can be fine-tuned by the synthesis Ni/P ratio and identify suitable catalysts for low temperature RWGS process. Ni 12 P 5-SiO 2 showed 80–100% selectivity over the full temperature range (i.e., 300–800 • C) tested, reaching 73% CO 2 conversion at 800 • C. Ni 2 P-SiO 2 exhibited CO selectivity of 93–100% over a full temperature range, and 70% CO 2 conversion at 800 • C. The highest CO 2 conversions for Ni 12 P 5-SiO 2 at all temperatures among all catalysts showed its promising nature for CO 2 capture and utilisation. The methanation reaction was suppressed in addition to RWGS activity improvement through the formation of nickel phosphide phases, and the crystal structure was found to determine CO selectivity, with the following order Ni 12 P 5 >Ni 2 P > Ni 3 P. Based on the activity of the studied catalysts, the catalysts were ranked in order of suitability for the RWGS reaction as follows: Ni 12 P 5-SiO 2 (Ni/P = 2.4) > Ni 2 P-SiO 2 (Ni/P = 2) > NiP-SiO 2 (Ni/P = 1) > NiP 2-SiO 2 (Ni/P = 0.5). Two catalysts with Ni/P atomic ratios; 2.4 and 2, were selected for stability testing. The catalyst with Ni/P ratio = 2.4 (i.e., Ni 12 P 5-SiO 2) was found to be more stable in terms of CO 2 conversion and CO yield over the 24-hour duration at 550 • C. Using the phosphidation strategy to tune both selectivity and activity of Ni catalysts for RWGS, methanation as a competing reaction is shown to be no longer a critical issue in the RWGS process for catalysts with high Ni/P atomic ratios (2.4 and 2) even at lower temperatures (300–500 • C). This opens up potential low temperature RWGS opportunities, especially coupled to downstream or tandem lower temperature processes to produce liquid fuels.

This study is to investigate the performance properties during the extraction of pectin from grapefruit peel powder using ohmic heating. Pectin extraction was carried out under different voltage gradients (7–11 V/cm), different solid: liquid ratios (1:20–1:60), and different holding times (0–180 min) at constant pH and temperature (80°C). The voltage gradient and solid: liquid ratio affected the time to reach the target temperature. The highest energy efficiency value for all voltage gradients and solid: liquid ratios were obtained in the 0 min holding time, and the efficiency value, which changed between 89.47% and 56.02%, was negatively affected by the increase in the holding time. The exergy efficiency was lower than the energy efficiency and decreased due to the increasing holding time and decreasing voltage gradient. Also, the exergy efficiency was found to be between 73.69% and 18.09%. Determining the performance characteristics of the system will make a significant contribution to pilot and industrial‐scale system/process applications for the future. Practical application In this study, pectin was successfully obtained from grapefruit powder using an ohmic heating system. The operating conditions for the obtained pectin include constant pH (pH:1) and temperature (80°C) but various voltage gradients, solid: liquid ratios, and extraction times. It has been observed that voltage gradient and extraction time were effective on energy efficiency. When looking at exergy efficiency, voltage gradient, solid: liquid ratio, and extraction time were effective. It has been observed that the improvement potential (IP) value calculated for the system decreases depending on the increasing voltage gradient. The results obtained in this study are thought to be an important data source for literature, pilot, and industrial‐scale production systems. It has been realized that ohmic heating, which is increasingly used, is an alternative technique for pectin production.

In this study, the evaporation of apple juice was completed with ohmic heating to eliminate some problems with conventional evaporation methods. Ohmic evaporation (OE) was performed at different voltage gradients (13–17 V/cm) for determining electrical conductivity (EC), Hydroxymethylfurfural (HMF), and the total phenolic content (TPC) changes. The voltage gradient affected the total consumed energy, average power, and specific water removal ratio (SWRR) values (p 

Gelişen teknolojik durumlara bağlı olarak, insanların alternatif ısıtma yöntemleri kullanma eğilimleri artmaktadır. Mevcut çalışmada, limon kabuğu tozundan, 3 farklı asit türü (sülfirik, hidroklorik ve nitrik asit) kullanılarak ayarlanmış sabit pH 1.5 değerinde, sabit katı:sıvı oranında (1:40) ve 10 V/cm voltaj gradyanında 20 °C den 80 °C ye kadar ısıtılması ve 80 °C ekstraksiyon sıcaklığında 10 dakikalık işlem süresi sonunda elektriksel iletkenlik değerinin değişimini ve asit türünün pektin verimi üzerine etkisinin incelenmesi amaçlanmıştır. Yapılan değerlendirme sonucunda, örneklerin ohmik ısıtma destekli ekstraksiyon sisteminde ısınma sürelerinin 199 ile 252 s arasında değiştiği, elektriksel iletkenlik değerinin ise 0.89 ile 2.10 S/m arasında değiştiği belirlenmiştir. Ek olarak, sıcaklık değeri arttıkça 3 farklı asit türü içinde elektriksel iletkenlik değerinin artış gösterdiği tespit edilmiştir. Bunun yanı sıra ohmik ısıtma destekli ekstraksiyon işlemi kullanılarak 3 farklı asit türü için % pektin verimi değerlerinin %8.88 ile %10.72 arasında değiştiği ve en yüksek pektin veriminin sülfürik asit çözeltisi kullanılarak gerçekleştirilen ekstraksiyon işleminde elde edilmiştir. Farklı asit türü kullanımının ısınma süresi, elektriksel iletkenlik ve pektin verimi üzerine anlamlı bir etkiye sahip olduğu (p0.05). Elde edilen bulgular sonucunda ohmik ısıtma destekli ekstraksiyon sistemi kullanılarak pektin ekstraksiyon işleminin başarılı bir şekilde yapılabileceği tespit edilmiştir. Güncel ısıtma yöntemlerinin bu tarz ürünlerin ekstraksiyonunda kullanılmasının literatüre ciddi katkı sağlaması beklenmektedir. Depending on the developing technology, people's use of alternative heating methods is increasing. In the present study, a solution of lemon peel powder prepared with 3 different acids (sulphuric, hydrochloric, and nitric acid) was heated from 20 °C to 80 °C at a constant pH of 1.5, solid: liquid ratio (1:40), and a voltage gradient of 10 V/cm. It is aimed to investigate the change of electrical conductivity value and the effect of acid type on pectin yield at the end of 10 minutes of processing time at 80 °C extraction temperature. As a result of the experiments, the heating times of the samples in the ohmic heating-assisted extraction system varied between 199 and 252 s, and the electrical conductivity values varied between 0.89 and 2.10 S/m. In addition, the electrical conductivity value increased in 3 different acid types as the temperature value increased. Also, pectin yield values for 3 different acid types varied between 8.88% and 10.72%, and the highest pectin yield was obtained in the extraction process obtained from the solution prepared with sulfuric acid. It was determined that the use of different acid types had a significant effect on the heating time, electrical conductivity, and pectin yield (p0.05). According to the results, it has been determined that pectin extraction can be done successfully using the ohmic heating-assisted extraction system. It is expected that the data obtained from the use of current heating methods in the extraction of such products will make a serious contribution to the literature.

Bulgur is a nutritious, healthy, and partially cooked food product with long shelf life and produced from wheat grains. In the present study, ohmic heating (OH) was used to cook bulgur as an alternative method to conventional cooking in case of bulgur pilaf due to its advantages including shorter heating time, uniform heat distribution in food, and higher energy efficiency. Bulgur was cooked in 0.1% salt solution to evaluate the effect of OH at various voltage gradients (10, 13, 16, and 19 V/cm) and conventional cooking processes on the textural properties of bulgur and energy consumption. The results showed that for the OH process, the total energy consumption for the cooking of bulgur reduced by approximately 80% compared to that for conventional cooking. In addition, the voltage gradients were significantly related to the cooking time, a crucial parameter for the water absorption of bulgur (p < 0.05). Novelty Impact Statement Pre-cooked bulgur must be cooked in water by using electric or flame equipment before consumption. Nevertheless, in these systems, the cooking process consumes a pretty long time and causes a vast amount of waste energy. Therefore, alternative methods are needed to save time and energy. Thus, the ohmic heating was used as an alternative cooking process for bulgur prior to consumption.

The ohmic heating process is one of the novel electrical heating methods that are considered as fast, homogeneous and efficient heating. In this study, the details of the relationship between electrical conductivity (EC)-Temperature (Temp) and ECpH-Temp at different Total Soluble Solid Content (TSSC) and different pH values were examined. Especially, the study explains details of the electrical conductivity value due to pH change (2, 2.5, 3, 3.5) and expressing EC change depending on the pH value of fruit and vegetable juices. At constant pH, EC values decrease with increasing TSSC values (10%, 20%, 30%, 40%, 50%, 60%) and decrease with increasing pH at constant TSSC value. When the relationship between Temp-EC is analyzed that the EC value increases as Temp increases in all cases and this increase is linear. It was found that the Temp-EC relationship was in high compatibility with an R2 value above 0.97. Also, in the Temp-ECpH relationship, the R2 value was found to be an acceptable value above 0.95. Key words: Ohmic heating, electrical conductivity, pH, TSSC, mathematical model.

Couscous has been widely eaten around the world because it has a low glycemic index, is low in fat, and is simple to prepare. However, it should be cooked before consumption. Therefore, novel heating methods, such as ohmic heating, can be used to cook couscous. This study aimed to investigate the potential use of ohmic heating at a voltage gradient of 17 V/cm to cook couscous and compare it with the conventional cooking method. To determine the effect of ohmic heating and conventional methods on the quality properties (color, texture profile analysis, cooking loss, moisture content, and weight increase (%)) of couscous, samples were cooked in a 0.1% salt solution. The samples were analyzed at different cooking times (4, 8, 12, and 16 min). The results obtained in the present study revealed that the total color difference also increased with an increase in cooking time. In addition, similar trends were observed for cooking loss, moisture content, and weight gain. Furthermore, the couscous samples treated with ohmic heating and conventional heating methods were completely cooked after 12 minutes. Overall, compared to the conventional cooking method, the ohmic heating process did not induce any negative effects on the quality parameters of couscous.

Climate change is becoming increasingly more pronounced every day while the amount of greenhouse gases in the atmosphere continues to rise. CO2 reduction to valuable chemicals is an approach which has gathered substantial attention as a means to recycle these gases. Herein we explore some of the tandem catalysis approaches that can be used to achieve transformation of CO2 to C-C coupled products, focusing especially on tandem catalytic schemes where there is a big opportunity to improve performance by designing effective catalytic nanoreactors. Recent reviews have highlighted the technical challenges and opportunities for advancing tandem catalysis, especially highlighting the need for elucidating structure-activity relationships and mechanisms of reaction through theoretical and in situ/operando characterization techniques [1–3]. In this review, we focus on nanoreactor synthesis strategies as a critical research direction, and discuss these in the context of two main tandem pathways (CO-mediated pathway and Methanol-mediated pathway) to C-C coupled products.