Al-modified yolk-shell silica particle-supported NiMo catalysts for ultradeep hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene:Efficient accessibility of active sites and suitable acidity

Yolk-shell SiO2 particles(YP)with center-radial meso-channels were fabricated through a simple and effective method.Al-containing YP-supported NiMo catalysts with different Al amounts(NiMo/AYP-x,x=Si/Al molar proportion)were prepared and dibenzothiophene(DBT)and 4,6-dimethyl-dibenzothiophene(4,6-DMDBT)were employed as the probes to evaluate the hydrodesulfurization(HDS)catalytic performance.The as-prepared AYP-x carriers and corresponding catalysts were characterized by some advanced characterizations to obtain deeper correlations between physicochemical properties and the HDS performance.The average pore sizes of series AYP-x supports are above 6.0 nm,which favors the mass transfer of organic sulfides.The cavity between the yolk and the shell is beneficial for the enrichment of S-containing compounds and the accessibility between reactants and active metals.Aluminum embedded into the silica framework could facilitate the formation of Lewis(L)and Brønsted(B)acid sites and adjust the metal-support interaction(MSI).Among all the as-synthesized catalysts,NiMo/AYP-20 catalyst shows the highest HDS activities.The improved HDS activity of NiMo/AYP-20 catalyst is attributed to the perfect combination of excellent structural properties of the yolk-shell mesoporous silica,enhanced acidity,moderate MSI,and good accessibility/dispersion of active components.

A Hypothesis Regarding the Origin of Additional Surface Acidity in Solid Complexes with Same Metal Cations

Based on the criteria for additional surface acidity generation in composite oxides and composite fluorides proposed by Tanabe and Kemnitz et al.A hypothesis for the origin of additional surface acidity in solid composites with the same metal cations is proposed.The surface acidsites of We analyze three types of solid composite systems,that is,CrF_(3)/Cr_(2)O_(3),MgF_(2)/MgO,and ZnF_(2)/ZnO,is systematically analyzed,which agrees with experimental results.Accordingly,the origin of additional surface acidity in these solid composites is reasonably explained,and the types of acidic sites are also predicted.

Effect of Saline Water on Soil Acidity, Alkalinity and Nutrients Leaching in Sandy Loamy Soil in Rwamagana Bella Flower Farm, Rwanda

The necessity to saline and sodic waters is sometimes used for irrigating agricultural activities under certain circumstances, but it is important to note that the use of these waters comes with specific considerations and limitations. One way to decrease undesirable effects of sodic waters on the physical and chemical properties of soils is to apply organic and chemical amendments within the soil. This study aimed to assess the effectiveness of saline water on soil acidity, alkalinity and nutrients leaching in sandy loamy soil at Bella flower farm, in Rwamagana District, Rwanda. The water used was from the Muhazi Lake which is classified as Class I (Saline water quality). Column leaching experiments using treated soils were then conducted under saturated conditions. The soil under experimental was first analyzed for its textural classification, soil properties and is classified as sandy loamy soil. The t-test was taken at 1%, 5% and 10% levels of statistical significance compared to control soil. The results indicated that the application of saline water to soils caused an increase in some soil nutrients like increase of Phosphorus (P), Potassium (K+), Magnesium (Mg2+), Sulphur (S), CN ratio and Sodium (Na+) and decreased soil texture, physical and chemical properties and remained soil nutrients. Consequently, the intensive addition of saline water leachates to soil in PVC pipes led to decreased of soil EC through leaching and a raiser Soluble Sodium Percentage (SSP). The rate of saline water application affected the increase accumulation of SAR and Na% in the top soil layers. The study indicated that saline water is an inefficient amendment for sandy soil with saline water irrigation. The study recommends further studies with similar topic with saline water irrigation, as it accentuated the alkalinity levels.

Characterization of Acidity in Acid Sulphate Soils of Kerala

The acidity characteristics of acid sulphate soils of Kuttanad, Kerala, were studied in detail by collecting surface, profile and subsurface soil samples from 20 locations of six soil series viz., Ambalapuzha, Purakkad, Thotapally, Thuravur, Kallara and - Thakazhi that belonged to acid sulphate soils. The soils were extremely acidic showing a range of pH （H：O） varying from 2.5 to 5.2. Lowest pH was recorded by Thakazhi series and the highest by Thotapally. The potential acidity of soils ranged from 14.71 cmol.kg-1 to 110.5 cmol-kg1 with Thakazhi series showing the highest value. The contribution of hydrolytic acidity to potential acidity ranged from 70.2% to 97.2%. In all soil series, exchangeable A13＋ was greater than exchangeable H~. A significant correlation was observed among pH （KCI）, pH （H20） and pH （CaCI2） in all series.

Characteristics of Soluble and Exchangeable Acidity inan Extremely Acidified Acid Sulfate Soil

An extremely acidified acid sulfate soil (ASS) was investigated to characterize its soluble and exchangeableacidity. The results showed that soluble acidity of a sample determined by titration with a KOH solutionwas much significantly greater than that indicated by pH measured using a PH meter, particularly for theextremely acidic soil samples. This is because the total soluble acidity of the extremely acidic soil sampleswas mainly composed of various soluble Al and Fe species, possibly in forms of Al sulfate complexes (e.g.,AISO4) and ferrous Fe (Fe2+). It is therefore suggested not to use pH alone as an indicator of soluble acidityin ASS, particularly for extremely acidic ASS. It is also likely that AISO4+ actively pericipated in cationexchange reactions. It appears that the possible involvement of this Al sulfate canon in the canon adsorptionhas significant effect on increasing the amount of acidity being adsorbed by the soils.

Understanding the biochar’s role in ameliorating soil acidity

Extensive acidic soils,which suffer from accelerated soil acidification,are found in southern China.Soil acidity,aluminum toxicity,and nutrient deficiencies severely limited crop productivity in acidic soils.It has been widely reported that crop residue biochars can ameliorate acidic soils and increase crop productivity.Here,we summarized the positive effects and mechanisms involved in the correction of soil acidity,the alleviation of aluminum toxicity and the increase of soil pH buffering capacity by crop residue biochars.The carbonate,oxygen-containing functional groups and silicates in biochars are the major components responsible for their efficacy in amending acidic soils and resisting soil re-acidification.We conclude that application of crop residue biochars may be a better option than traditional liming to ameliorate acidic soils.Nonetheless,further researches into soil acidification are still required to address some issues that are controversial and poorly understood.

Effects of Light Rare Earth on Acidity and Catalytic Performance of HZSM-5 Zeolite for Catalytic Cracking of Butane to Light Olefins

The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by the impregnation of the ZSM-5 type zeolites（Si/Al=64：1）with the corresponding RE nitrate aqueous solutions.The catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD,and IR spectroscopy of adsorbed pyridine.The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor.The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins,especially to propylene,thus increasing the total yield of olefins in the catalytic cracking of butane.Among the RE-modified HZSM-5 samples,Ce/HZSM-5 gave the highest yield of total olefins,and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600℃.The presence of rare earth metal on the HZSM-5 sample,not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type,that is,the ratio of L/B（Lewis acid/Brnsted acid）,but also altered the basic properties of it,which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.

Rod-shaped porous alumina-supported Cr_2O_3 catalyst with low acidity for propane dehydrogenation

Direct catalytic propane dehydrogenation(PDH)to obtain propylene is a more economical and environmentally friendly route for propylene production.In particular,alumina-supported Cr2O3 catalysts can have better potential applications if the acidic properties could be tuned.Herein,a series of rod-shaped porous alumina were prepared through a hydrothermal route,followed by calcination.It was found that the acidity of the synthesized alumina was generally lower than that of the commercial alumina and could be adjusted well by varying the calcination temperature.Such alumina materials were used as supports for active Cr2O3,and the obtained catalysts could enhance the resistance to coke formation associated with similar activity in PDH reaction compared to the commercial alumina.The amount of coke deposited on a self-made catalyst(Cr-Al-800)was 3.6%,which was much lower than that deposited on the reference catalyst(15.7%).The lower acidity of the catalyst inhibited the side reactions and coke formation during the PDH process,which was beneficial for its high activity and superior anti-coking properties.

Coking kinetics and influence of reaction-regeneration on acidity, activity and deactivation of Zn/HZSM-5 catalyst during methanol aromatization

The coking kinetics and reaction-regeneration on Zn/HZSM-5 （Zn/HZ） catalyst in the conversion of methanol to aromatics were investigated. The highest initial benzene, toluene and xylene （BTX） yield of ca. 67.7% was obtained on fresh Zn/HZ catalyst, which showed the worst catalytic stability. The cycle of reaction-regeneration significantly modified the texture and acidity of Zn/HZ catalyst, which in turn affected its catalytic performance and coking behavior in methanol conversion to BTX. The residual carbon located on the surface of Zn/HZ catalyst led to the decrease of acid sites and the change on the acid sites distribution, which played an important roles on its activity and deactivation. It was found that the high B/L ratio and the low total acid sites concentration of the Zn/HZ catalyst favored to the high BTX yield and good catalytic stability in methanol conversion.

Modifying the acidity of H-MOR and its catalytic carbonylation of dimethyl ether

Among the reactions catalyzed by zeolites there are some that exhibit high selectivity due to the spatial confinement effect of the zeolite framework.Tailoring the acidity,particularly the distribution and location of the Bronsted acid sites in the zeolite is effective for making it a better catalyst for these reactions.We prepared a series of H-mordenite（H-MOR） samples by varying the composition of the sol-gel,using different structure directing agents and post-treatment.NH3-TPD and IR characterization of adsorbed pyridine were employed to determine the amount of Bronsted acid sites in the 8-membered ring and 12-membered ring channels.It was shown that controlled synthesis was a promising approach to improve the concentration of Bronsted acid sites in MOR,even with a low Al content.Using an appropriate composition of Si and Al in the sol-gel favored a higher proportion of Bronsted acid sites in the 8-membered ring channels.HMI as a structure-direct agent gave an obvious enrichment of Bronsted acid sites in the 8-membered ring.Carbonylation of dimethyl ether was used as a probe reaction to examine the modification of the acid properties,especially the Bronsted acid sites in the 8-membered ring channels.There was a linear relationship between methyl acetate formation and the number of Bronsted acid sites in the 8-membered ring channels,demonstrating the successful modification of acid properties.Our results provide information for the rational design and modification of zeolites with spatial constraints.

Tolerance of VA Mycorrhizal Fungi to Soil Acidity

A 45-day greenhouse experiment was carried out to determine effect of vesicular-arbuscular (VA) mycorrhizal fungi on colonization rate, plant height, plant growth, hyphae length, total Al in the plants, exchangeable Al in the soil and soil pH by comparison at soil pH 3.5, 4.5 and 6.0. Plant mung bean (Phaseolus radiatus L.) and crotalaria (Crotalaria mucronata Desv.) were grown with and without VA mycorrhizal fungi in pots with red soil. Ten VA mycorrhizal fungi strains were tested, including Glomus epigaeum (No. 90001), Glomus caledonium (No. 90036), Glomus mosseae (No. 90107), Acaulospora spp. (No. 34), Scutellospora heterogama (No. 36), Scutellospora calospora (No. 37), Glomus manihotis (No. 38), Gigaspora spp. (No. 47), Glomus manihotis (No. 49), and Acaulospora spp. (No. 53). Being the most tolerant to acidity, strain 34 and strain 38 showed quicker and higher-rated colonization without lagging, three to four times more in number of nodules, two to four times more in plant dry weight, 30% to 60% more in hyphae length, lower soil exchangeable Al, and higher soil pH than without VA mycorrhizal fungi (CK). Other strains also could improve plant growth and enhance plant tolerance to acidity, but their effects were not marked. This indicated that VA mycorrhizal fungi differed in the tolerance to soil acidity and so did their inoculation effects. In the experiment, acidic soil could be remedied by inoculation of promising VA mycorrhizal fungi tolerant of acidity.

Surface Acidity of Amorphous Aluminum Hydroxide

The surface acidity of synthetic amorphous AI hydroxide was determined by acid/base titration with several complementary methods including solution analyses of the reacted solutions and XRD characterization of the reacted solids. The synthetic specimen was characterized to be the amorphous material showing four broad peaks in XRD pattern. XRD analyses of reacted solids after the titration experiments showed that amorphous AI hydroxide rapidly transformed to crystalline bayerite at the alkaline condition （pH〉10）. The solution analyses after and during the titration Ksp=^aAl^3＋/aH^＋^3 ,was 10^10.3. The amount of consumption of added acid or base during the titration experiment was attributed to both the protonation/deprotonation of dissolved AI species and surface hydroxyl group. The surface acidity constants, surface hydroxyl density and specific surface area were estimated by FITEQL 4.0.

Gastric juice acidity in upper gastrointestinal diseases

AIM: To search the independent factors determining gastric juice acidity and to investigate the acidity of gastric juices in various benign and malignant upper gastrointestinal diseases. METHODS: Fasting gastric juice acidity of 165 healthysubjects and 346 patients with esophageal ulcer (n = 21), gastric ulcer (n = 136), duodenal ulcer (n = 100) or gastric cancer (n = 89) were measured and compared. Additionally, gastric specimens were taken from the antrum and body for rapid urease test and histological examination. RESULTS: Multivariate analysis revealed that bile stain of gastric juice, high acute inflammatory score of the corpus, and atrophy of the corpus were independent risk factors for the development of gastric hypoacidity with odds ratios of 3.1 (95% CI: 1.3-7.3), 3.1 (95% CI: 1.2-7.9) and 3.5 (95% CI: 1.3-9.2). Esophageal ulcer and duodenal ulcer patients had a lower pH level (1.9 and 2.1 vs 2.9, both P < 0.05) of gastric juices than healthy subjects. In contrast, gastric ulcer and gastric cancer patients had a higher pH level (3.4 and 6.6 vs 2.9, both P < 0.001) than healthy controls. Hypoacidity existed in 22%, 5%, 29%, 5% and 88% of healthy subjects, esophageal ulcer, gastric ulcer, duodenal ulcer and gastric cancer patients, respectively. CONCLUSION: Bile reflux, atrophy and dense neutrophil infiltrate of the corpus are three independent factors determining the acidity of gastric juice.

Should peri-gastrectomy gastric acidity be our focus among gastric cancer patients?

AIM: To investigate the necessity and correctness of acid suppression pre- and post-gastrectomy among gastric carcinoma (GC) patients.

Alleviation of Soil Acidity and Aluminium Phytotoxicityin Acid Soils by Using Alkaline-Stabilized Biosolids

A pot experiment was catried out to study alleviation of soil acidity and Al toxicity by applying analkaline-stabilised sewage sludge product (biosolids) to an acid clay sandy loam (pH 5.7) and a strongly acidsandy loam (pH 4.5). Barley (Hondeum vulgare L. cv. Forrester) was used as a test crop and was grownin the sewage sludge-amended (33.5 t sludge DM ha-1) and unamended soils. The results showed that thealka1ine biosloids increased soil pH from 5.7 to 6.9 for the clay sandy loam and from 4.5 to 6.0 for the sandyloam. The sludge product decreased KCl-extractable Al from 0.1 to 0.0 cmol kg-1 for the former soil andfrom 4.0 to 0.1 cmol kg-1 for the latter soil. As a result, barley plants grew much better and grain yieldincreased greatly in the amended treatments compared with the unamended controls. These observationsindicate that alkaline-stabilised biosolids can be used as a liming material for remedying Al phytotoxicity instrongly acid soils by increasing soil pH and lowering Al bioavailability.

Acidity Regimes of Soils Under Different Vegetations in the Changbai Mountains Region

The acidity regimes of representative soils on the north slope of the Changbai Mountains were examined through determinations of PH and pCa of the soil paste as well as in-site determinations. For soils under broad-leaf forest or broad-leaf-Korean pine forest, the pH decreased from the litter to lower layers gradually until it did not change or decreased further slightly. For soils under coniferous forest or Ermans birch forest,there was a minimum in pH at a depth of 3～6 cm where the content of humus was high. The pCa increased gradually from the soil surface downward to a constant value. The lime potential (pH-0.5pCa) showed a similar trend as the PH in its distribution. For a given soil, the measured pH value of the thick paste, ranging from 4.5 to 5.5, was lower by about 0.5 units than the value determined by the conventional method with a water to soil ratio of 5:1. The PH determined in site was even lower. It was found that there was a fairly close relationship between soil acidity and the type of vegetation. The pH showed a trend of decreasing from soils under broad-leaf forest through broad-leaf-conifer mixed forest and coniferous forest to Ermans birch forest, and the pCa showed an opposite trend in variation.

Acidity effects of Hβ zeolite on olefin alkylation of thiophenic sulfur in gasoline

Olefin alkylation of thiophenic sulfur process was carried out in model gasoline, using Hβ zeolites with different Si/Al2 ratios as catalysts. In particular, the influence of acid properties of Hβ zeolites on its catalytic ability for the thiophene alkylation, xylene alkylation and hexene oligomerization was investigated. The results showed that the acidity of the Hβ zeolite was increased with the decrease of Si/Al2 ratio, but its catalytic ability was not always increased. In fact, it reached the maximal catalytic ability at Si/Al2 ratio of 66, and under the reaction conditions of 60 ℃, 1.5 MPa, WHSV 3.0 h^-1 and time on stream 2 h. At the ratio, the conversion of thiophene, xylene, and oligomerized hexene were 96.6%, 2.7% and 2.8%, respectively. An optimal Si/Al2 ratio exists for the catalytic performance of Hβ zeolite. By investigating the coke deposition of the used Hβ zeolite catalysts, it has been found that the optimal Si/Al2 ratio is attributed to the combined effect of the carbocation activation capability and the hydrogen transformation capability of the Hβ zeolite catalyst.

Nature of Soil Acidity in Relation to Properties and Lime Requirement of Some Inceptisols

Some Inceptisols representing the Singla catchment area in Karimgaungedistrict of Assam, India, were studied for lime requirement as influenced by the nature of soilacidity. The electrostatically bonded (EB)-H^+ and EB-Al^(3+) acidities constituted 33 and 67percent of exchangeable acidity while EB-H^+, EB-Al^(3+), exchangeable and pH-dependent aciditiescomprised 6, 14, 20 and 80 percent of total potential acidity. The pH-dependent acidity made a majorcontribution towards the total potential acidity (67%～84%). Grand mean of lime requirementdetermined by the laboratory incubation method and estimated by the methods of New Woodruff,Woodruff and Peech as expressed in MgCaCO_3 ha^(-1) was in the order: Woodruff (15.6) > New Woodruff(14.9) > Peech (5.1) > incubation (5.0). Correlations analysis among different forms of acidity andlime requirement methods with selected soil properties showed that pH in three media, namely water,1 mol L^(-1) KC1 and 0.01 mol L^(-1) CaCl_2, had a significant negative correlation with differentforms of acidity and lime requirement methods. Exchangeable Fe and Al showed significant positivecorrelations with EB-Al^(3+) acidity, exchangeable acidity, pH-dependent acidity and total potentialacidity, and also lime requirement methods. Extractable Al showed positive correlations withdifferent forms of acidity except EB-H^+ and EB-Al^(3+) acidities. The lime requirement by differentmethods depended upon the extractable aluminium. Significant positive correlations existed betweenlime requirements and different forms of acidity of the soils except EB-H^+ acidity and incubationmethod. The nature of soil acidity was mostly pH-dependent. Statistically, the Woodruff method didslightly better than the New Woodruff, incubation and Peech methods at estimating lime requirementand hence the Woodruff procedure may be recommended for routine soil testing because of its speedand simplicity.

Prediction of valid acidity in intact apples with Fourier transform near infrared spectroscopy

To develop nondestructive acidity prediction for intact Fuji apples, the potential of Fourier transform near infrared (FT-NIR) method with fiber optics in interactance mode was investigated. Interactance in the 800 nm to 2619 nm region was measured for intact apples, harvested from early to late maturity stages. Spectral data were analyzed by two multivariate calibra- tion techniques including partial least squares (PLS) and principal component regression (PCR) methods. A total of 120 Fuji apples were tested and 80 of them were used to form a calibration data set. The influences of different data preprocessing and spectra treatments were also quantified. Calibration models based on smoothing spectra were slightly worse than that based on derivative spectra, and the best result was obtained when the segment length was 5 nm and the gap size was 10 points. Depending on data preprocessing and PLS method, the best prediction model yielded correlation coefficient of determination (r2) of 0.759, low root mean square error of prediction (RMSEP) of 0.0677, low root mean square error of calibration (RMSEC) of 0.0562. The results indicated the feasibility of FT-NIR spectral analysis for predicting apple valid acidity in a nondestructive way.

Sorption of a triazol derivative by soils: importance of surface acidity

The sorption of a triazol derivative, 1-(4-chlorophenyl)- 4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)penten-3-ol with a common name of S3307D, on fifteen soils and three H_2O_2-treated soils was investigated. The sorption isotherm for each untreated and treated soil was non-linear, and was best fitted to Freundlich sorption equation. Soils containing high amount of clay content or organic matter or both sorbed much higher amounts of the chemical than soils that had low contents of these soil constituents. H_2O_2-treated soils showed considerable sorptive affinity for S3307D. It was concluded that both organic matter and mineral fraction in natural soils contributed to the sorption of the basic compound. Sorption by the H_2O_2 treated soils increased as suspension pH decreased, but all suspension pHs exceeded the pKa of the compound by more than two units. This implies that organic base protonation can occur on surfaces of soil components, and surface acidity (exchangeable acidity ) is important in sorption process of the organic base rather than suspension pH.